U.S. DEPARTMENT OF THE INTERIOR

BUREAU OF RECLAMATION
EARTH MANUAL

PART 1

Third Edition

Earth Sciences and Research Laboratory

Geotechnical Research

Technical Service Center

Denver, Colorado

1998

U.S. DEPARTMENT OF THE INTERIOR

BUREAU OF RECLAMATION
ii

MISSION STATEMENTS

The mission of the Department of the Interior is to protect

and provide access to our Nation’s natural and cultural

heritage and honor our trust responsibilities to tribes.

The mission of the Bureau of Reclamation is to manage,

develop, and protect water and related resources in an

environmentally and economically sound manner in the

interest of the American public.

Any use of trade names and trademarks in this publication is for descriptive

purposes only and does not constitute endorsement by the Bureau of

Reclamation.

The information contained in this report regarding commercial products or firms

may not be used for advertising or promotional purposes and is not to be

construed as an endorsement of any product or firm by the Bureau of

Reclamation.

United States Government Printing Office

Denver: 1998

For sale by the Superintendent of Documents,

U.S. Government Printing Office

Washington, DC 20402
iii

PREFACE

Paul Knodel, Chief, Geotechnical Services Branch, Division of Research and Laboratory Services, directed the

writing of the Earth Manual, Third Edition, Part 1. Richard Young, Technical Specialist, Geomechanics and

Research Section, authored chapter 1. Amster Howard, Technical Specialist, Field Operations Team, wrote

chapter 3. I drafted chapter 2, along with sections on drilling, excerpted from the Small Dams Manual

originally written by Robert Hatcher, Division of Geology, and on remote sensing, excerpted from the

Engineering Geology Manual. H. Kit Fuller of the U.S. Geological Survey, Reston, Virginia updated the

information on geologic products available from their agency. The Geology Division (Sam Bartlett, Mark

McKeown, and Sandy Kunzer), Construction Division (Pete Aberle), and Embankment Dams Branch (Tom

McDaniels) performed Reclamation technical reviews. These technical reviews were essential in improving the

quality of the product. Robert T. Sirokman was instrumental in obtaining new photographs of construction from

Reclamation Field Offices. Technical editors for this manual were Richard Walters and Lelon A. Lewis. 

Monica A. Rodriguez and Sharon S. Leffel formatted it.

Part 2 contains standard procedures for investigating and testing soil materials for engineering design,

construction, and operation and maintenance of water resources structures. Research and development continue

to produce improvements in the knowledge of geotechnical materials and methods in which those materials are

evaluated. Therefore, readers benefit from the latest technologies.

After the publication of Part 2 in 1990, efforts began immediately to update Part 1 of the manual. We realized

that, with such a broad topic area, we could not afford to go into detail as greatly as we would wish on any one

topic. To help alleviate this, a major change to the previous edition is the addition of referenced documents. We

have strived to provide the reader the best citations to find further information. We have also referenced other

Reclamation documents for more information in the subject areas.

The Bureau of Reclamation has a proud history in the construction of major water resources projects. We have 

recently broadened our mission to become a water resources management agency. This new direction signals a

change from the era of project development. During restructuring in the mid-1990s, the agency witnessed the

retirement of hundreds of engineers, technicians, and inspectors. We hope that this manual will stand to

document the knowledge gained through the efforts of many of these individuals. The third edition is dedicated

to all of those in Reclamation who have participated in these great earthwork endeavors. I know that I, for one,

am eternally grateful to my companions in the Bureau of Reclamation, for I have learned so much about

geotechnical engineering. 

Jeffrey A. Farrar

Earth Sciences Laboratory

Bureau of Reclamation
v

PREFACE TO THE SECOND EDITION

The purposes of the Second Edition remain essentially the same as those which prompted the First Edition, as

described in the latter' s Preface. Constantly changing concepts of soil mechanics&as evidenced by new research

techniques and ideas, innovations in construction methods and equipment, and computer-generated solutions to

previously insurmountable soils-analyses problems&make mandatory this Second Edition. To improve its

readability and provide for the new material, the Manual has increased in size as those familiar with the First

Edition will recognize.

The contributors to the Manual have held important the need for uniformity in terminology, so that all

personnel&field and office alike speak the same language. Much effort has been expended to achieve

consistency of terms in the text and the 39 designations or procedures that comprise the appendix. This may be

noted especially in the material on soil classification, and methods of logging and reporting; and types and

methods of field explorations and investigations, and the tools and equipment required to obtain the desired

information.

Although the Manual is primarily geared to the Reclamation organization, engineers and technicians of other

governmental agencies, foreign governments, and private firms can, with modifications, utilize the information

as a guide to their individual investigations, control of earth construction, and laboratory testing since emphasis

is upon practical applications rather than upon complex theory. Users of the Manual should recognize that

certain recommendations and values are the result of experience and cannot always be mathematically proved,

nor should one attempt to. The Manual has been written as a guide and aid for the construction of a safe and

stable structures with utmost concern for the safety of lives.

New material, not covered in the First Edition, includes material on: stabilized soils (soil-cement and asphaltic

concrete), more complete information on field investigations and testing equipment in both chapter 2 and

designation E-2, an expanded discussion on pipelines, and a newly developed designation, E-39, titled,

"Investigations for Rock Sources for Riprap," which describes investigative and reporting procedures. In

addition to the conversion factors in the First Edition, conversion curves are included to facilitate the increased

utilization of metric units.

Major revisions center on designation E-16, which has been rewritten and retitled, "Measurement of Capillary

Pressures in Soils," and designation E-17, "Triaxial Shear of Soils," which has been rewritten to conform to

advanced developments in the procedure. Introduced in E-17 is the "Triaxial Shear Test with Zero Lateral

Strain" referred to in modern soil mechanics texts as the K0-test, which now can easily be performed through the

use of the electronic computer.

Since the "Rapid Compaction Control" method, designation E-25, is being used extensively in 35 foreign

countries as well as the United States, reorientation of the text material has been made for presenting the material

in a manner more readily adaptable to both field and office use. More recently (1970), Australia has been

granted permission by the Commissioner, Bureau of Reclamation, to incorporate the "Rapid Compaction

Control" method in the Australian standards, "Testing Soils for Engineering Purposes." Designation E-12 has

similarly been reoriented for ease in performing the relative density test in cohesionless soils.

Designations E-27 through E-35 covering "Instrument Installations" have been revised and updated to reflect

changes in equipment and materials, techniques in installation procedures, and to clarify some of the methods of

reading and reporting of data. To be commended are those dedicated field personnel who recognize

inconsistencies or problems in the field related to "instruments" and who so often resolve the problems

on-the-job. Reflected in these designations are many of their recommendations which have been offered

unselfishly.
vi

While environmental and ecological problems are major concerns of the Bureau of Reclamation, space and time

limitations cause exclusion of discussion of views and policies regarding these highly important design

considerations. It still remains the responsibility of each planner, investigator, designer, and constructor to

consider these problems in his work.

There are occasional references to proprietary materials or products in this publication. These must not be

construed as an endorsement since the Bureau cannot endorse proprietary products or processes of manufacturers

or the services of commercial firms for advertising, publicity, sales, or other purposes.

Indicative of the monumental task involved in the preparation of this Second Edition is that some 90

persons&engineers, technicians, and those of other disciplines&from the Bureau of Reclamation at its

Engineering and Research Center, Denver, Colo., constructively contributed to the content in some measure. 

The efforts of these people, some of whom are internationally acknowledged, are greatly appreciated.

Special recognition is given to H. J. Gibbs, Chief, Earth Sciences Branch, Division of General Research, and F.

J. Davis, Supervisory Civil Engineer Hydraulic Structures Branch Division of Design and Construction, for

authoring much of the technical material, for their technical advice, and for their overall guidance. In addition,

recognition is made of engineers C. W. Jones, W. Ellis, R. R. Ledzian, G. DeGroot, and P. C. Knodel, and

technician R. C. Hatcher, all of the Division of General Research, and engineer W. W. Daehn of the Division of

Design and Construction for their major contributions. Because illustrations are invaluable to a publication,

recognition must be made to R. E. Glasco and Mrs. H. Fowler for their patience, guidance, and help in

obtaining illustrations of the highest quality.

This Second Edition was edited and coordinated, and supplemental technical information and illustrations

provided by H. E. Kisselman, general engineer, Technical Services and Publications Branch.
1

Since the tentative edition, 28,000 copies of the first formal edition and its revised reprint (first printing) have been printed and distributed.

vii

PREFACE TO THE FIRST EDITION

The need for an up-to-date formal edition of the Bureau of Reclamation' s Earth Manual became evidenced by the

many printings of the June 1951 tentative edition. More than 6,000 copies of that edition were distributed, and a

worldwide demand for the publication continues.1

The tentative edition was a combination and revision of three early manuals; namely, the Earth Materials

Laboratory Test Procedures, the Field Manual for Rolled Earth Dams, and the Earth Materials Investigation

Manual. In the present formal edition, the Earth Manual has been completely rewritten and contains much

material not covered in the earlier edition.

The manual provides current technical information on the field and laboratory investigations and construction

control of soils used as foundations and materials for dams, canals, and many other types of structures built for

Reclamation projects in the United States of America. It contains both standardized procedures that have been

found desirable for securing uniform results throughout the Bureau, and general guidelines intended to assist but

not to substitute for engineering judgment.

Chapter I describes the Unified Soil Classification System developed jointly by the Bureau of Reclamation and

the Corps of Engineers, Department of the Army, from the system proposed by Professor A. Casagrande of

Harvard University, and discusses the various properties of soils relating to engineering uses. Investigations of

soils are covered in chapter II which describes the various stages of investigation corresponding to the stages of

development of the Bureau projects, and gives technical information necessary for planning and executing

explorations and for presenting the results.

Chapter III presents information on the control of construction from the soils standpoint, for both foundation

treatment and compaction control of fills. In addition to a general treatment of the subject applicable to all types

of earthwork, separate sections are devoted to problems of rolled earth dams, canals, and miscellaneous

construction features. For each of these, information on design features and usual specifications provisions are

given to provide control personnel with a background to assist in implementing the recommended control

techniques.

The appendix contains detailed procedures for sampling, classification, and field and laboratory testing of soils. 

Instructions for installing and obtaining information from instruments that measure pore-water pressures and

displacements within and adjacent to earth embankments are also included. A tabulation of conversion factors

commonly used in earth construction is included at the end of the appendix.

The appendix contains laboratory test procedures which are used in both the project laboratories and the central

Bureau laboratory, and some of the more complex test procedures which are performed only in the central

laboratory. The first group is presented for use by all Bureau laboratories, so that uniformity of test results will

be obtained. The second group is presented for the purpose of recording the test procedures used in the central

Bureau laboratory, so that the results of these tests, which are often contained in published reports, can be

properly understood and interpreted.

Although the basic test procedures are standardized, it is emphasized that soil testing does not lend itself to strict

standardization as normally applied to such construction materials as concrete, steel, and asphalt. Tests on soils

must be carried out in such a way that natural conditions and operational conditions are fully accounted for

during the test. In a simple test as for gradation determinations, the standard procedure may not take into

account particle breakdown that may occur during excavation and compaction. Therefore, the test procedure 
viii

may require changes to provide "as constructed" gradation data. The compaction and other properties of some

soils may be changed by drying and rewetting. In such cases, the field construction conditions must be taken

into account during the test.

When variations from standard procedures are required, the variations must be described when reporting results,

so that proper interpretations can be made. The exact procedures to be used for consolidation and shear tests

normally require considerable judgment to assure that natural and operational prototype conditions are being

duplicated as closely as possible. For this reason, the basic procedures presented for these two tests are merely

guides and the details of actual test procedures used are covered in individual reports.

There may be instances in which the procedures and instructions in the Earth Manual are at variance with

contract specifications requirements. In such cases, it should be understood that the specifications take

precedence. It is also pointed out that each employee of the Bureau is accountable to his immediate supervisor

and should request advice concerning any doubtful procedure.

Unless otherwise noted, the terms and symbols used in the Earth Manual conform to those given in ASTM

Designation D-653-58T, "Tentative Definitions of Terms and Symbols Relating to Soil Mechanics," ASTM

Standards 1958, part 4, page 121 1. These terms are also given in Paper 1826, "Glossary of Terms and

Definitions in Soil Mechanics," Journal of the Soil Mechanics and Foundations Divisions, ASCE, October 1958.

Some of the exploratory and test procedures in chapter 11 and in certain of the designations which are applicable

to the investigations, design, and construction of small earth structures have also been included in the publication

"Design of Small Dams," recently published (1960).

The Earth Manual represents the joint efforts of many engineers and technicians over a period of many years

covering the preparation of the tentative edition, its three predecessor publications, and this first formal edition. 

The present edition (including the revised reprint) was prepared by engineers in the Earth Dams Section, Dams

Branch, Division of Design, and the Soils Engineering Branch, Division of Research, in Denver, Colo., under

the direction of Chief Engineer B. P. Bellport and his predecessors.

Major writing was performed by F. C. Walker, J. W. Hilf, and W. W. Daehn of the Earth Dams Section; and

W. G. Holtz and A. A. Wagner of the Soils Engineering Branch. Contributing writers were F. J. Davis, E. E.

Esmiol, H. J. Gibbs, and C. W. Jones. The draft was reviewed and helpful suggestions submitted by geologists

and engineers in various other branches of the organization. Principal among these were W. H. Irwin, A. F.

Johnson, H. G. Curtis (deceased), and C. E. McClaren. The contributions of these individuals, as well as those

of the many other engineers and technicians who contributed in various ways to the publication, are gratefully

acknowledged. The draft was edited and coordinated by J. W. Hilf, and final review and preparation for

publication was performed by E. H. Larson, Head, Manuals and Technical Records Section, Technical and

Foreign Services Branch.

There are many references throughout the text to the Assistant Commissioner and Chief Engineer and the Office

of Assistant Commissioner and Chief Engineer. For expediency these references were not changed in the reprint

to agree with recent organization changes (February 1963), and they should be interpreted as meaning Chief

Engineer and Office of Chief Engineer, respectively. References to the Commissioner' s Office, Denver, should

also be interpreted as meaning the Office of Chief Engineer.
ix

CONTENTS

Page

Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii

Preface to the Second Edition ................................................. v

Preface to the First Edition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii

Chapter 1 Properties of Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

A. Identification and Classification .......................................... 1

1-1. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1-2. Unified Soil Classification System ..................................... 1

1-3. Current Classification System ........................................ 1

1-4. Basis of Unified Soil Classification System ................................ 3

1-5. Gravel, Sand, Silt, and Clay ......................................... 3

a. Gravel and Sand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

b. Silt and Clay (Fines) ............................................. 4

c. Organic Matter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

1-6. Cobbles and Boulders ............................................. 4

1-7. Shale, Crushed Rock, and Slag . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

1-8. Soil Composition ................................................ 5

B. Index Properties of Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

1-9. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

1-10. Terms and Units of Measure ........................................ 7

a. Mass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

b. Density . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

c. Weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

d. Unit Weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

e. Percentage and Decimal Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

1-11. Gradation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

1-12. Atterberg Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

1-13. Porosity and Void Ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

1-14. Specific Gravity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

1-15. Moisture Content . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

a. Optimum Moisture Content . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

b. Absorbed Moisture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

1-16. Density and Unit Weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

a. In Situ Unit Weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

b. Wet Unit Weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

c. Dry Unit Weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

d. Laboratory Maximum Dry Unit Weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

e. Relative Density . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

f. Compacted-Fill Unit Weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

1-17. Penetration Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

a. Soil Plasticity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

b. Penetration Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

1-18. Unconfined Compressive Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

1-19. Soluble Solids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

C. Engineering Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

1-20. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
x

Contents

Page

Chapter 1 Properties of Soils (continued)

C. Engineering Properties (continued)

1-21. Shear Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

a. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

b. In Situ Shear Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

c. Direct Shear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

d. Triaxial Shear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

e. Pore-Water Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

f. Capillary Stress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

g. Sliding Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

h. Residual Shear Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

1-22. Volume Change . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

a. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

b. Control of Compressibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

c. Pressure-Compression Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

d. Pressure-Expansion Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

1-23. Permeability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

a. Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

b. Ranges of Permeability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

c. Control of Permeability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

d. Determination of Coefficient of Permeability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

1-24. Engineering Characteristics of Soil Groups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

a. Engineering Use Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

1-25. Changes in Soil Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

1-26. Workability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

1-27. Frost Action . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

1-28. Erodibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

1-29. Dispersive Clay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

1-30. Dynamic Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

Chapter 2 Investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

A. Principles of Investigations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

2-1. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

a. Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

b. Classification of Structure Foundations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

2-2. Sources of Map and Photo Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

a. U.S. Department of Agriculture (Aerial Photography) . . . . . . . . . . . . . . . . . . . . . . . 64

b. The U.S. Geological Survey (USGS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

c. USGS Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

d. USGS Technical Reports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

e. USGS Publications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

f. USGS Software, Data, and Related Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

g. USGS Remote Sensing Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

h. Access to USGS Data Bases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

i. Sources of USGS Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
xi

Contents

Page

Chapter 2 Investigation (continued)

A. Principles of Investigations (continued)

2-2. Sources of Map and Photo Information (continued)

j. USGS Topographic Maps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

k. USGS Geologic Maps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

l. Agricultural Soil Maps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

2-3. Remote Sensing Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

a. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

b. Nonphotographic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

1. Scanners . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

2. Video . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

c. Resolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

1. Spatial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

2. Spectral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

d. Photography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

1. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

2. Panchromatic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

3. Natural Color . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

4. Multispectral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

5. Color Infrared . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

e. Thermal Infrared Imagery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

f. Multispectral Scanner Imagery (MSS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

1. Airborne MSS Imagery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

2. Satellite MSS Imagery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

g. Radar Imagery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

h. Applications to Geotechnical Engineering and Geology . . . . . . . . . . . . . . . . . . . . . . 76

i. Availability of Imagery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

j. Mission Planning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

2-4. Site Investigations and Land Form Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

a. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

b. Alluvial Deposits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

1. Stream Channel Deposits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

2. Flood Plain Deposits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

3. Terrace Deposits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

4. Alluvial Fan Deposits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

c. Slope Wash or Colluvial Deposits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

d. Lacustrine Deposits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

e. Glacial Deposits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

1. Tills or Glacial Deposits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

2. Outwash or Glaciofluvial Deposits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

f. Eollan Deposits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

1. Loess . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

2. Dune Deposits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

g. Residual Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
xii

Contents

Page

Chapter 2 Investigation (continued)

A. Principles of Investigations (continued)

2-5. Subsurface Investigations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

a. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

b. Point Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

c. Line Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

d. Damsites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

e. Tunnels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

f. Borrow Areas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

g. Selection of Samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

h. Field Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94

2-6. Investigations for Construction Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95

a. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95

b. Impervious Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95

1. Canal Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95

2. Dam Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96

c. Pervious Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96

1. Concrete Aggregates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96

2. Filters and Drains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96

3. Bedding Under Riprap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

4. Drainage Blankets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

5. Road Surfacing and Bass Course . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

d. Riprap and Rockfill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

1. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

2. Riprap for Earth Dams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

3. Riprap for Stilling Basins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

4. Riprap for Canals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

5. Rockfill Blankets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

6. Investigative Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

2-7. Materials for Stabilized and Modified Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

a. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

b. Compacted Soil-Cement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

c. Soil-Cement Slurry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102

d. Modified Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102

B. Exploratory Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102

2-8. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102

2-9. Accessible Exploratory Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

a. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

b. Test Pits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104

c. Large-Diameter Borings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

d. Trenches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

e. Tunnels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

2-10. Nonaccessible Exploratory Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

a. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

b. Auger Borings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108

c. Mechanical Auger Drilling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
xiii

Contents

Page

Chapter 2 Investigation (continued)

B. Exploratory Methods (continued)

2-10. Nonaccessible Exploratory Methods (continued)

c. Mechanical Auger Drilling (continued)

1. Continuous-Flight Augers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110

2. Hollow-Stem Augers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110

3. Helical, Disk, and Bucket Augers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112

4. Bucket Drills . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112

5. Enclosed Augers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

d. Nonsampling Borings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

2-11. Rotary Drilling Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

a. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

b. Rotary Drills . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125

1. Rotary-Table Drills . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125

2. Top-Head Drive Drills . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125

3. Hollow-Spindle Drills . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127

4. Fluted Kelly Drills . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129

5. Reverse-Circulation Drills . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129

6. Top-Head Drive With Percussion Casing Hammer Drills . . . . . . . . . . . . . . . . . . . 132

7. Horizontal Rotary Drills . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134

c. Core Drilling for Tunnel Alignment Geology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135

d. Slope Inclinometer Casing Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135

e. Piezometer Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135

f. Settlement-Plate Monitoring Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135

g. Churn/Cable-Tool Drills . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136

h. Rock Core Drilling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136

1. Conventional and Wire-line Core Drills . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138

2. Shot or Calyx Drills . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140

i. Planning a Drilling Program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140

2-12. Procedures for Drilling in Embankment Dams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140

a. Conditions Conducive to Hydraulic Fracturing . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140

b. Recommended Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140

c. Acceptable Drilling Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141

C. Sampling and Testing Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141

2-13. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141

2-14. Hand Sampling Methods for Obtaining Disturbed Samples . . . . . . . . . . . . . . . . . . . . . 142

a. Accessible Test Pits, Trenches, and Large-Diameter Borings . . . . . . . . . . . . . . . . . . . 142

b. Stockpiles and Windrows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142

c. Hand Auger Borings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143

2-15. Mechanical Sampling Methods for Obtaining Disturbed Samples . . . . . . . . . . . . . . . . . 143

a. Power Auger Drills . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143

b. Reverse-Circulation Drills . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143

c. Protecting and Preparing Disturbed Samples for Shipping . . . . . . . . . . . . . . . . . . . . . 143

2-16. Hand-Sampling Methods for Obtaining Undisturbed Samples . . . . . . . . . . . . . . . . . . . 144

a. Undisturbed Hand-Sampling Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144

b. Protecting and Preparing Hand-Cut Undisturbed Samples for Shipping . . . . . . . . . . . . 146
xiv

Contents

Page

Chapter 2 Investigation (continued)

C. Sampling and Testing Methods (continued)

2-17. Mechanical Sampling Methods for Obtaining Undisturbed Samples . . . . . . . . . . . . . . . 146

a. Saturated Cohesionless Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146

b. Soft to Moderately Firm Cohesive Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149

1. Thinwall Push Samplers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149

2. Hollow-Stem Auger Samplers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151

c. Medium to Hard Soils and Shales . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153

1. Pitcher Sampler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153

2. Denison Sampler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153

3. Large-Diameter Hi-Recovery Core Barrels . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156

d. Unsaturated Water Sensitive Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156

2-18. Casing Advancer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157

2-19. Rock Sampling Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157

2-20. Geophysical Exploration Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161

2-21. Field Testing Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164

a. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164

b. Field Permeability Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164

c. In-Place Density Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164

d. Penetration Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168

1. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168

2. Penetration Resistance and Sampling of Soils . . . . . . . . . . . . . . . . . . . . . . . . . . 168

e. Becker Penetration Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170

1. Origin of Becker Penetration Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170

2. Open-Ended Becker Drilling Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170

3. Close-Ended Becker Drilling Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171

4. Interpretation of BPT and SPT Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171

f. Cone Penetration Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171

g. Dynamic Penetrometers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173

h. In Situ Strength and Modulus Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174

i. Field Vane Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174

j. Pressuremeter Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174

k. Soil and Rock Borehole Shear Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175

l. Flat Plate Dilatometer Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176

m. Pocket Vane Shear Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178

n. The Point-Load Strength Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178

o. Portable Direct Shear Rock Testing Device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181

p. Large-Scale, In-Place, Direct Shear Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182

q. Uniaxial and Radial Jacking Tests in Rock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182

D. Recording and Reporting of Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183

2-22. Maps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183

a. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183

b. Site Geologic Mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187

1. General Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187

2. Documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187
xv

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Page

Chapter 2 Investigation (continued)

D. Recording and Reporting of Data (continued)

2-23. Logging of Exploratory Holes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188

a. Location of Holes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188

b. Identification of Holes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189

c. Log Forms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189

1. Geologic Logs of Drill Holes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190

2. Log of Test Pit or Auger Hole . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194

2-24. Subsurface Sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201

2-25. Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201

2-26. Reports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202

a. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202

b. Foundations and Earthwork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203

c. Construction Materials Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203

Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206

Chapter 3 Control of Earth Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211

A. Principles of Construction Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211

3-1. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211

3-2. Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212

3-3. Field Laboratory Facilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212

3-4. Laboratory Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213

3-5. Reports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216

B. Earthwork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218

3-6. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218

3-7. Embankment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218

a. Types of Embankment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218

b. Dumped Fill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218

c. Selected Fill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218

d. Equipment-Compacted Embankment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219

e. Rolled Earthfill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219

f. Vibratory-Compacted Embankment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220

g. Blended Earthfill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220

h. Modified Soil Fill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221

i. Hydraulic Fill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221

3-8. Linings and Blankets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223

a. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223

b. Rock Blankets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223

c. Sand and Gravel Blankets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223

d. Impervious Blankets and Linings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224

e. Topsoil Blankets or Zones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224

3-9. Backfill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225

a. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225

b. Compacted Backfill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225

3-10. Excavation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226

C. Foundations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226

3-11. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226
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Page

Chapter 3 Control of Earth Construction (continued)

C. Foundations (continued)

3-12. Bearing Capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226

3-13. Stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227

3-14. Settlement and Uplift . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230

3-15. Deterioration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230

3-16. Permeability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230

3-17. Unsuitable Foundation Soil Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232

a. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232

b. Topsoil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232

c. Swamp Deposits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232

d. Silt and Sand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233

e. Talus and Spoil Piles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234

f. Highly Plastic Clays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234

g. Soft or Saturated Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234

3-18. Foundation Improvement Technology and Dam Rehabilitations . . . . . . . . . . . . . . . . . . 235

a. Slurry Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235

b. Fill Loading With Sand or Wick Drains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235

c. Dynamic Compaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236

d. Vibratory Densification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239

1. Vibro-Compaction/Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239

2. Vibrating Probes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239

3. Blasting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240

e. Grouting and Soil Mixing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240

1. Compaction Grouting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240

2. Jet Grouting and Deep Soil Mixing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241

D. Embankment Dams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242

3-19. Foundation Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242

a. Design Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242

b. Specifications Provisions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245

c. Control Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247

3-20. Compacted Earthfill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247

a. Design Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247

b. Specifications Provisions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250

c. Control Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251

3-21. Compacted Pervious Fill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 258

a. Design Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 258

b. Specifications Provisions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259

c. Control Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261

3-22. Semipervious Fill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261

3-23. Rockfill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262

a. Sound Rock in Rockfill Dams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262

1. Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262

2. Placement Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262

3. Compaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262

b. Unsound Rock in Rockfill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263
xvii

Contents

Page

Chapter 3 Control of Earth Construction (continued)

D. Embankment Dams (continued)

3-24. Riprap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263

3-25. Miscellaneous Fills . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264

3-26. Instrument Installations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264

a. Instruments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264

b. Installation of Embankment Dam Instrumentation . . . . . . . . . . . . . . . . . . . . . . . . . . 264

c. Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265

d. Record Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265

3-27. Records and Reports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265

a. Daily Reports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265

b. Periodic Progress Reports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266

c. Final Embankment Construction Reports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267

3-28. Control Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269

E. Canals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273

3-29. Design Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273

3-30. Specifications Provisions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275

a. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275

b. Subgrades and Foundations for Embankments and Compacted Earth Lining . . . . . . . . . 276

c. Earth Embankments and Linings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276

d. Riprap, Protective Blankets, Gravel Fills, and Gravel Subbase . . . . . . . . . . . . . . . . . . 278

3-31. Control Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281

a. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281

b. Subgrades and Embankment Foundations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281

c. Earth Embankments and Linings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283

F. Pipelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285

3-32. Design Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285

3-33. Specifications Provisions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285

3-34. Construction Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 288

3-35. Construction Control Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289

3-36. Soil-Cement Slurry Pipe Bedding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289

G. Miscellaneous Construction Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292

3-37. Highways and Railroads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292

a. Design Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292

b. Earthwork Specifications Provisions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292

c. Control Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293

3-38. Miscellaneous Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294

a. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294

b. Structure Foundations on Soil or Rock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294

c. Pile and Drilled Shaft Foundations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296

d. Backfill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297

e. Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 298

H. Stabilized Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299

3-39. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299

3-40. Compacted Soil-Cement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299

a. Design Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299
xviii

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Page

Chapter 3 Control of Earth Construction (continued)

H. Stabilized Soils (continued)

3-40. Compacted Soil-Cement (continued)

b. Construction Provisions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 301

c. Control Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302

d. Control Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 305

3-41. Compacted Soil-Lime . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306

a. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306

b. Adding Lime to Highly Plastic Clay Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 307

c. Adding Lime to Dispersive Clay Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308

d. Construction Procedures for Lime . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308

Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 310

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313

TABLES

Table Page

1-1 Relationship between consistency, unconfined compressive strength, and 

 penetration resistance, N . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

1-2 Relation of soil index properties to expansion potential of high-plasticity clay soils . . . . . . . . . 46

1-3 Average engineering properties of compacted soils from the 17 Western United States . . . . . . . 50

1-4 Engineering use chart for compacted soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

2-1 Diamond Core Drill Manufacturers Association nomenclature for bits and drill rods . . . . . . . . 118

2-2 Diamond Core Drill Manufacturers Association drill rod specifications . . . . . . . . . . . . . . . . 119

2-3 Wire-line and American Petroleum Institute drill rods . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120

2-4 Diamond Core Drill Manufacturers Association casing specifications . . . . . . . . . . . . . . . . . . 121

2-5 Approximated core and hole diameters for core barrels . . . . . . . . . . . . . . . . . . . . . . . . . . . 122

2-6 Tools and methods for subsurface investigations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165

2-7 Geophysical methods and techniques for logging boreholes . . . . . . . . . . . . . . . . . . . . . . . . 166

3-1 General suitability of soils for compacted backfill by saturation and internal vibration . . . . . . . 225

3-2 Criteria for control of compacted dam embankments . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273

3-3 Materials and placing requirements for various fills used in canals . . . . . . . . . . . . . . . . . . . 280

FIGURES

Figure Page

1-1 Typical soil exploration log . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

1-2 Clay kaolinite particles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

1-3 Halloysite particles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

1-4 Gradation plot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
xix

Contents

Figures

Figure Page

1-5 Consistency limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

1-6 Phases of a soil-water system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

1-7 Plasticity chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

1-8 Typical relationships between the liquid limit and the plasticity index for various soils . . . . . . . 14

1-9 Relationship between air, water, and solids in a soil mass . . . . . . . . . . . . . . . . . . . . . . . . . 15

1-10 Gradation, penetration, and compaction curves for various soils . . . . . . . . . . . . . . . . . . . . . 17

1-11 Effect of compactive effort on the compaction and penetration-resistance curves . . . . . . . . . . . 18

1-12 Typical minimum and maximum dry unit weights for various coarse-grained soils . . . . . . . . . 21

1-13 Maximum and minimum index dry unit weights of typical sand and gravel soils . . . . . . . . . . . 22

1-14 Maximum dry density versus gravel content for compacted soils . . . . . . . . . . . . . . . . . . . . . 23

1-15 Criterion for predicting relative density of sand from the penetration resistance test . . . . . . . . . 25

1-16 Unconfined compressive strength versus penetration resistance, N, for various soils . . . . . . . . 26

1-17 Effect of relative density on the coefficient of friction, tan 1, for coarse-grained soils . . . . . . . 29

1-18 Results of a consolidated-undrained (CIU) triaxial shear test on lean clay with and without 

 considering pore pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

1-19 Peak and residual shear strength and resultant angles of internal friction . . . . . . . . . . . . . . . . 32

1-20 Compression characteristics of various compacted embankment soils based on field 

 measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

1-21 Void ratio-pressure curve, compression index, and preconsolidation pressure . . . . . . . . . . . . 36

1-22 A 34-foot cut on 1/2:1 slope in loess formation&Franklin Canal, Nebraska . . . . . . . . . . . . . . 37

1-23 Effect of loading and wetting high and low unit weight loess soil foundations . . . . . . . . . . . . . 38

1-24 Criterion for treatment of relatively dry fine-grained foundations . . . . . . . . . . . . . . . . . . . . 39

1-25 Assessing collapse potential of various soils using dry density and liquid limit . . . . . . . . . . . . 40

1-26 Compressibility characteristics of a fine sand in relation to placement relative density . . . . . . . 42

1-27 Pressure-expansion curves for two typical expansive clays . . . . . . . . . . . . . . . . . . . . . . . . . 43

1-28 Typical expansive clay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

1-29 Slope failure and bottom heaving of Friant-Kern Canal, California . . . . . . . . . . . . . . . . . . . 45

1-30 Heaving of canal bottom (about 300 mm at center), Mohawk Canal, Arizona . . . . . . . . . . . . 45

1-31 Effect of lime on shrinkage limit, plastic limit, and liquid limit . . . . . . . . . . . . . . . . . . . . . . 47

1-32 Permeability ranges for soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

1-33 Relationship of permeability to gravel content for specimens of various relative densities . . . . . 49

1-34 Frost susceptibility classification by percentage of mass finer than 0.02 mm . . . . . . . . . . . . . 55

1-35 Limiting tractive forces recommended for canals and observed in rivers . . . . . . . . . . . . . . . . 56

2-1 Soil triangle of the basic soil texture classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

2-2 Rock strata illustrating folding in sedimentary rocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

2-3 Sinkhole plain indicating deep plastic soils over cavernous limestone, developed in 

 humid climate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

2-4 Aerial view and topography of stream deposit showing river alluvium and three levels of 

 gravel terraces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78

2-5 Aerial view and topography of an alluvial fan, a potential source of sand and gravel . . . . . . . . 79

2-6 Aerial view and topography of terminal moraine of continental glaciation . . . . . . . . . . . . . . . 82

2-7 Aerial view and topography of loess identified by smooth silt ridges; usually parallel, 

 right-angle drainage patterns; and steep-sided, flat-bottomed gullies and streams . . . . . . . . . 83
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Contents

Figures

Figure Page

2-8 Photomicrograph showing typical open structure of silty loess . . . . . . . . . . . . . . . . . . . . . . 84

2-9 Depth of preliminary exploratory holes for point structures . . . . . . . . . . . . . . . . . . . . . . . . 87

2-10 Soil profile at a pumping plant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

2-11 Depth of preliminary exploratory holes for canal, road, and pipeline alignments . . . . . . . . . . . 89

2-12 Example of a geologic profile along the centerline of a pipeline . . . . . . . . . . . . . . . . . . . . . 90

2-13 Geologic section of a damsite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91

2-14 Exploration for embankment materials&borrow area location map and typical cross sections . . . 93

2-15 Results of a major blast in a riprap quarry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

2-16 Blasting a rock ledge at the riprap source for Stampede Dam, California . . . . . . . . . . . . . . . 99

2-17 Talus slope of igneous rock proposed for riprap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

2-18 Samplers used for undisturbed soil sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104

2-19 Shallow test trench excavated by bulldozer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

2-20 Example of tunnel mapping from machine-excavated tunnel . . . . . . . . . . . . . . . . . . . . . . . . 107

2-21 Types of hand augers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

2-22 Continuous-flight auger mounted on an all-terrain carrier . . . . . . . . . . . . . . . . . . . . . . . . . 111

2-23 Hollow-stem auger with center plug . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113

2-24 Illustration of the helical, disc, and barrel types of machine-driven augers showing 

 basic differences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114

2-25 Bucket drill rig in drilling position with a 24-foot triple Kelly and 36-inch bucket . . . . . . . . . . 115

2-26 Enclosed auger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

2-27 Core drill casing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124

2-28 Photograph of typical rotary drill showing some of the essential equipment for rotary drilling . . 126

2-29 Top-head drive drill with head-in mast for drilling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128

2-30 Fluted Kelly drill setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130

2-31 Dual-wall reverse-circulation method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131

2-32 Casing drivers can be fitted to top-head drive rotary rigs to simultaneously drill and 

 drive casing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133

2-33 Horizontal rotary drill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134

2-34 Typical diamond drilling rig for exploration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137

2-35 Wire-line core barrel operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139

2-36 Auger sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144

2-37 Method for obtaining a hand-cut, undisturbed cylindrical sample . . . . . . . . . . . . . . . . . . . . . 145

2-38 Initial steps to obtain a hand-cut, undisturbed block sample from (A) bottom of test pit or 

 level surface, and from (B) cutbank or side of test pit. . . . . . . . . . . . . . . . . . . . . . . . . . . 147

2-39 Final steps in obtaining a hand-cut, undisturbed block sample . . . . . . . . . . . . . . . . . . . . . . . 148

2-40 Chain saw equipped with carbide-tipped blade being used to cut block sample . . . . . . . . . . . . 149

2-41 Thinwall fixed-piston sampler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150

2-42 Overshot wire-line a) and rod type b) continuous sampling system . . . . . . . . . . . . . . . . . . . . 152

2-43 Pitcher sampler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154

2-44 Denison sampler and core barrel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155

2-45 Relationship of inner-barrel protrusion using different-length, Denison-sampler cutting 

 bits for drilling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156
xxi

Contents

Figures

Figure Page

2-46 Double-tube swivel-type core barrels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158

2-47 Wire-line packer system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160

2-48 Use of a cardboard PVC half-round and plastic wrap to prevent disturbance and drying 

 out of shear zone, special samples, or fracture zones . . . . . . . . . . . . . . . . . . . . . . . . . . . 162

2-49 Arrangement of cores in a core box to ensure proper identification of samples . . . . . . . . . . . . 163

2-50 Rock rippability as related to seismic P-wave velocities . . . . . . . . . . . . . . . . . . . . . . . . . . . 167

2-51 Standard drilling equipment used to perform penetration tests . . . . . . . . . . . . . . . . . . . . . . . 169

2-52 Sampler requirements for penetration resistance testing . . . . . . . . . . . . . . . . . . . . . . . . . . . 170

2-53 Example of electronic cone penetrometer data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172

2-54 Electronic cone penetrometer testing vehicle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173

2-55 Menard pressuremeter equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175

2-56 Self-boring pressuremeters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176

2-57 Borehole shear device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177

2-58 Dilatometer test equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177

2-59 Torvane (pocket-vane shear meter) equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179

2-60 Point-load strength testing machines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180

2-61 Point-load strength testing variations (a) diametral test, (b) axial test, (c) irregular lump test . . . 181

2-62 Relationship between point-load strength index and uniaxial-compressive strength . . . . . . . . . 182

2-63 Sketch of portable direct shear device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183

2-64 Shear and sliding friction testing equipment, Auburn damsite . . . . . . . . . . . . . . . . . . . . . . . 184

2-65 Uniaxial jacking test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185

2-66 Example geologic log of a drill hole . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192

2-67 Subsurface exploration&penetration resistance and log&example . . . . . . . . . . . . . . . . . . . . 193

2-68 Log of test pit or auger hole&abbreviated soil classification group symbols for soil with 

 cobbles and boulders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195

2-69 Log of test pit or auger hole&in-place conditions and sampling . . . . . . . . . . . . . . . . . . . . . . 197

2-70 Log of test pit or auger hole&combined laboratory and visual classification . . . . . . . . . . . . . . 199

2-71 Log of test pit or auger hole&materials other than natural soils . . . . . . . . . . . . . . . . . . . . . . 200

2-72 Geologic interpretation in test pit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202

2-73 Summary of field and laboratory tests for embankment materials report&impermeable-type 

 materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205

2-74 Summary of field and laboratory test for embankment materials report&permeable-type 

 materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205

3-1 Examples of floor plans for field control laboratories . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214

3-2 Typical field laboratories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215

3-3 A deposit of impervious material which overlies a deposit of pervious material . . . . . . . . . . . 222

3-4 Landslide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228

3-5 Cutoff trench at Davis Dam in Arizona . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228

3-6 Cutoff trench at Twin Buttes Dam in Texas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229

3-7 Typical sinkhole . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231

3-8 Cracking and settling of canal bank in dry, low-density silt . . . . . . . . . . . . . . . . . . . . . . . . 233

3-9 Ponding dry foundation of Trenton Dam in Nebraska . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234
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Contents

Figures

Figure Page

3-10 Schematic drawing showing slurry wall construction methods&backhoe and clamshell 

 excavation and surface backfill method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236

3-11 Slurry wall construction using panel excavation and tremie placement&view of a hydromill and 

 crane with 30-inch (75-cm) x 10 ft (3-m) clamshell&Twin Buttes Dam modification . . . . . . . 237

3-12 Photograph of dynamic compaction showing crane, weight, and impact pattern . . . . . . . . . . . 238

3-13 Schematic drawing of vibro-replacement&backfill can be added by top feed (illustrated)

 or bottom feed methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239

3-14 Schematic drawing of jet grouting process showing construction of columns . . . . . . . . . . . . . 241

3-15 Curtain grouting in right abutment of New Waddell Dam in Arizona . . . . . . . . . . . . . . . . . . 244

3-16 Temporary diversion channel through Bonny Dam, Colorado . . . . . . . . . . . . . . . . . . . . . . . 246

3-17 Foundation preparation for the impervious (zone 1) foundation at Jordanelle Dam, Utah . . . . . 248

3-18 Earthfill (zone 1) compaction by a model 925 C Caterpillar pad foot roller . . . . . . . . . . . . . . 249

3-19 Separation plant at Meeks Cabin Dam in Wyoming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251

3-20 Earthfill operation on impervious zone at Reclamation’s McPhee Dam, Colorado . . . . . . . . . . 252

3-21 A view of McPhee Dam under construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253

3-22 Pad foot roller on a test fill of zone 1 material at New Waddell Dam, Arizona . . . . . . . . . . . . 254

3-23 Average field and laboratory compaction curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255

3-24 A Holland loader excavating a vertical face mixing silt and fine sand deposits for 

 impervious fill at Reclamation’s Calamus Dam, Nebraska . . . . . . . . . . . . . . . . . . . . . . . . 256

3-25 Two model 992C Caterpillar front end loaders loading zone 4 (gravel and cobble fill) from 

 borrow into a model 540 Dart belly dump truck . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257

3-26 Block sample from test pit in zone 1 at McPhee Dam, Colorado . . . . . . . . . . . . . . . . . . . . . 259

3-27 Test pit at the interface of sand filter and gravel drain, Jordanelle Dam, Utah . . . . . . . . . . . . 260

3-28 Form for recording embankment roller data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268

3-29 Typical laboratory tests for the development of shear planes . . . . . . . . . . . . . . . . . . . . . . . 270

3-30 Statistical analysis of test results for density control of fill . . . . . . . . . . . . . . . . . . . . . . . . . 271

3-31 Statistical analysis of test results for moisture control of fill . . . . . . . . . . . . . . . . . . . . . . . . 272

3-32 Typical canal section and compacted earth lining . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276

3-33 Placing and compacting thick earth lining in Welton-Mohawk Canal in Arizona . . . . . . . . . . . 277

3-34 Completed thick earth lining in Welton-Mohawk Canal in Arizona . . . . . . . . . . . . . . . . . . . 278

3-35 Geomembrane being placed over prepared subgrade . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 279

3-36 Placement of a protective earth cover over a geomembrane . . . . . . . . . . . . . . . . . . . . . . . . 279

3-37 Installation requirements of pipe 250-mm in diameter and smaller . . . . . . . . . . . . . . . . . . . . 286

3-38 Typical trench details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287

3-39 Side clearance requirements for flexible pipe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290

3-40 Soil-cement slurry installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291

3-41 Filter gradations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300

3-42 Soil-cement facing at Lubbock Regulating Reservoir in Texas . . . . . . . . . . . . . . . . . . . . . . 301

3-43 Soil-cement facing at Merritt Dam in Nebraska . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302

3-44 Soil stockpile and pugmill for mixing soil-cement at Lubbock Regulating Reservoir in Texas . . 303

3-45 Soil-cement placement at Merritt Dam in Nebraska . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304

3-46 Compaction of soil-cement at Lubbock Regulating Reservoir in Texas . . . . . . . . . . . . . . . . . 305

3-47 Power brooming of surface prior to placement of next lift at Lubbock Regulating Reservoir 

 in Texas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306

3-48 Cement vane feeder and soil feed belt to pugmill at Cheney Dam in Kansas . . . . . . . . . . . . . . 307
1

Chapter 1

PROPERTIES OF SOILS

A. Identification and Classification

1-1. General.&Most soils are a heterogeneous

accumulation of mineral grains that are not cemented

together. However, the term "soil" or "earth" as used in

engineering includes virtually every type of uncemented or

partially cemented inorganic and organic material in the

ground. Only hard rock, which remains firm after

exposure, is wholly excluded. In the design and

construction of foundations and earthwork, the physical and

engineering properties of soils, such as their density,

permeability, shear strength, compressibility, and interaction

with water, are of primary importance.

A standard method is used for identifying and classifying

soils into categories or groups that have distinct engineering

characteristics. This enables a common understanding of

soil behavior just by knowing the classification. Written

exploration records (logs) as shown on figure 1-1 contain

soil classifications and descriptions; they can be used to:

 ̆ Make preliminary estimates.

 ̆ Determine the extent of additional field investigations needed for final design.

 ̆ Plan an economical testing program.

 ̆ Extend test results to additional explorations.

For final design of important structures, visual soil

classification must be supplemented by laboratory tests to

determine soil engineering properties such as permeability,

shear strength, and compressibility under expected field

conditions. Knowledge of soil classification, including

typical engineering properties of various soil groups, is

especially valuable when prospecting for earth materials or

investigating foundations for structures.

1-2. Unified Soil Classification System.&In 1952,

the Bureau of Reclamation (Reclamation) and the U.S.

Army Corps of Engineers, with Professor Arthur

Casagrande of Harvard University, reached agreement on

modifications to his "Airfield Classification System" and

named it: Unified Soil Classification System (USCS) [1]. 1

During World War II, Professor Casagrande developed the

"Airfield Classification System" for categorizing soils based

on engineering properties related to airfield construction [2].

After the war, Reclamation began using the system, which

led to the modifications agreed upon in 1952.

From 1952 to 1986, the system required minor

changes&particularly in presenting information in written

logs. Most changes were documented in Reclamation' s

Earth Manual (1st and 2d eds.) and in written directives,

while some changes were taught in Reclamation training

courses without formal documentation.

In 1984, American Society for Testing and Materials

(ASTM), with encouragement and participation of several

U.S. Government agencies (including Reclamation),

reevaluated the Unified Soil Classification System. New

data and philosophies [3, 4] resulted in revised ASTM

standards, which modified the 1952 system. Reclamation

adopted the new standards with only slight modifications.

While the soil classification system has evolved over many

years, soil classifications and descriptions recorded at any

point in the past must remain valid, because they were based

on information available at that time. Therefore, earlier

logs and past descriptions must not be changed to conform

to current standards.

1-3. Current Classification System.&The Unified

Soil Classification System has been through several

transitions since it was developed. The current version used

by Reclamation went into effect January 1, 1986. The

classification system is described in Reclamation' s testing

procedures USBR 5000 and 5005 [5]. 2

 These procedures

are similar to ASTM D 2487 and D 2488 [6]; the ASTM

standards may be used in place of Reclamation procedures.

The basics of the system may be mastered by studying and

completing exercises in the Geotechnical Branch' s Training

Manuals Nos. 4 and 5 [7, 8]. They are well-prepared, selfinstructing manuals that progress from simple to more

difficult topics. Reclamation has standard formats for

written logs of test pits and auger holes. Uniformity of data

presentation results in consistency and completeness, which

enables efficient review of large numbers of logs. Format

1

 Numbers in brackets refer to bibliography. 2 See bibliography [5] regarding numbered USBR procedures.
EARTH MANUAL

2

Figure 1-1.—Typical soil exploration log.
CHAPTER 1—PROPERTIES OF SOILS

3

guidelines are given in Geotechnical Branch Training

Manual No. 6 [9]. They should be adhered to as closely as

possible; however, every situation cannot be covered.

Therefore, when preparing a log, the object is to present as

complete and as clear a description as possible.

The Soil Classification Handbook [9] also contains charts,

forms, and illustrations useful in soil classification.

1-4. Basis of Unified Soil Classification

System.&The USCS is based on engineering properties of

a soil; it is most appropriate for earthwork construction.

The classification and description requirements are easily

associated with actual soils, and the system is flexible

enough to be adaptable for both field and laboratory use.

The USCS is a method for describing and categorizing a soil

within a group that has distinct engineering properties.

Upon recognizing a USCS symbol of a classification group

or understanding the description, one can immediately

deduce the approximate permeability, shear strength, and

volume change potential of a soil and how it may be affected

by water, frost, and other physical conditions. Also, using

soil classification symbols can assist a contractor in

estimating excavation and compaction characteristics,

potential dewatering situations, and workability.

The USCS is based on: (a) the distribution (gradation) of

various particle sizes, and (b) the plasticity characteristics of

very fine particles. Particle-size distribution is determined

from a gradation analysis test. In this test, soil is dried and

then shaken through a series of sieves having progressively

smaller openings. The soil mass retained on each sieve is

measured, and the percentage that passes the different

openings can be calculated. The gradation analysis test is

discussed in part B of this chapter. Plasticity characteristics

of the fines (particles that pass a U.S.A. Standard 75-μm

[No. 200] sieve and smaller) are determined by performing

the Atterberg limits tests. These tests are performed to

determine the moisture content of a soil when in a liquid,

plastic, semisolid, or solid state. The tests are discussed in

part B of this chapter.

Gradation analysis data are used to determine percentages of

gravel, sand, and fines in a soil; Atterberg limits are used to

determine whether the fines are silt or clay. The four basic

soil types are: gravel, sand, silt, or clay. Because soil can

contain all of these components, the classification system is

used to describe the major components; for example, clayey

sand with gravel, sandy silt, or silty clay with sand. The

percentages and behavior of each component can be

determined from laboratory tests or they can be estimated by

visual and manual tests in the field. However, in the USCS

system, the method of classification must be stated, whether

it is based on visual observations or on laboratory tests.

Unique factors must be realized when comparing the USCS

system with other classification methods. First, the USCS

is based only on the particles passing a 75-mm (3-in) sieve

opening. While particles larger than 75 mm are not used to

classify soil, they are of great importance in engineering use

of a soil in earthwork. Therefore, cobbles and boulders are

included in USCS names, and they are fully described in the

narrative portion of field logs.

Second, silt and clay are differentiated by their physical

behavior and not by their particle size. Other classification

systems define silts and clays as having specific particle

sizes with silts being the larger particle size. As a system

based on engineering properties, the USCS is concerned

only with plasticity characteristics of the fines and not the

particle sizes.

1-5. Gravel, Sand, Silt, and Clay.&The relative

amounts of gravel, sand, and fines; the plasticity

characteristics of the fines (silt, clay, or both); and the

presence of cobbles and boulders all affect the soil' s use as

a construction material. These characteristics also affect

selection of laboratory and field tests to be performed on the

soil.

Gravel particles are those passing a 4.75-mm (3-in) sieve

but retained on a 4.75-mm (No. 4) sieve. Sand particles

pass a 4.75-mm sieve and are retained on a 75-μm

(No. 200) sieve. Fines are soil particles that pass a 75-μm

sieve; they are further characterized as silt or clay, based on

their plasticity.

a. Gravel and Sand.&Gravel and sand have

essentially the same basic engineering properties, differing

mainly in degree. The division of gravel and sand sizes by

the 4.75-mm sieve is arbitrary and does not correspond to

an abrupt change in properties. When devoid of fines,

coarse-grained soils are pervious, easy to compact, and little

affected by moisture or frost action. Although particle

shape, angularity, gradation, and size affect the engineering

properties of coarse-grained soils, gravels are generally

more pervious, more stable, and less affected by water or

frost than are sands containing the same percentage of fines.

As a sand becomes finer and more uniform, it approaches

the characteristics of silt, with corresponding decreased

permeability and reduced stability in the presence of water.

Visually, very fine sands are difficult to distinguish from
EARTH MANUAL

4

silts. However, dry sand exhibits no cohesion (does not

hold together) and feels gritty in contrast to the very slight

cohesion and smooth feel of dried silt.

b. Silt and Clay (Fines).&In soils, small amounts of

fines may have important effects on engineering properties.

As little as 10 percent of particles smaller than the 75-μm

sieve size in sand and gravel may make the soil virtually

impervious, especially when the coarse grains are well

graded. Also, in well-graded sands and gravels, serious

frost heaving may be caused by less than 10-percent fines.

The utility of coarse-grained materials for surfacing roads,

however, can be improved by adding a small amount of clay

to act as a binder for the sand and gravel particles.

Soils containing large quantities of silt and clay are the most

troublesome in engineering. These materials exhibit marked

changes in physical properties with change of moisture

content. For example, a hard, dry clay may be suitable as

a foundation for heavy loads as long as it remains dry, but

may turn into a quagmire when wet. Many fine-grained

soils shrink on drying and expand on wetting; this may

adversely affect structures founded upon them or

constructed of them. Even when moisture content does not

change, the properties of fine-grained soils may vary

considerably between their natural condition in the ground

and their state after being disturbed. Fine-grained soils,

having been subjected to loading in geologic time,

frequently exhibit a structure that gives the material unique

properties in the undisturbed state. When soil is excavated

for use as a construction material or when a natural deposit

is disturbed, for example, by driving piles, soil structure is

destroyed, and soil properties are radically changed.

Silts differ from clays in many respects, but because of

similarity in appearance, often they are mistaken for each

other. Dry, powdered silt and clay are indistinguishable

from each other visually but are easily identified by their

characteristics when wet or moist. Recognition of fines as

having either silt or clay behavior is an essential part of the

Unified Soil Classification System.

Silts are slightly plastic or nonplastic fines. They are

inherently unstable when wet and have a tendency to

become "quick" when saturated and unconfined, assuming

the character of a viscous fluid, and commonly flow. Silts

are fairly impervious, difficult to compact, and highly

susceptible to frost heaving. Silt masses undergo change of

volume with change of shape (the property of dilatancy), in

contrast to clays, which retain their volume with change of

shape (the property of plasticity). Silts vary in size and

shape of particles; this is reflected mainly in

compressibility. For similar conditions of previous geologic

loading, the higher the liquid limit of a silt, the more

compressible it becomes.

Clays are plastic fines. They have low resistance to

deformation when wet but dry to hard, cohesive masses.

Clays are virtually impervious, difficult to compact when

wet, and impossible to drain by ordinary means. Large

expansion and contraction with changes in water content are

characteristic of clays. The small size, flat shape, and

mineral composition of clay particles combine to produce a

material both compressible and plastic. The higher the

liquid limit of a clay, the more compressible it will be when

compacted. Hence, in the Unified Soil Classification

System, the liquid limit is used to distinguish between clays

of high compressibility and those of low compressibility.

Differences in plasticity of clays are reflected by the

plasticity index. At the same liquid limit, the higher the

plasticity index, the more cohesive the clay.

c. Organic Matter.—The effect of organic matter upon

engineering properties is recognized in the USCS, and

organic soils are part of the classification system. Organic

matter in the form of fully or partly decomposed vegetation

can be found in many soils. Varying amounts of finely

divided vegetable matter are found in sediments and often

affect sediment properties sufficiently to influence their

classification. Thus, the USCS recognizes organic silts

having no or low plasticity and organic clays having

medium to high plasticity. Even small amounts of organic

matter in colloidal form in a clay may result in an

appreciable increase in liquid limit (and plastic limit) of the

material without increasing its plasticity index.

Generally, organic soils are dark gray or black in color and

usually have a characteristic decaying odor. Organic clays

feel spongy in the plastic range when compared to inorganic

clays. The tendency for soils high in organic content to

form voids through decay or to change the physical

characteristics of a soil mass through chemical alteration

makes them undesirable for engineering use. Soils

containing even moderate amounts of organic matter are

significantly more compressible and less stable than

inorganic soils; hence, they are less desirable for

engineering use.

1-6. Cobbles and Boulders.—While particles of

rock retained on a 75-mm (3-in) sieve are not considered

when classifying a soil according to the USCS, they can

have a significant effect on the construction use of a soil and

may need to be removed. The presence of cobbles and

boulders must always be noted in the group name of a soil

and in any description of the soil. Cobbles pass a 300-mm
CHAPTER 1—PROPERTIES OF SOILS

5

(12-in) square opening but are retained on a 75-mm sieve.

Boulders are too large to pass a 300-mm square opening.

Note that for engineering use, the definitions of cobbles and

boulders refer only to size. Some other definitions consider

particle angularity.

For soils that may be used in compacted embankments or

compacted backfill, cobbles must be identified as being

larger or smaller than 125 mm (5 in) in diameter, as a

typical compacted layer of cohesive soil is restricted to

about 150 mm (6 in) in thickness. The maximum particle

size allowed in the compacted layer is 125 mm. Thus,

particles larger than 125 mm must be removed or separated.

Logs and soil descriptions must state the percentage of

cobbles smaller than and the percentage larger than

125 mm. This topic is discussed in chapter 2, section 17:

Logging of Exploratory Holes.

1-7. Shale, Crushed Rock, and Slag.&The USCS

can also be used for describing materials such as shale,

siltstone, claystone, mudstone, sandstone, crushed rock,

slag, cinders, and shells. These materials are not

considered natural soils but they can be used as construction

materials.

In some cases, materials variously described as shale,

claystone, mudstone, or siltstone can be excavated with

construction equipment and then broken down using disking

or other methods into a material that can be used to

construct embankments or other earthworks. In the

laboratory, these materials can be processed into a "soil" by

grinding or slaking. They can then be classified according

to the USCS to evaluate their properties as a construction

material. However, these materials should not be primarily

classified or described as soil because that is not their

natural state.

To avoid misinformation, any log, report of laboratory test

results, or description(s) must identify the original material

as shale, claystone, etc. However, in the description of

material properties, a USCS soil classification symbol and

name may be used. The classification is secondary, and the

symbol and name are to be enclosed in quotation marks to

distinguish them from a typical soil classification as shown

in the following example:

SHALE CHUNKS: Retrieved as 50- to 100-mm pieces

of shale from power auger hole; dry, brown; no

reaction with HCl. After a sample was laboratory

processed by slaking in water for 24 hours, the sample

was classified as "SANDY LEAN CLAY (CL)" &

61-percent clayey fines, LL = 37, PI = 16; 33-percent

fine to medium sand; 6-percent gravel-size pieces of

shale.

Other examples are in USBR 5000 and 5005 [5] and training

manuals Nos. 4, 5, and 6 [7, 8, 9].

The same format applies to other materials not considered

to be natural soils, but which are used in construction such

as sandstone, crushed rock, slag, cinders, and shells.

For some materials, the laboratory processing required to

test the material as a soil may be significantly different than

the processing at the project site using construction

equipment. The differences must be considered when

evaluating the material for construction. Test sections are

often used as a final evaluation of whether to accept or

reject these materials.

1-8. Soil Composition.&In addition to soil

classification, knowledge of the mineralogy and origin of

soils can aid in evaluating the behavior of a soil. While silt

particles and sand-size particles are generally

equidimensional, clay particles are very small and are flaky,

or platelike, as shown on figure 1-2. As clay components

of soils become more predominant, the clay mineral

characteristics assume great importance. Soil properties

such as consistency, shear strength, and moisture content

are directly influenced by the mineral constituents of the

clay. When soils are fairly moist, clay particles are

surrounded by water films. As dehydration takes place, the

films become thinner and thinner until adjacent particles are

held together by strong cohesive (capillary) forces. As soils

are wetted, the films become weaker. Film strength also is

related to the fineness and specific surface of the material

and to compactness (density) which influences size of void

spaces.

The mineralogic clays in soils affect their physical behavior.

Two groups of clay minerals are of particular interest&the

kaolin group and the montmorillonite group. The kaolin

minerals have fixed crystal lattices or layered structure and

exhibit only a small degree of hydration and absorptive

properties. In contrast, montmorillonite minerals have

expanding lattices and exhibit a higher order of hydration

and cation absorption.

Montmorillonite soils, with their expanding lattice structure

and resulting capacity for wide ranges of water contents, can

be particularly troublesome. Settlement from shrinkage,

heave from swelling, and loss of strength and stability
EARTH MANUAL

6

Figure 1-2.—Clay kaolinite particles (1 ) = 0.001 mm).

caused by shrinkage or swelling can create major structural

problems. These problems are greatly magnified in the case

of hydraulic structures.

The clay mineral halloysite, illustrated on figure 1-3, can

cause construction problems. Typically, it is a hollow, rodshaped particle and decreases soil density. The soil changes

engineering behavior as its structure changes because of

particle breakdown during drying or construction and the

irreversible process of water being removed from inside the

tubal particles.

The presence of mica in soils causes a highly compressible

material. The thin, flaky particles act like springs that

separate other soil particles, thus creating low densities and

also deforming under load. This occurrence is especially

important in sands containing mica.

Many low-density deposits are found in the arid and

semiarid parts of the United States. These soils are

unsaturated deposits of loose, wind-deposited loess and

loess-like soils or colluvial and alluvial soils deposited by 

flash runoffs, often in the form of mudslides. In none of

these situations have the soils been completely wetted or

worked to allow breakdown and consolidation of the loose

structure. Generally, these soils have high dry strengths

created by a well dispersed clay binder. Major wind-blown

loess deposits are found in the Plains States of Kansas and

Nebraska and can be found in other areas. Loessial soils

form high vertical faces that are stable as long as the water

content is low. However, upon wetting, strength is largely

lost and slope failures occur. Similarly, loessial soils

support heavy structural loads on footings or pilings when

dry; however, they lose their bearing capacity and resistance

to compression when their loose structure collapses upon

becoming wet.

Certain alluvial fan soil deposits such as those adjacent to

the southwestern foothills of the Central Valley of California

have similar characteristics. When dealing with hydraulic

engineering works, where the subsoils will eventually

become saturated, it is imperative to recognize these soils'

characteristics and to take precautionary measures to

improve them before constructing structures on them.

Many engineering problems associated with the effects of

mineralogy and origin are discussed later in more detail in

this manual.
CHAPTER 1—PROPERTIES OF SOILS

7

Figure 1-3.—Halloysite particles (1) = 0.001 mm).

B. Index Properties of Soils

1-9. General.&Engineers are continually searching

for simplified tests that will increase their knowledge of

soils beyond that which can be gained from visual

examination without having to resort to the expense, detail,

and precision required for engineering properties tests.

These simplified index tests or physical properties tests

provide indirect information about engineering properties of

soils; the most widely used are gradation analyses and

Atterberg limits tests. Both tests define the limits of the

various groups of soils when using the USCS.

Moisture content and density relationships are commonly

used as index properties in evaluating foundations and for

construction control. Other index tests include:

 ̆ Laboratory penetration resistance needle tests on

compacted specimens

 ̆ Field penetration resistance tests with split-tube drive

samplers

 ̆ Unconfined compression tests on undisturbed or

compacted samples of fine-grained cohesive soil

Data secured from index tests, together with descriptions of

visual observations, are often sufficient for design purposes

for minor structures. This information is used also in

making preliminary designs for determining probable cost

of a major structure and to limit the amount of detailed

testing. An assumption is that construction materials within

a limited area, having similar index properties, will exhibit

similar engineering properties; however, correlations

between index properties and engineering properties are not

perfect. If index properties are used in design, a liberal

factor of safety should be included.

1-10. Terms and Units of Measure.&The terms

and units of measure used here follow.

a. Mass.&Mass, the amount of matter an object

contains, remains constant even if temperature, shape, or

other physical attributes of the object change. The object' s

mass does not depend on local gravitational attraction and is

independent of the object' s location in the universe. The

output or reading from any type of balance or scale is

mass¬ weight. Typical units of mass are gram (g) or

kilogram (kg) and pound mass (lbm).

b. Density.&Density is mass per unit volume. The

symbol for density is the lowercase Greek letter rho, '.

Units of density are megagram per cubic meter (Mg/m3) and

pound mass per cubic foot (lbm/ft3).

c. Weight.&Weight is the gravitational force that

causes a downward acceleration of an object. Units of

weight are the same as units of force: newton (N) and

pound force (lbf).
EARTH MANUAL

8

Coefficient of uniformity, Cu = D60

D10

1-2

Coefficient of curvature, Cc ˆ (D30)

2

D10 × D60

1-3

d. Unit Weight.&Unit weight is weight per unit

volume. The symbol for unit weight is the lowercase Greek

letter gamma, ı. Units of unit weight are kilonewton per

cubic meter (kN/m3) and pound force per cubic foot

(lbf/ft3).

e. Percentage and Decimal Use.&Certain terms

pertaining to soil properties are customarily expressed as a

percentage, whereas others are usually expressed as

decimals. For example, degree of saturation (S), moisture

content (w), and porosity (n) are commonly written in

percentage as:

S = 85.6%, w = 16.2%, and n = 34.3%

Conversely, void ratio (e) and specific gravity (Gs) are

expressed in decimals as:

e = 3.52, and Gs = 2.76

To avoid confusion in computations involving these

quantities, a simple rule should be followed: Always

express quantities as a decimal in all computations. The

answers can be given as percentages&provided the percent

sign is used, as shown in the following example.

Given: 

ıd = 113.2 lbf/ft3, w = 16.2%, Gs = 2.76, and

n = 34.3%.

Find the degree of saturation, S

S = 

w G

n

 - n

 = 

 - 

 = s

1

0 162 2 76

0 343

1 0 343

0 856 85 . .

.

.

. %

×

or 1-1

1-11. Gradation.&Gradation is a descriptive term that

refers to distribution and size of grains in a soil. It is

determined by the gradation analysis of soils, 3

 and is

presented in the form of a cumulative, grain-size curve in

which particle sizes are plotted logarithmically with respect

to percentage (by dry mass) of the total specimen plotted to

a linear scale (fig. 1-4).

Certain terms and expressions are used when referring to a

gradation curve. A particular diameter of particle is

indicated by D with a numeric subscript that corresponds to

a point on the curve equivalent to the percentage of particles

passing. On figure 1-4, D10 equals 0.075 mm. This means

10 percent, by dry mass of soil, is composed of particles

smaller than 0.075 mm. The 10-percent size (D10 size) is

also called the "effective" grain size. This term was

introduced by Hazen [10] in connection with his work on

sanitary filters. Hazen found that sizes smaller than the

effective grain size affected the functioning of filters as

much or more than did the remaining 90 percent of sizes.

Other sizes, such as D15, D50, and D85, are also used in filter

design. The sizes D10, D30, and D60 are used in defining the

gradation characteristics of a soil. The gradation curve is

used to designate various soil components by grain size.

A soil is said to be well graded when a good representation

of all particle sizes exists&from the largest to the smallest.

A soil is considered to be poorly graded if an excess or a

deficiency of certain particle sizes occurs within the limits

of the minimum and maximum sizes or if the range of

predominant sizes falls within three or less consecutive

sieve-size intervals on the gradation curve. A poorly graded

soil is called uniform if all the particles are about the same

size. When there is an absence of one or more intermediate

sizes, the material is said to have a gap or skip gradation.

To determine whether a material is well graded or poorly

graded, coefficients describing the extent and shape of the

gradation curve have been defined as follows and illustrated

on figure 1-4:

To be well graded, a material must have a coefficient of

curvature between 1.0 and 3.0; in addition, the coefficient

of uniformity must be greater than 4.0 for gravels and

greater than 6.0 for sands. If one or both of these criteria

are not satisfied, the soil is poorly graded. A poorly graded

soil having a coefficient of uniformity of 2.0 or less is

uniform [11].

3

 5325: Performing Gradation Analysis of Gravel Size Fraction of

Soils.

5330: Performing Gradation Analysis of Fines and Sand Size

Fraction of Soils, Including Hydrometer Analysis.

5335: Performing Gradation Analysis of Soils Without Hydrometer&

Wet Sieve.

5345: Performing Gradation Analysis of Soils by the Bottom

Withdrawal Test Method.

(Numbered footnotes refer to groups of related soil testing procedures, as

described in Part 2 of the Earth Manual. Each footnote lists the soil testing

procedures in a group by their USBR designations.)
CHAPTER 1—PROPERTIES OF SOILS

9

Figure 1-4.—Gradation plot.

A soil sample may be divided into parts&called

fractions&based on grain size. For example, in construction

control of earthwork, soil is frequently divided into two

fractions using the U.S.A. Standard 4.75-mm sieve (No. 4).

The fraction finer than the 4.75-mm sieve (the minus

4.75-mm fraction) is called the control fraction, and the

 fraction coarser than the 4.75-mm sieve (the plus 4.75-

mm fraction) is called the oversize.

A number of different upper-size limits are frequently used

in appraising soils. The workability of a soil is often

affected appreciably by the largest soil particles present.

Important upper-size limits for various applications are:
EARTH MANUAL

10

U.S.A. Standard Series

Sieve Size Application

300 mm 12 inch Sand, gravel, and cobble fill;

division between cobbles and

boulders

125 mm 5 inch Impervious rolled fill

75 mm 3 inch Soil classification, large-scale

laboratory testing, division

between gravel and cobbles

4.75 mm No. 4 sieve Most laboratory testing,

division between sand and

gravel

425 )m No. 40 sieve Atterberg limits test

75 )m No. 200 sieve Division between fines and

sand

Use of gradation in determining engineering properties is

limited to coarse-grained materials. In poorly graded

uniform materials, permeability increases approximately as

the square of the effective grain size (D10) [10]. For such

materials, compressibility is normally small except for in

very fine sands. Shear strength consists almost wholly of

internal friction and is more or less independent of grain

size. Uniform materials are generally workable; that is,

they are easily excavated and compacted. As the range in

sizes of coarse-grained soils increases:

 ̆ permeability decreases,

 ̆ compressibility decreases, and

 ̆ shear strength increases.

Workability of well-graded soil is good.

Amount and plasticity of fines influence the properties of

coarse-grained materials. Permeability is reduced with

increasing quantity of fines&rapidly with a small quantity

and at a slower rate with a large quantity. Compressibility

and shear strength are affected only slightly by small

percentages of fines in coarse-grained soils, but the effects

increase with increase in fines.

1-12. Atterberg Limits.&The physical properties of

most fine-grained soils, and particularly clayey soils, are

greatly affected by moisture content. The consistency of a

clay may be very soft, that is, a viscous liquid; or it may be

very hard, having the properties of a solid&depending on its

moisture content. In between these extremes, clay may be

molded and formed without cracking or rupturing the soil

mass. In this condition, it is referred to as being plastic.

Plasticity is an outstanding characteristic of clays and is

used to identify and classify clayey soils.

In 1911, a Swedish soil scientist, A. Atterberg, developed

a series of hand-performed tests for determining the clay

activity or plasticity of soil [12]. These tests are known as

the Atterberg limits tests. The series of tests is common to

engineering classification of soil.

The consistency of a soil can go through four stages:

1. liquid,

2. plastic,

3. semisolid, and

4. solid.

The stages are related to moisture content. Although the

transition between stages is gradual, test conditions have

been arbitrarily established to delineate the moisture content

as a precise point in the transitions between the four stages.

These moisture contents, which are determined by ovendrying procedures, are called the:

 ̆ liquid limit,

 ̆ plastic limit, and

 ̆ shrinkage limit.

As the tests are performed only on the soil fraction that

passes the U.S.A. Standard 425-μm (No. 40) sieve, the

relation of this fraction to total material must be considered

when determining the state of the total material from these

tests.

The significance of the limits and their relation to the phases

of a soil-water system can be explained by referring to

figures 1-5 and 1-6. As a very wet, fine-grained soil dries,

it passes progressively through different phases. In a very

wet condition, the mass acts like a viscous liquid, which is

referred to as the liquid state. As the soil dries, a reduction

in volume of the mass takes place that is nearly proportional

to the loss of water. When moisture in a soil is at a value

equivalent to the liquid limit, the mass becomes plastic.

Liquid limit, LL, is that moisture content (expressed as a

percentage of the dry mass of soil) when the soil first shows

a small but definite shear strength as moisture content is

reduced. Conversely, with increasing moisture, liquid limit

is that moisture content when the soil mass just begins to
CHAPTER 1—PROPERTIES OF SOILS

11

Figure 1-5.—Consistency limits.

Figure 1-6.—Phases of a soil-water system.
EARTH MANUAL

12

LI =

wn  ̃ PL

PI

1-4

Cr = LL  ̃ wn

PI

1-5

become fluid under the influence of a series of standard

blows, as outlined in USBR 5350 and 5355.4

As moisture content is reduced below the liquid limit, the

soil mass becomes stiffer and will no longer flow as a

liquid. However, it will continue to be deformable, or

plastic, without cracking until the plastic limit is reached.

Plastic limit, PL, is that moisture content (expressed as a

percentage of the dry mass of soil) when the soil mass

ceases to be plastic and becomes brittle, as determined by a

procedure for rolling the soil mass into threads 3 mm

(1/8 in) in diameter. Plastic limit is always determined by

reducing the moisture content of the soil mass.

As the moisture content of soil is reduced below the plastic

limit, the soil becomes a semisolid; that is, it can be

deformed, but considerable force is required and the soil

cracks. This condition is referred to as a semisolid state.

As further drying takes place, the soil mass will eventually

reach a solid state when further volume change (shrinkage)

will not occur. Moisture content under this condition is

called shrinkage limit, SL. This is the moisture content at

which a reduction in moisture will not cause a decrease in

the volume of the soil mass. Below the shrinkage limit, soil

is considered to be a solid; that is, most particles are in very

close contact and are very nearly in an arrangement which

will result in the most dense condition. 

In most fine-grained plastic soils, plastic limit will be

appreciably greater than shrinkage limit. However, for

coarser fine-grained soils (soils containing coarse silt and

fine sand sizes), the shrinkage limit will be near the plastic

limit. The shrinkage limit, together with other indexes, is

useful in identifying expansive soils [13].

Plasticity index, PI, is the difference between the liquid and

plastic limits, and represents the range of moisture content

over which soil is plastic. (See figs. 1-5 and 1-6 and the

plasticity chart on fig. 1-7.) Silts have low or no plasticity

indexes, whereas clays have higher indexes. Plasticity

index, in combination with liquid limit, indicates how

sensitive a soil is to change in moisture content.

Liquidity index, LI, is the ratio of the difference between

natural moisture content and plastic limit, wn % PL, to the

plasticity index, PI:

Liquidity index is a useful indicator of the behavior of a

fine-grained soil when sheared. If liquidity index is less

than zero (negative), soil at natural moisture will exhibit

brittle stress-strain behavior if sheared. If liquidity index is

between zero and one, soil at natural moisture will behave

like a plastic. If liquidity index is greater than one, soil at

natural moisture will act like a viscous liquid when sheared

[14].

Relative consistency, Cr, is the ratio of the difference

between liquid limit and natural moisture content to the

plasticity index:

If moisture content of a soil in its natural state, or in place,

is greater than the liquid limit (relative consistency less than

zero), any process of remolding will transform the soil into

a thick, viscous slurry. If natural moisture content is less

than the plastic limit (relative consistency greater than one),

the soil cannot be remolded [15].

Soils may be grouped according to their liquid limits and

plasticity indexes on a plasticity chart as shown on

figure 1-7. Such plots can be useful in predicting properties

of soils by comparing with similar plots for tested soils (see

fig. 1-8).

As an index of engineering properties, soil plasticity applies

only to fine-grained soils. The variation of engineering

properties is generally related to the four zones on the

plasticity chart (fig. 1-7), which determines the soil

classification group. For soils plotting above the "A" line,

permeability is very low. Compressibility increases with

increasing liquid limit. For the same liquid limit, the

greater the plasticity index, the greater will be the shear

strength at the plastic limit.

1-13. Porosity and Void Ratio.&In evaluating a

soil, either the amount of solids contained in a given volume

or the remaining voids can be considered. Many of the

computations in soil mechanics are simplified by considering

the voids rather than the solids. Two expressions, porosity

and void ratio, are used to define the void space. Porosity,

n, is the ratio (expressed as a percentage) of space in the

soil mass not occupied by solids (volume of voids) with

respect to total volume. Void ratio, e, is the ratio of space

4

 5350: Determining the Liquid Limit of Soils by the One-Point

Method.

5355: Determining the Liquid Limit of Soils by the Three-Point

Method.
CHAPTER 1—PROPERTIES OF SOILS

13

Figure 1-7.—Plasticity chart.

n ˆ Vv

Vt

ˆ e

1  ̄ e

e ˆ Vv

Vs

ˆ n

1  ̃ n

1-6

1-7

not occupied by solid particles (volume of voids) to the

volume of solid particles in a given soil mass. These

relationships are expressed as follows:

where:

n = porosity expressed as a percentage

e = volume of voids to volume of solid particles

Vt = total volume

Vv = volume of voids

Vs = volume of solid particles

Porosity and void ratio are measures of the state or

condition of a soil structure. As porosity and void ratio

decrease, engineering properties of a given soil become

more dependable with decreases in permeability and

compressibility and an increase in strength. As porosity

decreases, and, consequently, the void ratio decreases,

excavating the material becomes more difficult. At a given

moisture content, the compactive effort must be increased

to obtain a decrease in porosity. However, similar

properties may be obtained in different soils at widely

different conditions of porosity. Engineering properties of

a soil do not vary directly with its porosity; the relationship

is complex.

1-14. Specific Gravity.&In investigating a soil, the

most easily visualized condition involves the volume

occupied by soil solids, Vs , the volume occupied by water,

Vw, and the volume occupied by air, Va, in the soil mass

(fig. 1-9). However, most measurements are more readily

obtained by mass. To correlate mass and volume, the

specific gravity factor is required. Specific gravity is

defined as the ratio between the density of a substance and

the density of water at 4 (C. Several different types of

specific gravity are in common use. Reclamation uses

apparent specific gravity and several types of bulk specific

gravities. These values are obtained using methods outlined

in USBR 5320: Determining Specific Gravity of Soils5

5

 5320: Determining Specific Gravity of Soils.
EARTH MANUAL

14

Figure 1-8.—Typical relationships between the liquid limit and the 

plasticity index for various soils.

n ˆ 1  ̃ Vs

Vt

ˆ 1  ̃ ıd

ıw Ga

e ˆ Vt

Vs

 ̃ 1 ˆ ıw Ga

ıd

 ̃ 1

S ˆ Vw

Vv

ˆ w Ga

e

1-8

1-9

1-10

Apparent specific gravity, Ga, is determined on soil particles

as they occur naturally. Voids that exist within grains and

cannot be filled with water are referred to as "impermeable

voids." Apparent specific gravity ranges from 2.50 to 2.80

for most soils, with a majority of soils having an apparent

specific gravity near 2.65. Unless specifically stated to the

contrary, "specific gravity" (in this manual) is assumed to

mean the "apparent specific gravity." It is used to compute

many important soil properties involving volume

determinations such as porosity, void ratio, and degree of

saturation as shown in the following equations:

where:

e = volume of voids to volume of solid particles

n = porosity expressed as a percentage

s = degree of saturation

w = moisture content

Vv = volume of voids

Vs = volume of solid particles

Vt = total volume

Vw = volume of water

ıd = dry density

ıw = density of water at 4 (C

Bulk specific gravity (specific mass gravity), Gm, is the

specific gravity having the permeable or surface voids of the

particles filled with water. This value is smaller than the

value determined for apparent specific gravity unless there

are no permeable voids within the particles. The bulk

specific gravity, saturated surface dry, of aggregate

(sand and gravel) is used for concrete mix design and also

for quality tests for riprap and rockfill materials. The bulk
CHAPTER 1—PROPERTIES OF SOILS

15

Figure 1-9.—Relationship between air, water, and solids in a soil mass.

specific gravity of gravel particles may be determined on a

wet, surface-dry basis, where permeable voids may not be

entirely filled with water. Bulk specific gravity (wet surface

dry) is used in all in situ density testing procedures. Bulk

specific gravity (ovendry) is, in effect, the minimum dry

density of all particles distributed throughout the entire or

effective volume of particles; that is, both impermeable and

permeable voids associated with individual particles in the

ovendry condition are included in the volume determination.

It is the smallest value of the different specific gravities.

As an index test, specific gravity is somewhat indicative of

the durability of a material. Materials having low specific

gravity are likely to break down and change properties with

time whereas, high specific gravity materials normally do

not deteriorate rapidly. The test is applicable primarily in

evaluating coarse-grained materials and riprap or rockfill

materials.

1-15. Moisture Content.&Moisture content, w, is

defined as the ratio (expressed as a percentage) of mass of

water to mass of soil solids. Moisture (water) is the most

influential factor affecting soil properties. Also, it is the

principal factor subject to change either from natural causes

or at the discretion of the engineer. In soil used as

construction material or as encountered in foundations, the

control of moisture often represents an important part of the

structure' s cost and may considerably influence the

construction procedures used. Therefore, it is essential that

the moisture content of a soil be determined, recorded, and

reported in conjunction with all investigations, tests, and

construction control work. Moisture content is an important

factor in formulating designs, and the requirements for

moisture are delineated in most specifications for

construction. Regarding materials or foundation

investigations, descriptive terms such as dry, moist, and wet

may provide sufficient information to decide whether to use

a given material. In all tests and in construction control

procedures, a quantitative determination of moisture content

is required. Moisture content is determined by a particular

testing procedure. 6

6

 5300: Determining Moisture Content of Soil and Rock by the Oven

Method.

5305: Determining Moisture Content of Soils Using the Moisture

Teller Device.

5310: Determining Moisture Content of Soils Using the Calcium

Carbide Reaction Device.

5315: Determining Moisture Content of Soils by the Microwave

Oven Method.
EARTH MANUAL

16

w = P1

w1

100

 ̄ P2

w2

100

 ̄ ....  ̄ Pn

wn

100

1-11

Note that moisture content is expressed as a percentage of

the dry mass of soil. Because moisture content is measured

in terms of mass, it is independent of the volume occupied

by the soil mass; that is, moisture content does not change

whether material is in a loose state or in a dense state.

Drying a soil specimen to a constant dry mass at a

temperature of 110 (C (see USBR 5300) is accepted as a

standard method for determining moisture content.

Occasionally, however, soils are encountered for which this

procedure is not valid; then, special methods are required.

Soils containing organic matter, an appreciable amount of

soluble solids, or unusual clay minerals such as halloysite or

allophane require special treatment. Sometimes, ovendrying

causes irreversible changes in soil properties; therefore,

ovendried materials should not be used in laboratory tests

unless specifically required.

a. Optimum Moisture Content.&In 1933,

R.R. Proctor [16, 17, 18, 19] showed that the dry density

of a soil obtained by a given compactive effort depends on

the amount of water the soil contains during compaction.

He pointed out that, for a given soil and a given compactive

effort, there is one moisture content that results in a

maximum dry density of the soil, and that moisture contents

both greater and smaller than this optimum value will result

in dry densities less than the maximum (see fig. 1-10c). As

early as 1934, moisture content at maximum dry density

was termed optimum moisture content, wo, by other

investigators of soil compaction [20]. As defined for

Reclamation work, optimum moisture content is based on

the compactive effort for the standard laboratory compaction

test described in USBR 5500. 7

 Figure 1-11 shows the

variation of optimum moisture content when compactive

effort is varied from the standard [21].

b. Absorbed Moisture.&Absorbed moisture is that on

saturated surface-dry particles. Depending upon moisture

conditions in a soil containing gravel-size particles,

sufficient moisture may not always be available for the

gravel to take up the maximum amount. The actual amount

of absorbed moisture is determined by separating the gravel

from the other soil particles and determining the wet and dry

mass of the gravel. 8

If a soil has been separated into fractions by sieving,

average moisture content of the total material, w, (in

percent) may be calculated by:

where:

P1 , P2 , Pn = percent of each size fraction in total

material, %

w1 , w2 , wn = moisture content of each size fraction,

%

100 = constant representing the total

materials, %

Engineering properties change so much with moisture

content that it is used primarily to assist in interpreting other

index properties. Primarily, moisture content is used to

evaluate soils in their natural state, both as foundations and

as construction materials sources.

1-16. Density and Unit Weight.&Mass or weight of

a unit volume of soil is an easily determined property.

Consequently, density and unit weight are basic parameters

to which all other performance characteristics are related.

Relationships between density, unit weight, and other soil

properties&as a rule&are complex, but in engineering

practice, simple relationships are assumed to exist. A large

number of qualified expressions are in common use for

density or unit weight. To avoid confusion, the kind of

density or unit weight reported must be clearly delineated.

Generally, density is used in laboratory testing and

construction control; unit weight is used in engineering

analysis and design.

a. In Situ Unit Weight.&The soil' s unit weight as it

exists in a natural deposit, at any particular time, is the inplace or natural unit weight. It can be determined either by

measuring the mass and volume of an undisturbed sample of

material or by measuring the mass of material removed from

a hole of known volume. In-place density is calculated from

mass and volume and then converted to unit weight. Inplace unit weight is used in engineering computations such

as:

 ̆ slope stability,

 ̆ bearing capacity, 

 ̆ settlement analyses, and

 ̆ determining earth pressures.

In some soil types, sufficient correlations exist between inplace unit weight and compression characteristics so that

foundations for simple structures may be designed based

only on those data and a knowledge of in-place unit weight

7

 5500: Performing Laboratory Compaction of Soils&5.5-lbm

Rammer and 18-in Drop.

8

 Determining Unit Weight of Soils In-Place by the Sand Replacement

Method in a Test Pit.
CHAPTER 1—PROPERTIES OF SOILS

17

Figure 1-10.—Gradation, penetration, and compaction curves for various

soils.
EARTH MANUAL

18

Figure 1-11.—Effect of compactive effort on the compaction and penetration-resistance curves.
CHAPTER 1—PROPERTIES OF SOILS

19

ıd = ıwet

1  ̄ w

100

1-12

Dd = emax  ̃ e

emax  ̃ emin

100 1-13

Dd = ıdmax

ıd

ıd  ̃ ıdmin

ıdmax  ̃ ıdmin

1-14

in the foundation under consideration. The in-place or

natural unit weight can be expressed as a wet or dry unit

weight.

b. Wet Unit Weight.&The unit weight of the solid

particles and the contained water is called wet unit weight,

ıwet. It includes&but is not restricted to&in-place unit

weight. The method for its determination and its application

is the same as that previously described in "In situ unit

weight."

c. Dry Unit Weight.&Dry unit weight is the normal

expression for unit weight of soil. It is regarded as a fixed

quantity independent of moisture content unless compactive

effort is applied to the soil to change it. Dry unit weight,

ıd, is computed from wet unit weight, ıwet, and moisture

content using the following:

where:

w = moisture content

ıd = dry unit weight

ıwet = wet unit weight of solid particles plus contained

water

d. Laboratory Maximum Dry Unit Weight.&Dry unit

weight&produced with Reclamation' s standard compactive

effort at optimum moisture content&is called the laboratory

maximum dry unit weight. Test procedures are performed

on the soil fraction that passes the U.S.A. Standard 4.75-

mm (No. 4) sieve, according to procedures outlined in

USBR 5500, which provides a compactive effort of

600 kN-m/m3

 (12,375 ft-lbf/ft3). Figure 1-10c shows the

variation in laboratory maximum dry unit weight for several

soil types. Figure 1-11 shows typical compaction curves of

various compactive efforts expressed in terms of number of

standard blows per layer of soil. The maximum density and

the optimum moisture content vary with the compactive

effort. When the first laboratory compaction test procedure

was developed, the compactive effect used was similar to

the compactive effort of the construction equipment used to

compact soils in the field. As construction equipment got

heavier, additional procedures using various compactive

efforts were developed. Reclamation has maintained a

single standard. However, Reclamation may specify

percentages of the maximum density and deviations from

optimum moisture for various types of earthwork

construction.

e. Relative Density.&Soils consisting almost

exclusively of coarse-grained particles (e.g., sands and

gravels), when compacted by impact according to

procedures outlined for determining laboratory maximum

dry unit weight, have unit weight-moisture content

relationships that correlate poorly with other properties.

Furthermore, compaction curves are erratic; often they do

not produce a definable maximum unit weight. To evaluate

such soils, relative density (Dd) procedures consisting of

three independent laboratory and field determinations have

been developed. 9

When shear strength of coarse-grained soils is correlated

with unit weight in the range between minimum and

maximum index unit weights, a fairly reliable relationship

exists. With a reasonable amount of construction control,

a given type and amount of compactive effort can be

expected to produce a related relative density. In practice,

a relative density of 70 percent or greater is satisfactory for

most conditions. However, special analyses of sands and

gravels may be required to assess liquefaction potential in

zones of high earthquake probability. While several

different relationships for expressing the relative

density exist, the original and the one now generally used is

to express relative density (Dd) in terms of void ratio using

the following:

where:

Dd = relative density expressed as a percentage

e = void ratio in place

emax = void ratio in loosest state

emin = void ratio in densest state

Relative density may also be expressed in terms of dry unit

weight as follows:

9

 5525: Determining the Minimum Index Unit Weight of

Cohesionless Soils.

5530: Determining the Maximum Index Unit Weight of Cohesionless

Soils.

7250: Determination of Percent Relative Density.
EARTH MANUAL

20

ıt = 1

P

ıw Gm

 ̄ 1  ̃ P

ıds

1-15

 where:

ıd = dry unit weight in place

ıdmax = dry unit weight in densest state

ıdmin = dry unit weight in loosest state

Figure 1-12 shows a chart from which relative density may

be determined if the maximum index, minimum index, and

in-place or compacted-fill dry unit weights of a material are

known. Figure 1-12 also shows the maximum and

minimum index dry unit weights for a variety of sands and

gravels. Figure 1-13 shows the variation of maximum and

minimum index unit weights as various percentages of

gravel were added to a sand [22].

f. Compacted-Fill Unit Weight.&The soil' s unit

weight as it is compacted into a constructed fill is called the

compacted-fill unit weight to distinguish it from in-place unit

weight of a foundation or any of the various unit weights

determined in the laboratory. Usually, it is expressed as dry

unit weight, although wet unit weights are used to some

extent. The compacted-fill unit weight may be determined

by any one of a number of test procedures.

Compacted-fill unit weight is used primarily for construction

control to ensure that compacted fill is at least as dense as

assumed in preparing designs.

If a cohesive soil contains an appreciable quantity of

coarse-grained particles retained on the U.S.A. Standard

4.75-mm (No. 4) sieve, an adjustment must be made in the

compacted fill dry unit weight. The theoretical dry unit

weight of total material, plus 4.75 mm and minus

4.75 mm, comparable to the laboratory maximum dry unit

weight, is computed using the following [23]:

where:

Gm = bulk specific gravity (oven dry) of plus 4.75-

mm fraction

P = percentage of plus 4.75-mm material to total

material (dry mass basis) expressed as a

decimal

ıt = theoretical dry unit weight of total material

ıds = dry unit weight of minus 4.75-mm fraction

ıw = unit weight of water at 4(C

Equation 1-15 gives theoretical dry unit weight of total

material for different percentages of plus 4.75-mm (plus

No. 4) particles of a given specific gravity assuming that

each plus 4.75-mm particle is surrounded by minus

4.75-mm material. The equation is meaningless for

percentages of plus 4.75-mm material for which the unit

weight of plus 4.75-mm material corresponds to greater than

100-percent relative density of the plus 4.75-mm material

when considered alone (fig. 1-14). This occurs at about 70

to 80 percent of plus 4.75-mm material, depending on

gradation and on specific gravity. For plus 4.75-mm

contents above about 30 percent, studies have shown

compacted dry unit weight of soil in the field is less than the

theoretical dry unit weight although, for many soils,

compaction is not seriously affected until the percentage of

plus 4.75-mm material rises to about 40 or 50 percent. For

these soils, the usual assumptions of correlation between dry

unit weight and other soil properties are not true. For such

soils used in fill, special tests must be made. Figure 1-14

(and fig. 6 in USBR 5515)10 illustrates relationships of

various dry unit weights of mixtures of plus 4.75-mm and

minus 4.75-mm materials [24].

1-17. Penetration Resistance.&

a. Soil Plasticity.&In 1933, R.R. Proctor developed a

simple instrument called a "soil-plasticity needle" that could

be used to correlate moisture content-dry density

relationships of soils used in construction [18]. He noted

that for a given compactive effort upon a given soil, a curve

could be developed relating the penetration resistance of a

small rod (needle) with the soil’s moisture content.

10 5515: Performing Laboratory Compaction of Soils Containing

Gravel.

7205: Determining Unit Weight of Soils In-Place by the Sand-Cone

Method.

7206: Determining Unit Weight of Soils In-Place by the Rubber

Ballon Method.

7215: Determining Unit Weight of Soils In-Place by the Sleeve

Method.

7220: Determining Unit Weight of Soils In-Place by the Sand

replacement Method in a Test Pit.

7221: Determining Unit Weight of Soils In-Place by the Water

Replacement Method in a Test Pit.

7230: Determining Unit Weight and Moisture Content of Soils InPlace Nuclear Moisture-Density Gauge.
CHAPTER 1—PROPERTIES OF SOILS

21

Figure 1-12.—Typical minimum and maximum dry unit weights for various coarse-grained soils.
EARTH MANUAL

22

Figure 1-13.—Maximum and minimum index dry unit weights of typical sand and gravel soils [15].
CHAPTER 1—PROPERTIES OF SOILS

23

Figure 1-14.—Maximum dry unit weight versus gravel content for compacted soils.

Figures 1-10b and 1-11 show penetration resistance plotted

as ordinate versus moisture content as abscissa. The curve

begins with a rather high penetration resistance at a point on

the compaction curve&dry of optimum moisture content.

Then, penetration resistance decreases rapidly and almost

uniformly to a rather low value at a point wet of optimum

moisture content. From there, the decrease in penetration

resistance is gradual to zero near the liquid limit. The

curve' s straight line part, where penetration resistance

decreases rapidly, is normally the useful part of the curve.

The penetration resistance test is described in USBR 5505. 11

The test was formerly used to compare the resistance (of a

specimen compacted according to the standard laboratory

procedure) to the compaction achieved in the fill at the same

moisture content. When fill material contained an

appreciable amount of plus 4.75-mm particles, the test was

not dependable. This approximate method of controlling

compaction, called the "needle-density test," has now been

replaced by the rapid method of construction control test.11

b. Penetration Test.&The standard penetration test12

is used in foundation exploration to indicate relative density

of in situ cohesionless soils and may be used to estimate

unconfined compressive strength of cohesive soils in situ.

The test is performed using a standard sampler and a

standard sampling procedure. The sampler is at least 840

mm long, has a constant 50-mm outside diameter, and a

constant 35-mm inside diameter (33 by 2 by 1G in).

Penetration resistance is measured on the basis of the

number of blows of a 64-kg rammer dropped 762 mm

required for a sampler penetration of 305 mm (140 lbm at

30 in for 1 ft). The range in which these data are best

interpreted extends from a lower limit of 5 to 10 blows per

11 5505: Determining Moisture Content-Penetration Relationships of

Fine-Grained Soils.

12 7215: Performing Penetration Resistance Testing and Sampling of

Soils.
EARTH MANUAL

24

Table 1-1.—Relationship between consistency, unconfined compressive 

strength, and penetration resistance, N

Consistency Field identification

Unconfined compressive

strength, qu , ton / ft2

Penetration

resistance, N

 Very soft Easily penetrated several inches by fist Less than 0.25 Below 2

 Soft Easily penetrated several inches by thumb 0.25 to 0.5 2 to 4

 Medium Can be penetrated several inches by thumb with

moderate effort

 0.5 to 1.0 4 to 8

 Stiff Readily indented by thumb but penetrated only with

great effort

 1.0 to 2.0 8 to 15

 Very stiff Readily indented by thumbnail 2.0 to 4.0 15 to 30

 Hard Indented by thumbnail with difficulty Over 4.0 Over 30

305 mm to an upper limit of 30 to 50 blows per 305 mm.

It is applicable only to nonlithified soils including fairly

clean sands and gravels smaller than about 10 mm (G in) at

a variety of moisture contents and in saturated or nearly

saturated fine-grained soils. Soil deposits containing

appreciable gravel content cannot be tested reliably because

of the sampler bearing directly on gravel particles, damage

to equipment, and possible plugging of the sampler

barrel&all of which result in high blow count values.

Deposits containing coarse gravel, cobbles, or boulders

typically result in penetration refusal and damage to

equipment. Data from this test require interpretation by

experienced practitioners and should take into account:

 ̆ soil type,

 ̆ moisture content,

 ̆ methods of drill hole advance,

 ̆ ground-water conditions, and

 ̆ purpose for performing the test.

Figure 1-15 shows the relationship of blow count to relative

density. Figure 1-15a is a relationship determined from

chamber testing of clean sands in the laboratory under

various overburden pressures. The tests were performed on

fine to coarse sands containing less than 5-percent fines; this

relationship is not applicable to sands containing more than

10-percent fines or those containing gravel particles. The

relationship is converted to a more convenient form, on

figure 1-15b, for use in analyzing field data. The graph' s

vertical pressure scale can be converted to a depth scale by

estimating the in-place wet density of soil. For tests below

the water table, in situ submerged density must be used,

taking into account the buoyant effect of water, that is, in

situ wet density of the soil minus density of water. Using

the graph in this manner, penetration resistance is plotted

against depth; relative density is determined according to the

relative density zone in which the point is plotted. More

recently, additional laboratory chamber tests were

performed by the Corps of Engineers, and their work

confirms the relationships shown on figure 1-15 [25, 26].

The relative consistency of saturated fine-grained soils can

be estimated by the standard penetration test. As the values

obtained for these soils are only qualitative, table 1-1 and

figure 1-16 can be used to provide an approximate

evaluation of a soil.

1-18. Unconfined Compressive Strength.&The

internal friction component of undrained shear strength for

fine-grained soils in a saturated or nearly saturated state is

usually small. A compression test made without benefit of

confining pressure is assumed to provide an index of the

available undrained shear strength of a soil that will be

somewhat conservative. A variety of equipment has been

developed for making the tests. The devices range from

simplified equipment and procedures&from which test

results are of value only as an index test&to rather complex

equipment and test procedures that provide reliable data on

engineering properties. The unconfined compressive

strength of a soil is the strength of a cylindrical specimen

(maximum axial load divided by cross-sectional area) tested

in compression with the lateral pressure equal to

atmospheric or zero gauge pressure.

1-19. Soluble Solids.&The quantity of soluble solids

present in a soil may be an important factor when

considering the suitability of a soil for the foundation of a 

hydraulic structure or for constructing embankments. The
CHAPTER 1—PROPERTIES OF SOILS

25

Figure 1-15.—Criterion for predicting relative density of sand from the penetration

resistance test.
26

Figure 1-16.—Unconfined compressive strength versus penetration resistance, N, for various soils.
CHAPTER 1—PROPERTIES OF SOILS

27

quantity of soluble solids is determined using the procedure

described in USBR 5450. 13 The effect of soluble solids on

an earth structure depends on:

 ̆ Temperature,

 ̆ Minerals present in the soil and their solubility

characteristics in water,

 ̆ Coefficient of permeability and, thus, the amount of

water passing through the soil, 

 ̆ Chemical characteristics of the water, and

 ̆ Other factors.

Therefore, the percentage of soluble solids is only an

indication of possible effects. Soluble solids are more

objectionable in materials having moderate to high

permeability than in soils with low permeability.

The kinds of soluble minerals present in a soil or carried by

groundwater are important when considering the type of

cement to be used in constructing concrete structures in

contact with soil. The aggressive substances which affect

concrete structures are the sulfates of sodium, magnesium,

and calcium. The relative degrees of attack on concrete by

sulfates from soil, groundwater, and other substances are

discussed in Reclamation' s Concrete Manual [27]. Soluble

minerals present in soil and groundwater must be

determined by chemical analyses. The presence of

appreciable quantities of soluble minerals indicates that

engineering properties may change in the presence of

percolating water.

C. Engineering Properties

1-20. General.&In evaluating a soil, the transition

is gradual between those properties that serve only as broad

guides to the character of material and quantitative

properties which define specific performance characteristics.

For example, moisture content and dry density are at times

used as index properties and at other times used as

engineering properties. The importance of the two

properties in investigation and construction control, as

indicators of the nature of material and of the quality of

compaction, has frequently resulted in the belief that low

moisture content and high dry density are the only desirable

characteristics to attain in soils. This is not necessarily true.

These properties are only indexes of the probable

engineering behavior of a soil. Yet, both dry density and

moisture content are so intimately a part of computations

involved in design of structures of soil that they must

frequently be evaluated as engineering properties.

The principal distinction between index and engineering

properties is that the procedures for determining index

properties are relatively simpler than those for determining

engineering properties, which require considerable

knowledge and skill to develop reliable information. This

does not imply index properties tests are simple to perform.

Skill and care are required when performing index tests.

Considerably more special knowledge and skill are required

to interpret and apply index information than are required to

use information from tests for engineering properties. The

13 5450: Determining Water Soluble Solids in Soils.

most commonly listed soil engineering properties are

strength, volume change, and permeability. In addition, but

less clearly defined, are such characteristics as deterioration

and workability for which quantitative evaluation is invalid.

Selecting samples and specimens for both index and

engineering properties testing requires considerable thought

to ensure materials selected for testing are representative of

materials at the structure site. Also, careful sample and

specimen selection are required to obtain maximum

information from the testing program at minimum cost.

1-21. Shear Strength.&

a. General.&Soil has little strength compared to other

materials used for building a structure. Moreover,

compared to maximum soil strength, large variation can

exist in strength, both from soil to soil and within a given

soil type, depending on how it was deposited or placed.

Engineering computations using soil strength deal primarily

with shear strength, the resistance to sliding of one mass of

soil against another, and rarely with compressive or tensile

strengths. In 1776, C.A. Coulomb [28], a French engineer

and scientist, observed that the shear strength of a soil

consisted of two parts: (1) one part dependent on the stress

acting normal to the shear plane, (2) the other part

independent of that stress. The parts were called internal

friction and cohesion, respectively. The factor relating the
EARTH MANUAL

28

s = c  ̄ ) tan 1 1-16

normal component of stress to shear strength was designated

by tan 1 and the unit of cohesion by c. The shear strength,

s, may then be expressed as:

where:

c = unit of cohesion

s = shear strength

) = normal stress on the sliding surface

1 = angle of internal friction

Many soils are either predominantly cohesive or

noncohesive. For either type of soil, engineering

computations can be simplified by dropping the smaller term

in the shear strength equation, and the resulting solution is

conservative. Much of early soil mechanics practice was

based on this simplified assumption. The terms cohesive (1

= 0) and noncohesive or cohesionless (c = 0) soils are still

in common use in referring to these soils.

Occasionally, a structure is so massive or the soil foundation

is so weak that this simplifying assumption cannot be used.

For a large earth embankment dam, this is almost always the

case. In such a situation, determining the values of c and 1

with as much precision as possible is most important for

both the proposed structure and foundation under a variety

of probable loading conditions. It is extremely important

that "undisturbed" samples from the foundation, secured

during investigations, be truly representative of materials

and conditions. Also, material placed in these earth

structures (during construction) should comply with

established design limitations, based on laboratory tests.

b. In Situ Shear Strength.&In situ shear strength

estimates can be derived from:14

 ̆ standard penetration test&USBR 7015

 ̆ vane shear test&USBR 7115

 ̆ cone penetration tests&USBR 7020 and 7021

 ̆ borehole shear device test

Each field test has been used successfully. In situ shear

strength has been estimated for a variety of soils using

appropriate computations and empirical correlations. The

Menard Pressuremeter and the flat blade dilatometer, as

well as various other equipment and methods, have been

used to determine modulus values of soils.

c. Direct Shear.&In the laboratory, shear strength

measurement is accomplished either by using the direct

shear test or the triaxial shear test. The direct shear test,

USBR 5725, 15 was developed first and is still used widely.

It has the advantage of simplicity, but disadvantages include

stress and strain concentrations within the specimen, and

pore-water pressures cannot be monitored during the test.

Usually, the specimen is tested under consolidated-drained

conditions. The specimen is allowed to fully consolidate

under each applied normal pressure and is sheared at a rate

slow enough to allow pore pressures to remain at

equilibrium during shear. Therefore, test results are

reported in terms of effective stress.

d. Triaxial Shear.&The triaxial shear test apparatus

was developed to permit control of other factors that

influence shear strength, which cannot be evaluated with the

direct shear test apparatus. Originally used as a research

tool, the triaxial device was instrumental in better

understanding the mechanics of shear in soils. Because of

its capability to simulate a wide range of test conditions, the

triaxial shear apparatus is now used for routine testing. The

triaxial shear apparatus is used to perform four different test

procedures. 16 The procedure used to test a soil must be

based on field loading and drainage conditions to which the

soil will be subjected. Figure 1-17 indicates the relation

between relative density and the angle of internal friction, 1

(also expressed as tan 1), for compacted coarse-grained

soils [24, 29].

e. Pore-Water Pressure.&Shear strength is primarily

dependent on effective normal stress. Under an externally

applied stress, soil grains are forced into more intimate

contact, and the soil mass volume decreases. Because soil

grain volume cannot be changed appreciably, this volume

change must take place primarily in the soil voids or pores.

If these pores are completely filled with water, their volume

14 7015: Performing Penetration Resistance Testing and Sampling

of Soils.

7020: Performing Cone Penetration Testing of Soils - Mechanical

Method.

7021: Performing Cone Penetration Testing of Soils - Electrical

Method.

7115: Performing Field Vane Shear Testing.

15 5725: Performing Direct Shear Testing of Soils. 16 5740: Determining Lateral Earth Pressure (ko) by the Triaxial Test

Method.

5745: Performing Unconsolidated-Undrained Triaxial Shear Testing

of Soils.

5750: Performing Consolidated-Undrained Triaxial Shear Testing of

Soils.

5755: Performing Consolidated-Drained Triaxial Shear Testing of

Soils.
CHAPTER 1—PROPERTIES OF SOILS

29

Figure 1-17.—Effect of relative density on the coefficient of friction, tan 1,

for coarse-grained soils [24, 28].

cannot be changed unless some water is drained from the

soil mass, because water is considered incompressible. If

drainage is prevented or impeded, stress will develop in the

pore water opposing the externally applied stress. The

developed stress is called excess pore-water pressure (i.e.,

pore-water pressure in excess of hydrostatic conditions).

Even if the pores are filled only partially with water,

pressures in the fluid combination of air and water will

develop to a lesser degree, because volume change is

possible (air is compressible), and additional stresses can be

carried by the soil grains. However, a difference will exist

between pore-air pressure and pore-water pressure resulting

from capillary tension or capillary stress of the water films.

Therefore, when analyzing shear strength of unsaturated
EARTH MANUAL

30

s = c1  ̄ ()  ̃ u) tan 11 1-17

soils, consideration must be given to whether pore-air or

pore-water pressure is used. Because pore pressures are

opposed to the normal stress, total normal stress will be

reduced whenever positive pore-water pressure is present.

Based on this observation, the general case Coulomb

equation must be rewritten:

where:

s = shear strength

u = pore fluid pressure

c1 = effective cohesion

) = normal stress on the sliding surface

11 = effective angle of internal friction

The analysis can be made considering u as either pore-air

pressure or pore-water pressure, depending on the

application. Figure 1-18 shows the effect of pore fluid

pressure on the shear characteristics of a lean clay. True

strength characteristics of a soil are determined only when

pore fluid pressures are accounted for during laboratory

testing.

f. Capillary Stress.&When the water in a soil does not

completely fill the voids, a surface develops between the

water and air. This surface is not flat, but is curved due to

surface tension. The degree of curvature depends on:

 ̆ size of the void, 

 ̆ nature of the material forming the sides of the void,

and 

 ̆ kind of liquid in the voids.

Because the surface is curved, it is stressed in tension; this

tensile stress is imparted to the liquid in the pores. The

effect of tensile stress is to pull the soil particles together.

The action is contrary to pore-water pressure as described

in the previous paragraphs, and it can influence the value of

cohesion determined by laboratory tests.

Capillary stress is present when soil is not completely

saturated and may have a significant influence on results of

laboratory tests. The presence of capillary stress results in

a higher shear strength for a soil than will exist when

capillary stress is lessened or eliminated by wetting or

saturation.

Laboratory test methods for measuring capillary stress are

described in USBR 5735. 17 With information from the

capillary test, a triaxial shear test can be analyzed either on

the basis of pore-air pressure, which will indicate the shear

strength when it is influenced by capillary stress, or on the

basis of pore-water pressure, which does not include the

influence of capillary stress and which can represent the

condition of saturation.

g. Sliding Resistance.&A special type of shear

strength investigation involves the shear strength between

dissimilar materials, commonly between soil and concrete or

between soil and geosynthetic materials. Usually, this type

of shear is identified as sliding resistance or interface

friction. The nature of the problem makes it necessary to

investigate this case by direct shear test methods.

h. Residual Shear Strength.&Some soils exhibit

brittle stress-strain behavior during shear. Materials such as

shale, indurated clay, overconsolidated clay, or stiff fissured

clay reach maximum shear stress after extremely small shear

displacements. Studies indicate measured shear stress in

these materials decreases rapidly with increasing shear strain

beyond the point of maximum shear stress. Continued

displacement beyond maximum shear stress will reduce the

measured shear stress to a low constant value termed the

"residual shear stress" [30] (fig. 1-19). Residual shear

strength can be evaluated using either USBR 5726 or USBR

5730. 18

1-22. Volume Change.&

a. General.&Volume change in a soil mass caused by

both natural and artificial conditions introduces problems

peculiar to soils and not encountered with other construction

materials. Volume decrease is caused by pressure increase

and is a function of time and permeability; it is associated

with changes in moisture and air content, and it can occur

as a result of compaction. Volume increase is a function of:

 ̆ pressure, 

 ̆ density, 

 ̆ moisture content, and 

 ̆ soil type.

Terms that describe volume change phenomena are:

 ̆ Compression&Volume change as a result of elastic

deformation or expulsion of air produced by

application of a static external pressure.

17 5735: Determining Initial Capillary Pressure of Soils.

18 5726: Performing Repeated Direct Shear Testing of Soils.

5730: Performing Rotational Shear Testing of Soils.
CHAPTER 1—PROPERTIES OF SOILS

31

Figure 1-18.—Results of a consolidated-undrained (CIU) triaxial shear test on lean clay with and

without considering pore pressure.
32

Figure 1-19.—Peak and residual shear strength and resultant angles of internal friction [29].
CHAPTER 1—PROPERTIES OF SOILS

33

 ̆ Consolidation&Volume change produced by

application of static external pressure and achieved

through pore-water movement with time.

 ̆ Shrinkage&Volume change produced by capillary

stresses during drying of a soil.

 ̆ Compaction&Volume change produced by

mechanical manipulation such as rolling, tamping,

or vibrating.

The above terms apply to volume reduction. Corresponding

terms apply to volume increase:

 ̆ Rebound as opposed to compression.

 ̆ Expansion as opposed to consolidation.

 ̆ Swell as opposed to shrinkage.

 ̆ Loosening or scarifying describes the operation

opposite of compaction.

Ground surface movement is often the result of volume

change in the underlying soil. Terms describing ground

surface movement are:

 ̆ Settlement&Ground surface movement associated

with volume decrease.

 ̆ Heave&Ground surface movement associated with

volume increase.

Most often, volume change is associated with changes in

volume of the voids and only to a limited extent with

changes in volume of solid particles. If voids are, to a large

extent, filled with air, an increase in pressure on the soil

mass will result in compression without appreciable

subsequent consolidation. Conversely, if voids are nearly

or completely filled with water, little or no compression will

take place immediately upon application of a pressure

increment; and only when water drains from the soil mass

can consolidation occur. If water can drain readily from the

soil mass, consolidation may take place within a short

period of time; but, if the soil has a low permeability, if the

soil mass is extremely large, or if drainage is otherwise

impeded, complete consolidation may require many years.

Volume change also is caused by particle rearrangement,

particle breakdown, and physical or chemical absorption of

moisture. Usually, particle rearrangement is associated with

clay soils deposited underwater that have been stressed only

with the weight of soil above them. Particle breakdown is

most commonly found where residual soil is derived from

rock that has been weathered and altered in place. Most

clay soils have affinity for moisture which can be removed

only with considerable effort. Fortunately, many of the clay

minerals attain a state of saturation without great volume

change; but a few (e.g., montmorillonite) will absorb or

release large volumes of water and experience large

shrinkage and swell.

b. Control of Compressibility.&By far, the most

frequently occurring problem the geotechnical engineer must

deal with involves compressibility. Some spectacular

failures have occurred because of compressibility, but the

most commonly observed effect is the cracking of

structures. Shear strength is affected indirectly because the

greater the soil' s compressibility, the greater the potential

for high pore pressures. Figure 1-20 shows the variation of

compressibility with soil type for compacted earth

embankments [31].

Although the potential for high compressibility is usually

associated with fine-grained, highly plastic soils, a number

of procedures have been developed to treat soil to minimize

compressibility. In constructed fills, for most soil types,

sufficient compaction can be applied to limit compression to

a few percent. Where it can be applied, moisture control

tends to reduce future consolidation by facilitating

compaction. For some soils compacted dry of optimum

moisture content, the soil grain structure will not assume its

densest state as discernible from compaction curves shown

on figure 1-10c. For such a condition, subsequent wetting

may result in particle rearrangement and an accompanying

volume strain called saturation collapse. This action can

occur rapidly in some silty type soils.

Soils subject to shrinkage and swell can be used in earth

structures if compacted under good moisture control and

loaded sufficiently with other materials to prevent swelling.

When swelling-type soils are used for the majority of an

embankment, flatter slopes and greater soil volumes are

required than for nonswelling soils. This may require more

stringent zoning of an embankment, and consideration must

be given to acquiring better materials from more distant

sources as opposed to using swelling-type soils found

locally.

Compressibility in a soil foundation is difficult to control.

Removing compressible soil, using piles or piers, and use of

spread footings or mats has been applied in specific cases

with success. Variation in compressibility within the

construction area can produce greater difficulty than the

amount of compressibility encountered. Under earth dams,

removal of questionable materials, drainage of wet soils,

wetting of dry soils, and spread embankments have all been

used to minimize compressibility. Compressible

foundations under proposed buildings and similar structures
34

Figure 1-20.—Compression characteristics of various compacted embankment soils based on field measurem
CHAPTER 1—PROPERTIES OF SOILS

35

are frequently improved by removing an amount of soil

equal to the structure' s weight so there is no net increase in

stress in the natural soil after the structure is built.

c. Pressure-Compression Characteristics.&When

soils are gradually deposited layer upon layer, each layer is

compressed by the layers above it; and, as time passes, the

soil attains a state of consolidation in equilibrium with the

superimposed pressure. Such a soil is described as normally

consolidated. In such a soil, the density increases with

depth or overburden pressure, and the void ratio decreases

correspondingly. This relationship is nearly a straight line

(virgin compression line) when plotted on a semilogarithmic

scale (fig. 1-21 [32]). If all or a portion of the

superimposed pressure is removed, rebound will occur, but

the change in void ratio usually will be small compared to

the void ratio change produced by initial compression and

consolidation. Such a soil is overconsolidated. If an

overconsolidated soil is again loaded, the change in void

ratio will be small compared to that produced with similar

pressure increments during initial consolidation. The final

void ratio, however, will be somewhat smaller than that

originally obtained. Where such a condition exists, either

as a result of a glacier having overridden the deposit&where

extensive erosion has occurred&or where desiccation has

occurred, these materials often can function as a foundation

without difficulty.

In the arid and semiarid parts of the Western United States,

unsaturated deposits of loose silt (ML), silty clay (CL-ML),

or lean clay (CL) have caused special problems [33]. These

deposits include wind-deposited loess and loess-like soils

and colluvial and alluvial soils deposited by flash flood

runoffs, often in the form of mudslides. In these deposits,

soils have never been completely wetted to allow breakdown

of the loose depositional structure. Generally, these soils

have relatively high dry strength created by well dispersed

clay binder [34]. It is known that loessial soils form high,

near-vertical faces that are stable as long as the moisture

content is low (fig. 1-22). However, upon wetting, strength

is essentially lost and slope failures occur. Similarly,

loessial soils support heavy structural loads on footings or

piles when dry but lose their bearing capacity and resistance

to compression when their loose structure collapses upon

wetting (fig. 1-23 [35]). Certain interfan soil deposits

adjacent to the southwestern foothills of the Central Valley

of California as well as other areas in the Western United

States with similarly formed deposits have similar

characteristics. When dealing with hydraulic engineering

works, where subsoils eventually will become saturated,

recognizing such soil deposits is important so that measures

can be taken to improve them before building structures

upon them.

Methods have been designed to identify these metastable

soils [36]. Certain relationships exist between in-place dry

density, moisture content, and the volume change that may

be anticipated for fine-grained soils. The relationship in

which dry density is expressed as the ratio of in-place dry

density to laboratory maximum dry density for various

moisture contents, presented in relation to optimum moisture

content, is shown on figure 1-24a ([37]). If the dry density

ratio and moisture content difference of a soil plot above

and to the left of the limit line (shown on fig. 1-24a), very

small additional volume change will occur upon wetting, and

treatment of in-place material is not normally required for

small dams, canal embankments, or lightweight structures.

If the dry density ratio and moisture content difference plot

below and to the right of the limit line, significant volume

change may occur on wetting of the in-place material even

under low pressures; and treatment of in-place materials

may be required. Rigid structures should not be placed on

either wet loose soils or dry loose soils, subject to later

wetting, as structure cracking may occur. Foundation

treatment may be required for rigid structures whose

foundation soil properties plot above the limit line.

Another criterion for predicting loose, fine-grained soils

needing treatment involves in-place dry density and liquid

limit as shown on figures 1-24b and 1-25 (from [37]). The

theory is simple: if in-place dry density is so low that the

volume of voids is larger than that required to hold the

volume of water needed to reach the liquid limit (as shown

for case I), the soil can become saturated. Consistency is

low, and the void space is sufficient to allow collapse.

Conversely, if in-place dry density is high enough so that

the volume of voids is less than that required to hold the

volume of water needed to reach the liquid limit (as shown

for case III), the soil will not collapse upon saturation but

will reach a plastic state in which particle-to-particle contact

always will take place. Therefore, soils with liquid limits

and in-place dry densities that plot above the line show a

critical dry density condition, while soils that plot below the

line do not. In the latter condition, soils would only settle

in a normal manner due to a pressure increase. The graph

has additional usefulness in presenting data so the quality of

denseness of soils in the case III category can be evaluated.

For example, dry densities and liquid limits plotted close to

the case II line may not be susceptible to collapse, but may

be critical with respect to pressure increases; whereas soils

with conditions plotted lower in the case III area would

result in more firm material. In the case of expansive soils,

with high liquid limits and very high in-place dry densities,

plotting very low on the graph indicates susceptibility to

future expansion. Therefore, in case III, a moderate range

of dry densities exists that is most desirable.
EARTH MANUAL

36

Figure 1-21.—Void ratio-pressure curve, compression index, and preconsolidation pressure [31].
CHAPTER 1—PROPERTIES OF SOILS

37

Figure 1-22.—A 34-foot cut on 1/2:1 slope in loess formation—

Franklin Canal, Nebraska.

Loessial soils in Kansas and Nebraska are quite uniform and

have liquid limits between 30 and 40 percent. Therefore,

in-place dry density and moisture content versus settlement

upon wetting can be expressed in terms of in-place dry

density and moisture content for these localities. Soils from

other areas must be tested.

For loessial soils in Kansas and Nebraska:

 ̆ Loess with dry density less than 1,281 kg/m3

(80 lb/ft3) is considered loose and highly susceptible

to settlement on wetting with little or no surface

loading.

 ̆ Loess with dry density between 1,281 and

1,442 kg/m3

 (80 and 90 lb/ft3) is medium dense and

is moderately susceptible to settlement on wetting

when loaded.

 ̆ Loess with dry density above 1,442 kg/m3

 (90 lb/ft3)

is quite dense and capable of supporting ordinary

structures without serious settlement, even upon

wetting.

 ̆ For earth dams and high canal embankments, a dry

density of 1,362 kg/m3

 (85 lb/ft3) has been used as

the division between high, dry density loess

requiring no foundation treatment and low, dry

density loess requiring treatment. However,

considerable compression may still occur, and

defensive design techniques such as wide filters and

drains may be required in the embankment.

 ̆ Generally, moisture contents above 20 percent will

permit full settlement under load.

Where volume change is a potential problem, a foundation

investigation must provide information not only as to soil

types found, but also information on their present

undisturbed state. Samples must be recovered in an

"undisturbed" state using methods described in either USBR

7100 or 7105. 19

19 7100: Obtaining Undisturbed Block Samples by the Hand and

Chain Saw Methods.

7105: Performing Undisturbed Soil Sampling by Mechanical Drilling

Methods.

5600: Determining Permeability and Settlement of Soils 18-in (203-

mm) Diameter Cylinder.

5605: Determining Permeability and Settlement of Soils Containing

Gravel.

5610: Determing Permeability of Soil by the Back-Pressure Test

Method.

5700: Determining the One-Dimensional Consolidation Properties of

Soils (Incremental Stress).

5705: Determining the One-Dimensional Expansion Properties of

Soils.

5715: Determining the One-Dimensional Uplift Properties of Soils.
38

Figure 1-23.—Effect of loading and wetting high and low unit weight loess soil foundations [34].
39

Figure 1-24.—Criterion for treatment of relatively dry fine-grained foundations.
40

Figure 1-25.—Assessing collapse potential of various soils using dry density and liquid limit [36].
CHAPTER 1—PROPERTIES OF SOILS

41

Laboratory consolidation testing of undisturbed or

compacted soil specimens is performed using USBR 5700.

Permeability and settlement of compacted soil specimens

may be determined using USBR 5600, 5605, or 5610.

Other volume change characteristics of soils (e.g.,

expansion, swell, or heave) may be determined using USBR

5705 or 5715. Three-dimensional volume change

characteristics of soils may be obtained using consolidation

procedures given for triaxial shear tests (see USBR 5750 or

5755). Figure 1-21 shows the type of compression results

obtained from testing cohesive soil. Figure 1-26 shows the

relation of relative density and void ratio to compressibility

for a compacted, fine sand [38].

d. Pressure-Expansion Characteristics.&In addition

to the normal rebound phenomenon, which occurs upon

release of a compressive pressure as indicated on

figure 1-21, certain types of clayey soils and clay shales

exhibit expansive characteristics in the presence of water.

The amount of expansion depends on the type of clay

mineral, confining pressure, and the availability of water;

expansion is a function of: 

 ̆ time, 

 ̆ confining pressure, 

 ̆ initial density, and 

 ̆ initial moisture content.

Clays containing montmorillonite are the chief sources of

difficulty. Since hydraulic structures always provide a

water source for soil expansion, clays must be identified and

treated to avoid future failures. Figure 1-27 shows a

comparison between pressure and expansion for two typical

expansive clays [39, 40]. Figure 1-28 shows effects of

placement moisture content and dry density on expansion

characteristics for a typical compacted expansive clay.

Graph (a) shows volume change under a pressure of 7 kPa

(1 lbf/in2

), and graph (b) shows total uplift pressure

developed when this clay was restrained from expanding

[41]. Figures 1-29 and 1-30 show canal lining failures

caused by heaving of expansive soils. Table 1-2 gives

criteria for identifying expansive clay [42].

An expansive clay can be modified by adding a small

percentage of hydrated lime to the soil. Adding lime to soil

has two major effects: (1) improves the workability and

(2) increases the shear strength.

The first effect is immediate and results from the following

reactions of lime with soil:

 ̆ Soil plasticity is immediately reduced (fig. 1-31).

The liquid limit (LL) of the soil changes very little

while the plastic limit (PL) increases, thus reducing

the plasticity index (PI) of the soil.

 ̆ The finer clay size particles (colloids) agglomerate to

form larger particles.

 ̆ The large particles (clay clods) disintegrate to form

smaller particles.

 ̆ A drying effect takes place caused by absorption of

moisture for hydration of the lime, which reduces the

moisture content of the soil.

The result of these reactions is to make the material more

workable and more friable.

The second effect of adding lime to soil is a definite

cementing action with strength of the compacted soil-lime

mixture increasing with time. The lime reacts chemically

with available silica and some alumina in the soil to form

calcium silicates and aluminates.

The percentage of lime added to a soil depends on whether

the purpose is for modification (small percent to increase

workability) or for stabilization (sufficient lime to provide

strength). For stabilization, lime percentage can be based

on: 

 ̆ soil pH, 

 ̆ plasticity index reduction, 

 ̆ strength gain, and 

 ̆ prevention of harmful volumetric change.

When the soil-lime mixture reaches a pH of 12.4, sufficient

lime has been added to react with all the soil. An optimum

lime percentage exists beyond which addition of more lime

slightly reduces the plasticity index of the mixture but

cannot be economically justified. If a minimum strength

material is needed, enough lime can be added to obtain that

strength, or enough lime can be added to increase the

shrinkage limit to placement moisture or higher to prevent

excessive volume change through wetting and drying

cycles [43].

1-23. Permeability.&

a. Definition.&Voids in a soil mass provide not only

the mechanism for volume change, but also passages for

water to move through a soil mass. Such passages are

variable in size, and the flow paths are tortuous and

interconnected. If a sufficiently large number of such paths

act together, an average rate of flow through a soil mass can
EARTH MANUAL

42

Figure 1-26.—Compressibility characteristics of a fine sand in relation to

placement relative density [37].

k = Q

A

L

Ùh = vi 1-18

be determined under controlled conditions that will be

representative of larger masses of the same soil under

similar conditions.

Under gravitational forces, water movement through soil is

called percolation or seepage. The measure of this

movement is called permeability; the factor relating

permeability to unit conditions is the coefficient of

permeability, k, defined as:

where:

A = gross cross-sectional area through which 

Q flows

Ùh = head loss

i = hydraulic gradient, equal to Ùh /L, or the ratio

of head lost to distance over which the head is

lost

k = coefficient of permeability

L = distance over which head is lost

Q = volume of water per unit time

V = discharge velocity

This equation is commonly known as Darcy' s law.

Temperature and viscosity of water affect the coefficient of

permeability; these factors are usually accounted for in

permeability determinations by correcting test results to a

standard temperature of 20 (C.

Many units of measure are used to express the coefficient of

permeability. In the past, Reclamation preferred to use feet

per year (ft/yr), which is the same as cubic feet per square

foot per year ([ft3

/ft2]/yr) at unit gradient. Feet per day

(ft/d) is a term used to some extent in canal design, while 

water-supply engineers favor gallons per square foot per day

([gal/ft2

]/day). Most technical literature uses centimeters

per second (cm/s) (fig. 1-32), and Reclamation will be

converting to these units.

b. Ranges of Permeability.&The coefficient of

permeability in natural soil deposits is highly variable. In

many soil deposits, permeability parallel to bedding planes

may be 100 or even 1,000 times larger than permeability
43

Figure 1-27.—Pressure-expansion curves for two typical expansive clays [38, 39].
44

Figure 1-28.—Typical expansive clay. Effects of placement moisture content and dry unit weight on

expansion characteristics [40].
CHAPTER 1—PROPERTIES OF SOILS

45

Figure 1-29.—Slope failure and bottom heaving of

Friant-Kern Canal, California.

Figure 1-30.—Heaving of canal bottom (about 300 mm at center),

Mohawk Canal, Arizona.
EARTH MANUAL

46

Table 1-2.—Relation of soil index properties to expansion potential of high-plasticity clay soils.

 Data for making estimate of probable volume change for expansive materials

Data from index tests1

Probable expansion2, percent

total volume change, dry to

saturated condition

Degree

of

expansion

Colloid content,

percent minus

0.001 mm

Plasticity index, PI,

%

Shrinkage

limit, SL, %

 > 28 > 35 < 11 > 30 Very high

 20 to 31 25 to 41 7 to 12 20 to 30 High

 13 to 23 15 to 28 10 to 16 10 to 20 Medium

 < 15 < 18 > 15 < 10 Low

 1

 All three index tests should be considered in estimating expansive properties.

 2

 Based on a vertical loading of 7 kPa (1.0 lbf/in2)

perpendicular to bedding planes. An exception to this is

loess in which vertical permeability is several times greater

than horizontal permeability [44]. Permeability of some

soils is sensitive to small changes in density, moisture

content, or gradation. In certain permeability ranges, a few

percent variation in any one of these factors may result in a

1,000-percent variation in permeability. Because of possible

wide variation in permeability, measurement with great

accuracy is not possible for most design work; rather, the

order of magnitude of permeability is important.

Reclamation describes soils with permeability less than

1× 10-6cm/s (1 ft/yr) as impervious, those with permeability

between 1x10-6 cm/s and 1x10-4 cm/s (1 and 100 ft/yr)

as semipervious, and soils with permeability greater than 

 1× 10-4 cm/s (100 ft/yr) as pervious. Figure 1-32 shows

a compilation of some of the permeability testing performed

at the Reclamation soils laboratory (Denver, Colorado) on

compacted specimens of various soils. Figure 1-33 shows

results of permeability tests on relatively clean, sand-gravel

mixtures [45].

c. Control of Permeability.&The determination of

coefficient of permeability is important in water retention

and water conveyance structures because water lost through

the soil is an economic loss charged to the structure.

Continuous movement of water through the soil of a

structure may result in removal of soluble solids or may

result in internal erosion called piping. Piping must

particularly be guarded against because it occurs gradually

and is often not apparent until the structure' s failure is

imminent. In nonhydraulic structures, permeability is

important only when work below water table is required or

when changes in water table occur in the area influenced by

constructing the structure.

Seepage control is accomplished in a variety of ways that

may be divided into three classes: (1) reducing the

coefficient of permeability, (2) reducing the hydraulic

gradient, and (3) controlling the effluent.

In embankments, permeability is reduced by selection of

material through compaction control and on rare occasions

by use of additives. Through foundations, seepage is

reduced by several types of cutoffs formed by injection of

a material into the foundation by grouting methods and

densification by dynamic compaction, vibration, and loading

often accompanied by changing the moisture content of the

materials to hasten or enhance densification.

Hydraulic gradient reduction is accomplished either by

reducing the head or increasing the length of the seepage

path. Usually, some type of low permeability reservoir

blanket is constructed to increase the seepage path.

Control of effluent requires a design that reduces seepage

pressures sufficiently at all points so rupture of impervious

zones or foundation layers is prevented and that provides

filters to prevent piping. This is accomplished by zoning in

earth dams and canal banks, using filters and drains, and

installing drains and pressure relief wells. A number of

combination control methods are in common use including

wide embankment sections, impervious diaphragms, and

linings. The control method selected depends primarily on

cost of treatment compared to benefit received both in

preventing water loss and in assurance against piping

failure.

Detailed analysis and design techniques are presented in

Design Standards No. 13&Embankment Dams ([46] chs. 2,

5, 8, 17).
CHAPTER 1—PROPERTIES OF SOILS

47

Figure 1-31.—Effect of lime on shrinkage limit, plastic limit, and liquid limit.

d. Determination of Coefficient of

Permeability.&Permeability is determined in the field by

means of a variety of tests based either on forcing water

through the material or removing water under controlled

conditions. USBR 7300, 7305, and 7310 describe field

methods for determining in situ permeability. USBR 5600,

5605, 5610, and 5615 are methods for determining

permeability in the laboratory. 20 There are ranges of

permeability for which none of these tests may be

satisfactory. However, this happens so rarely that

procedures have not been established for these special

conditions. For groundwater studies, large scale aquifer

testing may be necessary (see Ground Water Manual [47]).

1-24. Engineering Characteristics of Soil

Groups.&Although substitutes for thorough testing have

not been devised to determine the important engineering

properties of specific soils, approximate average values for

compacted specimens of typical soils from each USCS

group are available based on statistical analyses of available

data (table 1-3). The attempt to determine soil data from

average values involves risks: (1) the data may not be

representative and (2) the values may be used in design

without adequate safety factors. In the early stages of

project planning, when different borrow areas and design

sections are being studied, these average values of soil

properties can be used as qualitative guides. Because the

values pertain to the soil groups, proper soil classification is

of vital importance. Verification of field identification by

laboratory gradation and Atterberg limits tests must be made

on representative samples of each soil group encountered.

20 7300: Performing Field Permeability Testing by the Well

Permeameter Method.

7305: Field Permeability Test (Shallow-Well Permeameter Method).

7310: Constant Head Hydraulic Conductivity Tests in Single Drill

Holes.

5600: Determining Permeability and Settlement of Soils [8-in (203-

mm) Diameter Cylinder].

5605: Determining Permeability and Settlement of Soils Containing

Gravel.

5610: Determining Permeability of Soil by the Back-Pressure Test

Method.

5615: Performing Radial Vacuum Permeability Test for Soil-Cement

or Porpous Rock.
48

Figure 1-32.—Permeability ranges for soils.
CHAPTER 1—PROPERTIES OF SOILS

49

Figure 1-33.—Relationship of permeability to gravel content for specimens of various relative densities.

Table 1-3 is a summary of values obtained from more than

1,110 soil tests performed between 1960 and 1985 in

Reclamation' s Denver geotechnical laboratory. The data

were obtained from reports on soil samples for which

laboratory classifications were available and are arranged

according to the USCS groups. The soils are from the

17 Western United States.

For each soil property noted in table 1-3, the average,

minimum, and maximum test values; standard deviation;

and number of tests performed are listed. Because all

laboratory tests (except large-size permeability tests) were

made on compacted specimens of the minus 4.75-mm (No.

4) soil fraction, data on average values for gravels were not

available for most properties. The averages shown are

subject to uncertainties that may arise from sampling

variation and tend to vary widely.

The values for laboratory maximum dry density, optimum

moisture content, specific gravity, and maximum and

minimum index densities were obtained using the previously

referenced test procedures. The MH and CH soil groups

have no upper boundary of liquid limit in the classification

system; therefore, the range of those soils is included in the

table. The maximum liquid limits for the MH and CH soils

tested were 82 and 86 percent, respectively. Soils with

higher liquid limits than these have inferior engineering

properties.

Two shear strength parameters are given for the soil groups

under the heading c 1 and 1 1. The values of c 1 and 1 1 are

the vertical intercept and the angle, respectively, of the

Mohr strength envelope on an effective stress basis as

shown on figure 1-18. The Mohr strength envelope is

obtained by testing several specimens of compacted soil in

a triaxial shear apparatus in which pore-fluid pressures

developed during the test are measured. Effective stresses

are obtained by subtracting measured pore-fluid pressures in

the specimen from stresses applied by the apparatus. Data

used in compiling the values in table 1-3 were taken from

unconsolidated-undrained (UU) and consolidated-undrained

(CU) triaxial shear tests with pore-fluid pressure

measurements and from consolidated- drained (CD) triaxial

shear tests (see USBR 5745, 5750, and 5755).

a. Engineering Use Chart.&The Engineering Use

Chart, table 1-4, shows the type of soil most appropriate for

certain kinds of earthwork construction. The various soil

groupings in the USCS generally relate to engineering

properties typical for each soil group. These relationships
EARTH MANUAL

50

Table 1-3.—Average engineering properties of compacted soils from the 17 Western United States. Data from reports published between June 1960 and December 1985.

Data from 2005 tests on 1110 samples. Table compiled January 1988

Compaction Shear Strength

Specific gravity Laboratory Index density Consolidated-drained and consolidatedundrained triaxial shear tests

Unconsolidated-undrained triaxial shear

tests

Total 

No. of

samples

tested

Optimum

moisture

content

%

Av. placement

conditions Effective stress Av. placementconditions Effective stress

USCS

soil

type

No. 4

minus

No. 4

plus

Max. dry

density

kg/m3

Max.

kg/m3

Min.

kg/m3

Dry

density

kg/m3

Moisture

content

%

Friction

angle

degrees

Cohesion

kPa

Dry

density

kg/m3

Moisture

content

%

Friction

angle

degrees

Cohesion

kPa

Values

listed

GW 22

2.69

0.03

2.63

2.75

2.58

0.08

2.39

2.67

1989

51

1907

2042

11.4

1.2

9.9

13.3

2167

139

1810

2332

1746

128

1417

1896

Average

Std. dev.

Minimum

Maximum

17 10 5 20 # of tests

GP 62

2.68

0.04

2.54

2.77

2.52

0.21

1.76

2.65

1907

153

1436

2045

12.2

4.3

9.1

26.5

2212

113

1826

2383

1808

124

1375

1986

1933

238

1489

2144

7.5

4.1

3.3

15.1

42.2

2.1

38.0

43.8

8.1

16.3

0.0

40.7

Average

Std. dev.

Minimum

Maximum

37 15 16 50 5 # of tests

GM 37

2.73

0.07

2.65

2.92

2.43

0.18

2.19

2.92

1819

189

1393

2130

15.7

5.9

5.8

29.5

Average

Std. dev.

Minimum

Maximum

35 17 35 # of tests

GC 32

2.73

0.09

2.67

3.11

2.50

0.15

2.38

2.78

1854

126

1537

2066

14.2

3.9

6.0

23.6

Average

Std. dev.

Minimum

Maximum

30 5 32 # of tests

SW 20

2.67

0.03

2.64

2.72

2.57

0.03

2.54

2.59

2019

96

1896

2162

9.1

1.7

7.4

11.2

1987

128

1683

2207

1576

142

1278

1758

Average

Std. dev.

Minimum

Maximum

13 2 4 13 # of tests

SP 81

2.66

0.04

2.60

2.86

2.62

0.08

2.52

2.75

1827

160

1649

2159

10.5

2.1

7.8

13.4

1890

120

1621

2199

1542

144

1252

1960

Average

Std. dev.

Minimum

Maximum

50 5 8 43 # of tests

SM 174

2.68

0.06

2.51

3.11

2.50

0.12

2.24

2.69

1877

140

1488

2114

12.3

3.3

6.8

25.5

1803

147

1417

1968

1379

136

1034

1555

1760

145

1459

2019

13.2

5.2

4.6

23.0

34.0

4.9

23.7

40.7

20.7

25.5

0.0

90.3

1821

201

1488

2122

12.6

5.5

7.6

25.0

33.5

6.1

23.3

45.0

59.3

42.1

0.0

146.2

Average

Std. dev.

Minimum

Maximum

162 10 133 20 10 8 # of tests

SC 112

2.69

0.04

2.56

2.84

2.47

0.18

2.17

2.59

1906

99

1547

2109

12.4

2.4

6.7

22.1

1773

225

1459

2111

15.4

5.2

7.5

22.7

32.7

3.8

25.5

38.3

19.3

14.5

0.0

42.1

1967

88

1843

2035

11.1

2.1

9.7

14.0

35.1

0.7

34.2

35.8

53.8

4.1

49.0

58.6

Average

Std. dev.

Minimum

Maximum

110 4 90 11 3 # of tests

ML 63

2.70

0.09

2.52

3.10

1645

168

1355

2018

20.1

5.7

10.6

34.6

1528

179

1292

1778

25.2

9.5

13.5

40.3

35.2

2.5

31.4

38.3

4.8

3.4

0.0

10.3

1678

161

1512

1909

17.4

5.7

11.1

25.8

31.8

4.3

25.2

37.2

61.4

24.1

21.4

82.0

Average

Std. dev.

Minimum

Maximum

60 36 11 4 # of tests

MH 11

2.79

0.27

2.47

3.50

1372

35

1327

1425

33.1

1.5

31.5

35.5

Average

Std. dev.

Minimum

Maximum

9 4 # of tests

CL 395

2.70

0.05

2.56

2.87

2.48

0.13

2.34

2.75

1768

97

1398

2002

16.4

3.1

10.7

30.9

1665

174

1297

1922

18.3

5.7

10.2

35.0

28.1

5.0

10.8

36.8

15.2

18.6

0.0

104.1

1760

86

1622

1986

15.3

2.4

11.6

20.2

24.4

7.0

8.0

33.8

91.0

49.0

0.0

164.1

Average

Std. dev.

Minimum

Maximum

361 8 286 31 24 # of tests

CH 101

2.73

0.06

2.51

2.89

1531

102

1318

1720

24.8

5.2

16.6

41.8

1406

107

1249

1555

30.6

5.7

22.4

42.0

20.5

6.3

10.8

30.9

32.4

31.0

0.0

108.2

1574

92

1438

1680

22.7

4.6

17.9

29.1

15.1

6.7

5.1

26.1

124.1

25.5

85.5

148.2

Average

Std. dev.

Minimum

Maximum

93 36 11 5 # of tests

Conversion factors: 1 kg/m3

 = 0.06243 lb/ft3; 1 kPa = 0.145 lb/in2
CHAPTER 1—PROPERTIES OF SOILS

51

Table 1-4.—Engineering use chart for compacted soils

Engineering Properties of Compacted Soil1 Relative Desirability for Various Uses (No. 1 is considered the best)

Rolled earth dams Canal sections Foundations and fills

Soil group name

Group

symbol

Permeability2 Shear strength (saturated) Compressibility (saturated)

Workability asa construction

material

Homogeneous

embankment Core Shell

Erosionresistant

blanket or belt

Compacted earth

lining

Impervious Per- vious

Resistance

to frost

heave

Well-gradedgravel

GW Pervious Excellent Negligible Excellent — — 1 1 — — 1 1

Poorly gradedgravel

GP Pervious Good Negligible Good — — 2 2 — — 3 2

Silty gravel

GM Semipervious

to impervious

Good Negligible Good 2 4 — 4 4 1 4 6

Clayey gravel GC Impervious Good to fair Very low Good 1 1 — 3 1 2 6 5Well-gradedsands

SW Pervious Excellent Negligible Excellent — — 3 if gravelly 6 — — 2 3

Poorly gradedsands

SP Pervious Good Very low Fair — — 4 if gravelly 7 if gravelly — — 5 4

Silty sands SM Semipervious

to impervious

Good Low Fair 4 5 — 8 if gravelly 5 erosion critical 3 7 12

Clayey sands SC Impervious Good to fair Low to medium Good 3 2 — 5 2 4 8 7Silt ML Semipervious

to impervious

Fair Medium Fair 6 6 — — 6 erosion critical 6 9 11

Lean clay CL Impervious Fair Medium Good to fair 5 3 — 9 3 5 10 9Organic silt andorganic clay

OL Semipervious

to impervious

Poor Medium to high Fair 8 8 — — — 7 11 —

Elastic silt MH Semipervious

to impervious

Fair to poor High Poor 9 9 — — — 8 12 10

Fat clay CH Impervious Poor High Poor 7 7 — 10 — 9 13 8Organic silt andorganic clay

OH Impervious Poor High Poor 10 10 — — — 10 14 —

Peat and otherhighly organicsoils

PT — — — — — — — — — — — —

1 Compacted to at least 95 percent of laboratory maximum dry density or to at least 70 percent relative density.2 Impervious: < 1 ft/yr (1 x 10-6 cm/s)

Semipervious: 1 to 100 ft/yr (1 x 10-6 cm/s to 1 x 10-4 cm/s).Pervious: > 100 ft/yr (1 x 10-4 cm/s).
EARTH MANUAL

52

can help direct an investigation toward specific soil types

best suited for the type of earthwork to be constructed.

Three important engineering properties of soils typical of

each classification group are listed on the chart adjacent to

the group symbol. They are: (1) permeability when

compacted, (2) shear strength when compacted and

saturated, and (3) compressibility when compacted and

saturated. In addition, workability as a construction

material is shown. Based on these properties, workability,

and experience, the use chart lists the soil groups’ relative

desirability for use in rolled earthfill dams, compacted earthlined canal sections, and compacted backfill. The numerical

ratings given in the chart are relative and are intended only

as a guide to aid the investigator in comparing soils for

various purposes.

Gravelly soils are normally preferred construction and

foundation materials because of their low compressibility

and high shear strength. The GW and GP soils are pervious

because they contain little or no fines to fill soil voids.

Ordinarily, good drainage is ensured. Their properties are

not affected appreciably by saturation and, if reasonably

dense, these soils have good stability and low

compressibility. In these respects, GW soils are better than

GP soils. The GW and GP soils are virtually unaffected by

freezing and thawing. 

As the sand, silt, and clay fractions increase, the matrix

soils begin to dominate the gravel skeleton structure, and the

total material assumes more of the characteristics of the

matrix. When properly compacted, GC soils are

particularly good material for homogeneous, small earthfill

dams or other embankments, or for the impervious sections

of high earth dams. Permeability of GC soil is low, shear

strength is high, and compressibility is low.

An important factor in the behavior of gravelly soils is the

gravel content at which interference between the large

particles begins to influence total material properties [48].

Extensive compaction studies demonstrated that particle

interference begins to influence compaction at about 30-,

35-, and 45-percent gravel content, respectively, for sandy,

silty, and clayey gravel soils tested, when placed using

standard compactive effort. Similarly, at about the same

gravel content, shear strengths show significant effects of

particle interference. Soils having angular gravel particles,

as compared to rounded particles, show interference

characteristics at lower gravel contents.

A mixture' s permeability is reduced as gravel content

increases because solid particles replace permeable voids

until the gravel content reaches an amount at which the

matrix soils (i.e., sand, silt, or clay) can no longer fill the

voids between the gravel particles. At that point,

permeability increases with increase in gravel content.

Structural characteristics of gravelly soils are largely

controlled by density, amount and shape of gravel particles,

and the amount and nature of the matrix soils. Usually,

cohesionless gravel soils have high shear strength and low

compressibility when placed at a relative density of

70 percent or above.

Structural characteristics of coarse sands approach those of

gravelly soils, but the structural characteristics of fine sands

are more like those of silty soils. As in gravelly soils,

density and amount and nature of the matrix (silt and clay)

control the structural properties of sand. The SW and SP

soils are pervious; whereas, SM and SC soils are

semipervious to impervious depending upon the amount and

character of the fines. When adequately compacted, SC

soils are good for impervious earthfill dams and other

embankment materials because of their low permeability,

relatively high shear strength, and relatively low

compressibility.

Other engineering problems encountered with sands are

normally related to density. Stability of pervious saturated

sands remains high as long as adequate drainage is

provided. Shear strength of saturated sands containing

appreciable amounts of silty and clayey fines will be

controlled by water content; thus, as density becomes lower

and water content becomes higher, shear strength decreases.

One of the most troublesome problems encountered by

geotechnical engineers is restricted drainage in saturated

sands because of low permeability or impervious

boundaries. If rapid loadings are applied and if soil density

is sufficiently low to allow volume decrease, high pore

pressure and reduced stability will result. This may cause

strains of unacceptable magnitude or even total failure

because of liquefaction. Seismic and equipment vibrations

and vehicular traffic loads are examples of rapid loadings

that must be resisted.

Coarse, cohesionless soils usually are not affected by

moderate water velocities. However, fine sands can be

loosened or rearranged by low velocities of waterflow.

Therefore, when constructing on sand below ground-water

table, the control of seepage is important to prevent particle

displacement causing erosion, loosening, or quick action

(quicksand).

Even small amounts of fines may have important effects on

the engineering properties of coarse-grained soils. For
CHAPTER 1—PROPERTIES OF SOILS

53

instance, as little as 5- to 10-percent fines in sands and

gravels may significantly reduce permeability and increase

susceptibility to frost action.

Silts are nonplastic, fine-grained soils that are inherently

unstable in the presence of water and, like fine sands, may

become quick. Silts are semipervious to impervious, often

difficult to compact, and are susceptible to damage by frost.

Typical bulky grained, inorganic-silt soils having liquid

limits of about 30 percent are less compressible than highly

micaceous and diatomaceous silts that have flaky grains and

have liquid limits above 100 percent.

1-25. Changes in Soil Properties.&Although soil

is commonly considered a stable material, it is constantly

changing, either gradually from solid rock to increasingly

finer particles or, conversely, gradually changing back to

rock. In most soils, this change is sufficiently gradual that

it is not a concern. However, in some soils, the change is

rapid enough to be important in the life of an engineered

structure. Soils where change may be important include

those with appreciable quantities of: (1) organic matter,

(2) soluble solids, or (3) minerals of volcanic origin.

Residual soils may be in a state of chemical alteration such

that during placement, they will have one set of

characteristics; later, during the life of the hydraulic

structure, they may have very different characteristics.

Frequently, existing soil deposits in their natural state have

been stable for many years and give every indication that

they will remain so. Nevertheless, human changes may

result in failure of some soils. One of the soils prone to

failure is called sensitive clay. This type of clay in an

undisturbed condition has substantial shear strength, which

to a large extent is lost upon being remolded. Very loose,

saturated, fine sand and silt&when subjected to dynamic

loading such as an earthquake or vibration from

machinery&will lose strength and behave like a viscous

liquid. This phenomenon is known as liquefaction.

Another group of soils exists where minor changes in

moisture content result in an abrupt change in shear

strength. In some cases, these soils, such as loessial soils,

have been deposited in a very loose state and exhibit change

in shear strength and can collapse and subside when the

moisture content is increased. Swelling clays frequently

exhibit a change in strength characteristics caused by an

increase in moisture.

Among the soils that, through desiccation, consolidation,

and chemical action, have changed to forms commonly

regarded as rock are varieties of shale, sandstone, and

limestone. When these rocks are exposed to air, marked

changes in characteristics can occur. Some shales flake off,

air slake, or weather rapidly&turning into soil. Some shales

may dry out without any apparent effect, but if rewetted,

they deteriorate rapidly into very soft clay. Some

sandstones and limestones harden on exposure to air and

retain their improved qualities, while other limestones and

sandstones break down rapidly with fluctuating temperature

and moisture content.

Although deterioration is rare, if unrecognized, failure can

occur without advance warning. Engineering practices for

treating soils that deteriorate are not well known. Where

situations as described above are suspected, the situation

should be reviewed by specialists in this field, and

specialized treatment may be necessary.

1-26. Workability.&Although laboratory testing

indicates the maximum extent to which engineering

properties such as shear strength, volume change, and

permeability of a given soil may vary, achieving these limits

in engineering practice is seldom practical. The ease with

which satisfactory values of engineering properties can be

economically reached is an important attribute of a soil, a

soil deposit, or a foundation.

The cost to procure a unit volume of soil and place it (as in

a structure) or for treating a unit amount of foundation

varies widely, not only according to soil type but according

to type and size of structure. Also, cost is influenced by the

kind of equipment available and by current available labor.

If a project is sufficiently large so that special equipment can

be economically used, maximum efficiency in construction

is most likely to be achieved. However, the soils selected

must be workable by such methods. 

Where separation of oversize is not required and where

mixing requirements are minimized, borrow pits which can

be preprocessed to optimum moisture content are preferable

and usually more economical, even though longer haul

distances may be required for their effective use. In

practice, situations arise where separation of oversize is

economical; also, cases exist where mixing two varieties of

soil is worthwhile. Instances occur where extensive efforts

to obtain maximum moisture control are justified; however,

such operations should be avoided if possible.

Test procedures do not exist for measuring workability.

Rather, all pertinent information concerning a soil, a borrow

pit, or a foundation is tabulated so the various design

possibilities can be evaluated. The engineering use chart

(table 1-4) provides qualitative information on the

workability of soils as a construction material and the

relative desirability of various soil types according to

structure. Borrow pits may be evaluated according to
EARTH MANUAL

54

amount of work required. Because equipment mobilization

is charged against a soil deposit, unit cost decreases

appreciably as the volume of work increases. The change

in unit cost for excavation up to about 100,000 m3

(100,000 yd3) is noticeable; then to 1 million m3 (1 million

yd3

) it is gradual; and beyond that range, unit cost is nearly

constant. Transportation costs are nearly constant above

about 100,000 m3

 (100,000 yd3), depending only on

distance. Moisture control costs depend primarily on the

uniformity and slope of the borrow area and the availability

of water. Excavation costs are influenced somewhat by

topography of the borrow area. Borrow pits slightly higher

in elevation than the work structure are preferable to those

below the work.

1-27. Frost Action.&Heaving of subgrades caused by

formation of ice lenses and subsequent loss of shear strength

upon thawing is known as frost action. Water rises by

capillarity and by thermal gradient toward the freezing zone

and forms lenses of ice, which heave the soil. Soils most

susceptible to frost action are those in which capillarity can

develop but are sufficiently pervious to allow adequate water

movement upward from below the freezing zone. Freezing

of the pore water in saturated fine-grained soils, called

closed-system freezing, decreases the density of soil by

expansion but does not result in appreciable frost heave

unless water movement can take place from below.

The severity of frost heave depends on three factors:

(1) type of soil, (2) availability of free water, and (3) time

rate of fluctuation of temperature about the freezing point.

Soils having a high percentage of silt-size particles are the

most frost susceptible. Such soils have a network of small

pores that promote migration of water to the freezing zone.

Silt (ML, MH), silty sand (SM), and clays of low plasticity

(CL, CL-ML) are in this category. Tests by the Corps of

Engineers from 1950 to 1970 [50] form the basis for figure 1-34; it relates frost susceptibility in terms of average

rate of heave in percent by mass finer than the U.S.A.

Standard 75-μm (No. 200) sieve. The figure shows most

soil types have a wide range of frost susceptibility without

a sharp dividing line between frost-susceptible and

nonfrost-susceptible soils. Nevertheless, silts, clayey silts,

and silty sands have the highest potential for frost heave

followed by gravelly and sandy clay, clayey sand, and

clayey gravel. Soils with the lowest potential to heave are

sandy gravels, clean sands, and silty sands with less than

3 percent finer than the 75-μm (No. 200) sieve [51]. In the

absence of a source of free water, frost heave is limited to

the increase in volume due to freezing of pore water. This

upper limit amounts to about 9 percent of pore water volume

[52].

1-28. Erodibility.&Erosion has been defined as

". . . a process of detachment and transport of soil particles

or particle groups by the forces of water, wind, ice, and

gravity [53]." Erodibility is the susceptibility of a soil to

erode.

The processes that influence erosion of cohesionless soil

particles have been understood for many years. A

cohesionless soil particle resting on the side or bottom of a

stream or canal is acted on by gravity and by a tractive or

erosive force caused by movement of water past the particle.

Thus, erosion resistance of cohesionless soils depends on

the applied tractive force and the mass of the particle

expressed in terms of mean particle diameter (D50). Figure 1-35 presents data collected by a number of investigators

showing the relationship between critical tractive force, the

force required to start erosion, and the mean particle

diameter [54].

The processes that influence erosion of cohesive soils have

been studied for a number of years but still are not

completely understood. Over the years, investigators have

attempted to correlate tractive force to various parameters

and properties of cohesive soil. Strong, consistent

correlation has not been found. Field performance data

have been collected on operating canals and streams as well

as laboratory data collected from various erosion devices,

including flumes, erosion tanks, submerged hydraulic jets,

and rotating cylinders. These studies have helped identify

the properties that influence erosion of cohesive soils but

have not provided quantifiable correlations between

laboratory tests and erodibility in the field. Some soil and

fluid properties that may influence the erosion process in

cohesive soil include:

 ̆ dry density and moisture content,

 ̆ grain-size distribution,

 ̆ Atterberg limits,

 ̆ undrained shear strength,

 ̆ clay mineralogy,

 ̆ pore-water chemistry,

 ̆ stress history,

 ̆ soil structure and fabric,

 ̆ chemistry of the eroding fluid,

 ̆ temperature,

 ̆ viscosity of the eroding fluid, and

 ̆ applied tractive stress [55].

1-29. Dispersive Clay.&Some unique cohesive soils

have been found to be highly erodible. These soils are

designated dispersive clay because they erode when the

individual clay particles disperse (go into suspension)&even

in the presence of still water. Dispersive clays cannot be 
55

Figure 1-34.—Frost susceptibility classification by percentage of mass finer than 0.02 mm [35].
EARTH MANUAL

56

Figure 1-35.—Limiting tractive forces recommended for canals and observed in rivers [54].
CHAPTER 1—PROPERTIES OF SOILS

57

distinguished from nondispersive clays by conventional

index tests such as gradation, Atterberg limits, or

compaction characteristics [56].

Dispersive characteristics are determined by performing

three standardized tests on the questionable clay sample

material. The three test results are combined to rate the clay

as dispersive, intermediate, or nondispersive [57]. The

three tests are USBR 5400, 5405, and 5410. 21

Chemical tests to determine quantity and type of dissolved

salts in the pore water are also useful in determining

dispersive potential of clay soils. Dispersive clays can be

made nondispersive by adding a small percentage of

hydrated lime (about 2 to 4 percent by dry mass of soil) to

the soil. Detrimental effects of dispersive clay (in hydraulic

structures) can also be minimized by proper zoning and by

using designed granular filters to prevent piping failures.

1-30. Dynamic Properties.&The response of soil to

cyclic or dynamic stress application must be considered in

the design of structures subjected to:

 ̆ earthquake loading,

 ̆ foundations subjected to machine vibrations, and

 ̆ subgrades and base courses for pavement.

A variety of laboratory equipment has been used to

determine the dynamic properties of soil including: 

 ̆ cyclic triaxial compression,

 ̆ cyclic simple shear,

 ̆ cyclic torsional shear,

 ̆ resonant column,

 ̆ ultrasonic devices.

The dynamic properties of most interest include: 

 ̆ shear modulus,

 ̆ damping ratio,

 ̆ dynamic shear strength,

 ̆ pore-pressure response.

Detailed dynamic properties test procedures are not included

in this manual; information on this subject may be found in

references [58,59,60,61].

21 5400: Determining Dispersibility of Clayey Soils by the Crumb

Test Method.

5405: Determining Dispersibility of Clayey Soils by the Double

Hydrometer Test Method.

5410: Determining Dispersibilit of Clayey Soils by the Pinhole

Test Method.
EARTH MANUAL

58

BIBLIOGRAPHY

[1] Wagner, A.A., "The Use of the Unified Soil

Classification System by the Bureau of Reclamation,"

Proceedings of the Fourth International Conference on Soil

Mechanics and Foundation Engineering, vol. I, pp. 125-

134, London, August 1957.

[2] Casagrande, A., "Classification and Identification of

Soils," Transactions, American Society of Civil Engineers,

vol. 113, pp. 901-991, 1948.

[3] Howard, A.K., "The Revised ASTM Standard on the

Unified Soil Classification System," Geotechnical Testing

Journal, GTJODJ, vol 7, No. 4, pp. 216-222, December

1984.

[4] Howard, A.K., "The Revised ASTM Standard on the

Description and Identification of Soils (Visual-Manual

Procedure)," Geotechnical Testing Journal, GTJODJ,

vol. 10, No. 4, pp. 229-234, December 1987.

[5] Bureau of Reclamation, Earth Manual, Part 2, 3d ed.,

1270 p., USBR 5000: "Procedure for Determining Unified

Soil Classification (Laboratory Method)," and USBR 5005:

"Procedure for Determining Unified Soil Classification

(Visual Method)," Denver CO, 1990.

[6] American Society for Testing and Materials D 2487:

"Standard Classification of Soils for Engineering Purposes

(Unified Soil Classification System)" and D 2488:

"Standard Practice for Description and Identification of

Soils (Visual-Manual Procedure)," West Conshohocken PA.

[7] Bureau of Reclamation, Laboratory Classification of

Soils, Geotechnical Branch Training Manual No. 4,

102 pp., Denver CO, January 1986.

[8] Bureau of Reclamation, Visual Classification of Soils,

Geotechnical Branch Training Manual No. 5, 106 pp.,

Denver CO, January 1986.

[9] Bureau of Reclamation, Soil Classification Handbook,

Geotechnical Branch Training Manual No. 6, 81 pp.,

Denver CO, January 1986.

[10] Hazen, A., "Discussion of Dams on Sand

Foundations," by A.C. Koenig, Transactions, ASCE,

vol. 73, pp. 199-203, 1911.

[11] Lambe, William T., and Robert V. Whitman, Soil

Mechanics, 553 pp., John Wiley and Sons, Inc., New York

NY, 1969.

[12] Atterberg, A., "Die Plastizität der Tone" (Plasticity of

Clays), Internationale Mitteilungen für Bodenkunde

(International Reports on Soil Science), vol. 1, pp. 10-43,

1911.

[13] Laboratory Report of Research Studies on Expansive

Clay for Desirable Placement Conditions and Identifying

Index Tests, Bureau of Reclamation Report No. EM-307,

Denver CO, July 25, 1952.

[14] Holtz, Robert D., and William D. Kovacs, An

Introduction to Geotechnical Engineering, 733 pp.,

Prentice-Hall, Inc., Englewood Cliffs NJ, 1981.

[15] Terzaghi, K., and Ralph B. Peck, Soil Mechanics in

Engineering Practice, 729 pp., John Wiley and Sons, Inc.,

New York NY, 1967.

[16] Proctor, R.R., "Fundamental Principles of Soil

Compaction," First of Four Articles on the Design and

Construction of Rolled-Earth Dams, Engineering News

Record, vol. 111, No. 9, pp. 245-248, August 31, 1933.

[17] Proctor, R.R., "Description of Field and Laboratory

Methods," Second of Four Articles on the Design and

Construction of Rolled-Earth Dams, Engineering News

Record, vol. 111, No. 10, pp. 286-289, September 7, 1933.

[18] Proctor, R.R., "Description of Methods," Third of

Four Articles on the Design and Construction of RolledEarth Dams, Engineering News Record, vol. 111, No. 12,

pp. 348-351, September 21, 1933.

[19] Proctor, R.R., "New Principles Applied to Actual

Dam-Building, Last of Four Articles on the Design and

Construction of Rolled-Earth Dams," Engineering News

Record, vol. 111, No. 13, pp. 372-376, September 28,

1933.

[20] Crossley, N.F., Laboratory Compaction Study, Bureau

of Reclamation Report No. EM-0.30, Tech. Memo. No.

405, Denver CO, October 19, 1934.
CHAPTER 1—PROPERTIES OF SOILS

59

[21] Hamilton, L.W., The Compaction of Earth

Embankments, Bureau of Reclamation Report No. EM-3.75,

Denver CO, December 1938.

[22] Gibbs, H.J., First Progress Report of Research on

Triaxial Shear Testing of Gravelly Soils, Bureau of

Reclamation Report No. EM-350, Denver CO, July 17,

1953.

[23] Ruettgers, A., and R.F. Blanks, Laboratory

Procedures in Testing Earth Dam Materials, Bureau of

Reclamation Tech. Memo. No. 533, Denver CO, September

1, 1936.

[24] Holtz, W.G., and C.A. Lowitz, Compaction

Characteristics of Gravelly Soils, Bureau of Reclamation

Report No. EM-509, Denver CO, September 20, 1957.

[25] Bieganousky, W.A., and W.F. Marcuson III,

Liquefaction Potential of Dams and Foundations: Report 1,

Laboratory Standard Penetration Tests on Reid Bedford

Model and Ottawa Sands, Research Report S-76-2, 96 pp.,

U.S. Army Corps of Engineers Waterways Experiment

Station, Vicksburg MI, October 1976.

[26] Bieganousky, W.A., and W.F. Marcuson III,

Liquefaction Potential of Dams and Foundations: Report 2,

Laboratory Standard Penetration Tests on Platte River and

Standard Concrete Sands, Research Report S-76-2, 47 pp.,

U.S. Army Engineer Waterways Experiment Station,

Vicksburg MI, February 1977.

[27] Bureau of Reclamation, Concrete Manual, 8th ed.,

rev. rep., 627 pp., Denver CO, 1981.

[28] Coulomb, C.A., Eassai sur une application des règles

des maximis et minimis à quelques problèmes de statique

relatifs à l' architecture, Mémoires de Mathematique et de

Physiques, Presentes a l'Academie Royale des Sciences, par

divers Savants, et lus dans ses Assemblees; Test of an

application of the rules of the maximum and minimum to

several problems of static relating to architecture.

Dissertations on Mathematics and Physics, presented before

the Royal Academy of Sciences by various scientists and

read during their assemblies; vol. 7, pp. 343-382, Paris,

1776.

[29] Holtz, W.G., and H.J. Gibbs, "Triaxial Shear Tests

on Pervious Gravelly Soils," Journal of the Soil Mechanics

and Foundation Engineering Division, ASCE, vol. 82, SM

1, January 1956.

[30] Skempton, A.W., "Fourth Rankine Lecture: LongTerm Stability of Clay Slopes," Geotechnique, vol. 14,

No. 2, pp. 77-101, 1964.

[31] Gould, J.P., Compression Characteristics of Roller

Fill Materials in Earth Dams, Bureau of Reclamation Tech.

Memo. 648, Denver CO, March 1954.

[32] Gibbs, H.J., Estimating Foundation Settlement by

One-Dimensional Consolidation Test, Engineering

Monograph No. 13, 24 pp., Bureau of Reclamation, Denver

CO, March 1953.

[33] Holtz, W.G., and J.W. Hilf, "Settlement of Soil

Foundations Due to Saturation," Proceedings, Fifth

International Conference on Soil Mechanics and Foundation

Engineering, vol. I, pp. 673-679, 1961.

[34] Gibbs, H.J., and W.Y. Holland, Petrographic and

Engineering Properties of Loess, Engineering Monograph

No. 28 (microfiche only), 37 pp., Bureau of Reclamation,

Denver CO, 1960.

[35] Holtz, W.G., and H.J. Gibbs, "Consolidation and

Related Properties of Loessial Soils," Symposium on

Consolidation Testing of Soils, ASTM STP 126, pp. 9-33,

1951.

[36] Gibbs, H.J., and J.P. Bara, "Predicting Surface

Subsidence from Basic Soil Tests," Field Testing of Soils,

ASTM STP 322, pp. 231-246, 1962.

[37] Gibbs, H.J., Properties Which Divide Loose and

Dense Uncemented Soils, Bureau of Reclamation Report

No. EM-608, Denver CO, January 6, 1961.

[38] Holtz, W.G., Notes for Lecture on Compaction and

Compaction Specifications (unpublished), October 1952.

[39] Clevenger, W.A., Laboratory Studies on Foundation

and Backfill Materials for Pumping Plants No. 1, 2, and 3,

and on Expansive Clays From the Wellton-Mohawk

Canal&Wellton-Mohawk Division&Gila Project, Bureau of

Reclamation Report No. EM-240, Denver CO,

August 28, 1950.

[40] Clevenger, W.A., Laboratory Studies on Expansive

Clays, Lindmore Irrigation District, Friant-Kern

Distribution System, Central Valley Project, Bureau of

Reclamation Report No. EM-267, Denver CO, April 30,

1951.
EARTH MANUAL

60

[41] Gibbs, H.J., Laboratory Report of Research Studies on

Expansive Clay for Desirable Placement Conditions and

Identifying Index Tests, Bureau of Reclamation Report No.

EM-307, Denver CO, July 25, 1952.

[42] Holtz, W.G., Expansive Clays&Properties and

Problems, Bureau of Reclamation Report No. EM-568,

Denver CO, November 6, 1959.

[43] Howard, A.K., and J.P. Bara, Lime Stabilization on

Friant-Kern Canal, Bureau of Reclamation Report

No. REC-ERC-76-20, 53 pp., Denver CO, December 1976.

[44] Gibbs, H.J., Summary of Research Studies on Loess

for Use as Foundations and Construction Material, Bureau

of Reclamation Report No. EM-424, Denver CO, July 13,

1955.

[45] Jones, C.W., The Permeability and Settlement of

Laboratory Specimens of Sand and Sand-Gravel Mixtures,

Bureau of Reclamation Report No. EM-353, Denver CO,

March 26, 1954.

[46] Bureau of Reclamation, Design Standards No. 13&

Embankment Dams:

Ch. 1: General Design Standards, 19 pp., Aug. 1986.

Ch. 2: Embankment Design, 123 pp., June 1992.

Ch. 3: Foundation Surface Treatment, 16 pp., Sept.

1984.

Ch. 4: Static Stability Analyses, 36 pp., July 1987.

Ch. 5: Protective Filters, 20 pp., May 1987.

Ch. 7: Riprap Slope Protection, 54 pp., July 1992.

Ch. 8: Seepage Analysis and Control, 42 pp., Mar.

1987.

Ch. 9: Static Deformation Analysis, 28 pp., July

1991.

Ch. 10: Embankment Construction, 55 pp., July 1991.

Ch. 11: Instrumentation, 53 pp., July 1990.

Ch. 12: Foundation and Earth Materials Investigation,

86 pp., Oct. 1989.

Ch. 13: Seismic Design and Analysis, 190 pp., Dec.

1989.

Ch. 16: Cutoff Walls, 24 pp., June 1991.

Ch. 17: Soil-Cement Slope Protection, 114 pp., Oct.

1990.

Ch. 19: Geotextiles, 83 pp., Sept. 1992.

Ch. 20: Geomembranes, vol. 1, 182 pp., Sept. 1991.

Ch. 20: Geomembranes, vol. 2, 302 pp., Sept. 1991.

[NOTE. - Nos. 6, 14, 15, and 18 out-of-print]

[47] Bureau of Reclamation, Ground Water Manual, rev.

rep., pp. 197-415, Denver CO, 1995.

[48] Holtz, W.G., and C.A. Lowitz, "Compaction

Characteristics of Gravelly Soils," Conference on Soils for

Engineering Purposes, ASTM STP 232, pp. 67-101,

Conshohocken, 1957.

[49] Karpoff K.P., Frost-Action Test on Spillway

Foundation Materials&Kerwin Dam, Missouri River Basin

Project, Kansas, Bureau of Reclamation Report No. EM326, Denver CO, November 14, 1952.

[50] Department of the Army, Pavement Design for Frost

Conditions, Technical Manual&TM 5-818-2, July 1965.

[51] Jones, C.W., D.G. Miedema, and J.S. Watkins, Frost

Action in Soil Foundations and Control of Surface Structure

Heave, Bureau of Reclamation Report No. REC-ERC-82-

17, 69 pp., Denver CO, June 1982.

[52] Gibbs, H.J., Soil Engineering in Frost Area&A

Summary of the Summer Session Given at Massachusetts

Institute of Technology, June 11 to 21, 1957, Bureau of

Reclamation Report No. EM-510, Denver CO, October 3,

1957.

[53] Shaika, A., J.F. Ruff, and S.R. Abt, Surface Erosion

of Compacted Clays, Civil Engineering Department,

Colorado State University, Fort Collins CO, May 1986.

[54] Lane, E.W., Progress Report On Results of Studies on

Design of Stable Channels, Bureau of Reclamation Report

No. HYD-352, Denver CO, June 1952.

[55] "Erosion of Cohesive Sediments," Journal of the

Hydraulics Division, Task Committee on Erosion of

Cohesive Materials, ASCE, vol. 94, No. HY4, pp. 1,017-

1,049, July 1968.

[56] Sherard, J.L., L.P. Dunnigan, and R.S. Decker,

"Some Engineering Problems With Dispersive Clay,"

Dispersive Clays, Related Piping, and Erosion in

Geotechnical Projects, ASTM STP 623, May 1977.

[57] Kinney, J.L., Laboratory Procedures for Determining

the Dispersibility of Clayey Soils, Bureau of Reclamation

Report No. REC-ERC-79-10, 20 pp., Denver CO,

September 1979.

[58] Tiedemann, D.A., L.P. Kaufman, and J. Rosenfield,

Determining Dynamic Properties for Embankment Dams

from Laboratory Testing, Bureau of Reclamation Report

No. REC-ERC- 84-17, 34 pp., Denver CO, December

1984.
CHAPTER 1—PROPERTIES OF SOILS

61

[59] Bureau of Reclamation, Design Standards No. 13&

Embankment Dams, Ch. 13: Seismic Design and Analysis,

190 pp., Denver CO, December 1989.

[60] Department of the Army, Laboratory Soils Testing,

EM-1110-2-1906, Change 1, App. XA: Cyclic Triaxial

Tests, Office of the Chief of Engineers, May 1980.

[61] Department of the Navy, Soil Dynamics, Deep

Stabilization, and Special Geotechnical Construction,

Design Manual 7.3&NAVFAC DM-7.3, April 1983.
63

Chapter 2

INVESTIGATION

A. Principles of Investigations

2-1. General.&

a. Objectives.&The purpose of an investigation is to

obtain information relating to foundation conditions and to

natural construction materials commensurate with the type

of structure involved and with the stage of the project. The

investigation is conducted in the office, in the field, and in

the laboratory. Characteristics of subsurface conditions are

developed in progressively greater detail as exploratory

work proceeds. Investigations should be performed in

phases so the program can be reevaluated and revised to

obtain maximum information at least cost. Data obtained

must be organized to clearly show significant features of the

occurrence and properties of the materials.

Specific objectives of an investigation are to determine (as

required):

 ̆ The regional geology influence on materials, site, and

structure characteristics, particularly seismotectonics.

 ̆ The location, sequence, thickness, and areal extent of

each stratum, including a description and

classification of the materials and their structure and

stratification in the undisturbed state. Significant

geologic features such as concretions, fabric, and

mineral and chemical constituents should be noted.

 ̆ The depth to and type of bedrock:

% location,

% depth of weathering, 

% sequence,

% seams,

% thickness,

% joints,

% areal extent,

% fissures,

% attitude,

% faults,

% soundness, and

% other structural features.

 ̆ The characteristics of the ground water:

% depth to water table, 

% whether the water table is perched or normal, 

% depth of and pressure in artesian zones,

% quantity and types of soluble salts or other minerals

present, and

% water chemistry particularly for any contaminants.

 ̆ Properties of the materials by methods appropriate

for the investigation stage, the type of structure, and

detailed engineering data:

% by describing and identifying materials in place

visually, and determining in-place density.

% by obtaining disturbed samples, describing and

identifying them visually, and determining their inplace water content and index properties.

Engineering properties may be estimated on the

basis of the classification along with results of

laboratory index tests.

% by indirect methods performed in the field such as

geologic interpretations, in-place tests, or surface

geophysical methods, using results of direct

explorations and other tests to provide necessary

correlations.

% by observing performance of previously

constructed structures built of or placed on similar

materials.

% by observing natural slopes of similar materials.

% by obtaining undisturbed samples, identifying them

visually, describing their undisturbed state,

determining in-place density and water content, and

obtaining index and engineering properties by

laboratory tests.

% by performing tests in the field such as standard

penetration tests, cone penetration tests, bearing

capacity tests, pile loading tests, permeability tests,

pressuremeter tests, dilatometer tests, and vane

shear tests.

b. Classification of Structure Foundations.&For

structures used by the Bureau of Reclamation (Reclamation),

investigation requirements for foundations vary over a wide

range and may include consideration of the foundation

material use both for the foundation and for the structure.

Foundations for structures can be conveniently grouped into

four classes to assist in determining type and degree of

foundation investigation required:
EARTH MANUAL

64

(1) The engineering properties of the material are

unacceptable, and the soil or rock must be partially or

entirely removed to provide a satisfactory foundation

for the structure under consideration.

(2) The soil or rock in place will provide the structure

foundation, either with or without ground improvement.

(3) The soil or rock provides both the foundation and a

major part of the structure&with material from the

required foundation excavation provided for use in the

structure.

(4) Same as (3), except that substantial amounts of

material are needed for the structure in addition to that

available from the required excavation.

For structures constructed on rock, in addition to

investigations of the rock foundation, a soil investigation is

made in which primary concerns are depth to bedrock,

stability of slopes, and difficulty of excavation. Stability of

reservoir rims should also be considered and investigated if

problem areas are identified. Materials from excavations

for structures in class 3 should be used for other

construction purposes when feasible. For example, a site

considered suitable for a concrete dam will usually require

temporary cofferdams, and materials from required

excavations could be used for that purpose. Aggregate

sources for concrete and for filters for earth and rockfill

dams also need to be located and investigated.

For structures founded on soil, the primary objective of a

soil investigation is to determine soil volume change

characteristics that may result in foundation settlement or

heave. Dispersivity and soluble salts could also be

important, depending on the structure type. If heavy

loading and wet soil conditions are anticipated, the shear

strength should be investigated.

For structures which use materials from required

excavations, materials must be considered from both

stability and utilization standpoints. Stability of slopes, both

in cuts and fills, is a primary consideration.

Compressibility varies in importance, approximately

commensurate with the importance of the structure

itself&having little significance where roads and laterals are

concerned&but major importance where paved highways

and large lined canals with large structures are required. In

expansive soils and in-place low density soils, the

probability and magnitude of uplift and collapse must be

evaluated. Permeability is important on canals and laterals.

Where a choice in location is possible, workability of

materials is of major economic importance. For this reason,

cuts into bedrock are normally avoided.

2-2. Sources of Map and Photo Information.&

a. U.S. Department of Agriculture (Aerial

Photography).&The U.S. Department of Agriculture

(USDA) is an excellent source of aerial photography. The

Aerial Photography Field Office (APFO) is the depository

and reproduction facility of the U.S. Department of

Agriculture’s aerial photography, housing aerial film

acquired by the Agricultural Stabilization and Conservation

Service (ASCS), Natural Resources Conservation Service

(NRCS), and the U.S. Forest Service. Combined aerial

photography covers about 95 percent of the conterminous

United States (see sec. 2-3d for more information). APFO’s

film holdings include black and white panchromatic, natural

color, and color infrared films (CIR) with negative scales

ranging from 1:6000 to 1:120,000. National High Altitude

Photography (NHAP) is a primary source of new aerial

photography. APFO libraries keep the original CIR

positives which are flown at a scale of 1:60,000 with each

exposure covering 68 square miles.

Ordering information can be obtained from:

U.S. Department of Agriculture % ASCS

Aerial Photography Field Office

Customer Services

2222 West 2300 South

PO Box 30010

Salt Lake City UT 84130-0010

b. The U.S. Geological Survey (USGS).&The USGS

produces information in many forms that can be useful in

local engineering studies: maps, scientific reports, geodetic

data, aerial photographs, bibliographic data, and other

forms. Most of these products are available from one or

more of the following sources: 

 ̆ USDA&aerial

 ̆ USGS Distribution&maps and published reports

 ̆ USGS Earth Science Information Center Open-File

Report unit&open-file reports

 ̆ Earth Science Information Centers (ESICs)&maps,

reports, aerial photographs, and general information

on many earth science topics

 ̆ Water Resources Division (WRD)&state water data

reports

 ̆ National Technical Information Service (NTIS)
CHAPTER 2—INVESTIGATION

65

Most maps and reports are available for reference in USGS

libraries, in selected U.S. Government Printing Office

(GPO) Depository Libraries, and in large university libraries

and are available commercially. 

c. USGS Products.&Maps, cross sections, and related

indexes.

 ̆ Topographic maps are the most common USGS

maps. For most parts of the United States,

topographic maps are available in several scales: 

% 1 : 24,000

% 1 : 100,000

% 1 : 250,000

% 1 : 500,000

% 1 : 1,000,000

% 1 : 62,500 and 1 : 63,360 scale maps are available

for some areas of the country.

% 1 : 50,000 and 1 : 100,000 scale county maps are

being prepared in selected States.

% Topographic maps are available commercially and

from USGS Distribution and Earth Science

Information Centers.

% Topographic data (in digital form) called digital

elevation models (DEMs) and digital line graphs

(DLGs), are available from ESICs, the EROS Data

Center (EDC), and commercial vendors.

% Specific information about topographic maps is

presented State by State in the USGS: Indexes and

Catalogs to Topographic and Other Map Coverage

[1].

 ̆ Geologic maps are of many kinds: bedrock geology

and surficial geology are the most common, but maps

showing depth to bedrock, bedrock structure

contours, coal or other mineral resources, basement

geology, and similar maps also are considered

geologic maps. Cross sections are presented on

many geologic and hydrologic maps but are not

generally available separately. Bedrock and surficial

geologic maps are available in many scales; such

maps, at detailed scales (1 : 24,000 or larger), have

been published for only about one-third of the United

States. To identify maps available for a specific

place, use the USGS Geologic Map Index for that

State or the USGS GEOINDEX data base, which

contains the same information but is more up to date.

The State geoscience agencies can be helpful in

identifying such geologic maps.

 ̆ Hydrologic maps, like geologic maps, can be of

many kinds: water table contours, aquifers and

aquicludes, water quality, hydrologic units

(watersheds), flood hazards, and so on. These kinds

of maps are published by the USGS and other

Federal, State, and local government agencies. The

USGS hydrologic maps are published either as

thematic maps available from USGS Distribution or

in open-file reports available from the ESIC

Open-File Report unit. Hydrologic maps are listed in

the annual catalogs.

 ̆ Geophysical maps show information about

geomagnetism, gravity, radioactivity, and many other

geophysical characteristics. Geochemical maps show

information related to stream sediment samples

processed in search of mineral resources. Seismicity

maps show information about earthquake history,

severity, and risk. Hazard maps can show areas of

swelling clays, landslides and related hazards,

avalanche danger, volcanic and earthquake hazards,

and other geologic hazards. These maps are

available either as published USGS thematic maps

from USGS Distribution or as open-file reports from

the ESIC Open-File Report unit. 

 ̆ River surveys and wetlands inventory maps may be of

particular interest to investigators studying river sites.

River surveys were mostly conducted between 30 and

60 years ago in support of large-scale engineering

projects. Some maps are still available showing river

courses and profiles. Wetlands inventory maps,

which show kinds of wetland ecosystems, are being

made by the U.S. Fish and Wildlife Service for

7.5-minute quadrangles.

 ̆ Out-of-print (o.p.) USGS maps generally are

available for reference in libraries and from other

sources. Blueprint copies of o.p. topographic maps

are available from ESICs. Generally, reproductions

of o.p. thematic maps are available from the U.S.

National Archives, Cartographic Division. Another

source of o.p. maps is map dealers, of whom some

specialize in old, rare maps.

 ̆ Other miscellaneous maps are available from the

USGS, including folios (sets of environmental maps

of many selected areas showing geologic, hydrologic,

land use, historical, and other features) and

wilderness area maps. 

d. USGS Technical Reports.&The USGS publishes

several kinds of technical reports. These reports are useful

in many earth science disciplines, including engineering

geology and hydrology; most are listed in annual catalogs

and bibliographies. 
EARTH MANUAL

66

e. USGS Publications.&Publications catalogs have

been published annually. This USGS information has been

available since 1982; earlier publications are compiled into

larger catalogs:

 ̆ Publications of the U.S. Geological Survey, 1971-81

 ̆ Publications of the U.S. Geological Survey, 1962-70

 ̆ Publications of the U.S. Geological Survey, 1879-

1961

These are available from USGS Distribution and from

ESICs. A monthly list, "New Publications," of new USGS

publications is available free from USGS. Bibliographies of

USGS publications on selected topics are available as

open-file reports, bulletins, and other publications.

Additional unpublished bibliographies on selected geologic

topics are also available from the Geologic Inquiries Group

(GIG).

A complete bibliography of USGS publications, "Publications of the U.S Geological Survey" [2], includes

information on all but the topographic maps described above

and is available on CD ROM from the American Geological

Institute GeoRef Information System. Other selected

references are listed in the bibliography [3, 4, 5, 6].

Several USGS data bases of bibliographic and similar

information are available to help identify USGS products:

 ̆ Earth Science Data Directory lists earth science data

files and data bases from many sources, including

many outside the USGS. 

 ̆ Map and Chart Information System is a data base

listing USGS and other maps and charts.

 ̆ Cartographic Catalog is a data base listing kinds of

maps and such map-related information as map

dealers, geographic software vendors, and producers

of globes. 

 ̆ Aerial Photography Summary Record System is a

data base for information about aerial photographic

coverage of the United States. 

 ̆ GEOINDEX is a data base of bibliographic and

related information about geologic maps of the

United States. 

 ̆ Library data base provides bibliographic information

about recent acquisitions of the USGS library; this

data base includes many non-USGS publications.

 ̆ Selected Water Resources Abstracts presents abstracts

of water resources reports and articles published by

many organizations.

f. USGS Software, Data, and Related

Products.&The USGS has published (and released in other

ways) computer software.

The USGS Open-File Report 89-681 (available from the

ESIC Open-File Report unit) lists USGS software published

as of June 1989 [7]. The individual publications describing

or containing computer programs are also listed in USGS

publications catalogs and in other references listed above.

For many parts of the country, the USGS also has digital

data useful in many earth science investigations:

 ̆ DLGs, i.e., digital map data such as roads, streams,

and boundaries

 ̆ DEMs, i.e., digital map data showing topography

 ̆ digital versions of land use and land cover data

 ̆ geographic names information

 ̆ stream gauge data

 ̆ water well data

 ̆ geophysical logs

 ̆ other kinds of data

One can check on data bases available in the Earth Science

Data Directory and contact an ESIC for more information

on access to USGS data.

g. USGS Remote Sensing Products.&The USGS

has acquired many aerial photographs, orthophotos, satellite

photographs, and many kinds of satellite imagery such as:

 ̆ Landsat multispectral scanner (MSS)

 ̆ Landsat thematic mapper (TM)

 ̆ side-looking airborne radar (SLAR)

 ̆ advanced very-high resolution radiometer (AVHRR)

Aerial photographs are available for the entire United States,

and in many places, an option of scales and acquisition dates

is available. Orthophotos are made from aerial photographs

that have been geometrically corrected to eliminate

displacements present in the aerial photographs; these are

available for many parts of the country. For assistance, in

ordering any kind of aerial photograph or satellite image,

contact an ESIC for help in identifying the best coverage,

which varies depending on how it will be used.

The USGS has also collected geophysical data, including

gravity data, aeromagnetic and aeroradioactivity. For

detailed information about the availability of these kinds of

geophysical data for a specific area, contact the USGS
CHAPTER 2—INVESTIGATION

67

Branch of Geophysics. Information about magnetic

declination is available from the National Geomagnetic

Information Center. The National Uranium Resource

Evaluation (NURE) program collected a large amount of

general aeromagnetic data and stream-sediment-sample

geochemical data for most of the country; NURE data are

available in published form from the ESIC Open-File Report

unit and in digital form from the EDC. For more

information on remote sensing, see section 2-3.

h. Access to USGS Data Bases.&

Earth Science Data Directory (ESDD)

On several CD-ROM products, on-line, ESDD Project

Manager, U.S. Geological Survey, 801 National

Center, Reston VA 22092.

GEOINDEX

On several CD-ROM products and available for

personal computer style microcomputers as USGS

Open-File Report 91-575.

Selected Water Resources Abstracts (SWRA)

On several CD-ROM products, online, on Dialog

(file 117), and through the WAIS system on Internet.

i. Sources of USGS Products.&

USGS Distribution 

Distribution, U.S. Geological Survey, PO Box 25286,

Denver Federal Center, Denver CO 80225.

Open-File Reports

ESIC Open-File Report unit, U.S. Geological Survey,

PO Box 25425, Denver Federal Center, Denver

CO 80225.

ESICs

Reston ESIC, 507 National Center, Reston VA 22092

(1-800-USA-MAPS).

Washington, DC ESIC, U.S. Department of the

Interior, 1849 C St., NW, Rm. 2650, Washington

DC 20240.

GIG

Geologic Inquiries Group, U.S. Geological Survey,

907 National Center, Reston VA 22092.

EDC

EROS Data Center, U.S. Geological Survey, Sioux

Falls SD 57198.

USGS Libraries

Library, U.S. Geological Survey, 950 National Center,

Reston VA 22092.

Cartographic Information Center, 952 National Center,

Reston VA 22092.

Library, U.S. Geological Survey, MS 955,

345 Middlefield Rd., Menlo Park CA 94025.

Library, U.S. Geological Survey, MS 914, Bldg. 20,

PO Box 25046, Denver Federal Center, Denver CO

80225.

Library, U.S. Geological Survey, 2255 North Gemini

Dr., Flagstaff AZ 86001.

NTIS

National Technical Information Service,

U.S. Department of Commerce, 5285 Port Royal Rd.,

Springfield VA 22161.

New Publications and monthly list

USGS New Publications, 582 National Center, Reston

VA 22092.

Commercial map dealers

Local map dealers are listed in the telephone yellow

pages under "Maps." A map information specialist at

ESIC' s toll-free telephone number, 1-800-USA-MAPS,

also provides names and addresses of map dealers for

anywhere in the United States.

Earthquake information

National Earthquake Information Center,

U.S. Geological Survey, MS 967, PO Box 25046,

Denver Federal Center, Denver CO 80225.

USGS publications CD-ROM

American Geological Institute, GeoRef Information

System, 4220 King St., Alexandria VA 22302-1507.

Guide to USGS maps

Documents Index, Inc., PO Box 195, McLean

VA 22101.

Soil surveys

U.S. Department of Agriculture, Natural Resources

Conservation Service offices or extension offices

located in most counties nationwide; State Soil

Conservationist office located in most State capitals.
EARTH MANUAL

68

Out-of-print maps

U.S. National Archives, Cartographic Branch

(National Science Foundation [NSF] Network Service

Center [NNSC]), Washington DC 20408,

j. USGS Topographic Maps.&A topographic map is

useful in the design and construction of most civil

engineering structures. Before undertaking the painstaking

job of mapmaking, a thorough search should be made for

existing maps which cover the area of the structure and

potential sources of construction materials. The USGS has

made a series of standard topographic maps covering the

United States and Puerto Rico.

The unit of survey for USGS maps is a quadrangle bounded

by parallels of latitude and meridians of longitude.

Quadrangles are available generally covering 7.5 minutes,

15 minutes, and 30 minutes of latitude and longitude, and

possibly at several scales such as 1 : 24,000 (1 inch equals

2000 feet for 7.5 minutes of latitude and longitude). Each

quadrangle is designated by the name of a city, town, or

prominent natural or historical feature within it; the margins

of each map are printed with the names of adjoining

quadrangle maps. In addition to published topographic

maps, the USGS has other information for mapped areas;

for example, location and true geodetic position of

triangulation stations and elevation of permanent

benchmarks established by the USGS.

River survey maps are important to dam planning. These

are topographic strip maps that show the course and fall of

a stream; configuration of the valley floor and the adjacent

slopes; and locations of towns, scattered buildings or

houses, irrigation ditches, roads, and other cultural features.

River survey maps were prepared in connection with the

classification of public lands; hence, most of them are of

areas in the Western United States. If a valley is less than

1.6 km (1 mi) wide, the topography is usually shown to

30 m (100 ft) or more above the water surface; if the valley

is flat and wide, topography is shown for a strip of 1.6 to

3.0 km (1 to 2 mi) parallel to the river or stream. The usual

scale is 1 : 31,680 or 1 : 24,000, and the normal contour

interval is 6 m (20 ft) on land and 1.5 m (5 ft) on the water

surface. Many of these maps include proposed damsites on

larger scale topography and show a profile of the stream.

k. USGS Geologic Maps.&Important information is

obtainable from geologic maps. These maps identify the

rock units directly underlying the project area.

Characteristics of rocks are of major importance in selection

of a damsite and in design of water-retaining and

conveyance structures. Many surface soils are closely

related to the type of rock from which they are derived, but

if the soil has been transported, it may overlie an entirely

different rock type. When the influence of climate, relief,

and geology of the area is considered, reasonable

predictions can be made of the type of soil which will be

encountered or of the association with a particular parent

material. Subsurface conditions can often be deduced from

the three-dimensional information given on geologic maps.

These maps are especially valuable in areas where only

limited information on soils or agricultural classifications

are available; for example, in arid or semiarid regions

where soils are thin.

Commonly available general purpose geologic maps

(e.g., USGS-type maps) are not detailed enough for sitespecific needs. Geology for engineering exploration,

design, and construction must be generated for the specific

application. Horizontal scales of 1 in to 50 or 100 ft and

contour intervals of 1 to 5 ft are common. Site-specific

maps are usually generated using aerial photographs flown

for the application, although small maps may be prepared

using plane table or ground survey data.

Site geologic maps are used for the design, construction,

and maintenance of engineering features. These maps

concentrate on geologic and hydrologic data pertinent to the

engineering needs of a project and do not address the

academic aspects of the geology. 

Rocks are identified on geologic maps by name and geologic

age. The smallest rock unit mapped is generally a

formation, but smaller subdivisions such as members or

beds may be delineated. A formation is an individual bed

or several beds of rock that extend over a fairly large area

and can be clearly differentiated from overlying or

underlying beds because of a distinct difference in lithology,

structure, or age. The areal extent of these formations is

indicated on geologic maps by means of letter symbols,

color, and symbolic patterns.

Geologic maps often show one or more geologic sections.

A section is a graphic representation of the disposition of the

various strata in depth, along an arbitrary line usually

marked on the map. Geologic sections are interpretive and

should be used with that in mind. The vertical scale may be

exaggerated. Sections prepared solely from surface data are

less accurate; sections prepared from boring records or

mining evidence are more reliable. A section compiled to

show the sequence and stratigraphic relations of the rock

units in one locality is called a columnar section; it shows

only the succession of strata and not the structure of the

beds as does the geologic section.
CHAPTER 2—INVESTIGATION

69

Several types of geologic maps are available. A bedrock or

areal geologic map shows a plan view of the bedrock and

surficial materials in the area. This type of map shows the

boundaries of formations, inferred where the units are

covered by soil or plant growth, and may include one or

more geologic sections. Areal maps do not show soil except

for indicating thick deposits of alluvial, glacial, or windblown materials. In areas of complex geology where

exposures of bedrock are scarce, location of the contacts

between formations is often indicated as approximate.

Surficial geologic maps differentiate surface materials of the

area according to their geologic categories such as stream

alluvium, glacial gravel, and windblown sand. These maps

indicate the areal extent, characteristics, and geologic age of

surface materials. Areal (bedrock) geologic maps of

moderately deformed areas often show enough structural

detail to provide an understanding of the structural geology

of that region; in many instances, generalized subsurface

structure can be deduced from distribution of the formations

on the map. In highly complex areas, where a great amount

of structural data is necessary for an interpretation of the

geology, special structural geologic maps are prepared.

In addition to giving the geologic age of mapped rocks,

some maps briefly describe the rocks. Many maps,

however, lack a lithologic description. An experienced

geologist may make certain assumptions or generalizations

based only on the age of rock by making analogies with

other areas. Geologic literature on the entire area must be

consulted for more detail and for certain identification of the

lithology. Engineering information can be obtained from

geologic maps if the user has the appropriate background

and experience. It is possible to prepare a preliminary

construction materials map by study of a basic geologic

map, together with all collateral geologic data that pertain to

the area shown. Similarly, preliminary foundation and

excavation conditions, as well as surface and ground-water

data, can be deduced from geologic maps. Such

information is valuable for preliminary planning activities

but is not a substitute for detailed field investigations during

the feasibility and specifications stages.

l. Agricultural Soil Maps.&A large portion of the

United States has been surveyed by the USDA. These

investigations are of surficial materials. The lower limit of

soil normally coincides with the lower limit of biological

activity and root depth. Soils are examined down to rock or

down to 2 m (80 in)&possibly deeper in some cases. Soils

are classified according to soil properties including color,

structure, texture, physical constitution, chemical

composition, biological characteristics, and morphology.

The USDA publishes reports of these surveys in which the

different soils are described in detail; interpretations are

given for agricultural and certain nonagricultural uses. Each

report includes a map of the area surveyed (usually a

county) showing by pedological classification the various

kinds of soils present. In addition to published soil maps,

many areas are shown in which individual farms and

ranches are mapped using the same system of soil

classification and interpretation.

Agricultural soil maps can be obtain from the State or local

office of the NRCS, from a county agent, or from a

congressional representative. Many libraries keep published

soil surveys on file for reference. Also, resources

conservation district offices and county agricultural

extension offices have copies of local soil surveys that can

be used for reference. Out-of-print maps and other

unpublished surveys may be available for examination from

the USDA, county extension agents, colleges, universities,

and libraries. Using the agricultural soil classification

system, soil surveys have been made for many river basins

in the 17 Western States to classify land for irrigation based

on physical and chemical criteria. Inquiry should be made

at the local Reclamation area offices concerning availability

of soil data for these areas.

When applying agricultural soil maps to exploration for

foundations and construction materials, some knowledge of

the pedological system of classification is necessary. This

system is based on the premise that water leaches inorganic

colloids and soluble material from upper layers to create

distinct layers of soil. The depth of leaching action depends

on the amount of water, permeability of the soil, and length

of time involved. The surface layer lacks in fines which are

accumulated in a subsurface layer containing these fines in

addition to its original fines. Deep soil beneath the

subsurface layer has been little affected by water and

remains essentially unchanged. Exceptions are in the

Southeastern United States (or other humid areas) where

some soils are weathered to greater depths.

Three layers are typically developed from the surface

downward: the A horizon, the B horizon, and the

C horizon. In some soils, an E horizon (a more leached

horizon) is between the A and B horizons. In detailed

descriptions, these horizons may be subdivided into A1, A2,

B1, B2, etc.

Soils of the United States are divided into main divisions

depending on the cause of profile development and on the

magnitude of the cause. The main soil divisions are further

divided into "suborders," then into "great groups" based on

the combined effects of climate, vegetation, and topography.

Within each "great group," soils are divided into soil series,

of which each has the same degree of development, climate,
EARTH MANUAL

70

vegetation, relief, and parent material. In the pedological

classification system, all soil profiles of a certain soil series

are similar in all respects, except for variation in texture or

grain size of the topsoil or A horizon. Typically, the soil

series are named after a town, county, stream, or similar

geographical source where the soil series was first

identified.

The final soil mapping unit, which is called the soil phase,

consists of the soil series name plus the textural

classification of the topsoil or A horizon plus other features

such as slope, flooding, etc. The USDA' s textural

classification system is different from the Unified Soil

Classification System used for engineering purposes.

Figure 2-1 shows textural classification of soils used by

USDA [8]. The chart shows terminology used for different

percentages of:

 ̆ clay . . . . . particles smaller than 0.002 mm,

 ̆ silt . . . . . . 0.002 to 0.05 mm, and

 ̆ sand . . . . . 0.05 to 2.0 mm. 

Note the term "loam" is a mixture of sand, silt, and clay

within certain percentage limits. Other terms (used as

adjectives to the names) obtained in the USDA system are:

 ̆ gravelly . . . rounded and subrounded particles from

2 to 75 mm,

 ̆ cobbly . . . 75 to 250 mm (3 to 10 in), and

 ̆ stony ....sizes greater than 250 mm (10 in).

The textural classification&given as part of the soil name on

the agricultural soil map&refers to material in the A horizon

only; hence, this is not of much value to an engineer

interested in the entire soil profile. The combination of soil

series name and textural classification to form a soil type,

however, provides a considerable amount of significant

data. For each soil series, the following can be obtained:

 ̆ texture,

 ̆ degree of compaction,

 ̆ presence or absence of hardpan or rock,

 ̆ lithology of the parent material, and

 ̆ chemical composition.

A table of estimated engineering sieve sizes, the Unified

Soil Classification System and American Association of

State Highway and Transportation Officials (AASHTO)

classification, and Atterberg limits are included in each

published soil survey. In addition, actual test data from the

survey area is published in some cases.

The following example is taken from the Soil Survey Data

Base available from offices of USDA' s Natural Resources

Conservation Service. The "Cecil Series" is described by

a general geographical distribution of the series, the rocks

from which it was derived, and information on climate. A

comparison is made to series with associated or related soil

series. Additional discussion concerns the range in

characteristics of the Cecil Series as well as: relief,

drainage, vegetation, land use, and remarks; and

distribution of the series by States and location. A soil

pedon description for the Cecil Series is given as follows.

The Cecil Series consists of very deep, well-drained,

moderately permeable soils on ridges and side slopes of the

Piedmont uplands. They are deep to saprolite and very deep

to bedrock. They formed in residuum weathering from felsic

crystalline rocks of the Piedmont uplands. Slopes range from

0 to 25 percent. Mean annual precipitation is 1220 mm (48 in)

and mean annual temperature is 15 (C (59 (F) near the type

location.

Taxonomic Class: Clayey, kaolinitic, thermic Typic

Kanhapludults

Typical Pedon: Cecil sandy loam—forested. (Colors are

for moist soil unless otherwise stated.)

Oi – 50 to 0 mm (2 to 0 in); very dark grayish brown

(2.5Y 3/2) partially decayed leaves and twigs. 0 to

75 mm thick (0 to 3 in).

A – 0 to 50 mm (0 to 2 in); dark grayish brown (10YR

4/2) sandy loam; weak medium granular structure;

very friable; many fine roots; strongly acid; clear

wavy boundary. 50 to 200 mm thick (2 to 8 in).

E – 50 to 175 mm (2 to 7 in); brown (7.5YR 5/4) sandy

loam; weak medium granular structure; very

friable; many fine and medium roots; few pebbles

of quartz; strongly acid; clear smooth boundary. 0

to 250 mm thick (0 to 10 in).

BE – 175 to 275 mm (7 to 11 in); yellowish red (5YR

4/8) sandy clay loam; weak fine subangular blocky

structure; friable; few fine and medium roots;

strongly acid; clear smooth boundary. 0 to 200

mm thick (0 to 8 in).

Bt1 – 275 to 77 mm (11 to 28 in); red (2.5YR 4/8) clay;

moderate medium subangular blocky structure;

firm; sticky, plastic; common thick distinct clay

films on faces of peds; few fine flakes of mica; few

small pebbles of quartz; strongly acid; gradual

smooth boundary.
CHAPTER 2—INVESTIGATION

71

Figure 2-1.—Soil triangle of the basic soil texture classes. (Natural Resources Conservation Service)
EARTH MANUAL

72

Bt2 – 700 to 1000 mm (28 to 40 in); red (2.5YR 4/8)

clay; moderate and weak medium subangular

blocky structure; firm; sticky, plastic; common thin

clay films on faces of peds; few to common fine

flakes of mica; strongly acid; gradual smooth

boundary. [Combined thickness of the Bt horizon

is 600 to 1200 mm (24 to 48 in).]

Bt3 – 1000 to 1275 mm (40 to 50 in); red (2.5YR 5/8)

clay loam; common medium distinct strong brown

(7.5YR 5/6) mottles; weak medium subangular

blocky structure; friable; few thin distinct clay films

on vertical faces of peds; common fine flakes of

mica; strongly acid; gradual smooth boundary.

175 to 500 mm thick (7 to 20 in).

C – 1275 to 1900 mm (50 to 75 in); mottled red (2.5YR

5/8), strong brown (7.5YR 5/8), and pale brown

(10YR 6/3) loamy saprolite of gneiss; common

pockets of clay loam; massive; friable; common

fine flakes of mica; strongly acid.

Type Location: Note. – The county, state, and detailed

directions are given to locate the particular parcel surveyed.

Agricultural soil classifications used for engineering

purposes are of limited value. Information of this type is

qualitative rather than quantitative; but, if carefully

evaluated, agricultural soil classifications can often be used

to advantage in the reconnaissance stage and in planning

subsurface exploration. Additional information of how soil

surveys are made is covered in the Soil Survey Manual [9],

an in-house publication of the Natural Resources

Conservation Service.

The agricultural soil survey report is designed to provide

information useful to the farmer and to the agricultural

community. However, in addition to the soil maps and soil

profile descriptions contained in these reports, other

valuable information is included. The reports discuss: 

 ̆ topography,

 ̆ ground surface conditions,

 ̆ obstructions to movement on the ground,

 ̆ natural vegetation,

 ̆ size of property parcels,

 ̆ land utilization,

 ̆ farm practice and cropping systems,

 ̆ meteorological data,

 ̆ drainage,

 ̆ flood danger,

 ̆ irrigation,

 ̆ water supply and quality,

 ̆ nearness to towns, roads, and railroads,

 ̆ electric power, and 

 ̆ similar data.

2-3. Remote Sensing Techniques.&

a. General&Remote sensing is defined as the act of

gathering data concerning the earth' s surface without

coming into contact with it. Remote sensing is performed

using devices such as cameras, thermal radiometers,

multispectral scanners, and microwave (radar) detectors.

Engineering and geologic interpretation of remotely sensed

data may be simple or complicated, depending on the nature

of the data and the objective of the study. Remote sensing

is a tool which makes some tasks easier, which enables

some tasks to be performed that could not otherwise be

accomplished, but which may be inappropriate for other

tasks. Depending on the situation, remote sensing may be

extremely valuable or totally inappropriate. Some remote

sensing interpretations can be used directly and with

confidence; but for most applications, field correlations are

essential to establish reliability. Appropriate specialists

should be consulted when evaluating situations to determine

if remote sensing methods can provide useful data.

b. Nonphotographic.&

1. Scanners.&Electronic sensors are used that have

less spatial resolution than photographs, but which can

obtain a variety of spectral data and thus allow a wide

variety of image processing and enhancement techniques.

Scanners can be either airborne or satellite.

2. Video.&A television type system is used. Video

systems still have lower spatial resolution than photographic

cameras, but provide products more quickly and are

excellent for reconnaissance type work. They are highly

useful for mapping and monitoring linear features such as

rivers and canals.

c. Resolution.&

1. Spatial.&The sharpness of an image and the

minimum size of objects that can be distinguished in the

image are a function of spatial resolution.

2. Spectral.&The width of a part of the

electromagnetic spectrum is the spectral resolution. Certain

portions of the electromagnetic spectrum, including the

visible, reflective infrared, thermal infrared, and microwave

bands, are useful for remote sensing applications. Materials

have spectral signatures and distinctive absorptive and 
CHAPTER 2—INVESTIGATION

73

reflective spectral characteristics which allow them to be

recognized. Given sufficient multispectral data, digital

image processing can produce unique spectral signatures to

be identified. Instrument limitations, cost limits on

computer processing, or lack of spectral contrast may

preclude unambiguous identification of some materials.

d. Photography.&Photography provides the best

spatial resolution, but less flexibility in spectral data

collection and image enhancement.

1. General.&Several types of aerial photographs are

available. An aerial photograph is a picture of the earth' s

surface taken from the air. It may be a vertical photograph

or an oblique photograph more or less inclined. High

oblique photographs include the horizon; low obliques do

not. The vertical photograph is commonly used for

topographic mapping, agricultural soil mapping, vegetation

mapping, and geological interpretations.

2. Panchromatic.&Panchromatic photography

(black and white) records images essentially across the

entire visible spectrum. In aerial photography, blue is

generally filtered out to reduce the effects of atmospheric

haze.

3. Natural Color.&Images are recorded in natural

visible colors. In addition to black and white aerial

photographs available as contact prints, color photography

can be obtained either as positive transparencies or opaque

prints, black and white infrared, or color infrared. By using

appropriate film and filters, photography may be obtained

ranging from ultraviolet to near infrared.

4. Multispectral.&Photographs acquired by multiple

cameras simultaneously recording different portions of the

spectrum can enhance interpretation. Multiband cameras

employing four to nine lenses and various lens, filter, and

film combinations make possible photography within narrow

wavelength bands to emphasize various soil, moisture,

temperature, and vegetation effects to aid photo

interpretation.

Except where dense forest cover obscures large areas, aerial

photographs reveal every natural and human endeavor on

earth within the resolution of the photographic system.

Relationships are exposed which could not be detected on

the ground under normal or routine surface investigation.

Identification of features shown on a photo is facilitated by

stereoscopic examination. Knowledge of geology and of

soil science will assist in interpreting aerial photographs for

engineering uses. Aerial photographs are often used for

locating areas to be examined and sampled in the field.

Virtually the entire United States has been covered by aerial

photography. An index map of the United States is

available from the USGS and USDA. This map shows

which of seven Government agencies can provide

photographic prints for particular areas. When ordering

photographs, specify: 

 ̆ Contact prints or enlargements, glossy, matte finish,

or Cronapaque 

 ̆ Location should be given by range, township, and

section, latitude and longitude 

 ̆ State and county and the preceding location(s) can be

shown on an enclosed index map of the area.

 ̆ Where possible, use the airphoto index to determine

project symbol, film roll number, and exposure

number to expedite the request. 

 ̆ Stereoscopic coverage should be requested for most

uses.

Aerial mosaics covering some of the United States are also

available. A mosaic is an assemblage of individual aerial

photographs fitted together to form a composite view of an

entire area of the earth. An index map showing the

availability of aerial mosaics of the United States, including

the coverage and the agencies holding mosaic negatives, is

available from the USGS Map Information Office.

Equipment is commercially available to produce

orthophotographs that have a uniform scale and from which

radial and relief displacement due to topography have been

removed. Orthographs overprinted with contour lines can

be acquired, if desired.

Aerial photograph interpretation of earth materials and

geologic features is relatively simple and straightforward,

but experience is required. Diagnostic features include

terrain position, topography, drainage and erosional

features, color tones, and vegetation cover. Interpretation

is limited mainly to surface and near-surface conditions.

Special cases arise, however, where features on a

photograph permit reliable predictions to be made of deep,

underground conditions. Although interpretation can be

rendered from any sharp photograph, resolution is a limiting

factor because small-scale photographs limit the amount of

detailed information that can be obtained. The scale of 1:

20,000 is satisfactory for some engineering and geologic
EARTH MANUAL

74

Figure 2-2.—Rock strata illustrating folding in sedimentary rocks. (A) Satanka

formation, (B) Lyons formation, (C) Morrison formation, and (D) Lower and Middle

Dakota formation. (U.S. Forest Service)

interpretation of surface materials. Small-scale photographs

are used for highly detailed work such as for reservoir

clearing estimates and for geologic mapping of damsites and

reservoir areas.

Aerial photographs can be used to identify many terrain

types and landforms. Stereoscopic photograph inspection of

regional topography, local terrain features, and drainage

conditions usually will suffice to identify the common

terrain type. This permits the possible range in soil and

rock materials to be anticipated and their characteristics to

be defined within broad limits.

Geologic features that may be highly significant to the

location or performance of engineering structures can often

be identified from aerial photographs. In many instances,

these features can be more readily identified on an aerial

photograph than on the ground. However, aerial

photograph interpretation is applicable only to those features

that develop recognizable geomorphic features such as

surface expressions such as drainage patterns, old river

channels, and alignment of ridges or valleys. Joint systems,

landslides, fault zones, lineations, folds, and other structural

features are sometimes identified quickly in an aerial

photograph, whereas it may be difficult to find them on the

ground. The general attitude, bedding, and jointing of

exposed rock strata, as well as the presence of dikes and

intrusions, can often be seen in aerial photographs. The

possibilities of landslides into open cuts and of seepage

losses from reservoirs can be assessed.

Figures 2-2 and 2-3 are examples of identifiable geologic

features determined from aerial photographs by an

experienced interpreter using stereoscopic procedures.

5. Color Infrared.&Images use part of the visible

spectrum and part of the near infrared, but resultant colors

are not natural. Infrared film is commonly used and is less

affected by haze than other types.

Other remote sensors use thermal, infrared, microwave, and

radar wavelengths. Such phenomena as differences in the

earth' s gravity and magnetic properties may be measured to

afford additional interpretive tools.

e. Thermal Infrared Imagery.&Thermal infrared

systems create images by scanning and recording radiant

temperatures of surfaces. Some characteristics of thermal
CHAPTER 2—INVESTIGATION

75

Figure 2-3.—Sinkhole plain indicating deep plastic soils over cavernous 

limestone, developed in humid climate. (Natural Resources Conservation Service)

image data produce digital image data which enable

computer image processing, and others are unique to

thermal infrared images which makes them valuable

interpretive tools.

Thermal infrared imagery can be analyzed using

conventional photo interpretation techniques in conjunction

with knowledge of thermal properties of materials and

instrument and environmental factors that affect data.

Where thermal characteristics of a material are unique,

thermal infrared imagery is easily and confidently

interpreted. Vegetation patterns can be distinguished and

can relate to subsurface conditions such as seepage beneath

or through an existing dam. However, thermal

characteristics of a material can vary with ambient

temperature, moisture content, differential solar heating, and

topography, and make interpretation difficult and

ambiguous.

f. Multispectral Scanner Imagery (MSS).&MSS

images are a series of images of the same target, acquired

simultaneously in different parts of the electromagnetic

spectrum. The MSS images are an array of lines of

sequentially scanned digital data, as opposed to the

simultaneously exposed area of a photograph. They may

have unique distortions and may or may not have high

resolution and information content. Scanner systems consist

of scanning mechanisms, spectral separators, detectors, and

data recorders.

Because a digital image is actually an array of numerical

data, the image can be manipulated by a computer for a

variety of purposes. Geometric distortions caused by sensor

characteristics can be removed, or distortions can be

introduced if desired. Computer processing can be used to

precisely register a digital image to a map or another image.

Various techniques can be used to improve image quality

and interpretability. Various types of data (for example,

thermal and visible imagery or a digital image and digitized

gravity data) can be merged into a single image. Subtle

information, difficult to interpret or even to detect,

sometimes can be extracted from an image by digital

processing.

1. Airborne MSS Imagery.&Image characteristics.&A number of different airborne MSS systems are

available with various spatial and spectral characteristics.

Some systems are capable of recording 10 or more spectral

bands simultaneously, ranging from ultraviolet to thermal

infrared. Typical digital image processing techniques are

used. The size of data sets and the number of separate

spectral bands on some airborne MSS systems may require
EARTH MANUAL

76

data consolidation or careful selection of data subsets for

special processing. Typically, interpretation involves

normal photointerpretive techniques along with knowledge

of spectral characteristics and the data manipulations

applied.

Advantages and limitations.&High resolution can

be obtained; and with proper band selection and processing,

even geochemical information may be possible from

imagery. Depending on complexity of the geology or other

features and on the size of the area studied, the necessary

digital processing can become costly and may require

considerable experimentation to obtain satisfactory results.

2. Satellite MSS Imagery.&Landsat is the

U.S. satellite for civilian remote sensing of Earth' s land

surface. The Landsat MSS records four broad bands at 80-

meter resolution. Though primarily oriented toward

agricultural applications, it has proved useful for some

geologic applications. The current Landsat is equipped with

a thematic mapper (TM), which enhances spatial and

spectral resolution compared to the MSS. The TM records

seven narrow bands at 30-meter resolution and is more

useful for geologic and geotechnical engineering

applications.

A French satellite, Satellite Pour l’Observation de la Terre

(SPOT), provides panchromatic imagery with up to

10-meter spatial resolution and MSS imagery at 20-meter

resolution and is capable of stereo imaging.

Satellite imagery provides a synoptic view of a large area,

which is valuable for regional studies, but the limited

resolutions currently available restrict its value for

engineering geology and geotechnical work.

g. Radar Imagery.&Radar is an active remote sensing

method (as opposed to passive methods like photography

and thermal infrared) and is independent of lighting

conditions and cloud cover. Some satellite radar imagery is

available, but like Landsat, it is more useful for regional

geologic studies than for engineering geologic or

geotechnical application. Side-looking airborne radar

(SLAR) produces a radar image of the terrain on one side of

the airplane carrying the radar equipment (equivalent to a

low-oblique airphoto). This imagery is useful when

studying regional geologic faulting patterns and can be used

to assist in determining specific sites for detailed fault

investigations. 

Image characteristics.&Radar imagery has some

unusual distortions which require care when data are

interpreted. Resolution is affected by several factors, and

the reflectivity of target materials must be considered.

Analysis and interpretation of radar imagery require

knowledge of the imaging system, wave length polarization,

look angle, and responses of target materials.

Advantages and disadvantages.&Radar can

penetrate clouds and darkness and, to some extent,

vegetation or even soil. Distortions and resolution can

complicate interpretation, as can a lack of multispectral

information.

h. Applications to Geotechnical Engineering and

Geology.&In general, the most useful form of remote

sensing for geotechnical applications is aerial photography

because of its high resolution, high information content, and

low cost. Various scales of aerial photographs are valuable

for regional studies and site studies, for both detection and

mapping of a wide variety of geologic features of

importance to engineering investigations.

Application of other forms of remote sensing to engineering

work depends on the nature of the problem to be solved and

the characteristics of site geology or other features. Some

problems can be best solved using remote sensing; for

others, remote sensing is of no value. In some cases, the

only way to determine if remote sensing can be useful is to

try it.

i. Availability of Imagery.&The entire United States

has been imaged by the Landsat MSS. Partial Landsat TM

and SPOT coverage of the United States is also available.

The SLAR coverage of a portion of the United States is

available. Other types of imagery are also available, but

generally only for limited areas. 

j. Mission Planning.&Numerous factors make

planning a nonphotographic mission more complicated than

planning for a conventional aerial photographic mission.

Remote sensing mission planning should be done by, or in

consultation with, an expert in the field.

The cost of remote sensing data acquisition can be relatively

accurately estimated. However, cost of interpretation is a

function of the time and image processing required; this cost

is difficult to estimate accurately. Some forms of data are

inexpensive to acquire and require little processing to be

useful. Other forms may be costly to acquire and may or

may not require considerable processing. 

Two excellent reference books by Sabins [10] and Siegal

and Gillespie [11] deal with remote sensing. A thorough
CHAPTER 2—INVESTIGATION

77

treatment of remote sensing by Colwell [12] includes a

287-page chapter on geological applications with numerous

color images.

2-4 Site Investigations and Land Form Types.&

a. General.&Surface investigations are generally

limited to geologic mapping of water resource development

sites, outlining areas of potential construction materials, and

assessing hazardous waste remedial sites. However, useful

relationships exist between surface land forms and the

subsurface soil and rock conditions. The ability to

recognize these landforms on topographic maps, on aerial

photographs, and during preliminary site reconnaissance,

when combined with a geologic knowledge of the area, is

very important when characterizing a site and when locating

potential sources for construction materials.

Soils in their geologic context are defined by their

mechanism of deposition which, in turn, usually results in

distinct landforms (physiographic surface expressions). A

good representation of the subsurface soil engineering

characteristics can be made by detailed surface mapping.

However, a complete understanding of subsurface soils

conditions can only be obtained through careful subsurface

investigations. Knowledge of surface conditions can be

used to economically lay out a subsurface investigation

program.

Most water resource development projects are sited in river

valleys containing a variety of soil (surficial deposits).

Typically, valley sedimentation consists of alluvial channel,

flood plain, and terrace deposits. Slope wash and colluvial

materials, landslides, and alluvial fans are often found on

the valley slopes but can also impinge upon the valley floor.

Side ridges, especially where auxiliary structures may be

sited, often contain residual soils forming in place. Other

types of surficial deposits that form structural foundations at

many Reclamation Projects are glacial, windblown (eolian),

and lacustrine in origin. The physical description and

properties of the types of soils most common to water

resource development projects are described below, and

some broad generalizations are made about the engineering

characteristics and applications of these soil types associated

with their particular landforms.

b. Alluvial Deposits.&These deposits constitute the

largest group of transported soils. Alluvial deposits are

stream transported and are usually bedded or lenticular, but

massive deposits may also occur. The different types of

sedimentary processes, combined with different source

materials and the energy required during the transportation

process, leads to materials ranging from well to poorly

graded.

1. Stream Channel Deposits.&Typically, high

energy stream channel deposits contain sands, gravels and

cobbles. The size and extent of channel deposits can vary

greatly. Channel deposits may comprise the entire valley

floor and may be quite deep. In a wide valley, a

meandering or braided stream may distribute channel

deposits widely, resulting in thin, widespread layers or very

irregular lenses of sand and gravel. These deposits can be

poorly to well graded and can provide sources of filter

materials and concrete aggregate. Stream channel deposits

represent paths of potential high seepage. Variation in soil

properties, seepage, consolidation, and possible low shear

strengths may make them undesirable foundations for water

retention structures. Figure 2-4 shows an aerial view and

topography of river alluvium and terrace deposits.

The presence of a high water table is often a major difficulty

in using channel deposits for borrow. When borrowing of

material is being considered from a river deposit

downstream from a water retention structure, such

operations may change the tailwater characteristics of the

stream channel, and the spillway and outlet works may have

to be designed for the modified channel conditions. 

2. Flood Plain Deposits.&The low gradient sections

of nearly all streams have flood plains. Their surface

expression is usually that of a smooth flat strip of land just

above the stream channel. Clay, silt, and sand are typical

soils of flood plains. Most flood plain deposits were once

carried as sediment load while in the swiftly moving flood

water of a channel (high energy) but settled out on the flood

plain when water overflowed the channel and slowed (lower

energy). In broad valleys, flood plains may be miles wide

and may be flooded on an annual or more frequent basis.

Flood plain deposits are often the source of the impervious

zones for water retention structures.

3. Terrace Deposits.&Terraces are located above

the flood plain (see fig. 2-4). They are usually elongate

deposits along the streamcourse and have either a flat or a

slight downstream dip on their upper surface. They also

have well-delineated steep slopes, downward from the

terrace on the stream side and upward on the valley wall

side of the terrace. Along degrading streams, the alluvium

in terrace deposits generally has the same size range as

adjacent channel deposits. Terrace deposits can be sources

of sand and gravel, but often are of limited extent and may

require washing and processing.
EARTH MANUAL

78

Figure 2-4.—Aerial view and topography of stream deposit showing river alluvium and 

three levels of gravel terraces. (U.S. Geological Survey)
CHAPTER 2—INVESTIGATION

79

Figure 2-5.—Aerial view and topography of an 

alluvial fan, a potential source of sand and gravel. 

(U.S. Geological Survey)

4. Alluvial Fan Deposits.&Alluvial fans are

typically gently sloping, fan-shaped masses of soil deposited

in locations where an abrupt decrease in stream gradient

occurs (see fig. 2-5). Large alluvial fans, many miles in

width and length, occur along mountain fronts, where steep

streams from mountain drainages spread out on relatively

flat valley floors. Aggrading stream channels migrate

laterally along the surface of the fan as temporary channels

are both eroded and filled. Much mixing of the soils may

result, and lenticular, poorly to well-graded materials are

typical laterally across the fan. In contrast, there is a

longitudinal grading from the head to the toe of the fan. 

Coarser material is deposited first and found on the steeper

slopes at the head of the fan, while the finer material is

carried to the outer edges. Grading of a fan depends on a

combination of source material, water velocity, and slope.

In arid climates, where mechanical weathering generates

coarser particles with associated steeper slopes, the fans

may be composed largely of rock fragments, gravel, sand,

and silt. If the source produces fine materials, large

deposits of silty sands or sandy silts may occur. In humid

climates, where chemical weathering tends to generate finer

particles and landforms have flatter slopes, the alluvial fan

can contain much more sand, silt, and clay. In the Western
EARTH MANUAL

80

United States, all types of construction materials are found

in alluvial fan deposits, but the percentages of clays are

generally small, and when used for impervious zones in

water retention structures, may be erodible.

c. Slope Wash or Colluvial Deposits.&Slope wash is

a general term referring to loose, heterogeneous soils

deposited by sheet wash, or slow, continuous downslope

creep, usually collecting at the base of slopes or hillsides.

Angular rock fragments are locally very common. The

types of slope wash soils generally reflect the bedrock of the

slopes on which they occur; that is, clays occur on slopes

with shale bedrock, and sandy deposits on slopes with

sandstone bedrock. Slope wash may typically vary from

thin deposits high on a slope to tens of feet thick near the

base of the same slope and are often of low density. Slope

wash deposits, where relatively thick, can provide good

material for the impervious zones of water retention

structures. If rock fragments are too large and numerous,

these soils may be undesirable for construction purposes.

Unless located within the confines of the reservoir, shallow

slope wash deposits often make undesirable borrow sources

due to the small volumes of material available.

d. Lacustrine Deposits.&Lacustrine deposits, or

lakebed sediments, are the result of sedimentation in still

water. Lacustrine deposits are likely to be fine-grained silt

and clay except near the deposit margins where currents

from tributary streams may have transported coarser

materials. Frequently, lacustrine stratification is so fine that

the materials appear to be massive in structure. However,

a color and grain size difference usually exists between

successive beds, and the layered structure often can be

observed by drying a slice from an undisturbed sample.

Lacustrine soils are likely to be impervious, compressible,

and low in shear strength. Their principal use in water

development projects has been for impervious cores in

earthfill dams, for impervious linings of reservoirs and

canals, and for low embankments. These soils often have

moisture contents exceeding optimum but can be used with

careful moisture control. Treatments may include

excavation, transport to drying pads, and discing to

accelerate the sun' s drying action. In extreme cases, drying

can be accomplished using drying kilns if only small

quantities are required. 

Generally, lacustrine deposits provide poor foundations for

structures. The engineering characteristics of these deposits

may be so questionable that special laboratory and field

testing may be required even during the reconnaissance

design stage. Close coordination between the exploration

and design teams regarding soil sampling and testing is

imperative whenever structures must be founded on lake

sediments.

e. Glacial Deposits.&Glacial soils produced and

deposited by Pleistocene continental ice sheets are prevalent

in a wide area across the Northern United States. Alpine or

mountain glaciation has also produced glacial soils in the

Rocky Mountains, the Sierra Nevada, the Cascades, and

other high western mountain ranges and volcano flanks.

Glacial modification of valley shapes and deposition of

glacial soils are important to the siting, design, and

construction of many water retention structures. Material

deposited by glaciers is generally divided into two classes:

(1) tills, which are deposited directly from or by the glacier;

and (2) outwash or glaciofluvial deposits, which are

deposited by water issuing from the glacier. Tills and

outwash deposits are often mixed in varying proportions,

and generalizations concerning the soil characteristics of any

glacial land form are difficult to make. A separate

classification is made for deposits laid down in lakes related

to glaciation. These lake-related deposits are

glaciolacustrine soils and are similar to lacustrine deposits.

1. Tills or Glacial Deposits.&Tills are glacial soils

deposited directly from glaciers without subsequent

reworking by outwash. Tills often form distinctive

landforms and are often described as soils of landforms such

as morainal deposits. Tills are predominantly unsorted,

unstratified soils consisting of a heterogeneous mixture of

clay, silt, sand, gravel, cobbles, and boulders ranging

widely in size and shape. The gradation and types of rock

fragments and minerals found in till vary considerably and

depend on the geology of the terrain over which the ice

moved and the degree of postdepositional leaching and

chemical weathering. Certain glacial tills may be used to

produce impervious materials with satisfactory shear

strength, but removal of cobbles and boulders is necessary

so that the soil can be compacted satisfactorily. Where till

deposits have been overridden by ice, the resulting high, inplace density may make them satisfactory foundations for

many hydraulic structures. Typical landforms often

composed wholly or partially of till are:

 ̆ Till plain or ground moraine, which has a flat to

undulating surface.

 ̆ Terminal or end moraine (see fig. 2-6), usually in the

form of a curved ridge, convex downstream, at right

angles to the direction of ice advance and which

marks the maximum advance of a glacier.
CHAPTER 2—INVESTIGATION

81

 ̆ Lateral or medial moraines, or till ridges usually

formed parallel to the direction of ice movement and

consisting of material carried on the surface of the

glaciers sides and center (see fig. 2-6).

2. Outwash or Glaciofluvial Deposits.&The

meltwater from glaciers produces streams of water which

wash out and carry away material of all sizes that have been

produced by glacial abrasion. The material is deposited in

front of or beyond the margin of an active glacier. In

contrast to tills, outwash deposits are usually sorted and

poorly stratified by stream action. Outwash deposits consist

of the same range of sizes, from fines to boulders, as tills.

Some landforms created by outwash deposits are outwash

fans, outwash plains, eskers, and kames. An outwash fan

is a fan-shaped accumulation of outwash deposited by

streams beyond the front of an active glacier. An outwash

plain is formed by numerous coalescing outwash fans.

Eskers, remnants of the beds of glacial streams that once

flowed under the ice, are winding ridges of sand, gravel,

and cobbles that are excellent sources of pervious materials,

filter materials, and concrete aggregate. Kames are mounds

or short ridges that are composed of materials similar to

those of eskers and that were typically deposited by

subglacial streams at the margins of glaciers.

f. Eolian Deposits.&Eolian soils have been

transported and deposited by the wind. Eolian soils are

composed mainly of silt and/or sand-sized particles. They

very often are of low density, have low bearing strength,

and are generally poor foundations for typical water

resource structures. When used as foundations, detailed

explorations defining the extent and physical properties of

the eolian deposits are necessary. Density data are very

important, and this information, combined with Atterberg

limits data, can be used to assess collapse potential of the

soils. The most common eolian soils are loess and dune

deposits.

1. Loess.&Large areas of the Central and Western

United States, especially the Mississippi and Missouri river

drainage system, the High Plains, the Snake River Plain, the

Columbia Plateau, and some of the Basin and Range valleys

are covered with loess. Figure 2-7 shows typical loessial

topography by map and aerial photograph. These deposits

have a remarkable ability for standing in vertical faces,

although local sloughing and erosion occur with time.

Loess consists mostly of particles of silt or fine sand, with

a small amount of clay that binds the soil grains together.

Loessial deposits may contain sandy portions which are

lacking in binder and are very pervious. Undisturbed loess

has a characteristic structure marked by remnants of small

vertical root holes that makes it moderately pervious in the

vertical direction. Figure 2-8 shows the structure of loess.

Although of low density, naturally dry loessial soils have a

fairly high strength when dry because of the clay binder.

This strength, however, may be readily lost upon wetting,

and the soil structure may collapse. When compacted,

loessial soils are impervious, moderately compressible, and

of low cohesive strength, and they exhibit low plasticity.

Usually, loessial soils plot in the ML group or the

borderline ML/CL and SM/ML groups of the Unified Soils

Classification System [13, 14, 15]. Figure 1-22 shows a

steep cut face in loess.

2. Dune Deposits.&Although not as widespread as

loess, dune deposits are common in some Western States.

Although active dunes are easily recognizable because of

their exposed soils and typical elongated ridge shape that is

transverse to prevailing winds or a crescent shape that is

convex upwind, inactive dunes may be covered with

vegetation or detritus so that their extent is not immediately

obvious. Dune deposits are usually rich in quartz minerals

and uniform in grain size&usually in the range of fine- to

medium-grained sand. These sands have no cohesive

strength, moderately high permeability, and moderate

compressibility, although density and associated

compressibility often vary widely. Generally, dune sands

fall in the SP group of the Unified Soil Classification

System. In their natural state, dune sands are extremely

poor materials on which to site hydraulic structures. They

erode easily in canal prisms and are generally poor

foundations for footings. Cut slopes in dune sands will

stand only at the angle of repose or flatter, whether in the

wet or dry state. If excavated underwater, slopes will flow

(run) until the angle of repose is reached. Dune deposits are

usually subject to liquefaction and seepage problems where

they are present in the foundation of existing dams.

However, dune deposits can be a good source of material

for uniform-grain-size filters.

g. Residual Soils.&Residual soils are derived from inplace chemical and mechanical weathering of parent rock,

and differ from all of the other soils discussed in this section

in that they are not transported and are not associated with

unique landforms. The nature of these soils depends on the

texture, structure, and mineralogy of the parent rock,

climate, rate of surface erosion, ground-water table, and

local vegetation. Because of the many factors affecting the

development of residual soils, at any one site there may be

great variability laterally and vertically.
EARTH MANUAL

82

Figure 2-6.—Aerial view and topography of terminal moraine of continental

glaciation. (Natural Resources Conservation Service)
CHAPTER 2—INVESTIGATION

83

Figure 2-7.—Aerial view and topography of loess identified by smooth silt ridges; usually parallel, right-angle drainage

patterns; and steep-sided, flat-bottomed gullies and streams. (Natural Resources Conservation Service)
EARTH MANUAL

84

Figure 2-8.—Photomicrograph showing typical open structure of silty loess.
CHAPTER 2—INVESTIGATION

85

Large regions of the United States are underlain by residual

soils, and many dams are both composed of and founded on

them. These soils typically have a natural vertical profile

consisting of an A-Horizon at the top, with B- and

C-Horizons progressively below. The A-Horizon is usually

very thin (a few inches), relatively sandy (clays are moved

to the underlying horizon by rainwater percolation), and

high in organic material. The B-Horizon is relatively

clayey. Its original mineral content, especially the silicate

minerals, is highly weathered, and there is no trace of

parent rock structures. The C-Horizon contains varying

percentages of unweathered mineral grains of the parent

rock and shows varying degrees of the parent rock

structure.

When residual soils are used for the foundations and zones

of embankment dams, the designer should consider that the

B-Horizon is usually less permeable than the C-Horizon.

Failure to take the cutoff trench through the C-Horizon and

the use of some C-Horizon material in impermeable zones

have resulted in seepage both through and under dams.

Relict joints, foliation, bedding planes, and faults in

C-Horizons have resulted in concentrated seepage with

subsequent foundation piping. These same relict structures

may also cause weak, potential failure planes in dam

foundations.

Because the type of parent rock has a pronounced influence

on the character of residual soils, the rock type should

always be determined. The degree to which alteration has

progressed largely governs strength characteristics.

Laboratory testing, including testing for dispersion, is

required if the material appears questionable or when

important or large structures are planned. Petrographic

analyses for identification of clay minerals in residual soils

is required for an understanding of their engineering

properties.

A distinguishing feature of many residual soils is that

individual particles in place are angular but soft. During

construction, handling of the material may appreciably

reduce the grain size so that the soil, as placed in the

structure, may have entirely different characteristics than

shown by standard laboratory testing of the original soil.

Decomposed granites, which at first appear to be free

draining granular materials, may break down when

excavated, transported, placed, and compacted. As a result,

this material may become semipervious to impervious.

Special laboratory and field testing programs are often

required to determine changes that might occur in the

engineering characteristics of residual soils. During this

testing, special attention should be paid to soil breakdown

by drying, by impact compaction, and by kneading

compaction action. Full scale field compaction test sections

are sometimes appropriate before proper decisions can be

made regarding the use of residual soils. 

2-5. Subsurface Investigations.&

a. General.&Subsurface geotechnical exploration is

performed primarily for three purposes: (1) to determine

what distinct masses of soil and rock exist in a foundation or

borrow area within the area of interest; (2) to determine the

dimensions of these bodies; and (3) to determine their

engineering properties.

In the engineering evaluation of a foundation or borrow

area, soil structure should be delineated by means of profiles

or plans into a series of masses or zones within which soil

properties are relatively uniform. Soils having variable

properties can be evaluated, provided the nature of the

variation can be defined. Determination of dividing lines

between what may be considered uniform soil masses must

usually be done on the basis of visual examination and

requires considerable judgment. The soil classification

system described in chapter 1 is a satisfactory guide for

consideration of soils in a disturbed state. For evaluating

soils in the undisturbed state, additional qualifying factors

required are in-place water content, density, firmness, and

stratification. Color and texture are also helpful in

delineating soil masses of uniform characteristics.

Occasionally, the only uniformity found in a soil deposit is

its heterogeneity. However, by exercising careful analysis,

a pattern may be found in the soil mass for use in

geotechnical analysis.

The dimensions of these masses of soil are determined by

methods analogous to those used in surface surveying such

as making cross sections or by contouring the upper and

lower surfaces (or isopachs). The method used depends

somewhat on the type of structure involved. Point

structures (buildings) or line structures (canals, pipelines,

and roads) are best visualized by cross sections; massive

structures (dams) are best visualized by topographic plan

maps in addition to cross sections. 

Unfortunately, the problem of locating measuring points or

the "breakpoints" of buried surfaces is difficult because the

subsurface cannot be seen, and the cost of investigating the

entire area with a grid of test holes is usually great. The

normal procedure used for an investigation is to begin with

an estimation of the breakpoints' locations based on a

geologic interpretation of the subsurface. An initial series

of test borings&supplemented by data from geophysical

surveys&can be used for preliminary delineation of buried

surfaces. Breakpoint locations can be further defined by
EARTH MANUAL

86

locating additional test borings using successive

approximations after considering geophysical data. A grid

system of test holes is normally used only on large or

critical borrow areas and on foundations (for large earth

dams) where subsurface irregularities cannot be established

by other means. Simple, inexpensive penetration tests such

as the electronic cone penetrometer test can provide useful

information which can be used for more detailed delineation

of subsurface irregularities.

b. Point Structures.&For structures such as small

buildings, small pumping plants, transmission towers, and

bridge piers, a single test hole is often adequate. Larger

structures may require more test holes. When the exact

location of a structure is dependent on foundation

conditions, the number of test holes required should be

increased. Two or three test holes are used for preliminary

exploration to establish general foundation conditions; the

investigation requirement can usually be reduced for later

stages. Figure 2-9 shows suggested depths of preliminary

exploratory holes for various point structures. Figure 2-10

is an example of a soil profile at a pumping plant site.

c. Line Structures.&Exploration requirements for the

foundations of canals, pipelines, and roads vary

considerably according to the size and importance of the

structure and according to the character of the ground

through which the line structure is to be located. Spacing of

holes or other explorations will vary, depending on the need

to identify changes in subsurface conditions. Where such

structures are to be located on comparatively level ground

with uniform soils such as the plains areas, fewer holes

along the alignment may suffice for foundation investigation

requirements. In certain instances, special investigations

may be required such as test pits and in- place densities

measurements for pipelines or hand cut block samples to

study collapse potential in areas of low density soils.

Test hole requirements are quite variable for design and

specifications purposes on major structures; landslides, talus

and slopewash slopes, and alluvial fans require thorough

exploration. Usually, a test hole at the point of highest fill

or at valley bottom is needed. Additional off-line holes may

be required for all of these features, depending on

topographic, geologic, and subsurface conditions. During

investigations, special consideration should be given to line

structure excavation such as dewatering requirements and

cut slope stability. Water levels should be monitored in test

holes for a sufficient length of time to establish seasonal

ground-water level variation. Dewatering design parameters

must be anticipated throughout investigations. Useful data

regarding permeability can be obtained from laboratory

gradation tests of critical soils and from borehole

permeability tests. Excavations through soft, fine-grained

soils or through wet areas should be investigated more

thoroughly. Shear strength data may be required in certain

critical excavation areas. 

When major, costly features are involved, detailed

explorations are required even for feasibility estimates.

Figure 2-11 shows the suggested minimum depths of

exploratory holes for major line structures. Greater depths

are sometimes required to determine the character of

questionable soils. Figure 2-12 is an example of a geologic

profile along the centerline of a proposed pipeline.

d. Damsites.&Sites for dams are initially selected

because the valley at that location is narrower than at other

places or the abutment and foundation conditions appear

superior. The exploration program must be directed toward

determining the detailed subsurface conditions. Study of

surface geology will aid in deciding locations for initial test

holes. In some cases, a surface geologic map, together with

four or five test holes and to a depth reaching a competent

and impervious formation, will delineate conditions well

enough to proceed with a feasibility design of a dam. A line

of test holes along the potential dam axis, the outlet works,

and spillway structure are also important. Some of the holes

may be located to satisfy more than one requirement.

A dam forms only a small part of a reservoir. To assure the

adequacy of a reservoir, exploration at considerable

distances from the damsite is frequently necessary to locate

possible routes of water loss and to identify potential

landslide conditions. The entire reservoir rim should always

be carefully inspected for landslide potential, rock toppling,

areas of high water loss, or other conditions which might

jeopardize the safety or economics of the project. Data

needed for reservoir studies require detailed investigations

and thorough surface geologic mapping as described in the

Design of Small Dams [16].

As the design progresses, additional boreholes in the valley

floor, in dam abutments, and at locations of appurtenant

structures will be required. The number, spacing, angle,

diameter, and depth of these holes depend not only on the

size of the dam and structures, but also on type and

complexity of the foundation. Usually, this exploratory

program is prepared by the exploration team which includes

representatives from both the design and field offices.

Figure 2-13, an example of a generalized geologic section

for a damsite, shows exploratory holes for an earth dam.
CHAPTER 2—INVESTIGATION

87

Figure 2-9.—Depth of preliminary exploratory holes for point structures.
EARTH MANUAL

88

Figure 2-10.—Soil profile at a pumping plant.
89

Figure 2-11.—Depth of preliminary exploratory holes for canal, road, and pipeline alignments.
90

Figure 2-12.—Example of a geologic profile along the centerline of a pipeline.
91

Figure 2-13.—Geologic section of a damsite.
EARTH MANUAL

92

e. Tunnels.&The investigation program must be in

balance with anticipated geologic complexities and stage of

study. Design studies may require development of detailed

geologic investigations. Drill holes are required at each

portal area to define the extent and character of overburden

materials and along the alignment where overburden

materials may be pertinent to tunnel design. This is in

addition to geologic and rock mechanics data for tunnel

design. Horizontal boreholes and angle boreholes are often

used to further define soil and rock properties, and

geophysical studies can provide useful supplemental data.

Studies of rock hardness, jointing, and stratification should

be performed to determine the best method of excavation

and for proper tunnel lining and support design.

f. Borrow Areas.&Explorations for borrow areas can

be divided into two types. The first type includes those to

locate a specific kind of material such as:

 ̆ aggregate for concrete,

 ̆ ballast for railroad beds,

 ̆ surfacing and base courses for highways, 

 ̆ filter materials for drains, 

 ̆ blanketing and lining materials for canals or

reservoirs, 

 ̆ riprap materials for dams, and

 ̆ materials for stabilized or modified soils.

The second type is general to define the major kinds of

material available in an area.

The first type of exploration requires locating comparatively

small quantities of material with specific characteristics.

The site should be geologically mapped to determine the

nature and extent of the deposit. Then, either holes are

drilled, test pits dug, or other investigations are performed

in highly probable locations to establish if materials exist

with the required characteristics. When a potential source

is located, supplementary exploration is done to evaluate the

required quantity. This should include at least one test pit

to confirm drill hole data. The limits of the entire deposit

need not be determined; but when exploring for specific

materials for a major specification, an excess of the required

quantity is needed to provide for waste, shrink, swell, or

other unforeseen conditions.

The second type of exploration is performed to locate

comparatively large quantities of material in which

accessibility, uniformity, and workability are as important

as engineering properties. A potential source satisfying

these requirements is first located on the basis of surface

indications. Next, a few holes are drilled or other

investigations are performed to establish that appreciable

depth of material exists; then the area is explored using a

grid of holes or other investigations to establish the volume

available. This should include at least one test pit to

confirm drill hole data. The grid system layout should

provide maximum information with the least number of

holes. Normally for a long, narrow deposit, the section

lines across the deposit can be located quite far apart, but

the holes on these sections should be spaced quite closely.

In a valley, more continuity is likely in the longitudinal

direction than across the valley; exploring this variability is

important. The variability of the deposit will also influence

the number of holes.

Test pits and test trenches should always be a part of an

investigation as they allow for: 

 ̆ Visual inspection of in-place conditions,

 ̆ Verification of data obtained from drill holes or other

investigations, and

 ̆ Determination of in-place density to evaluate shrink

and swell factors.

Additional test holes should be required during construction.

Prior to actual excavation, sometimes test hole spacing is

reduced to 15 or 30 m (50 or 100 ft) near the edges of a

deposit and in deposits where material is variable.

Figure 2-14, an example of a plan and sections, shows

exploration in a borrow area. On canal work, borrow

material is usually taken from areas adjacent to the canal;

and test holes or other investigations for borrow are not

required if canal alignment test holes are spaced closely

enough to ensure availability of satisfactory materials.

g. Selection of Samples.&Laboratory or field tests to

establish engineering properties of a soil deposit may be

required on: (1) soil samples without regard to their inplace condition in the deposit, (2) soil samples in which the

natural in-place conditions are preserved as well as possible,

and (3) soils as they exist in foundations. Laboratory and

field tests are made on soils to determine both the average

engineering properties and the range over which these

properties vary. Because of cost, the procedure used is to

determine by visual examination those samples likely to

have the poorest, median, and best engineering properties

considered critical. In the specifications stage, index tests

are used to select samples for detailed laboratory testing

instead of depending on visual examination.

During construction, samples are collected from the soils

actually used; laboratory tests are performed on a portion of

each sample, and the remainder is stored for detailed testing

should a need arise. Because samples may become damaged

during shipment, storage, or testing, and the exact number
CHAPTER 2—INVESTIGATION

93

Figure 2-14.—Exploration for embankment materials—borrow area location map and typical cross sections.
EARTH MANUAL

94

to be tested cannot be predetermined, the number of samples

collected should be considerably greater than the number

actually considered necessary for testing.

Disturbed samples are collected (see USBR 7000 and 7010)

when natural in-place conditions of the soil are relatively

unimportant, i.e., where the soils will be reworked for use

in the structure. The important element in this type of

sampling is that:

 ̆ Samples are uniform throughout the sampling depth

interval.

 ̆ Separate samples are collected for each change in

material.

 ̆ Samples collected are representative of materials

being investigated.

 ̆ Samples collected show lateral and vertical variations

in material.

If test holes are small, total material is collected from the

hole. In large test holes, a uniform cross-section cutting is

removed from one wall to provide the samples. In some

cases, a specific portion of each stratum is set aside as a

representative sample. Normally, all of the initial

exploratory holes are sampled completely. If the soil

deposits have recognizable uniform characteristics,

intermediate holes may not require sampling. 

Undisturbed samples are collected when foundations are

being evaluated for their capability to support structures or

where it appears that soil in its natural state may possess

special characteristics that will be lost if the soil is

disturbed. Undisturbed samples may be collected solely for:

 ̆ Visual examination of soil structure

 ̆ Determining in-place density 

 ̆ Load-consolidation testing 

 ̆ Shear strength testing 

 ̆ Performing special tests to determine change in

engineering properties as the natural condition is

changed

Many procedures are available for securing undisturbed

samples. The procedures are designed to:

 ̆ best sample different types of soil,

 ̆ secure samples of an soil structure,

 ̆ minimize the amount of disturbance, and

 ̆ reduce sampling costs.

Bureau of Reclamation standard practices include securing

samples from boreholes with:

 ̆ mechanical open end push tube sampling,

 ̆ piston sampling, or

 ̆ continuous double or triple tube rotary drilling and

sampling.

Undisturbed samples are taken also from test pits or open

excavations by carefully cutting out large blocks of material

or by hand trimming a sample into a metal or plastic

cylinder. Hand cut blocks and cylinder samples from

accessible excavations provide the highest quality

undisturbed samples which can be obtained. Details of

undisturbed sampling procedures are given in USBR 7100

and 7105.

h. Field Tests.&Tests made on foundations in the field

may include, but are not limited to, the following tests:

 ̆ in-place density and water content,

 ̆ in-place permeability,

 ̆ standard penetration,

 ̆ cone penetration,

 ̆ pressuremeter,

 ̆ flat blade dilatometer,

 ̆ vane shear,

 ̆ pile driving, and

 ̆ pile loading. 

Foundations for hydraulic structures (dams and canals) are

tested for permeability as a standard procedure.

 ̆ Sometimes, standard penetration tests are made on

soil foundations and used as an index test&

particularly, where bearing strength of the soil is

questionable.

 ̆ Cone penetration tests are useful for delineating

stratigraphy as well as for giving an indication of

bearing capacity.

 ̆ Pressuremeter and dilatometer tests are used to

determine modulus values of soils.

 ̆ Vane tests provide data on in-place shear strength.

 ̆ Pile driving and pile-load tests are made to assess pile

performance.

Because the location of these tests must be closely related to

design requirements, they are required mainly in connection

with specifications stage investigations. Special tests other

than those discussed above are often made in the field. In

many cases, field tests can be performed to produce

engineering properties more economically than laboratory

testing. In some materials and conditions, field tests are

preferred over laboratory techniques. An advantage of field

testing is that the soil tested is at in-place condition under
CHAPTER 2—INVESTIGATION

95

existing stress. Disadvantages are that the test is limited to

a fixed stress path; empirical correlations are required, and

sometimes a physical sample is not retrieved.

2-6. Investigations for Construction Materials.&

a. General.&A sufficient variety of naturally

occurring materials is usually not available in the immediate

vicinity of an earthwork structure to allow development of

the feature except at an excessive cost. 

Often, limited quantities of materials can be economically

obtained that have special, desirable characteristics from

areas at a considerable distance from the site, or an

investigation can be made to determine whether existing

materials can be modified at the site. Such materials might

include:

 ̆ Impervious soils for constructing linings or blankets

 ̆ Sand and gravel for concrete aggregate, filters, filter;

blankets, drains, road surfacing, and occasionally,

protection from erosion; and

 ̆ Rock fragments for riprap or rockfill, filters, filter

blankets, or concrete aggregate.

If the required materials are found in sufficient quantities in

the immediate vicinity of the site, investigating more distant

sources is unnecessary. If there is a deficiency of

impervious materials, pervious materials, or rock in the

immediate area, limited quantities of that deficient material

may come from 40 to 80 km (25 to 50 mi) distant. Past

cases have shown that securing riprap (rock) 320 km

(200 mi) or more distant may be economical. If the haul

distance to a suitable borrow source exceeds about 30 km

(20 mi), design concept changes or modifications to

available materials should be considered. Some

modifications might be:

 ̆ adding bentonite to sandy soils,

 ̆ using cutoff walls, or

 ̆ using soil-cement or precast concrete blocks as

alternate methods of slope protection.

The engineering use chart, discussed in chapter 1, provides

information on desirability of earth materials for various

uses from a quality standpoint as grouped using the Unified

Soil Classification System. Usually, it is infeasible to

secure any material having ideal characteristics (including

rock); investigators must exercise considerable judgment in

selecting material sources. The extent to which desirable

characteristics are sought varies according to the purpose for

which the material is to be used. In exploiting materials,

volume may be substituted for quality to some extent;

special processing of nearer sources may be more

economical than long hauls. A definite need for and an

improvement in the quality of material must exist with

increasing distance from the emplacement site to justify long

hauls. For distant sources, accessibility and type of

available transportation facilities have an important bearing

on desirability of the source. 

b. Impervious Materials.&Situations arise where a

special source of impervious materials is required, namely,

in the construction of canals; dams on pervious foundations;

and terminal, equalizing, or regulating reservoirs. When

extensive permeable beds are found in the foundations for

such structures, investigators must then locate a source of

impervious material. Such material should be

impervious&as compared to foundation soils&to justify

using the material, but highly plastic clay materials are

seldom desirable or necessary. These impervious soils are

applied as blankets or linings over pervious foundations.

Hydraulic gradients through the blanket or lining will be

high; consequently, it is essential that gradations should

satisfy appropriate filter criteria so that piping of fines from

the blanket or lining into the more pervious foundation

materials is prevented.

Piping also may be prevented by use of geotextiles or of soil

bedding which meet appropriate filter criteria. The

impervious material will be exposed to water in the canal or

reservoir and should be capable of resisting erosive forces

of flowing water and of waves. The material may be

exposed to alternately wet and dry conditions and in some

cases to freezing and thawing. Therefore, materials used

for exposed linings or blankets should be free of shrinking

and swelling characteristics. Special care should be taken

to avoid use of dispersive clay soils for any of these

purposes. A number of methods can be employed to

overcome problems such as by stabilization with lime,

cement, or insulation. However, in many cases, costs may

increase to a point where buried impermeable

geomembranes or geocomposites, or other types of linings

such as shotcrete with or without geocomposites, compacted

soil-cement, or concrete might become competitive

alternatives. Blending two different soils together to form

a superior blanketing material has been found to be

feasible&such as adding bentonite to sands may be practical.

1. Canal Construction.&On canal construction,

lining is used to reduce water loss. In turn, it conserves a

water supply, prevents waterlogging of adjacent lands, or

reduces the size of the conveyance system. Because of these

considerations, impermeable lining is very desirable;

however, thicker linings of soil material of moderately low

permeability have been used. Such linings can be protected
EARTH MANUAL

96

from erosion water by reducing the water velocity or by

providing a protective cover for the soil lining. These

linings are made as thin as possible, both to conserve

material and to minimize the necessary additional

excavation. Consequently, a mixture of coarse material

with impervious soil, either blended together or naturally

occurring, will provide a material that is both erosion

resistant and impervious. When water velocity in a canal is

contemplated to be high or the natural soil is to erode easily,

investigations for materials for canals should include a

source of coarse material for blending or blanketing unless

the impervious material already contains an appreciable

percentage of coarse particles.

2. Dam Construction.&On dam construction, it is

seldom possible to significantly reduce reservoir water loss

with partial earth blankets; but seepage gradients can be

reduced to the point that piping is prevented. Materials for

blankets should be highly impervious so their permeability

is very low compared to that of the foundation. Resistance

to flowing water usually is not critical, but care should be

taken that dispersive clay soils are not used for this

application. Because erosion from flowing water is not

critical, blending requirements need not be anticipated.

However, the possibility of the blanket piping into the

foundation and the possibility of cracking of material having

high shrinkage and swell characteristics must be considered.

Investigations may be required to locate a source of blanket

material for storage dams; but more often, blankets are

needed in connection with diversion dams. The qualifying

differences between impervious blanket material for canals

and dams as discussed above should be noted.

c. Pervious Materials.&Clean sands and gravels are

required for:

 ̆ concrete aggregates,

 ̆ filter and drainage zones in earth dams,

 ̆ filters and drains associated with construction of

concrete structures,

 ̆ bedding under riprap on earth dams, 

 ̆ transition zones to prevent piping.

Distance from the construction site to areas where

investigations are made for locating a supply of pervious

materials having special properties will vary depending on

the need for such special material. Using naturally

occurring materials rather than those that require processing

is usually more economical, especially when found near the

site. Designs almost always can be made to accommodate

pit run materials such as terrace deposits, etc. If quantities

are small, materials acquired from developed commercial

sources may be more economical.

On major projects such as large embankment dams, careful

investigations must be performed so appropriate information

is obtained for developing pervious borrow materials. A

borrow area rarely produces concrete aggregates or filter

and drain materials without processing. Processing

operations are required to wash, sort, and crush granular

materials and are critical to the contractor in sequencing

construction events. For example, in a dam, filter and drain

material will be in early demand since the downstream base

of a dam will require a drainage blanket. In many cases,

processing and stockpiling pervious materials may be

desirable in the early phase of construction.

For all borrow investigations, long, linear test trenches

should be excavated&in addition to point explorations such

as test pits or auger borings&to gain a better understanding

of geologic variability at the site. Trenches in alluvium

should be excavated perpendicular to streamflow. Complete

trench wall maps should be made, with all pockets and

lenses shown, and with geologic interpretations. Special

care should be taken to evaluate percentage of fines and

their plasticity so formation of clay balls can be avoided

during placement of the pervious materials.

On major projects as large dams, such volumetric estimates

of oversized particles, e.g., cobbles and boulders, should be

supplemented with full-scale gradations of representative

materials because processing of oversize is crucial to the

contractor' s crushing operations. Coarse particles should be

examined petrographically, and hardness should be

evaluated. Contractors should be supplied with all borrow

information that includes summary gradation plots which

include comparisons to design gradation requirements. Test

pits should be left open for prospective bidders, if possible.

Uncertainties in processing borrow materials should be

noted in the specifications.

1. Concrete Aggregates.&Procedures for investigation for concrete aggregates are described in the Concrete

Manual [17]. Investigations for concrete aggregates

require more information than other pervious materials.

Consequently, data from investigations for concrete aggregate also can be used for other purposes, but data from

investigations for other purposes are not usually adequate

for concrete aggregate investigations.

2. Filters and Drains.&Although the quantity of

pervious materials required for filters and drains is usually

small, quality requirements are high. Filters and drains are
CHAPTER 2—INVESTIGATION

97

used to prevent piping and reduce hydrostatic uplift

pressures. Therefore, the material must be free draining,

but at the same time must be able to dissipate relatively high

hydraulic heads without movement of either the filter

material or the protected soil. Often, a single layer of

material will be inadequate, and a two-stage filter should be

designed. Fine sand, silt, or clay in the pervious material

is objectionable; processing by washing or screening is often

required to produce acceptable material from most natural

deposits.

Although grading requirements will be different, filter

materials are commonly secured economically from sources

acceptable for concrete aggregate. Particle shape of

pervious material is not as critical; processed concrete

aggregates rejected for shape can usually be used to

construct drainage blankets and drains, if suitable gradation

and adequate permeability is maintained. However,

minerals contained in pervious materials should be evaluated

for potential degradation as water percolates through the

filter. Likewise, attention should be given to soundness and

durability of particles to be sure no significant change

occurs in gradation due to particle breakdown as the

material is compacted.

Quality evaluation tests, similar to those performed on

aggregate for concrete, are performed on these materials to

evaluate their durability and suitability as filters or drains.

Filter and drain materials must meet filter design criteria as

outlined in Design Standards No. 13&Embankment Dams

([18] ch. 5).

3. Bedding Under Riprap.&Sand and gravel

bedding material under riprap should be coarse but still

conform to filter criteria in order to perform as a transition

between embankment and riprap. Because of this

requirement, blanket material is sometimes secured from

rock fines resulting from quarrying operations. However,

if a coarse gravel deposit can be found within reasonable

distance from the damsite, developing the source will

usually be economical. Quantity requirements are quite

large, and special processing by screening or other means is

costly. The principal purpose of this type of blanket is to

prevent waves which penetrate the riprap from eroding the

underlying embankment. A limited amount of fine material

is not objectionable even though some will most likely be

lost through erosive wave action. The material should be

durable; most fine material found in gravel deposits is adequate. However, gravel deposits have been found

containing large quantities of unsuitable material. Such

deposits include ancient gravel beds often in terraces that

have deteriorated by weathering, and talus or slopewash

deposits where water action has been insufficient to remove

the soft rock.

4. Drainage Blankets.&Materials used for drainage

blankets within the downstream zones of earth dams should

be pervious with respect to both the embankment and

foundation soils. The material should not contain

appreciable quantities of silt or clay, and the gradation

should meet the required filter criteria [18].

Sometimes, the volume of blanket material can substitute for

poor quality. If a sufficient quantity can be found close to

the point of use, a search for better materials at greater

distances may not be warranted.

5. Road Surfacing and Base Course.&Materials

for road surfacing or base course are sought primarily for

strength and durability. The preferred material for

surfacing will consist primarily of medium to fine gravel

with enough clay to bind the material together and with

relatively small amounts of silt and fine sand. Similar

material, but without silt or clay, is preferred for base

courses. For these materials, when road construction is for

replacement and to be performed by the Bureau of

Reclamation, requirements of the local highway agency

should be determined before making extensive

investigations.

d. Riprap and Rockfill.&

1. General.&Rock fragments are required in

connection with earthwork structures to protect earth

embankments or exposed excavations from the action of

water either as waves, turbulent flow, or heavy rainfall.

Rock fragments associated with wave action or flowing

water protection are called riprap. The term rockfill is

commonly applied to the more massive bodies of fill in dam

embankments and consists of rock fragments used primarily

to provide structural stability. Such rockfills may serve as

drainage blankets or blankets under riprap; and if the

material to be used is adequate for slope protection, a

separate requirement for riprap may not be necessary. 

Material from rock sources should satisfy two main

requirements: (1) the rock source should produce rock

fragments in suitable sizes according to required use, and

(2) the rock fragments should be hard and durable enough

to withstand the processes involved in procuring and placing

them and to withstand normal weathering processes and

other destructive forces associated in the place of use.
EARTH MANUAL

98

Figure 2-15.—Results of a major blast in a riprap quarry.

Specific gravity and density are important attributes

although, to some extent, increase in fragment size may be

substituted for high density. Suitable substitutes are

available for riprap and rockfill blankets such as soil-cement

or asphalt for upstream slope protection, and sod cover for

downstream slope protection. These alternatives are

considered when rock is unavailable or economically

prohibitive.

2. Riprap for Earth Dams.&Riprap surfaces on

earth dams must withstand severe ice and wave action as

well as destructive forces associated with temperature

changes, which includes freezing and thawing, heating and

cooling, and wetting and drying. Securing highly durable

material for riprap is important. Laboratory tests such as

the "freeze-thaw" test will disclose weaknesses and lack of

durability. Durability can be judged by finding locations

where the same rock is subjected to similar conditions in

other reservoirs, in stream channels, or in other exposures.

Figure 2-15 shows results of a major blast in a riprap quarry

which produced rock fragments of the sizes required for a

dam constructed in the Western United States. A more

detailed discussion on riprap requirements, use, and

placement is in Design of Small Dams [16] and in Design

Standards No. 13 % Embankment Dams [18], chapter 7, and

in [19]. Joint spacing in a rock outcrop will be a

determining factor as to whether adequate size fragments

can be secured. Old joints that have become cemented but

would break apart during excavation should be noted.

Because these mechanical weaknesses are often difficult to

detect, a blast test should be conducted (fig. 2-16). Riprap

blasting techniques are covered in the Engineering Geology

Field Manual [20] and in Blasting Review Team Report [21].

When a bedrock exposure containing satisfactory rock is

unavailable in the immediate vicinity of a damsite, it may be

possible to secure riprap material from:

 ̆ stream deposits,

 ̆ glacial till,

 ̆ talus slopes (fig. 2-17), and, occasionally,

 ̆ surface deposits.
CHAPTER 2—INVESTIGATION

99

(A) Initial blast.

(B) Results of blast.

Figure 2-16.—Blasting a rock ledge at the riprap source for Stampede Dam, California. 

The rock is basalt having a specific gravity of 2.6.
EARTH MANUAL

100

Figure 2-17.—Talus slope of igneous rock proposed for riprap.

The quality of many rock sources changes laterally and with

depth, and overburden on some sources becomes so thick

that its removal is uneconomical. It will frequently be

necessary to explore rock sources with drill holes,

depending on geologic conditions, before establishing the

deposit as an approved source.

When investigating riprap at distances greater than a few

kilometers, a number of economical sources are usually

located. Specifying quality requirements for the riprap

rather than the source is desirable, so that a contractor may

competitively secure material from the most economical

source. If riprap from several sources satisfies quality

requirements, all sources are listed in the specifications.

Each deposit should be sampled and tested sufficiently to

establish essential characteristics. This information will be

used in designs to establish minimum acceptable properties

for specifying quality requirements. Establishment of these

minimum requirements will be influenced by:

 ̆ initial cost,

 ̆ effective life of the cover,

 ̆ repair cost,

 ̆ climatic conditions, and

 ̆ thickness of cover.

3. Riprap for Stilling Basins.&Riprap blankets are

commonly used downstream of spillway and outlet works

stilling basins, and other energy dissipating structures where

high-velocity turbulent flow must be reduced to noneroding

velocities. Quantities involved are usually comparatively

small, but quality requirements may exceed those of earth

dam reservoir riprap blankets. In some instances, even

though marginal material may be used on the dam surface,

high-quality riprap must be secured for the blanket material

used to protect other structures. Where investigations

disclose only moderate quality rock in the vicinity of the

site, investigations should be extended to establish the

location of a high-quality source.
CHAPTER 2—INVESTIGATION

101

4. Riprap for Canals.&Riprap is used in canal

construction where severe erosion of the channel could

occur. Usually, these locations occur in short reaches of

canals below concrete structures, adjacent to bridge piers,

and at sharp turns in alignment. Protective requirements

vary over a wide range; they may be satisfied with a thin

gravel cover or may require riprap equal to that required

below the controlling works of dams. When these areas

must be protected by riprap, blankets are usually 300 to 600

mm (12 to 24 in) thick with corresponding rock sizes.

5. Rockfill Blankets.&When rockfill is used to

provide surface protection from rainfall, almost any rock

fragments that do not break down excessively on exposure

to air or water are acceptable as rockfill. Shales and some

siltstones are about the only types of rock considered

unacceptable for this purpose. Size is not critical except that

fragments should be at least gravel size, and the upper-size

limit is controlled by the specified thickness of the blanket.

Rounded gravel, if readily available, is frequently used for

this purpose. Special investigations for this type of material

are almost wholly confined to the plains areas of the

Western United States where rock is generally absent within

economical depth beneath ground surface. Substitutes may

include sod blankets. Securing rockfill blanket material

from appreciable distances is justified only where quality

rock is absent in the immediate vicinity of the work and

when substitutes are inadequate.

6. Investigative Procedures.&Investigation

requirements for rock sources for riprap are variable

dependent upon:

 ̆ the stage of investigation, 

 ̆ whether a choice of material is locally available, 

 ̆ the type of specifications to be prepared; i.e.,

whether contractor or Government furnishes the rock.

Guidance for investigations and testing is no longer included

in the Earth Manual, Part 2, Third Edition. Reclamation

guidance will be included in a new Rock Manual, under

development. The practice will be issued as USBR 6025,

"Sampling and Testing of Rock Fragments or Rock Samples

for Riprap Usage." Draft copies of this standard can be

obtained from the Earth Sciences Laboratory in Denver.

Another source of information on investigating riprap

sources can be found in ASTM standard D-4992-94,

"Standard Practice for Evaluation of Rock to Be Used for

Erosion Control."[22]

2-7. Materials for Stabilized and Modified

Soils.&

a. General.&A stabilized soil is a soil whose

properties are partially or completely changed by adding a

dissimilar material before compacting the soil or by placing

an additive into the soil in place. Depending upon the

properties and the amount of additive, all of the properties

characteristic of the soil may be completely and permanently

changed.

A modified soil is a soil in which specific properties may be

either temporarily or permanently changed. Soils are

modified by adding a small amount of an additive before

compaction or by placing the additive into the soil in place.

Stabilized soils are used as a substitute for:

 ̆ riprap to protect the upstream slopes of earth dam

embankments,

 ̆ linings for reservoirs, and

 ̆ temporary protection of construction during river

diversion.

They are used also as protective blankets and as pipe

bedding. Small quantities of additives are used to:

 ̆ modify and improve properties of soils used in fills,

 ̆ increase erosion resistance,

 ̆ reduce permeability, or 

 ̆ provide temporary stability during construction.

b. Compacted Soil-Cement.&Compacted soil-cement

is a stabilized soil consisting of a mixture of soil, cement,

and water compacted to a uniform, dense mass used for

linings, protective blankets, and slope protection in lieu of

riprap [23, 24]. Placement water content and density are

controlled by the laboratory compaction test (see USBR

5500).

The most desirable soil for soil-cement is a silty sand (SM)

which has a good distribution of sizes with 15 to 25 percent

fines [25]. Other soils may be used; however, more cement

may be required to satisfy strength and durability

requirements if cleaner, coarse-grained soils are used.

Uniformity of soil gradation and moisture when introduced

into a continuous feed pugmill type mixing plant is the most

important factor in ensuring uniformity of compacted

soil-cement.
EARTH MANUAL

102

Soil is usually obtained from a borrow area explored in

detail to ensure quantity and uniformity desired. A uniform

deposit is most desirable. Stratified deposits may be used,

provided selective excavation and processing is practical and

economical compared to using other potential sources.

Selective excavation and mixing during stockpiling may be

necessary to provide a soil as uniform in grading and

moisture content as practicable. Screening equipment may

be necessary to (1) remove undesirable organic material and

oversize particles; (2) remove or reduce the size of sand,

silt, and clay aggregations, called "clay balls," which tend

to form in the borrow areas containing lenses of clay.

Laboratory testing is required to determine the quantity and

type of cement, the moisture limits, and the compaction

requirements to be specified for construction.

Representative samples of the finest, average, and coarsest

material should be submitted for laboratory testing. The

water proposed for mixing should be reasonably clean and

free from organic matter, acids, alkali, salts, oils, and other

impurities. Clear water that does not have a saline or

brackish taste and is suitable for drinking may be used;

however, doubtful sources should be sampled and tested.

c. Soil-Cement Slurry.&Soil-cement slurry is a

cement stabilized soil consisting of a mixture of soil and

cement with sufficient water to form a material with the

consistency of a thick liquid that will flow easily and can be

pumped without segregation. Sands with up to 30-percent

nonplastic or slightly plastic fines are best.

Reclamation has used soil-cement slurry for pipe bedding

[26, 27]. Even though materials from the trench excavation

may be used, locating the borrow areas along the pipeline

alignment is generally more economical and usually results

in a better controlled and more uniform product. Soilcement slurry has often been supplied by commercial readymix firms when haul distances are economical.

d. Modified Soil.&A modified soil is a mixture of soil,

water, and a small amount of an additive. The various

components are well mixed before compaction or added to

the soil in place to modify certain properties&temporarily or

permanently&to within specified limits. Because of the 

small amount of additive, a modified soil usually retains

most of the characteristics of the original soil because it is

an aggregation of uncemented or weakly cemented particles

rather than a strongly cemented mass. Limited experience

has been acquired on even the most commonly used

additives including asphalt, portland cement, fly ash, lime,

slag, resins, elastomers, and organic chemicals.

As a soil additive, use of lime is the oldest known method

of chemical stabilization: it was used by the Romans to

construct the Appian Way. Soil-lime is a mixture of soil

(usually clay), lime, and water which is compacted to form

a dense mass. Experience has shown that mixtures of most

clay soils with either quick or hydrated lime and water will

form cementitious products in a short period of time.

Reclamation applications for water resources works have

been limited to use of lime for stabilizing expansive clay

soils and dispersive clay soils.

Reclamation' s Friant-Kern Canal in California experienced

severe damage to both earth and concrete-lined sections

from expansive clay soils. Lime, 4 percent by dry mass of

soil, was used during rehabilitation of Friant-Kern Canal;

and the soil-lime lining has proved durable after more than

20 years of service [28].

Dispersive clay soils will erode in slow-moving or even still

water by individual colloidal clay particles going into

suspension and then carried away by flowing water.

Dispersive clay soils may be made nondispersive by addition

of 1 to 4 percent lime by dry mass of soil. Generally, the

design lime content is defined as the minimum lime content

required to make the soil nondispersive. If lime-treated soil

is to be used in surface layers, adding additional lime may

be desirable to increase the shrinkage limit to near optimum

water content to prevent cracking from drying. In

construction specifications, the lime content is often

increased 0.5 to 1.0 percent above the design value to

account for losses, uneven distribution, incomplete mixing,

etc. Dispersive clay soils were found throughout the borrow

areas for Reclamation' s McGee Creek Dam in Oklahoma.

Lime was used to stabilize those soils for certain critical

parts of the dam, and specifications required between

1.5 and 3.0 percent lime to be added to the soil [29].

B. Exploratory Methods

2-8. General.&Exploration methods may be grouped

in different ways: (1) those that produce usable samples and

those that do not, and (2) those that are accessible and those

that are not. In investigations of foundations or materials,

one purpose of an exploration is to secure samples of soil

and rock, either for visual examination or for laboratory

testing. Procedures which will not produce samples should

be used only where the general characteristics of the
CHAPTER 2—INVESTIGATION

103

materials to be penetrated are already known, where

sufficient samples have been secured for testing, or where

penetration test or other in-place test data can be used to

define or refine an investigation plan or program. Sampling

methods will vary according to the type of material to be

sampled and according to the acceptable degree of sample

disturbance; and test holes or other investigations may be

advanced by manual labor or by mechanical power.

Exploratory holes may be of various sizes depending upon:

 ̆ the need to access,

 ̆ the penetration depth,

 ̆ the size of sample to acquire, and

 ̆ the type of material to penetrate.

Stability of small-size holes entirely above the water table is

dependent on the type of material encountered. Holes in

soil below the water table usually require support by steel

casing, augers, or by drilling fluid. Sometimes, exploratory

holes require protection with steel casing because of

potential damage to the hole by drilling operations and to

prevent contamination of samples with materials from higher

elevations. As part of a foundation investigation, many

exploratory holes require water testing. When casing is

used, specific portions of the foundation may be water tested

to simplify evaluation, to concentrate on certain foundation

conditions, and to determine required treatment. If water

testing or piezometer installation is a part of the

requirement, bentonite drilling mud should not be used.

In soft or loose soil foundations, the strength of the

materials in the wall of the hole may be insufficient to keep

soil from flowing into the bottom of the hole. In many

instances, just keeping the hole filled with water will suffice

to hold materials in place. In severe cases, a wall stabilizer,

a heavy fluid, or both must be used. Information on the

various stabilizers may be obtained from drilling fluid

manufacturers. If water testing is not required, drilling fluid

consisting of a mixture of commercially available bentonite

or other materials and water may be used. Drilling fluid

may be specially prepared to have a required mass per unit

volume due to addition of finely divided solid material or to

addition of other additives. (See USBR 7105 and USBR

5890 through 5895.)

Samples may be secured from holes supported by drilling

fluid or casing with either double-tube or triple-tube soil

samplers, core samplers, drive tube, or with push-tube

samplers. To minimize sample disturbance,

fixed-piston-type samplers are preferable for very soft soils.

The double-tube hollow-stem auger sampler is best for water

sensitive, very loose, or unsaturated low density soils. If

undisturbed sampling is not successful, a number of in-place

tests can be performed that yield valuable information

concerning foundation soil conditions. Radiographs (X-ray)

may be taken of undisturbed samples after they are received

in the laboratory. The radiographs are studied to determine

degree of disturbance to each sample. Radiographs are also

useful to identify:

 ̆ slip planes,

 ̆ fault gouge zones,

 ̆ slickensides,

 ̆ contamination by drilling fluid,

 ̆ amount of slough on top of a sample,

 ̆ location of gravel particles within a sample, 

 ̆ various other conditions.

Figure 2-18 shows some of the samplers available for

obtaining undisturbed samples.

In drilling exploratory holes through hard materials, where

support might normally be unnecessary, crushed zones or

faults may be encountered from which rock fragments fall

into the hole and either plug the hole, bind the drilling

equipment, or both. In such situations, cement grout may

be placed in that area; after the grout has set, the hole can

be drilled through the grout. Because these crushed zones

or faults represent some of the critical conditions being

investigated from an engineering standpoint, all pertinent

tests (such as water tests) must be performed before

grouting the unstable section of hole; a record of the

conditions should be fully reported and recorded.

All exploratory holes should be protected with suitable

covers and fences to prevent foreign matter from entering

the holes and to keep people and animals from disturbing

them or falling into them. All holes should be filled or

plugged after fulfilling their purpose.

2-9. Accessible Exploratory Methods.&

a. General.&Open test pits, large diameter borings,

trenches, and tunnels are accessible and yield the most

complete information of the ground penetrated. They also

permit examination of the foundation bedrock. When depth

of overburden and ground-water conditions permit their

economical use, these methods are recommended for

foundation exploration in lieu of relying solely on borings.

In prospecting for concrete aggregate, embankment, filter,

or drain materials containing cobbles and boulders, open

pits and trenches may be the only feasible means for

obtaining the required information.
EARTH MANUAL

104

Figure 2-18.—Samplers used for undisturbed soil sampling.

b. Test Pits.&Test pits are an effective means to

explore and sample earth foundations and construction

materials and to facilitate inspection, sampling, and testing.

The depth of a test pit is determined by investigation

requirements but is usually limited to the depth of the water

table. Dragline, backhoe, clamshell, caisson drilling or

auger equipment, and bulldozer pits are usually more

economical than digging pits by hand for comparatively

shallow materials explorations. Explosives may be required

to break up large boulders. At the surface, the excavated

material should be placed in an orderly manner around the

pit to indicate depth of pit from which the material came to

facilitate accurate logging and sampling. The moisture

condition should be determined and recorded before drying

occurs by exposure to air. 

Investigations in open, accessible explorations such as test

pits, large diameter borings, trenches, and tunnels are

inherently hazardous. Federal, State, and local regulations

must be followed when planning and executing accessible

investigations. Occupational Safety and Health Act (OSHA)

regulations for excavation safety (29 CFR 1926.650-652)

should be consulted prior to planning accessible

explorations. Regulations require that competent personnel

plan, design, and monitor excavations. Excavations greater

than 5 ft in depth normally require sloping or shoring

systems designed by professional engineers. Large diameter

borings and deep trenches may be considered to be confined

space and may require special ventilation, monitoring, and

rescue safety equipment.

Deep test pits should be ventilated to prevent accumulation

of dead air. Ventilating pipe, which begins slightly above

the floor extending about 1 m (3 ft) above the mouth of the

pit, is usually satisfactory. Canvas and plastic sheeting have

been used to deflect wind into the hole. Oxygen meters

should be used to determine satisfactory air quality. Test

pits left open for inspection must be provided with covers

and barricades for safety. All applicable safety and shoring

requirements must be met.

When water is encountered in the pit, a pumping system is

required for further progress. Small, portable, gasolinepowered, self-priming, centrifugal pumps can be used;

however, air or electric powered equipment is preferred

whenever possible because of the change of carbon

monoxide poisoning. The suction hose should be 15 mm

(1⁄2 in) larger in diameter than the pump discharge and not

more than 5 mm (15 ft) long. This requires resetting the

pump in the pit (on a frame attached to the cribbing) at

about 4-m (12-ft) intervals. When an air or electric

powered pump is not available, and a gasoline engine is

used, pipe the exhaust gases well away from the pit when

the engine is in or near the pit. When a gasoline engine is
CHAPTER 2—INVESTIGATION

105

operating within a pit, personnel shall not be allowed in the

pit for any extended period of time regardless of how well

the system is vented. Dewatering test pits is usually

expensive and is often unwarranted.

c. Large-Diameter Borings.&Caisson auger rigs

using large-diameter discs, gushers, or buckets are often

used when accessible explorations are required to be deeper

than about 6 m (20 ft). Depths of over 30 m (100 ft) have

been achieved using this method. Wall support must be

provided for the total depth. Typical wall support for largediameter borings may consist of welded steel casing installed

after the boring is complete or preformed steel liner plate

segments bolted together and placed as the boring

progresses. Personnel access within a drilled caisson hole

may be provided by an elevator platform rigging using

power from a crane hoist or by notched safety rail ladder

using an approved grab-ring safety belt. Work may be

performed at any depth in the drilled caisson boring using

steel platform decking attached to the steel wall support,

from a steel scaffolding, or from an elevator platform.

Access for material logging or sample collection outside a

steel-encased caisson hole may be accomplished by cutting

openings in the casing at desired locations or by removing

bolted liner plate segments to expose the sides of the boring.

Sufficient ventilation must be maintained at all times for

personnel working within the excavation. Radio

communication to surface personnel should be maintained.

Water within a drilled excavation may be removed by an

electric or air-powered pump with discharge conduit to the

surface. Dewatering may require stage pumping by using

several holding reservoirs, at appropriate elevations, and

additional pumps as required to lift the water from the

borehole to the ground surface.

Large-diameter borings left open for inspection should

always be provided with locking protective covers and

should be enclosed by a fence or barricade.

d. Trenches.&Test trenches are used to provide a

continuous exposure of the ground along a given line or

section. In general, they serve the same purpose as open

test pits but have the added advantage of disclosing the

lateral continuity or character of particular strata. They are

best suited for shallow exploration (10-15 ft [3-4.5 m]).

Trenching can be used to drain wet borrow areas and at the

same time fulfill investigation requirements.

On a slope, field work consists of excavating an open trench

from the top to the bottom to reach representative

undisturbed material. Either a single slot trench is

excavated down the face of a slope, or a series of short

trenches can be spaced at appropriate intervals along the

slope.

Depending on the extent of investigation required,

bulldozers, backhoes, or draglines can be used. Figure 2-19

shows a trench excavated by bulldozer. All safety

procedures and guidelines must be followed when

excavating deep trenches to prevent accidents caused by

caving ground.

The material exposed by trenches may represent the entire

depth of significant strata in an abutment of a dam;

however, their shallow depth may limit investigation to only

a portion of the foundation, and other types of exploration

may be required to explore to greater depths. Test trenches,

however, are often extensively used to delineate stratigraphy

in borrow areas. As with test pits, trenching permits visual

inspection of soil strata which facilitates logging of the

profile and selection of samples. Large undisturbed samples

or large disturbed individual or composite samples are easily

retrieved from test trenches. Trenches in sloping ground

have the further advantage of being self-draining.

e. Tunnels.&Tunnels, adits, or drifts have been used

to explore and test areas beneath steep slopes in or back of

clifflike faces. Any exploratory tunnel or drift is usually

roughly rectangular in shape and about 1.5 m wide by 2 m

high (5 ft by 7 ft). When lagging is required for side and

roof supports, it should be placed to follow excavation as

closely as practicable. Excavation of exploratory tunnels

can be a slow, expensive process; consequently, this type of

investigation should be employed only when other methods

will not supply the required information.

Logging and sampling of exploratory tunnels should proceed

concurrently with excavation operations if possible (see

fig. 2-20).

If explosives were used to excavate the tunnel, selecting

locations for undisturbed samples must be carefully made.

This includes removal of all material disturbed by the

explosives, thereby exposing undisturbed material.

2-10. Nonaccessible Exploratory Methods.&

a. General.&The usual nonaccessible exploratory

methods are cone penetrometer, standard penetration, auger

drilling, rotary drilling, core drilling, and in-place field

testing. Of the methods, auger drilling, rotary drilling, and

core drilling are the most commonly used to obtain samples
106

Figure 2-19.—Shallow test trench excavated by bulldozer.
107

Figure 2-20.—Example of tunnel mapping from machine-excavated tunnel.
EARTH MANUAL

108

for laboratory examination and testing. It should be stressed

that geologic complexity should have been determined

beforehand, and exploratory drilling operations should never

be solely relied upon to provide data for accurate and

reliable geologic interpretation of a complex geologic

structure.

Economics and depth requirements are the principal reasons

for performing extensive drilling programs in lieu of

constructing accessible test pits or trenches to establish

geologic conditions. If drilling is considered the only

feasible method for conducting subsurface explorations, the

following considerations should be given priority when

planning the remainder of the exploration program:

 ̆ All relevant subsurface and geologic information

should be assembled and used when selecting

strategic drilling locations so the maximum amount of

subsurface information can be obtained from a

minimum number of drilling locations.

 ̆ The type of exploration drilling, in-place testing,

sampling, or coring necessary to obtain pertinent and

valid subsurface information should be carefully

considered (see section 2-12 for embankment

drilling).

 ̆ The type of drilling rig capable of accomplishing

exploration requirements must be determined.

Although drilling may be accomplished to some extent using

manual methods (i.e., hand augers, tripod assemblies, and

hand-crank hoist systems), many factors such as equipment

technology, economics, depth requirements, type of sample

needs, and the need for accurate subsurface information

have made manual exploration methods obsolete. Various

types of mechanical power-driven drilling equipment are

available, and most efficient use and capability of each type

of drilling unit is discussed.

b. Auger Borings.&General.&Auger borings often

provide the simplest method of soil investigation and

sampling. They may be used for any purpose where

disturbed samples are satisfactory and are valuable in

advancing holes to depths at which undisturbed sampling or

in-place testing is required. Mechanical hollow-stem auger

drilling and sampling are the most preferred methods for

drilling in existing dam embankments to avoid hydraulic

fracturing. Hollow-stem augers are frequently used for

drilling potentially contaminated ground because fluids are

not used. Sometimes, depths of auger investigations are

limited by the ground-water table, by rock, and by the

amount and maximum size of gravel, cobbles, and boulders

as compared with the size of equipment used. 

Hand-operated post hole augers 100 to 300 mm (4 to 12 in)

in diameter can be used for exploration to shallow depths

(fig. 2-21).

An auger boring is made by turning the auger the desired

distance into the soil, withdrawing it, and removing the soil

for examination and sampling. The auger is inserted into

the hole again, and the process is repeated.

A soil auger can be used both for boring the hole and for

bringing up disturbed samples of soil. It operates best in

somewhat loose, moderately cohesive, moist soils. Usually,

holes are bored without addition of water; but in hard, dry

soils or in cohesionless sands, introduction of a small

amount of water into the hole will aid with drilling and

sample extraction. It is difficult to avoid some contamination or mixing of soil samples obtained by small augers.

Rock fragments larger than about one-tenth the diameter of

the hole cannot be successfully removed by normal augering

methods. Large-size holes permit examination of soils in

place; therefore, they are preferred for foundation

investigation. An excellent guide for using augers in water

resources investigations is available from USGS:

Application of Drilling, Coring, and Sampling Techniques

to Test Holes and Wells [30].

Pipe casing may be required in unstable soil in which the

borehole fails to stay open&and especially where the boring

is extended below ground-water level. The inside diameter

of the casing must be slightly larger than the diameter of the

auger used. The casing is driven to a depth not greater than

the top of the next sample; the boring is cleaned out by

means of the auger. Then, the auger can be inserted into

the borehole and turned below the bottom of the casing to

obtain the sample.

c. Mechanical Auger Drilling.&Auger drills are

mechanical, engine-powered drills that are designed to

produce high rotational torque at low revolutions per minute

as required to drill into and collect subsurface soil samples.

Drill cuttings and soil samples are removed by the auger' s

rotation without using fluid circulation media; thus, the

requirement for high torque capability of the drill.

Multipurpose drills are available which are capable of auger,

rotary, or core operations. Discussion in this section is

directed toward describing and explaining individual general

uses for each of the four distinct types of auger-drilling

operations used in subsurface explorations:

 ̆ Continuous-flight auger drilling

 ̆ Hollow-stem auger drilling

 ̆ Helical, disk, and bucket auger drilling

 ̆ Enclosed augers
109

Figure 2-21.—Types of hand augers (2-inch helical, 2- and 6-inch Iwan, and 6-inch Fenn [adjustable]).
EARTH MANUAL

110

1. Continuous-Flight Augers.&Continuous-flight

auger drilling often provides the simplest and most

economical method of subsurface exploration and disturbed

sampling of surficial deposits. Flight augers consist of a

center drive shaft with spiral-shaped steel flights welded

around the outside circumference of the drive shaft.

As each auger section is drilled into the ground, another

section is added with an identical spiral flight that is

manufactured to match the in-hole auger. The joining of

each matched auger section results in a continuous spiral

flight from the bottom of the hole to the surface. The

auger' s rotation causes drill cuttings to move upward along

the spiral flights so that disturbed soil samples can be

collected at the hole collar. Figure 2-22 shows a

continuous-flight auger drilling operation.

Flight augers are manufactured in a wide range of diameters

from 50 to greater than 600 mm (2 to > 24 in). The most

common auger used for obtaining disturbed samples of

overburden is 150 mm (6 in) in diameter. Normally, flight

auger depths are limited by:

 ̆ Equipment torque capability,

 ̆ ground-water table,

 ̆ firmness of materials penetrated,

 ̆ cobble or gravel strata,

 ̆ caliche zones, and

 ̆ bedrock.

Continuous-flight auger drilling is an economical and highly

productive exploration method. A common and efficient use

of flight augers is to define borrow area boundaries and

depths. Borrow area investigations are conducted by

augering holes on a grid pattern to define borrow boundaries

and to estimate quantities of usable material. Flight augers

are especially efficient when used to collect composite

samples of mixed strata material to establish a borrow depth

for excavation by belt-loader equipment. Composite

samples are collected by advancing auger borings to the

depth capability of the belt loader. Hole advancement is

accomplished by turning the auger at a low, high-torque rate

while adding downpressure for penetration to depth. At the

end of the penetration interval, the auger is turned at a

higher rate without further downward advancement to

collect a composite sample of the material augered through.

After the hole is thoroughly cleaned by bringing all cuttings

to the surface, the material is mixed to form a representative

composite sample and sacked according to requirements for

laboratory testing. If additional sample intervals are

required, the process can be repeated at a second sample

depth.

Although the above procedure for collecting composite

samples of mixed material strata is efficient, it may not

result in an accurate representative sample of the material

being drilled&especially at greater depths. This is because

the augered material may mix with sidewall material as

cuttings are brought to the surface. In addition, auger

borings through a noncohesive, low density sand stratum

can result in a sample with a greater volume of sand than

would be obtained from a borehole having a constant

diameter throughout the hole depth. (It is assumed the

diameter of the hole enlarges in the sand stratum.) If

material contamination is evident or if too large a volume of

material is recovered from a given auger penetration

interval, a hollow-stem auger with an inner-barrel wire-line

system or a continuous-sampler system should be used in

lieu of a continuous-flight auger.

Other beneficial and efficient uses of flight-auger drilling

include:

 ̆ Delineation of soil properties for lengthy line

structures such as canals and pipelines.&Economical

power auger borings can be spaced in between more

detailed sampling and testing locations.

 ̆ Determination of shallow bedrock depths.&This

method is especially valuable for estimating

overburden excavation volume required to expose

potential rockfill or riprap sources. Confirmation of

potential rock quality and usable volume must be

determined using rotary core drilling exploration

methods.

 ̆ Drilling through cohesive soils to install well points

to monitor water table fluctuation.&This method is

recommended for use only through cohesive soils that

can be completely removed from the auger hole to

leave a clean, full-size open hole so the well point

can be installed and backfill material placed.

 ̆ Determination of overburden depth to potential sand

and gravel deposits for concrete aggregate

processing.&This method would be used to estimate

the volume of overburden excavation required to

expose the sand/gravel deposit. Assessment of

quality of potential concrete aggregate and usable

volume could be determined from open pit excavation

or by use of a bucket drill.

2. Hollow-Stem Augers.&Hollow-stem auger

drilling can provide an efficient and economical method of

subsurface exploration, advancing holes for in-place testing,

and sampling of overburden material in an undisturbed

condition. Hollow-stem augers are manufactured similar to

flight augers. The difference between flight augers and
CHAPTER 2—INVESTIGATION

111

Figure 2-22.—Continuous-flight auger mounted on an all-terrain carrier.
EARTH MANUAL

112

hollow-stem augers is in the design of the center drive shaft.

The continuous-flight auger drive shaft consists of a steel

tube with end sections for solid pin connections to abutting

auger sections. The hollow-stem auger drive shaft,

however, consists of a hollow steel tube throughout the total

length with threaded or cap screw connections for coupling

to abutting auger sections. The advantages of hollow-stem

auger drilling over continuous-flight auger drilling are:

 ̆ Undisturbed sampling tools and in-place testing

equipment can be lowered and operated through the

hollow stem without removing the in-hole auger. 

 ̆ Unstable soils and water zones can be drilled through

by the hollow-stem auger without caving.

 ̆ Instruments and ground behavior monitoring

equipment can be installed and the hole backfilled

through the hollow stem.

 ̆ Removal of samples through the hollow stem

eliminates contamination from upper-strata material.

 ̆ The hollow stem may be used as casing so rotary

drilling or core drilling operations can be used to

advance the hole beyond auger drilling capabilities.

In addition to advantages listed, the hollow-stem auger can

function as a continuous-flight auger. This is accomplished

by using a plug bit within the center tube of the lead auger,

as shown on figure 2-23. The bit can be retracted at any

time for undisturbed sampling or in-place testing without

removing the auger tools from the drill hole.

In the 1960s, Reclamation developed a double-tube auger to

combine soil sampling with auger-hole advancement. This

arrangement was quite successful, especially in water

sensitive soils such as loess [31]. During the 1980s, auger

manufacturers developed (for commercial sale) double-tube

auger soil sampling tools so that undisturbed soil samples

could be recovered simultaneously with advancement of the

hollow-stem auger and without the need for drilling fluids.

This development resulted in a method to recover highquality, undisturbed soil samples of surficial deposits more

efficiently and economically than any other method. The

method is especially good for sampling low density soils that

may be susceptible to collapse upon wetting.

Hollow-stem augers are commonly manufactured in 1.5 m

(5 ft) lengths and with sufficient inside clearance to pass

sampling or in-place testing tools from 50 to 175 mm (2 to

7 in) in diameter. The spiral flights are generally sized to

auger a hole 100 to 125 mm (4 to 5 in) larger than the inside

diameter of the center tube. Normally, drill depths are

limited by:

 ̆ equipment rotational torque capability, 

 ̆ firmness of materials penetrated,

 ̆ cobble or gravel strata,

 ̆ caliche zones, or

 ̆ bedrock.

3. Helical, Disk, and Bucket Augers.&Helical, disk,

and bucket augers are useful for obtaining disturbed samples

from large-diameter borings for classifying overburden or

borrow soils. Generally, these augers are limited to

sampling above the water table without casing and can be

further limited by caving ground or oversize particles.

Figure 2-24 illustrates the basic differences of these auger

systems. Disk-auger drilling can be an economical method

of drilling large-diameter holes for disturbed sampling or for

installing large-diameter casings for accessible explorations.

A helical or disk auger has spiral-shaped flights similar in

design to a flight auger; however, it is used as a singlelength tool rather than being coupled to abutting sections.

Rotational power is provided by a square or hexagonal drive

shaft (Kelly bar) on the drill rig. With the disk-auger, drill

cuttings are retained by the upper-disk flight and are

removed by hoisting the disk auger from the hole after every

1 to 1.5 m (3 to 5 ft) of penetration.

Hole diameters range from 300 to 3,050 mm (12 to 120 in);

the larger disk-auger rigs drill to 37 m (120 ft) depth or

more using telescoping Kelly drive bars. Unless casing is

installed, disk-auger capabilities are generally limited by

cobble or boulder strata, saturated flowing sands, or

ground-water tables. Weathered or "soft" rock formations

can be drilled effectively with a helical auger equipped with

wedge-shaped "ripper" teeth. Concrete and "hard" rock can

be drilled by helical augers equipped with conical,

tungsten-carbide tipped teeth.

In addition, for use in drilling and installation of deep

accessible explorations, disk augers are used to recover

large-volume samples from specific subsurface strata. They

may be used to drill and install perforated casing or well

screens for ground-water monitoring systems. The most

common use of disk augers is drilling caissons for building

foundations.

4. Bucket Drills.&Figure 2-25 shows a bucket drill

in operation. Bucket drills or "bucket augers" are used to

drill large-diameter borings for disturbed sampling of

overburden soil and gravel material. The bucket is designed

as a large-diameter hollow steel drum, usually 1 m (3 ft)

long, that is rotated by a square or hexagonal drive (Kelly

bar) on the drill rig and connected to a steel yoke fixed to
CHAPTER 2—INVESTIGATION

113

Figure 2-23.—Hollow-stem auger with center plug.
EARTH MANUAL

114

Figure 2-24.—Illustration of the helical, disc, and barrel types of machine-driven 

augers showing basic differences. (U.S. Department of the Navy)
CHAPTER 2—INVESTIGATION

115

Figure 2-25.—Bucket drill rig in drilling position with a 24-foot triple Kelly and 36-inch bucket.
EARTH MANUAL

116

the top of the bucket. The bottom of the bucket is designed

with a hinged, lockable, steel cutter plate equipped with

wedge-shaped ripper teeth. The cutter plate is mechanically

locked during the rotational drilling operation and has a 225-

to 300-mm (9- to 12-in) bottom opening through which drill

cuttings are forced and collected in the bucket. After about

1/2 to 1 m (1.6 to 3.3 ft) of drilling penetration, the bucket

is hoisted out of the drill hole, attached to a side-jib boom,

and moved off the hole to discharge the cuttings. Cuttings

are discharged from the bucket by mechanical release of the

hinged cutter plate or by opening one side of the bucket,

which also may be hinged. The drilling operation is

continued by locking the cutter plate or the hinged side

panel of the bucket before lowering the bucket to the hole

bottom and continuing drilling.

Holes can range from 300 to 2,100 mm (12 to 84 in) in

diameter using a standard bucket. A reamer arm extension,

equipped with ripper teeth, can be attached to the bucket

drive yoke for overreaming a hole to 3 m (120 in) in

diameter using special crane-attached bucket drills. When

using overreaming bar extensions, drill cuttings enter the

bucket from the bottom cutter plate during rotary

penetration. Cuttings also fall into the top of the bucket as

a result of the rotational cutting action of the overreamer.

Generally, bucket drill capabilities are limited by saturated

sands, boulders, caliche, or the ground-water table unless

casing is installed. Weathered or "soft" rock formations can

be effectively penetrated with bucket drills. The larger

crane-attached bucket drills have achieved depths of 60 m

(190 ft) using telescoping Kelly drive bars and crane drawworks hoist systems.

Bucket drills are used for boring caisson holes for

foundations. They have proved extremely beneficial for

performing subsurface investigations into sand and gravel

deposits for concrete aggregate investigations. Also, they

may be used to drill and collect intermixed gravel and

cobble samples with particle diameters up to about 200 mm

(8 in). Bucket drills can be an effective method of drilling

deep, accessible, exploration holes. In large caisson

applications, the boring can be an "accessible"

excavation&as these are often inspected in construction.

5. Enclosed Augers.&Enclosed augers have been

used successfully in lieu of casing (fig. 2-26). The outer

barrel, which acts as casing, is connected to the sampler on

a swivel-type head and remains in a stationary position as

the auger rotates.

The sampler is lowered to the bottom of the hole and auger

rotation started. As the auger penetrates unsampled soil, the

outer barrel is pulled down with the unit, thereby holding

out any caved or foreign material. The sampled material is

retained on the helical auger inside the outer barrel. After

completing the sample run, the final penetration depth is

carefully noted and the sampler removed from the hole.

The auger is rotated in reverse to eject the sampled material.

Increased torque capacity of mechanical drills has enhanced

capability of continuous or hollow-stem augers to operate

below the water table thereby diminishing use of enclosed

augers.

d. Nonsampling Borings.&Test holes excavated

merely to determine depth to some particular stratum or

bedrock, or for advancing a hole to provide access to a

buried layer for sampling, can be accomplished by any of

the previously described methods. A number of economical

procedures are in common use. These procedures include

percussion or churn drilling, wash boring, and jetting. All

operations are based on moving the tool up and down to

chop away the material in the hole, using increasing

amounts of water in the order listed&except probing which

uses none at all. Often, probing is an economical method

for establishing the depth to a firm stratum. Variations in

procedure depend primarily on the nature of the soil to be

penetrated, with percussion drilling being used on the

hardest and most dense soils, and probing on the softest.

In churn or cable tool drilling, the tool is attached to the end

of a cable. Water is added, and the cuttings form a slurry

which is removed intermittently by pumping or bailing. In

wash boring and jetting, the cuttings are removed with a

continuous flow of water from the top of the hole. Wash

boring advances the hole by a combination of chopping and

washing. Jetting depends primarily on the cutting action of

a high-pressure stream of water. Care must be exercised to

avoid disturbing and moistening the underlying stratum to be

sampled when using these methods. Some indication of the

nature of material penetrated is obtained by examining

cuttings in the sludge or wash water, but accurate

classifications require other sampling methods. Probing

consists of driving or pushing a rod or pipe into the soil and

measuring the effort required. Probing can be accomplished

with or without jetting tips. If the layers to be penetrated

are soft enough, crude probing may be replaced by cone

penetration or other dynamic penetrometers to gain

additional information on surficial materials.

2-11. Rotary Drilling Methods.&Nonaccessible

Borings.&

a. General.&One of the most important tools for

subsurface exploration is a rotary drill rig complete with

core barrels, diamond bits or hardened metal bits, and a
CHAPTER 2—INVESTIGATION

117

Enclosed auger assembled.

Auger disassembled.

Figure 2-26.—Enclosed auger.

hydraulic or screw feed. The drill may be operated with a

variety of samplers and bits, depending on the hardness of

the material penetrated. Rotary drill equipment is

manufactured in a wide variety of forms that vary from

highly flexible to extremely specialized equipment, from

lightweight and highly mobile equipment to heavy stationary

plants, and range in size of hole and core from less than 25

(1 in) to 900 mm (36 in) or more in diameter. Normally,

drill equipment is mounted on trucks but a wide variety of

carrier units such as track, all terrain, and skid mounts are

available. They are capable of drilling to depths of hundreds or thousands of meters depending upon the type of rig

and the material penetrated.

The Diamond Core Drill Manufacturers Association

(DCDMA), which is composed of members from the United

States and Canada, has established dimensional standards for

a series of nesting casings with corresponding sizes for bits

and drill rods [32]. These standards allow for

interchangeable use of equipment from different

manufacturers. Table 2-1 shows the nomenclature for hole

size, group, and design. Nominal hole sizes run from R to

Z [25 to 200 mm (1 to 8 in), respectively]. These nominal

hole sizes are often specified in exploration requests. 

The DCDMA standards for drill rods, casings, and core bit

sizes are given on tables 2-2, 2-3, 2-4, and 2-5. Casing,

drill rods, core bits, and barrels are designed to be used as

a system for a particular hole size and group of tools. For

example, HX core-barrel bits will pass through flushcoupled HX casing (flush-coupled casing is denoted by the

group letter X) and will drill a hole large enough to admit

flush-coupled NX casing (the next smaller size) and so on to

the RX size. Flush-joint casing, denoted by group letter W,
EARTH MANUAL

118

Table 2-1.—Diamond Core Drill Manufacturers Association nomenclature for bits and drill rods

Three-Letter Names

First letter Second letter Third letter

Hole size Group Design

Casing, core barrel, diamond bit,

reaming shell,and drill rods

designed to be used together for

drilling a nominal hole size.

Key diameters standardized on an

integrated group basis for

progressively reducing hole size

with nesting casings.

The standardization of other

dimensions, including thread

characteristics, to allow

interchangeability of parts made by

different manufacturers. 

MilliLetter Inch meter

 R 1 25

 E 1-1/2 40

 A 2 50

 B 2-1/2 65

 N 3 75

 K 3-1/2 90

 H 4 100

 P 5 125

 S 6 150

 U 7 175

 Z 8 200

Letters x and w are synonymous

when used as the GROUP (second)

letter.

Any DCDMA standard tool with an x

or w as the GROUP letter belongs

in that DCDMA integrated group of

tools designed using nesting

casings and tools of sufficient

strength to reach greater depths

with minimum reductions in core

diameter.

The DESIGN (third) letter

designates the specific design of

that particular tool.

It does not indicate a type of

design.

Two-Letter Names

First letter Second letter

Hole size Group and design

Approximate hole size, same as in

3-letter names.

GROUP standardization of key

diameters for group integration and

DESIGN standardization of other

dimensions affecting

interchangeability.
CHAPTER 2—INVESTIGATION

119

Table 2-2.—Diamond Core Drill Manufacturers Association drill rod specifications

W Series Drill Rod

Rod

type

Outside

diameter

Inside

diameter

Coupling

identification Mass

per foot

lbm

Threads

per inch

Thread

in mm in mm in mm type

RW 1.094 27.8 0.719 18.3 0.406 10.3 1.4 4 Regular

EW 1.375 34.9 0.938 22.2 0.437 12.7 2.7 3 "

AW 1.750 44.4 1.250 31.0 0.625 15.9 4.2 3 "

BW 2.125 54.0 1.500 44.5 0.750 19.0 6.1 3 "

NW 2.625 66.7 2.000 57.4 1.38 34.9 7.8 3 "

HW 3.500 88.9 3.062 77.8 2.375 60.3 9.5 3 "

WJ Series Drill Rod

AWJ 1.75 44.5 1.43 36.4 0.63 16.1 3.6 5 Taper

BWJ 2.13 54.0 1.81 46.0 0.75 19.3 5.0 5 "

NWJ 2.63 66.7 2.25 57.0 1.13 28.8 6.0 4 "

KWJ 2.88 73.0 2.44 61.9 1.38 34.9 4 "

HWJ 3.50 88.9 2.88 73.1 1.75 44.5 4 "

Old Standard

E 1.313 33.3 0.844 21.4 0.438 11.1 3 Regular

A 1.625 41.3 1.266 28.6 0.563 14.3 3 "

B 1.906 48.4 1.406 35.7 0.625 15.9 5 "

N 2.375 60.3 2.000 50.8 1.000 25.4 4 "
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120

 Table 2-3.—Wire-line and American Petroleum Institute drill rods

Wire-line Drill Rods

Rod

type

Outside

diameter

Inside

diameter Gallons

per

100 ft

Weight

per

lbm

Threads

 per inch

Thread

type

in mm in mm

AQWL1 1.750 44.5 1.375 34.9 7.7 3.3 4 Taper

AXWL2 1.813 46.0 1.500 38.1 9.18 2.8 4 Regular

BQWL1 2.188 55.6 1.812 46.0 13.4 4.0 3 Taper

BXWL2 2.250 57.2 1.906 48.4 14.82 3.8 4 Regular

NQWL1 2.750 69.9 2.375 60.3 23.0 5.2 3 Taper

NXWL2 2.875 73.0 2.391 60.7 23.30 6.8 3 Regular

HQWL1 3.500 88.9 3.062 77.8 38.2 7.7 3 Taper

HXWL2 3.500 88.9 3.000 76.2 36.72 8.7 3 Regular

PQWL1 4.625 117.5 4.062 103.2

CPWL2 4.625 117.5 4.000 101.6

 1 Q Series rods are specific manufacturer's design.

 2

 X Series rods are specific manufacturer’s design.

API Tool Joints — Internal Flush (in-lb system)

Type/size

Joint body

o.d. Pin i.d.

Thread

type

API 2-3/8 3.375 1.750 Taper

API 2-7/8 4.125 2.125 "

API 3-1/2 4.750 2.687 "

API 4 5.750 3.250 "

API 4-1/2 6.125 3.750 "
CHAPTER 2—INVESTIGATION

121

Table 2-4.—Diamond Core Drill Manufacturers Association casing specifications

DCDMA Casing Design

Size

Outside

diameter

Inside

diameter

W series

Inside

diameter

X series

Gallons

per

l00 ft

Mass

per ft

Threads per

inch

in mm in mm in mm W series X series

RW, RX 1.44 36.5 1.20 30.5 1.20 302.0 5.7 1.8 5 8

EW, EX 1.81 46.0 1.50 38.1 1.63 41.3 9.2 2.8 4 8

AW, AX 2.25 57.2 1.91 48.1 2.00 50.8 14.8 3.8 4 8

BW, BX 2.88 73.0 2.38 60.3 2.56 65.1 23.9 7.0 4 8

NW, NX 3.50 88.9 3.00 76.2 3.19 81.0 36.7 8.6 4 8

HW, HX 4.50 114.3 4.00 100.0 4.13 104.8 65.3 11.3 4 5

PW, PX 5.50 139.7 5.00 127.0 5.13 130.2 14.0 3 5

SW, SX 6.63 168.3 6.00 152.4 6.25 158.8 16.0 3 5

UW, UX 7.63 193.7 7.00 177.8 7.19 182.6 2 4

ZW, ZX 8.63 219.1 8.00 203.2 8.19 208.0 2 4

W series casing is known as "flush-coupled casing." W series casing has flush inside diameter throughout, while X series

casing has upset diameter with coupling inside diameter equal to flush wall inside diameter.
EARTH MANUAL

122

Table 2-5.—Approximated core and hole diameters for core barrels

*Core

barrel

type/group

Set bit dimension

inside diameter

1 Core Diameter

Set reaming shell

1 Hole Diameter

in mm in mm

Conventional Core Barrels1

RWT (d) 0.735 18.7 1.175 29.8

EWD3 0.835 21.2 1.485 37.7

EWG (s.d.), EWM (d) 0.845 21.5 1.485 37.7

EWT (d) 0.905 23.0 1.485 37.7

AWD3, AWD4 1.136 28.9 1.890 48.0

AWG (s.d.), AWM (d) 1.185 30.1 1.890 48.0

AWT (d) 1.281 32.5 1.890 48.0

BWD3, BWD4 1.615 41.0 2.360 59.9

BWG (s.d.), BWM (d) 1.655 42.0 2.360 59.9

BWT (s.d) 1.750 44.4 2.360 59.9

NWD3, NWD4 2.060 52.3 2.980 75.7

NWG (s.d.), NWM (d) 2.155 54.7 2.980 75.7

NWT (s.d.) 2.313 58.8 2.980 75.7

HWD3, HWD4 2.400 61.1 3.650 92.7

HWG (s.d.) 3.000 76.2 3.907 99.2

HWT (s.d.) 3.187 80.9 3.907 99.2

DCDMA Large Diameter—Double-Tube Swivel—Core Barrels

2-3/4 × 3-7/8 2.690 68.3 3.875 98.4

4 × 5-1/2 3.970 100.8 5.495 139.3

6 × 7-3/4 5.970 151.6 7.750 196.8

Wire-line Core Barrel Systems2

AXWL (joy) 1.016 25.8 1.859 47.2

AQWL 1.065 27.1 1.890 48.0

BXWL 1.437 36.5 2.375 60.3

BQWL 1.432 36.4 2.360 60.0

BQ3WL 1.313 33.4 2.360 60.0

NXWL 2.000 50.8 2.984 75.8

NQWL 1.875 47.6 2.980 75.7

NQ3WL 1.75 44.4 2.980 75.7
CHAPTER 2—INVESTIGATION

123

Table 2-5.—Approximated core and hole diameters for core barrels

(continued)

*Core

barrel

type/group

Set bit dimension

inside diameter

1 Core Diameter

Set reaming shell

1 Hole Diameter

in mm in mm

Conventional Core Barrels1

HXWL 2.400 61.0 3.650 92.7

HQWL 2.500 63.5 3.790 96.3

HQ3WL 2.375 60.3 3.790 96.3

CPWL 3.345 85.0 4.827 122.6

PQWL 3.345 85.0 4.827 122.6

PQ3WL 3.25 82.6 4.827 122.6

 1 Conventional double-tube core barrels are available in either rigid or swivel

designs. The swivel design inner barrel is preferred for sampling because it aids in

preventing core rotation. In general, smallest core for given hole size results in

best recovery in difficult conditions (i.e., triple-tube core barrels). Use of doubletube-swivel type barrels, with split liners, are recommended in geotechnical

investigations for best recovery and least sample damage.

 2

 Wire-line dimensions and designations may vary according to manufacturer.

*s = single tube d = double tube

is such that 20- by 150-mm (3/4- by 6-in) nominal corebarrel bits will pass through ZW casing and will drill a hole

large enough to admit flush-jointed UW casing (next smaller

size) and so on to the RW size. An illustration of nested

casings and casing terminology is shown on figure 2-27.

The straight A through N drill rods with no group

designation are no longer commonly used. The recent trend

in the drilling industry has been toward the J group of drill

rods with taper threads although some W group rods are

still frequently used. Wire-line drill rod (casing) sizes are

also listed on table 2-3. Wire-line core barrel systems have

not been standardized by DCDMA, but most manufacturers

adhere to nominal hole and core sizes listed in the tables.

Rotary drills are mechanical and/or hydraulic, enginepowered drills designed for medium rotational torque at

variable rotational speeds from low (1100 r/min) for hole

penetration using tricone rock bits or carbide-tipped drag

bits to medium-high (1800 r/min) for undisturbed soil

sampling or rock core drilling with core barrels.

All rotary drills are equipped with high-pressure fluid

injection pumps or air compressors to circulate drill fluid

media. These media, which may consist of water, drill

mud, compressed air, or air-foam are used to cool and

lubricate drill bits and to hold drill cuttings in suspension for

circulation to the top of the hole at ground surface.

Accessories essential for a drill rig are:

 ̆ A watermeter

 ̆ A cathead winch and derrick for driving casing and

for hoisting and lowering drill rods 

 ̆ A pump for circulating drilling fluid to the bit and for

flushing and water testing the hole

 ̆ The required driving hammer, bits, drill rods, and

core barrels

Usually, supported holes are required except when drilling

through competent rock or stiff cohesive soils. A short

surface casing about 1.5 to 3 mm (5 to 10 ft) long is

commonly used at the top of the hole. Use of drilling

fluids&including hole wall stabilizer compounds&often

nullifies the need for casing in soil, but the foundation

cannot be effectively water tested when bentonite drill mud

is used.

At least two drive hammers should be available, a 64-kg

(140-lbm) safety or automatic hammer for standard field

penetration tests (see USBR 7015) and a 113 to 181 kg mass
EARTH MANUAL

124

Figure 2-27.—Core drill casing.
CHAPTER 2—INVESTIGATION

125

(250 to 400 lbm) for driving and removing casing pipe. The

hammer is raised by pulling tight on an attached rope which

is threaded through a sheave at the top of the derrick and

wound two to four times on the revolving cathead winch.

Sudden loosening of the rope permits the hammer to drop

on the driving head attached to the casing. Various types of

chopping bits are used to facilitate driving casing through

soils containing cobbles and boulders. Large boulders must

be drilled with a diamond bit or a roller rock bit or blasted.

Casing is raised before blasting. Figure 2-28 shows a drill

rig with derrick.

Although the rotary drill was designed primarily for

penetrating rock rather than soil, many sample barrels and

cutting bits have been developed for investigating a wide

variety of soil deposits. Double-tube core barrel samplers

of the Denison, Denver, Pitcher, and double-tube auger

types are capable of obtaining 150-mm (6-in) diameter

undisturbed samples of sands, silts, or clays for laboratory

testing. These samplers are described in USBR 7105.

The following discussion, excerpted from the Design of

Small Dams [16] provides a comprehensive review of rotary

drilling equipment technology.

b. Rotary Drills.&Seven distinctively different types of

rotary drills are used for subsurface explorations:

 ̆ Rotary-table drills

 ̆ Top-head drive drills

 ̆ Hollow-spindle drills

 ̆ Fluted Kelly drills

 ̆ Reverse-circulation (rotary and percussion) drills

 ̆ Top-head drive with percussion casing hammer drills

 ̆ Horizontal rotary drills

Each type of rotary drill is described; and a typical

application for which each drill was designed follows. In

addition, although not classified as a rotary drill, operation

and use of a churn/cable-tool drill is described.

1. Rotary-Table Drills.&Initially, rotary drills were

developed for the petroleum industry as a stationary-plant,

heavy-duty drill machine that used a large rotational table

mechanism to provide rotary power to a rigid tubular string

of rods with a bit attached. Hole penetration, using rotarytable drills, is accomplished by using heavy, weighted drill

collars coupled to the drill rod and high-pressure pumps that

discharge drill cutting circulation fluid through small jet

ports in the bit. The mass, cutting action of the rotary bit,

and high-pressure jetting-action of the circulation fluid all

combine to rapidly advance the drill hole through all types

of surficial deposits and bedrock. Although this type of drill

proved extremely effective for the petroleum industry, the

rotary-table drill was not designed to perform relatively

shallow subsurface investigations. This type of drilling

operation is prohibitively costly for shallow exploration

work and results in extremely poor core quality in

low-strength rock.

A smaller version of the rotary-table drill was developed by

drilling rig manufacturers to perform shallow explorations

and for water well drilling. These drills are generally truckmounted rigs with either a chain-driven or gear-driven

rotary table. Use of smaller, lower pressure pumps with

bypass systems provides better control over downhole fluid

pressure that can easily erode or fracture subsurface soil or

rock. Mechanical chain pulldowns were added to eliminate

use of heavy drill collars and for more precise control over

downward bit pressure. However, a drill with a mechanical

chain pulldown is not designed with the precision control

features necessary to recover high-quality core samples of

soil or laminated hard to soft rock. This type of rotary-table

drill is used primarily in the water well industry and can be

a useful method for installing ground-water monitoring

systems.

Rotary-table drills can drill holes from 150 to 600 mm (6 to

24 in) in diameter. Depth capabilities can range from 750

to greater than 3,000 m (2,500 to > 10,000 ft).

2. Top-Head Drive Drills.&The top-head drive drill

was developed to provide greater operator control over the

drilling operation. This is accomplished through use of

variable-speed hydraulic pumps and motors to control

rotational speed and downward bit pressure. Incorporation

of hydraulic systems into drilling machinery vastly

improved drilling capabilities, performance, and

reliability&with less down time for costly repairs. A skilled

operator can precisely control even the largest top-head

drive drill by:

 ̆ Monitoring drill-head hydraulic pressure (indicating

bit torque resistance),

 ̆ Monitoring drill fluid circulation pressure (indicating

open-hole, blocked-hole, open-bit, or plugged-bit

condition), and

 ̆ Controlling applied hydraulic pulldown pressure,

making it compatible with required bit pressure to

drill a given formation at a constant and efficient rate

of penetration.

In addition to controlled hydraulic down pressure (crowd

pressure), the new top-head drive drill rigs are equippedwith

"float" controls that provide pulldown pressure equal to the

weight of the drill head and in-hole drill tools, and
EARTH MANUAL

126

Figure 2-28.—Photograph of typical rotary drill showing some of the essential equipment for rotary

drilling.(Central Mine Equipment Company)
CHAPTER 2—INVESTIGATION

127

with "hold-back" controls, which apply a back pressure to

the down pressure to reduce applied weight at the bit. All

of these features make the top-head drive rotary drill one of

the most advanced drilling units for high-quality subsurface

explorations.

Top-head drive rotary drills are generally long-stroke drills

capable of a continuous penetration of 3 to 10 m (10 to

30 ft) without requiring additional rods or "rechucking."

Conventional drilling to advance boreholes to specific depths

is normally accomplished using 60 to 140 mm (2-3/8 to

5-1/2 in) outside diameter (o.d.) drill rods. For drilling

stability, maintenance of hole alignment, and efficient

circulation of drill cuttings out of the hole, drill rod

diameter should not be less than one-half the diameter of the

cutting bit. A drill rod/bit combination of a 115-mm-

(4-1/2-in-) o.d. rod and a 200-mm (8-in-) diameter bit

results in a nominal annulus of 44 mm (1-3/4 in) between

the rod and drill hole wall. This size annulus is adequate

for efficient removal of all drill cuttings by high-velocity

circulation of drill fluid while maintaining minimum pump

pressure. For holes larger than 200 mm (8 in) in diameter,

centralizers or stabilizers&about 25 mm (1 in) smaller in

diameter than the bit&should be added to the drill rod string

on approximately 9-m (30-ft) centers. These devices

stabilize the drill string and aid removal of drill cuttings

from the hole through a reduced annulus area.

Downhole percussion hammers are commonly used with

top-head drive drills for rapid penetration through hard

materials and to maintain a better drill-hole alignment than

can be achieved with use of tricone rock bits.

Tricone rock bits are generally rotated 3 to 4 times faster

than a downhole hammer but tend to drift off alignment

when one or more cutting cones contact the edge of a

boulder or other obstruction. Downhole hammers are

operated with air or an air-foam mix as the drilling fluid and

are generally rotated between 12 and 20 rpm. The bit is

slightly concave and embedded with rounded

tungsten-carbide buttons that chip away at the rock with the

rapid in-out percussion impact blows. The slow rotation

and direct impact hit of the single-piece button bit can result

in a truer hole alignment than using a 3-roller tricone bit.

Under reamer percussion, bits also allow rapid drilling or

casing through overburden materials.

In subsurface exploration programs, top-head drive drills

are commonly used to install ground-water monitoring

systems and structural-behavior monitoring instruments.

They are used for geothermal investigations, drilling waste

injection wells, and to recover large-diameter samples of

surficial deposits or rock core. When continuous cores are

required, a large-diameter wire-line system should be used

to enhance the efficiency of the operation and to eliminate

the need for removing all drill rod from the hole for core

recovery.

In all coring operations using air-foam as the circulation

media, the o.d. of the core bit must be sized to drill a hole

no less than 22 mm (7/8-in) larger in diameter than the o.d.

of the drill rod. Water or low-viscosity drill mud

circulation could be accomplished with a core bit no less

than 13 mm (1/2-in) larger diameter than the o.d. of the

rod.

Hole diameters using top-head drive drills generally range

from 150 to 600 mm (6 to 24 in); depth capabilities may

range from 460 to more than 1,525 m (1,500 to 5,000 ft).

Figure 2-29 shows a top-head drive drill with head in mast.

3. Hollow-Spindle Drills.&The hollow-spindle drill

is a multiple-use drill developed for rapid changeover from

auger drilling to rotary or core drilling operations.

Basically, the hollow-spindle transmits rotary drive power,

pull down, and retract to the specific drill tools being used.

Unlike other rotary drills designed to drill only with tubularshaped drill rods or heavy-duty Kelly bars, the hollowspindle drillhead was designed for attachment of a flight

auger or hollow-stem auger drive head. Manual or

hydraulically activated chuck assemblies can be used to

clamp tubular drill rods, or automatic chuck assemblies for

clamping and drilling with fluted Kelly drive bars.

Another advantage of a hollow-spindle drill is that the

spindle opening provides access for passage of sampling

tools or of testing tools through larger-diameter drill rod or

through the hollow-stem auger without having to

disassemble major equipment. This is especially

advantageous with hollow-stem auger drilling, wire-line

core drilling, or penetration resistance testing operations.

Hollow-spindle drills are manufactured either with variablespeed hydraulic drillheads or mechanically driven drillheads

with multiple rotary-speed transmissions. Pulldown feed

rate and retraction are hydraulically controlled and can be

set to automatically maintain a constant rate of feed and

pressure on the drill bit. Hollow-spindle drills are

manufactured with capability to drill 1.7 to 1.3 m (6 to

11 ft) in a single feed stroke without having to add drill rods

or rechuck to achieve additional depth.

A wide variety of sampling and in-place testing operations

can be performed with a hollow-spindle drill. Disturbed

samples can be obtained by flight auger drilling.

Undisturbed samples can be obtained using 75 to 125 m
EARTH MANUAL

128

Figure 2-29.—Top-head drive drill with head-in mast for drilling.

(3 to 5 in) thinwall push tubes or with soil samplers

designed to lock within the hollow-stem auger and

simultaneously recover a soil core sample with advancement

of the auger. Large-diameter undisturbed soil samples [100

to 150 mm diameter (4 to 6 in)] can be recovered using drill

mud or air-foam circulation media and conventional soilsampling core barrels. The hollow-spindle design also

permits piston sampling of noncohesive sands or sampling

of saturated soils with sampling tools that require an inner

rod within the drill rod. Rock coring operations can be

performed using wire-line systems or conventional core

barrels with water, air, or air-foam circulation media.

In-place testing can be conducted from within the hollowstem auger or casing without major equipment changeover.

Specific in-place tests, which can be efficiently performed
CHAPTER 2—INVESTIGATION

129

with a hollow-spindle drill, are vane shear, penetration

resistance, flat plate dilatometer, and hydraulic Dutch-cone

testing.

Hollow-spindle drill holes generally do not exceed 200 mm

(8 in) in diameter. Depth capabilities vary:

 ̆ 45 m (150 ft) approximately, through surficial

deposits with a hollow-stem auger,

 ̆ 60 m (200 ft) through surficial deposits with a flight

auger,

 ̆ 245 m (800 ft) through surficial deposits and bedrock

with a 150-mm- (6-in-) diameter rotary bit, and

 ̆ up to 305 m (1,000 ft) through bedrock with a

75-mm- (3-in-) diameter wire-line coring system.

4. Fluted Kelly Drills.&Figure 2-30 shows a fluted

Kelly drill setup. A rotary drill equipped with a fluted Kelly

rod is designed to continuously drill 3 to 9 m (10 to 30 ft)

(depends upon length of Kelly rod) without having to add

additional drill rods. The Kelly rod is a thick-walled tubular

steel rod with 3 or 4 semicircular grooves milled on equally

spaced centers into the outer wall of the rod and parallel to

the longitudinal axis of the rod. The milled grooves (flutes)

run continuously along the total length of the Kelly rod

except through the upper and lower tool joint connections.

Drills equipped with fluted Kelly rods are generally

designed so rotational power is supplied to the Kelly rod

through combined use of a stationary drillhead and rotary

quill. The quill is equipped with automatic pulldown to

apply downward pressure and a Kelly drive bushing for

rotational drive to the Kelly rod. The Kelly drive bushing

contains hardened steel pins sized to fit into the rod flutes

which transmit rotational drive power to the Kelly rod.

While rotational torque is being applied by the drive bushing

pins within the flute grooves, the Kelly rod has unrestricted

up or down movement throughout the total length of the

flutes. Hole advancement is accomplished by engaging the

automatic pulldown to clamp and apply hydraulically

controlled down pressure to the Kelly rod. It is common

practice to disengage the automatic pulldown, in relatively

easy drilling material, and let the weight of the total drill

string (Kelly rod, attached drill rods, and bit) advance the

hole with holdback control maintained by braking the drawworks hoist cable attached to the top of the Kelly rod.

(Draw works: an oil-well drilling apparatus that consists of

a countershaft and drum and that is used for supplying

driving power and lifting heavy objects.)

Fluted Kelly drills are commonly used for subsurface

exploration to bore 150- to 200-mm- (6- to 8-in) diameter

holes through surficial deposits and bedrock, to set casing,

and to recover large-diameter 100- to 150-mm (4- to 6-in)

undisturbed soil or rock cores with conventional core

barrels. Usually, drill mud or air-foam is used to remove

cuttings. A fluted Kelly drill is not considered efficient for

exploration programs where continuous core recovery is

required because they are not generally equipped for wireline core operations. This limitation significantly reduces

coring production because all rods and the core barrel must

be removed from the hole after each core run.

Fluted Kelly drills are best used for drilling and installing

water and/or wells. Hole sizes may be drilled to 300 mm

(12 in) in diameter and to depths ranging from 300 to 450 m

(1,000 to 1,500 ft). 

5. Reverse-Circulation Drills.&A reversecirculation drill (rotary and percussion) is a specialized

rotary or percussion drill that uses a double-walled tubular

drill rod. The circulation drilling media, compressed air or

air-foam, is forced downhole through the annulus between

the inner and outer rod wall. For a reverse-circulation

rotary drill, the circulation media is ejected near the tool

joint connection between the rotary bit and the center rod.

The media circulates around the outside face of the bit to

cool the bit and moves drill cuttings upward through a

center opening in the bit. The cuttings are forced up the

center tube to a discharge point at the hole collar. For a

reverse-circulation percussion drill, the circulation media is

ejected just above the drive shoe on the outer rod. The

circulation media forces drill cuttings in the drive shoe

upward through the center tube to a discharge point at the

hole collar, as shown in figure 2-31 from reference [34].

The reverse-circulation rotary drill uses a hydraulically

powered top-head drive drillhead and hydraulic

pulldown/retract system. This drill is especially useful for

drilling through loss circulation zones (loose sands, voids,

etc.), for recovering uncontaminated disturbed samples, and

for testing water aquifer yield. Drill depths to 300 m

(1,000 ft) can be achieved using a dual-wall drill rod with an

o.d. of 140 mm (5-1/2 in) and a center tube inside diameter

of 80 mm (3-1/4 in).

The reverse-circulation percussion drill uses an air- or

diesel-powered pile drive hammer to drive dual-wall drive

pipe ranging from 140 mm o.d. (5.5 in) outer tube by

83 mm i.d. (3.25 in) inner tube to 610 mm o.d. (24 in)

outer tube by 305 mm i.d. (12 in) inner tube. Depth

capabilities range from 15 m (50 ft) (with the 610-mm o.d.

drive pipe) to 105 m (350 ft) (with the 140-mm o.d. drive

pipe). This drill is especially good for drilling gravel to
EARTH MANUAL

130

Figure 2-30.—Fluted Kelly drill setup. Automatic pull-down chuck 

assembly and breakout table.
CHAPTER 2—INVESTIGATION

131

Figure 2-31.—Dual-wall reverse-circulation method.
EARTH MANUAL

132

boulder-size material and for recovering uncontaminated

disturbed samples of sand, gravel, and cobble-size material.

Another advantage of a reverse-circulation percussion drill

and dual-wall drive pipe system is that the drive pipe can be

used as a temporary casing through coarse aggregate

deposits. Smaller drills then can be set over the casing to

conduct coring operations, perform in-place tests, or install

subsurface instrumentation systems.

A special version of a reverse-circulation drill known as the

"Becker" drill uses a double-acting diesel hammer.

Research is being performed to obtain penetration resistance

test data using this drill to evaluate loose or dense conditions

in gravels. Reclamation has used these drills on several

dam investigations for evaluating the penetration resistance

of gravels.

6. Top-Head Drive With Percussion Casing

Hammer Drills.&This drill is essentially the same as the

conventional top-head drive drill previously described

except it is equipped with an automatic casing hammer.

Addition of an automatic casing driver allows equipment to

be used to simultaneously advance casing during rotary

drilling operations. This is especially advantageous when

drilling through materials susceptible to caving or squeezing

such as sand-cobble-boulder strata, saturated sands, and soft

saturated silts and clays.

Automatic casing drivers are designed for use only with tophead drive rotary drills. The casing driver has a circular

opening through the center of the driver assembly so drill

rods can rotate inside the casing. This permits simultaneous

drilling advancement with casing advancement. As the

casing driver lowers during percussion driving of the

casing, the drillhead also lowers to ream a pilot hole for the

casing drive shoe and cuttings are removed from within the

casing; see figure 2-32 [34].

The compressed-air-powered driving ram is designed to

impact the casing drive anvil with a driving energy ranging

from 1750 N-m (1,300 lbf) for the smaller drivers, to 10000

N-m (7400 lbf) for the larger drivers. Circulation media for

removing cuttings is compressed air or air-foam. Cuttings

travel upward through the casing to a discharge spout that is

a component of the casing driver.

Casing can be removed using the casing driver to drive

upward for impact against a pulling bar anvil positioned in

the top of the driver assembly. The bottom of the pulling

bar, opposite the upward-drive anvil, is connected to an

adaptor "sub" for attachment to each section of casing.

Casing driver systems are very efficient in terms of

production. Production rates of up to 60 m (200 ft) per day

can be realized. They are very advantageous for instrument

installations where the goal of the program is to rapidly

produce a boring, and sampling or testing can be performed

along the way through the casing. Some casing driver

systems are equipped with underreaming downhole

hammers. The hammer has an eccenetric bit that can cut a

borehole slightly larger than the casing; and, in some cases,

the casing can be dropped under its own weight. These

systems are useful in deposits containing cobbles and

boulders and are often used for drilling rockfill sections of

embankments.

Casing drivers can be operated using several methods.

The casing advancer has an advantage that the casing

maintains an open hole and prevents caving and possible

blocking of circulation which could result in fracturing

problems. One method to reduce the potential for hydraulic

fracturing of embankments consists of using a rotary rock

bit which is kept inside of the casing so that a small soil

plug in the end reduces the possibility of fracturing (see

section 2-12 for drilling methods in existing dams). This

technique is used when drilling impervious zones of dams.

When cobble, boulder materials, or bedrock is encountered,

the bit or a downhole hammer must be extended past the

casing. 

After backfill is placed to a height of about 9 m (30 ft)

above the hole bottom, 3 to 9 m (10 to 20 ft) of casing is

removed followed by continuation of backfilling. This

procedure leaves the upper part of the backfill within the

casing at all times to prevent any caved material from

damaging the instrument or contaminating the backfill. The

percussive blows of the casing driver contribute to

consolidation of backfill material by vibrating the casing

during removal.

The action of the casing driver can be similar to

displacement piles if the bit is withdrawn inside the casing

during hole advance. Some soil is displaced laterally as the

casing is advanced, and corresponding vibrations may

cause densification of surrounding soils. The zone of

influence is assumed to be small (300 to 900 mm [1 to 3 ft])

when adequate precautions are taken, but influence may

affect testing between closely spaced boreholes (i.e.,

crosshole shear wave velocity which is normally performed

at 3-m [10-ft] spacings). Densification effects may be more

pronounced in loose cohesionless soils.
CHAPTER 2—INVESTIGATION

133

Figure 2-32.—Casing drivers can be fitted to tophead drive rotary rigs to simultaneously drill and

drive casing. (Aardvark Corporation)
EARTH MANUAL

134

Figure 2-33.—Horizontal rotary drill. Aardvark model 500 drill

 with adjustable box-beam slide, crawler-tractor mounted.

7. Horizontal Rotary Drills.&Special self-propelled

horizontal rotary drills are used to install perforated or

slotted pipe drains to stabilize water-saturated landslide

areas. The success of this innovative idea resulted in

development of specialized drilling equipment and slotted

polyvinylchloride drainpipe. Horizontal rotary drills are

crawler tractor-mounted for all-terrain mobility and are

designed with proper mass distribution for stability to

provide the required horizontal thrust. The track carrier

power unit provides mechanical tracking power for the

tractor and for total hydraulic power for the drill unit. The

rotary drillhead is positioned on a box-beam slide attached

to the side of the tractor. The slide can be positioned by

hydraulic cylinders to drill at any angle from vertical

downward to 45( above horizontal. Drilling is continuous

over a 3-m travel length of the drillhead on a smooth plane

surface of the beam slide. Forward thrust and retract of the

drillhead is hydraulically controlled through combined use

of a hydraulic ram, equipped with wire rope sheave wheels,

and a cable (wire rope) attached to the drillhead.

Drilling is accomplished using a custom-size drill rod,

57 i.d. by 76-mm o.d. (2-1/4 by 3 in), or 114 i.d. by 127-m

o.d. (4-1/2 by 5 in). The smaller rod is used to install

50-mm (2-in) diameter slotted polyvinylchloride drain pipe;

the larger rod is used to install up to 100-mm- (4-in-)

diameter drain pipe, piezometers, or inclinometer casing.

Special carbide tipped drag bits or tricone bits are locked to

a drill sub on the lead rod that is manufactured with two

L-shaped slots milled into opposite sidewalls of the drill

subbody. The bit shank (threaded tool joint connection of

the bit body) is welded to a tubular steel sleeve that is milled

with an inside diameter slightly larger than the o.d. of the

L-slotted drill sub. A hardened steel pin is welded across

the inside diameter of the bit sleeve for locking into the

L slots of the sub. The bit is attached for drilling by

pushing the bit sleeve over the drill sub to bottom contact of

the hardened pin into the L slot and locked by one-quarter

turn in the opposite direction of the drilling rotation.

Figure 2-33 shows an Aardvark- model 500 horizontal drill

in operation.
CHAPTER 2—INVESTIGATION

135

Drilling for drain installations, such as landslides, is

performed using water as the circulation media to remove

cuttings. Horizontal or angle drilling into slide zones is

generally a high-production operation [average drilling

penetration rate is 2.5 to 3 m/min (8 to 10 ft/min)],

primarily because of the saturated and loose condition of the

material. Holes can be drilled to 245-m (800-ft) depths

(horizontally or nearly so) using a 114-mm (4-1/2-in) bit for

the 76-mm- (3-in-) o.d. drill rod, and to 150-m (500-ft)

depths using a 165-mm (6-1/2-in) bit for the 127-mm-

(5-in-) o.d. drill rod. Drain installations are commonly

drilled in a fan pattern through the slide material or wet

area.

After the hole is completed to the designed depth, the drill

head is unthreaded from the drill rod, and slotted

polyvinylchloride drain pipe is installed within the drill rod

to contact with the drill bit at the end of the hole. A oneway check valve assembly, positioned behind the discharge

ports of the bit, inhibits entrance of ground water or drill

cuttings into the rod during drain pipe installation. Drain

pipe installation into the drill rod is measured to equal total

hole depth plus 1 m (3 ft) to ensure the water discharge

point is outside the hole collar. The drill head is power

threaded onto the drill rod containing the slotted drain pipe,

and an additional 300 to 460 mm (1 to 1-1/2 ft) of drilling

penetration is made without using circulation media. This

operation forces dry cuttings to plug and seize the drill bit

so that it can be detached from the drill rod. After the dry

drilling, water is pumped into the drill rod to about

2070 kPa (300 lbf/in2

) pressure behind the plugged bit. A

reverse rotation on the drill rod unlocks the expendable bit

from the L-slot drill sub. This is followed by a rapid (high

power) pullback on the drill rod while monitoring pump

pressure for indication of a sudden pressure drop. The

pressure drop confirms bit drop off, which is immediately

followed by rapid withdrawal of the drill rods. The bit cost

is insignificant when compared to cost of removing all drill

rods, saving the bit, and attempting to install drain pipe into

a hole that has collapsed. As the rods are withdrawn, the

drain pipe is maintained in the hole (against the expendable

bit) by continuing to inject water against a floating piston

device seated against the outlet end of the drain pipe. This

floating piston maintains pressure on the drain pipe to

prevent withdrawal of the drain during rod removal. After

all rods are removed, the drain discharge is plumbed into a

manifold pipe assembly and conduit to direct the water away

from the slide zone or wet slope area.

In addition to drilling for drain installations, horizontal

rotary drills have proved extremely efficient and effective

for use in performing other types of subsurface work

discussed below.

c. Core Drilling for Tunnel Alignment Geology.&A

river diversion tunnel alignment at Reclamation' s Buttes

Dam, Arizona, was horizontally core drilled to a depth of

283 m (927 ft) using a horizontal rotary drill and NWD-3

core-barrel assembly. Core recovery was 98.9 percent.

Production rate was good at an average of 8 m (26 ft) per

workshift; however, the addition of a pump-in wire-line

core barrel would have had the potential to triple

conventional core-barrel production.

d. Slope Inclinometer Casing Installation.&Using a

horizontal rotary drill is a productive and efficient method

for drilling, installing, and grouting inclinometer casing in

place. The drill can be track-walked under its own power

to difficult access sites. The inclinometer hole can be

drilled with a 158-mm (6-1/4-in) expendable bit and a

108-mm- (4-1/4-in-) i.d. drill rod. The inclinometer casing

can be installed to the hole bottom through the largediameter drill rod. After releasing the expendable bit, the

annulus between the hole wall and inclinometer casing can

be grouted by pumping grout through the drill rod. When

grout fills to the hole collar, drill rod can be removed from

the hole to complete the inclinometer casing installation.

After completion, a water-injection pipe should be lowered

to the bottom of the hole inside the inclinometer casing, and

clean water should be circulated to remove any grout that

may have entered through the casing joints.

e. Piezometer Installation.&The drilling and

installation procedure is the same as that described for an

inclinometer casing. However, the backfilling procedure is

modified to be compatible with the type of backfill material

used. Generally, a uniformly graded clean sand is placed

around the piezometer tip or to a specified height above the

slot openings of a well screen. This can be accomplished by

placing in the drill rod a measured volume of backfill

material 28 to 57 liters (1 to 2 ft3

) greater than the volume

required to fill the hole after removal of a single drill rod.

Then, the drill head is threaded onto the collar rod, and one

rod is removed while rotating slowly while clean water is

simultaneously pumped to force the backfill out of the rod.

This procedure leaves 300 to 600 mm (1 to 2 ft) of material

in the bottom rod and protects the piezometer from an open

hole condition and possible caving. The backfill and rod

removal procedure is repeated in like increments to

completion of the hole.

f. Settlement-Plate Monitoring Systems.&

Reclamation' s Choke Canyon Dam, Texas, was constructed

with 0.84-m2

 (1-yd2) steel settlement plates embedded at the

interface between the embankment and compacted

overburden material just below the embankment. After

completion of embankment construction, a horizontal rotary

drill was set on the 3:1 (horizontal : vertical) downstream
EARTH MANUAL

136

slope face to drill and install a steel reinforcement

measurement rod to contact on the plate for survey

monitoring of embankment settlement. Drilling was

conducted using 76-mm- (3-in-) o.d. rod and a 108-mm

(4-1/4-in) drag bit with water circulation media. The plates

were located at six separate stations along the embankment

at an average depth of 43 m (140 ft). After the bit contacted

each plate, the rods were pulled and the bit removed.

The second drill phase was conducted with an open drill sub

on the lead rod to contact the steel plate. The 50-mm-

(2-in-) diameter casing pipe was lowered through the drill

pipe to plate contact. A bentonite seal was injected to the

bottom of the hole during removal of a 3-m (10-ft) rod

section. The bentonite was used to seal the casing to inhibit

grout intrusion. The installation was completed by filling

the annulus between the casing and hole wall with grout

from the top of the bentonite seal to the hole collar. After

removal of all drill rods from the hole and initial grout set,

a reinforcement steel rod was installed through the casing to

plate contact. The top of the steel rod is a survey point to

monitor embankment settlement.

g. Churn/Cable-Tool Drills.—Although incapable of

performing rotary drilling operations, the churn drill or

cable tool is sometimes used in lieu of, or in combination

with, rotary or core drills. The churn/cable-tool drilling

procedure is one of the oldest known methods of boring

holes and continues to be a favored method to drill water

wells. Drilling is performed by raising and dropping a

heavy string of tools tipped by a blunt-edge chisel bit. The

tools are attached to a steel cable that is alternately raised

and released for free fall by a powered drum assembly. The

cable is suspended from a sheave assembly mounted on an

oscillating beam that absorbs the shock load created by

quick load release on the taut cable upon impact of the drill

tools in the bottom of the hole. The impact of the bluntedge chisel pulverizes soil and rock material, and the

borehole is advanced. The cuttings are suspended in a

slurry injected into the borehole. After each 3- to 6-m (10-

to 20-ft) penetration, the cable tools are hoisted out of the

hole, and a cylindrical bailer equipped with a bottom check

valve is lowered into the hole to remove the slurry. This

process is repeated to total hole depth.

A sampling barrel also can be attached in place of the bluntedge chisel bit. In this mode, the churn/cable-tool drill can

be used to sample and to advance the hole without using

water, resulting in a muddy hole. The sampler mode has

been used to advantage in sampling glacial terrains where

great thicknesses of heterogeneous surficial deposits overlie

bedrock. The sampler mode of churn/cable-tool drilling

has also been used to advantage for sampling and

instrumenting dam embankments.

The churn/cable-tool drill is sometimes used to drill and

then drive casing pipe through cobble-laden or fractured

material so core drilling of deeper formation material can be

done with diamond-core drills. When vertical hole

alignment is critical, the churn/cable-tool drilling method is

very effective. The churn/cable-tool drill was used

successfully by the petroleum industry to drill 380-mm-

(15-in-) diameter holes to depths of 2,000 m (7,000 ft).

Simplicity of equipment makes churn/cable-tool drilling

operations one of the least expensive methods for boring

holes.

h. Rock Core Drilling.&Rock core drilling is

accomplished with mechanical, engine-powered rotary drills

designed to drill rock and to recover cylindrical cores of

rock material. Most core drilling equipment is designed with

gear or hydraulically driven variable-speed hollow-spindle

rotary drill heads (fig. 2-34). Average core-diameter

capability of these drills ranges from 19 to 85 mm (3/4 to

3-3/8 in) and to 300-m (1,000-ft) depths. Larger-diameter

coring operations [100 to 150 mm (4 to 6 in)] are usually

performed using rotary drills, and cores to 1.8 m (6 ft) in

diameter can be drilled and recovered using a shot/calyx

drill.

A general misconception is that for coring operations with

diamond core bits to be efficient, drilling must be performed

at the highest rotary speed®ardless of core size.

However, this operational procedure usually results only in

shortened bit life, poor penetration rate, and excessive

vibration that results in broken cores or core blockage.

Diamond drill manufacturer’s literature serves as an

excellent guide for selecting bit styles and evaluating bit

wear [32, 35, 36].

Diamond-core drilling can be compared to using drill

presses or center-bore lathes in a machine shop. A smalldiameter drill bit must be rotated at high speed with

minimum pressure applied to the bit, while a large diameter

drill bit must be rotated at a low rate of speed with

significant pressure on the bit. Any variation from this

procedure results in bit chatter, dulled drill bits, and poor

penetration rate. The same is true for a core drilling

operation. Rotational speed and "crowd" pressure must be

compatible with type and hardness of rock being drilled to

achieve a smooth and steady rate of penetration throughout

the core length. Any variation results in loss of extremely

expensive core bits, poor production, and poor quality core

recovery.

All core drills are equipped with pumps or compressors to

circulate drill media through use of water, drilling mud, air,

or air-foam to cool and lubricate the coring bits and to

transport the drill cuttings to the top of the hole. Most core
CHAPTER 2—INVESTIGATION

137

Figure 2-34.—Typical diamond drilling rig for exploration. (Acker Drill Co., Inc.)
EARTH MANUAL

138

drills are equipped with a mast assembly, powered hoist

assembly for hoisting heavy loads, and, sometimes, a wireline hoist assembly for hoisting or lowering a wire-line core

barrel through the drill rods.

Although some core rigs have been manufactured with gear

or chain pulldown/retract systems, precise control over bit

pressure can best be accomplished with a hydraulic

pulldown/retract system. The hydraulic system must have

a precision regulator control so desired pressure can be set

and maintained on the bit. Deep-hole rigs should be

equipped with a hydraulic holdback control so the full

weight of the drill tools is not exerted on the drill bit.

Many variations are available in design and mountings for

drill rigs manufactured specifically for corin; however, there

are only two basic types. They are conventional or wireline core drills, for drilling and recovering cores up to 150

mm (6 in) in diameter, and shot/calyx core drills for

drilling, and recovering cores to 1.8 m (6 ft) in diameter.

1. Conventional and Wire-line Core Drills.&

Conventional and wire-line core drills are capable of highspeed rotary core drilling (up to 1,800 rpm) for recovery of

relatively small-diameter cores ranging from 19 to 150 mm

(3/4 to 6 in) in diameter; however, wire-line core recovery

is limited to 86 mm (3-3/8 in) in diameter.

Conventional core drilling is performed using standard

rotary drill rods and a core barrel. After each core run, all

rods and core barrel must be removed from the hole to

recover the core. A wire-line core drill uses large insidediameter drill rods through which an inner-core barrel

assembly is lowered by wire-line cable and locked into a

latch mechanism in the lead rod. After each core run, an

"overshot" tool is lowered by wire-line to unlock and

retrieve the inner-barrel assembly for core recovery.

Conventional core drilling is usually limited to relatively

shallow coring depths or when intermittent core runs are

separated by intervals of hole advancement by rock bitting.

 However, the nonrecovery advancement of boreholes

between coring intervals also can be achieved with a wireline system by removing the inner core barrel and lowering

a rock bit&designed with a wire-line latching

mechanism&into the wire-line drill rod.

Wire-line equipment is especially valuable in deep hole

drilling since the method eliminates trips in and out of the

hole with coring equipment. Figure 2-35 illustrates the

working components of the wire-line core barrel. With the

wire-line technique, the core barrel becomes an integral part

of the drill rod string. The drill rod serves as both coring

device and casing, and usually is not removed except when

making bit changes. Core samples are retrieved by

removing the inner-barrel assembly from the core barrel

through the drill rod. This is accomplished by lowering an

overshot or retriever, by wire-line, through the drill rod to

release a locking mechanism built into the inner-barrel head.

The inner barrel is brought to the surface; the core is

removed, the inner barrel is returned to the bottom of the

hole through the drill rod, and coring is continued.

Other advantages of wire-line core drilling over

conventional core drilling are:

 ̆ Production & Wire-line core drilling is three to four

times faster.

 ̆ Hole Protection & The larger drill rod functions as a

casing to protect the hole from caving material or

squeezing zones at all times.

 ̆ Drilling Stabilization & The wire-line drill rod helps

to eliminate rod vibration and rotational whipping

action by minimizing the open hole annulus between

the outside of the rod and the hole wall.

 ̆ Extended Bit Life & The only time wire-line rods

must be removed from a core hole is to replace a

worn core bit. Rod trips in and out of a core hole, as

with conventional core drilling operations, reduce bit

life because the o.d. gauge stones (diamonds) on the

bit are in contact with abrasive rock formations

during rod "tripping" operations. This is especially

true during angle or horizontal hole conventional

coring operations. In addition, removal of rods from

the hole may cause rock fragments to loosen and fall

or wedge in the hole. As a result, reaming through

the fallout material is necessary while the rods are

lowered to the hole bottom.

 ̆ Water Permeability Testing & Water testing through

a wire-line rod can be accomplished by hoisting the

rod above the test interval, then lowering a wire-line

packer unit through the bit for expansion and seal

against the hole wall. Conventional core drill

operations would require removal of all rods and core

barrel before setting the packer at the zone to be

tested.

Some core drills are designed with angle-drilling

capabilities, including up-hole drilling with underground

drills used in the tunneling and mining industry. Angle-hole

drills are generally small and can be quickly disassembled

for moving by helicopter or other means into areas of rough

terrain. Core drills can be mounted on motorized carriers,

trailers, skids, or stiff-leg columns for underground

operations.

Core drills have limited capability for drilling through

gravels, cobbles, or any surficial material that requires
139

Figure 2-35.—Wire-line core barrel operation.
EARTH MANUAL

140

significant rotary torque. Generally, casing must be set

through surficial materials to preclude hole caving and loss

of drill fluid circulation. Core drill depth capabilities are

limited mainly by hoisting capacity of the mast and draw

works and by the ability to maintain a clean hole free of

cuttings.

2. Shot or Calyx Drills.&A shot drill, also called a

calyx drill, is a large rotary drill used primarily in largediameter (0.1 to 2 m [4 to 6 ft]) rock or concrete core

drilling operations. After development and use of industrial

diamond-core bits, the shot or calyx drill became obsolete

in the United States, but still is used in some European and

Asian countries. The primary differences between a

shot/calyx drill and rotary core drills previously discussed

are the tools and methods used to perform core drilling

operations. Coring is performed using a coring bit that is

a flat-face steel cylinder with one or two diagonal slots cut

in the bottom edge. As the bit and core barrel are rotated,

small quantities of hardened steel shot (also called

adamantine shot, buckshot, chilled shot, or corundum shot)

are fed at intervals into the drill-rod water injection system.

The water circulation media flows through the core barrel

around the bit face for cooling and return circulation of

cuttings, leaving the heavier steel shot on the hole bottom.

The rotating core barrel creates a vortex at the bit, which

results in movement of steel shot under the flat face of the

bit. As the core bit rotates, the steel shot aids in coring

penetration by abrasive cutting action on the rock.

A steel tube called a calyx barrel is attached to the upper

(head) end of the core barrel. The o.d. of the calyx barrel

is the same as that of the core barrel; the calyx barrel serves

as a stabilizing guide rod for the core barrel. The top end

of the calyx barrel is open except for a steel yoke welded

across the inside diameter of the barrel to a steel ring

encircling the drill rod. In addition to functioning as a

stabilizer for the core barrel, the calyx barrel functions as a

bucket to catch and contain drill cuttings too heavy for

circulation out of the hole by drill water. Cores are

recovered by hoisting all rods and the core barrel out of the

hole using a cable draw-works system.

Depth limitation for a shot/calyx drill depends on the mast

and draw works hoist capacity and on capability to maintain

a clean open hole. Although smaller-diameter cores can be

drilled with a shot/calyx drill, costs would be much higher

than diamond drilling. Only on jobs where large-diameter

[1 to 2 m (3 to 6 ft)] cores are required would efficiency and

price be comparable for diamond and for shot drilling.

i. Planning a Drilling Program.&Planning is critical

to the success of a rotary drilling program. Engineering

Geology Field Manual [20] provides guidance on planning

a drill program. An investigation program with drilling

operations program can be a major cost, and proper

planning is required to ensure that the program can be

performed without cost overruns. In planning a drill

program, important areas to consider include:

 ̆ preplanning,

 ̆ site visit,

 ̆ topography and accessibility,

 ̆ protection of the environment,

 ̆ drilling concerns,

 ̆ equipment concerns,

 ̆ traffic control and safety plans,

 ̆ buried and overhead utilities,

 ̆ special considerations, and

 ̆ preparation of drilling specifications.

2-12. Procedures for Drilling in Embankment

Dams.&Concern exists throughout the geotechnical

community regarding drilling in embankment dams and the

potential for hydraulic fracturing of the impervious core

during drilling. This concern has prompted an evaluation of

conditions and drilling methods which pose the greatest

potential for hydraulic fracturing. The following procedures

should be followed when drilling in the impervious portions

of embankment dams.

a. Conditions Conducive to Hydraulic Fracturing.&

Reclamation’s embankment design and construction

practices, historically as well as currently, minimizes

development of stress patterns within an embankment caused

by drill fluids during drilling. However, certain

embankment locations and conditions have a higher potential

for hydraulic fracturing than others, and improper drilling

procedures or methods increase the potential for fracturing.

Site locations and conditions where hydraulic fracturing by

the drilling media are most likely to occur include the

following:

 ̆ Impervious cores with slopes steeper than 0.5H:IV,

within cutoff trenches, and upstream inclined.

 ̆ Near abutments steeper than 0.5H:IV; where abrupt

changes in slopes occur; or above boundaries in the

foundation which sharply separate areas of

contrasting compressibility.

 ̆ Near rigid structures within embankments.

 ̆ Impervious zones consisting of silt and mixtures of

fine sand and silt.

b. Recommended Procedures.&Recommended

procedures for developing exploration and instrumentation

programs and for drilling in the impervious portion of

embankment dams are as follows:
CHAPTER 2—INVESTIGATION

141

 ̆ A site-specific determination as to whether hydraulic

fracturing potential exists should be made by

exploration team.

 ̆ If a potential for hydrofracturing exists, the type of

equipment and the method and technique proposed to

be used must have the approval of the exploration

team. Once drilling has commenced, drilling

personnel are responsible for controlling and

monitoring drill media pressure, drill media

circulation loss, and penetration rate to assure that the

drilling operation minimizes the potential for

hydraulic fracturing.

 ̆ If a sudden loss of drill fluid occurs during any

embankment drilling in the impervious core, drilling

should be stopped immediately. The reason for the

loss should be determined; and if hydraulic fracturing

may have been the reason for the fluid loss, the

Principal Designer and Principal Geologist should be

notified. Action should be taken to stop the loss of

drill fluid.

c. Acceptable Drilling Methods.&Based on the

evaluation of the various drilling methods, with the

exception of augering, any drilling methods have the

potential to hydraulically fracture an embankment if care

and attention to detail are not taken.

Augering is the preferred method of drilling in the core of

embankment dams. Augering does not pressurize the

embankment, and no potential for hydrofracturing exists.

Use of a hollow-stem auger permits sampling of the

embankment and the foundation through the hollow stem

with the auger acting as casing.

With proper planning, the following drilling methods may

be approved for drilling in embankment dams if augering is

not practical:

 ̆ cable tool

 ̆ mud rotary (bentonite/biodegradable)

 ̆ drilling with water

 ̆ air-foam rotary

 ̆ reverse-circulation percussion/rotary

 ̆ rotary percussion

Selection of any one of the above methods should be based

on site-specific conditions, hole utilization, and availability

of equipment and trained personnel. Any drilling into the

impervious core of an embankment dam should be

performed by experienced drill crews that employ methods

and procedures that minimize the potential for hydraulic

fracturing. Therefore, it is essential that drillers be well

trained and aware of the causes of and the problems

resulting from hydraulic fracturing.

Because hydraulic fracturing can be induced when in-place

horizontal stress and tensile strength in the embankment

material are less than fluid or gas pressure, general practice

is to limit downhole pressures of circulation media to 1 to

2 kPa/m [1⁄2 to 1 (lbf/in2

)/ft] of depth of drill hole drilling

operations. Advance rates should be slow to ensure that

blocking of the bit or barrel does not occur. Drill rod and

hole diameter should be selected to ensure appropriate

annulus for efficient cuttings removal. Circulation pressures

should be monitored continuously during the drilling

process.

Rotary percussion and reverse-circulation drills can induce

fracture by air pressure. General precautions to reduce

fracture potential include reducing air pressures and

maintaining lead distance of casing shoe well in advance of

the downhole hammer or inner casing. Rotary percussion

and reverse-circulation drilling can normally circulate

cuttings efficiently with air pressures of 100 to 200 kPa (15

to 30 lbf/in2

).

In cases where steep abutment contacts are encountered, the

static weight of fluid column alone may be sufficient to

induce hydraulic fracture without any excess hydrostatic

pressure. In these cases, the only successful method for

advancing a drill hole without fracturing is to incrementally

drive casing and perform cleanout inside the casing, while

leaving a sufficient plug of soil in the casing to prevent

exposure of drill media with the consequent transmission of

excess pressure to the embankment.

C. Sampling and Testing Methods

2-13. General.&Sampling serves many purposes

when investigating foundations and evaluating construction

materials for water resources structures. Samples are

required to accurately identify and classify soil or rock.

Samples are essential for obtaining in-place density and

moisture content, for performing laboratory tests on earth

and rock materials, for testing potential concrete sand and

aggregate deposits, for designing concrete mixes, and for

testing potential riprap sources. Data obtained from

laboratory testing of samples are used to finalize the design
EARTH MANUAL

142

of foundations and embankments and to select construction

materials for use in earth and concrete dams and in other

structures.

The importance of obtaining representative samples cannot

be overemphasized. Samples that are not truly

representative of in-place subsurface conditions can result in

erroneous conclusions that affect the design of the structure.

Sample recovery requires considerable care to avoid altering

in-place conditions of natural deposits. Obtaining

representative samples from accessible trenches, test pits, or

tunnels is relatively easy because in-place material can be

visually inspected to determine the best method of sampling

by hand. However, in boreholes, visually inspecting inplace material is not possible; consequently, the recovery of

representative samples is more difficult.

Samples are broadly classified as either disturbed or

undisturbed. Disturbed samples do not reflect the in-place

condition of the soil or rock. Obtaining undisturbed

samples requires significant experience and meticulous care

to maintain in-place material conditions. Even using the

most careful procedures, undisturbed soil or rock samples

are changed from their in-place condition because removing

them from parent material changes stresses which confine

the sample.

Both hand and mechanical sampling methods commonly

used to recover disturbed and undisturbed subsurface

samples are described in the following paragraphs.

2-14. Hand Sampling Methods for Obtaining

Disturbed Samples.&Disturbed Samples (hand-sampling

methods) are normally used to obtain samples from

accessible excavations, from existing stockpiles and

windrows, or from shallow hand-auger borings.

a. Accessible Test Pits, Trenches, and LargeDiameter Borings.&Using methods described in

USBR 7000, obtaining disturbed samples from accessible

test pits or trenches (including road cut and river bank

deposits) can be accomplished in the following manner:

 ̆ An area of sidewall of the test pit, trench, largediameter boring, or open cut should be trimmed to

remove all weathered or mixed material.

 ̆ The exposed strata should be examined for changes

in gradation, natural water content, plasticity,

uniformity, etc., and a representative area should be

selected for sampling.

 ̆ Sketches and photographs showing changes in strata,

geologic descriptions, and sampling locations should

be recorded.

 ̆ Either individual or composite samples can be

obtained by cutting a sampling trenching down the

vertical face of a test pit, trench, or cut bank with a

sampling cut of uniform cross section and depth.

 ̆ The soil can be collected on a quartering cloth spread

below the sampling trench.

 ̆ The minimum cross section of the sampling trench

should be at least four times the dimension of the

largest gravel size included in the soil.

In obtaining individual samples, it is important that an

adequate sample of representative material be obtained only

from the stratum of interest and that extraneous material is

not included. For composite samples, a vertical sampling

trench is cut through all strata of interest.

If the material sampled is a gravelly soil that contains large

percentages (about 25 percent or more of total material) of

particles 75 mm (3 in) in diameter or larger, it is usually

appropriate to take representative parts of the excavated

material (such as every 5th or 10th bucketful) rather than to

trim the sample from the in-place sidewall of the excavation.

In critical investigations, such as for processed aggregates

or cohesionless soils, screening all oversize may be

necessary to determine volume of oversize cobbles and

boulders&while maintaining a constant width of cut.

Size requirements for disturbed samples for various testing

purposes are given in USBR 5205 for soils and in

USBR 4075 [37] for concrete. The quantity of the field

sample depends on the testing that is to be performed and

the maximum particle size present in the material. When

samples are larger than required for testing, they may be

reduced by quartering as described in USBR 5205 or

USBR 4075. This is done by piling the total sample in the

shape of a cone on a canvas or plastic tarpaulin. Each

shovelful should be placed on the center of the cone and

allowed to distribute equally in all directions. Then, the

material in the cone is spread out in a circular pattern by

walking around the pile and gradually widening the circle

with a shovel until a uniform thickness of material has been

spread across the tarpaulin. The spread sample is then

quartered. Two opposite quarters are discarded, and the

material in the remaining two quarters is mixed again by

shoveling the material into another conical pile, taking

alternate shovelfuls from each of the two quarters. The

process of piling, spreading, and discarding two quarters is

continued until the sample is reduced to the desired size.

b. Stockpiles and Windrows.&When sampling

stockpiles or windrows, care must be taken to ensure that

samples are not selected from segregated areas. Procedures

for sampling stockpiles are given in USBR 4075. The

amount of segregation in materials depends on gradation of
CHAPTER 2—INVESTIGATION

143

the material and on methods and equipment used for

stockpiling. Even with good control, the outer surface and

fringes of a stockpile are likely to be somewhat segregated,

particularly if side slopes are steep and the material contains

a significant amount of gravel or coarse sand.

Representative samples can be obtained from stockpiles by

combining and mixing small samples taken from several

small test pits or auger holes distributed over the entire pile.

A windrow of soil is best sampled by taking all the material

from a narrow cut transverse to the longitudinal axis of the

windrow. Samples from either stockpiles or windrows

should be fairly large originally, and they should be

thoroughly mixed before quartering down to the size desired

for testing.

c. Hand Auger Borings.&Small auger holes cannot be

logged and sampled as accurately as an open trench or a test

pit because they are inaccessible for visual inspection of the

total profile and for selecting representative strata.

Procedures for augering and sampling are discussed in

USBR 7010. Small hand augers [100-mm (4-in) diameter

or smaller] can be used to collect samples adequate for soil

classification and, possibly, for physical properties testing

(fig. 2-36). As the auger hole is advanced, soil from the

hole should be deposited in individual stockpiles to form an

orderly depth sequence of removed material. When

preparing an individual sample from an auger hole,

consecutive piles of the same type of soil should be

combined to form a representative sample. All or equal

parts from each of the appropriate stockpiles should be

mixed to form the sample of desired size for each stratum

(fig. 2-36).

2-15. Mechanical Sampling Methods for

Obtaining Disturbed Samples.&Disturbed Samples

(mechanical sampling methods) using mechanical methods

are often obtained from drilled holes; however, samples also

are obtained using construction excavation equipment

(backhoes, draglines, trenchers, dozers) when they are

required primarily for identification or for making volume

computations of usable material. Samples obtained with

construction equipment are generally unsuitable for use in

laboratory testing because of severe mixing of material that

occurs during the excavation process. Heavy excavation

equipment is best used to excavate an accessible test pit or

trench so individual material stratum can be sampled by

hand methods to avoid contamination from adjacent

materials.

a. Power Auger Drills.&One of the most common

methods of obtaining disturbed subsurface samples is by

using power auger drills. Continuous-flight auger drilling

can be used to obtain disturbed samples of borrow area

materials. As the drill hole is advanced, soil cuttings travel

up the spiral flight of the auger to the collar of the hole, and

soil from selected intervals, or material change, is collected.

Soil cuttings are most efficiently transported up flights when

explorations are performed in partially saturated strata.

When an interval has been reached, auger rotation can be

continued without depth advancement until most of the soil

is brought to the surface. However, soil cuttings moving

upward along the flight can loosen and mix with previously

drilled material. If contamination or mixing with other soil

material is undesirable, a hollow-stem auger with an internal

sampling system should be used.

Disk augers are commonly used to recover disturbed

samples of soil and moderately coarse-grained material.

After each penetration, the disk is removed from the hole

with the disturbed sample cuttings retained on the top of the

disk. Then, the sample collection is made at the hole collar

followed by repeated drilling intervals.

Bucket augers are suitable for recovering disturbed samples

of coarse-grained soils, sands, and gravel deposits. During

each drilling interval, sample cuttings enter the cylindrically

shaped bucket through the bottom cutter block. Removal

and collection of samples are accomplished by hoisting the

bucket from the hole and releasing the hinged bottom plate

or side of the bucket. Samples of gravels and sands

obtained below the water table are normally unreliable

because of loss of soil fines through the bucket openings.

b. Reverse-Circulation Drills.&Reverse-circulation

drills work well for recovering sand, gravel, and cobble-size

disturbed samples. However, this sampling method is

relatively expensive and is not used for borrow area

investigations. These drills use a double-walled drill stem

and compressed air to circulate drill cuttings for collection

at the hole collar. Compressed air is pumped down the

annulus between the inner and outer walls of the doublewalled drill rod, and cuttings are forced upward through the

center rod as drilling progresses. Drill cuttings are collected

at the discharge spout of a special funnel-shaped cyclone

assembly designed to dissipate the energy of the compressed

air and deposit cuttings in the order drilled.

This method of disturbed sampling is considered most

reliable to produce a noncontaminated sample because the

drill stem seals previously drilled material zones.

Normally, coarse gravels and cobbles are broken by impact

of the double wall casing shoe, but this is easily identified

by fresh fracture surfaces. Gradation tests are unreliable if

coarse particle fracturing occurs.

c. Protecting and Preparing Disturbed Samples for

Shipping.&Disturbed samples of 35 kg (75 lbm) or more

should be placed in bags or other suitable containers that
EARTH MANUAL

144

Figure 2-36.—Auger sampling.

prevent loss of moisture or fine fraction from the soil.

Asphalt coated burlap sacks with an inner plastic liner are

commonly used for protecting and shipping disturbed soil

samples. Samples of silty or clayey borrow soils can be

allowed some moisture loss as long as studies show no

irreversible processes occur from air drying. These soils

will be dried in the laboratory for development of

compaction curves. The coated burlap sack with plastic

liner has proved satisfactory for most borrow studies of silty

and clayey soils.

When proposed for use as borrow material, samples of silt

and clay for laboratory testing should be protected against

drying by placement in waterproof bags or other suitable

containers. Sand and gravel samples should be shipped in

closely woven bags and should be air dried before they are

placed in the bags. When sack samples are shipped by

public carrier, they should be double sacked.

2-16. Hand Sampling Methods for Obtaining

Undisturbed Samples.&

a. Undisturbed Hand-Sampling Methods.&

Undisturbed samples in the form of cubes, cylinders, or

irregularly shaped masses can be obtained from strata

exposed in the sides or bottoms of open excavations, test

pits, trenches, and large-diameter auger holes. Such

samples are useful for determining in-place density and

moisture content and for other laboratory tests.

Hand cut cylinder samples and block samples provide the

highest quality undisturbed samples for laboratory testing

and are often preferred in critical studies of weak zones

when access is available. Generally, sampling is only

possible in unsaturated zones because dewatering can cause

increases in effective stress and possible consolidation of
CHAPTER 2—INVESTIGATION

145

Figure 2-37.—Method for obtaining a hand-cut, undisturbed cylindrical sample.

sensitive material. Sampling by hand-carved cylinder

sample is depicted on figure 2-37. An elevated bench is

constructed in a test pit or accessible shaft. A cylinder,

sharpened on one end, is placed on a level surface and is

pressed into the soil as the sample is trimmed with a knife

to a diameter slightly larger than the cutting edge. The

incremental process of trimming and pressing is continued

until the cylinder is overfilled with soil. The sample bottom

can be severed from parent material by spade or shovel and

ends trimmed flush the end of the cylinder. This method is

effective for soils generally wet of laboratory optimum

water content and which contain maximum particle sizes less

than coarse sand.

If soils are very fine-grained and wet, cylinders can possibly

be pushed the complete depth without trimming in advance

of the cutting edge. Several devices such as the U.S. Army

Corps of Engineers drive cylinder or the "Elly Volumeter"

have been developed. Samples can be extruded from

cylinders into laboratory test chambers. Reclamation has

obtained large-diameter cylinders [200 to 300 mm (8 to 12

in)] for testing by pushing into compacted fills. Cylinders

were pushed with drawbars of bulldozers or buckets of front

end loaders. This sampling method may be particularly

effective for compacted clay liners placed wet of optimum

water content.
EARTH MANUAL

146

Figures 2-38 and 2-39 show procedures commonly used to

hand-cut block samples. Cutting and trimming samples to

the desired size and shape requires extreme care particularly

when working with easily disturbed soft brittle materials.

Appropriate cutting tools should be used to prevent

disturbance or cracking of the sample. Soft, plastic soils

require thin, sharp knives. Sometimes a thin piano wire

works well.

A faster and more economical method for obtaining

undisturbed block samples is by use of a chain saw equipped

with a specially fabricated carbide-tipped chain to cut block

samples of fine-grained material and soft rock (fig. 2-40)

(see USBR 7100). Usually, this method results in least

disturbance to a sample because of the saw' s rapid,

continuous cutting action. Diamond concrete saws can cut

gravel particles in a soil matrix effectively, although

considerable precautions must be taken to prevent

disturbance. When using saws, the operators should take

appropriate safety measures, including wearing chaps and

eye and ear protection. Block samples for laboratory testing

are usually limited in size to 300- to 460-mm (12- to 18-in)

cubes to facilitate handling. This size should allow for

sufficient shear, consolidation, and permeability specimens.

Block sampling is routinely performed as record testing of

compacted fill to determine density. Small block samples of

undisturbed soil can be cut from the larger block and coated

with wax and tested in accordance with USBR 5375.

In dry climates, moist cloths should be used to inhibit

drying of the sample. After the sample is cut and trimmed

to the desired size and shape, it should be covered with thin

plastic sheeting (such as Saran Wrap), wrapped with a layer

of cheesecloth, and painted with melted, microcrystalline

sealing wax. Rubbing the partially cooled wax surface with

the bare hands helps seal the pores in the wax. At least two

additional layers of cloth and wax should be applied.

b. Protecting and Preparing Hand-Cut Undisturbed

Samples for Shipping.&As illustrated in figure 2-39, a

firmly constructed wood box with top and bottom panels

removed should be placed over the sample before the base

of the sample is severed from the parent material and lifted

for removal. The annular space between the sample and the

walls of the box should be packed with moist sawdust or

similar packing material. The top cover of the box then

should be placed over the packing material. After the

sample is cut from the parent material, the bottom side of

the sample should be covered with plastic sheeting and the

same number of layers of cloth and wax as the other

surfaces; and the bottom of the box should be placed over

the packing material. Tags and markers should be attached

to the block to denote top, bottom, and orientation. Samples

may vary in size, but most often are 150- to 300-mm (6- to

12-in) cubes. The same trimming and sealing procedures as

described for block samples apply to cylindrical samples.

2-17. Mechanical Sampling Methods for

Obtaining Undisturbed Samples.&Soil samplers used

by Reclamation are designed to obtain relatively undisturbed

samples of soils ranging from saturated, noncohesive soils

to shale or siltstone. Each soil type dictates use of different

types of sampling equipment to effectively recover highquality samples. The following paragraphs describe the

type of sampler best suited for good sample recovery from

various soils.

a. Saturated Cohesionless Soils.&Cohesionless soils

such as poorly graded sands (SP, SP-SM) and silty sands

(SM) are difficult to sample below the water table. This is

due to lack of friction in the inner tube or barrel. Research

has shown that undesirable volume change can occur in

clean sands during insertion of thinwall tubes or piston

samples [38]. This is because the high permeability of clean

sands allows movement of porewater and volume change

results (i.e., drainage can occur). Sand may either dilate or

contract during the sampling process. For sands containing

more than 15 percent fines, undesirable volume change may

not occur if the structure is not sensitive because there is no

drainage due to decreased permeability. For clean sands,

the only successful method to preserve structure is to freeze

the soil before sampling. Freezing can be accomplished

without disturbance in clean sand, but costs are so excessive

that it is infrequently used. Efforts to characterize

engineering properties of cohesionless soils currently depend

on penetration resistance testing such as Standard

Penetration Test or Cone Penetrometer Test.

Efforts have been made to track volume change in sands

during fixed piston sampling. The technique requires use of

piston sampling with inner rods with accurate measurements

of stroke, recovery, and deflection on a reaction frame set

up on a drilling rig. Measurements are made to 3 mm (0.01

ft) on the drill rig frame. Using this procedure,

Reclamation found that predicted volume changes were also

occurring in fine-grained soils. Accuracy and precision of

such an approach has not been established, and Reclamation

is not currently using this procedure.

In situations where cohesionless soils must be recovered,

piston sampling or sampling barrels with baskets or retainers

can be used. A fixed-piston sampler is designed to obtain

a sample within a thin-wall cylindrical tube by pushing the

tube into the soil with an even and uninterrupted hydraulic
CHAPTER 2—INVESTIGATION

147

Figure 2-38.—Initial steps to obtain a hand-cut, undisturbed block sample from (A) bottom of 

test pit or level surface, and from (B) cutbank or side of test pit.

thrust. The sample is held within the tube during removal

from the drill hole by a vacuum created by a locked piston,

which is an integral part of the sampler (USBR 7105). 

Reclamation uses several types of fixed-piston samplers to

recover samples of soft, saturated soils. With the Hvorslev,

Butters, and other inner rod piston samplers, the piston is

held stationary by a piston-rod extension connected to the

upper part of the drill rig mast while the sample tube is

pushed into the soil. These samplers require a drill rig with

a hollow-spindle. The Osterberg sampler has a piston that

is attached to the head of the sampler. Sample recovery is

accomplished by use of drill fluid pressure through the drill

rods to push the thinwall sample tube into the soil. A fluid

bypass system fabricated into the sampler stops penetration

of the sampler tube at 750 mm (30 in). Figure 2-41

illustrates the operating principle of the Osterberg sampler.

The Osterberg sampler is preferred for sampling in soils
EARTH MANUAL

148

Figure 2-39.—Final steps in obtaining a hand-cut, undisturbed block sample.

where inner rod deflection measurements are not required

since it is much faster to operate. The sample is recovered

from the borehole by removing all rods and the sampler

from the hole.

Thinwall push tube sampling is normally successful in

nonsensitive cohesive soils. The optimum clearance ratios

and drill mud consistencies described in USBR 7105 should

be used. Since cohesive soils are undrained during the

penetration process, high-quality samples can be obtained 

with smooth penetration rate. The cohesive nature of fines

normally causes sufficient friction between soil and tube to

retain the sample. Initial attempts to sample soft cohesive

soils should be made with the thinwall push tube.

Handheld penetrometer tests should be performed on soft

clays at the bottom of the tube to assist with selection of

laboratory test specimens. A guide for sampling methods

for materials difficult to recover can be found in reference

[39].
CHAPTER 2—INVESTIGATION

149

Figure 2-40.—Chain saw equipped with carbide-tipped 

blade being used to cut block sample.

Samples of soft cohesive soils should be shipped to the

laboratory and tested promptly. If stored for excessive

periods of time, changes in material structure can occur

because of oxidation and microbial processes. In the past,

many materials have been used to coat steel tubes, such as

lacquers and zinc magnesium oxides. If appreciable sand

content exists in the soil, these coatings can be scraped

away, and rust (iron oxides) forms on the thinwall tube.

Stainless steel tubes can be used, but they are more difficult

to cut open. The ends of thinwall soil samples are

inevitably exposed to air during trimming, and the oxidation

processes begins. Aging along with oxidation processes can

cause detrimental changes in peak strength and sensitivity of

soft clays.

b. Soft to Moderately Firm Cohesive Soils.&Soft to

moderately firm cohesive soils in surficial deposits can be

sampled in a relatively undisturbed condition using fairly

simple sampling methods. Sampling equipment for this type

of soil includes the thinwall push sampler and the hollowstem auger sampler. The following paragraphs discuss each

sampler and the necessary operational procedures to ensure

recovery of a high-quality representative soil sample. 

1. Thinwall Push Samplers.&Thinwall push

samplers were developed primarily for obtaining

undisturbed soil core samples of soft to moderately firm

cohesive soils and are described in detail in USBR 7105.

The sampler consists of a thinwall metal tube attached to a

sampler head containing a ball check valve. The principle

of operation is to push the sampler, without rotation, into

the soil at a controlled penetration rate and pressure. The

sample is held in the tube primarily by soil cohesion to the

inner tube walls and assisted by a partial vacuum created by

the ball check valve in the sampler head.

Reclamation commonly uses thinwall sampling equipment

designed to recover either 75- or 125-mm- (3- or 5-in-)

diameter soil cores. Size requirements depend primarily

upon intended use of the sample. For moisture density

determinations, a 75-mm- (3-in-) diameter sample will

suffice, but great care must be exercised, and proper

clearance ratios must be used to ensure that the sample does

not densify during sampling. Appropriate tube clearance

ratios and drill mud consistencies for thinwall sampling are

given in USBR 7105. Samples 125 mm in diameter are

preferred for laboratory testing because multiple specimens

can be trimmed from a single sample. Triaxial shear

equipment is available with end platens to accommodate

extrusion of 75-mm thinwall specimens directly from the

tube, especially for soils which are difficult to trim. 

The ends of the soil sample in thinwall tubes should be

trimmed to fresh soil. A moisture specimen should be taken

from the bottom end of the tube. Average tube density can

be measured according to USBR 7105. Expandable O-ring
EARTH MANUAL

150

Figure 2-41.—Thinwall fixed-piston sampler (Osterberg type).
CHAPTER 2—INVESTIGATION

151

packers should be used to confine the soil. Special care

should be taken to remove slough and cuttings by trimming

the top of the sample. 

2. Hollow-Stem Auger Samplers.&As described in

USBR 7105, three types of sampling operations are

available for recovering soft to moderately firm cohesive

soils with hollow-stem augers. In the first method, a

conventional sampler is lowered inside the hollow stem. In

the second and third methods, known as "continuous

sampler systems," a sampler barrel is specifically designed

to lock into the lead auger allowing sampling to progress

with advancement of augers. The continuous samplers are

widely used in the drilling industry and are capable of

sampling a wide variety of materials. Schematic drawing of

wire-line and rod type continuous sampling systems are

shown on figure 2-42.

The first type of sampling operation is accomplished by

drilling to the sampling depth with a hollow-stem auger

equipped with a center pilot bit. The pilot bit is attached to

drill rods positioned within the hollow-stem auger. At the

sampling depth, the drill rods and pilot bit are removed, and

a thinwall push sampler is lowered to the bottom of the hole.

After the sample is recovered, the pilot bit is replaced, and

augering is continued to the next sampling depth.

A second type of hollow-stem auger sampling operation

involves a wire-line latch system that locks the pilot bit and

soil sampler within the lead hollow-stem auger. After the

auger has been advanced to the sampling depth, an overshot

assembly is lowered by wire-line to unlock and latch onto

the pilot bit for removal from the hole. Then, a thinwall

sampler with a head bearing assembly is lowered by wireline and locked within the lead auger section. Sampling is

accomplished by continuing auger rotation and penetration,

which allows the center core material to enter the thinwall

sampler. The head bearing assembly on the sampler allows

the sample tube to remain stationary while the auger is

rotating. At the end of the sample run, the overshot is

lowered by wire-line to release the sampler lock mechanism,

latch onto the sampler, and remove it with the soil sample

from the hole.

The wire-line hollow-stem auger sampling system can be

used to successfully sample a wide variety of soils. Some

difficulties may be experienced with latching systems in

soils below the water table which heave into the hollow

stem. Wire-line line systems are economical due to rapid

continuous sampling capability. They are used extensively

for hazardous waste site characterization studies. Drill rod

systems discussed below are preferred for large-diameter

soil samples where detailed studies of engineering properties

are required. Inner barrels can be equipped with split liners

or Plexiglas liners. Sample diameters of up to 100 mm (4

in) are currently available in wire-line systems. Typical

sample lengths are 1.5 m (5 ft) but may be shortened if

sample disturbance is evident.

The third and most recently developed hollow-stem auger

sampling system (USBR 7105) involves using rods to lower,

hold, and hoist a continuous sampler unit designed to

recover samples during auger penetration. This system

positively eliminates rotation of the sampler as the auger

rotates. It is considered the best mechanical sampling

system available for recovery of undisturbed soil samples by

hollow-stem auger.

The stability of any sampling tool is critical to recovery of

representative undisturbed samples. With hollow-stem

augers, the inner barrel or sample tube that receives the soil

core must not rotate as soil enters the sampler. A sampler

with a head bearing assembly can rotate if cuttings are

allowed to accumulate in the annulus between the outer

rotating auger and the inner sample barrel. To eliminate

any chance of movement of the inner barrel, the continuous

sampler system is rigidly connected to rods that extend up

through the hollow-stem auger to a yoke located above the

rotating auger drillhead. Then, the outer auger is allowed

to rotate for drilling penetration, but the sampler within the

auger is held to prevent rotation as soil core enters the

sample tube. As with the wire-line systems, typical

sampling intervals are 1.5 m; but for large-diameter samples

for laboratory testing, this interval should be shortened to

reduce friction buildup in liners and/or the tendency to use

larger clearance ratios and overcut the sample. Samplers up

to 150 mm (6 in) in diameter are available with the drill rod

hollow-stem auger system. The large diameter capability

and positive antirotation of the inner rod system make this

the preferred method when detailed engineering properties

studies are required.

To recover a sample with the continuous sampler system, all

sampler connecting rods and the sampler are removed from

the auger to retrieve the soil core. This is followed by

lowering the sampling unit to the hole bottom for

continuation of sampling operations. 

Both continuous hollow-stem auger sampling systems have

adjustments for lead distance of the soil cutting shoe and

different clearance ratios for the shoe. As with the Denison

soil core barrel, the lead distance and clearance ratios must

be optimized for best sample recovery. In general, softer

soils require more lead distance of the cutting shoe below

auger flights. More cohesive soils require larger clearance

ratios to avoid buildup of friction inside liners. Both the
EARTH MANUAL

152

a b

Figure 2-42.—Overshot wire-line a) and rod type b) continuous sampling system. (Mobile Drill Co.)
CHAPTER 2—INVESTIGATION

153

wire-line and inner rod operated hollow-stem auger systems

will accept clear acrylic liners. Plastic liners should have

walls thick enough to confine the core without deflecting

[usually about 6 mm (1/4 in)]. Numerous measurements are

taken with micrometers to ensure that liner diameters

required for accepting samples are maintained. The plastic

liners can be cut flush with soil ends, and plastic caps or

expandable O-ring packers can be used to seal specimen

ends to preserve in-place moisture content. Use of plastic

liners permits sample inspection and adjustments for

clearance ratio and shoe lead distance.

Manufacturer supplied shoes are designed for successful

recovery of a wide variety of soils but may not provide

optimum sampling for advanced engineering properties

testing. For critical samples, shoes of varying lead distance

and clearance ratios can be readily machined by local

commercial machine shops. The most frequent problem is

the tendency to use too large a clearance ratio during

sampling. This can result in a large air gap inside the

sample liner and possible alteration of soil properties. The

goal is to provide a sample which fills the sample liner

without objectionable friction that results in compression

and densification of the soil. If an air gap exists, the

clearance ratio should be reduced. If excessive friction

develops in the liners, either decrease sample length or

increase clearance ratio.

c. Medium to Hard Soils and Shales.&Medium to

hard soils and shales located either above or below the water

table can usually be sampled in an undisturbed condition

using double-tube coring barrels. The three types of core

barrels commonly used are the Pitcher sampler, Denison

core barrel, and DCDMA series 100- by 140-mm and 150-

by 200-mm core barrels (4- × 5-1/2- and 6- × 7-3/4-in).

The DCDMA series barrels can also be converted to

perform diamond coring for rock sampling. The following

paragraphs discuss each sampler and the necessary

procedures to ensure recovery of high-quality representative

soil samples.

1. Pitcher Sampler.&The Pitcher sampler was

developed primarily for obtaining undisturbed soil core

samples from medium to hard soils and shales. Figure 2-43

illustrates the action of this sampler. The Pitcher sampler

has a unique feature in that it has a spring-loaded inner

barrel which lets the sample trimming shoe protrude or

retract with changes in soil firmness. In extremely firm

soils, the spring compresses until the cutting edge of the

inner barrel shoe is flush with the crest of the outer barrel

cutting teeth. In soft soils, the spring extends and the inner

barrel shoe protrudes below the outer barrel bit and prevents

damage to the sample by drilling fluid and drilling action.

Because spring action on the cutting shoe automatically

adjusts lead distance, the pitcher sampler is always preferred

for use in firm to stiff soils where layer stiffness will

change or where softer zones will be encountered. If soft

zones are encountered without spring loaded inner barrels,

the material will be washed out and contaminated with drill

fluid.

Although the Pitcher sampler is available in various sizes for

obtaining cores from 75 to 150 mm (3 to 6 in) in diameter,

Reclamation' s laboratory requirements normally dictate 150

mm (6 in), a 150- by 200-mm Pitcher sampler. This

sampler was designed to use 150-mm thinwall tubes as the

inner barrel. Normally, the soil core is contained within the

thinwall tube, and a new tube is placed within the sampler

for each sampling run. However, Reclamation changed the

inner-barrel configuration to one that accommodates sheet

metal liners for the soil core, rather than thinwall tubes.

Aluminum irrigation pipe was found to have acceptably

small-diameter variation for high-quality sampling. The

modified inner barrel is threaded for attachment of a

trimming shoe with a milled recess to contain the sheet

metal liner. Sheet metal liners are preferred for samples for

laboratory testing because they are easier to open for

examination, and core is more easily removed without

damage.

2. Denison Sampler.&The Denison sampler, shown

in figure 2-44, was developed to obtain large-diameter

undisturbed cores of cohesive soils and shales of medium to

hard consistency. Disadvantages of the Denison sampling

barrel are having to manually adjust the position relationship

between the outer barrel cutting bit and the inner barrel

trimming shoe according to the consistency of the soil to be

sampled. The required setting must be determined by the

operator before each sampling run. The setting is achieved

by interchanging varied lengths of outer barrel cutting bits

to conform with the type and consistency of soil being

sampled. The proper cutting bit for various soil

consistencies is selected as described below and as

illustrated in figure 2-45. 

 ̆ Soft soil samples can be obtained with a short cutting

bit attached to the outer barrel so the inner barrel

trimming shoe protrudes about 75 mm (3 in) beyond

the bit. The shoe acts as a stationary push sampler,

trims and slides over the sample, and protects the

core from drill-fluid erosion or contamination.

 ̆ Firm soil samples can be obtained by attaching a

cutting bit having a length that will position the

crown of the bit teeth approximately flush with the

inner-barrel shoe trimming edge. With this setting,
154

Figure 2-43.—Pitcher sampler. (Pitcher Drilling Co.)
CHAPTER 2—INVESTIGATION

155

Figure 2-44.—Denison sampler and core barrel.
EARTH MANUAL

156

Figure 2-45.—Relationship of inner-barrel protrusion using different-length, Denison-sampler

cutting bits for drilling.

the bit teeth cut the core simultaneously with the

trimming of the core by the shoe. The shoe provides

some protection to the sample from the drill fluid

because most of the fluid circulates between teeth

openings rather than through the crown area.

 ̆ Hard soil samples are obtained by attaching a cutting

bit having a length that will position the teeth about

25 to 50 mm (1 to 2 in) below the trimming shoe.

This setting is intended only for nonerodible soils

because the entire circumference of the sample is

subjected to drill fluid circulation before it is

contained within the trimming shoe.

3. Large-Diameter Hi-Recovery Core

Barrels.&Increased demand for large-diameter soil samples

for laboratory testing became obvious to manufacturers of

conventional rock coring equipment in the late 1960s. To

provide alternatives to soil-sampling core barrels

(e.g., Denison and Pitcher core barrels), the DCDMA

developed standards for a large-diameter core barrel with

versatility to sample both soil and rock. These core barrels

use a variety of interchangeable parts to convert the basic

rock core barrel to core medium to hard soils and shales,

fragmented rock, rock with soil lenses, and homogeneous

rock. Some of the interchangeable parts and their functions

are:

 ̆ A clay bit, with face extension, to trim and advance

over softer clay soils and to protect the core from

drill-fluid erosion.

 ̆ A spring-loaded inner barrel to protrude in front of

the core barrel for soft soils and to retract into the

core barrel for harder soils.

 ̆ A split inner barrel for coring shales, soft rock,

fragmented rock, and lensed rock.

 ̆ A single-tube inner barrel for coring homogeneous

hard rock.

Reclamation has used successfully both the 120- by 140-mm

core barrel and 150- by 200-mm barrel core (4- by 5-1/2-

and 6- by 7-3/4-in), depending upon core size requirements.

A metal liner should be inserted inside the inner barrel to

contain and seal the core sample for shipment to the

laboratory.

d. Unsaturated Water Sensitive Soils.&Dry drilling

techniques are preferred for sampling water sensitive

unsaturated soils. Water sensitive soils include windblown

loess deposits and slopewash that can collapse when exposed

to water. These soils are characterized by low density inplace conditions. Continuous hollow-stem auger samplers

are preferred for sampling these deposits because exposure

to drilling fluids is not permitted. If surface exposures are

accessible, block samples provide the highest quality

sample. Sampling studies in loess have shown that thinwall

tubes and Pitcher sampling result in unacceptable sampling
CHAPTER 2—INVESTIGATION

157

disturbance [40]. Thinwall samplers compacted loess&

when dry methods were used to advance the borehole.

Pitcher sampling allowed for some exposure to fluid if not

properly operated. 

2-18. Casing Advancer.&Manufacturers have

adapted wire-line drilling principles to accommodate a wide

variety of sampling methods. The wire-line casing advancer

can be used to advance standard BW, HW, and HW, casing

through difficult deposits such as coarse alluvium or highly

fractured materials while still protecting the drillhole.

Casing advancers have a center pilot bit which is normally

configured as a tricone rockbit. In one case, where it was

necessary to drill through several steel settlement plates, a

pilot bit made with diamonds was used. Casing bits are

normally diamonds, but carbide insert drag bits have been

used in soils. After the casing is advanced to depth for

testing or sampling, the center pilot bit can be removed by

wireline, and a flush casing is left. The casing advancer has

proved effective for the following operations:

 ̆ Conventional or wire-line coring through casing

 ̆ Casing through landslide or alluvial materials

 ̆ Conventional or wire-line thinwall tube sampling

through casing

 ̆ Penetration resistance testing and sampling ahead of

casing

 ̆ Tie back anchor installation through casing

 ̆ Installation of well screen, perforated drain, or

piezometers through casing

The casing advancer has been used to successfully perform

penetration resistance tests in loose sands below the water

table. Drilling was performed with carbide casing bit and

no pilot bit. The primary reason for success was that a fluid

column was maintained in the casing that prevented heaving

sands from entering, and careful attention was paid to

circulation to avoid hydraulic fracturing. 

2-19. Rock Sampling Methods.&Core barrels are

available to obtain cores from 20 to 150 mm (3/4 to 6 in) in

diameter. There are two principal types of core barrels:

(1) single tube and (2) double tube. The DCDMA has

standardized dimensions for four series of conventional rock

core barrels. The series are denoted as WG, WT, WM,

and Large Diameter [32]. The W series barrels can be

obtained for nominal hole sizes R through H. The

differences between these designs are primarily related to

methods of fluid circulation and optimizing core diameters.

For example, the G series of tubes is the most basic in

design and allow for more core exposure to drill fluid. The

T series barrels have thinner tube walls, which result in

larger core. The G and T series are available in single tube

or double-tube configurations. In the M series barrel, the

inner tube is threaded to receive the lifter with resulting less

exposure of core to drill fluid. The large-diameter core

barrels have better control of drill fluid circulation and core

protection. The M and Large Diameter series barrels have

double-tube design. As one progresses through G, T, M,

and Large Diameter, the ability to retrieve difficult cores

increases. Double-tube core barrels can be either rigid or

swivel design. Reclamation uses either M or Large

Diameter double-tube core barrels for the majority of rock

coring operations with conventional barrels. Figure 2-46

shows a schematic view of typical M and Large Diameter

double-tube swivel core barrels with a split liner

recommended for most investigations. When DCDMA,

standard drawings are compared to drill manufacturers

literature, it is difficult to distinguish which DCDMA core

barrel series is available. Most manufacturers offer

conventional barrels equivalent to the M series. 

Normally, R, E, A, and B hole size cores normally apply

only to instrumentation or stabilization applications such as

overcoring studies or rock bolt installations. For

investigation purposes, Reclamation specifies a minimum

hole size of N for conventional core barrels.

The single-tube core barrel is a basic design and consists of

a core barrel head, a core barrel, and an attached coring bit

that cuts an annular groove to permit passage of drilling

fluid pumped through the drill rod. This design exposes the

core to drilling fluid over its entire length and can result in

serious core erosion of unconsolidated or weakly cemented

materials. The single-tube core barrel is no longer used

except in unique situations, such as in concrete sampling or

when using "packsack-type" drills. Single-tube core barrels

or masonry core barrels are frequently used for coring soil

cement dam facings for construction control. Single-tube

core barrels are not recommended for coring operations in

concrete dams [41].

The rigid-type, double-tube core barrel provides an inner

barrel which rotates with the outer barrel but protects the

core from drilling fluid. The rigid-type, double-tube core

barrel has been used successfully in soft to medium-hard

formations and in hard, broken formations. A problem

arises in core abrasion caused by the rotating inner tube, and

soft, easily disturbed material cannot be cored well with the

barrel. The rigid design is not recommended for coring

when laboratory tests are required or where good recovery

is required.
EARTH MANUAL

158

Figure 2-46.—Double-tube swivel-type core barrels. (Bureau of Mines [39])

The swivel-type, double-tube core barrel sampler consists of

an outer rotating barrel and an inner stationary barrel that

protects the core from drilling fluid and reduces torsional

forces transmitted to the core. The swivel-type, double-tube

barrel is used to sample most rock; it may be used to obtain

cores in hard, brittle, or poorly cemented materials such as

shale and siltstone or cores of soft partially consolidated or

weakly cemented soils.

Most double-tube core barrel inner tubes may be replaced

with a split inner tube. Use of a split inner tube is required

in Reclamation investigations unless special conditions exist

which warrant deviation from this requirement. Advantages

to split inner tubes are:

 ̆ The undisturbed core allows detailed visual analysis.

 ̆ The core is easily transferred into the core box

without sample disturbance.

 ̆ The core can be easily wrapped in plastic to preserve

moisture content before it is placed in the box.

 ̆ Expansive or sticky formations can be easily

removed. 

A few of the double-tube core barrels have been modified to

allow a split liner to be inserted inside a solid inner tube to

accept the core sample. Barrels modified in this fashion are

sometimes referred to as "triple-tube" core barrels. A tripletube configuration is desirable in formations that may be

detrimentally affected by drill fluid which could penetrate a

single-split inner tube.

The Large Diameter core barrels can be adapted for a wide

variety of sampling purposes. Three sizes commonly

available are described by core and barrel outer diameter (in

inches) as follows: 2.75 by 3.87, 4 by 5.5, and 6 by 7.75.

The large-diameter series is available also with split inner

tube or triple-tube configuration. The larger barrels can

even be adapted for sampling soils by converting bits and

liners into configurations similar to Denison or Pitcher

samplers. These core samplers also have been designed with

a spring-loaded retractable inner barrel, which enables the

same type of core barrel to be used for coring either soil or

rock. The retractable inner barrel and soil-coring bits are

replaced with a standard inner barrel and diamond bits for

rock coring. They can be equipped with split liners. These

barrels are highly recommended in deposits which are
CHAPTER 2—INVESTIGATION

159

difficult to sample. Samples of soils have been successfully

obtained with this type of barrel. In cases where soil

samples are retrieved, soil core should be waxed to preserve

in-place moisture content.

A wide variety of wire-line core barrel systems are available

for rock coring. By design, the wire-line core barrel is

essentially a swivel type double-tube or triple-tube system.

Most coring operations now use a split inner liner inside of

a solid inner tube. The triple-tube system is highly

recommended over a single-split inner tube system to

prevent core loss if the single-split tube springs open. Some

of the triple-tube systems with split inner liners are equipped

with hydraulic core extraction pistons to remove the split

liner from the solid inner tube. The AQ, BQ, NQ, HQ,

and PQ wire-line core barrels are available in core

diameters of about 27, 33, 44, 60, and 83 mm (1.1, 1.3,

1.75, 2.4, and 3.25 in). The actual core sizes vary slight

among manufacturers. NQ size is considered a

minimum&primarily, because rapid water testing is

routinely performed on many investigations using wire-line

downhole packers. The wire-line packer system is shown

on figure 2-47. Water tests are performed using this system

according to USBR 7310. If the objective of the program

is good core for testing, Reclamation normally uses HQ size

wire-line equipment, and water testing can be performed on

these holes also. PQ size equipment is useful for obtaining

better recovery in softer matrices such as soil-cementbentonite cutoff wall backfill materials. Materials with

compressive strengths as low as 1400 Kpa (200 lb/in2

) have

be successfully recovered with PQ size equipment.

Compressive strengths lower than this present significant

problems with good core recovery, and other testing

methods such as in-place tests must be considered to

characterize these materials.

Many guides are available for selecting conventional and

wire-line core barrel bits including from the manufacturers

themselves. Key parameters in bit selection include the

abrasiveness of the cuttings and the matrix of the material.

For softer materials, diamond bits can be replaced with

hardened metal, polycrystalline, or carbide drill bits, and

shorter core runs [1.5 m (5 ft) or one-half that in length] are

used to minimize disturbance. Metal bits are an attractive

alternative for sampling softer materials, but diamonds are

a must for coring harder rock. Another important

parameter is the location of fluid discharge. Core barrel bits

can either be internal or face discharge with face discharge

recommended for easily erodible matrix. Excellent

references for bit selection are available [32, 39, 42].

Accuracy and dependability of data from rock core drilling

depend largely on the size of core in relation to the kind of

material drilled, the percentage of core recovered, behavior

during drilling, and experience of the drill crew. Since rock

that cores well in an NX size hole may break up badly in an

EX size hole, it is important to use the largest practical

diameter hole and core barrel. Recovery of core is more

important than making rapid progress when drilling a hole.

Portions of core that are lost probably represent shattered or

soft, incompetent rock, whereas recovered portions represent

the best rock from which an overly optimistic evaluation of

the foundation likely will be made. Nevertheless, a

reasonably high percentage of core recovery provides a more

continuous section of the materials passed through. Cores

provide information on the character and composition of

different materials, with data on spacing and tightness of

joints, seams, fissures, and other structural details. When

drilling in soft materials, drill fluid circulation must be

reduced or stopped entirely, and the core recovered "dry,"

even though significant delay in operations may occur.

Many of the principles of conventional coring can apply to

wire-line coring. The core barrel is fitted with a coring bit

and is lowered into the hole with the hollow drill rod.

Circulation of drilling fluid should begin before the core

barrel reaches the bottom of the hole to lift cuttings or

sludge and prevent them from entering the core barrel at the

start of coring. The optimal rotational speed of drilling

varies with type of bit used, diameter of core barrel, and

kind of material to be cored. Excessive rotational speed

results in chattering and rapid bit wear and will break the

core. Low rotational speed results in less wear and tear on

the bit and better cores, but lower rates of progress. It is

critical to minimize vibration from uneven rods or poor

drive head assembly. Vibration of the drill stem will cause

vibrating and chattering, resulting in bit blockage, broken

core, and poor core recovery. If rotation rates must be

decreased because of vibration, the mass or pressure on the

bit must also be decreased, or polishing and dulling of the

diamonds will occur.

Rotational speed must also be adjusted for core barrel

diameter. Drillers must evaluate all factors when

considering coring rates and pressures. Bit wear can provide

many clues when selecting proper rotational rates once the

appropriate bit is specified for the material. If wire-line

coring is performed, bit inspection will cause trip time delay.

The rate at which the coring bit advances depends on

firmness of material, amount of pressure applied on the bit,

and rotational speed. Pressure must be carefully adjusted by

the driller; excessive pressure causes the bit to plug and may

shear the core from its base. Bit pressure is controlled by 
160

Figure 2-47.—Wire-line packer system. (Longyear Co.)
CHAPTER 2—INVESTIGATION

161

a hydraulic or screw feed on the drilling machine. The

weight of the column of drill rod is seldom in excess of the

optimum bit pressure for coring medium and hard rock;

frequently, additional downward pressure is applied. If

coring is performed in abrasive, friable, or fractured rock,

the rotational speed and downfeed pressure must be

reduced. If the coring bit penetrates these materials too fast,

pieces of uncut rock result and cause core blockage and

poor recovery. After the core run is completed, the drill

rods are pulled up without rotation which causes the core

lifter to slide down a beveled shoe and increasingly grip the

rock until breakage occurs. Generally, breakage can be

heard as a snapping sound, and it will always occur below

the lifter. 

If the drill hole in rock is clean, and seams and fissures are

not sealed off by drill action, percolation tests can be

performed to test the permeability of various strata. Gravity

or pressure tests are made as described in USBR 7310.

Large drilling fluid losses or water inflows into drill holes

during drilling indicate either the presence of large openings

in the rock or the existence of underground flow.

Completed holes should be protected with lockable caps to

preserve them for use in ground-water level observations, as

grout holes, or for reentry, if later it is necessary to deepen

the hole. Usually, casing is required for those sections of

hole in loose material or unconsolidated subsurface soils.

As rock cores are removed from core barrels, they are

placed in core boxes and logged. Guidelines for logging,

core box construction, and core box arrangements are given

in the Engineering Geology Field Manual [20]. Core can be

placed by hand into core boxes, and use of cardboard or

plastic half-rounds is encouraged. Long pieces of core may

be broken to fit into the core box but should be marked as

a mechanical break. If the core contains weak materials or

materials for laboratory testing, the core should be

completely wrapped in layers of plastic wrap, aluminum

foil, and wax. Wrapping can be performed on core in the

half-round as shown on figure 2-48, except that the

complete core is wrapped.

Figure 2-49 shows a standard core box and illustrates the

method of placing cores in the box to ensure proper

identification of each core sample.

2-20. Geophysical Exploration

Methods.&Geophysical methods of subsurface exploration

are an indirect means of gathering data pertaining to

underground conditions. Using geophysical techniques

involves taking measurements at the earth' s surface or in

boreholes to determine subsurface conditions. Geophysical

methods may be employed during any stage of an

investigation and include:

 ̆ seismic,

 ̆ electrical,

 ̆ magnetic, and

 ̆ gravity.

Geophysical methods can be a useful and economic addition

when used in conjunction with a test-boring investigation

program. In contrast to borings, geophysical surveys are

used to explore large areas rapidly and economically. They

indicate average conditions along an alignment or in an area,

rather than along the restricted vertical line at a single

location as in a boring. Geophysical data can be used to

help determine the best location of future drill holes as well

as provide information to extrapolate foundation conditions

between existing drill holes. These data are useful for

detecting irregularities in bedrock surface and at interfaces

between strata. The cost of performing geophysical surveys

is often less than the cost of drilling; therefore, judicious use

of both geophysical methods and drilling can produce the

desired information at an overall lesser cost. Although

geophysical field work is relatively inexpensive,

interpretation of results is difficult and specialized. For test

results to be usable and reliable, correlations must

necessarily be made locally with exploration data from

borings.

Geophysical methods are best suited to prospecting sites for

dams, reservoirs, tunnels, highways, canals, and other

structures. Also, they have been used to locate gravel

deposits and sources of other construction materials whose

properties differ significantly from adjacent soils.

Downhole, uphole, and cross-hole seismic surveys are used

extensively to determine dynamic properties of soil and rock

at small strains.

All geophysical techniques are based on detection of

differences between properties of geologic materials. If

such differences do not exist, geophysical methods will not

be useful. These differences range from acoustic velocities

to contrasts in electric properties of materials. Seismic

methods, both reflection and refraction, depend on the

difference in compressional or shear-wave velocities through

different materials. Electrical methods depend on contrasts

in electrical resistivities. Differences in density of different

materials permit gravity surveys to be used in certain types

of investigations, and contrasts in magnetic susceptibility of

materials allow magnetic surveying to be used. Differences

in magnitude of naturally existing electric current within the

earth can be detected by self-potential surveys.
EARTH MANUAL

162

Figure 2-48.—Use of a cardboard PVC half-round and 

plastic wrap to prevent disturbance and drying out of 

shear zone, special samples, or fracture zones.

Based upon detection and measurement of these differences,

geophysical surveys can often be designed to gather useful

data to assist engineers and geologists in performing a more

complete geotechnical investigation for civil engineering

structures. Geophysical methods constitute only another

exploratory tool to geological investigations, and they must

never be regarded as anything more than tools. These

methods will not disclose more than a good set of boreholes

and drill holes&and usually not as much&and they should

not be used without specific and constant correlation with

geologic information. A preliminary geologic investigation

is essential before geophysical methods can be applied, since

they require knowledge of certain general conditions of local

geology. The most favorable condition occurs when high

contrasts between geophysical properties exist, such as when
CHAPTER 2—INVESTIGATION

163

Figure 2-49.—Arrangement of cores in a core box to ensure proper

identification of samples.

rock underlies a shallow surficial deposit and the physical

characteristics of the two are markedly different. Each type

of geophysical survey has its capabilities and its limitations.

Geophysical methods are now frequently used for

preliminary investigations at potential damsites and at

proposed locations of other types of water resources

structures. The most extensive use of geophysical methods

in the practice of civil engineering has been in the United

States where the larger federal engineering organizations

have used these methods regularly in preliminary

exploration work. All the methods are subject to definite

geological restrictions; rocks of essentially different physical

character must be in contact, and the strata encountered

must be fairly uniform with respect to their physical

character. Low-density strata overlain by high density strata

cannot be detected by any of the surface geophysical

methods, although they can be detected by some of the

borehole methods. Finally, all information obtained as a

result of geophysical investigations must be studied and used

only when properly correlated by a specialist with the

maximum information available regarding local geologic

conditions. Despite these qualifications and necessary

restrictions, geophysical methods are a powerful and useful

tool.

The use of geophysics has increased when characterizing

hazardous waste sites. Large areas can be tested to reduce

the number of conventional borings and monitoring wells.

Six methods are commonly used for ground-water

contamination studies:

 ̆ resistivity,

 ̆ electromagnetic,

 ̆ refraction and reflection,

 ̆ magnetic,

 ̆ ground-penetrating radar,

 ̆ borehole geophysics [43].

In many cases, water of differing chemistry or the presence

of buried objects, such as tanks or drums, makes

geophysical methods especially effective. For example,

gravity surveys, which are not especially useful in civil

engineering applications, may be useful at a site that

contains buried storage tanks of unknown location. Expert

systems have been developed to provide data on which

forms of geophysics may be effective at a contamination site

[44].
EARTH MANUAL

164

A list of geophysical methods commonly used follows.

These methods for performing geophysical testing are

discussed in more detail in the Engineering Geology Field

Manual [20].

Surface Geophysical and Other Techniques

1. Seismic Refraction

2. Seismic Reflection

3. Shear-Wave Surveys

4. Surface Wave Surveys

5. Vibration Surveys

6. Electrical-Resistivity 

Profiling

Soundings

Dipole-dipole

7. Electromagnetic Conductivity 

Profiling

Soundings

8. Ground Probing Radar

9. Self-Potential Surveys

10. Magnetic Surveys

11. Gravity Surveys

Borehole Geophysical and Other Techniques

1. Electrical Logging

Spontaneous potential

Single-point resistivity

Multiple electrode arrays

Micrologging

Induction logging

Borehole fluid resistivity

2. Nuclear Radiation Logging

Gamma ray

Gamma-gamma logging

Neutron logging

3. Acoustic/Seismic 

Acoustic velocity

Acoustic borehole logging

Crosshole seismic

Tomography

4. Optical Borehole Logging

Television camera

Film camera

5. Borehole Caliper Logger

6. Borehole Fluid Temperature Logger

7. Borehole Gravity Logger

Tables 2-6 and 2-7 show application and limitations for use

of some of these techniques. Table 2-6 shows surface

methods, and table 2-7 shows borehole logging methods.

Correlations have been made between rock rippability and

seismic wave velocity. Figure 2-50 shows an example of

such correlations for heavy duty ripper performance (ripper

mounted on tracked bulldozer). Charts similar to that

shown in figure 2-50 are available from various equipment

manufacturers but must be used with extreme caution.

Each of the geophysical tests listed above is discussed in

greater detail in either the Design of Small Dams [16] or the

Engineering Geology Field Manual [20]. Two more

references containing excellent discussions on geophysical

methods are Hunt [45] and Legget and Karrow [46].

2-21. Field Testing Methods.&

a. General.&Quantitative data can be obtained during

standard penetration testing, and several other field tests can

be used to obtain information concerning in-place subsurface

conditions when exploring foundations. These include:

 ̆ permeability tests,

 ̆ in-place density tests,

 ̆ penetration tests,

 ̆ in situ strength and modulus tests,

 ̆ hand tests.

b. Field Permeability Tests.&Approximate values of

permeability of individual strata penetrated by borings can

be obtained by making water tests in boreholes. Reliability

of values obtained depends on homogeneity of the stratum

tested and on certain constraints of mathematical formulas

used. However, if reasonable care is exercised in adhering

to recommended procedures, useful results can be obtained

during ordinary boring operations. Open end tests and

packer tests in boreholes are described in USBR 7310,

although open end tests are often of lower reliability. A

well permeameter test used for estimating canal seepage

losses is described in USBR 7300. Using the more precise

methods of determining permeability by pumping from wells

with a series of observation holes to measure drawdown of

the water table (aquifer testing), or by pumping-in tests

using large-diameter perforated casing, requires special

techniques. Detailed information on field permeability

testing methods can be found in the Groundwater Manual

[47].

c. In-Place Density Tests.&The sand replacement

method is used to determine in-place density in a

foundation, a borrow area, or a compacted embankment by
CHAPTER 2—INVESTIGATION

165

Table 2-6.—Tools and methods for subsurface investigations

Method Principle and application Limitations

Surface seismic refraction Determine bedrock depths and characteristic

wave velocities as measured by geophones

spaced at intervals.

May be unreliable unless velocities increase

with depth and bedrock surface is regular. 

Data are indirect and represent averages. 

Limited to depths of about 30 m (100 ft).

High resolution reflection Determine depths, geometry, and faulting in

deep rock strata. Good for depths of a few

thousand meters. Useful for mapping offsets

in bedrock. Useful for locating ground water.

Reflected impulses are weak and easily

obscured by the direct surface and shallow

refraction impulses. Does not provide

compression velocities. Computation of

depths to stratum changes requires velocity

data obtained by other means.

Vibration Travel time of transverse or shear waves

generated by a mechanical vibrator is

recorded by seismic detectors. Useful for

determining dynamic modulus of subgrade

reaction for design of foundations of vibrating

structures.

Velocity of wave travel and natural period of

vibration gives some indication of soil type. 

Data are indirect. Usefulness is limited to

relatively shallow foundations.

Uphole, downhole, and

cross-hole surveys

(seismic direct method)

Obtain velocities for particular strata; dynamic

properties and rock-mass quality. Energy

source in borehole or at surface; geophones

on surface or in borehole.

Unreliable for irregular strata or soft soils with

large gravel content. Cross-hole

measurements best suited for in-place

modulus determination.

Electrical resistivity

surveys

Locate fresh/salt water boundaries; clean

granular and clay strata; rock depth; depth to

ground water. Based on difference in

electrical resistivity of strata.

Difficult to interpret and subject to wide

variations. Difficult to interpret strata below

water table. Does not provide engineering

properties. Used up to depths of about 30 m

(100 ft).

Electromagnetic

conductivity surveys

Measures low frequency magnetic fields

induced into the earth. Used for mineral

exploration; locating near surface pipes,

cables, and drums and contaminant plumes.

Fixed coil spacings limited to shallow depth. 

Background noise from natural and

constructed sources (manufactured) affects

values obtained.

Magnetic measurements Mineral prospecting and locating large igneous

masses. Highly sensitive proton

magnetometer measures Earth’s magnetic

field at closely spaced intervals along a

traverse.

Difficult to interpret quantitatively, but indicates

the outline of faults, bedrock, buried utilities, or

metallic objects in landfills.

Gravity measurements Detect major subsurface structures, faults,

domes, intrusions, cavities. Based on

differences in density of subsurface materials.

Not suitable for shallow depth determination

but useful in regional studies. Some

application in locating caverns in limestone.

Ground-penetrating radar Locate pipe or other buried objects, bedrock,

boulders, near surface cavities, extent of

piping caused by sink hole and leakage in

dams. Useful for high-resolution mapping of

near-surface geology.

Does not provide depths or engineering

properties. Shallow penetration. Silts, clays,

and salts, saline water, the water table, or

other conductive materials severely restrict

penetration of radar pulses.
EARTH MANUAL

166

Table 2-7.—Geophysical methods and techniques for logging boreholes

Method Principle and application Limitations

Electrical logging Several different methods available. Provides

continuous record of resistivity from which

material types can be deduced when

correlated with test-boring data.

Provides qualitative information. Best used

with test-boring information. Limited to

uncased hole.

Neutron radiation logging Provides continuous measure of natural

moisture content. Can be used with density

probe to locate failure zones or water bearing

zones in slopes.

Data from neutron probe is limited to in-place

moisture content values. Often differs from

oven-dried moisture content and requires

correction.

Gamma-gamma logging Provides continuous measure of in-place

density of materials.

Data limited to density measurements. Wet

density usually more accurate than dry

density.

Scintillometer (Gamma ray

logging)

Provides measure of gamma rays. Used to

locate shale and clay beds and in mineral

prospecting.

Qualitative assessments of shale or clay

formations.

Acoustic borehole imaging Sonic energy generated and propagated in

fluid such as air to water. Provides continuous

360( image of borehole wall showing fractures

and other discontinuities. Can be used to

determine dip.

Must be used in fluid-filled borehole unless

casing is being inspected. Tool must be

centered in the borehole. Logging speed is

relatively low between 20 and 75 mm/s (4 and

15 ft/min). Images less clear than those

obtained with borehole cameras.

Acoustic velocity logging Can determine lithologic contacts, geologic

structure, cavities, and attitude of

discontinuities. Elastic properties of rock can

be calculated. Compression (P-water) is

generated and measured. Used almost

exclusively in rock.

Borehole must be fluid filled and diameter

accurately known. Penetration beyond

borehole wall of about a meter or so. 

Geologic materials must have P-water

velocities higher than velocity of the borehole

fluid.

Crosshole seismic tests Seismic source in one borehole; receiver(s) at

same depth in second (or more) borehole(s). 

Material properties can be determined from

generated and measured compression and

shear waves. Low velocity zones underlying

high velocity zones can be detected.

Borehole spacing is critical and should be

>3 m and <15 m. Precise borehole spacing

must be accurately known for data to be

useful.

Borehole cameras Borehole TV or film type cameras available. 

TV viewed in real time. Can examine cavities,

discontinuities, joints, faults, water well

screens, concrete-rock contacts, grouting

effectiveness, and many other situations.

Requires open hole. Images are affected by

water clarity. Aperture on film camera must

be preset to match reflectivity of borehole wall

materials.

Borehole caliper logging Used to continuously measure and record

borehole diameter. Identify zones of borehole

enlargement. Can evaluate borehole for

positioning packers for other tests. One to six

arm probe designs.

Diameter ranges from about 50 to 900 mm (2

to 36 in). Must calibrate caliper against known

minimum and maximum diameter before

logging. Special purpose acoustic caliper

designed for large or cavernous holes (dia.) 

1.8 to 30 m (6 to 100 ft).

Temperature logging Continuous measure of borehole fluid

temperature after fluid has stabilized. Can

determine temperature gradient with depth.

Probe must be calibrated against a fluid of

known temperature. Open boreholes take

longer to stabilize than cased holes. Logging

speed 15 to 20 mm/s (3 to 4 ft/min).
CHAPTER 2—INVESTIGATION

167

Figure 2-50.—Rock rippability as related to seismic P-wave velocities. (Caterpillar Tractor Co.)

excavating a hole from a horizontal surface, determining the

mass of material excavated, and determining the volume of

the hole by filling it with calibrated sand. Water content of

soil excavated from the hole is determined, and in-place dry

density is calculated. In-place density data are often used in

calculations to determine shrinkage or swell factors between

borrow area excavation and compacted embankment

volumes. In-place density tests can be performed in shallow

foundations to evaluate bearing capacity for small structures.

Various devices using replacement methods (i.e., water,

balloons and water, oil) have been used to measure the

volume of the test hole. Indirect methods such as the

nuclear moisture and density gauge (USBR 7230) are also

used to determine in-place density, but the sand replacement

method is most common. USBR 7205 and 7220 describe

sand density methods to be used depending upon gradation

of material being tested and consequent size of the required

excavation. If the soil to be tested contains appreciable

coarse gravel and cobbles, in-place density is normally

determined by use of test pits with water replacement

(USBR 7221). These large scale tests are expensive;

normally, they only are performed when exploring critical

coarse grained borrow materials and for construction control

of rockfills and coarse shells of dams.

The determination of in-place dry density and water content

of a fairly deep foundation is often necessary. In this case,

the sand density method requires excavating a deep test pit

or test trench to gain access to the soils to be tested.

Excavation of deep test pits or accessible shafts can be
EARTH MANUAL

168

hampered by the presence of ground water, and special

safety precautions are required. Most deep test shafts are

reserved for critical explorations of coarse and cohesionless

soils. Mechanical drilling and sampling methods have

mostly replaced deep test shafts. Mechanical drilling and

sampling, if performed correctly, can provide reliable

information on in-place moisture and density of deep

foundation soils. Detailed procedures are given in

USBR 7105 for determining density of undisturbed tube

samples. These data can be reliably obtained in the field

and are extremely useful for design purposes. If mechanical

drilling and sampling is performed, it is strongly

recommended that average tube density be determined.

d. Penetration Testing.&

1. General.&Data obtained from quasi-static or

dynamic penetration tests can be used to estimate

engineering properties of soils and to delineate subsurface

stratigraphy. The most common tests employed are

standard penetration and cone penetration tests [SPT and

CPT tests (USBR 7015, 7020 and 7021)]. By evaluating

resistance to penetration during the tests, engineering

properties of compressibility and shear strength can be

estimated. Also, test results can be compared and correlated

to properties obtained from laboratory tests on undisturbed

soil specimens. In many cases the number of undisturbed

sampling holes may be reduced in favor of less expensive

penetration tests to better interpret complex site stratigraphy.

2. Penetration Resistance and Sampling of

Soils.&The SPT test consists of determining the number of

blows N, of a 64 kg (140 lbm) hammer dropping 762 mm

(30 in), required to produce 300 mm (1 ft) of penetration of

a standard 50-mm (2-in) o.d. sampler into soil at the bottom

of a prebored drill hole after the sampler is seated an initial

150 mm (6 in) (fig. 2-51). The N value can be used to

estimate strength and compressibility of sands, consistency

of clays, and bearing capacities. A disturbed sample is

retrieved in the 35-mm (1-3/8-in) i.d. sampler barrel which

allows for inspection, visual classification, and moisture

content determination (fig. 2-52). Reclamation specifies a

barrel with constant inside diameter of 35 mm (1-3/8 in),

but most SPT barrels manufactured in the United States

today are upset walled to 38-mm (1-1/2-in) diameter to

accommodate liners. The difference in SPT N value can

vary 10 to 30 percent between different barrels [48]. If

critical studies are performed, the inside diameter of the

barrel must be known so corrections can be made.

Laboratory soil classification tests (USBR 5000) also can be

performed on the soil sample. Normally, penetration tests

are performed at 1.5 m (5 ft) intervals or with changes in

soil strata. For critical investigations, such as foundations

for dams, testing may be performed more frequently, but

normally the minimum testing interval is 0.75 m (2.5 ft) to

prevent disturbance of soil to be tested in the next interval.

The penetration resistance test is widely used to evaluate

foundation conditions for investigations requiring drill holes.

Penetration resistance obtained during field testing is

inversely proportional to the energy delivered to the sampler

system by the driving system. Research has shown that the

wide variety of equipment available and in use in the United

States results in large variations in energy delivery and

consequently in N (blow count) values [48]. In USBR 7015,

procedures require the use of safety hammers with the rope

and cathead method. The drill rod energy delivered by

safety hammers ranges from 60 to 70 percent of free fall

hammer energy and is now considered the standard target

range for SPT in the United States. Energy delivered by

automatic and manual trip hammer systems is more

reproducible, and possibly higher, because the influence of

rope condition, method of rope release from the cathead,

and friction in the mast sheave are all bypassed. Drill rod

energy transmission ranges from 90 to 95 percent for those

automatic trip hammers for which energy measurements

have been made. Using automatic hammer systems

enhances test reproducibility. These hammer systems can,

however, only be approved for use after energy delivery and

transmission characteristics are known. On critical

programs, such as liquefaction studies, adjustment for

higher energy of automatic hammers may be required [48].

Numerous studies have been performed that indicate the

impossibility of obtaining a truly undisturbed sample of

clean loose sand using thin wall tube and thin wall piston

samplers [49]. Volume changes can occur in the clean

sands during pushing because of the pervious nature of the

material. As a result, there is increased reliance on

empirical correlations to estimate engineering properties of

sands. Figure 1-15 in chapter 1 shows results of

Reclamation' s research for estimating the relative density of

medium to fine sands in relation to SPT blowcounts.

Studies performed by the Corps of Engineers produced

additional data on the factors affecting penetration resistance

in sands. The Reclamation chart can be used with sufficient

accuracy for evaluating foundation conditions for most small

structures. Strength and compressibility can be estimated

from knowledge of relative density. 

Penetration resistance tests are also used to evaluate the

liquefaction resistance of sands during earthquakes. The

method consists of comparing site data to data from a

compilation of case histories of liquefaction occurrence.

Case history data are available for performance of silty
CHAPTER 2—INVESTIGATION

169

Figure 2-51.—Standard drilling equipment used to perform penetration tests.

sands during cyclic loading. Liquefaction testing is

normally associated with drilling, testing, and sampling of

loose clean sands and silty sands that must be carefully

drilled. If procedures are not taken to stabilize the loose

deposits, data will be unreliable. Normally, rotary drilling

methods with drill muds are required to stabilize the boring.

The primary cause of disturbance of sands is hydrostatic

imbalance. To maintain hydrostatic balance, the boring

must be kept full of drill fluid during drilling and by use of

a pump bypass during removal of cleanout string and

testing.

Penetration resistance data obtained with the 50-mm (2-in)

diameter sampler are not reliable in gravelly soils. Research

on penetration resistance of gravelly soils has been

performed using larger samplers of 75 to 90 mm (3 to

3 1/2 in) o.d. along with larger hammers, but these tests are

nonstandard. Recovery of coarse-grained soils and accuracy

of blowcount data may be improved using the larger sampler
EARTH MANUAL

170

Figure 2-52.—Sampler requirements for penetration resistance testing.

barrels; however, the analysis of data obtained with this

equipment and procedures should only be used with

engineering supervision and oversight. If engineering

properties of coarse-grained soils must be determined, it is

recommended that accessible borings, in-place density tests,

Becker penetration tests, and shear-wave velocity tests be

performed. 

Penetration resistance data can be used to estimate the

relative consistency of cohesive soils as shown on table 1-1

(ch. 1). Moisture content data from SPT testing can be used

in conjunction with laboratory data from undisturbed

samples to evaluate engineering properties at critical sites.

Vane shear, borehole shear, cone penetration, flat-plate

dilatometer, and pressuremeter tests are better suited for

determining undrained shear strength of medium to very soft

cohesive soils than is the standard penetration test.

e. Becker Penetration Test.&

1. Origin of Becker Penetration Test.&The Becker

penetration test is performed with the Becker hammer drill,

a rugged and specially built hammer-percussion drill. The

drill is used in geotechnical investigations for drilling,

sampling and penetration testing in coarse-grained granular

soils. The drill uses a double-acting diesel pile hammer to

drive a specially designed double-walled casing into the

ground. The casing comes in 2.4- or 3.0-m (8- or 10-ft)

lengths and is available in three standard sizes: 140 mm

(5 1/2 in) O.D. by 83 mm (3 1/4 in) I.D., 170 (6 3/4 in)

O.D. by 110 (4 1/4 in) I.D., and 230 mm (9 in) O.D. by

150 mm (6 in) I.D. The main advantage of the Becker

hammer drill is its ability to sample or penetrate cobbles and

boulder deposits at a fast rate and provide a penetration test

similar to SPTs. The heavy-walled Becker casing is strong

and can break up and penetrate boulders and weak bedrock

[50].

2. Open-Ended Becker Drilling Method.&The

Becker casing can be driven open-ended with a hardened

drive bit for drilling and sampling, in which compressed air

is forced down the annulus of the casing to flush the cuttings

up the center of the inner pipe to the surface. The

continuous cuttings or soil particles are collected at the

ground surface via a cyclone. At any depth, the drilling can

be stopped, and the open-ended casing allows access to the
CHAPTER 2—INVESTIGATION

171

bottom of the hole for tube sampling, standard penetration

test or other in-place test, or for rock coring to be

conducted. On completion of drilling, the casing is

withdrawn by a puller system comprising two hydraulic

jacks operating in parallel on tapered slips that grip the

casing and react against the ground.

3. Close-Ended Becker Drilling Method.&The

Becker casing can also be driven close ended, without using

compressed air, to simulate the driving of a displacement

pile. The idea is to drive the Becker casing close-ended like

a pipe pile and use the recorded blow counts [blows per

0.3 m (1 ft)] to indicate soil density. The Becker denseness

test, or the Becker penetration test (BPT), is generally less

sensitive to gravel particle size than the SPT because of the

larger Becker pipe [140 mm (5 1/2) O.D. and larger]

compared to the SPT sampler [51 mm (2 in) O.D.], and

has, therefore, been found to be useful as an indicator of

density in gravelly soils. As a result, the BPT can be used

for pile driveability and pile length evaluation, as well as for

foundation design, usually through correlations with the SPT

[51]. The BPT is also becoming accepted as a practical tool

for liquefaction potential assessment in gravelly sites, again

through correlations with the SPT [52, 53, 54].

4. Interpretation of BPT and SPT Data.&In order

to make use of the large worldwide foundation performance

data base currently available for the SPT, such as the SPTbased liquefaction data base, there is a need for reliable

BPT-SPT correlations. Numerous attempts have been

carried out in the past to correlate the BPT blow counts to

the SPT N-values. Most of these correlations, however,

have limited applications since they do not take into account

two important factors affecting the BPT blow counts: the

variable energy output of the diesel hammer used in the

Becker system and the soil friction acting on the Becker

casing during driving.

To overcome the variable hammer energy problem in the

BPT, a method was proposed of using the measured peak

bounce-chamber pressures at the top of the double-acting

diesel hammer to correct the measured blow counts to a socalled "constant full combustion condition" [52]. The

corrected BPT blow counts can be correlated to corrected

SPT blow counts. Although an improvement over existing

BPT-SPT correlations, this method still has serious

limitations. The bounce-chamber, pressure-correction

method cannot capture all the important variables affecting

the BPT blow count, and the BPT-SPT correlation does not

consider casing friction in the BPT [55].

f. Cone Penetration Tests.&Cone Penetration testing

was developed in the Netherlands for rapid penetration

testing of low density estuarine deposits. The procedure

consists of measuring the resistance of a 60( apex angle

cone, with 1000 mm2

 projected surface area, being pushed

into the soil at a controlled rate of 20 mm/s. During most

cone tests the force exerted on a cylindrical friction sleeve

located behind the tip is also measured. Procedures for

mechanical and electric cone penetration tests are given in

USBR 7020 and 7021. Cone testing is performed for rapid

delineation of site stratigraphy and estimation of strength,

compressibility, pile capacity and liquefaction resistance. 

With the introduction of electronic cone penetrometers,

penetration resistance data can be collected at intervals as

close as 20 mm (3/4 in) to provide an excellent record of

subsurface stratigraphy. As shown on the example,

figure 2-53, drained behavior in cohesionless deposits

results in significantly higher cone tip resistance than in

undrained clays. The resulting data trace accurately

delineates bedding in layered deposits. The bottom layer,

of the example figure, is a lacustrine deposit under a dam

where seasonal gradational differences in the deposit are

delineated with the cone. Additional sensors can be added

to the cone body to obtain records of:

 ̆ pore pressure,

 ̆ cone inclination,

 ̆ temperature,

 ̆ electrical resistivity or conductivity,

 ̆ seismic wave velocity by use of geophones.

Using the piezocone, soundings can be stopped in sand

layers and hydrostatic pressures can be determined.

Advantages of cone testing include the rapid rate of testing,

ability to obtain excellent soil stratigraphy data, and

repeatability of test data. Disadvantages of cone penetration

testing are the inability to obtain a soil sample and to test

firmer soils because of the large thrust required to push the

cone into the soil. On favorable sites, having good access

and moderate to soft soil conditions, production can reach

60 to 120 meters per day (200 to 400 ft/d) with resulting

minimal exploration costs per meter of sounding. Error in

test data is slight if testing is performed according to USBR

7020 and 7021. On investigations for significant structures,

such as dams, the inability to obtain samples requires that

site-specific correlation be performed with undisturbed

sampling. If the cone is used, the number of expensive

sampling holes may be reduced. Another disadvantage of

cone penetration soundings is that backfill grouting of cone

holes is difficult and requires specialized equipment.

Backfilling may be required when sounding through water

retaining embankments and hazardous waste sites.
EARTH MANUAL

172

Figure 2-53.—Example of electronic cone penetrometer data.
CHAPTER 2—INVESTIGATION

173

Figure 2-54.—Electronic cone penetrometer testing vehicle.

Reclamation uses both mechanical and electrical cone

adaptor kits for drill rigs, as well as an 18-metric-ton

(20-ton), cab-mounted testing vehicle shown on figure 2-54.

The all-wheel-drive, 18-metric-ton, gross-weight vehicle can

advance cones through harder and/or coarser deposits and

to greater depths than conventional drilling rigs, which can

only develop 4.5 to 9 metric tons (5 to 10 tons) of reaction.

Cone penetration testing is limited by thrust capacity and by

durability of the rod and cone system. Lithified deposits

and very firm to hard cohesive soils cannot be readily

penetrated. Dense to medium dense gravel usually impedes

penetration, but loose silty gravels have been penetrated.

The enclosed truck-mounted cone testing rig allows for

testing in difficult weather conditions. Data acquisition,

reduction, and calibration equipment are all contained on

board and allow for onsite data interpretation. A

disadvantage of the large 18-metric-ton truck is access in

soft ground surface conditions. If trafficability problems

exist, all-terrain equipped drill rigs or trailer-mounted drill

rigs using tie down augers for vertical reaction can be used.

Conventional drill rigs used for cone testing should have a

hydraulic feed system to ensure smooth, steady, quasi-static

advance of the cone.

Primary use of cone penetration testing in Reclamation is for

stratigraphic mapping. Cone testing is performed to acquire

data in between conventional drilling and sampling holes.

Correlations between cone data and soil classification, and

strength and compressibility of sands and clay, have been

developed for both mechanical and electrical cones [56, 57].

In clean sands, design methods for evaluating settlement of

footings using cone data are accepted as one of the most

reliable techniques. Reclamation has found that some

degree of site specific data analysis is required to refine

some of these correlations to achieve sufficient accuracy for

design data purposes. For example, when evaluating

undrained shear strength of clay, it is required that other

field or laboratory tests be performed because the cone

bearing capacity factor, Nk, varies widely. Recent

researchers have focused on using dynamic pore pressures

from the piezocone to refine these correlations. However,

piezocone testing requires additional time and effort to

prepare and calibrate the cone and prevent cavitation of the

element. Cavitation of the saturated pore pressure

measuring element is a problem when the sounding must

first penetrate unsaturated zones or sands near the surface

which dilate and cavitate the system.

g. Dynamic Penetrometers.&In Europe, dynamic

penetrometers are frequently used for performing rapid

soundings to develop site stratigraphy. Many different

standards exist, depending on the country of use.

Procedures consist of driving a cone pointed penetrometer

with repeated hammer blows and counting the number of

blows to advance the point a given distance. Most dynamic

penetrometer systems are portable and use automatic means

to lift and drop the hammer, thereby reducing variability in

the test method as well as experience and training required

for operators. Dynamic soundings provide an economic

means to perform investigations at close spacings. Most

penetrometers can penetrate gravelly soils. Reclamation has

not used dynamic penetrometers to a significant degree.
EARTH MANUAL

174

h. In Situ Strength and Modulus Tests.&General.&

Many new methods of in situ load testing are being studied

in an effort to improve prediction of engineering properties

of soil and rock in place. The term "in-situ" is often used

to describe these tests in geotechnical engineering and is

used here to signify that the test actively loads the

surrounding soil. Elsewhere in this manual, the term "in

place" is used to describe in-place conditions.

In most of the in situ tests, loads are applied to the soil, and

deformation or shearing resistance is measured. Most

methods depend on carefully preparing a prebored drill hole

to minimize borehole wall disturbance. In many cases,

several different drilling techniques will need to be

attempted prior to successful operation of the test. Testing

specialists need to participate in the early phases of planning

and testing. Even with increased cost of additional efforts

in drilling, savings may be realized in the overall

exploration program through reduction in laboratory or

other in situ testing. The advantage of in situ tests is that

the soil is tested at existing stress conditions; whereas in

laboratory testing, detrimental effects of unloading (stress

relief) and reloading must be considered. In soft weathered

rocks and friable deposits, sometimes it is impossible to

recover samples for laboratory specimens, and properties of

these low recovery zones are often most critical to design of

the structure. In situ tests offer the means by which

engineering properties may be obtained in the absence of

available samples for laboratory testing.

i. Field Vane Tests.&The vane method of testing is

widely accepted for determining undrained shear strength of

soft to very soft consistency clays. The test consists of

pushing a four-bladed vane into the soil at the bottom of a

borehole and measuring the rotational torque required to

rapidly fail the soil. Equipment and procedures for

performing the vane shear test are described in USBR 7115.

Even though the vane shear test can be used to delineate

stratigraphy, it may be more economical to perform cone

penetration or flat-plate dilatometer testing for this purpose.

In most vane shear testing, a remolded strength

determination is also made to assess sensitivity of the clays.

Determination of sensitivity of clays is difficult in the

laboratory and is best determined using field vane shear

testing. 

Vane shear testing requires a rotary drill rig to drill and

clean the boring and to press the vane into undisturbed soil.

Reclamation has modified the BX casing housing of the

vane and rods to act as a rotary drill string. During drilling,

the vane is retracted inside the BX cutting bit. This

modification reduces hole disturbance in very soft clays and

precludes the need to withdraw the entire drill string and

lower it again every time a vane test is performed.

Determination of rod friction is easily accomplished using

Reclamation’s vane shear device which is equipped with a

special vane slip coupling system.

j. Pressuremeter Testing.&Pressuremeter tests are

performed to characterize the stress-strain behavior of soil

and rock in place. Tests are performed by measuring the

pressure and resulting volume change increments of a

cylindrical expandable measuring cell which is inserted into

a carefully prepared borehole (fig. 2-55). The measuring

cell or probe is typically inserted into a prebored drill hole;

but in some instances, it is advanced by self-boring or

driving. Reclamation test procedures are still under

development, but satisfactory procedures for interim use are

given in ASTM procedure D 4719 [59]. 

Pressuremeter tests can be used to determine the in-place

modulus of deformation of a wide variety of soils and rock

for which undisturbed sampling and laboratory testing are

difficult. The data are primarily used to evaluate anticipated

structural settlements. Usually, testing is performed with

pressure increments applied at 1 minute intervals, which

results in undrained loading of fine-grained soils.

Undrained strength of cohesive soils can be estimated from

the limit pressure (pressure at infinite expansion), but

requires extrapolation of test data. The pressuremeter is the

only reliable method of determining the in-place friction

angle of sands using stress-dilatency theory. However, use

of a self-boring pressuremeter is required in saturated loose

sands to minimize drilling disturbance.

Rock pressuremeters (dilatometers) with maximum pressure

capability approaching 35.5 MPa (5,000 bf/in2

) can be used

to evaluate deformation modulus in hard rock to soft rock

and in areas of low recovery. Strength interpretation of

both hard rock and softer rock is difficult, highly

theoretical, and requires interpretations of stress-strain

paths. Strength test data interpretation in cemented soils and

soft or fractured rock is especially difficult. As a result of

these difficulties, Reclamation still uses the rock dilatometer

primarily to evaluate deformation modulus, and other field

and laboratory tests are performed to determine strength.

Pressuremeter testing has been performed in gravelly soils

by driving a slotted AW casing to protect the pressuremeter,

but effects of driving displacements in gravel are not fully

understood.

Pressuremeter testing in soils requires exacting execution of

drilling to: (1) minimize disturbance of the borehole wall

and (2) provide a borehole diameter within allowable

tolerance. Test procedures require that the borehole be no
CHAPTER 2—INVESTIGATION

175

Figure 2-55.—Menard pressuremeter equipment. 

 (Baguelin, Jézéquel, and Shields [58])

smaller than 97 percent of probe diameter or 20 percent

greater than probe diameter when testing soils. Even tighter

borehole diameter requirements are required for rock

dilatometers. Since testing is typically performed in

materials which are difficult to sample, a variety of drilling

methods may need to be attempted to achieve success. In

very soft clays and loose saturated sands the self-boring

pressuremeter is recommended. Two self-boring

pressuremeters are shown in figure 2-56. A recent trend in

self-boring pressuremeters is using jetting instead of rock

bitting for hole advancement. If jetting is used, the

pressuremeter body should be equipped with fluid pressure

sensors to ensure that circulation is maintained. Wall

disturbance can be evaluated from the pressure-volume data.

Testing duration can be up to 1 to 2 hours per interval.

Although pressuremeter testing is one of the more expensive

in-place tests, the testing is still performed at less cost than

obtaining undisturbed samples and performing laboratory

testing. 

k. Soil and Rock Borehole Shear Testing.&Borehole

shear testing is performed for rapid 

determination of shearing resistance. The test consists of

lowering two diametrically opposed shear plates into a

borehole, applying a normal force to seat the plates into the

borehole sidewalls, and applying shearing force to the plates

by vertically pulling on rods connecting to the ground

surface. A schematic of the equipment is shown in

figure 2-57. The soil borehole shear test was developed by

Prof. Handy of Iowa State University. Later, under a

Bureau of Mines research program, a rock borehole shear

device was developed with capability for exerting normal

forces of 35 MPa (5,000 lbf/in2

). Testing procedures for

rock borehole shear devices are under development by

Reclamation and the American Society for Testing

Materials.

Borehole shear testing requires careful drilling to minimize

disturbance to the borehole walls and to ensure appropriate

borehole diameter. Usually, for rock borehole shear

testing, NX diameter boreholes should not exceed 83 mm

(3.25 in) in diameter. Shear stress and normal stress data

can generally be obtained at three normal stresses at one

location in the borehole within 30 minutes to 1 hour and

results in significant cost savings over laboratory testing.
EARTH MANUAL

176

Figure 2-56.—Self-boring pressuremeters. (Jamiolkowski, Ladd, Germaine,

and Lancellotta [60])

Strength interpretation of data from the borehole shear test

in soils is complicated by the need to evaluate loading rate

and resulting drainage conditions. A pore pressure sensor

has been added to the shear plates to provide data on

consolidation and drainage, so application of load can be

evaluated. Borehole shear testing is not recommended for

cohesionless soils or soft to very soft cohesive soils because

of the difficulty in borehole preparation. Gravel particles in

soils may result in invalid test results because of nonuniform

stress distribution around the plates. Testing is most

successful in firmer cohesive deposits, which are easily

sampled for laboratory testing; as a result, testing in soils is

not performed often.

Borehole shear testing of rock is economical and provides

accurate test data [62]. It is a viable alternative to more

expensive laboratory testing. Testing has been performed

on a wide range of rocks including lightly cemented

sandstones and claystones, and of coals to hard granites.

Laboratory shear strength tests tend to overestimate strength

values, as only cores with sufficient length to diameter ratios

are tested. Borehole shear testing permits testing of low

sample recovery zones that are often the most critical for

design. The normal force plates of the rock testing

apparatus allow testing at three normal stresses at a single

elevation in the borehole by rotating the shear head to an 

untested area of the borehole. Testing intervals as close as

50 mm (2 in) in elevation may be tested, depending on

materials. The close spacing allows testing of thin seams

and shear zones.

l. Flat Plate Dilatometer Test.&The flat plate

dilatometer test (DMT) is performed to determine

compressibility and shearing strength of a wide range of inplace soils [63]. The test requires advancing (by pushing)

a blade-shaped penetrometer with an expandable membrane

(fig. 2-58) into the soil using a drilling rig or cone

penetration equipment. After pushing the dilatometer to the

desired depth, the membrane is pneumatically expanded,

and pressures are recorded at two positions of membrane

deflection. Tests are normally performed at 200-mm (8-in)

depth intervals. Testing is rapid and repeatable with simple

equipment and operation. By using the expanding

membrane, the instrument can more accurately determine

soil compressibility than cone penetration testing and with

similar economy in exploration costs. Testing procedures

are under development by American Society for Testing

Material, but are well established by more than 10 years of

engineering experience [65]. The DMT testing can provide

an estimate of soil type based on differences in the two

deflection pressures. The pressure difference reflects

drainage conditions influenced by permeability and

coefficient of consolidation. With addition of thrust data to
CHAPTER 2—INVESTIGATION

177

Figure 2-57.—Borehole shear device. (Wineland [61])

Figure 2-58.—Dilatometer test equipment. (Schmertman [65])
EARTH MANUAL

178

advance the dilatometer, the DMT provides data for

defining subsurface stratigraphy similar to cone penetration

testing.

The flat plate dilatometer provides data to accurately

evaluate compressibility in normally consolidated clays and

sands. Undrained strength in normally consolidated to

lightly overconsolidated clays is equivalent to uncorrected

vane shear strengths making the DMT an economical

alternative or supplement to vane shear testing. DMT data

can be used to estimate stress history and changes in stress

history. Field studies have been performed in

overconsolidated deposits to provide empirical correlations

to engineering behavior. Prediction of friction angle in

sands is performed using wedge penetration theory and

requires measurement of thrust required to push the

dilatometer into the ground. Since thrust is typically

measured at the surface, rod friction limits depths in which

friction angle can be accurately predicted.

Using 18-metric-ton (20-ton), truck-mounted, cone

penetration testing equipment, the DMT can be pushed

quasi-statically through soils with SPT N values less than

30. Stronger soils require preboring using conventional

drilling equipment. The DMT testing is not suitable for

testing gravelly soils. Testing rates of up to 50 meters per

day (165 ft/d) can be obtained. Operation and maintenance

of the testing equipment is simple.

m. Pocket Vane Shear Test.&The hand held vane

shear testing device (Torvane) is used for rapid evaluation

of undrained shear strength of saturated cohesive soils. It

can be used on tube-type samples, block samples, or on

sides of test pits in the field. Values obtained from these

tests are sometimes useful to assist in planning laboratory or

field investigations. The Torvane is designed for use on

saturated, fine-grained cohesive soils. Torvane tests should

always be performed in the ends of thin wall samples of soft

clays in the field. The data regarding consistency is of great

assistance in selecting laboratory tests to be performed on

clay samples. The presence of coarse sand or gravel in test

specimens could result in erroneous values of undrained

shear strength of soil. If the test specimen contains coarsegrained material, the Torvane should not be used, and other

shear strength measuring techniques should be performed.

The device is shown on figure 2-59.

The Torvane device is a small vane shear meter capable of

measuring shear strengths between 0 and 2.5 kg/cm2

(2.5 ton/ft2). The Torvane dial is marked with major

divisions in units of 0.05 kg/cm2

 (0.05 ton/ft2) to permit

visual interpolation to the nearest 0.01 kg/cm2

 (0.01 ton/ft2).

To perform the test, a flat area on the side of a test pit or

undisturbed sample is selected. A vane size is selected

which is appropriate for the material being tested. Several

trials may be necessary to determine the correct vane size.

Too small a vane will produce dial readings of insufficient

magnitude to register on the dial head, while too large a

vane will produce readings too great for the scale. A larger

vane adapter is shown on figure 2-59. The vane is carefully

pressed into the cohesive soil to the depth of the vane

blades. The Torvane knob is turned while a constant

normal load is kept on the device by finger pressure against

the knob. A rate of rotation that causes failure in 5 to

10 seconds is recommended. After failure occurs, the dial

head reading indicated by the pointer is read and recorded,

and the shear strength is calculated. The procedure for

performing this test is outlined in USBR 5770. Field data

taken from sample tubes should be noted in the comments

column of the undisturbed soil sampling data sheet 7-1656

(USBR 7105)

n. The Point-Load Strength Test.&Rock strength is

an important property, and a suitable strength-index test is

required. Simple "hammer and penknife" tests can be used;

however, this approach seldom provides objective,

quantitative, or reproducible results. The uniaxial

(unconfined) compression test has been widely used for rock

strength classification but requires machined specimens and,

therefore is an expensive technique&essentially confined to

the laboratory.

The point-load test is conducted in the field on unprepared

rock specimens using simple portable equipment. Two

types of point-load test machines are available as shown on

figure 2-60. Essentially, the test involves compressing a

piece of rock between two points. The point-load index is

calculated as the ratio of the applied load to the square of

the distance between the loading points. As illustrated on

figure 2-61, the point-load test has a number of variations

such as the diametral test, the axial test, and the irregular

lump test. 

The strength at failure is expressed as a point load index, Is.
CHAPTER 2—INVESTIGATION

179

(b) Side view. Note vane at bottom.

(d) Adaptor: 0 to 2.5 ton/ft2 (c) Adaptor: 0 to 0.2 ton/ft . 2.

(a) Top view.

Figure 2-59.—Torvane (pocket-vane shear meter) equipment.

An approximate correlation exists between the point-load

index and the uniaxial compressive strength, Oc , as shown

on figure 2-62 and is given by: Oc = 24 Is.

In the above equation, the constant 24 is for a 54-mm

(2.125-in)(NW)-diameter core. For other core sizes, values

are: 20 mm (0.750 in)(RW) = 17.5, 27.0 mm

(1.062 in)(AQ) = 19, 36.5 mm (1.432 in)(BQ) = 21,

47.6 mm (1.875 in)(NQ) = 23, and 63.5 mm (2.500

in)(HQ) = 24.5.

Reclamation experience indicates the above correlation may

vary with geologic rock type as well as the condition of the

core. On important projects, such as tunnels and pressure

shafts, a site-specific correlation should be developed and

the variability of the results evaluated.
EARTH MANUAL

180

Figure 2-60.—Point-load strength testing machines.
CHAPTER 2—INVESTIGATION

181

Figure 2-61.—Point-load strength testing variations (a) diametral test,

(b) axial test, (c) irregular lump test.

To judge whether a point-load test is valid, the fractured

pieces of core should be examined. If a clean fracture runs

from one loading point indentation to the other, the test

results can be accepted. However, if the fracture runs

across some other plane, as might happen when testing

schistose rocks, or if the points sink into the rock surface

causing excessive crushing or deformation, the test should

be rejected.

o. Portable Direct Shear Rock Testing

Device.&Shear strength is an important factor for stability

of a rock slope. The shear strength of a potential failure

surface that may consist of a single discontinuity plane or a

complex path following several discontinuities and involving

some fracture of the intact rock material must be

determined. Determination of reliable shear strength is a

critical part of a slope design because relatively small

changes in shear strength can result in significant changes in

the safe height or angle of a slope. To obtain shear strength

values for use in rock slope design, some form of testing is

required. This may take the form of a sophisticated

laboratory or in-place test in which all the characteristics of

the in-place behavior of the rock discontinuity are

reproduced as accurately as possible. Alternatively, the test

may involve a simple determination depending upon

facilities available, the nature of the problem being

investigated, and the stage of the investigation.

A portable direct shear device for testing rock

discontinuities is shown on figure 2-63. This machine was

designed for field use; many of the refinements present on

larger machines were sacrificed for simplicity and

portability. A typical test can be performed in this device

in about 15 to 30 minutes. As shown on figure 2-63(b), the

test specimen is oriented and encapsulated in the shear box

halves so the discontinuity is aligned within the shear plane

of the testing device. Specimen size is limited to about

100-mm- (4-in-) diameter core or other shapes of about

100 mm (4 in) in dimension.
EARTH MANUAL

182

Figure 2-62.—Relationship between point-load strength index and uniaxial-compressive strength.

1MPa = 10.2 kg/cm2

 = 145 lb/in2.

Stationary high pressure rock direct shear machines in the

Earth Sciences laboratory are available for testing larger

specimens. Reclamation has direct shear machines capable

of testing 150- and 250-mm- (6- and 10-in-) diameter

specimens at normal stresses of up to 700000 kPa

(100,000 lbf/in2

).

p. Large-Scale, In-Place, Direct Shear

Tests.&Direct shear testing of small rock cores may not

produce accurate data because of scale effects. In many

cases, it is desirable to test rock with discontinuities which

are difficult to sample or which could be disturbed by the

sampling process. If shear strength information is critical

on large structures such as dams or powerhouses,

performing large scale in-place shear tests may be

necessary. These tests are expensive and difficult to

perform. The test can be performed in accessible openings

or adits. Figure 2-64 shows the arrangement for testing in

an adit where the normal force is applied through reaction

to the tunnel crown. Test specimens are normally 380 by

380 square by 250 mm (15 × 15 × 10 in) deep. Shear

loads, approximating structure loading, are applied, and

there is only one peak strength determination prior to sliding

shear strength determinations. Normal stresses of up to

7,000 kPa (1,000 lbf/in2

) have been tested. A more detailed

description for conducting these tests is presented in

reference [66] and in the following section.

q. Uniaxial and Radial Jacking Tests in

Rock.&Borehole dilatometer tests and tests performed on

core samples may not produce representative results because

they reflect behavior of only a small percentage of a rock

mass. Modulus of deformation of laboratory specimens is

usually higher than true rock mass behavior because joints

and discontinuities are not included in the specimen.

Borehole tests may include some discontinuities and result

in lower moduli. The stress field from a large structure,

such as an arch dam, may extend well into an abutment and

may include many discontinuities which influence the

behavior of the structure itself. To accurately design such

structures, larger-scale tests have been developed. Uniaxial

jacking tests such as those depicted in figure 2-65 can be

performed in exploration adits. Uniaxial tests can be

aligned to simulate thrust direction produced by the structure

and to accommodate arrangement of jointing and

discontinuities present in the rock. Uniaxial tests are always

performed to provide data for the design of large concrete

dams. The tests are major undertakings and are expensive.

Radial jacking tests have also been developed to simulate

"circumferential" in-place stresses for larger areas [67].
CHAPTER 2—INVESTIGATION

183

Figure 2-63.—Sketch of portable direct shear device.

Aluminum components are used to perform the uniaxial

jacking test; and 0.9-m- (3-ft-) diameter hydraulic circular

flat jacks are used for applying reaction to the column.

Jacking pressure (simulated structure load on the rock) of up

to 7,000 kPa (1,000 lbf/in2

) can be applied. Deformation is

monitored in two NX size boreholes located in the center of

the jacking pad. Seven-point retrievable steel rod

extensometers are installed in each drill hole to monitor

deformations at various depths from the rock face. 

Locations of the extensometer anchors are such that both

closing of surficial cracking and rock mass deformation can

be evaluated. Usually, load increments are applied in 1,500

kPa (200-lbf/in2

) increments and sustained for 1 or 2 days,

followed by complete unloading and evaluation of set [68].

The test site preparation is the most time consuming

activity. Tunnel adits must be expanded to a minimum

diameter to accommodate equipment. Test areas must be

carefully prepared to remove any blast damaged material by

using pneumatic chipping hammers and drills.

D. Recording and Reporting of Data

2-22. Maps.&Information which requires many pages

of narrative can be shown on a map. Among the many

varieties of mapping methods available, some suitable

procedure can be found that will convey the necessary

information clearly and easily.

a. General.&Three scale ranges for maps are

commonly used. Maps ranging in scale between 1 and

10 miles per inch are usually suitable for showing the

general area of the work; describing access and

transportation facilities such as highways, railroads, rivers,

and towns; and locating special types of material deposits

such as riprap or aggregates. Map scales ranging between

5,000 feet per inch and 400 feet per inch often are used for

more detailed information covering the immediate vicinity of

the work; general geology of the area; reservoir areas;

location of borrow pits; right-of-way lines; locations of
EARTH MANUAL

184

Figure 2-64.—Shear and sliding friction testing equipment, Auburn damsite.

roads, canals, and transmission lines; and similar

information. To provide detailed information on a structure

site, map scales ranging between 500 feet per inch and

20 feet per inch are commonly used; but long, low damsites

with limited relief may be mapped at a scale of 1,000 feet

per inch. Locations of small structures where local detail is

important may be mapped on scales of 20 feet per inch. In

selecting a scale, it is desirable to keep the ratio of ground

measurement to map measurement as simple as possible; for

example, the added detail that can be shown using a scale of

750 feet per inch may be less beneficial than the

convenience of using a scale of 1,000 foot per inch. Also,

the complete map should not be larger than may be

conveniently spread on an ordinary table. The map' s scale

and a north arrow must always be shown. Further specific

guidance is provided for proper scaling of various geologic

maps in the Engineering Geology Field Manual [20] and

Engineering Geology Office Manual [69].

State plane coordinate systems are preferred. All detail

maps should be controlled by a coordinate system or other

definite means of locating points on the ground. The grid

lines should run true north and south, and east and west. If

a local grid system is established, the origin of the system

should be to the south and west of the area under

consideration, and the displacement should be

predominantly in one direction, so there will be a major

numerical difference between the north and east coordinates

of any point. If a damsite is involved, the displacement

should be sufficient so the entire work area, including
CHAPTER 2—INVESTIGATION

185

Figure 2-65.—Uniaxial jacking test.

borrow areas, plots within the northeast quadrant. The grid

system should be referenced to public land surveys,

triangulation stations, and other prominent permanent

features in the area.

Variations in elevation are depicted on detail maps by use of

contours. Contour intervals required may range from 20-

or 25-foot intervals to 2-foot intervals, and, occasionally,

1-foot intervals depending on the map scale, the irregularity

of the land surface, and the map use.

In general, contours should be sufficiently close together so

that elevations between contours can be determined with

confidence, but sufficiently separated so that a contour can

be visually followed without difficulty. Elevations should

always be referred to sea level on the basis of the

nationwide survey system of the U.S. Geological Survey or

U.S. Coast and Geodetic Survey. If an assumed datum is

used for reconnaissance purposes, this elevation selected

should not conflict with any known elevations.

Topographic maps are necessary in exploration of

foundations and construction materials for hydraulic

structures. The locations and elevations of exploratory

holes, outcrops, and erosional features can be shown on the

map, and landforms portrayed by contours can indicate, to

some degree, the type of soil and subsurface geologic

conditions. In the absence of topographic map coverage or

where greater detail is needed, photogrammetric methods

are used to produce maps of any desired scale and contour

interval.

Commonly available general purpose topographic maps

(e.g., USGS-type maps) are not detailed enough for sitespecific needs. Topography for engineering exploration,

design, and construction must be generated for the specific

application. Horizontal scales of 1 inch to 50 or 100 ft and

contour intervals of 1 to 5 ft are common. Site-specific

maps are usually generated photogrammetrically using aerial

photographs flown for the application, although small maps

may be prepared using plane table or ground survey data.

Topographic maps are generated from aerial photographs by

viewing the photos in an analytical plotter. The plotter

permits manual or automatic generation of lines of equal

elevation at predetermined intervals and scales derived from

stereo images of the photos.

The coordinate system used on a map to locate features

depends on the needs or conventions of the project. State

plane coordinates are usually used, but older projects may
EARTH MANUAL

186

still use local coordinate systems set up for the specific

project. The measurement units (U.S., metric, or degrees)

are determined by the needs of the project.

Reference point accuracy is categorized in orders,

depending on the need of the project. The locations of

benchmarks vary in accuracy and may vary from precisely

located geodetic benchmarks to locations scaled off a

topographic map. The geodetic survey provides data on

benchmark location, including those set by the USGS.

The map datum used for determining the map coordinate

system is important because older maps generally use

obsolete datums (e.g., NAD 27 used on most USGS

quadrangles) and new maps or measurements use new

datums (e.g. NAD 83). Mixing datums can produce

apparent errors of several hundred feet that are often

difficult to resolve. 

Site topographic maps are used as base maps for geologic

mapping as well as for foundation design and construction

excavation maps. These site-specific maps are generally

updated during construction to document actual conditions

encountered. Updates are made by ground survey or are

reflown on major jobs. Material quantities are often

determined by successive topographic mapping as

excavation proceeds.

When having specialized topographic maps made, several

factors are important. The scale, contour interval, and area

are the most important factors and are determined by the

needs of the project. The map datum (generally NAD 27 or

NAD 83) and the map medium are also very important. All

topography should be provided on paper and digitally.

Site geologic maps are used for the design, construction,

and maintenance of engineering features. These maps

concentrate on geologic and hydrologic data pertinent to the

engineering needs of a project and do not address the

academic aspects of the geology. In addition to published

topographic maps, the USGS has other information for

mapped areas; for example, location and true geodetic

potion of triangulation stations and elevation of permanent

benchmarks established by the USGS.

The horizontal and vertical accuracy and precision of

locations on a map depend on the spatial control of the base

map. General base map controls are (in decreasing

accuracy and precision): 

(1) survey control or controlled terrestrial photogrammetry,

mapped from survey-controlled observation points or by

plane table or stadia; 

(2) existing topographic maps. Control for these maps

varies with scale. The most accurate are large-scale

photogrammetric topographic maps generated from aerial

photographs for specific site studies; 

(3) uncontrolled aerial/terrestrial photogrammetry. Camera

lens distortion is the chief source of error; 

(4) Brunton compass/tape surveys. These surveys can be

reasonably accurate if measurements are taken with care; and

(5) sketch mapping. Practice is needed to make reasonably

accurate sketch maps. 

The geographical positioning system (GPS) may provide

adequate position locations depending on the required

accuracy or precision.

The geographical positioning system is a system of satellites

that provides positioning data to receivers on earth. The

receiver uses the positioning data to calculate the location of

the receiver on earth. Accuracy and type of data output

depend on many factors that must be evaluated before using

the system. The factors that must be evaluated are:

• Project requirements.—The location, accuracy, or

precision needed by the project is a controlling factor

in whether GPS is appropriate for the project. The

actual needs of the project should be determined, being

careful to differentiate with “what would be nice.”

Costs should be compared between traditional

surveying and GPS.

• GPS equipment.—Different GPS receiver systems

have different accuracies. Accuracies can range from

300 ft to inches (100 m to mm) depending on the

GPS system. Costs increase exponentially with the

increase in accuracy. A realistic evaluation of the

typical accuracy of the equipment to be used is

necessary, and a realistic evaluation of the needed, not

“what would be nice,” accuracy is important. Possible

accuracy and typical accuracy are usually not the same.

• Data parameters.—The datum or theoretical reference

surface to be used for the project must be determined

at the start. USGS topographic maps commonly use

NAD 27, but most new surveys use NAD 83.

Changing from one datum to another can result in

apparent location differences of several hundred feet

(hundreds of meters).

The map projection is the projection used to depict the round

shape of the earth on a flat plane or map. The most common

projections used in the U.S. are the transverse Mercator and

the Lambert conformal conic. State plane coordinate systems
CHAPTER 2—INVESTIGATION

187

almost exclusively use one or the other. To use these state

plane projections, location and definition parameters are

necessary.

• Transverse Mercator.—The transverse Mercator

projection requires a central meridian, scale reduction,

and origin for each state or state zone. 

• Lambert conformal conic.—The Lambert conformal

conic projection requires two standard parallels and an

origin for each state or state zone.

The coordinate system is the grid system that is to be used on

the project. The state plane system is used by most projects,

but latitude/longitude, universal transverse Mercator, or a

local coordinate system may be used. 

Standard American units or metric units should be selected as

early in the project as possible. Conversions are possible, but

converting a large 1-foot contour map to meters is no trivial

matter.

Remember that when using several sources of location data,

the reference datum must be known. Systematic differences

in location data are generally due to mixing datums.

Location and general maps are oriented with north at the top

of the page. Detail maps for water conveyance or storage

structures are oriented for water movement to the top or to

the right of the page. Railroad and highway location maps

are oriented according to the practices of the organization

involved. Every map has a north arrow.

Location maps should show all established transportation

routes and communities adjacent to the area under

consideration. Reservoir maps should show all major

constructed fixed facilities including but not restricted to

railroads, highways, pipelines, canals, telephone lines, and

powerlines; buildings, mines, cemeteries, reservoirs, and

wells. Also, the type and kind of plant cover should be

shown. Detail maps, in addition to showing the above

features, should show rock outcrops, talus, recognizable

landslides, waterways, survey monuments and benchmarks;

and section, township, and county lines.

For specifications, a map is required showing the extent to

which right-of-way will be acquired for the structure

involved. The map should show property lines and

ownership of individual areas.

b. Site Geologic Mapping.&Engineering geologic

mapping is done in two phases, mapping prior to

construction based on study levels, and mapping during

construction. In general, the following suggestions are for:

(1) general mapping requirements for the job; (2) type of

documentation needed; and (3) mapping requirements.

 

1. General Requirements.&Relatively detailed site

geologic mapping studies generally are done for most

structures or sites. Site mapping requirements are controlled

by numerous factors, the most important of which are the

type and size of structure to be built or rehabilitated, the

phase of study (planning through operation and

maintenance), and the specific design needs.

Site mapping studies for major engineering features

should be performed within an approximate 5-mile

radius of the feature, with smaller areas mapped for less

critical structures. These studies consist of detailed

mapping and a study of the immediate site, with more

generalized studies of the surrounding area. This

approach allows an integration of the detailed site

geology with the regional geology. The overall process

of site mapping is a progression from preliminary,

highly interpretive concepts based on limited data, to

final concepts based on detailed, reasonably welldefined data, and interpretation. This progression builds

on the previous step using more detailed and usually

more expensive methods of data collection to acquire

additional and better defined geologic information.

Typically, site mapping is performed in phases:

(a) preliminary surface geologic mapping; and (b)

detailed surface geologic mapping, and construction

geologic mapping. These phases are roughly equivalent

to reconnaissance (or preliminary), feasibility, design,

and construction geology mapping. All site mapping

studies begin with preparation of a preliminary surface

geologic map which delineates surficial deposits and

existing bedrock exposures. The preliminary surface

geologic map is then used to select sites for dozer

trenches, backhoe trenches, and drill holes. These

explorations provide data for the present and later

mapping phases. Surface geologic maps are then

reinterpreted based on the detailed surface and

subsurface data. If required, detailed subsurface

geologic data are also obtained from exploratory shafts

and adits. The later mapping phases are generally the

same but become more detailed and specific for the

project.

2. Documentation.&Site data are documented on

drawings (and associated notes) generated during the study.

The drawings fall into two general categories&working

drawings and final drawings. Working drawings serve as

tools to evaluate and analyze data as they are collected and
EARTH MANUAL

188

to define areas where additional data are needed. Analysis

of data in a three-dimensional format is the only way the geologist can arrive at an understanding of the site geology,

and it is critical these drawings be generated early in the

study and continuously updated as the work progresses.

These drawings are used for preliminary data transmittals.

Scales used for working drawings may permit more detailed

descriptions and collection of data that are not as significant

to the final drawings. Final drawings are generated late in

the mapping program after the basic geology is well

understood. Although working drawings may be finalized,

many times, new maps and cross sections are generated to

illustrate specific data that were not available or well

understood when the working drawings were made. These

drawings serve as a record of the investigations for special

studies, specifications, or technical record reports. Site

mapping documentation is developed in phases: preliminary

surface geologic mapping and detailed surface geologic

mapping.

Preliminary surface geologic mapping.&The purpose of

preliminary surface geologic mapping is to define the

major geologic units and structures in the site area and

the general engineering properties of the units.

Suggested basic geologic maps are regional

reconnaissance maps at scales between 1 inch =

2,000 feet and 1 inch = 5,280 feet (1:24,000 to

1:62,500) and a site geology map at scales between

1 inch = 20 feet and 1 inch = 1,000 feet (1:250 to

1:12,000). Scale selection depends on the size of the

engineered structure and the complexity of the geology.

Maps of smaller areas may be generated at scales larger

than the scale of the base map to illustrate critical

conditions. Cross sections should be made at the same

(natural) scale (horizontal and vertical) as the base

map’s scale unless specific data are better illustrated at

an exaggerated scale. Exaggerated scale cross sections

are generally not suited for geologic analysis because

the distortion makes projection and interpretation of

geologic data difficult. 

Initial studies generally are a reconnaissance-level

effort, and the time available to do the work usually is

limited. Initially, previous geologic studies in the

general site area are used. These studies should be

reviewed and field checked for adequacy, and new data

should be added. Initial base maps usually are generated

from existing topographic maps, but because most

readily available topography is unsuitable for detailed

studies, site topography at a suitable scale should be

obtained if possible. Existing aerial photographs can be

used as temporary base maps if topographic maps are

not available. Sketch maps and Brunton/tape surveys or

global-positioning-system (GPS) location of surface

geologic data can be done if survey control is not available. Good notes and records of outcrop locations and

data are important to minimize re-examination of

previously mapped areas. Photography is a highly

useful tool at this stage in the investigation, as photos

can be studied in the office for additional data. Only

after reasonably accurate surface geology maps have

been compiled can other investigative techniques such

as trenching and core drilling be used to full advantage.

For some levels of study, this phase may be all that is

required.

Detailed Surface Geologic Mapping.&The purpose of

detailed surface geologic mapping is to define the

regional geology and site geology in sufficient detail

that geologic questions critical to the structure can be

answered and addressed. Specific geologic features

critical to this assessment are identified and studied, and

detailed descriptions of the engineering properties of the

site geologic units are compiled. Project nomenclature

should be systematized and standard definitions used.

Suggested basic geologic maps are similar to those done

for preliminary studies, although drawing scales may be

changed based on the results of the initial mapping

program. Maps of smaller areas may be generated to

illustrate critical data at scales larger than the base

map’s scale. The preliminary surface geology maps

are used to select sites for dozer trenches, backhoe

trenches, and drill core holes. As the surface geology is

better defined, drill hole locations can be selected to

help clarify multiple geologic problems. Detailed

topography of the study site should be obtained if not

obtained during the initial investigations. Data

collected during earlier phases of investigations should

be transferred to the new base maps, if possible, to save

drafting time. Field mapping control is provided

primarily by the detailed topographic maps and/or GPS,

supplemented by survey control if available or

Brunton/tape survey. If not, small scale aerial

photographs of the site area flown to obtain detailed

topography are useful in the geologic mapping.

2-23. Logging of Exploratory Holes.&

a. Location of Holes.&The initial holes drilled or

excavated in an area are usually to clarify geological

conditions. Therefore, the location is governed primarily by

the geology; the final holes are drilled or excavated

primarily for specific geology or engineering purposes and

are located on the basis of the engineering structure to be

built. Holes are also drilled or excavated both to establish

the form and shape of a geologic unit and to examine the
CHAPTER 2—INVESTIGATION

189

character of a geologic discontinuity. Although it is

desirable to locate holes so as to satisfy as many of these

requirements as possible, sometimes, these respective

requirements are contradictory and separate holes are

required. From an engineering standpoint, holes that

bracket a condition are more desirable if other design

requirements provide sufficient flexibility so the structure' s

location can possibly be moved to avoid an unfavorable

condition. From a geologic standpoint and for those

engineering situations where the questionable area cannot be

avoided, holes in questionable areas are preferable.

Every hole drilled or excavated should be definitely located

in space. The hole should be tied either to the coordinate

grid system and have a coordinate location or be tied to a

location in some other satisfactory manner such as stationing

or section ties. The elevation at the top of each borehole

should be established by survey or reliable global

positioning system. Coordinates and elevation of an

exploration hole or trench should refer to the center of the

excavation. However, if more than one log is required to

adequately describe the materials in a trench, the coordinates

and elevations of each log should be supplied. The direction

of the longitudinal axis of trenches should also be indicated.

Any hole drilled or excavated should be logged for the full

depth of hole. If, for any reason, a portion cannot be

logged, the interval not logged should be recorded along

with an explanation stating the reason for omission. The

bearing and angle from horizontal of angle holes must be

reported.

b. Identification of Holes.&To ensure completeness of

the record and to eliminate confusion, test holes should

normally be numbered in the order of excavation, and the

series should be continuous through the various stages of the

work. If a hole is planned and programmed, it is preferable

to maintain the hole number in the record as "not drilled" or

"abandoned" with an explanatory note rather than reuse the

hole number elsewhere. However, it is permissible to move

the location of holes short distances and to retain the

program number where such moves are required by local

conditions or by changes in engineering plans; but new

coordinates and elevation should be established and

recorded. When explorations cover several areas, such as

alternative sites and borrow areas, a new series of numbers

should be used for each site or borrow area. The favored

practice is to begin excavation numbering of each new area

explored at an even hundred. Recent practice has been to

include the year of drilling in the hole number (i.e., DH-92-

201). 

Normally, test hole numbers are prefixed with a one-, two-,

or three-letter designation to describe the type of

exploration. The following prefix system is commonly

used.

DH Drill hole

AH Auger hole

AP Auger hole, power

TP Test pit

TT Trench

DT Dozer trench

PT Pitcher sampling hole

DN Denison sampling hole

HS Hollow-stem auger hole

CH Churn drill hole

VT Holes in which field vane tests are made

CPT Cone penetration holes

MP Pressuremeter holes

DM Dilatometer holes

BS Borehole shear test holes

SPT Standard penetration test

BPT Becker penetration test

In the above designations, DH is used to include not only

rotary drilling, but also all the methods of hole advancement

that produce core or relatively undisturbed samples, in

contrast to the AH or AP holes that produce highly

disturbed samples and CH holes that produce only cuttings

and no samples. The CH designation should be used for all

types of holes advanced by a chopping and washing action

such as wash borings, jetting, or percussion drilling. The

TP designation includes both hand- and machine-excavated

test pits. Similarly, the T designation includes open

trenches whether made by hand or machinery.

Computerized logs may require a special prefix designation.

Regardless of the prefix system used, somewhere in the data

report and on the specifications drawings, a complete

explanation of the prefix system used should be included.

c. Log Forms.&A log is a written record of data and

observations concerning materials and conditions

encountered in individual test holes and provides the

fundamental facts on which all subsequent conclusions are

based, including:

 ̆ additional exploration or testing,

 ̆ feasibility of the site,

 ̆ design treatment required,

 ̆ cost of construction,

 ̆ method of construction, 

 ̆ evaluation of structure performance.
EARTH MANUAL

190

A log may:

 ̆ represent pertinent and important information that is

used over a period of years, 

 ̆ be needed to accurately determine a change of

conditions with passage of time,

 ̆ form an important part of contract documents,

 ̆ be required as basic evidence in a court-of-law in

case of dispute.

Each log should be factual, accurate, clear, and complete.

In addition, logs can contain basic interpretations of the

geologic nature of the materials encountered. Log forms are

used to record and provide required information.

 ̆ A log should always include information on the size

of borehole and on the type of equipment used for

boring or excavating the hole. This should include:

% the kind of drilling bit used on boreholes,

% samplers used,

% a description of the penetrating equipment or

type of auger used,

% method of excavating test pits, or

% description of the machinery used.

 ̆ The location, elevation, and amount of material

collected for test pit samples should be indicated on

the logs.

 ̆ In boreholes, the length of core recovered should be

computed and expressed as a percentage of each

length of penetration of the core barrel (percent core

recovery).

 ̆ Depth from which the sample was taken should be

recorded.

 ̆ The logs should show the extent and the method of

support used as the hole is deepened such as:

% size and depth of casing,

% location and extent of grouting if used,

% type of drilling mud, 

% type of cribbing in test pits.

 ̆ Caving or squeezing material should be noted on

borehole logs as this may represent a low strength or

swelling stratum.

Various water levels should be recorded and water tests

made at pertinent intervals (i.e., the following):

 ̆ Information on the presence or absence of water

levels, and comments on the reliability of these data

should be recorded on all logs.

 ̆ The date that measurements are made should be

recorded, since water levels fluctuate seasonally.

 ̆ Water levels should be recorded periodically from the

time water is first encountered and as the test hole is

deepened.

 ̆ Upon completion of drilling, the hole should be

bailed and allowed to recover in order to obtain a true

water level measurement.

 ̆ Perched water tables and water under artesian

pressure are important to note.

 ̆ The extent of water-bearing members should be

noted, and areas where water is lost as the boring

proceeds should be reported, since subsequent work

on the hole may preclude duplicating such

information.

 ̆ The log should contain information on any water tests

made.

 ̆ Since it may be desirable to obtain periodic records

of water level fluctuations in drilled holes,

determination should be whether this is required

before plugging or backfilling, and abandoning the

exploratory hole.

 ̆ Hole completion data.

Detailed guidelines for logging exploratory holes are in the

Engineering Geology Field Manual [20]. Numerous

training manuals are available and should also be consulted

so uniformity in logging and reporting data is maintained.

These guides provide a common framework for presenting

data. Some variation in log format is possible, because the

information gathered should be tailored to project needs. A

review of current procedures is presented in the following

sections.

Examples of logs of two types of exploratory holes are

discussed below:

1. Geologic Logs of Drill Holes.&Geologic logs of

drill holes Log forms 7-1337 and 7-1334 (figs. 2-66 and

2-67), were developed for percolation and penetration

resistance testing. These forms are suitable for logging all

types of core borings which produce relatively undisturbed

samples. The forms are often modified to present

information for many other types of drilling and sampling.

Drill hole logs are also prepared using several types of

computer generated log forms. Regardless of how the form

is configured, each must have five areas for presenting

required information. The five required sections are:

 ̆ Heading block

 ̆ Left column for notes
CHAPTER 2—INVESTIGATION

191

 ̆ Center column for summary data of testing,

sampling, and lithologic information

 ̆ Right column for describing physical condition and

description of samples or material retrieved from the

hole

 ̆ Bottom section for any explanation or notes required

Examples of a percolation test log and a penetration

resistance test log are shown on figs. 2-66 and 2-67. These

figures illustrate the type of information to be included in

the log. The following outline shows the five sections of the

log:

Heading: The top portion of the log provides

space for identification information pertaining to project,

feature, hole number, location, elevation, bearing, dip,

inclination, start and completion date, and the names of

persons logging and reviewing. This information is

mandatory.

Drilling Notes Column (left column of drill log):

A. General Information

1. Purpose

2. Drill site and setup

3. Drillers

4. Drilling equipment (rig, rods, barrels, bits,

pumps, and water test equipment)

B. Procedures and Conditions

1. Drilling methods

2. General drilling conditions and drillers comments

3. Drilling fluid use, return, color, and losses

4. Caving conditions

5. Casing record

6. Sample interval comments and any unusual

occurrences during sampling

7. Cementing record

C. Hole Completion and Monitoring Data

1. Borehole survey data

2. Water level data

3. Hole completion, backfilling, and instrumentation details

4. Reason for hole termination

5. Drilling time

Summary Information (center column): As shown on

the example logs, this portion of the log is used to

summarize drilling, lithology, testing, and sampling results.

The most common tests performed are percolation tests or

penetration resistance tests for which the forms are

designed. Center column is often modified to present

results of other types of testing such as undisturbed

sampling with in-place dry density determinations and inplace testing such as vane shear or borehole shear tests.

Columns for noting core recovery, and locations and depths

of lithologic contacts aid in visualizing geologic conditions

and are included in the center portion of the log.

Information on sampling intervals should include, at least,

depths of sampling and, if space permits, graphic or tabular

information on sample measurements such as in-place dry

density. This information aids designers in selecting

samples for testing.

Comments and Explanations (bottom portion):

Notes as to abbreviations and other miscellaneous references

such as deck elevations should be shown in this area. Dates

and filenames, and dates of any revisions related to

computer data bases should be recorded.

Classification and Physical Description (right

column): An accurate description of recovered core is

provided here and includes technically sound interpretations

of nonrecovered material conditions.

 ̆ In areas of no recovery, it is frequently possible to

infer conditions based upon drilling action and

cuttings return.

 ̆ Rockbit intervals and characteristics of return

materials should be described.

 ̆ Geologic interpretations to delineate major lithologic

units are included in this column.

 ̆ Rock or soil cores or samples should be described as

completely as possible.

Soil classifications are determined using the

Unified Soil Classification System as described in USBR

5000 and 5005. Soil descriptions on test pits are discussed

immediately following this subsection. Soil classifications

and descriptions for the drill log' s right column are the same

as those for test pits, except for describing the in-place

condition which is not included for soil cores. The Unified

Soil Classification System (USCS) symbol for soil recovered

from drill holes also can be shown in tabular form in the

center column of the log.

Guidelines for logging rock cores are given in

detail in chapters 4 and 5 of the Engineering Geology Field

Manual [20]. In general, classifications include

determination of a rock unit name based on lithologic

characteristics followed by description of structural features

of engineering importance. The suggested content for word

descriptions is listed below:
EARTH MANUAL

192

Figure 2-66.—Example geologic log of a drill hole.
CHAPTER 2—INVESTIGATION

193

Figure 2-67.—Subsurface exploration—penetration resistance and log—example.
EARTH MANUAL

194

 ̆ Rock name &

 ̆ Lithologic descriptors & Such as texture, grain size

and shape, color, porosity and other physical

characteristics of importance.

 ̆ Bedding/foliation/flow texture & Such as thickness of

bedding, banding, or foliation including dip and

inclination

 ̆ Weathering/alteration & Use the standardized series

of weathering descriptors. Also, describe other

forms of alterations such as air slaking upon exposure

to air.

 ̆ Hardness & Use standardized descriptors.

 ̆ Discontinuities & Describe shears, fractures, and

contacts.

% Note attitude, spacing, and roughness of

bedding, foliation, and fractures.

% Use standardized fracture density descriptors and

characterize fracture frequency and Rock Quality

Designation (RQD).

% Describe shears and shear zones in detail,

including all matrix materials present such as

reworked material in the shear zone.

 ̆ Specific information for design. The empirical

ground support (Q and RMR) calculations and the

erodibility index utilize specialized parameters.&The

need for these parameters should be determined at the

start of explorations.

The recommended format for word descriptions (on boring

logs) is one of the main headings describing lithologic

groups, followed by indented subheadings and text

describing important features of the core. Examples of

classifications and physical descriptions for rock logging are

shown in figure 2-66.

2. Log of Test Pit or Auger Hole.&As shown in

figure 2-68, Form 7-1336-A is used for logging test pits,

auger holes, and other excavations, such as road cuts,

through surficial soils. Predominant use of this form is for

construction materials investigations and investigations for

line structures such as pipelines and canals. This form is

suitable for all types of exploratory holes which produce

complete but disturbed samples. It is used for logging auger

holes where disturbed sampling is performed following

USBR 7010. Other exploratory drill holes advanced by

rotary drilling methods are reported on drill hole logs

discussed in the previous subsection.

Detailed guidelines for logging test pits and auger holes are

available to provide consistency in data presentation.

Reclamation investigations of soils for construction require

classification and description in accordance with the USCS

as described in USBR 5000 or 5005. Guidelines for logging

test pits are given in Reclamation training manuals [70] and

in the Engineering Geology Field Manual [20]. Procedures

for obtaining disturbed samples from test pits, trenches,

accessible borings, and tunnels are given in USBR 7000.

Procedures for obtaining disturbed samples from auger

holes are given in USBR 7010.

The log form (fig. 2-68) has a heading area at the top and a

remarks area at the bottom. The body of the log form is

divided into a series of columns to include the various kinds

of information required. Columns are for: classification

group symbol; classification and description of material; and

the percentage of particles larger than 75 mm (3 in) by

volume.

Information under the heading is required. Spaces are

provided for supplying information such as project, feature,

hole number, location, elevation, dates started and

completed, and the name of the person responsible. Depth

to bedrock and to water table (free water) are important

information and should always be reported. The date when

water level was measured is very important information, as

water levels can change seasonally. When this or any other

information called for on the log cannot be obtained, the

reasons must be stated on the log or on other supporting

documents. 

In the column for classification and group symbol,

information such as group symbol, depth intervals logged,

and samples taken are recorded. The system allows for

modification of the group symbol with either prefixes or

suffixes to further describe the soil (Annex X-5, USBR

5000). An example is shown on figure 2-68. The group

symbol GW (well graded gravel) is modified by suffixes scb

which indicate that sand, cobbles, and boulders are present

to a significant extent in the sample. According to USBR

5005, the typical name for the strata is WELL GRADED

GRAVEL WITH SAND, COBBLES, AND BOULDERS.

While this system of abbreviations is useful for geologic

drawings of borrow areas and trenches, considerable

additional information is contained in the word descriptions,

and decisions should not be based on group symbols alone.

In the right column of the log, the amount of oversize

material [particles > 75 mm (3 in)] by volume is either

estimated by visual inspection or calculated by determining

the mass of the oversize. At this time, a detailed procedure

for determining the mass of oversize has not been

developed. In test pit operations, it may be advisable to

screen all material from the pit and determine oversize
CHAPTER 2—INVESTIGATION

195

Figure 2-68.—Log of test pit or auger hole—abbreviated soil classification group 

symbols for soil with cobbles and boulders.
EARTH MANUAL

196

percentages by sorting over screens or templates and

determining the mass of each size range. The procedures

used for determining oversize by mass should be included

in the construction materials or geologic reports. Once the

mass is determined, it can be converted to volume by

procedures described in USBR 7000. If oversize is

determined by mass, the volumes are reported to the nearest

percentage as shown on figure 2-68. If the volume of

oversize is estimated visually, report percentages to the

nearest 5 percent. If oversize is present, their presence is

included in the log by adding to the typical name, and the

particles are described as shown on the example of

figure 2-68.

The "Remarks" section of the log is for comments on the

overall excavation or drilling. Information includes: 

 ̆ reason for stopping,

 ̆ details on equipment used,

 ̆ details on instrumentation,

 ̆ legend for abbreviations, and 

 ̆ any miscellaneous comments.

Terminating statements similar to the following would be

considered satisfactory:

 ̆ hole eliminated due to lack of funds,

 ̆ hole caved in (include depth to cave),

 ̆ depth limited by capacity of equipment,

 ̆ hole terminated at predetermined depth,

 ̆ encountered water, and

 ̆ unable to penetrate hard material in bottom of hole.

Material should not be described as bedrock, slide material,

or similar interpretive terminology unless the exploration

actually penetrated such conditions, and samples were

collected to substantiate these conclusions. If rock is

exposed at the base of a test pit, it can be logged according

to guidelines in the Engineering Geology Field Manual.

The classification and description portion of the log can vary

depending on the type of excavation, type of testing

performed, and the materials encountered. For disturbed

soils, such as materials from power auger holes or

stockpiles, all the information is in a paragraph as follows:

 ̆ depth of strata,

 ̆ USCS classification group name,

 ̆ percentages and descriptions of the size fractions

present (gravel, sand, and fines),

 ̆ maximum particle size,

 ̆ moisture, color, and odor,

 ̆ remarks, and

 ̆ reaction with dilute solution HCl acid.

If oversize is present in the logged strata, the next paragraph

of word descriptions consists of describing the total sample

by volume. The estimated percentages are given&along

with a description of the cobbles and boulders&and the

maximum size present. Noting the presence of oversize on

test pit logs is extremely important. If only a trace or more

of oversize is present, it must be included in the typical

name. If the percentage of oversize (by volume) is less than

50 percent of the total volume, the characteristics of the

oversize are described in a separate paragraph following

description of the minus 75-mm (3-in) fraction. If the

percentage of cobbles and/or boulders, by volume, exceeds

50 percent of the total material, the characteristics of the

oversize are described in the first paragraph; the term

cobbles and/or boulders is predominant in the typical name,

and no classification symbol is assigned.

An additional paragraph is added to the word descriptions if

access is available to evaluate the in-place condition of the

soil in an undisturbed state. In this case, reporting of

moisture, color, and odor is omitted from the first paragraph

and replaced with a more detailed description in a following

paragraph. In this additional paragraph, information

includes the following items in order of presentation.

 ̆ consistency (fine grained soils only) & very soft,

soft, firm, hard, and very hard

 ̆ structure & homogeneous, stratified, blocky,

fissured, laminated, etc.

 ̆ cementation (coarse-grained soils only)

 ̆ moisture, color, and odor

 ̆ remarks

An additional example of in-place condition descriptions is

given on figure 2-69.

Careful attention must be given to reporting when and where

samples are taken and when laboratory testing was

performed. If samples are taken, it should be noted in the

left column of the log as shown on figure 2-69. A detailed

description of how the sample was taken must be added to

the word description. In many cases, disturbed sack

samples are taken by cutting a vertical strip of soil through

the interval being classified. If a sample is taken which

does not match the full interval logged, describe the exact

location of the sample. 

In cases where laboratory testing is performed for

classifying the soil, this information must be as shown on

the test pit logs. The ability for a classification to identify
CHAPTER 2—INVESTIGATION

197

Figure 2-69.—Log of test pit or auger hole—in-place conditions and sampling.
EARTH MANUAL

198

and describe soils is learned under the guidance of

experienced personnel and by systematically comparing

laboratory test results with visual classifications. On new

projects, laboratory tests are sometimes used to "calibrate"

the visual classifier when working with unfamiliar soils.

However, visual classification is based upon total material

observed and that laboratory classifications must be

performed on representative materials for comparison with

the visual information. In many cases, borrow area

investigations will have a certain proportion of laboratory

classifications to visual classification as verification.

However, on large projects, it is not economical for all the

classifications to be based solely upon results of laboratory

testing.

When the soil classification is based upon laboratory data,

this must be clearly stated and distinctly noted on the log.

Particle-size percentages are reported to the nearest

1 percent, and information on Atterberg limits, coefficients

of uniformity and curvature are reported on the test pit log.

Under the left column group symbol, the group symbols are

noted as being obtained through laboratory classification.

If laboratory classification tests are performed, and results

of visual classification are also reported on the log,

laboratory data are presented in a separate paragraph.

Figure 2-70 illustrates combined reporting of visual and

laboratory classifications. If the laboratory classification

based upon USBR 5000 differs from the visual

classification, both group symbols are shown in the left

column. Do not change the visual classification or

description, based upon laboratory data, because the visual

description is based upon a widely observed area. If the

typical name is different, this is shown in the laboratory test

data paragraph. 

In-place density tests are often performed in test pits and

trenches in borrow areas to determine shrink-swell factors.

In-place density tests are also performed in pipeline

investigations to evaluate soil support for flexible pipe. In

most cases, laboratory compaction tests (USBR 5500, 5525,

5530, and 7240) are performed depending on the material

and requirements of the investigation. The compaction tests

are used to determined relative density or percent

compaction (USBR 7250, 7255). The in-place density and

percent compaction or relative density must be reported in

the paragraph on in-place condition on the log. In-place

density tests such as the sand cone or nuclear gage normally

represent a smaller interval than the interval logged. For inplace density tests, the interval is measured or estimated and

 reported on the log.

On some features, using standard USCS group symbols and

typical names may make it difficult to distinguish materials

important to construction. For example, topsoil is normally

stripped and stockpiled in construction operations. In this

case, the log should clearly show the interpreted strata

thickness and heading for topsoil present. An example

follows:

Classification symbol Description

TOPSOIL 0.0 to 2.6 ft TOPSOIL—would be

classified as ORGANIC SOIL

(OL/OH).

About 90% fines with low plasticity,

slow dilatency, low dry strength, and

low toughness; about 10% fine to

medium sand; soft, wet, dark brown,

organic odor, roots present

throughout strata, weak reaction with

HCl.

Other material types that may be important to distinguish for

design and construction operations may be drill pad, gravel

road surfacing, mine tailings, and fill or uncompacted fill.

If a certain soil feature requires a special description for

investigations, they should be determined at the beginning

of the exploration program. The exploration team should

consider these requirements and advise investigators of the

special cases.

The USCS was developed to classify naturally occurring

soils; it was not intended for classifying lithified or

manmade materials. Problems can occur by classifying a

partially lithified material such as a weathered rock or shale

as a soil. An example would be the use of power-auger

holes in shales. If the power auger grinds up the shale into

a soil-like material, problems could arise when excavating

during construction. It is important to note that the visual

classification was performed on materials after processing.

Other materials such as claystones, processed aggregates,

and natural materials (e.g., shells) are examples of materials

where the group symbol and typical name from USCS

should not be used without careful notation. Examples of

logs for these materials are shown on figure 2-71. The

USCS typical name is enclosed within quotation marks as

the classification of material after processing.

Geologic interpretations should be made by or under the

supervision of a geologist. The geologic interpretation is

presented in a separate paragraph. An example is shown on

figure 2-68. Factual geologic data can be provided in

construction materials reports.

Large machine-dug test pits or test trenches may require

more than one log to adequately describe variation in
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199

Figure 2-70.—Log of test pit or auger hole—combined laboratory and visual classification.
EARTH MANUAL

200

Figure 2-71.—Log of test pit or auger hole—materials other than natural soils.
CHAPTER 2—INVESTIGATION

201

materials found in different portions of the pit or trench.

The initial log of such pits or trenches should describe a

vertical column of soil at the deepest part of the excavation,

usually at the center of one wall of the pit or trench. If this

one log will not adequately describe variation in the

different strata exposed by the pit or trench, additional logs

should be prepared for other locations within the test

excavation to provide a true representation of all strata

encountered in the test pit or trench. In long trenches, at

least one log should be prepared for each 15 m (50 ft) of

trench wall, regardless of uniformity of material or strata.

A geologic section of one or both walls of long test trenches

is normally required to describe variation in strata and

material between log locations. When more than one log is

needed to describe the material in an exploratory pit or

trench, coordinate location and ground surface elevation

should be noted for each point for which a log is prepared.

A plan geologic map and geologic sections should always be

prepared for test trenches that encounter bedrock in

structure foundations.

Sketches of test pit walls are useful to describe variability of

materials. Figure 2-72 shows a sketch depicting location of

the pit wall which was logged. This figure is attached to the

test pit log for reference. Additional examples can be found

in the Engineering Geology Field Manual [20].

Photographs of test pit walls are valuable inclusions in

geologic design data and construction materials reports.

2-24. Subsurface Sections.&Guidelines for

preparing geologic drawings and sections are presented in

the Engineering Geology Field Manual and Engineering

Geology Office Manual [20, 68]. These guides contain

detailed instructions for developing geologic drawings. The

five primary objectives of geologic sections are to:

 ̆ Compile and correlate surface and subsurface

geologic data.

 ̆ Present geologic interpretations.

 ̆ Save the user time by concisely and accurately

displaying pertinent geologic conditions.

 ̆ Graphically show in two or three dimensions the

subsurface conditions which cannot be determined

with ease from a geologic map, particularly those

interpretations which may be significant to

engineering planning or design.

 ̆ Indicate probable structure excavation limits and

show geotechnical considerations or treatment.

Geological sections are used to show interpreted subsurface

conditions in geological reports, materials reports, and

design data for dams, canals, and other project features.

Location of sections should be chosen so as to present

conditions described in the best possible way. Cross-valley

sections are generally more informative than a series of

sections parallel to the valley. Also, sections should cross

physical features at right angles as nearly as possible. A

clear differentiation should always be maintained between

factual and interpretive data. A system where lines range

from dotted to solid is recommended. In this system dots

represent purely hypothetical interpretation, a solid line

represents fact, and dashed lines define the degree of

reliability of intermediate data according to length of dash.

The cross section should always show the name of the

person who made the interpretation and the date the

interpretation was made.

2-25. Sampling.&Samples of soil and of rock are

collected for visual examination so that a log of the test hole

may be prepared for preservation as representative samples

in support of the descriptive log, for testing to determine

index properties, and for laboratory testing to determine

engineering properties.

Requirements for undisturbed samples are given in

USBR 7100 and 7105.

When drilling core holes, the total material recovered as

core is collected and stored in core resealable boxes. In

addition, samples of soil should be collected and placed in

sealed pint jars or resealable plastic bags to preserve the

natural water content representative of each moist or wet

stratum. Samples representative of the various types of

material found in the area under investigation should be

collected as the work progresses. Samples should be 100 to

150 mm (4 to 6 in) long and must be representative of that

material found in the area, particularly as to the degree of

alteration. If a wide variation in material quality exists,

samples representative of the ranges of the material should

be collected.

When exploring for materials in borrow areas and in

foundations where substantial quantities occur that

potentially may be used in embankment construction,

samples should be collected representative of each stratum

in a volume sufficient to provide 35 kg (75 lb) of material

passing a 4.75-mm (No. 4) sieve to be used for testing for

engineering properties. Only material larger than 75 mm

(3 in) should be removed from a sample, and the percentage

of plus 75 mm removed should be reported. However, in

some cases, larger samples are required for tests on total

material. If the entire test hole appears to be in uniform

material, samples from the upper, middle, and lower onethird of the test hole should be collected. USBR 5205

should be referred to for size of sample required for a

particular test.
EARTH MANUAL

202

Figure 2-72.—Geologic interpretation in test pit (geologic profile).

When investigating riprap sources, samples consisting of

three or four pieces of rock totaling at least 275 kg (600 lb)

representative of the source should be collected. Collecting

samples of concrete aggregates is covered in the Concrete

Manual [20]. Collecting samples of blanketing material,

filter material, and ballast should conform to requirements

for collection of borrow material for embankment

construction.

From the set(s) of samples collected described above,

samples are selected for performing index and engineering

properties tests. Care should be taken to preserve sufficient

samples to substantiate logs of exploratory holes and for

representative samples to be transmitted.

Samples collected in the process of routine exploration

generally are not satisfactory for testing associated with

determining properties of in-place soil or rock. For this

purpose, samples of material unaffected by seasonal climatic

influence are collected from large-diameter boreholes [100

to 150 mm (4 to 6 in) in diameter minimum] or from the

bottom of open pits. Borehole samples should be 300 to

600 mm (12 to 24 in) long, and open-pit samples 250- to

450-mm (10- to 18-in) cubes. Every effort should be made

to preserve such samples in as nearly an in-place natural

condition as possible. Procedures for collecting and

preserving this type sample are described in USBR 7100 and

7105.

2-26. Reports.&

a. General.&Guidelines for preparing geologic design

data reports are presented in the Engineering Geology Office

Manual [69]. This guide contains detailed instructions

concerning required information for inclusion in geologic

design data reports.

The results of every investigation should be presented in a

report. In the reconnaissance stage for a small structure, a

letter report describing in general terms the nature of

problems associated with the investigation, the extent of the

investigation, and the conclusions reached may suffice. As

an investigation proceeds, additional data are collected and

evaluated. As the various stages of investigation proceed,
CHAPTER 2—INVESTIGATION

203

previously assembled material is incorporated in a progress

report. During preparation of this progress report, previous

reports should be examined; those questions which have

been answered should be noted in the report together with

the resolution or, if unanswered, should be carried over for

future consideration. The final report should either answer

all questions raised in the past or discuss why a positive

solution cannot be reached within the scope of an

investigation.

Every investigation should contain:

 ̆ A statement of the purpose of the investigation

 ̆ The stage for which the report is being prepared

 ̆ The kind of structure contemplated or the type of

study

 ̆ The principal dimensions of the structure

The following features pertaining to foundations and

earthwork should be included in all reports.

b. Foundations and Earthwork.&Foundation data

should reflect recognition and consideration of the type and

size of the particular engineering structure and the effect on,

or relationship to, the structure of the significant

characteristics of foundation materials and conditions at the

particular site.

The general regional geology should be described. The

description should include major geological features, names

of formations found in the area, their age, their relationship

to one another, their general physical characteristics, and

seismicity.

 ̆ A description and interpretation of local geology

should include:

% physical quality and geologic structure of

foundation strata,

% groundwater and seismic conditions,

% existing and potential slide areas, and

% engineering geologic interpretations appropriate

to the engineering structure involved.

 ̆ Geologic logs of all subsurface explorations should

be included in the report. 

 ̆ Combine geologic map plotted on the topographic

map of the site showing surface geology and the

location of geologic sections and explorations.

 ̆ Supplement the above map by geologic sections

showing known and interpreted geologic conditions

related to engineering structures.

 ̆ Photograph pertinent geologic and topographic

features of the terrain, including aerial photographs

for mosaics, if available, are valuable additions to the

report.

Engineering data on overburden soils within the foundation

of the proposed structure should be shown by detailed soil

profiles and reported as follows:

 ̆ A classification of the soil in each major stratum

according to the Unified Soil Classification System.

 ̆ A description of the undisturbed state of the soil in

each stratum.

 ̆ A delineation of the lateral extent and thickness of

critical, competent, poor, or potentially unstable

strata.

 ̆ An estimate, or a determination by tests, of the

significant engineering properties of the strata such as

density, permeability, shear strength, and

compressibility or expansion characteristics; and the

effect of structure load, changes in water content, and

fluctuations or permanent rise of ground water on

these properties.

 ̆ An estimate or a determination of the corrosive

properties and sulphate content of the soil and ground

water as affecting the choice of cement for use in

structures.

For data on bedrock, the following are required:

 ̆ A description of the depth to and contour of bedrock,

thickness of weathered, altered, or otherwise softened

zones, and other structural weaknesses and

discontinuities.

 ̆ A delineation of structurally weak, pervious, and

potentially unstable zones and strata of soft rock

and/or soil.

 ̆ An estimate or a determination of the significant

engineering properties of bedrock such as density,

absorption, permeability, shear strength, stress, and

strain characteristics; and the effect of structure load,

changes in water content, and fluctuations or

permanent rise of groundwater on these properties.

c. Construction Materials Data.&As part of the

design data for earth dams, an earth materials report is

required containing a list of:

 ̆ available impermeable soils,

 ̆ permeable soils,

 ̆ sand for filters, and 

 ̆ rock for riprap and rockfill.
EARTH MANUAL

204

Occasionally, a list is required for canals and other large

structures when appreciable quantities of these materials are

required. Sometimes, similar reports for smaller quantities

of special materials are needed. The principal items to be

covered in the earth materials report are:

 ̆ A grid map showing the topography of the deposit

and of the structure site and the intervening terrain if

within a radius of 3.2 km (2 mi). The location of test

holes and trenches should be shown using standard

symbols.

 ̆ Ownership of deposit.

 ̆ Brief description of topography and vegetation.

 ̆ Estimated thickness of the deposit, including

variations. Drawings showing subsurface profiles

along grid lines should be included.

 ̆ Areal extent of the deposit.

 ̆ Estimated quantity of the deposit.

 ̆ Type and thickness of overburden.

 ̆ Depth to water.

 ̆ Accessibility to the source.

 ̆ General description of rock.

 ̆ Amount of jointing and thickness of bedding of rock

strata.

 ̆ Spacing, shape, angularity, average size, and range

of sizes of natural boulder deposits.

 ̆ Brief description of shape and angularity of rock

fragments found on slopes and of the manner and

sizes into which the rock breaks when blasted.

 ̆ Logs of all auger test holes and exposed faces of test

trenches or pits.

 ̆ An estimate, or determination by tests, of the

pertinent index and engineering properties of soils

encountered. The amount of testing should be

limited in the feasibility stage but should be more

detailed for specifications.

 ̆ Photographs, maps, and other drawings are helpful

and desirable for the record of explorations.

In most cases, information gathered for the earth materials

report of an earth dam, for final design and specifications,

may not be of sufficient detail to permit development of a

plan for using available earth materials to the

best 

advantage. However, explorations should be sufficient to

assure that sufficient materials required are available. As

soon as funds are available for constructing the dam,

additional studies can be performed.

The primary purposes of a detailed study are to determine

the depth of borrow pit cuts, the most efficient distribution

of materials to be placed in the embankment, and the need

for addition or removal of moisture. In most cases, it is

desirable to add moisture to dry, impervious borrow

materials before excavating. Studies should include an

analysis of moisture conditions in each borrow area from

which plans may be developed for irrigating the areas. If

materials in borrow areas are too wet for proper placement,

plans for draining these areas may be based upon results of

detailed studies. Seasonal variations of water content,

variation of water content with depth, and rate of water

penetration are items requiring consideration.

Detailed investigations are also desirable for canals and

structures where large quantities of required excavations and

borrow are involved. In any case, sufficient preconstruction

explorations should be made to know where specified types

of materials are to be obtained and where all materials are to

be placed.

Information on concrete aggregates should be reported

according to instructions in the Concrete Manual [20].

Information on sources and character of acceptable road surfacing materials, if required, should be given in the

construction materials report. Reference should be made to

results of sampling and analysis of materials, including

previous tests. Figures 2-73 and 2-74 are example forms for

summarizing field and laboratory tests on embankment

materials which accompany preconstruction reports.
CHAPTER 2—INVESTIGATION

205

Figure 2-74.—Summary of field and laboratory tests for embankment materials report—

permeable-type materials. 

Figure 2-73.—Summary of field and laboratory tests for embankment materials report—

impermeable-type materials. 
EARTH MANUAL

206

BIBLIOGRAPHY

[1] U.S. Geological Survey, Indexes and Catalogs to

Topographic and Other Map Coverage, 23 pp., Denver,

Colorado, 1993.

[2] U.S. Geological Survey, Publications of the

U.S. Geological Survey, 117 pp. Denver, Colorado, 1992.

[3] Dodd, K., H.K. Fuller, and P.F. Clarke, Guide to

Obtaining USGS Information: U.S. Geological Survey

Circular 900, 34 pp. 1989.

[4] Ray, R.G., Aerial Photographs in Geologic

Interpretation and Mapping: U.S. Geological Survey

Professional Paper 373, 230 pp. 1906.

[5] U.S. Geological Survey, Interpreting Geologic Maps

for Engineering Purposes, Hollidayburg Quadrangle,

Pennsylvania: U.S. Geological Survey Special Map,

6 sheets, 1:62,500 scale. 1953.

[6] Varnes, D.J., The Logic of Geologic Maps, With

Reference to Their Interpretation and Use for Engineering

Purposes: U.S. Geological Survey Professional Paper 837,

48 pp. 1974.

[7] U.S. Geological Survey, USGS Open-File Report 89-

681, 78 pp., Denver, Colorado, June 1989.

[8] Natural Resources Conservation Service, Soil

Taxonomy, USDA Agricultural Handbook No. 18. U.S.

Department of Agriculture.

[9] Natural Resources Conservation Service, Soil Survey

Manual, U.S. Department of Agriculture Handbook No. 18,

p. 473, 1951, rev. in press.

[10] Sabins, F.F., Remote Sensing & Principles and

Interpretation, 2d ed., Freeman, New York, New York,

449 pp., 1987.

[11] Siegal, B.S., and A.R. Gillespie, eds., Remote

Sensing in Geology, 702 pp., Wiley & Sons, New York,

New York, 1980.

[12] Colwell, R.N., ed., Manual of Remote Sensing,

2d ed., Falls Church VA, American Society of

Photogrammetry, 2,724 pp., 1983.

[13] Clevenger, W.A., Engineering Properties of Loessial

Soils, Bureau of Reclamation Report, EM-426, Denver,

Colorado, June 1955.

[14] Gibbs, H.J., Summary of Research Studies on Loess

for Use as Foundations and Construction Material, Bureau

of Reclamation Report No. EM-424, Denver, Colorado,

July 1955.

[15] Holtz, W.G., and J.W. Hilf, Settlement of Soil

Foundations Due to Saturation, Bureau of Reclamation

Report No. EM-636, Denver, Colorado, September 1961.

[16] Bureau of Reclamation, Design of Small Dams,

3d ed., 535 pp., Denver, Colorado, 1987.

[17] Bureau of Reclamation, Concrete Manual, 8th ed.,

rev. rep., 627 pp. Denver, Colorado, 1981.

[18] Bureau of Reclamation, "Protective Filters," Design

Standards No. 13&Embankment Dams, Ch. 5, 20 pp.,

Denver, Colorado, May 1987.

[19] Farrar, J.A., "Bureau of Reclamation Experience in

Testing of Riprap for Erosion Control of Embankment

Dams," Rock for Erosion Control, ASTM STP 1177, Charles

H. McElroy and David A. Lienhart, eds., American Society

for Testing and Materials, West Conshohocken,

Pennsylvania, 1993.

[20] Bureau of Reclamation, Engineering Geology Field

Manual, Vol. 1, Denver, Colorado, 1998.

[21] Bureau of Reclamation, Blasting Review Team

Report, 47 pp., rev. February 1980, Denver Colorado.

[22] American Society for Testing and Materials, ASTM

Annual Book of Standards, 04.09, West Conshohocken,

Pennsylvania, 1996.

[23] Holtz, W.G., and F.C. Walker, "Soil-Cement as

Slope Protection for Earth Dams," Journal of the Soil

Mechanics and Foundations Division, ASCE, vol. 88,

No. SM6, pp. 107-134, 1962.

[24] Davis, F.J., E.W. Gray, Jr., and C.W. Jones, The

Use of Soil-Cement for Slope Protection, Eleventh Congress

on Large Dams, Madrid, pp. 237-255, 1973.
CHAPTER 2—INVESTIGATION

207

[25] DeGroot, G., Soil-Cement Protection on Bureau of

Reclamation Features, Bureau of Reclamation Report RECERC-71-20, 104 pp., Denver, Colorado, 1971.

[26] Howard, A., Soil-Cement Slurry Pipe Bedding,

ACI Meeting on Controlled Low-Strength Materials,"

Washington, DC, March 1992.

[27] Howard, A.K., Pipe Bedding and Backfill,

Geotechnical Training Manual No. 7, Bureau of

Reclamation, Denver, Colorado, 1996.

[28] Howard, A.K., and J.P. Bara, Lime Stabilization

on Friant-Kern Canal, Bureau of Reclamation Report, RECERC-76-20, 53 pp., Denver, Colorado, December 1976.

[29] Knodel, P.C., Lime in Canal and Dam

Stabilization, Bureau of Reclamation Report No. GR-87-10,

14 pp., Denver, Colorado, June 1987.

[30] Shuter, E., and W.E. Teasdale, Application of

Drilling, Coring, and Sampling Techniques to Test Holes

and Wells, U.S. Geological Survey Report, TWRI 2-FI,

Denver, Colorado, 1989.

[31] Gibbs, H.J., Double-Tube Auger, Bureau of

Reclamation Report, EM-770, 31 pp., Denver, Colorado,

July 1969.

[32] International Drilling Federation, DCDMA

Technical Manual, Columbia, South Carolina, 1991.

[33] Bureau of Reclamation, Earth Manual, 2d ed.,

810 pp., Denver, Colorado, 1974.

[34] Ruda, T.C., and P.J. Bossher, Drillers Handbook,

National Drilling Contractors Association, Columbia South

Carolina, June 1990.

[35] Cumming, J.D., and A.P. Wicklund, Diamond

Drill Handbook, J.K. Smit, Toronto, Canada, 3d ed.,

rep.,1980.

[36] Heintz, W.F., Diamond Drilling Handbook,

1st ed., South African Drilling Association, Johannesberg,

South Africa, 1985.

[37] Bureau of Reclamation, Concrete Manual, Part 2,

9th ed., 900 pp., Denver, Colorado, 1992.

[38] Marcuson, W.F., and A.G. Franklin, State of the

Art of Undisturbed Sampling of Cohesionless Soils,

Miscellaneous Paper GL-79-16, U.S. Army Engineer

Waterways Experiment Station Geotechnical Laboratory,

Office, Chief of Engineers, Washington, DC, July 1979.

[39] Bureau of Mines, Core Recovery Techniques for

Soft or Poorly Consolidated Materials, final report prepared

by Woodward Clyde Consultants, Contract No. JO275003,

April 28, 1978.

[40] Casias, T.J., Results of Research in Sampling

Loessial Soil for Inplace Unit Weight Determinations,

Bureau of Reclamation Report REC-ERC-87-5, 37 pp.,

Denver, Colorado, June 1987.

[41] Electric Power Research Institute, Guidelines for

Drilling and Testing Core Samples at Concrete Gravity

Dams, Report EPRI GS-6365, Project 2917-5, Palo Alto,

California, May 1989.

[42] Acker, W.L., Basic Procedure for Soil Sampling

and Core Drilling, Acker Drill Co., Inc., Scranton

Pennsylvania, 1974.

[43] U.S. Environmental Protection Agency, A

Compendium of Superfund Field Operations Methods, EPA

540/P87/001, NTIS pb88-181557, Office of Emergency and

Remedial Response, Washington, DC, December 1987.

[44] U.S. Environmental Protection Agency,

Geophysics Expert System Advisor, EPA-600/4-89/023,

Environmental Monitoring Systems Laboratory, Las Vegas,

Nevada, June 1989.

[45] Hunt, Roy E., "Geotechnical Engineering

Investigation Manual," Geotechnical Engineering, pp. 47-

66, McGraw-Hill, Inc., 1984.

[46] Legget, Robert F., and Paul F. Karrow, Handbook

of Geology in Civil Engineering, McGraw-Hill, Inc.,

pp. 12-1 to 12-22, 1983.

[47] Bureau of Reclamation, Groundwater Manual,

2nd ed., 661 pp., Denver, Colorado, 1995.

[48] Seed, H.B., K. Tokimatsu, L.F. Harder, and

R.M. Chung, Influence of SPT Procedures in Soil

Liquefaction Resistance Evaluations, Earthquake

Engineering Research Center Report, UCB/EERC/84/15,

50 pp., University of California at Berkeley, October 1984.
EARTH MANUAL

208

[49] Marcuson, W.F., and A.G. Franklin, State of the

Art of Undisturbed Sampling of Cohesionless Soils,

Miscellaneous Paper GL-79-16, U.S. Army Engineer

Waterways Experiment Station Geotechnical Laboratory

Office, Chief of Engineers, Washington, DC, July 1979.

[50] Anderson, L.G., "A Modern Approach to

Overburden Drilling," Western Miner, vol. 41, No. 11,

pp. 22-26, November 1982.

[51] Morrison, K.I. and B.D. Watts, Soil Modulus

Friction and Base Resistance From Simple Pile Load Tests

on End-Bearing Piles, 38th Canadian Geotechnical

Conference, pp. 273-281, Edmonton, Alberta, 1985.

[52] Harder, Jr., L.F. and H.B. Seed, Determination of

Penetration Resistance for Course Grained Soils Using

Becker Hammer Drill, Report No. UCB/EERC-86106,

Earthquake Engineering Research Center, University of

California, Berkeley, California, 1986.

[53] Harder, Jr., L.F., "Investigations of Mackay Dam

Following the 1983 Bora Peak Earthquake," Stability and

Performance of Slopes and Embankments II, ASCE

Geotechnical Special Publication No. 31, 2:956-972, 1992.

[54] Sykora, D.W., J.P. Koester, R.E. Wahl, and M.E.

Haynes, "Post-Earthquake Slope Stability of Two Dams

With Liquefied Gravel Foundations," Stability and

Performance of Slopes and Embankments II, ASCE

Geotechnical Special Publication No. 31, 2:990-1005, 1992.

[55] Sy, A., and R.G. Campanalla, Dynamic

Performance of the Becker Hammer Drill and Penetration

Test, 45th Canadian Geotechnical Conference, paper 24, pp.

1-10, Toronto, Ontario, 1992.

[56] Schmertmann, J.H., Guidelines for Cone

Penetration Test, Performance and Design, Federal

Highway Administration, Report, FHWA-TS-78-209,

145 pp., Washington, DC, July 1978.

[57] Robertson, P.K., and R.G. Campanella, Guidelines

for Using the CPT, CPTU, and Marchetti DMT for

Geotechnical Design, vol. 2, "Using CPT and CPTU Data,"

Federal Highway Administration, Report FHWA-PA-87-

023+ 84-24, pp. 235, NTIS PB88-21164, Washington, DC,

March 1988.

[58] Baguelin, F., J.F. Jezequel, and D.H. Shields, The

Pressuremeter and Foundation Engineering, Trans Tech

Publications, Clausthal, 1978.

[59] American Society for Testing Materials: "Standard

Test Method for Pressuremeter Testing in Soils," Annual

Book of Standards, vol. 04.08, D4719-87, West

Conshohocken, Pennsylvania, 1992.

[60] Jamiolkowski, M., C.G. Ladd, J.T. Germaine, and

R. Lancellotta, "New Developments in Field and Laboratory

Testing of Soils," Proceedings, 11th International

Conference on Soil Mechanics and Foundation Engineering,

vol. 1, San Francisco, pp. 57-153, 1985.

[61] Wineland, J.D., "Borehold Shear Device,"

Proceedings, American Society of Civil Engineers Specialty

Conference on In-Situ Measurement of Soil Properties, vol.

1, Raleigh, pp. 511-522, 1975.

[62] Handy, R.L., J.M. Pitt, L.E. Engle, and D.E. Pitt,

Rock Borehole Shear Test, paper presented at the

17th Symposium on Rock Mechanics, Rep. ERI-77026,

Engineering Research Institute, Iowa State University,

Paper 4B, 11 pp., August 1976.

[63] Marchetti, S., "In-Situ Tests by Flat Dilatometer,"

Journal of Geotechnical Engineering Division, ASCE,

vol. 106, No. GT3, pp. 299-321, March 1980.

[64] Schmertmann, J., "The New Marchetti Dilatometer

Test," Geotechnical News, vol. 2, No. 3, pp. 34-35,

September-November 1984.

[65] Schmertmann J., Guidelines for Using the CPT,

CPTU and Marchetti DMT for Geotechnical Design, vol. 3,

"DMT Test Method and Data Reduction," Federal Highway

Administration, Report, FHWA-PA-87-023+ 84-24, NTIS

PB88-21164, Washington, DC, February 1988.

[66] Haverland, M.L., and E.J. Slebir, Methods of

Performing and Interpreting In Situ Shear Tests, preprint of

paper prepared for 13th Symposium on Rock Mechanics,

University of Illinois Urbana-Champaign, Bureau of

Reclamation, Denver, Colorado, August 30-September 1,

1971.

[67] Wallace, G.B., E.J. Slebir, and F.A. Anderson,

Radial Jacking Test for Arch Dams, preprint of paper

presented at the 10th Rock Mechanics Symposium,

University of Texas, Austin, Texas, May 20-22, 1968,

Bureau of Reclamation,
CHAPTER 2—INVESTIGATION

209

[68] Wallace, G.B., E.J. Slebir, and F.A. Anderson,

"In situ Methods for Determining Deformation Modulus

Used by the Bureau of Reclamation," Field Testing and

Instrumentation of Rock, ASTM STP 554, American Society

for Testing and Materials, 1974.

[69] Bureau of Reclamation, Engineering Geology Office

Manual, 58 pp., Denver, Colorado, April 1988.

[70] Bureau of Reclamation, Soil Classification

Handbook, Geotechnical Branch Training Manual No. 6,

106 pp., Denver, Colorado, January 1986.
211

Chapter 3

CONTROL OF EARTH CONSTRUCTION

A. Principles of Construction Control

3-1. General.&In many types of engineering work,

structural materials are manufactured to obtain certain

characteristics; their use is prescribed by building codes,

handbooks, and codes of practice established by various

engineering organizations. However, for earth construction,

the common practice is to use material that is available

locally rather than specifying that a particular type of

material of specific properties be secured. Likewise, a

variety of procedures exists by which earth materials may be

satisfactorily incorporated into a structure. When earth is

the construction material, personnel in charge of construction

control must become familiar with design requirements and

must verify that the finished product meets the requirements.

Design of earth works must allow for an inherent range of

earth material properties. For maximum economy, tolerance

ranges will vary according to available materials, conditions

of use, and anticipated methods of construction. A closer

relationship is required among the operations of inspection,

design, and construction for earthwork than is needed in

other engineering disciplines. Construction control of

earthwork involves not only practices similar to those

normally required for structures using manufactured

materials, but also the supervision and inspection normally

performed at the manufacturing plant. In earthwork

construction, the processes by which an acceptable material

is produced are performed in the field.

Structures designed by the Bureau of Reclamation

(Reclamation) are usually built by a contractor. The basis of

the contract is a set of specifications that has a schedule of

items of work. Through information provided in

specifications, the contractor proposes prices for performing

the items of work that, when accepted, become a part of the

agreement between the Government and the contractor. The

primary functions of the construction control organization are

to: 

 ̆ Ensure the structure is built according to

specifications.

 ̆ Report and document any changed conditions.

 ̆ Certify to what extent the items of work have been

completed.

 ̆ Test for compliance with requirements.

 ̆ Determine payment due the contractor.

Although the Government prepares plans and specifications

defining work to be performed, once a contract is signed, the

Government representatives have no right to change contract

requirements, and the contractor has no right to change unit

prices. A condition may exist in the field that is different

from what was anticipated to exist during preparation of the

specifications. If changes to designs are necessary, a

contract modification is agreed upon by both the contractor

and the contracting officer.

Specifications requirements for earthwork construction may

be grouped into two types: those requirements based on

performance and those requirements based on procedures.

This distinction must be clearly recognized. The requirement

for earthfill in a dam embankment is usually based on both a

minimum procedure and on performance. If the two

requirements prove to be incompatible, the performance is

adjusted to obtain compatibility. The desirability of a

performance-type requirement is recognized; however, the

present state of knowledge of soil behavior, the complexity

of specifications required, and the extensive testing

requirement make this type of specification very expensive

for some types of noncritical earthwork construction.

When developing specifications, it is very important to

include the assumptions, confidence, and uncertainties

inherent in the design. This allows both the contractor and

contract administration personnel a clearer understanding of

the expectations of the designer and the inherent risks

involved in the contract. It has been Reclamation practice to

make all existing data available to bidders either by

incorporation of the data into specifications or by referencing

reports and making them available for review. In the past,

it was Reclamation’s practice to develop a separate document

called "construction considerations" which included the

designers’ assumptions, uncertainties, and requirements for

successful construction. Reclamation has recently attempted

to include some of these considerations directly in the

specifications. An example would be to include the

reasoning for excavations shown on certain levels in the

foundation. Acceptable foundation conditions should be

given along with the reasoning and the geologic

interpretations providing the basis for the excavation limits.

Also, Reclamation gives prebid briefings to prospective
EARTH MANUAL

212

contractors. During these briefings, it is helpful to show a

video of preconstruction excavations or to actually perform

excavations such as test pitting for the prospective bidders.

Often, Reclamation performs rather extensive design

investigations; however, they are performed to collect design

data and may not be related to constructability. Given the

nature of the earth and its complex geology, it is not

economical to attempt to perform extensive investigations to

alleviate any change of condition. Contractors are

encouraged to perform prebid investigations and

investigations as construction progresses, as necessary, to

avoid surprises during construction. 

Specifications requirements also may be divided into two

groups: definite requirements and those qualified by the

phrase "as directed." The undesirability of the latter

requirement is recognized and is avoided whenever possible.

However, the "as directed" type of requirement is used in

establishing minor dimensions in areas where investigations

sufficient to establish such dimensions are not justified and

when new conditions are encountered for which requirements

have not been established.

Where the "as directed" requirement refers to dimensioning,

either maximum and minimum dimensions or an average

dimension is noted on the design drawings. If maximum and

minimum dimensions are stated, the usual practice is to

excavate to the minimum dimension; and where visual

examination indicates the excavation is still within inferior

material, excavation up to the maximum dimension is

continued, if required, to reach a satisfactory foundation.

Where the "as directed" requirement refers to a new

condition, the contractor and construction engineer should

exercise joint effort to establish practical performance limits

or to establish procedures that will produce satisfactory

results where performance cannot readily be defined. Some

experimentation is desirable, but this aspect should be small

compared to the total requirement.

3-2. Inspection.&The adequacy of construction is

determined by visual examination, by measurements, and by

testing. Inspection determines whether the requirements of

plans and specifications are being satisfied; it does not

determine what the requirements should be. An inspector

must become familiar with the specified requirements for

work to be inspected. In determining whether work satisfies

the requirements, an inspector should also be familiar with

how the requirement is defined. For earthwork construction,

dimensional requirements and quality requirements are

evaluated. A requirement may be defined as a condition to

be achieved from which certain deviations (plus or minus)

are tolerable, or it may be defined as a limiting condition

from which deviation is allowable in only one specified

direction. Both methods are in common use. Although a

procedure is specified for some types of work (notably,

earthfill in dam embankments), inspection may be made on

the basis of satisfying a performance requirement. Basically,

inspection determines only whether work is acceptable or not

acceptable, but it also is desirable to determine the extent to

which work is acceptable or unacceptable.

An inspector should be familiar with the various safety and

health regulations for construction activities. Inspectors

should stay fully informed on progress of work and on future

programmed work.

To facilitate construction control, relationships between

engineering properties test results and index test results are

established wherever possible. In addition, visual

observations of soil characteristics are correlated with both

index and engineering properties. When noticeable

differences exist between acceptable and unacceptable work

or materials, sufficient testing is required to confirm that

differences persist. As these differences become less

obvious, the amount of testing should be increased. In any

event, testing should be sufficient to provide adequate quality

control and to furnish the necessary permanent records.

It is impractical to completely test all the work performed.

The usual procedure is to select samples of work or materials

for testing that are representative of some unit of work or

material. Accuracy of such procedures depends on:

 ̆ the relationship of sample size to size of unit it

represents,

 ̆ procedures used for sample selection, and

 ̆ frequency of sampling.

For most earthwork construction performed for Reclamation,

the ratio of sample size to unit of work or material

represented is small, so special sample selection procedures

are used. Since the principal objective is to ensure adequate

work, samples are selected at random with a minimum

recommended frequency.

3-3. Field Laboratory Facilities.&The primary

purpose of a field laboratory is to perform testing of

construction materials. Test data serve as bases for

determining and ensuring compliance with specifications, for

securing maximum benefit from materials being used, and

for providing a record of materials placed. Physical
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

213

properties testing of earth materials during investigation

stages may be performed in the field laboratory or in the

Denver Office laboratories&or a combination used.

The size and type of field laboratory are dependent on

magnitude of the job and on types of structures. When a

laboratory building needs to be constructed, requirements

usually will conform to one of the designs shown on figure 3-

1 or a suitable modification. The Type C arrangement

shown on figure 3-1 is appropriate for major earthwork

projects. This design was used for Palisades Dam, Idaho,

which contains about 10.7 million m3

 (14 million yd3) of

embankment and 115,000 m3

 (150,000 yd3) of concrete. It

was used at Trinity Dam, California, which has about 23

million m3

 (30 million yd3) of earth embankment and

76,500 m3

 (100,000 yd3) of concrete. The laboratory shown

on figure 3-1 as Type B is applicable for projects where

facilities are required for both earth and concrete testing of

moderate scale. This type laboratory was used at Heart Butte

Dam, North Dakota, which has about 1,070,000 m3

(1.4 million yd3) of earthwork and 7,600 m3 (10,000 yd3) of

concrete. The small mobile or stationary laboratories shown

as Type A on figure 3-1 are suitable for small projects, as a

satellite laboratory on a large earthwork project, or on

projects divided into several work divisions. They may be

truck-mounted or trailer units. An example of a mobile

laboratory is shown on figure 3-2.

At times, the type of laboratory suitable for a particular job

may be difficult to determine. The main factors in

determining the size and number of laboratories are size of

contemplated work, concentration of work, and complexity

of materials to be tested. In most cases, concrete and earth

materials testing are combined into the same building.

However, for small satellite control laboratories, separate

facilities for earthwork control may be desirable. When

earthwork is concentrated at one location&as for a dam&the

project laboratory can be erected near the worksite so that

laboratory facilities are immediately available for necessary

control work. When earthwork is spread out over long

distances, as in the cases of canal and road construction,

testing facilities in addition to those at the main project

laboratory must be provided near the work. Some projects

employ a utility-type vehicle or an equivalent equipped with

the necessary testing equipment as shown in figure 3-2.

Other projects have used small skid-mounted buildings. As

work progresses, these buildings are towed or hauled to new

locations. Other projects have used large portable boxes

where equipment can be stored. For testing work in very

dry or rainy weather, sheltered facilities are advantageous so

soil tests can be made without objectionable soil moisture

changes.

To ensure acceptable accuracy of test results, not only must

equipment be maintained to a known accuracy, but the

laboratory testing environment requires efficient control.

Laboratory areas, where permeability and hydrometer

analyses are performed, should be maintained at a

comfortable, uniform temperature with a variation in

temperature not to exceed ± 3 (C (± 5 (F); otherwise, test

results may be erratic and questionable. Usually, the most

satisfactory method of temperature control is a central forced

air system where air is heated or cooled (as required),

filtered to remove dust, and returned through ducts to the

various parts of the laboratory. Laboratory areas receiving

heat from other sources such as concentrated sunlight,

radiators, ovens, or hotplates should be avoided for tests

where temperature change would adversely affect test results.

For example, a hydrometer analysis would be adversely

affected by a heating radiator if a constant temperature water

bath is not used.

Some types of balances are sensitive to air currents. These

balances must be either properly shielded or located in areas

where air currents (from the heating or ventilating system) do

not interfere with their proper operation. If possible, a high

relative humidity should be maintained in areas where

undisturbed soil samples are stored. 

Operations that produce dust, such as sieving, processing, or

pulverizing, should be conducted in an area separate from the

main laboratory; an adequate system should be provided for

removing dust from the atmosphere either by filtration or

exhausting to the outside. Noisy operations such as sieving,

compacting, and maximum index density testing should be

conducted in rooms separate from the main laboratory

because of their adverse effect on personnel and on other

laboratory operations. When exposed to noise levels above

85 decibels for over 15 minutes per day, proper hearing

protection must be worn. This noise level is commonly

attained during the sieving of soils containing gravel.

3-4. Laboratory Data.&Data forms generated in daily

operations of field laboratories are important technical and

legal documents; they must be properly handled and

processed as described in USBR 9300: Checking, Rounding,

and Reporting of Laboratory Data. 1

 Following correct

procedures produces uniformity and consistency in data

reporting.

1

 9300: Checking, Rounding, and Reporting of Laboratory Data.
EARTH MANUAL

214

Figure 3-1.—Examples of floor plans for field control laboratories.
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

215

b. Type V laboratory—vehicle equipped for on-site 

earthwork control tests.

a. Semimobile trailer unit used as a field laboratory.

Figure 3-2.—Typical field laboratories.
EARTH MANUAL

216

Proper data recording means not only writing a measured or

calculated number in the correct location&with the

appropriate number of digits&but also completing the test

identification information on each data form. Observations

made during the test that might have an effect on test results

must be noted. Erasures are not allowed on data forms. If

a value has been erroneously recorded or calculated, a line

is drawn through the incorrect number, and the correct value

is written above or next to the original value.

All data calculated or transferred from another source must

be checked; the checkmarks are shown on the form. It is

important that the one who checks data uses the same steps

or method of computation as the original data reporter.

Numbers calculated by "chain" computations (with a

calculator or computer) may result in different values than

those obtained when values are rounded for each entry and

the rounded value is used in subsequent calculations.

When a numerical value is to be rounded to fewer digits than

the total existing digits, rounding should be done as follows:

When the first digit

dropped is:

The last digit

retained is:

Examples of

rounded numbers:

< 5

> 5

exactly 5

5 followed only by zeros

unchanged

increased by 1

increased by 1

increased by 1

2.44 to 2.4

2.46 to 2.5

2.55 to 2.6

2.5500 to 2.6

The same policy (rules) applies when rounding a number

with many digits to a number with few digits. A computer

or calculator may display the answer to a computation as 10

digits, and the answer is to be recorded to 2 digits. For

example, the number 2.3456789 would be rounded to 2.3;

the first digit dropped would be the 4; other examples are:

2.49999 to 2.5

2.49999 to 2

2.55555 to 2.56

2.55555 to 3

2.50000 to 3

The above examples of exactly 5 or 5 followed by zeros are

rounded differently than indicated in some references.

These references indicate the number is to be rounded to the

closest even number. That is, 2.50000 would be rounded to

2 and not 3. Unfortunately, calculators and computers do

not follow this rule and always round up. Recognizing the

universal use of calculators and computers, the policy as

stated should be followed.

Data sheets, equipment literature, and calibration records

must be filed for easy and ready retrieval any time during

construction.

3-5. Reports.&A record of construction operations

should be maintained as they are indispensable when repair

or modification of the structure is required in the future.

Also, a record is necessary when claims are made by either

the contractor or the Government that work required or

performed was not according to the contract. Recorded data

are beneficial in improving engineering knowledge and

practices for future work. Basic documents of the

construction record are:

 ̆ Plans and specifications

 ̆ Adopted modifications that were considered to come

within the terms of the contract

 ̆ Amendments made to the contract as extra work

orders

 ̆ Orders for work changes

 ̆ Contractual protests

 ̆ Results of:

% tests,

- measurements of work performed, and

% contract earnings.

To ensure that a proper record of construction is developed

and available, various periodic reports are required. By

reviewing these reports, supervisory personnel can

determine whether proper performance is being achieved or

whether deficiencies or misunderstandings exist. Necessary

corrections can be made quickly on the basis of such

reports. The progress report permits coordination of

various operations required for servicing a contract to be

performed in a timely and efficient manner.

The amount of reporting required varies according to

function and degree of supervision.

 ̆ Reports are made of every test performed in the

laboratory and in the field.

 ̆ Inspectors make daily reports concerning adequacy,

progress, and comments on decisions. These daily

reports may be of vital importance in subsequent

actions. 

 ̆ Administrative personnel make monthly reports on

quantity of work performed, contract earnings,

safety, employment records, and various other

statistical information as required.
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

217

 ̆ Intermediate and supervisory personnel summarize

these basic data periodically and make frequent

informal and monthly formal reports, as required,

and they include reports of all decisions made on

controversial matters.

Every construction project submits a monthly progress

report (referred to as the "L-29" report), "Construction

Progress Report, Concrete Construction Data, and

Earthwork Construction Data." This report covers the

progress of current construction activities and the structural

behavior of completed or partially completed features in

which observations are being made. Also, it provides a

continuous record of events and data for future reference.

Specialized reports on grouting, pile driving,

instrumentation, soil-cement construction, etc., are required

as needed [1]. These "technical" or "specialist" reports

contain:

 ̆ Tabulations of test results

 ̆ Statements of progress

 ̆ Amount of work performed

 ̆ Any questions concerning interpretation of

requirements or test results

 ̆ Descriptions of abnormal conditions or methods that

affect either quality or quantity of work accomplished

Copies of all these reports are sent to the central office for

immediate review by specialists so assistance or advice

concerning performance of work or testing can be provided

promptly if necessary.

Upon completing an earth dam embankment or other major

works, a Final Construction Report (summarizing the work

accomplished) should be prepared. In special cases,

additional summaries or reports may be required.

The narrative summary of these reports should be restricted

to matters of special importance or interest relating to

technical control exercised in earthwork construction. All

summaries should describe any difficult or unusual

experiences encountered during the reporting period. Types

of information desired are exemplified in the following list.

Of the items listed, only those that warrant reporting should

be included, such as:

 ̆ Description of foundation conditions encountered and

methods, procedures, and equipment used in:

preparing the foundation, stripping, excavating,

dewatering and unwatering the foundation, placing

piling or caissons, consolidating soils in place, etc.;

also, methods for protecting the foundation surface

prior to placing materials such as installation of

drains, wells, filters, geosynthetics, concrete

blankets, sealers, etc. Report unusual or unexpected

foundation conditions encountered and methods of

treatment.

 ̆ Describe preparation, clearing and stripping,

irrigation, and excavation operations in borrow pits,

required excavations, quarries, or other sources of

earth materials destined for the construction. List

methods used for adding or removing moisture,

separating, excavating, and hauling. Indicate sources

and delivery means of imported materials such as

filter sand, lime, cement and pozzolans, etc. Also,

describe borrow area drainage and restoration

procedures. Report any difficulties or unusual events

and remedies.

 ̆ Describe placement operations for embankments or

other earthfills, earth linings, structure and

instrumentation backfill, pipelines, and other earth

structures. The narrative shall include descriptions

of: equipment used (particularly the rollers); other

compaction or consolidation equipment; methods and

equipment for separating, scarifying, mixing,

blending, and controlling moisture on the fill;

finishing surfaces; placement of riprap, rock

blankets, filters, cover materials, and gabion

installations; final cleanup, landscaping, and seeding.

Include the quantities of earth materials placed in

each fill area, length of pipe backfilled, volume of

soil-cement placed, etc. Also include the elevations

reached for the various zones of major structures.

Report unusual or difficult experiences or conditions.

 ̆ Where necessary to clarify subjects emphasized in the

narrative section, suitably captioned photographs,

drawings, and sketches should be attached to the

summaries. Additional media such as films, video,

etc., may be useful.
EARTH MANUAL

218

B. Earthwork

3-6. General.&Differences in design requirements and

construction procedures have led to classifying fill

construction into three types: (1) embankments, (2) linings

and blankets, and (3) backfill. Usually, division lines

between fill types are not distinct. Embankment

construction applies primarily to laterally unsupported fills

built on top of the natural ground surface; however, refill of

cutoff trenches or key trenches is included as embankment

construction& especially regarding construction control.

Lining and blanket construction applies mainly to relatively

thin sheets of fill spread over an area of natural ground,

excavated surfaces, or embankment. Backfill refers to refill

of excavations below the ground surface or earth placed in

confined spaces and against rigid structures.

Based on the amount and kind of work required, each of

these groups is further divided into several types. Because

of the indistinctiveness of definition, where two or more

different types of construction are required involving

separate contractual pay items, it is customary to establish

arbitrary boundaries for the different types of work.

Separation may be definite, or an overlap may exist. The

lines of distinction will vary from job to job, so reference to

the particular specifications involved is required in all cases.

3-7. Embankment.&Engineering properties of soil

can be changed&and often improved&by:

 ̆ Selecting

 ̆ Controlling moisture content

 ̆ Mixing

 ̆ Stabilizing using various admixtures

 ̆ Compacting

a. Types of Embankment.&In the order stated, each

of those operations is successively more expensive to

perform. Although engineering properties are improved and

made more uniform, some of these operations may not be

justified for all structures.

In construction, any of the following types of embankment

construction may be specified:

 ̆ dumped fill,

 ̆ hydraulic fill,

 ̆ selected fill,

 ̆ equipment-compacted embankment,

 ̆ rolled earthfill,

 ̆ vibratory-compacted embankment,

 ̆ blended earthfill,

 ̆ modified soil fill.

b. Dumped Fill.&The simplest construction operation

of moving material from excavation and depositing it in a

fill to lines and grades is called dumped-fill construction.

This type of embankment is used to construct minor roads,

canals, and laterals when necessary engineering properties

can be developed in the available soil without special effort.

Although selection and distribution of material are not

specifically required, dumped fills should be free of tree

stumps and other organic matter such as trash, sod, peat,

and similar materials. Rocks, cobbles, and similar material

should be distributed throughout the section and not nested

or piled together. For the fill to be reasonably uniform

throughout, materials should be dumped in approximately

horizontal layers. "End dumping," a process by which fill

material is pushed off the edge of the fill and allowed to roll

down the slope, is objectionable because it fosters material

segregation and should be avoided wherever possible.

Dumped fill is often further classified as dragline-placed fill,

truck-dumped fill, or scraper-placed fill. If traffic over the

fill occurs during construction, either by construction

equipment or otherwise, it should be routed to distribute

compaction as much as possible.

On canal construction, a further requirement is to place the

finer and more impervious material on the water side of the

embankment. On road work, the gravelly material should

be in the top of the fill, and large rock should be well

buried. Inspection consists of visual examination to ensure

that the above requirements are satisfied and that

dimensional requirements are attained. Laboratory testing

of dumped fill construction is not required except for record

purposes.

c. Selected Fill.&Commonly used selected fill types

include selected impervious fill, selected sand and gravel fill

(pervious fill), rockfill, and riprap. Selected fill is a

dumped fill constructed of selected materials; occasionally,

compaction is required. This type of construction is widely

used where one engineering property is more important than

others, and soil with a specific property can be secured by

selective excavation. Accordingly, selected fill may be

specified to satisfy one of several engineering properties.

Construction and inspection requirements vary according to

the engineering property being emphasized.

The selected impervious fill type of embankment is used in

canal construction when selective excavation of the canal
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

219

prism will provide a superior structure with little extra

effort. Excavation from borrow pits and short hauls may be

required, but benefits derived solely from selection usually

do not warrant the cost of securing a better material from a

more distant source.

Selected sand and gravel fill is specified to improve

stability, to prevent frost heave, to provide improved

wearing surface on roadways, to prevent wave erosion of

underlying embankment, and to provide for removal of

seepage water without "piping." Benefits derived from this

type of construction often justify securing satisfactory

material from a considerable distance, and sometimes

processing to improve gradation is warranted. In choosing

material for sand and gravel fill, gravel is the more

important component, and a well-graded, rather than a

poorly-graded, material is preferred. Other characteristics

may be required for filter materials. Visual inspection

should be confirmed with an occasional gradation test.

Riprap and rockfill are used primarily for surface

protection. Riprap is used to protect against erosion by

flowing water and from ice and wave action and to protect

against rain and surface runoff. Rockfill is used to protect

against rain and minor surface runoff and to provide

stability to a fill structure; to some extent, it is used as a

substitute for sand and gravel fill in dams. Durability and

gradation are important requirements for riprap. These are

also desirable characteristics of rockfill, but the tolerance

ranges are much broader.

d. Equipment-Compacted Embankment.&Situations arise where selected fill does not produce an adequate

structure, and the addition of compactive effort by routing

of equipment will produce an acceptable fill. This type of

construction is mostly used on canal embankment and road

construction. Specifications for construction of these

features usually do not require a definite degree of

compaction. Control of moisture in the material may or

may not be required. Reference should be made to pertinent

specifications. Separate pay items may be used for addition

of water. The engineer in charge determines the amount of

water to be added largely on the basis of volume of fill to be

constructed and the nature of materials being used.

Sometimes, visual inspection is supplemented by laboratory

tests.

e. Rolled Earthfill.&Improving engineering properties

to the maximum practical extent by selection, compaction,

moisture control, and special processing is generally

justified in construction of earth dams and in canal

embankments. A failure could result in the loss of life or

substantial property damage, and conditions could develop

that would cause excessive water loss or expensive

maintenance costs. Where pertinent, procedures and

equipment are specified to ensure development of desirable

engineering properties to the maximum practical extent.

Materials selection will have been based on preliminary

investigations; that is, borrow areas will have been

designated. Preliminary investigations should have

disclosed the nature of the average materials and the

probable range of variation. Field personnel in charge of

construction operations should review preconstruction

investigation results, perform additional exploration and

testing (if necessary), and learn to recognize the kinds of

material acceptable for the adopted design. Since earth

dams and major canal embankments are designed to

accommodate materials available in the vicinity, the

materials used for various purposes will differ from site to

site. If, as a result of more detailed exploration or in the

process of construction, materials are encountered whose

characteristics differ appreciably from those anticipated, the

construction methods and procedures may have to be

changed.

For embankment dams, a specific moisture range and

density are generally specified. In specifying compaction,

requirements will include the general type of roller to be

used, the thickness of lifts, and the number of passes.

These requirements are based on extensive experience and

statistical data and will produce a satisfactory fill when

placed using good construction procedures. Specifications

include requirements for removal of oversize particles and

that the material be homogeneous in texture; that is, free

from lenses or pockets of material differing in gradation or

classification from the average material.

Soil moisture content must be controlled to obtain maximum

benefit from compaction. Specifications require water

content be uniform throughout the layer to be compacted

and that the layer be as close as possible to the water content

that results in most efficient densification of material to be

compacted. For the specified compactive effort, for earthfill

in dams, this water content is often slightly less than

optimum water content as determined by the laboratory

compaction test (see USBR 5500). 2

2

 5500: Performing Laboratory Compaction of Soils&5.5-lbm

Rammer and 18-in Drop.
EARTH MANUAL

220

Inspection is performed to determine whether the:

 ̆ Material is uniform and free from oversize particles.

 ̆ Compaction equipment complies with specifications

and is maintained in working order.

 ̆ Thickness of lifts and number of passes are according

to specifications.

 ̆ Moisture is uniform within the layer.

The inspector should determine that moisture content is

correct by performing manual tests to observe how the

material compacts in the hand and to confirm this by tests

using USBR 7240: Performing Rapid Method of

Construction Control. 3

 Inspection observations will be

supported with field and laboratory tests&USBR 7205,

7220, and 72404

&to determine the degree of compaction and

variation of water content from optimum, and USBR 5600

to determine permeability.5

f. Vibratory-Compacted Embankment.&Compaction

by vibration is usually specified in the construction of earth

dams to improve the engineering properties of strength and

consolidation in comparatively permeable soils; that is,

clean sands and gravels (GW, GP, SW, and SP). However,

several other methods of compaction will produce

satisfactory densification when permeability is not a

concern. Some of these methods are specified both for

highway and airport construction. If Reclamation forces are

required to supervise the construction of highways or

airports where maximum densification of sand and gravel

soils is required, specifications of the agency concerned will

be followed, and instructions necessary for field control will

be issued.

In constructing an earth dam, the contractor may propose

some method other than vibratory compaction to densify

permeable embankment materials. For those accepted

proposals, letter instructions covering construction control

will be issued as required.

In selecting filter and drain material to be compacted by

vibration, emphasis will be to eliminate soil contamination

by excessive amounts of fines [minus 75 μm (minus

No. 200 sieve size) material]. As a result, filters and drains

are designed with less than 5-percent fines. Field

inspection, therefore, will be directed toward removing

overburden fines, avoiding silt and clay lenses or pockets,

and preventing excavation into less permeable materials

below the sand and gravel deposit. Thickness of placed

embankment layers is commonly adjusted to avoid a

requirement for removal of oversize material, and

maintaining soil uniformity does not require the attention

that impervious fill construction requires. However, coarser

material should be placed toward the outer slopes. Where

vibratory compaction is specified, the material source will

be designated, minimum size tractor or vibratory roller

described, lift thickness and number of passes enumerated,

and moisture requirement defined.

Compaction by a vibratory roller or track-type tractor

depends on the vibration produced by the equipment in

operation. A secondary benefit results both from size and

mass; for example, thicker layers can be compacted with

larger equipment. Speed of the vibratory roller is

considered beneficial in that the effect of increased vibration

with high speeds more than compensates for any detrimental

effects of short period application. Maximum compaction

of sands and gravels is obtained by vibration when the soil

is either completely dry or thoroughly wetted without being

saturated. The wet condition is specified because

satisfactory density is more readily obtained, and field tests

are more likely to be reliable with wet compaction.

However, under certain conditions, dry compaction has

been permitted. In these circumstances, extra compactive

effort is necessary in lieu of thorough wetting. To secure a

thoroughly wetted material, excavation of materials from

below water table has been permitted in some instances.

This procedure is successful when small-size excavation

equipment combined with a relatively slow placement rate

is used. With large capacity equipment and a rapid

placement rate, drainage of excess moisture may be too slow

to permit satisfactory compaction.

Inspection consists of noting that proper quality of material

is used and that specified thickness of lifts and number of

passes are obtained. Water content is sufficient if free

moisture appears in the equipment tracks immediately

following passage. With proper water content, the

compacted fill will appear firm and solid. If the fill remains

soft, moisture is too great; if the fill is fluffy, water content

is insufficient.

g. Blended Earthfill.&Circumstances occur in which

two individual materials do not have adequate engineering

properties but, when combined, produce a satisfactory

material. Other cases arise in which a material having

inferior properties may be combined in a mixture with

3

 7240: Performing Rapid Method of Construction Control.

4

 7205: Determining Unit Weight of Soils In-Place by the Sand-Cone

Method.

7220: Determining Unit Weight of Soils In-Place by the Sand

Replacement Method in a Test Pit.

7240: Performing Rapid Method of Construction Control.

5

 5600: Determining Permeability and Settlement of Soils 8-in

(203-mm) Diameter Cylinder.
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

221

another material of adequate engineering properties to

increase the quantity of satisfactory material available.

When the materials to be blended occur as strata (one above

the other) in the same borrow pit, excavation by shovel or

wheel excavator can readily blend them together with little

extra effort or expense (see fig. 3-3). In this case,

construction control will require maintaining the height of

cut to obtain the necessary proportions of each type material

and to ensure that the two materials are being blended.

With dragline excavation, satisfactory mixing can be

accomplished, but greater attention must be given to the

operation because the tendency will be to remove material

in horizontal cuts. Several types of excavating equipment,

such as wheel excavators and belt loaders, have excellent

capabilities for blending vertical cut material (see fig. 3-24).

When scraper excavation is used, the difficulty in attaining

a satisfactory mixture is increased; frequently, supplemental

mixing is required on the fill by plows, discs, rippers, or a

blading operation. Excavation is performed by making a

slanting cut across the different types of materials; care must

be exercised to effect the proper proportions of each type of

material in each scraper load. Loading the materials in an

upslope direction usually gives a more effective mix of

materials than loading in a downslope direction. A common

practice is to spread the materials in half-lift thicknesses to

improve uniformity and minimize requirements for mixing

on the fill.

The cost considerations limit the procedure for blending

materials from separate sources to special situations such as

blanket and lining construction. First, one of the materials

is stockpiled upon the other so excavation can be made

across the two materials, or the materials are placed in thin

layers on the fill; then, they are mixed by blading, plowing,

or similar procedures before being compacted. Mixing

machines may be specified to obtain an optimum mixture for

earth linings.

h. Modified Soil Fill.&A fill using a soil that has been

modified by addition of minor quantities of a selected

admixture prior to compaction is called a modified soil fill.

The most commonly used additives are lime and cement.

The use of modified soils should be considered in lieu of

replacing poor soils with selected material from a distant

source. For example, to construct a switchyard fill, lime

can be used to modify expansive characteristics of a clay

soil.

Usually, conventional methods are used to spread and

compact the modified fill. In addition, some type of

equipment must be adapted to distribute and mix the

additive. This equipment requires initial calibration and

periodic checks during construction to ensure that the proper

amount of additive is being applied. Special tests of the

modified soil may be required to verify the amount of

additive, and visual observations should be made to ensure

that the additive is uniformly distributed. Construction

control testing of placement moisture and density is

required.

Inspection requirements will be comparable to those

required for concrete or other specialized materials, and

extensive testing should be anticipated. Considerable

experimentation may be required to develop suitable

construction procedures.

i. Hydraulic Fill.&Most methods of embankment

construction all involve control of water content. Some

situations require placement of fill material under conditions

of excess water content. These situations may involve

excavation and transportation of the material by use of

flowing water. The more common procedures involve only

the placement of material in still water or by the process of

washing material into place or densifying it with a stream of

water.

Terminology for the different types of hydraulic

construction is not standardized. In general, the term

"hydraulic fill" is applied to the complete operation of

excavation, transportation, and placing by flowing water.

When the hydraulic operation is confined to placing, it is

described as semihydraulic construction. The term "puddled

fill" is applied to special types of semihydraulic fill, and the

term "sluiced fill" is used for material washed into place.

There are several severe limitations to hydraulic fills which

may make them undesirable for embankment construction.

Uniform granular or cohesionless hydraulic fills, without

active densification measures, will result in very low

degrees of compaction. For undensified cohesionless soils,

the typical relative range is 30 to 60 percent. There have

been numerous examples of severe distress to hydraulic

fills, such as embankments, quay walls, and tailings piles

under earthquake loadings [2]. One such example is

earthquake-induced liquefaction experienced at Lower Van

Norman Dam during the 1971 San Fernando earthquake.

Puddled, sluiced, or hydraulically placed, fine-grained soils

will be weak and highly compressible. Many years may be

required before fine-grained soils are improved by

consolidation. In large embankments, the use of high water

content, fine-grained soils may result in high pore pressure

generation and reduced shear strength resulting in

unacceptable deformation or shear failures. Many hydraulic
EARTH MANUAL

222

Figure 3-3.—A deposit of impervious material which overlies a deposit of pervious material.

fill structures were built prior to the 1930s. Due to the

limitations listed above and the advent of modern

compacting equipment, hydraulic fill lost popularity after the

1930s [3].

Economical use of hydraulic fill construction depends on:

(1) availability of a material that is readily sorted by the

action of flowing water into a pervious material zone and an

impervious material zone, (2) a large volume operation, and

(3) a source of inexpensive power. This combination of

conditions happens so rarely that control procedures for

hydraulic fill construction have not been developed for

Reclamation operations. In the event that hydraulic fill or

semihydraulic fill is specified, special instructions will be

issued by the Denver Office engineering staff.

Sometimes, puddled-fill construction is used where climatic

conditions make moisture control operations impractical, for

backfill around pipelines and structures, and in lieu of

special compaction against rough and irregular surfaces.

The puddling process consists of depositing the soil in a

pool of water, stirring the soil-water mixture until a fairly

uniform slurry is developed, and then allowing the soil to

settle out of the mixture. Puddling is used mainly for soils

of low permeability, such as silts and sandy lean clays,

where high density is not necessary. Inspection is by visual

examination to establish that the proper type of material is

used and to ensure that thorough mixing is accomplished.

Puddled fill has many undesirable properties. The slurry

can consolidate over time, and unacceptable deformations

and stress distributions can occur. The slurry is weak, and

upon continued loading, high pore pressures can be

generated, resulting in further loss of strength. These

undesirable properties make the puddling method

unacceptable for many structural backfill applications.

Puddled clay core dams were often constructed in older

dams in the United Kingdom, where wet clay was healed by

foot or equipment traffic into thin central clay cores. The

wet clay had very low hydraulic conductivity. Many of the

dams have performed well, but there are concerns about

stress distributions, cracking of shells, and hydraulic

fracturing.

Sluiced-fill construction involves working a pervious

material into place by a washing operation produced by the

flow of a high-velocity stream of water. The method is used

to wash sand and gravel or rock fines into the voids of a

rock mass such as a rockfill. In lieu of tractor or vibratory
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

223

rollers, the method may be used for compacting sand and

gravel fill. Vibratory-compaction construction is considered

superior to sluiced-fill construction; hence, the latter is

usually restricted to areas inaccessible to equipment.

Inspection consists of visual examination to determine that

appropriate materials are used and that the washing

operation is properly performed; that is, the materials are

actually moved in the process. When sluiced-fill

construction is used in lieu of vibratory- compaction

construction, relative density tests are required to ensure

adequate densification.

Compacted fill is sometimes specified to be compacted in a

thoroughly wet condition using equipment such as

pneumatic rollers, vibratory rollers, surface vibrators, or

tractors. Soils placed by this method must have a relatively

high permeability for proper densification. A density

requirement is specified and is based on relative density.

3-8. Linings and Blankets.&

a. General.&In earth construction, many situations

require constructing a relatively thin layer or blanket of

selected material. These categories include:

 ̆ Layer of riprap on the upstream slopes of earth dams

 ̆ Sand and gravel blanket under riprap

 ̆ Rockfill blankets or blankets of gravel or topsoil on

the downstream slope of dam embankments

 ̆ Filter blankets under the downstream portions of dam

embankments and under the floors of concrete

structures

 ̆ Impervious blankets on the floors of reservoirs

 ̆ Channel linings for canals

 ̆ Linings and covers for hazardous waste disposal

areas

Base courses and surfacing on roads or highways, and

ballasting for railways, are considered to be in this category.

A common requirement of these types of blankets is proper

selection; that is, locating and using suitable materials.

Sources of material that have established characteristics and

in ample quantity for the various blanketing requirements

should always be determined before construction.

A requirement of all blankets is careful placement.

Requirements may vary widely according to the type and

location of blanket placement, but uniformity and thickness

are extremely important in every case. On the basis of

material used, blankets may be divided into four types:

(1) Rock.

(2) Sand and gravel.

(3) Silt and clay (impervious).

(4) Topsoil.

b. Rock Blankets.&The rock fragments used in rock

blankets should be essentially equidimensional, angular,

well graded from a maximum dimension equal to blanket

thickness to about one-tenth of blanket thickness&and

sound, dense, and durable. Elongated and thin slabs of rock

are undesirable, but rock fragments whose minimum

dimension is about one-third to one-fourth of the maximum

dimension are not objectionable. Although angular rock is

the most desirable, subangular and subrounded cobbles and

boulders are commonly used. While rounded cobbles and

boulders have been used as riprap in certain cases, their use

is more appropriate for blankets on flat surfaces. Testing

and placement of rock blankets are discussed in more detail

in section 3-24 on riprap.

Grading of riprap and other large stone can be performed in

accordance with ASTM procedure D-5519-94 [4]. The

procedure allows for determination of grading by volume,

mass, or a combination of volume and mass. On critical

projects, it may be necessary to specify testing and provide

for testing facilities such as concrete pads and scales.

Generally, blasted rock that has an appreciable quantity of

fragments near the maximum size requirement will possess

a satisfactory gradation. The condition to avoid is an excess

of small-size fragments. Fine material such as rock fines,

sand, and rock dust, in a volume not to exceed the volume

of the voids in the larger rock, may not be objectionable,

depending upon the purpose of the blanket.

Soundness, denseness, and durability requirements may vary

somewhat according to usage. The highest quality rock is

required for protection of slopes in stilling basins. The

soundness requirements for riprap on dams may vary

somewhat according to reservoir fetch and operating

characteristics; rock size, to some extent, can be substituted

for high density. Protection of downstream slopes of dams

can be accomplished with any rock that does not break down

appreciably by normal exposure to weather. Shale is about

the only rock that is unacceptable for downstream slope

protection of dams.

c. Sand and Gravel Blankets.&The characteristic of

sand and gravel mixtures to allow passage of water, while

at the same time preventing passage of soil grains, is

extensively used in the design of water retaining structures.

The properties of resistance to displacement by flowing

water, resistance to wear from vehicular traffic, and

maintenance of strength and limited volume change over a
EARTH MANUAL

224

large range of water contents, make sand and gravel useful

in providing surface protection to canal banks, roads, and

working areas in the various facilities of irrigation and

power projects. The wide range in gradation possible in

sand and gravel mixtures, together with the wide range in

structural materials to be protected, results in a wide range

of acceptability for the materials used for sand and gravel

blankets. However, blankets under the downstream portion

of an earth dam embankment must be designed as a filter.

Pervious blankets under concrete structures usually are

made as thin as possible. This condition makes processing

of material from natural deposits almost a necessity so as to

produce the specified gradation of material. Two-layer filter

systems are frequently used.

Sand and gravel used as base courses and surface courses on

roads, highways, and switchyards are normally processed

material. Materials used for surface courses differ from

pervious blankets for other uses in that a certain amount of

clayey material is considered desirable to bind the material

together and, in some instances, is actually added to

improve the quality of surface courses.

Pervious blankets used to prevent erosion in canal channels

require a material predominantly in the gravel range.

Appreciable quantities of sand are undesirable, and, in some

instances, removal of fine sand may be required. A sand

layer may be required between a coarse gravel layer and the

subgrade to prevent movement of fine subgrade soils

through the gravel. Materials for a pervious gravel blanket

and materials for an impervious blanket may be combined

to provide an erosion-resistant impervious blanket. Usually,

filter criteria are not important in impervious blankets.

Crushed rock may be used for any of the above-described

purposes. Crushed rock is a processed material that can be

manufactured to fulfill specifications requirements.

Sand and gravel or crushed rock blankets usually are

densified by equipment compaction using vibrating

equipment or operating smooth rollers. They may be placed

either dry or thoroughly wetted. Inspection is commonly by

visual examination, but gradation and relative in-place

density tests may be required in some cases.

d. Impervious Blankets and Linings.&Impervious

soils are used on reservoir floors and in canal channels to

reduce seepage. Material for these purposes must be:

 ̆ Impermeable

 ̆ Free from shrinking and swelling characteristics

 ̆ Resistant to erosion from flowing water

 ̆ Stable when placed on the sides of canals and

reservoirs

Probably the best material for these purposes is a wellgraded gravel with clay (GW-GC), which offers both

impermeability and excellent erosion resistance. A clayey

gravel (GC) material or a silty gravel (GM) material is also

suitable. Materials in other soil groups can be used

according to the engineering use chart, table 1-4 (ch. 1).

When satisfactory soils are not available, processing soil by

blending or protecting the fine-grained soil with a blanket of

sand and gravel is necessary.

Blankets and linings to be permanently underwater need not

meet erosion resistance and shrinking and swelling criteria.

Blankets and linings placed on essentially horizontal

surfaces need not possess high stability characteristics.

However, an impervious blanket beneath a reservoir may

require a filter beneath it to prevent piping of the blanket

material into the foundation.

Thickness of impervious blankets is usually controlled by

placement procedures. However, at high reservoir heads,

thickness greater than the minimum required for

construction operations may be required. Also, where some

swelling or shrinkage is anticipated, thickening impervious

blankets may be desirable so an effective thickness of

blanket (unaffected by swelling or shrinkage cracks) is

maintained. For canal linings, thickness generally is varied

depending on design requirements; availability of lining

material may affect thickness, and construction methods

may need to be revised to attain desired engineering

properties.

Construction and inspection requirements are similar to

those for rolled earthfill and blended earthfill.

e. Topsoil Blankets or Zones.&Topsoil blankets or

zones sometimes are specified for downstream slopes of

dams so slopes can be seeded to protect the underlying zone

against wind and rain erosion. Topsoil for restoring borrow

areas or other areas&where existing topsoil has been

destroyed or removed&is specified to fulfill ecological and

environmental requirements.

Normal topsoil sources are materials stripped from required

excavation for the dam and appurtenant structures and

approved stripping from borrow areas. Generally, it is not

feasible to borrow topsoil. Consequently, suitable materials

from stripping, which would otherwise be disposed of as

waste material, should be selected during excavation and, if

necessary, stockpiled for later use.
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

225

Table 3-1.—General suitability of soils for compacted

backfill by saturation and internal vibration

Soil type Limitation1

GW, GP, SW, SP All soil types are suitable.

 Fines in these soils are limited

 to less that 5 percent by

 definition.

GW-GM, GW-GC

 GP-GM, GP-GC

May or may not be suitable,

 depending on gradation and

 plasticity.

SW-SM, SP-SM,

 SP-SC

Test section may be required. 

 Fines are limited to 5 to 

 12 percent by definition.

SM, SC Normally unsuitable.

 1 Fines are particles smaller than U.S.A. Standard 75 μm

sieve (No. 200).

Normally, specifications require a 0.3-m (1-ft) normal

thickness for topsoil blankets; thus, areas requiring topsoil

should be brought to within 0.3 m of the prescribed final

cross section at all points and finished smooth and uniform

before topsoil is applied. Topsoil should be evenly placed

and spread over the graded area and compacted in two

layers.

Occasionally, for dams requiring topsoil, it will be

advantageous and economical to specify a thin topsoil zone

for downstream slope protection. A prime advantage is that

excavated topsoil can be placed concurrently with the rest of

the embankment&eliminating the requirement for

stockpiling. When a topsoil zone is specified, construction

and inspection requirements are similar to those for rolled

earthfill.

In most cases, seeding of topsoil on downstream slopes is

required; thus, topsoil should be selected from required

excavation or from a stockpile so the most fertile soil is

obtained. Topsoil must be free of excessive quantities of

large roots, brush, rocks, and other objectionable matter.

Topsoil should not be placed when the subgrade is frozen or

in a condition otherwise detrimental to proper grading and

seeding.

3-9. Backfill.&

a. General.&Backfill is earthfill in confined spaces,

such as refilling operations about concrete structures.

Refilling operations associated with embankment,

construction work adjacent to the concrete structure and in

other confined areas may be called special compaction rather

than backfill. Backfill operations may be divided into three

categories: (1) backfill, (2) compacted backfill of clayey

and silty soils, and (3) compacted backfill of cohesionless

free-draining soils.

b. Compacted Backfill.&Compacted backfill covers

two types of materials and compacting operations. The first

is compaction of clayey and silty materials of low

permeability. These soils are used for backfilling structures

when seepage is to be limited or if drainage is not required.

Normally, this type of backfill is compacted by tamping

rollers when space is available or by power tampers in

confined areas. Generally, the soils are compacted at

optimum moisture content and to a given percentage of the

laboratory maximum density.

The second type of compacted backfill uses cohesionless

free-draining soils of high permeability. These soils are

used around or under pipelines and structures when free

drainage is desired or when a bedding or a foundation of

low compressibility is required. The materials used must be

free-draining sandy and gravelly soils. When high stability

and low settlement are design requirements, this type of

backfill is often preferred over compacted backfill of clayey

and silty soils because of the ease and economy of

placing&particularly in confined areas. For example, when

good support is required under and around concrete pipe,

the material can easily be made to flow and can be

compacted to high density in the critical area beneath the

pipe and between the pipe and trench surfaces&providing

proper procedures are used for wetting and vibrating the

material. A fill of clean sands or gravels is specified often

for use under pumping plants and other structures when

necessary to improve the bearing capacity of soft foundation

soils. This improvement is accomplished by removing the

soft materials and replacing with selected backfill to spread

the load onto lower strata. Also, cohesionless free-draining

soils are preferred as backfill adjacent to some structures

when excessive surface settlements are undesirable or when

space is limited.

Generally, compaction of these soils is accomplished by

pneumatic rollers, vibratory rollers, tractors, surface

vibrators, or internal vibrators. 

Proper selection of materials is particularly important when

compacting using saturation and internal vibration.

Excessive amounts of fines will fill the voids between

coarser particles and will prevent drainage. Table 3-1

provides information for preliminary selection of soils

suitable for compaction using saturation and vibration.
EARTH MANUAL

226

3-10. Excavation.&Materials for embankment or

lining construction are obtained either from required

excavations or from borrow pits. Materials from required

excavations should be incorporated into embankment or

lining construction to the maximum extent possible. When

materials from required excavations can be used, the same

practices should be followed as in borrow-pit excavations.

Organic material such as plant growth and decaying

vegetable matter should be removed from the surfaces of

borrow pit within borrow areas before initiating excavation.

Depth of stripping varies according to the nature of ground

cover&from 50 to 75 mm (2 or 3 in) for prairie grasslands

to 600 to 900 mm (2 or 3 ft) in valley bottoms and forested

areas. The removal of all material containing grass and tree

roots is not necessary. The fine hair roots of grass and tree

roots less than 6 mm (1/4 in) in diameter are normally

considered not sufficiently detrimental to justify wasting

material containing minor amounts of this matter.

Excavating an area greater than required, in one

construction season, is inadvisable because of recurring

weed growth. The minor amount of weed growth that may

develop during the latter part of a construction season on a

stripped area is usually considered unimportant.

Occasionally, deposits of impervious soil are covered with

a layer of boulders; often, sand and gravel deposits are

covered with a layer of silt and clay. Such a deposit is

shown on figure 3-3. A thorough materials investigation for

an earthfill dam resulted in the most economical benefit to

use the upper clay-silt-sand portion of the deposit for the

impervious zone and the lower silt-sand-gravel portion for

the pervious zone, thus eliminating the need for another

borrow source with its subsequent additional development

costs. When impractical to salvage upper layers, they are

classed as stripping and wasted even though the layers may

be thicker than is normally considered applicable to

stripping.

In highway and canal construction, where the normal

method of excavation is by scraper, a lower limit to the

depth of cut is not required. In all other excavations, cut

depths less than 0.2 to 1.5 m (4 to 5 ft) are avoided for

economic reasons unless deficiency of material dictates

smaller cuts. Except in situations where separation between

two different types of material is desired or in which

controlled blending is required, maximum depths are usually

limited by the range of excavating equipment. However,

the maximum depth of cut may be limited by the presence

of bedrock or hardpan and, except for sand and gravel

excavation, by location of the water table. In stratified

borrow areas, excavation must be made so that every load

delivered to the point of use contains a mixture of the full

designated depth of cut. Extra mixing on a stockpile or on

the fill may be required.

C. Foundations

3-11. General.&If conditions in soils supporting a

foundation could be completely described as a result of

subsurface investigations and designs were prepared

accordingly, field inspection&during construction&would be

reduced to merely determining that dimensional

requirements of designs were satisfied. However, even a

thorough investigation program leaves the majority of

foundation soils and rock unexplored.

Because of the variety of conditions that may be encountered

in natural soil deposits, a complete set of guidelines for

judging adequacy of foundation soils is impossible to

provide. Individual judgment based largely on experience

must be used. The first objective in developing experience

is to enhance one' s ability to discriminate between sound

and unsound foundation soils. In practice, this means

classifying foundation soils as adequate, inadequate, and

questionable for the type of structure being built. Initially,

most cases seem to fall in the questionable category; but

with increasing experience, the number of cases decrease.

To supplement judgment, test procedures have been

developed for evaluating foundation soils. Such tests should

have been performed during the investigation program;

comparison by means of index tests and visual examination

between tested and untested areas will usually suffice to

establish adequacy. Additional tests may be required during

construction.

Conditions for which adequacy of foundation soils should be

established include bearing capacity, stability, ettlement,

uplift, deterioration, and permeability. The degree to which

each of these items is important depends on the nature of the

proposed construction, character of foundation soils, and

structural characteristics of the foundation.

3-12. Bearing Capacity.&Foundations for rigid

structures are usually evaluated on the basis of bearing

capacity. Bearing capacity in this sense involves both shear

strength of the soil and its consolidation characteristics.

Bearing capacity may be determined in the laboratory by
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

227

shear and consolidation tests on undisturbed samples or

approximated in the field from in-place dry density tests,

standard penetration tests, vane shear tests, cone penetration

tests, borehole shear tests, or pressuremeter tests.

The design of rigid structures should include the type of

foundation treatment required based on information

available from the investigation program. Where foundation

soils appear to be the same as those disclosed at locations of

the investigations, they may be assumed to be equally

competent. If soil conditions are disclosed that are

observably different from those disclosed by previous

investigations, the lateral and vertical extent of this different

condition should be determined before construction

continues.

One should be aware that a pocket or lens of harder or

firmer material in foundation soils can be equally as

detrimental as softer deposits. Therefore, common practice

is to specify that if such material is encountered, it will be

removed to some depth and be refilled with compacted soil

to provide a more uniform soil deposit at foundation grade.

This requirement should include beds, layers, or lenses of

indurated gravel or sand, shale, indurated clay, hardpan,

caliche, and other erratic cemented deposits such as

calcareous or siliceous material. The most desirable soil

deposit for a structural foundation has a uniform character,

and a moderate amount of additional excavation to develop

such a condition is usually justifiable.

3-13. Stability.&Excavation for a foundation can be

divided into two parts, the base and the side slopes. Except

for structures such as chutes of canals and spillways, the

load of the structure rests on the base of the excavation and

settlement usually limits development of full shear resistance

of foundation soils. Consequently, stability of the base of

an excavation may not present a problem. However,

foundation excavations adjacent to bodies of water or

directly above water bearing strata should be investigated

for loss of support caused by artesian pressure.

For most construction, cut slopes should be determined by

practicing geotechnical engineers using data available from

the investigation program together with appropriate analyses

and design experience. Federal, State, or local

requirements must be considered in the selection of

excavated slopes. Use of slopes not previously analyzed or

pre-established should be discouraged because of the many

variables involved in determining stable slopes such as soil

type, ground-water conditions, depth of cut, and intended

use. Both experience and engineering analyses are required

for this determination.

In determining stable slopes, a great deal of information can

be gained from examining previously excavated slopes and

natural slopes in similar soil in the same geographic area.

Stable slopes in sand and gravel are independent of height

of cut, but are very dependent on local ground-water

conditions. Likewise, safe cuts in saturated clay are

dependent on cut slope height and relatively independent of

slope. Because most soils are combinations of sand, gravel,

and clay, safe cuts will be controlled both by height and by

slope. Evaluation of natural slopes should consider that the

safety factor against failure is variable and that any increase

in slope (i.e., placing fill at the top of a slope or excavating

at the toe of the slope) results in reducing the safety factor.

Therefore, a natural slope should be steepened as little as

possible.

The presence of water has a significant effect on slope

stability. This can be in any combination of seepage,

rainfall, or water being conveyed or stored. An example of

failure of a natural slope (landslide) is shown on figure 3-4.

Excessive moisture was allowed to enter the soil, and

removing soil at the toe of the slope for constructing a

stilling basin may have triggered the slide. Where an

excavation cuts across the ground-water table, sloughing

may occur. To overcome this condition, the usual practice

is to remove ground water from the area before excavation

by any combination of well points, deep wells, or sump

pumps. Figure 3-5 shows well points and sump pumps used

in trench excavation; figure 3-6 shows removal of ground

water using drainage ditches and sump pumps. Damage to

a slope may result from high hydraulic gradients produced

by seepage. Where pumping is not practical, excavations

may be accomplished by making repeated cuts, which result

in gradually lowering the hydraulic gradient as ground water

is drained away. The success of any method is dependent on

a thorough knowledge of ground-water behavior and of local

soil conditions.

Where permanent cut slopes intersect the ground-water

table, some type of treatment is usually necessary to prevent

slope failure or sloughing. Required treatment involves

moving the free surface of the water table back from the

face of the slope or controlling the water as it exits the

slope. This may be accomplished either by drilling drainage

holes into the slope, excavating and placing drains in the

slope, or protecting the surface of the slope with freedraining materials such as a gravel or rock blanket on

geosynthetic drainage materials. Unless the potential for

seepage is high, a rock or gravel blanket will usually

suffice. A blanket 0.3 to 0.6 m (1 to 2 ft) thick placed on

a geosynthetic fabric or granular filter could be used in such

cases that are discovered during construction because cost
EARTH MANUAL

228

Figure 3-5.—Cutoff trench at Davis Dam in Arizona.

Figure 3-4.—Landslide (natural slope failure).
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

229

Figure 3-6.—Cutoff trench at Twin Buttes Dam in Texas.

is relatively small. Where material in the slope is well

graded and free draining, a blanket will develop naturally in

many situations, and special treatment may not be needed.

Rainwater damage commonly takes the form of surface

erosion. Preventive measures may include:

 ̆ Divert surface runoff away from slope faces with

small collector ditches a short distance back from the

intersection of the slope with the ground surface.

 ̆ Install surface sodding or blanket with a thin layer of

gravel or rock on a layer of geosynthetic fabric.

 ̆ Construct ditches to carry water off laterally from the

slopes.

 ̆ Steepen the slopes, as long as the slope remains

stable.

However, when rainwater can infiltrate foundation soils to

produce a rise in ground-water levels and resultant seepage,

both the sodding and slope steepening procedures may

actually be detrimental and, therefore, should not be used in

conjunction with a seepage condition without an adequate

analysis of the situation.

Erosive action from flowing water in a canal or wave action

in a reservoir is potentially the most severe type of water

damage. Protection involves flattening of slopes or

protection with gravel or rock blankets placed on

appropriate granular filters or geosynthetic materials

depending on the severity of the potential damage.

Situations exist where sloughing of slopes is not particularly

important such as in borrow pits within the reservoir area.

Such slopes should be flattened sufficiently to reduce the

hazard.

Situations may arise where selection of slopes is controlled

by criteria other than stability alone. For example, some

state highway departments use cut slopes closely

approximating natural slopes as a method of drift control for

sand and snow. Some state highway departments require

flattened slopes for grass cutting equipment. In some canal

work, 2h:1v slopes are specified (depending upon the types

of materials) instead of the more conventional slopes to

minimize maintenance and to provide more stable channels.

Sometimes, slopes are flattened in connection with earth

dams and high canal fills to distribute stresses caused by

high embankments.
EARTH MANUAL

230

3-14. Settlement and Uplift.&If a structure is not on

bedrock or supported by means of piles, piers, caissons, or

walls, the structure must be capable of withstanding some

vertical movement in the foundation soils. The usual

method for reducing such movement to within acceptable

limits is by spreading the base or footings of the foundation

so that unit pressures are reduced.

Uplift of structures may occur from several causes such as

hydrostatic forces, wetting of expansive soils, and frost

action. Structures and canal linings must be protected

against excessive upward movement. For light structures,

such as chutes and lined canals, protection against

hydrostatic uplift must be provided. This is commonly

accomplished by underdrains or drainage blankets of sand

and gravel and/or geosynthetic drainage materials. Where

possible, these drains will discharge into adjacent drainage

channels or into the structures. For certain lined canals, this

may require flap valves on outlets into the canal. Special

care should be taken to keep the drains open and the

drainage medium free from contamination. 

Expansive soils may cause uplift upon wetting, particularly

when the loads are light, when the initial in place dry

density is high, and when the initial moisture content is low.

Usual methods for reducing movement of rigid structures

are by using long friction piles or belled caissons attached

firmly to the structure, by increasing unit footing pressures,

or by removing expansive soils and replacing with

nonexpansive soils to a depth sufficient to control

movement. Flexible canal linings such as earth linings or

geomembrane linings are used in preference to rigid canal

linings on expansive soils. In some cases, the structure load

is less than that of the original earth removed, and elastic

rebound may occur. This is true, particularly when

saturated expansive clays are involved. In some cases,

where structural loads are small, as in canal linings,

conditioning the expansive clay is possible by prewetting the

foundation and maintaining a moist condition so as to

minimize future expansion.

Frost action may also cause undesirable heaving and uplift.

The susceptibility of soil to frost action depends on: (1) soil

type, (2) temperature conditions, usually expressed in terms

of a "freezing index" (a summation of the degrees below

freezing multiplied by the days of below-freezing

temperatures), and (3) water supply. Uplift, from the

development of ice lenses in foundation soils, may cause

damage to such works as concrete canal linings, spillway

apron slabs, and other lightly loaded structures. Frost

action can also cause a decrease in the dry density in

compacted earth canal linings [5]. All soils, except those

classified as GW, GP, SW, or SP, may be susceptible to

frost action in cold climates and with water available. The

susceptibility of gravelly and sandy soils varies with the

amount of fines. Silts and clays, with a plasticity index of

less than 12, and varved silts and clays are particularly

susceptible to frost action.

Collapsible/low density soils can result in sudden settlement

of a foundation upon wetting (see sec. 3-17). This condition

is particularly severe in very arid portions of the Western

United States, where these types of soils were usually

deposited as Loess or as quickly deposited materials on the

outer limits of alluvial fans. More than 1 m (3 ft) of

settlement is common in widespread areas of collapsible/low

density soils. The usual treatment for collapsible/low

density soil areas is to prewet the foundation areas for

weeks or months in order to precollapse the soils at depth.

The best method of prewetting is through ponding

(preferably with wick drains); however, other methods such

as sprinkling, water injection, or dynamic compaction can

be effective. Explorations and analyses need to be

performed in areas of potentially collapsible/low density

soils to determine the areal extent, depths, and percentages

of collapsible/low density soils that can be expected.

Subsidence due to long-term fluid withdrawal is also an area

of potential settlement concern. Generally, subsidence

occurs at such a slow rate that foundations are not

immediately affected. However, the long-term use of a

structure, such as a canal, can be severely impacted. Again,

extensive explorations and analyses need to be completed in

order to mitigate the effects of subsidence on the long-term

operation of a structure.

3-15. Deterioration.&The surface of excavated

slopes in both soil and rock should be preserved in their

natural state as much as possible. A cover of soil should be

maintained over the excavated surface until final cleanup,

and the structure or foundation should be placed

immediately. Drying of the excavated surface should be

avoided. Some indurated clays and shales will dry and

crack when exposed to the air and then turn into a soft

slurry upon rewetting. When it is impossible to place the

structure or foundation immediately after such surfaces are

exposed, a spray-on cover of pneumatically applied mortar

or other approved material has been satisfactory in some

situations.

3-16. Permeability.&Water retention structures,

particularly reservoirs and canals, depend on foundation

soils for a part of their water barrier. If access to a waterbearing stratum exists, either through the process of

excavation or from natural conditions, some corrective

action is indicated. However, no soil formation is
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

231

Figure 3-7.—Typical sinkhole.

water-tight, and some water loss can always be expected.

Movement of water from a reservoir or canal may result in

piping or excessive water loss. These problems can be

reduced by: (1) controlling the velocity of flow;

(2) controlling the volume of flow; and (3) controlling exit

conditions. The treatment required may or may not be the

same for problems (1) and (2).

Damage to foundation soils resulting from water movement

may be caused by gradual removal of soil particles either by

solution action or by mechanical movement. Solution action

is a problem only when foundation soils contain substantial

amounts of soluble minerals. 

The existence of solutioning in a foundation can be a serious

problem. Whether such a condition involves primarily

bedrock or soil solutioning can produce sinkholes in

surficial soils. These sinkholes are often small in extent;

and unless positive evidence is apparent that they are

watertight, sinkholes should be stripped to sufficient depth

and filled with compacted impervious soil when they are

found along canal alignments. In reservoir areas and dam

foundations, 

further explorations and more positive methods of treatment

may be necessary. A sinkhole is shown on figure 3-7.

Similarly, in the excavation process, when bedrock surfaces

are exposed (i.e., contain solution channels, open holes, or

cracks), such openings should be sealed with concrete or

blankets of compacted impervious soil. An extensive

grouting program may be required to seal the bedrock

surface.

In limiting water loss at dams, as a rule of thumb, at least

95 percent of the pervious cross-sectional area of the soil

foundation must be blocked. However, where a soil

foundation consists of zones (or strata) of differing

permeability, and 1 zone is more than 10 times as permeable

as another, blocking of the more pervious zone is usually

effective in reducing water loss even though it may be only

a small part of the total permeable area. When water

conservation is required, a permeable strata only partially

excavated may be unacceptable. The strata may need to be

completely cut off by continuing the excavation down to a

lower elevation so that the entire permeable zone will be

blocked, or by cutting the strata completely off by use of a

cut off wall, or other similar means.
EARTH MANUAL

232

Similarly, on canals, any lined reach should be extended to

cover the entire reach of a pervious stratum. Consideration

should be given to fully lining (or using pipe) all constructed

water conveyance systems. Thorough justification is

required for using an unlined waterway. A study considers:

 ̆ Value of water saved

 ̆ Operation and maintenance cost

 ̆ Required drainage

 ̆ Right-of-way

 ̆ Allowable velocities

 ̆ Structure costs

 ̆ Cost of various types of lining correlated with other

conditions

 ̆ Amount of tillable land removed (for canal alignment

and because of seepage)

 The unit value assigned to each item varies with local

conditions; therefore, the amount of water loss allowed

before lining a canal may vary considerably in different

areas.

In constructing long canals, explorations are often

insufficient to reveal fully all pervious strata that will be

intersected. Where pervious canal reaches are encountered,

an impervious lining should be considered provided that:

(1) suitable material is available, and (2) slope and right-ofway limitations will permit. If space limitations, availability

of suitable impervious materials, or other considerations

indicate a requirement for another type of lining, or for a

more expensive lining, appropriate authorities should be

consulted.

3-17. Unsuitable Foundation Soil Conditions.&

a. General.&Materials normally considered unsuitable

for foundations include: 

 ̆ Organic matter such as topsoil, swamp deposits, or

peat

 ̆ Low density materials such as loose deposits of silt,

sand, loess, talus deposits, spoil piles, and dumps

 ̆ Some clays classified as highly plastic, active,

sensitive, or swelling

 ̆ Soils in a soft and saturated condition

Whether a soil is deemed unsuitable depends upon several

factors. Most important is the type of structure being

contemplated. Another important factor is the geographical

location of the intended structure. For example, some soils

may be determined to be unsuitable in one climate, while the

same soils in another climate may be deemed undesirable or

even suitable depending upon the climate and the availability

of suitable soils. In other words, the shortcomings of a soil

can often be overcome through prudent design.

For most structures, unless the deposits of unsuitable

materials prove extensive, avoiding these materials for use

in structural support may prove economical and satisfactory.

The more common methods to avoid using unsuitable

materials include:

 ̆ Removal and replacement with compacted select

material

 ̆ Full penetration with piles, piers, caissons, or walls

 ̆ Displacement; that is, remove a mass of material

equal to the mass of the structure

If feasible, the structure can be relocated to provide better

soil conditions. Treatment with additives may also be

effective for some soils.

b. Topsoil.&As in borrow deposits, the usual practice

is to remove topsoil from below all foundation elements.

Topsoil in this sense is the surface layer of material

containing decaying vegetable matter and roots. Removing

all soil containing fine hairlike roots is unnecessary but is

required of the rather heavy root mat. On prairie topsoil,

which contain light grass cover 50 to 75 mm (2 or 3 in),

stripping will suffice. Agricultural lands are stripped to the

bottom of the plowed zone, usually 150 to 250 mm (6 to

10 in). Valley bottom lands and brush-covered land

commonly require stripping up to 0.6 or 0.9 m (2 or 3 ft)

for removal of inadequate material. Forest land requires

removal of stumps, resulting in stripping requirements of 1

or more meters.

c. Swamp Deposits.&Marshlands, river backwaters,

lakebeds, and flood flow deposits are included in this

category. Foundation soils formed by these deposits contain

appreciable quantities of vegetable matter, clay, silt, or sand

lenses deposited in water.

Shallow deposits should be removed; however, deposits may

be deep, and their depth and extent should be established

before adopting a method of treatment. Relocation is

recommended to avoid such deep deposits, particularly

where roads, canals, pipelines, or transmission lines are

involved. For dams, powerplants, and similar large

structures, such materials may be excavated and wasted or

used for topsoil; for bridges, pumping plants, and mediumsize structures&where a water barrier is not required&fully
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

233

Figure 3-8.—Cracking and settling of canal bank in dry, low-density silt.

penetrating piles are commonly used. Sometimes, adequate

structural performance can be obtained by excavation to

firmer material and placing and compacting a pad of select

material.

d. Silt and Sand.&While dense silt and sand deposits

generally will be satisfactory, low density deposits of these

materials may be undesirable. Usually, such low density

materials are found as surficial deposits occurring as loess,

sand dunes, sandbars in stream channels, alluvial fans, and

deltas at the head of reservoirs and lakes. The surface

layers of soil subject to frost action are low density in some

areas.

Low density, poorly-graded sand, silts, and gravels that are

saturated and located in an seismically active region are

highly susceptible to the phenomenon of liquefaction when

disturbed by vibration. Many slope and bearing capacity

failures have occurred during earthquakes because of

liquefaction in low density materials.

Loose sands and wet silts will consolidate quite readily when

loaded and may not require special treatment when used for

flexible structures such as road fills and canal banks up to

6 m (20 ft) high. However, dry, low density silty soils

require removal or prewetting to support a structure. Figure

3-8 shows cracking and settling of a canal bank in dry, low

density silt after filling the canal.

Foundation soils composed of low density materials and wet

silts must be removed for earth dams and for fills higher

than 6 m (20 feet). For foundation soils of dry, low density

silt, either removal or consolidation by ponding is required

as shown on figure 3-9. Consolidation of saturated sands

can be facilitated by draining water from the soil.

Rigid structures usually are not founded on loose silts and

sands. These materials are either removed or consolidated,

or footings or piles for the structures are extended to firmer

material. Normally, designs will show the method to be

used.

Where loose sands or silts occur in foundation soils of water

retention structures, such as canal banks and dams, lining or

cutoffs are indicated. Permeability and the value of water

are usually the basis for determining the need for treatment.

A long canal may require treatment for a soil condition that

would not need treatment for a short lateral construction.
EARTH MANUAL

234

Figure 3-9.—Ponding dry foundation of Trenton Dam in Nebraska.

e. Talus and Spoil Piles.&The term "talus" describes

the buildup of soil and rock debris at the base of a slope.

Generally, such deposits consist of low density materials

and seldom provide adequate support for any structure more

important than a simple roadway. The usual treatment is to

remove the talus. Excavations into talus deposits are likely

to be unstable if cut slopes are appreciably steeper than the

natural slope of the talus deposit.

The processes used for disposal of excess or unsatisfactory

materials in spoil piles are similar to the processes by which

talus deposits developed&so the two have similar

characteristics. Spoil piles and talus deposits should not be

used for support of any structure without thorough

investigations, testing, analysis, and design.

f. Highly Plastic Clays.&Clays that create foundation

problems have one or more of the following characteristics:

 ̆ plasticity indexes greater than 25 percent,

 ̆ colloid content greater than 20 percent,

 ̆ high sensitivity, and

 ̆ shrinkage and swelling characteristics as noted by

their tendency to shrink and crack when drying.

Also, a relationship appears to exist between moisture

content and strength of clays. Criteria for identifying

expansive clays are given in chapter 1.

g. Soft or Saturated Soils.&Almost any soil

foundation is reduced in quality when it contains large

amounts of water. An apparently firm dry foundation soil

may become unstable when saturated. Foundation soils

subject to saturation may be protected by either preventing

water from entering the soil through use of drains to divert

surface runoff or by removing water that reaches the soil

using underdrains, drainage blankets, or relief wells.

Structures whose foundation soils will be permanently

underwater are designed against hydrostatic uplift.

Because of the difficulty in preparing and inspecting soils

located beneath the water table. Typically, specifications

contain provisions that require dewatering of foundation

soils before excavation. However, some work in water is
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

235

generally necessary when constructing cofferdams, pump

sumps, and drains. These structures should be kept away

from planned excavation surfaces so the surfaces will not be

damaged by the construction or by the action of dewatering

facilities. Saturated materials can be damaged by permitting

an upward flow of ground water into the excavation or by

permitting heavy equipment traffic in the area.

3-18. Foundation Improvement Technology and

Dam Rehabilitations.&Undesirable foundation conditions

can sometimes be alleviated by treatment in place. New

technologies have been developed to remediate foundation

problems [6, 7]. As part of the safety of dams program,

Reclamation has had to re-examine many of its older

structures. These examinations have revealed foundation

concerns at many structures including excessive seepage and

possible piping; collapse of dry, low density abutment soils;

and potentially liquefiable soils during earthquake shaking.

Many dams have been rehabilitated using ground

improvement methods [8]. These ground improvement

techniques are also applicable to foundations for new

structures. This section contains a brief discussion on

several ground improvement methods, and their applicability

to new or existing foundations is given. For more details on

these technologies, consult references provided.

Each method of ground improvement has unique advantages

and disadvantages relative to the ground conditions

requiring improvement. In many cases, differing methods

can be combined to overcome disadvantages of the methods

and benefit from the positive aspects of each method. For

example, at Steinaker Dam, Reclamation desired to treat

dirty sands and silts with dynamic compaction. Wick drains

were used in combination with the dynamic compaction to

effectively treat those soils. Another example is Jackson

Lake dam where a block treatment approach was used.

Dynamic compaction was used for shallow treatment under

the center of the dam, while mixed-in-place, soil-cement

columns in a honeycomb pattern at depths up to 90 feet

were placed under the toes of the embankment. The use of

the two combined methods resulted in satisfactory ground

improvement to preclude liquefaction failure.

a. Slurry Walls.&Slurry walls can be used to provide

positive cutoff for new dams or can be installed to alleviate

seepage problems in existing dams. A deep trench is

excavated with various types of equipment, depending on

the depth and consistency of the soil or rock. The trench is

supported with bentonite or biopolymer slurry. Backfill

materials can range from soil/cement/bentonite (SCB)

mixtures to structural grade concrete. Often, slurry wall

backfill is designed with strength and deformation properties

similar to those of the surrounding soils. Material with soil

consistency can be excavated in long trenches with

backhoes, draglines, or clamshells (see fig. 3-10).

Clamshells can be used in a wider range of deposits and can

be used to excavate "cells" or "panels." Material with

rocklike consistency can be excavated with chisels or rock

mills with hardened cutterwheels. Rock mills are most often

used to make cells or panels for cutoff walls (fig. 3-11).

Reclamation has applied slurry wall technology to existing

dams and new dams. An interesting application of slurry

wall technology for a new dam was performed at Diamond

Creek Dike, where an embankment was built with a sand

core which was later cut with a slurry wall for installation

of a SCB backfill to provide the water barrier or "core"

zone in the dike. This construction method was selected due

to a shortage of clay borrow and to accelerate embankment

construction.

Design considerations for slurry wall applications should

include determination of the geologic and geotechnical

conditions, establishment of the hydraulic conditions,

requirement of the design flow per unit surface area,

determination of the wall size and geometry, and design and

determination of the properties of the backfill material. 

Quality control issues with slurry walls include verticality,

caving, foundation contact and connection of panels or cells,

permeability, compressive strength, and voids or windows

[9]. Additional quality control issues include excavation and

repayment balance, width and depth measurements, and

cleaning of foundation contacts. During construction of

slurry walls, sounding devices can be dropped into the

slurry to sound the width of the trench to determine if

caving has occurred. Fresh SCB backfill material cylinders

may be cast for compressive strength testing. The heat of

neutralization test can be used to check cement contents

[10]. Samplers can be used to check for clean foundation

contact conditions prior to backfilling. Drilling, water

testing, and drill coring programs are often employed to

check backfill quality. However, if the backfill material is

weak (less than 200 lb/in2 (1400 kPa), core recovery may

be difficult and precautions must be made to avoid wall

fracture. Cross borehole tomographic P wave imaging can

be used to look at wall integrity and guide investigations. 

b. Fill Loading with Sand or Wick Drains.&Fill

loading has long been used to consolidate soft silty and

clayey deposits for embankments. The time required for

consolidation can be determine by consolidation theory. In

past practice, vertical sand drains were constructed to

accelerate the process. Recently, synthetic wick drains have

been developed to replace sand drains. The wick drains are

plastic drainage elements enclosed in a filter fabric. Wick

drains are installed by vibratory pile driving equipment.
EARTH MANUAL

236

Figure 3-10.—Schematic drawing showing slurry wall construction methods—backhoe and

clamshell excavation and surface backfill method. (Hayward Baker, Inc.)

These drains are also a useful complement to other

densification methods such as dynamic compaction.

Design considerations for wick drain application include

establishing the geologic/geotechnical site conditions,

determination of the driving and installation methods, testing

of undisturbed samples for consolidation rates and strengths,

determination of proper spacings, depths, and types of drain

elements, and determination of the required foundation

properties and fill loading times.

Quality control testing depends on the application. For fill

loading to improve soft clays, piezometers are often

installed to measure excess pore pressure dissipation over

time. Field strength tests, such as vane shear or lab tests,

can be used determine strength gain over time. When

drains are combined with other ground improvement

methods, there may be no quality control test needs other

than assurance of proper placement. 

c. Dynamic Compaction.&Dynamic compaction can

be a relatively low cost method for increasing the densities

of foundation soils. Dynamic compaction has been used to

treat low density, potentially liquefiable and collapsible

soils. Weights (steel or concrete) of up to 35 tons are

repeatedly dropped from heights of up to 30 m (100 ft) in a

pattern across a site to create high intensity surface impacts

(fig. 3-12). Cranes are generally modified from standard

configuration to accommodate the heavy weights used to

perform dynamic compaction. Weights are dropped in

patterns and sequences until densification is judged to be

sufficient There are a number of case histories documenting

the use of deep dynamic compaction to remediate

seismically sensitive embankment foundations [11].

Effective treatment depth is usually limited to depths

between 9 and 10 m (30 and 35 ft), depending on foundation

soil types, ground-water conditions, site geometry, weight

drop patterns, equipment, and equipment sequencing.

Dynamic compaction is typically used at sites with

nonplastic materials. The potential for effective treatment

becomes less for sites having soil horizons with high fines

contents (greater than 20- to 30-percent fines). Effective

treatment of sites having soils with high fines content can be

achieved by installation of wick drains or other drainage

features prior to deep dynamic compaction. 

Design considerations include determination of the

geologic/geotechnical conditions, evaluation of water control

for working pad, procuring backfill material, determination

of the drop weight, height and pattern, and determination of

monitoring parameters such as penetration resistance testing.

Quality control issues include crater depths (mapping),

surface heave or settlement monitoring, hammer energy,

pore water pressure buildup, and vibration monitoring.

Control testing for dynamic compaction can include load

testing, piezometric monitoring, penetration testing, shear

wave velocity determinations, and soil sampling for

evaluation of engineering properties. 
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

237

Figure 3-11.—Slurry wall construction using panel excavation and tremie placement—view of a hydromill and 

crane with 75-cm (30-inch) x 3-m (10-ft) clamshell—Twin Buttes Dam modification.
EARTH MANUAL

238

Figure 3-12.—Photograph of dynamic compaction showing crane, weight, and impact pattern (Hayward

Baker, Inc.)
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

239

Figure 3-13.—Schematic drawing of vibro-replacement—backfill can be added by top feed

(illustrated) or bottom feed methods. (Hayward Baker, Inc.)

d. Vibratory Densification.&There are many forms of

vibratory densification which can be used to improve

foundation conditions. These include vibro-compaction or

-replacement, vibrating probes (vibrating rods with small

diameter columns), and blasting. 

1. Vibro-Compaction/Replacement (Also Known

as Vibroflotation and Stone Columns).&Loose foundation

soils at some damsites may be densified for low to moderate

costs by inserting a type of vibrating tube or probe into the

foundation at a variety of depths and locations across the site

(fig. 3-13). Water and/or air jets may be used to aid

insertion of the vibratory probe and densification of

surrounding soils. The effectiveness of these vibrocompaction methods depends upon soil type (gradation) and

depth, spacing of treatment, vibration levels, backfill added

(if any), and pore pressure response during treatment. In

general, these methods are effective in treating cohesionless

soils with less than 20 percent fines [7]. For soils higher in

fines content, stone columns are used to improve the soil.

In the vibro-replacement method, sand and/or gravel can be

introduced into the foundation during the compaction

process, which displaces and intrudes into soils around the

probe, resulting in densification of foundation soils.

Introduction of sand or gravel can also improve pore

pressure dissipation and improve shearing resistance of the

treated zone. The probe is repeatedly withdrawn and

inserted at the point of treatment to maximize foundation

improvement. This process results in construction of a

"column" in the foundation, the characteristics of which

vary with the nature of the treated materials and those

introduced during construction. Columns are typically

constructed in triangular or rectangular grid patterns, at

center-to-center spacings of 1.5 to 3 m (7 to 10 ft), and are

generally 1 m (3 ft) or greater in diameter. 

Vibro-compaction and replacement methods using water can

have substantial containment and/or cleanup costs during the

construction, compared to dry methods. It may be

necessary to handle large quantities of excess mud, water,

silt, sand, and gravel, depending on the final construction

methods specified, foundation and construction material

types, ground-water conditions, and site surface

characteristics. 

2. Vibrating Probes (Small Diameter Vibratory

Columns/Drains; i.e., TerraProbes, Vibrorods, Vibrowing).&Small diameter [less than 0.5 m (1.5 ft)] columns

or drains may be constructed in loose soils, densifying them

through displacement, vibration, and the introduction of

sands or gravels in the process. In addition to densifying

surrounding soils, the small diameter columns that result

also improve pore pressure dissipation and provide some

increase in shearing resistance. Columns are usually spaced

on close centers, generally less than 1 m (3 ft), in

rectangular or triangular patterns. This method is moderate

to high cost when compared to other foundation

improvement methods. As the depth of required foundation

increases to around 21 m (70 ft) or greater, this method may

become more cost effective as equipment limitations begin

to impact the effectiveness of other methods.
EARTH MANUAL

240

There is little data available to evaluate the performance of

dam foundations remediated by this method. There no are

data from testing of posttreatment hydraulic conductivity in

treated foundation materials versus embankment

performance during earthquake shaking. Posttreatment

testing of dam foundation densities has also not been

completed. Therefore, this method should generally be

considered as an economical secondary defensive design

feature, counting primarily on the columns to improve pore

pressure dissipation during an earthquake. Series of

columns can be used adjacent to areas treated by other

methods to prevent high pore pressures from adjacent

untreated areas from adversely affecting the treated zone.

This method has been used in the design and construction of

seismic remediations for Mormon Island Auxiliary Dam

near Sacramento, California. Typical control tests for

verification are penetration resistance tests, shear wave

velocity, and undisturbed soil sampling.

Design considerations for vibratory ground improvement

methods should include determination of the geology and

geotechnical properties, establishment of ground

improvement requirements, selection of optimum vibratory

ground improvement method(s), evaluation of ground

settlement, determination of backfill properties and location

of backfill sources, and establishing baseline data for quality

control testing.

Quality control issues for vibratory ground improvement

include column locations, spacing and verticality, energy

input required, and quantities of backfill placed.

Acceptance testing for vibratory ground improvement is

primarily based on penetration resistance testing, standard

penetration tests, cone penetration tests, or Becker

penetration tests. Improvement in shear wave velocity can

be determined. Undisturbed samples can be procurred to

evaluate density and moisture changes. Stress levels and

modulus changes can be evaluated with a flat plate

dilatometer or pressuremeter. It is wise to never base

acceptance on a single test. Acceptance should be based on

average properties, not minimum or maximum properties.

3. Blasting.&Blasting, when used as a foundation

improvement method, densifies soils as a result of shock

waves, vibration, limited liquefaction, displacement,

remolding and settlement in the treated soils. This is a

relatively low cost foundation improvement method but

results in nonhomogeneous soils may be erratic. It is also

difficult to assess any potential damage that may occur to,

or beneath, an existing embankment or an appurtenant

structure. The use of blasting as a foundation improvement

method is much more likely to be practicable for sites prior

to construction of a new embankment. An example of

blasting at the Jebba damsite is given in the references [12].

This method has been used in ground improvement projects

where rubble and large boulders preclude the use of other

vibratory methods.

Design considerations for blasting should include

determination of geology and geotechnical properties;

evaluation of charge size, burial depth, charge spacing,

number of coverages, and surface settlements; evaluation of

required performance parameters; evaluation of blasting;

and vibration safety requirements.

Typical verification testing includes piezometric

measurements, penetration resistance tests (SPT, CPT,

BPT), shear wave velocity determinations, and undisturbed

sampling. Settlement is usually monitored.

e. Grouting and Soil Mixing.&Numerous technologies

exist for grouting and soil mixing in ground improvement.

The most common of these technologies include compaction

grouting, jet grouting, and soil mixing [13].

1. Compaction Grouting.&This method of soil

densification utilizes a low slump mortar grout (usually 0 to

50 mm (0 to 2 in), that is injected under high pressures (2.1

to 4.8 mPa, 300 to 700 lb/in2

), to form a series of grout

bulbs that displace and compact loose foundation soils

between and adjacent to the bulbs. 

The cost of compaction grouting, when compared to other

methods of foundation improvement, is moderate to high.

The relative cost of compaction grouting becomes more

economical when treating identifiable thin lenses or layers

where treatment of competent overlying layers is not

required, or in small areas adjacent to structures. 

Compaction grouting is often used in tunneling and

underpinning operations for settlement and deformation

control. The method is rarely used in the construction of

earth dams but has been used to remediate older dams.

Prior to selection of compaction grouting for ground

improvement associated with dam embankment foundations,

the following issues need to be considered:

 ̆ Compaction grouting may not be practical on the

downstream side of an embankment since a series of

impermeable grout bulbs, while not interconnected,

might impair drainage in the downstream direction.

This could adversely impact embankment stability

during static or dynamic loading. 

 ̆ For remedial seismic designs of embankments that

might use compaction grouting as a method of
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

241

Figure 3-14.—Schematic drawing of jet grouting process showing 

construction of columns. (Hayward Baker, Inc.)

foundation treatment, it is recommended that

compressive strengths and shearing resistance

provided by grout bulbs should be carefully

evaluated. How the individual grout bulbs respond in

treated dam foundation materials during strong

seismic shaking is presently not well understood.

Design considerations for compaction grouting should

include definition of the geotechnical parameters and

structure interaction considerations, location of the

compaction zones, definition of densification parameters,

estimation of grout volumes required, and development of

a plan for sequencing along with monitoring programs.

Quality control testing includes monitoring of grout

consistency (slump and compressive strengths), pressures

and volumes injected, and measurement of ground heave.

On critical programs, site-specific evaluation of grout bulb

effectiveness may be made. After installation, settlement is

monitored and the improvement in soils adjacent to the

columns can be monitored with penetration tests (SPT,

CPT). Increases in stiffness and horizontal stresses can be

monitored by flat dilatometer and pressuremeter tests. 

2. Jet Grouting and Deep Soil Mixing.&Jet

grouting is performed in foundation soils by high pressure,

and high velocity jets of water and/or air, which "excavate"

the materials, inject them, and mix them with some type of

stabilizer (fig. 3-14). This procedure can be used to

construct columns of improved soil in a wide variety of

foundation soil types (gravels, sands, silts, and some clays).

Columns and panels can be interlocked to form walls, to

cutoff/reduce seepage through a foundation, or form cells

within a potentially liquefiable foundation. The cost of jet

grouting can be relatively high when compared to costs of

other foundation improvement methods, depending on the

design goals of foundation remediation and the distribution

and type of soil to be treated. 

Deep soil mixing methods can also be used to construct

columns, walls, or cells of fairly precise final dimensions,

in materials ranging from sand to clay. This method utilizes

hollow stem auger flights and mixing paddles, which are

advanced into the soil, while grout is pumped through the

tip of the auger. The auger flights and mixing paddles mix

the grout with the surrounding soils during penetration to

design depth and withdrawal. The cost of deep soil mixing

relative to that of other foundation improvement methods is

moderate to high.

Jet grouting or soil mixing methods may introduce

impermeable elements into the dam foundation that may

adversely affect embankment stability (especially on the

downstream side of a dam). In several cases, these methods

have been used as cutoff wall elements for dams. In seismic

strengthening applications, the stress-strain compatibility of

the columns with encapsulated or adjacent foundation soils

is poorly understood (use of compressive strengths or

shearing resistance should be closely scrutinized in any

analysis). Finally, ground motions reaching an embankment

may be amplified through these stiffer elements, resulting in

stronger shaking of the dam. 
EARTH MANUAL

242

Design considerations for jet grouting and soil mixing

include determination of the range of soils to be treated,

required stabilizing additive dosage through trial mix design

studies, reasonable strengths and permeability that can be

obtained, treatment areas and depths and volumes, and

required performance parameters and quality analysis and

control monitoring plans.

Typical field testing consists of either waste or fresh column

sampling of the soil additive mixture. Waste sampling can

provide insight as to volume of the treated area and

conservative assessment of in situ characteristics. Core

samples are often procurred from cured columns, and

compressive strength is evaluated. Water testing can be

performed in boreholes, but there are often problems with

proper location of the holes for reliable tests. Records of

treatment methods (columns installed, volumes injected) are

maintained to monitor production and document

construction.

D. Embankment Dams

This section provides information according to Reclamation

practices in the early 1990s. Clearly, the designer acquires

expertise as knowledge and experience develops, technology

advances, and investigation and construction practices

improve. Reclamation publishes a series: Design Standards

No. 13&Embankment Dams; it is periodically updated and

reflects the latest technology. Design Standards No. 13

should be consulted for detailed information on the aspects

and components of embankment dams [14].

3-19. Foundation Treatment.&

a. Design Features.&An embankment dam is often

the most feasible type of structure for a particular damsite

because of relatively poor foundation conditions that are

unfavorable for rockfill or concrete dam construction.

Embankment dams are frequently founded on alluvial

deposits that consist of layers of varying thickness of coarse

sand and gravel, silts, or clays before bedrock is reached.

Deeply weathered or faulted rock may also be encountered

in embankment dam foundations. Foundations of thick

deposits of windblown silts and fine sands present especially

difficult problems. Foundation design must consider three

main problems: (1) seepage, (2) stability, and (3) control of

deformation.

Cutoff trenches, cutoff walls, or combinations of trenches

and walls are most commonly used in foundations of

permeable materials. These cutoffs are designed to stop the

flow of seepage water or to lengthen the path of percolation

under the dam. Blankets of impervious material that extend

upstream from the impervious zone of a dam on the

reservoir floor and cover all or part of the abutments are

sometimes used for lengthening the percolation path.

Cutoff features are typically located at or upstream of the

centerline of the crest of the dam beneath the impervious

zone of the embankment. The location and design of the

cutoff feature should provide an adequately long percolation

path through both the embankment and the cutoff feature.

Where the embankment is founded on or near bedrock,

"curtain" grouting and "blanket" grouting are usually

necessary to extend the cutoff into rock. Closing of joints

and other openings in bedrock is usually necessary and is

accomplished by injecting grout (under pressure) to form a

curtain cutoff. Comparatively shallow low-pressure

grouting ("blanket grouting") may be used to seal near

surface fractures in the rock beneath the impervious

foundation area.

Two general types of cutoff trenches are (1) sloping-side

trenches and (2) vertical-side trenches. Depth, location, and

type of cutoff trench used depend on the nature of

foundation materials and on their permeability. Common

practice for foundations, with bedrock at a shallow to

moderate depth, is to excavate a sloping-side trench located

at or upstream from the centerline of the crest of the dam.

For trenches located upstream, the trench centerline

parallels the centerline of the dam crest across the valley

floor but converges toward the crest centerline as it extends

up the abutment so that the cutoff is fully beneath the

impervious zone of the embankment. When bedrock or an

impervious stratum is relatively close to the surface, the

cutoff trench may be widened to the full width of the

impervious zone of the embankment. Sometimes, the entire

embankment is founded on bedrock when the top of bedrock

is located at a shallow depth. Where bedrock cannot be

reached economically, the cutoff excavation is extended

either to a stratum of relatively impervious material or to a

depth that will provide the desired length of the seepage

path. Care must be exercised when analyzing a dam

foundation to ensure that liquefiable materials are not left in

the foundation.

Sloping-side cutoff trenches are excavated using front-end

loaders, shovels, backhoes, draglines, or scrapers. The
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

243

excavation is backfilled with selected impervious materials

equivalent to the impervious zone in the dam embankment

and compacted in the same manner as rolled earthfill

embankment material. Properly designed filters and

transitions must be provided between the downstream face

of the cutoff and alluvium (or rock surfaces) to preclude any

piping into foundation alluvium (or bedrock). Rock

surfaces must be shaped to provide gradually changing

surfaces and must be treated to seal fractures ([14], ch. 3).

Vertical-side trenches may also be used as cutoffs. In some

instances, the depth of a sloping-side cutoff trench may be

extended by continuing the excavation as a narrow trench

with vertical side walls. Vertical-side cutoff walls require

special design and construction techniques where the two

types of trenches are connected or where the wall connects

to the base of the impervious zone. Sometimes, verticalside cutoff walls are used near the upstream toe of a dam or

in conjunction with upstream impervious blankets in which

case they must be connected to the impervious zone of the

dam. Use of cutoff walls has increased in recent years

because of improved technology and construction

techniques. There are basically three types of vertical-side

cutoff walls: (1) soil-bentonite slurry-trench cutoff wall,

(2) concrete cutoff wall, and (3) cement bentonite/plastic

concrete cutoff wall (see sec. 3-18a).

In addition to forming cutoffs, concrete walls are sometimes

used to treat certain geologic features such as faults or

fractured zones. Particular geologic features may require

placing short, independent wall sections at certain locations

on the abutments or within the river channel. Concrete

cutoff walls may be required:

 ̆ When bedrock is hard, but intensely fractured and

irregular

 ̆ For bedrock dipping steeply, especially on the

abutments

 ̆ Across shear or fault zones

 ̆ Across weathered zones

Careful consideration must be given to foundation contacts

in the design of an embankment. Any continuous void

spaces caused by lack of intimate contact between the

impervious portion of the embankment and the foundation

may result in dangerous seepage. Overhanging rocks and

undesirable material should be removed; slopes should be

flattened and smoothed to permit embankment materials to

bond properly to the abutments. In thin core dams, the

impervious section may be widened at the points of contact

with the abutments.

Foundation grouting is a process of injecting suitable

grouting materials into the underlying foundation through

specially drilled holes of seal or fill joints, bedding planes

seams, fissures, or other openings. Grouting may be done

with neat cement (the most common method), mixtures of

cement and sand, or cement mixed with bentonite or other

clay. In special cases, chemical or bituminous grouting may

be used. The adopted program may consist of grouting

along a specified line or multiple lines to create a deep,

relatively impermeable curtain; comparatively shallow or

"blanket" grouting over wider portions beneath the

impervious zone of the foundation area; or both. Every

foundation presents a unique grouting situation that depends

on composition and nature of the material and on the

geologic structure. Figure 3-15 is a geologic section of an

abutment of a dam showing a grout curtain.

In foundations of unlithified permeable materials, the path

of percolation can be increased by constructing a blanket of

compacted impermeable material upstream of the dam.

Blankets are usually used when cutoffs to bedrock&or to an

impervious layer&are uneconomical because of excessive

depth. Sometimes, they are used in conjunction with

partially penetrating trenches designed to increase the length

of the path of percolation. The topography just upstream

from a dam and the availability of impervious materials are

important factors in the design of blankets. The length of

upstream extension is determined by desired reduction of

volume of seepage and of hydraulic gradient. In zoned

embankments, the blanket must extend beneath the upstream

shell as a continuation of the central, impervious section.

Blankets may be constructed to cover either or both

abutments or particular abutment areas. The blanket

thickness will vary with permeability of the material and

with the head of water. Filters may be necessary to prevent

piping of the impervious blanket layer into the foundation.

Methods for improving foundation stability include:

 ̆ Removal of unsuitable material

 ̆ Preconsolidation by dewatering or by irrigation and

loading

 ̆ Adequate drainage of the downstream toe by means

of drainage blankets and filters, toe drains, and relief

wells to avoid piping and to reduce hydrostatic

pressures

 ̆ Construction of stabilizing fills to prevent

displacement of the foundation

 ̆ In place densification

The minimum requirement for foundation stripping is

removal of vegetation, sod, topsoil having high organic

content, and other unsuitable material that can be removed
244

Figure 3-15.—Curtain grouting in right abutment of New Waddell Dam in Arizona.
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

245

by opencut excavation. In cases where overburden is

comparatively shallow and composed of soft clays, loose

fine sands and silts, or extremely pervious sands and

gravels, or liquefiable materials, the entire foundation area

of the dam may be stripped to bedrock.

In special cases, water may be added to the foundation by

irrigation to cause consolidation. Dry loessal (wind

deposited) soils and other low density silty soils have been

successfully treated by this method. Sometimes, the entire

foundation area is saturated and preloaded to cause

consolidation and stabilization of otherwise unsuitable

foundation materials when the cost is less than the

alternative of excavating and replacing the material with

selected borrow material. Usually, such treatment is

accomplished by staged construction of the embankment.

Loose, fine sand deposits below ground-water table have

been successfully consolidated by deep compaction

techniques such as compaction piles and dynamic

compaction&usually in conjunction with dewatering.

Sometimes, these procedures are used to treat liquefiable

sands and silts (see sec. 3-18).

The purpose of dewatering is to permit construction in the

dry and to increase the stability of excavated slopes. Clean,

coarse to medium sands can be readily dewatered. Clean,

fine sand can be dewatered with some difficulty. Dirty,

fine, medium, and coarse sands are difficult to dewater.

Silts and clays require extraordinary methods to dewater.

Usually, dewatering consists of drains, drains with sumps,

deep wells, and wellpoints either alone or in combinations

for maximum effectiveness [15]. Dewatering shall maintain

a sufficiently low water table to allow for satisfactory

excavation and backfill placement. Dewatering systems

must be carefully designed to ensure the adequacy of the

system. If sufficient effort is not made in dewatering,

foundations can be damaged, excavation safety can be

jeopardized, and costly construction delays can occur.

Reclamation has taken a proactive approach of designing

their own dewatering schemes in certain critical situations to

avoid costly construction delays.

Preventing all seepage under a dam is not possible.

Inevitably, water will escape somewhere in the vicinity of

the downstream toe. When foundation materials in that area

consist of or contain appreciable quantities of fine sands,

silts, or clays that may be carried away&by water escaping

under pressure&a filter or drainage blanket is provided.

The filter is constructed of selected materials designed to

satisfy filter criteria. The filter allows the necessary passage

of water but prevents movement of fine soil particles from

the foundation. A filter design accounts for grain sizes of

foundation soils and head loss. Two, or more, layers of

different sizes of sand and gravel may be required to prevent

piping and to provide adequate drainage capacity. Another

method to relieve hydrostatic pressures near the downstream

toe of an embankment or high pressures beneath impervious

foundation layers in the vicinity of the downstream toe is by

installing vertical relief wells. The purpose of the wells is

to relieve excess water pressure in the foundation, and

thereby prevent formation of boils and heaving or piping.

Toe drains are commonly installed in a trench along the

downstream toe of a dam as part of the filter or drainage

blanket to collect and convey water to measuring devices.

Perforated concrete, high density polyethylene, or other

types of pipe may be used for the drains. Beginning with

small diameter pipe laid along abutment sections, the lines

progressively increase in size; with lines of maximum

diameter being placed across the valley floor. Toe drain

pipe must be laid in a trench of adequate depth and grade to

be effective. Drainpipe is encased in a filter (usually sand)

and drain material (usually gravel) to prevent piping of

surrounding material into the drain. Access points should

be installed along the drainpipe and outlet line for inspection

and maintenance and, if desirable, at other locations for

observation and measurement of the amount of seepage

water and detection of any piping. The function of drains

is to allow uninhibited escape of seepage water, thereby

preventing saturation and consequent reduction of stability

of the downstream embankment and foundation of the dam.

Toe drains, placed sufficiently deep in the foundation keep

the ground-water level low, preclude high exit gradients,

and prevent formation of boggy areas near the downstream

toe of a dam.

To make foundations of low strength materials suitable as

support for a dam, stabilizing fills are often used to provide

mass at the upstream, downstream, or both toes of a dam.

These fills act to restrain foundation materials from

displacing under load by increasing the normal effective

stress across potential failure surfaces. The depth and

extent of these fills depend on the properties of the

foundation materials. Stabilizing fills are generally

contiguous and integral with embankments.

b. Specifications Provisions.&During construction,

diversion and care of the river (stream, or surface runoff) is

an important factor in the design of an embankment dam.

Figure 3-16 shows a temporary diversion channel through

an embankment dam. Specifications require that the

contractor' s plan for diversion be approved, or the diversion

plan should be provided in the specifications. 
EARTH MANUAL

246

Figure 3-16.—Temporary diversion channel through Bonny Dam, Colorado.

Underwater excavation for the foundation of a rolled

embankment dam is not permitted. The contractor is

required to unwater the foundation in advance of excavating

an embankment cutoff trench. The unwatering is required

to be accomplished in a manner that will:

 ̆ Prevent loss of fines from the foundation

 ̆ Will maintain stability of the excavated slopes and

bottom of the cutoff trench

 ̆ Will result in all construction operations being

performed in the dry

Dewatering is to be continuous until the excavation has been

filled, except that in filling the cutoff trenches, the ground

water may be permitted to rise within 1.5 m (5 ft) of the top

of the compacted embankment after at least 3 m (10 ft) of

fill have been placed in the dry. This provision enables the

contractors to remove the majority of well points if they use

that type of dewatering process. Usually, it is impractical

to prevent water from seeping out along the contact of the

cutoff trench slopes with the foundation. Hence, some

surface drains are needed to ensure that backfill is placed in

the dry. Open-jointed or perforated pipe drains surrounded

by gravel and leading to sumps can be used to dry up the

foundation contact. Placement of drains that will be left in

place should be very carefully controlled and must be

meticulously filled with grout to avoid leaving any potential

leakage paths. The layout of these drains should be

carefully planned so that the contact of the impervious zone

is never penetrated, transversely, by more than one-third of

its width. The distance between the ends of transverse

drains from opposite sides of the impervious zone should be

no closer than one-third the width of the pervious contact.

The requirements for excavation of embankment foundation

provide that the area to be occupied by the embankment

shall be excavated to a sufficient depth to remove all topsoil,

rubbish, roots, vegetable matter of every kind, and all other

perishable or objectionable material that might interfere with

proper bonding of the embankment with the foundation.

Earth foundation surfaces are to be prepared by leveling and

rolling in the same manner as specified for placing

embankment materials. Rock foundation surfaces are to be

cleaned of all loose and objectionable materials. Foundation

surfaces of shale and other materials that tend to slake or

loosen on contact with air are to be cleaned just before

placing earthfill materials or protected from moisture

change. All foundation surfaces are to be moist but free
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

247

from standing water. Figure 3-17 shows a foundation being

prepared by excavation and water jetting to remove loose

rock and to smooth the impervious foundation prior to

placing earthfill.

c. Control Techniques.&The weak points in

embankment dam construction are generally found within

the foundation at the foundation contact with the

embankment and at the contact of the natural ground surface

with placed embankment. Construction of foundation

seepage control and stability features included in the design

must be carefully supervised by the inspection force to

ensure compliance with specifications. Dewatering methods

used in connection with the excavation of cutoff trenches

and for stabilizing foundations should be carefully checked

to verify that fine material is not being washed out of the

overburden materials because of improper performance of

drainage wells. To avoid creation of a "live" bottom due to

upward flow of water, continuous pumping may be

required.

Where overburden is stripped to firm material, the

foundation surface (including all pockets or depressions)

should be carefully cleaned of soil or rock fragments before

placing the embankment. This may require handwork water

or compressed air-water cleaning or both. Cleaning is

particularly important beneath the impervious zones.

Surfaces that disintegrate rapidly on exposure should be

covered immediately with embankment material or an

approved protective covering. If stripping operations

indicate the presence of unstable or otherwise unsuitable

material, test pits should be excavated for further

exploration, and generally this material will require

removal.

Before placing the first layer of impervious zone material on

an earth foundation, the foundation surface should be

leveled, moistened, and compacted. Foundation surfaces of

firm material should be moistened, but standing water

should not be permitted when the first lift is placed. An

earth foundation surface may require scarification by disks

or harrows to ensure proper bonding. When the foundation

can be penetrated by tamping roller feet, scarification is not

usually necessary. Where the surface would be damaged by

penetration of the tamping-roller feet, a thicker layer of

earthfill may be permissible for the first compacted layer, or

the first layer may be compacted with rubber-tired

(pneumatic) rollers. However, the first layer should not

exceed a thickness that will prevent attainment of the

specified density and should never exceed 400-mm (15-in)

loose lift. When thicker lifts are placed, additional roller

passes are usually required to ensure that proper compaction

is attained. Special compaction methods should be used in

pockets that cannot be compacted by the specified roller

instead of permitting unusually thick first lifts to obtain a

uniform surface for compaction. Figure 3-18 shows

compaction of earthfill (zone 1) near the foundation contact

with a pad foot roller at Reclamation' s Jordanelle Dam,

Utah.

On steep, irregular rock abutments, wetter-than-optimum

material may be necessary or desirable to obtain complete

and proper bond. The rock surface should be properly

moistened. Rock abutments should be shaped by excavation

or dental concrete to allow compaction by pneumatic tire

equipment or rollers directly against the contact. The fill

surface should be sloped or ramped to about 1v:6h near the

foundation surface to direct the force of the pneumatic roller

wheel towards the foundation surface. Tamping by hand

operated equipment should be avoided. If absolutely

unavoidable, when hand-held compactors are used, care

must be exercised to ensure that bond is created between

successive layers of material. This may require light

scarification between lifts of tamped material.

3-20. Compacted Earthfill.&

a. Design Considerations.&Rolled embankment dams

vary considerably in proportion and physical characteristics

of soils from which they are constructed. Some dams

contain essentially one kind of material and are called

homogeneous impervious structures, while others are

constructed of zones of sand, gravel, rockfill, and

miscellaneous soils in a variety of quantities and locations

within the fill, in addition to an impervious zone. The

impervious materials include clays (CL and CH), clayey

sands or gravels (SC or GC), and silty clays (CL-ML).

Occasionally, more pervious materials such as silts (ML)

and silty sands or gravels (SM or GM) are used in the

impervious zone. This impervious zone of earthfill, usually

designated zone 1 in Reclamation dams, provides the water

barrier and is common to all rolled embankment dams.

Homogeneous dams are virtually nonexistent in modern day

dam engineering&for dams of any size. Internal filters and

drains are always provided except for extremely small dams.

In controlling construction of impervious earthfill zones, the

following design criteria must be satisfied:

(1) The material must be formed into an essentially

homogeneous mass free from any potential paths of

percolation through the zone or along the contacts with

the abutments or concrete structures.

(2) The soil mass must be sufficiently impervious to

preclude excessive water loss through the dam.
EARTH MANUAL

248

Figure 3-17.—Foundation preparation for the impervious (zone 1) foundation at Jordanelle Dam, Utah. The workman near

the backhoe is using a high pressure mixture of air and water. The backhoe has a metal plate welded across its bucket teeth

to provide a smooth edge for scraping. Inspector in right center, and impervious fill shown in foreground (July 1990).
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

249

Figure 3-18.—Earthfill (zone 1) compaction by a model 925 C Caterpillar pad foot roller. 

Also, notice filter upstream of zone 1 being compacted by a vibratory roller. Filter is over

weathered fracture zones in the foundation rock (July 1990).
EARTH MANUAL

250

(3) The material must not consolidate excessively under

the weight of superimposed embankments.

(4) Differential settlement that would cause shear planes

must be avoided.

(5) The soil must develop and maintain its maximum

practicable shear strength.

(6) The material must not consolidate or soften

excessively upon saturation.

These design objectives are achieved by proper use of

equipment and methods of borrow-pit conditioning,

excavating, placing, compacting, and foundation shaping.

To satisfy design criteria of imperviousness, low

consolidation, and resistance to softening, a high density is

desirable. However, to control development of pore

pressure&which would reduce shear strength&and to avoid

formation of slickensided layers, which may become paths

of percolation, material that is too wet must be avoided.

Based on knowledge of available materials gained from

exploration and testing, the designer will specify moisture

control requirements near laboratory optimum moisture

content. The inspector should observe the fill placement

operation to ensure that specifications requirements are

satisfied and that an adequate fill is obtained. The plan of

control of the impervious earthfill for high dams must be a

compromise that will result in a proper balance among all

the design criteria. Experimentation with different

moisture-density control procedures may be necessary to

obtain proper deformation properties of earthfill (zone 1).

For example, the California Department of Water Resources

compaction control procedure was used at New Waddell

Dam, Arizona to obtain deformation properties slightly

stiffer than standard Reclamation laboratory tests would

have yielded.

b. Specifications Provisions.&The specifications for

open cut excavation require that all suitable excavated

materials shall be used for permanent construction.

Materials suitable for earthfill must be excavated separately

and in the same manner as those fill materials excavated

from borrow areas. Provisions are made for direct

placement of materials in the embankment or for

stockpiling.

The specifications designate which borrow areas to use for

earthfill material and provide Government control for both

location and extent of borrow activity to obtain suitable

materials. Designated borrow pits within a borrow area are

required to be cleared and stripped of unsuitable material

and are to be irrigated or drained to obtain the proper water

content before excavation. The contracting officer

designates the depth of cut in all borrow pits; the

contractor' s operations must be such that earthfill material

delivered on the embankment is equivalent to a mixture of

materials obtained from an approximately uniform cutting

from the face of the borrow-pit excavation. When

necessary, separation of oversized material from the earthfill

is specified.

The specifications prohibit placing frozen soil in the

embankment or placing unfrozen material upon frozen

embankment. The maximum allowable difference in

elevation between zones during construction is specified.

The Government controls all openings through the

embankment, limits the slopes of bonding surfaces, and

requires careful preparation of sloping surfaces before

additional material is placed. Slopes of bonding surfaces in

earthfill material usually are limited to 4h:1v or flatter.

Each load of embankment material must be placed in the

location designated by the Government. 

Specifications provide for placing earthfill only on

dewatered and prepared foundations. All cavities within the

foundation area are to be filled. Materials to be used for

earthfill are described. In placing earthfill, distribution and

gradation of material must avoid lenses, pockets, streaks, or

layers that would prevent homogeneity of the fill. If the

earthfill material contains only occasional cobbles or rock

fragments, provisions are made to remove such cobbles or

rock fragments over 125 mm (5 in) from the fill before

rolling. When an appreciable percentage of oversize is

known to exist in the source of earthfill material, a

separation plant is specified, as shown on figure 3-19.

When a separation plant is required, separation may be

specified on either the 75- or 125-mm (3- or 5-in) size.

Earthfill placement is to be in approximately horizontal

layers not more than 150 mm (6 in) in compacted thickness.

Fill surfaces that are too dry or too wet are required to be

reconditioned before additional materials are placed.

Moisture control provisions of earthfill require uniformity

of water content throughout the entire layer before and

during compaction. Water content of a soil is limited to a

range based on design considerations. In general, the

average water content will be near the standard Reclamation

laboratory optimum moisture content or, in some cases,

near optimum of an alternative moisture-density control test

such as the California Department of Water Resources

compaction test. The contractor is required to perform all

operations necessary to obtain the proper water content by

irrigating or draining borrow pits, by performing

supplementary sprinkling on the fill, and by working the

material in the borrow area or on the fill prior to

compaction.
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

251

Figure 3-19.—Separation plant at Meeks Cabin Dam in Wyoming.

Tamping (sheepsfoot) rollers are generally required for

compacting earthfill. However, many other acceptable

rollers have recently been developed and used. If a roller

other than the specified roller is proposed, a test fill should

be constructed to ensure that the proposed roller will

perform adequately. Normally, the tamping roller is still

specified. The size, mass, feet arrangement, and safety

features of the drums are specified. The number, location,

length, and cross-sectional area of the tamping feet are

described. The contractor is required to keep the spaces

between the tamping feet clear. The number of passes of

the roller on each layer of material is specified. Provisions

are made for situations where materials are too dry or too

wet. Where rolling with a specified roller is undesirable or

impractical, provisions are made for special compaction by

tampers or other equipment and for procedures that will

obtain the same degree of compactness as the rolling

process. Figures 3-20 and 3-21 show the operations of

placing, spreading, conditioning, and compacting earthfill.

The specifications provisions for control of placement water

content and compaction must be implemented by

establishing procedures to ensure their attainment. Prior to

construction of earthfill, all information available from field

and laboratory investigations is analyzed and reviewed in

light of design considerations to formulate tentative control

procedures. Special limiting moisture tests are performed

on representative samples of materials to be used in high

embankment dams for determining placement conditions that

will prevent development of excessive pore-water pressures

during construction and for settlement of the loaded soil

when saturated by water from the reservoir. Based on field

and laboratory investigations and on experience with similar

soils, the Denver Office will recommend placement

moisture limits and minimum density for representative

types of materials.

c. Control Techniques.&Although fill conditions are

approximated by laboratory tests, it is always necessary to
EARTH MANUAL

252

Figure 3-20.—Earthfill operation on impervious zone at Reclamation's McPhee Dam, Colorado. Selfpropelled tamping

compactor and disk plow in the foreground. Dart and Caterpillar belly dumps hauling and placing impervious fill

in the center of the photo. Contact between filter/drain chimney can be seen on right side (July 1983).

check planned control against actual results obtained on the

embankment and then to make any required adjustments.

This is done by careful observation and analysis of

operations, control test results, and embedded instruments,

especially during the early stages of earthfill construction.

In structures where unusual conditions are present, the

specifications may include provisions for the contractor to

construct one or more test sections of earthfill material. The

purpose of a test section is to determine the most effective

excavating, processing, placing, and compaction procedures

for representative soils under jobsite conditions. By varying

placement procedures within certain limits, by exercising

rigid control over the relatively small volume of the section,

and by maintaining complete, accurate records of tests, the

most applicable procedures for the rolled earthfill portion of

embankment may be determined during the initial stages of

construction. Results of field density tests made on test

sections will provide the necessary information for

establishing construction control procedures consistent with

design requirements. Figure 3-22 shows a test section under

construction using a pad foot roller to compact zone 1 at

New Waddell Dam, Arizona.

After proper placing procedures have been determined from

the embankment test section or from initial placing

operations when test sections are not required, construction

can proceed at full scale. Throughout construction, the

contractor' s operations must adhere strictly to limits and

conditions set forth in the specifications and to
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

253

Figure 3-21.—A view of McPhee Dam under construction. Upstream is to the left. Zoning can be clearly seen. 

From the left: gravel and cobble fill shell; impervious zone 1; zone 2 filter material; zone 2a drainage material; and

downstream gravel and cobble fill shell.

recommendations made by the design engineering staff. A

complete record of all operations must be kept so the most

efficient methods may be perfected. Relationships between

laboratory compaction curves and field roller curves

obtained by analysis of control test results are shown for

three dams on figure 3-23.

The most important variables affecting embankment

construction are:

 ̆ Selection of materials in the borrow area

 ̆ Distribution of materials on the embankment to

obtain uniformity

 ̆ Placement water content, and uniformity of this

moisture throughout the spread material

 ̆ Water content of borrow material

 ̆ Methods for correcting borrow material water content

if too wet or too dry

 ̆ Roller characteristics

 ̆ Number of roller passes

 ̆ Thickness of layers

 ̆ Maximum size and quantity of rock in the material

 ̆ Condition of the surface of layers after rolling

 ̆ Effectiveness of power tamping in places inaccessible

or undesirable for roller operation

To maintain control of earthfill construction, an adequate

number of inspection and laboratory personnel are essential.

For each shift, at least one inspector should be on the

embankment and one technician in the laboratory. Borrow
EARTH MANUAL

254

Figure 3-22.—Pad foot roller on a test fill of zone 1 material at New Waddell Dam, Arizona (1990).

operations on small jobs may be inspected by the

embankment inspector. On a large project, an inspector is

required at the borrow pit, especially when moisture control

is critical. On large projects, additional inspectors and

technicians may be required in all areas.

The borrow-pit inspector selects the areas in the borrow pit

to be excavated, determines the depths of cut, and specifies

the zone of the embankment where a particular material

should be placed according to an approved distribution plan.

The inspector checks adequacy of any mixing or separation

methods performed by the contractor and, as required, the

inspector cooperates with the contractor in determining the

amount of moisture to be added (or removed) to the borrow

pit to attain proper water content in the materials prior to

placement. Moisture content determinations of borrow-pit

materials should be made well in advance of excavation so

that corrective measures can be taken promptly.

The difference between laboratory optimum water content

and borrow-pit water content can be determined by

USBR 7240: Rapid Method of Construction Control.6

 As

a rule, to adjust to the final moisture content in the borrow

pit is impractical because of potential changes in water

content caused by (1) rain, (2) mixing or separation

operations, and (3) evaporation. However, an effort should

be made to have the excavated material as close as possible

to the desired water content before delivery to the

embankment. In some cases, specifications will require that

no more than 2- to 3-percent water can be added on the fill.

The foregoing inspection principles also are applicable to

structural excavations where materials are to be placed

directly in the embankment or are to be first processed or

stockpiled. Figure 3-24 shows the cut face of a borrow pit

where mixing of soils is accomplished during excavation;

figure 3-25 shows another method of excavating that

produces a good mixture from a layered deposit. Also,

figure 3-3, shows a cut face of a borrow pit in which

controlled excavation allowed material from the same pit to

be used for two separate embankment zones&pervious and

impervious.

The embankment inspector should determine the location

and elevation of tests made on the embankment and record

the location of the contractor' s operations. Horizontal

control, or station and offset, should be established.

Vertical control can be benchmarks and hand levels and

6 stadia rods used to establish elevations on the fill. When 7240: Performing Rapid Method of Construction Control.
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

255

Figure 3-23.—Average field and laboratory compaction curves.

materials are brought onto the embankment, the inspector

must verify placement in the proper zone, as indicated by

the approved distribution plan. Lines of demarcation can be

painted on rock abutments or marked by colored flags.

After materials are placed in the correct location, the

embankment inspector determines if the material contains

the proper amount of moisture before compaction. The

rapid method of construction control (USBR 7240) will

determine whether supplementary water is required. When

materials arrive on the embankment too dry, water can be

added by sprinkling before, during, or after spreading. The

contractor' s operations in sprinkling and mixing water with

soil will vary. However, regardless of the method used, the

proper water content must be uniformly distributed

throughout the layer before compacting.

Another important inspection task is to determine the

thickness of the compacted layer. A layer spread too thick

will not have the desired density for given conditions of

compaction. For initial placing operations, the test section

will have determined the proper spread thickness of a layer

which will compact to specified thickness; this specified

compacted thickness should never be exceeded. A method

for determining average thickness of placed layers is to plot

(daily) a cross section of the fill at a reference station(s).

The inspector' s report for that day will contain the number

of layers placed at that section; hence, average thickness can

be determined.

When oversize rock content is greater than about 1 percent,

removal of oversize rock from earthfill embankment

material is best accomplished prior to delivery of the soil on

the embankment. Smaller amounts of oversize rock can be

removed by handpicking or, under favorable conditions, by

various kinds of rock rakes. Generally, oversize rock,

which had been overlooked before rolling, can be detected

by the inspector during rolling by observing a bounce when

the roller passes over a hidden rock. The inspector should

be sure that the contractor removes the rock from the fill.
EARTH MANUAL

256

Figure 3-24.—A Holland loader excavating a vertical face mixing silt and fine sand deposits for 

impervious fill at Reclamation's Calamus Dam, Nebraska (Sept. 1983).

The inspector must ensure that each lift receives the

specified number of roller passes. An oversight in

maintaining the proper number of passes may lead to

undesirable low densities. Insistence upon orderliness of fill

procedures and the establishment of routine construction

operations will help to achieve the required number of roller

passes.

The final check on the degree of compaction is determined

by field density tests (USBR 7205, 7220)7

 and the rapid

method of construction control (USBR 7240).8

 The rapid

method should be checked periodically against values

obtained using the standard laboratory compaction of soils

test procedure (USBR 5500). 9

 If the degree of compaction

of material passing the 4.75-mm (No. 4) sieve is at or above

the minimum allowable percentage of laboratory maximum

dry density and the water content is within allowable limits,

the embankment is ready to be scarified and moistened, if

necessary, to secure a good bond between layers before the

next layer is spread. Time required to obtain results of the

field density test by the rapid method should be about 1 hour

or less.

7

 7205: Determining Unit Weight of Soils In-Place by the Sand-Cone

Method.

7220: Determining Unit Weight of Soils In-Place by the Sand

Replacement Method in a Test Pit. 8

 7240: Performing Rapid Method of Construction Control.

9

 5500: Performing Laboratory Compaction of Soils&5.5-lbm

Rammer and 18-in Drop.
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

257

Figure 3-25.—Two model 992C Caterpillar front end loaders loading zone 4 (gravel and cobble fill) from borrow

into a model 540 Dart belly dump truck. This type of loading operation, with steep face of borrow area, can be

used to get a well mixed fill from a layered deposit. Jordanelle Dam, Utah (August 1990).

Mechanical tamping&used around structures&along

abutments, and in areas not accessible to rolling equipment,

should be carefully observed and checked through use of

frequent density tests. The procedure to be followed for

mechanical tamping depends greatly on the type of tamper

used. Some factors affecting density are:

 ̆ Thickness of layer being tamped

 ̆ Time of tamping

 ̆ Water content of the material

 ̆ Mass of tamping unit

 ̆ Condition of tampers

 ̆ Air pressure (if air tampers are used the

manufacturer' s recommended pressures should be

maintained)

The embankment inspector must be alert for areas of low

density and have them remedied by sprinkling, scarifying,

removing, or rerolling, as required. An important function

of inspection is to determine when and where to make field

density tests. These tests should be made:
EARTH MANUAL

258

 ̆ In areas where the degree of compaction is doubtful

 ̆ In areas where embankment operations are

concentrated

 ̆ For every 1,500 m3

 (2,000 yd3) of embankment when

no doubtful or concentrated areas occur

 ̆ For representative tests of every 25,000 m3

(30,000 yd3) of earthfill placed

 ̆ For "record" tests at all embedded instrument

locations

 ̆ At least once during each work shift

Areas of doubtful density are sometimes detected by the

inspector' s observations. Insufficiently compacted locations

may include the following:

 ̆ The transition between areas of mechanical

tamping&or special compaction&and rolled earthfill

embankment along abutments or cutoff walls

 ̆ Areas where rollers turn during rolling operations

 ̆ Areas where too thick a layer is being compacted

 ̆ Areas where improper water content exists in a

material

 ̆ Areas where less than specified number of roller

passes were made

 ̆ Areas where dirt-clogged rollers are being used to

compact the material

 ̆ Areas where oversize rock has not been removed from

the fill

 ̆ Areas where materials with minor amounts of frost

have been placed, or were placed at nearly freezing

temperatures

 ̆ Areas that were compacted by rollers that have

possibly lost part of their ballast

 ̆ Areas containing material which differ substantially

from the average

The number and location of field density tests should be such

that the extent of the doubtful area is determined. All tests

made in areas of doubtful density should be identified by the

letter D.

When an embankment operation is concentrated in a small

area, i.e., if many layers of material are being placed one

over the other in a single day, tests should be made in this

area in every third or fourth layer to ensure the desired

density is attained. In such an area, all tests should be

identified by the letter C.

Even if areas of doubtful compaction do not exist or tests are

not required because of other reasons, at least one field

density test should still be made for each 1,500 m3

(2,000 yd3) of compacted embankment, and it should be

representative of the degree of compaction being obtained.

Such tests should be identified by the letter R.

Regardless of the number and purpose of other field density

tests, for large dams, one test is required for each 25,000 m3

(30,000 yd3) of earthfill placed; the tests should be

representative of the conditions of the fill. Percolation

settlement tests and specific gravity tests are made on the

same sample; the tests should be identified by the letter R

("record"). Additional material must be excavated adjacent

to the field density test hole to obtain enough soil to make

these additional tests.

"Record" tests are made at all instrument installations and are

recorded separately.

Test pits should be excavated periodically during construction

to visually check the fill for:

 ̆ Uniformity

 ̆ Laminations

 ̆ Contact areas

 ̆ Moisture content

 ̆ Density

 ̆ Interface zones

The effect of rolling and of superimposed loading is

evaluated by making field density tests as the test pit is

excavated. The degree of uniformity of moisture content

with depth is found by testing samples from various depths.

Visual inspection indicates whether successful bonding of

layers had been accomplished. As shown in figure 3-26,

undisturbed samples should be taken periodically for

laboratory testing to determine engineering properties and so

comparisons can be made to values used in the design. The

pit should be photographed. During a seasonal shutdown

period, test pits, as shown in figures 3-26 and 3-27 should be

excavated in the compacted embankment to determine the net

result of the season' s operations. Any unusual conditions

observed in the embankment test pit hole should be reported.

3-21. Compacted Pervious Fill.&

a. Design Considerations.&Permeable materials are

used in rolled embankment dams in internal filters and drains

and transition zones to control seepage and piping and in

outer shells to provide high strength to support the

impervious core. Usually, pervious fill is free-draining

cohesionless sand and gravel containing less than about

5 percent fines (material passing the 75-μm (No. 200) sieve).

Four criteria must be satisfied in controlling construction of

zones of sand and gravel:
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

259

Figure 3-26.—Block sample from test pit in zone 1 at McPhee Dam, Colorado. Final saw cut being made beneath the 

sample with a chain saw equipped with special tungster carbide bit. Also shows area where an in place density

test was taken 600 mm upstream of the block sample (1983).

 ̆ The material must be formed into a homogeneous

mass free from large voids.

 ̆ The soil mass must be relatively free draining

depending upon its intended use.

 ̆ The material must not consolidate excessively under

the mass of superimposed fill.

 ̆ The soil must have a high angle of internal friction.

If chimney drains containing filter and drainage layers are

not used (recently, chimney drains almost always are a

requirement), homogeneity of the shell is important to ensure

distribution of the inevitable seepage from the impervious

zone throughout the length of the dam since concentration of

seepage water into a few channels may induce dangerous

piping. The permeability of the permeable zone must be

much greater than the impermeable zone. In addition,

permeability of the free-draining zone should be high enough

to preclude development of construction pore-water pressures

in this zone. The requirements of low consolidation and high

shear strength for a permeable zone can be obtained by

properly compacting the materials. Because excessive porewater pressure is impossible to develop in pervious freedraining materials, the maximum practicable compaction of

such materials is desirable.

b. Specifications Provisions.&Specifications on

opencut excavations provide that suitable materials shall be

used for permanent construction. Provisions are made for

temporarily stockpiling such materials. When permeable
EARTH MANUAL

260

Figure 3-27.—Test pit at the interface of sand filter and gravel drain, Jordanelle Dam, Utah (September 1990).

soils are to be obtained from borrow pits, provisions for

compacted earthfill materials apply equally for these soils,

except that irrigation of borrow pits is not required.

Specifications prohibit use of frozen soil and do not allow

placing unfrozen material on frozen embankment. These

provisions are applicable to all kinds of soils. Provisions for

maximum allowable difference in elevation between adjacent

zones control placement of permeable material. Control of

openings through embankments, slopes of bonding surfaces,

and preparation of bonding surfaces apply equally to all

zones within the embankment. Distribution of material

within a permeable zone is controlled by the inspection staff.

Written directives are in the specifications pertaining to

permeable material used as a zone in the embankment. The

material will be described and its source designated.

Allowable thickness of the layer will be specified, either in

the form of compacted thickness or placed thickness.

Vibratory steel-drum rollers in the mass range of 4,500 to

9,000 kg (5 to 10 tons) are the best equipment for

compacting pervious clean coarse-grained soils. Drum-drive

self-propelled vibratory rollers may be effective on fine

uniform sands when other vibratory rollers are not. Rubbertire rollers may be used if they can produce the required

densities. At times, track-type equipment are used

effectively in rough areas or in confined areas where a

vibratory roller cannot operate effectively, for example, in

compacting a horizontal drainage layer on an irregular

foundation. The contact pressure of the equipment should be

at least 62 kPa (9 lbf/in2

) and should operate at a speed which

imparts greatest vibration to the fill. Track-type equipment

should be discouraged for compacting drainage blankets and

filter drains because of potential breakdown of the soil

particles.
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

261

Sometimes, alternate methods of compaction are permitted

by the specifications. In such cases, a minimum relative

density requirement is specified.

c. Control Techniques.&Workability of a permeable

soil is reduced considerably by the presence of even small

amounts of silt or clay. The contractor' s operations in the

borrow pits and on the fill must be such that contamination

of the pervious soil is minimized. As the material is brought

on the fill, it must be directed to the proper zone. Within

pervious shell zones, individual loads should be directed so

coarser material will be placed toward the outer slopes. This

does not apply to filter or drain material in chimney drains or

blankets. 

When compacted thicknesses are specified, the required

thickness of the loose layer, which will result in the specified

final thickness, must be determined by the inspector during

initial construction stage. Since in-place density will be

checked by relatively few tests after satisfactory placing

procedures have been established, the required thickness of

the loose layer must be maintained within close limits

throughout construction. The specified thickness of the

compacted layer is usually great enough to accommodate the

maximum size of rock encountered in the borrow. In cases

where cobbles or rock fragments occur that are greater in

size than the specified thickness of layer, provisions are

made for special embedding, for removal to outer slopes of

the pervious zone, or for removal to other zones. The

inspector must ensure that provisions for disposal of oversize

rock are followed.

After material has been placed, spread to the desired

thickness of lift, and oversize cobbles or rock fragments

removed, the next important step is application of water.

Thorough and uniform wetting of materials during or

immediately before compaction is essential for best results.

The best method for adding and distributing water on the fill

should be determined during initial placement. Relaxing

requirements for thorough wetting may result in densities far

below the minimum requirement&even with great

compactive effort. Different pervious materials require

different amounts of water for thorough wetting and best

compaction. In general, adding as much water to the

material as it will take is desirable. Too much water cannot

be added to an extremely pervious soil; however, permeable

soils containing small quantities of silt or clay may become

temporarily boggy if an excessive amount of water is used.

For these soils, care must be exercised in wetting the soil;

the contractor' s operations must be carefully controlled to

avoid creation of temporary boggy conditions.

Vibratory compaction units should be checked frequently to

ensure they are operating at a frequency which produces the

highest possible density. For cohesionless materials, the

frequency of vibration generally should fall between 1,100

and 1,500 vibrations per minute. If the track-type equipment

is used, operating at the highest practicable speed is desirable

during the compaction operation. High speed is conducive

to greater vibration and aids compaction. When inspecting

compaction made by track treads, ensure that the operator

makes complete tread coverage of the area to be compacted

before making the second and subsequent passes.

During initial placing operations, relative in-place density

tests (USBR 5525, 5530, and 7250)10 and gradation analyses

(USBR 5325 and 5330)11 are recommended at a frequency of

one test to represent each 750 m3

 (1,000 yd3) placed. After

placement procedures have proved satisfactory, and unless

significant changes in gradation occur or doubtful conditions

occur, one relative density test for every 7,500 m3

(10,000 yd3) of material placed will suffice. In the event of

significant gradation changes in borrow materials, increased

frequency of field tests may be needed to ensure satisfactory

compaction of the variable materials.

3-22. Semipervious Fill.&Semipervious materials

silty sands or gravels (SM or GM). Sands with dual symbol

classifications such as SW-SM, SW-SC, SP-SM, or SP-SC

[i.e., sands having as high as 12 percent passing the 75-μm

(No. 200) sieve (5 percent is the usual upper limit for a

material to be classified as pervious)] may have the

characteristics of semipervious material even though such

materials may be allowed by the specifications in

embankment zones designated "pervious fill." Generally,

compaction curves indicating adequately defined optimum

water contents and maximum dry densities can be developed

using standard compaction tests on impervious and

semipervious materials.

Also, in some dams, outer embankment zones composed of

coarse-grained sands and gravels, which contain appreciable

amounts of fines (i.e., > 5 percent), are sometimes

designated as "pervious zones." Compaction equipment,

procedures, and control for such materials can be either those

presented for pervious fill or those presented for impervious

10 5525: Determining the Minimum Index Unit Weight of

Cohesionless Soils.

5530: Determining the Maximum Index Unit Weight of Cohesionless

Soils.

7250: Determination of Percent Relative Density,

11 5325: Performing Gradation Analysis of Gravel Size Fraction of

Soils.

5330: Performing Gradation Analysis of Fines and Sand Size

Fraction of Soils, Including Hydrometer Analysis.
EARTH MANUAL

262

fill. The decision to use which control method depends on

whether the soil behaves like a pervious material or more like

an impervious material.

3-23. Rockfill.&Embankments with large rockfill

zones are becoming more common. This is primarily

because of:

 ̆ Necessity for using sites where rock foundation

conditions are unsuitable for concrete dams

 ̆ Suitability of modern construction equipment to handle

rock

 ̆ Increasingly higher dams being constructed

 ̆ Economic benefit that is obtained by maximum use of

rock from required excavation.

Rock that does not easily break during handling,

transportation, and compaction is considered sound and

results in a pervious fill. Such sound rock is desirable for

rockfill dams, or rockfill zones, especially if the source is

from required excavations such as a spillway.

a. Sound Rock in Rockfill Dams.&

1. Specifications.&The specifications for pervious

rockfill sections generally require that rock be sound, well

graded, and free draining without specifying gradations; but,

the maximum permissible size is specified together with lift

thickness. Normally, rock fill is placed by dumping from

trucks; bulldozers spread the material to the desired lift

thickness. The required placement and spreading operations

should avoid segregation of rock sizes. Type of roller, lift

thickness, and number of passes are specified, preferably

based on results of test fills.

2. Placement Operations.&When rock is dumped

on the fill surface and pushed into place by a bulldozer, the

fines are moved into the upper part of the lift, thereby

creating a smoother working surface for the compacting

equipment. If a layer of fines of significant thickness is

produced that might seal off the upper part of the lift and

prevent distribution of fines throughout the lift, the rock may

be dumped directly in place.

All oversize rock must be removed before compaction.

Usually, this is done with bulldozers fitted with special "rock

rakes." Oversize rocks are often pushed into a specified

zone in the outer slopes. Sometimes, excessively large rocks

are hauled off to be dumped elsewhere or they are broken

with a drop weight or explosives and used in the rockfill or

riprap zone. Another common way of breaking oversize

rock is with hydraulic chisels or spliters. Oversize rocks

should never be allowed to accumulate along the contact

slope of a closure section.

Close inspection is required to ensure that the material does

not contain excessive fines. Excessive fines can cause

excessive postconstruction settlements when the reservoir is

filled. Specifying a limited amount of fines in the

specifications is difficult; consequently, this is rarely done.

However, the design office should provide guidance to field

personnel based on results from rock-test fill studies which

will aid in determining if excessive fines are present. The

design and construction staff must be alert for material

variations that could result in undesirable changes in

gradation of the material brought to the embankment. If this

occurs, the contractor should be informed so a change can be

made in quarrying techniques.

3. Compaction.&Current practice is to use smooth

steel-wheel vibratory rollers to compact all sound rockfill in

comparatively thin lifts with minimal application of water.

The lift thickness specified is dependent on size and type of

rock and on type of compaction equipment used; usually,

thickness is determined from results obtained during

construction of a test fill. Less desirable rocks may break

down in varying degrees upon excavation, handling, and

compaction. These unsound rocks may degrade because of:

 ̆ Lack of induration

 ̆ Structure (such as thin bedding)

 ̆ Degree of fracturing

 ̆ Weathering

 ̆ Other physical and chemical properties

Some examples of material to be avoided are:

 ̆ Shales

 ̆ Mudstones

 ̆ Siltstones

 ̆ Claystones

 ̆ Chalk

 ̆ Earthy limestones

 ̆ Other sedimentary rocks which may be poorly

cemented

Ordinarily, sound rocks that are quite weathered and very

fractured may not be acceptable for rockfill zones because of

their susceptibility to breakdown caused by weathering and

fracturing.

Because of general unpredictability of breakdown of most

types of rocks, use of test quarries, test fills, and laboratory

tests for designing and constructing rockfill dams or zones is
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

263

widespread. Generally, the lift thickness specified will be no

thicker than 60 cm (24 in) unless test fills show that adequate

compaction can be obtained using thicker lifts. The

maximum particle size allowed in the lifts should not exceed

90 percent of the lift thickness.

Scarification of compacted lift surfaces is not necessary and

should not be allowed because it disturbs the compacted

mass.

b. Unsound Rock in Rockfill.&Formerly, use of soft

or unsound rocks has been dictated by availability of large

quantities from required excavations. The main concern

about these materials is the tendency to weather and soften

with time when exposed to air and water within the

embankment. However, dams with large portions of

embankments composed of unsound rocks attained adequate

shear strength, and the rock experienced insignificant

breakdown after placement when the rock was placed in

random and semipervious zones. Where unsound rocks will

constitute a significant structural portion of a fill, their

properties and the best methods for compaction should be

determined by means of a test embankment constructed

during design studies.

Some rockfills composed of unsound rocks have been

compacted by first rolling the loose lift with a heavy tamping

roller equipped with long spike or chisel-type teeth ("shale

breaker") and then compacting the lift with conventional

tamping or rubber-tire rollers.

3-24. Riprap.&Riprap is the commonly specified

material for slope protection. Properly graded riprap, placed

to provide a well-integrated mass with minimum void spaces

so that underlying bedding cannot be washed out, provides

excellent slope protection. The primary factors that govern

successful construction are:

 ̆ Loading from the quarry to provide a good mixture of

different sizes within the required gradation in each

load. Proper production from the quarry requires that

blasting operations or processing produce proper rock

sizes and that loading operations are properly

inspected. Gradation testing is often specified.

Grading of riprap and other large stone can be

performed in accordance with ASTM procedure D5519-94 [a] (see sec. 3-8b). Gradation tests are best

performed at the placement site by sampling several

trucks. Hauling vehicles should be weighed for

determination of tonnage hauled. 

 ̆ The rock should be placed on the slope to provide

uniform distribution of different sizes without

segregation to provide a rock mass without large

voids. Placement should be accomplished by placing

loads along the slope against previously placed riprap;

this reduces size segregation which otherwise occurs

if loads were dumped in separate piles. Dumping

rock at the top of the slope into a chute should never

be allowed because this results in segregation. If

dumping is done from trucks it is usually necessary to

winch load haulers down the slope to the placement

location. Dumping should proceed along horizontal

rows and progress up the slope; loads should not be

dumped to form rows up the slope. If large rock is

specified, a crane with an orange-peel or clam shell

attachment operating from a platform built on the

slope can be used. Recently, large backhoes have

been used to place riprap; experienced equipment

operators can do a good placement job. In using

backhoes, riprap must be placed as the embankment is

constructed because riprap placement must stay within

about 5 m (15 ft) of the top of the fill. The process of

end dumping without manipulation is generally not

sufficient for good placement. Reworking with

backhoes or other acceptable equipment will be

required. Close visual inspection or actual

measurement is required after dumping and spreading

riprap to determine the adequacy of the distribution of

different sizes. Reworking may be minimized by

exercising care when loading to ensure that each truck

load has the proper amount of each size rock (i.e., the

proper gradation). Placement should result in a low

void ratio, on the order of 0.35 or smaller. The void

ratio over a placement area can be estimated by using

mass tickets from each truck and the area of

placement. If the volume of an area is considered a

solid volume, then the void ratio is determined by

proportion of the solid volume and the actual mass.

For example, assume an area of 100 by 100 by 3 feet.

Assume the density of riprap as 160 lb/ft3 (or use the

specific gravity of the rock). The solid volume is then

160x100x100x3 = 4,800,000 lb = 2,400 tons. If the

mass tickets equal 1608 tons, the void ratio is (2,400-

1,680)/2,400 = 0.33. This method of void ratio

ensures a tight structure but does not ensure good

distribution of grain sizes. Strict enforcement of

specifications is required, especially during early

stages of riprap placement to ensure a well-graded

mass without large voids.

 ̆ A bedding layer (or layers) designed as a filter must

be provided between the riprap and embankment

material to protect the embankment material from

erosion by wave action and to provide a stable base

for riprap. Many riprap failures have occurred

because bedding material was not large enough to

preclude washing out through riprap interstices by
EARTH MANUAL

264

wave action. Removal of any bedding causes

settlement and dislodgement of overlying riprap,

which further exposes bedding and embankment

material to direct wave action. Good practice is to

place rock spalls or crushed stone of like size between

the bedding and the riprap if they are available from

quarry or required excavation. The term "spalls"

refers to the finer materials resulting from rock

excavation for materials such as riprap. Spalls must

be durable fragments of rock, free of clay, silt, sand,

or other debris. Spall gradation varies and must be

specified for each particular job. End dumps with

spreader boxes provide the best means of placing

bedding and spalls.

3-25. Miscellaneous Fills.&Dam embankments on

very plastic foundations may require toe berms to improve

stability. Excavations for dam foundations or for appurtenant

structures often produce material unsuitable for, or in excess

of, requirements for the structural zones of a dam. Such

excavated material can be used in toe berms of the dam. In

localities where good quality riprap is expensive, fill

materials from structural excavations have been used to

flatten the upstream slope of the dam to permit use of lesser

quality riprap and, in some cases, no riprap at all. In a few

cases, excess low quality material from required excavation

has been used in a noncritical zone&in the downstream

portion of a dam&merely to replace material which otherwise

would have had to be borrowed at greater expense.

Permeability of miscellaneous fills is not important in the

design; they may not specifically require compaction.

However, full use should be made of compaction obtainable

by routing hauling and placing equipment on placed layers of

the material. Sometimes, the nature of available materials or

the design may require that some compactive effort other

than routing of equipment be used. For example, sheepsfoot

rolling has been used to break up fairly large pieces of soft

rock to avoid excessive settlement. Compaction should be

specified if the miscellaneous fill is to function as an

impervious blanket or is within the limits of the embankment.

For miscellaneous fills, specifications should describe the

materials to be used and state their sources. Thickness of

layers will be specified, and the requirement for routing

construction equipment over each layer will be stated. The

specifications will also state if any moisture or special

compaction requirements are needed.

Inspection of miscellaneous fills is entirely visual.

Ordinarily, control tests are not made on such fills. A few

fill density tests may be required for record purposes, and

instruments may be placed to obtain performance

characteristics. When inspecting miscellaneous fills, it is

important to ensure that specified lift thickness is not

exceeded; also make sure that hauling equipment never

concentrates on a roadway but is routed over the entire

breadth of the placed layer.

3-26. Instrument Installations.&The behavior of

many embankment dams is monitored during construction

and throughout operation by instrumentation placed in the

embankment, in the foundation, and in or on appurtenant

structures.

a. Instruments.&Data obtained from the instruments

are used to assess performance of the structures by

comparing the results to design assumptions and to normal

performance expectations of embankment dams and their

foundations. Besides visual inspections, performance

monitoring with instrumentation is used to ensure safe, longterm performance of dams. 

The various types of instrumentation installations can be

grouped into five categories:

 ̆ Devices to observe pore-water pressures in the

embankment and in the foundation

 ̆ Devices to observe earth pressures in the embankment

 ̆ Internal and external devices that provide data on

deformations and displacements of the embankment

and foundation

 ̆ Devices for monitoring seepage flows

 ̆ Vibration recording devices to indicate the result of

transient stresses on the embankment

Type and quantity of instruments installed at a dam will vary

with:

 ̆ Design

 ̆ Purpose

 ̆ Foundation conditions

 ̆ Embankment materials

 ̆ Embankment size

Detailed information concerning types of embankment dam

instruments can be found in the Embankment Dam

Instrumentation Manual [1]. 

b. Installation of Embankment Dam Instrumentation.&Work required for installing the instruments is usually

performed by the contractor under provisions of the

specifications for construction or modification of a dam. In

special cases, however, Government forces may perform all

or part of the work. The Embankment Dam Instrumentation
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

265

Manual provides detailed information concerning methods

for installing embankment dam monitoring equipment.

c. Inspection.&Inspectors are required to inspect and

test all the equipment, to oversee all installation work, and to

obtain instrument readings during construction. Close

inspection is essential to ensure correct installation of

equipment and proper operation of the instrumentation.

d. Record Tests.&Record tests of embankment and

foundation materials at internal instrument installations are

necessary to obtain data on soils adjacent to the instruments.

One field density test should be made at each unit or element

of displacement or deformation monitoring device in earthfill

material. Two test samples should be obtained from soil near

the element or unit as well, one in the rolled embankment

near the element and one in specially compacted material

placed around the unit. When all or part of a dam is founded

on highly compressible materials, representative undisturbed

samples should be obtained in the foundation at the locations

of the vertical movement and baseplate installations unless

suitable samples have been obtained previously. Tests are

not required when these devices are placed on a rock

foundation unless specifically requested. Tests at the

elements or units should be designated "record rolled,"

"record tamped," or "undisturbed," depending on the

material being tested.

One field density test is required near each embankment

earth pressure cell and piezometer tip. This test should be

made in the rolled fill at the piezometer tip location prior to

excavating the offset trench for the tip for closed-system

piezometers. Each hole drilled for foundation piezometers

should be logged throughout its length, and a record sample

of the material should be obtained at the depths where

piezometers will be located.

In addition to field density tests on embankment materials

and in-place density tests on foundation materials, the

following four tests should be performed on the samples

taken:

1. Gradation analysis

2. Specific gravity

3. Liquid and plastic limits

4. Percolation-settlement

This laboratory testing may be performed during seasonal

shutdowns when workload permits. Sufficient material must

be obtained while making the density tests so that additional

tests can be made. Before testing, foundation samples should

be sealed to prevent moisture loss. Special care should be

exercised to attain desired accuracy in all record tests.

Embankment field moisture and density conditions must be

duplicated for the percolation-settlement test and in-place

conditions must be maintained for foundation materials.

During and after construction, the dam designer may request

that some record test samples or other special samples (core,

blocks) be sent to special laboratories for testing and that the

remaining samples that are not moisture sensitive be

permanently stored at the damsite, in accordance with

Reclamation guidelines. All stored samples should be

properly marked and referenced to the pertinent density test.

Each container should be identified as follows:

 ̆ Name of dam.

 ̆ Identification symbols.

 ̆ For samples taken at piezometer tips, the letter P and

the number of the tip (as shown on installation

drawings) should be used (e.g., "Heron Dam, P-14")

identifies the sample.

 ̆ For samples taken at porous-tube piezometers, the

symbol PTP is used.

 ̆ For samples taken at crossarm units of a vertical

movement installation, e.g., "Heron Dam, X-A-8-R"

and "Heron Dam, X-A-8-T" represents, respectively,

record rolled and record tamped material adjacent to

the eighth crossarm unit installed in installation A for

the dam.

 ̆ Likewise, as above, the symbols "Trinity Dam,

H-B-6-1-R" and "Trinity Dam, H-B-6-1-T" represent

samples taken from excavation and backfill of the

trench for plates associated with a horizontal

movement device.

 ̆ The symbol BP can be used for samples from

foundation settlement (baseplate) installations.

These identifying symbols should be marked on the container

in addition to identification normally required on record

samples.

Record samples obtained from the location of foundation

piezometers should contain representative materials taken

from the location of the tip of the piezometer. Quantity of

sample will depend on drilling equipment used to excavate

the holes.

3-27. Records and Reports.&The inspector must

make daily, periodic, and final reports covering construction

activities work.

a. Daily Reports.&The daily reports should record the

progress of construction, provide pertinent information for

the inspector (who is beginning a shift) about shutdowns,

construction difficulties, and tests in progress. These reports
EARTH MANUAL

266

will also furnish data for use in compiling the construction

progress report. The form of a daily report will vary to suit

the requirements of each job, but all information in the

periodic earthwork progress report should be based on dayto-day records. A consistent, systematic method is desirable

for identifying field density tests made on the embankment.

Each test should be designated by the date, shift, number on

that shift, and purpose; e.g., "8-2-92-a-2-D" defines:

 ̆ The field density test made August 2, 1992

 ̆ The 1st workshift, the 2nd test made on that shift

 ̆ The purpose was to check an area of doubtful

compaction

The above legend is as follows:

a = First shift

b = Second shift

c = Third shift

D = Doubtful area

C = Concentrated area

R = Representative

Results of tests made daily on the embankment are reported

in the progress report of embankment construction on the

appropriate forms.

b. Periodic Progress Reports.& Adequate technical

control of construction is an important and essential function

of field forces on an embankment dam project. Complete

records of all data pertaining to methods and procedures of

achieving satisfactory control must be maintained as a normal

part of the inspection. Summary of Earthwork Construction

Data reports are required of each project, for each month

during the working season that embankment is being placed,

except in special cases additional summaries or reports may

be required. This report is a part of the Construction

Progress Report (L-29). Copies of the Summary of

Earthwork Construction Data report may be required for

review by design team members. A Summary of Earthwork

Construction Data report consists of:

1. Narrative and Photograph.&The narrative shall

consist of a description of earthwork operations during

the reporting period. Important features of normal

embankment operations to be included in the narrative of

initial reports are outlined below:

Borrow-pit operations (each borrow area):

Description of material

Equipment used

Natural water content

Method of adding moisture

Depth of cut

Stratification

Mixing, separating

Transporting

Embankment operations (each zone):

Equipment used

Spreading, mixing

Method of adding moisture

Maximum size of rock fragments

Method of removing oversize rock fragments

Compaction method

Thickness of layers

To avoid repetition, many items reported in the above outline

should be described only once. Thereafter, only significant

changes in materials or in methods and procedures should be

described. Any difficulty or unusual conditions encountered

should be fully described. The narrative should clarify any

results reported on the various forms that require special

mention, and it should report pertinent information not

covered by the forms.

Photographs should be taken far enough in advance to ensure

no delay in submitting the reports and should include:

(a) A view from an abutment point showing the extent

of operations on the dam during the period of the

report. The camera position should be located

sufficiently high so that location can be used until the

dam is complete.

(b) An overall view showing the extent of operations

in each major source of material.

(c) Closeup views of each operation such as dumping,

spreading, adding moisture, disking, rolling, or

mechanical tamping. Photographs of these operations

need be submitted only once. Thereafter, only

photographs showing different or unusual procedures

should be submitted.

(d) Closeup views of typical borrow-pit cut banks.

These should be submitted once.

2. Completion of form 7-1352.&This form should

include results of field and laboratory tests made during

the reporting period for all materials controlled by

USBR 7240: Performing Rapid Method of Construction

Control, 12 or by laboratory compaction tests (USBR

12 7240: Performing Rapid Method of Construction Control.
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

267

5500 or 5515). 13 The specific gravity of the minus

4.75-mm (-No. 4) material and the percolationsettlement tests need be performed and reported only for

every 30,000 m3

 (30,000 yd3) of material placed. The

latter is a minimum requirement; variations in material

may require more frequent tests.

3. Completion of form 7-1582.&This form should

include results of field and laboratory tests made during

the reporting period on all materials controlled by

percent relative density.

4. Computer software programs are available which

summarize results of in-place density, rapid construction

control, and relative density tests, and that generate

forms similar to 7-1352 and 7-1582. Reclamation field

laboratories currently use the computer program

PCEARTH for statistical compilation of earth

construction data. This program provides for statistical

compilation and reporting of compaction control data by

rapid compaction and relative density test methods. The

program also allows for compilation of physical property

data from borrow investigation, foundation acceptance,

and aggregate processing activities. Modules are also

available for soil cement and soil cement slurry

(flowable fill used in pipe embedment) test data. This

program can be obtained for a small fee from the Earth

Sciences laboratory at the Technical Service Center.

5. Roller Data.&Figure 3-28 shows a suggested

tabulation of data for tamping rollers. Manufacturer' s

specification data sheets are also acceptable. Such data

should be obtained for each roller used on the

embankment to ensure compliance with specifications.

This information should be reported only once for each

roller, except when modifications are made to the roller.

c. Final Embankment Construction Reports.&Upon

completion of embankment construction, a report should be

prepared summarizing work accomplished. Final

Construction Reports are required to be prepared in duplicate

and submitted to the Denver Office for all major works,

including dams. A detailed summary of embankment

construction need not be transmitted separately but should be

included in the Final Construction Report. A suggested

outline for the embankment portion and related construction

requirements of the report follow. Items in the outline not

applicable to a particular project should be disregarded, and

variations or additions should be made to suit individual job

conditions.

1. General.&

(a) Location and purpose of structure.

(b) Description of dam and appurtenant works,

including dimensions and quantities involved.

2. Investigations.&

(a) Foundation explorations. -

(1) Description of foundation conditions.

(2) Itemized summary of foundation explorations

showing number, depth, and coordinate location of:

drill holes, test pits, shafts, and tunnels.

(3) Description of any special tests and methods of

taking undisturbed samples.

(b) Construction materials. -

(1) If a preconstruction earth materials report were

prepared, a general description of materials

investigation should be prepared and reference

should be made to the previously prepared report.

However, a complete and detailed description of

additional investigations made subsequent to the

preconstruction earth material report is required.

(2) If the preconstruction earth materials report was

not prepared, a complete and detailed description of

material investigations of borrow areas and rock

sources with test results and quantities available

shall be included in the Final Construction Report.

3. Construction history (include photos within text.&

(a) Required excavations, except borrow areas. -

(1) Stripping of foundation(s).

(2) Cutoff trench(s).

(3) Grout cap trench.

(4) Miscellaneous excavations.

The construction history shall include discussion on

depth, quantities, dewatering methods, disposition of

materials excavated, and type of equipment&including

number used and rated capacity.

(b) Foundation drilling and grouting. -

(1) General.&Include discussion on type of

equipment used and capacity. For the grouting

plan, show location and depth of holes.

(2) Pressure grouting.&Include discussion of:

grouting procedures, type of equipment and 

13 5500: Performing Laboratory Compaction of Soils&5.5-lbm

Rammer and 18-in Drop.

5515: Performing Laboratory Compaction of Soils Containing

Gravel.
EARTH MANUAL

268

Figure 3-28.—Form for recording embankment roller data.

pressures used, grout take and results obtained, and

any special problems and methods used to obtain

satisfactory results.

(c) Borrow area operations. -

(1) General.&Discussion of plan and use of

specified material sources and any problems in

borrow areas not anticipated at the time

specifications were issued.

(2) Borrow areas.&Detailed report of: initial

conditions of borrow pits, methods of excavating,

mixing, screening, and transporting of material.

Include: type, size, and rated capacity of all

equipment used&with special emphasis on any

unusual requirements for blending or excavating

procedures. Also, note: borrow pit yield, methods

of controlling moisture, disposition of oversize

material, and material from stripping operations.

(d) Embankment operations. -

(1) Zones.&Discussion to include: construction

methods and sequence, material source, and any

variation from the approved materials distribution

plan and reasons therefore. For riprap and rockfill,

record gradation.

(2) Placing.&Description of methods used

including: scarifying, spreading and leveling,

rolling, power tamping, removal or reworking, and

any other part of the work considered peculiar to

the placing operation.

(3) Equipment.&Discussion of type, capacity, size,

number used, efficiency, and suggested

improvements (if any) for all equipment used in

placing embankment.

(4) Testing.&Performance of field laboratory,

including number of testing personnel and number

and type of tests performed should be summarized.

Discussion of control tests, such as moisture content

and density, and any special tests should include:

procedures in making tests and reporting methods,

extent of testing, adequacy of tests, and difficulties

encountered.

4. Embankment Dam Instrumentation.&Brief description of systems installed such as piezometer tips,

horizontal and vertical movement crossarms, and

embankment and structure settlement measurement

points.

(d) Embankment Dam Instrumentation Reports.&A

monthly report, separate from other construction

reports, is required during construction of the dam to
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

269

present progress of placement of embankment dam

instrumentation. This report should include:

 ̆ A short narrative on progress of work

 ̆ As-built information

a. Reports of problems or abnormalities during

installation work

b. Readings made during the preceding period

c. Representative photographs showing current details

of the work

Within 6 months after completion of instrument installations,

a Report on Embankment Dam Instrumentation is required

and should include the following:

 ̆ Document materials and equipment actually used in

instrumentation installations.

 ̆ Records of preinstallation testing of equipment.

 ̆ Drill logs for holes in which instruments were

installed.

 ̆ Record test information.

 ̆ Problems or abnormalities that occurred during

instrument installations.

 ̆ Deviations or modifications from specification

requirements relative to instrument installations.

 ̆ Contractor claims that arose relative to

instrumentation work.

 ̆ Photographs as available.

 ̆ Complete as-built information.

 ̆ Comments, criticisms, and suggestions so that future

instrumentation design work can be improved.

 ̆ All instrumentation readings taken during construction.

Following completion of the dam, instrument readings shall

be taken in accordance with the current Schedule for Periodic

Readings (L-23) or with the reservoir filling criteria.

3-28. Control Criteria.&The concept of limiting the

moisture condition for placement of compacted earthfill in

dam embankments has been used by Reclamation for many

years. The idea of limiting the magnitude of pore-pressure

buildup in cohesive soils during construction, by controlling

the placement moisture, has been a major consideration since

1946. The relationships among moisture control, pore-water

pressure potential, and stability of the structure are well

established and are generally recognized as a basis for an

upper placement moisture limit.

Localized shear planes may develop under certain conditions

of placement moisture and compactive effort. Using

Reclamation procedures for compaction of earthfill, these

shear planes occur when the soil is at optimum water content

or wetter when construction pore pressures normally increase

rapidly with increased moisture content. A typical example

of laboratory tests on one soil is shown on figure 3-29. The

net effect of development of localized shear planes would be

a significant loss of shear strength; hence, placement

moisture should be so controlled as to avoid any possibility

in developing local shear planes.

The phenomenon of loss of effective strength of dry, lowdensity soil as the water content is increased is also well

known. This reduction in strength may result in appreciable

volume change of a loaded soil, either in the foundation or in

the compacted embankment. In the case of embankment

dams, wetting the foundation or the embankment&following

construction&does not occur uniformly. Hence, such volume

changes usually will result in differential settlement and may

result in cracking of the embankment. Many failures of

small embankment dams are attributed to cracking due to

differential settlement. Placement moisture should be

maintained in a range between the specified upper and lower

moisture limits so that the soil will not exhibit additional

consolidation upon saturation, will not develop excessive

pore pressures, and will not develop shear planes under field

compactive effort. Generally, this range is from about

2 percentage points dry to 1 percentage point wet of optimum

moisture content.

High shear strength, low consolidation, and permeability are

all related to dry density obtained in a fill. Design is usually

based on impervious or core material being placed at or

slightly below average laboratory maximum dry density of

the minus 4.75 mm (-No. 4) fraction. An average D-value

(ratio of dry density of fill to laboratory maximum dry

density, expressed as a percentage) near 100 percent is

expected for most soils containing less than about 30 percent

plus 4.75 mm material. For gravelly materials containing

more than about 30 percent plus 4.75 mm material, an

adjusted field density of the control fraction less than

laboratory maximum dry density of the minus 4.75 mm

fraction may be expected during construction and is

considered in design.

Overall quality of the embankment being placed can be

evaluated by statistical analysis of test results. A simple

frequency distribution analysis of the variables wo-wf

 and Dvalue, as outlined on table 3-2, can be maintained throughout

construction to aid engineers and inspectors in their efforts to

control placement within recommended or specified limits.

Figures 3-30 and 3-31 show worksheets designed for such an

analysis. Forms of this type, on which data from each test

are entered as results become available, should be maintained

in the laboratory or in some other suitable place where they
EARTH MANUAL

270

Figure 3-29.—Typical laboratory tests for the development of shear planes.

will be readily available for inspection. By means of this

analysis, the frequency distribution of test results is obtained,

and statistical values such as the mean, the standard

deviation, and the percentage of tests falling outside specified

limits can be determined. Computer software programs are

available which calculate statistical information on test data

such as average D-value, average wo-wf

 , percent of accepted

tests, and several other parameters. Reclamation’s computer

program PCEARTH can readily perform such statistical

compilations and generate distribution graphs as shown on

figures 3-30 and 3-31.

Various other criteria for quality control have been proposed.

Table 3-2 lists suggested limits of density and moisture

control based on Reclamation' s experience with earthfill

dams. In the absence of instructions to the contrary, criteria

given in this table may be used.
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

271

Figure 3-30.—Statistical analysis of test results for density control of fill.
EARTH MANUAL

272

Figure 3-31.—Statistical analysis of test results for moisture control of fill.
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

273

Table 3-2.—Criteria for control of compacted dam embankments

Percentages based on minus 4.75 mm (-No.4) fraction

15 m (50 ft) or less in height 15 m (50 ft) or greater in height

Type of material

Percentage of plus 4.75 mm

(+No.4) fraction by dry mass

of total material

Minimum

acceptable

density

Desired

average

density

Moisture

limits,

wo-wf

Minimum

acceptable

density

Desired

average

density

Moisture

limits,

wo-wf

Cohesive soil:

Soils controlled

by the laboratory

compaction test

 0 to 25 percent

 26 to 50 percent

 More than 50 percent1

D = 95 D = 98 -2 to +2 D = 98 D = 100 2 to 0

D = 92.5 D = 95 -2 to +2 D = 95 D = 98 Note2

D = 90 D = 93 -2 to +2 D = 93 D = 95

Cohesionless soil:

Soils controlled

by the relative

density test

Fine sands with 0 to 25%

Medium sands with 0 to 25% 

Coarse sands and gravels

with 0 to 100%

Dd = 75 Dd = 90 Soils should

be very wet

Dd = 75 Dd = 90 Soils

should

be very

wet

Dd = 70 Dd = 85 Dd = 70 Dd = 85

Dd = 65 Dd = 80 Dd = 65 Dd = 80

The difference between optimum water content and fill water content of dry mass of soil is wo-wf , in percent. 

D is fill dry density divided by laboratory maximum dry density, in percent.

Dd is relative density as defined in chapter I.

___________________

 1 Cohesive soils containing more than 50 percent gravel sizes should be tested for permeability of the total material if

used as a water barrier.

 2

 For high embankment dams, special instructions on placement moisture limits will ordinarily be prepared.

E. Canals

3-29. Design Features.&Canals are constructed

channels of widely varying capacities used to convey water

for irrigation, power, domestic uses, or drainage.

Distributory channels conveying water from the main canal

to farm units are called laterals and sublaterals. The design

capacity of an irrigation canal or lateral is based on

maximum daily consumptive use rate downstream of the

section under consideration, including allowance for seepage

losses. Water loss from seepage is a major problem in canal

design. On a typical irrigation project, about 20 to 40

percent of water diverted into the canals and laterals can be

expected to be lost by seepage unless lining is provided.

Conversely, water seeping into a canal can (under favorable

conditions) be used to augment the water supply. Also,

inflow seepage is the means by which subsurface drainage is

accomplished for open-ditch drainage systems.

Canal construction involves a variety of earthwork problems.

Because of the great longitudinal extent of the work, many

different kinds of earth foundation and material conditions

are encountered, all of which must be treated differently.

Thus, some reaches of a canal may require only uncompacted

embankments made of unselected materials excavated from

the prism, while other sections may require careful control

of cuts in borrow areas, strict moisture control, and

compaction of earth in the form of linings or entire

embankments. The following paragraphs summarize major

design features related to earthwork in canal construction.

Canals are classified as unlined or lined, depending on the

extent to which special provisions are made to prevent

seepage. An unlined canal or lateral is an open channel

excavated and shaped to the required cross section in natural

earth without special treatment of the subgrade.

Construction of compacted embankments at locations where

the canal water surface is above natural ground is considered

a normal seepage control measure in unlined canal

construction.

The cross section of a canal is selected to satisfy the most

desirable criteria for bottom width, water depth, side slopes,

freeboard, and bank dimensions, and to facilitate operation

and maintenance. The ratio of bottom width to depth ranges

from 2:1 for the smallest laterals to 8:1 for large canals; side
EARTH MANUAL

274

slopes on unlined canals range from 1.5h:1v to 2h:1v, or

flatter where unstable soils are encountered. Design of

canals is based on development of a steady-state seepage

condition from the normal high water surface, followed by

rapid drawdown of the water surface. Dimensions of the

banks and the soils of which they are composed must ensure

stability under these extreme hydraulic conditions.

The water section of a canal may be entirely in cut, entirely

in fill, or partially in each, depending on economics of the

route, necessary gradient, structure design, and requirements

of safety and water distribution. If the water section is

partially or entirely in fill, compacted embankments may be

used to prevent excessive amounts of seepage.

Requirements for compacting an embankment under

compacted earth lining depend upon (1) height of fill, (2)

earth construction materials used, and (3) method of fill

construction. These requirements are reflected in the

specifications.

Operation and maintenance roads are usually provided on the

lower bank of large canals. In some cases a maintenance

berm may be needed on the upper bank. In deep cuts, berms

are often used to reduce bank loads, to prevent sloughing of

earth into the canal, and to lower the elevation of the

operating road for easier maintenance. Berms also provided

between deep cuts and adjacent waste banks. Even where

operating roads are not planned, canal and lateral banks are

smoothed by blading to allow power mowers and other

power equipment to control vegetation.

A lined canal or lateral is one in which the wetted perimeter

of the section is lined or specially treated. Materials used to

line canals include:

 ̆ Unreinforced or reinforced concrete

 ̆ Pneumatically placed mortar

 ̆ Buried geomembranes

 ̆ Compacted earth

 ̆ Earth treated with additives (stabilized soils)

Various types of asphalt, brick, stone, and other materials

have been used in the past.

The great need to reduce water losses in canals means a

continuing search for effective low-cost linings. In addition

to water savings achieved by lining canals, other advantages

include:

 ̆ Prevention of water logging adjacent land

 ̆ Lower operation and maintenance costs

 ̆ Less danger of canal failures

 ̆ Reduced storage with less diversion requirements

In the case of hard-surface linings, further advantages

include:

 ̆ Possible smaller canal sections and structures

 ̆ Less right-of-way

 ̆ Higher permissible velocities

 ̆ Steeper gradients

Side slopes on earth-lined canals are 2h:1v or flatter, and on

hard-surface linings usually 1.5h:1v.

Lined canals can be built in either cut or fill or partially in

each; the economic advantages of balanced cut and fill must

be weighed against special treatment of fills to support the

lining properly in a canal. The lining above the water

surface varies with height and depend upon:

 ̆ Flow capacity

 ̆ Water velocity

 ̆ Alignment curvature

 ̆ Inflow of storm water

In addition, height increases with water surface elevation

caused by:

 ̆ Canal checks

 ̆ Checks in pumping plant forebays

 ̆ Surge waves

 ̆ Wind action

Various types of earth linings have been used by Reclamation

to reduce water loss [16]. The simplest method is silting

(sediment sealing), in which fine-grained soils are dispersed

into the water by hydraulic or mechanical means and are

deposited over the wetted perimeter of the canal. Although

it is effective in reducing seepage, silting is not considered a

permanent seal because the silt layer is easily destroyed.

Sometimes, thin, loose earth blankets of fine-grained soils

have been used as linings. Such linings are inexpensive and

are temporarily quite effective, but they erode easily unless

protected by a cover layer of gravel. Bentonite applied as a

buried membrane, or mixed with permeable-type soils, and

buried geosynthetic or asphalt membranes have been used;

but, such linings must be protected by gravel or soil cover.

When bentonite is used for the membrane, a high-swell

bentonite (sodium montmorillonite) is required. Acceptance

criteria for this material are contained in the specifications.

Compacted earth linings 150 or 300 mm (6 or 12 in) thick

usually satisfy design requirements from a seepage

standpoint; but, they require gravel cover or protection

against erosion and are relatively expensive because of

difficulty in compacting them on side slopes [17]. Of the
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

275

earth-type linings, heavy or thick compacted earth linings

have proved most desirable because:

 ̆ Conventional construction equipment and methods can

be used.

 ̆ Wider variety of soils may be used without erosion

protection.

 ̆ Lining is not easily destroyed by cleaning operations.

 ̆ Excellent seepage control can be achieved [16].

Heavy compacted earth lining is placed in the canal bottom

in 150-mm (6-in) compacted layers to a depth of 300 to

600 mm (1 to 2 ft) and on the canal slopes to a horizontal

width of 0.9 to 2.4 m (3 to 8 ft). In areas of potentially

serious frost action, a minimum lining thickness of 600 mm

is recommended. Sheepsfoot rollers are normally used for

compaction. When a thick compacted lining is placed on a

2h:1v slope about 750 mm (2 1/2 ft) of fully compacted

soil&normal to the 2:1 slope&is obtainable for an 2.4 m

(8 ft) horizontal width. In some instances, layers of

compacted fill on the side slopes are sloped downward

toward the canal to provide additional width needed for wider

rollers. The slope of the layers cannot be so steep as to

cause movement or segregation of the earth lining materials

during placing or compacting. Figure 3-32 shows a typical

canal section with compacted earth lining. Figure 3-33

shows a thick compacted earth lining under construction, and

the completed canal is shown on figure 3-34.

A wide range of impervious soils has been used successfully

for compacted earth linings. The most desirable soils

combine the most favorable properties of gradation,

plasticity, and impermeability.

 ̆ Best results are obtained from a WELL-GRADED

GRAVEL WITH SAND AND CLAY (GW-GC).

Good stability and erosion resistance characteristics

are provided by the well-graded, sandy-gravel fraction

as well as by the cohesive binder. The fines content

should be high enough to reduce seepage (12-20

percent).

 ̆ CLAYEY GRAVELS (GC) are next in quality.

 ̆ WELL-GRADED SAND WITH CLAY (SW-SC)

follows the above.

 ̆ CLAYEY SANDS (SC) is next in quality.

 ̆ SILTY GRAVELS (GM) have been used with

success.

The best materials contain just enough fines to make the soil

impervious and have sufficient gravel for erosion resistance.

Of the fine-grained soils, a LEAN CLAY (CL) is desirable

due to its imperability and workability.

A good cohesive binder usually means the soil must have

significant plasticity as measured by the plasticity index, PI.

However, some low PI (7 to 12 percent) earth linings have

performed reasonably well [18]. Additional side slope

protection (gravel or riprap) is always required on the outside

bank of curves and downstream of in-line structures and

sometimes on straight reaches.

The gravel cover layer sometimes used for erosion protection

of earth linings may vary from 150 to 300 mm (6 to 12 in)

thick. Pit-run sand and gravel up to 75 mm (3 in) in size and

containing a small amount of fines has been found

satisfactory. In some instances, placing a 150-mm-thick sand

and gravel filter layer on an open foundation structure has

been necessary to ensure that loss of earth lining material

would not occur. A WELL-GRADED GRAVEL WITH

SAND (GW) with a maximum size of 75 mm is used [17].

Usually, riprap or coarse gravel is required to protect wetted

earth surfaces in the vicinity of structures where high water

turbulence may occur. The material will vary in size and

thickness&depending upon degree of protection required&but

should be graded from the smallest to the largest particle

size.

The type of material considered suitable for covering buried

membranes depends on grade and velocity in the canal and

on steepness of side slopes. Cover materials must be stable

soils when saturated. Side slopes are normally 2h:1v or

flatter. In some cases, earth cover (sandy, silty, or clayey

soils) is adequate; in other cases, where erosive forces are

high, gravelly soil or gravel cover is required. Sometimes,

earth cover is placed directly on the membrane, and a gravel

cover is placed over the earth [19]. The total thickness of

cover is usually from 150 to 300 mm (6 to 12 in). The canal

subgrade must be relatively smooth&without abrupt breaks

or protruding materials&and open cobble structure must be

filled with a suitable finer filter material. Cover materials

must be carefully placed so the membrane is not punctured

or does not slip. Shear strength in the form of friction

between the different layers of material must be great enough

to prevent sliding of one material on the other. Laboratory

direct shear tests can be used to determine the interface

friction between different membrane and earth cover

materials. Installation of a buried geosynthetic membrane

lining is shown on figures 3-35 and 3-36.

3-30. Specifications Provisions.&

a. General.&The following paragraphs summarize

various standard specifications provisions used by

Reclamation for earthwork in canal construction. Their
EARTH MANUAL

276

Figure 3-32.—Typical canal section and compacted earth lining.

purpose is to clarify and to relate the different types of work.

However, this discussion should not be considered a

substitute for the published specifications for any particular

job. Each set of specifications includes only those standard

provisions that apply to the local situation; in addition,

modifications are made to fit each job.

b. Subgrades and Foundations for Embankments

and Compacted Earth Lining.&Provisions for canal

excavation require the contractor excavate to sections shown

on the drawings. If, because of undesirable bottom or slope

conditions, changes can be ordered for removal of unsuitable

material and for refilling as necessary.

Provisions for treatment of embankment foundations cover

required items of work like stripping, scarifying, and

compacting the foundation surface. Stripping includes

removing all material unsuitable for embankment foundation.

Necessary clearing of right-of-way, grubbing of stumps and

other vegetable matter and their roots, and burning or other

disposal of the material are required of the contractor.

As required, excavation for canals will allow slopes of

excavations and embankments for canals to be varied during

construction. Access ramps must not be cut into canal slopes

below the proposed water level in unlined canals or below

the top of the lining in lined canals. Above the canal section,

rock excavation need not be finished and will be allowed to

stand at its steepest safe angle. In unlined sections of canal

excavated in rock, sharp points of rock extending not more

than 150 mm (6 in) into the water prism are sometimes

permitted. Earth slopes are to be finished neatly to lines and

grades, either by cutting or by constructing earth

embankments.

Surfaces under all canal embankments, except for rock

surfaces, are required to be scored with a plow to make

furrows not more than 900 mm (3 ft) apart and not less than

200 mm (8 in) deep. For compacted embankments, the

entire foundation surface is scarified or disked to a depth of

not less than 150 mm (6 in) in lieu of scoring. Foundations

for embankments are stripped of unsuitable material.

c. Earth Embankments and Linings.&In

specifications for construction of earth embankments and

linings, general provisions are made to:

 ̆ Adhere to the dimensions shown on the drawings

 ̆ Provide allowance for settlement

 ̆ Grade the tops of canal banks

 ̆ Distribute gravel, cobbles, and boulders uniformly

throughout the fill
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

277

Figure 3-33.—Placing and compacting thick earth lining in Welton-Mohawk Canal in Arizona.

 ̆ Prohibit use of frozen materials and frozen working

surfaces for canal embankments and built-up canal

bottoms

Provisions are made for limiting the amount of backfill or

compacted backfill that can be placed about structures that

are built prior to excavation of the canal and construction of

canal embankment. Using all suitable materials from

excavations for construction of fills is required. Excess

material from excavation is used to strengthen canal

embankments or is wasted. Material, from cut not needed to

strengthen adjacent embankment and excavated material in

excess of requirements and unsuitable material, is deposited

in waste banks on Government right-of-way. Stockpiling of

suitable materials for use in earth linings or earth cover for

geomembrane linings may be required.

Where canal excavation at any section does not furnish

sufficient material for required fills, the contractor is

required to borrow materials from areas designated by the

Government. Adequate berms are left between embankment

toes and adjacent borrow pits with 1-1/2h:1v slopes in the

pits unless otherwise specified. Borrow pits may require

drainage by open ditches.

Specifications for earth canal embankments and linings

require that construction operations result in an acceptable

and uniform gradation of materials to provide for low

permeability and high stability when compacted, and that all

rock larger than maximum size specified [usually 75 or

125 mm (3 or 5 in)] be removed before compaction. These

requirements are particularly important in lining construction

because permeability is controlled by a relatively thin layer

of compacted soil. When blending fine-grained and coarsegrained soils (from different sources) is required to secure

the lining material desired, specifications usually require that

the fine soil be placed first, followed by the coarse soil, after

which the two are blended. This procedure is used so that
EARTH MANUAL

278

Figure 3-34.—Completed thick earth lining in Welton-Mohawk Canal in Arizona.

coarse lenses will not be left at the bottom of any finished

layer. Another requirement is that blending be accomplished

by a mixing machine built for the purpose of blending soils

or by equipment capable to produce comparable results and

specifically approved for the work. Weight of mixing

equipment is important because light-weight equipment rides

upward and is incapable of accomplishing proper blending.

An item covering excavation and refill of inspection trenches

is often provided in the specifications. This provision allows

proper inspection of materials, and blending and compaction

operations can be made from time to time, as required, to

ensure an acceptable lining product.

Sometimes, provisions are made for compacting clayey and

silty subgrade soils of low permeability for the base of a

compacted earth lining in the canal bottom. This base is

considered equivalent to about one 150-mm (6-in) compacted

layer in the canal bottom.

Construction of fills for canals in the forms of earth

embankments, linings, backfill, and refill is covered by a

number of specifications paragraphs. Table 3-3 summarizes

pertinent provisions and shows relationships among the

different types of fills.

d. Riprap, Protective Blankets, Gravel Fills, and

Gravel Subbase.&Riprap or a coarse gravel cover may be

required:

 ̆ On canal side slopes

 ̆ At in-line structures

 ̆ On the outside banks of curves

 ̆ In places where wind-generated waves may cause

erosion

 ̆ In areas where water velocity is otherwise high
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

279

Figure 3-36.—Placement of a protective earth cover over a geomembrane.

Figure 3-35.—Geomembrane being placed over prepared subgrade.
EARTH MANUAL

280

Table 3-3.—Materials and placing requirements for various fills used in canals

Type of construction

 and where used Material Placement requirements

Embankment not

to be compacted.

Not specified Approximate horizontal layers. If built by excavating and hauling equipment, travel

is routed over the embankment. If built by excavating machinery, thickness of

layer is limited to depth of material as deposited by excavating machine. Water

may be required, either added at site of excavation or by sprinkling of banks. 

Working may be required to secure uniformity of moisture and materials.

For lined and

unlined canals.

Embankment to 

be compacted.

Suitable material from

required excavation or

borrow; remove plus 125-

mm (+5-in) material; 

gradation must be

acceptable.

Prepare foundation; if clayey or silty soils, 150 mm (6 in) compacted thickness at

uniform optimum moisture; tamping rollers, 95-percent compaction. If

cohesionless and free-draining cohesionless and free-draining soils, horizontal

layers 150 mm (6 in) compacted thickness if rollers or tampers are used; 300 mm

(12 in) compacted thickness if tractor treads or other heavy vibrating equipment is

used; thorough wetting; 70-percent relative density.

For lined or unlined

canals.

Loose earth lining. Impervious soil from canal

excavation or borrow;

uniform mixture required;

depth of cut in borrow

areas to be designated;

uniform cutting of the face

of the excavation; no plus

75-mm (+3-in) rock; may

require blending.

Not specified.

For lined canals.

Compacted earth

lining.

Impervious soils from

canal excavation or

borrow; uniform mixture

required; depths of cut in

borrow areas to be

designated; uniform

cutting of the face of the

excavation; no plus

75-mm (+3-in) rock; may

require blending.

Prepare foundation; if clayey or silty soil, 150 mm (6 in) compacted thickness at

uniform optimum moisture; tamping rollers, 95-percent compaction.

For lined canals.

Refill above lining.

For lined canals.

Selected from excavation

or borrow.

Not specified.

Loose backfill.

About structures.

Approved material from

required excavation or

borrow.

Amount can be limited by the contracting officer; method of placement not

specified, but subject to approval.

Compacted backfill. Selected clayey and silty

material; from required

excavation or borrow; no

plus 75-mm (+3-in) rock.

Horizontal layers; compacted thickness at uniform optimum moisture shall not

exceed 150 mm (6 in) or two-thirds the length of roller tamping feet, whichever is

the lesser; compacted thickness shall not exceed 160 mm (4 in) where

compaction is performed by hand or power tampers; 95-percent compaction. About structures.

Selected cohesionless

free-draining material;

from required excavation

or borrow; no plus 75-mm

(+3-in) rock.

Horizontal layers 150 mm (6 in) compacted thickness if rollers or tampers are

used; 300 mm compacted thickness if tractor treads or surface vibrators are used;

and not more than the penetrating depth of the vibrator if internal vibrators are

used; wetting by hoses, flooding, or jetting is required; 70-percent relative density.
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

281

Riprap should be hard, durable, sound rock that is

predominantly angular and equidimensional. Reclamation

determines the durability of riprap by petrographic

examination and freeze-thaw durability testing [20]. If a

source of unknown quality is being considered,

representative samples of the material should be sent to the

Denver laboratories for testing. A guide for evaluating

potential riprap sources is presented in ASTM D 4992 [21].

Properly graded riprap will provide long-term, stable

protection. Gradation of rock particles should be well

distributed between the maximum and minimum sizes

permitted so placement will result in a firm mass with

minimum void spaces. (See sec. 3-24.)

A bedding layer of sand and gravel is normally required

between riprap and the embankment or lining. If the bedding

is designed as a filter, it will provide resistance to erosion

from runoff or wave action while serving as a stable base for

the riprap ([14], chs. 5 and 7). A geotextile may be used as

a filter, but a layer of sand and gravel is still required

between the riprap and the geotextile to protect the

geotextile.

For some canals, a coarse granular cover can be used as a

beach belt or as a complete cover for an earth lined canal.

This gravel protection not only protects the banks against

erosion and wave action, but also reduces maintenance for

weed control and improves the appearance of the canal.

Coarse gravel cover for a canal lining should:

 ̆ Have a maximum particle size between 75 and 150

mm (3 and 6 in)

 ̆ Have between 5 and 50 percent of particles passing a

4.75-mm (No. 4) sieve, 

 ̆ Contain 10 percent or less fines passing a 75-mm

(No. 200) sieve [22].

Gravel fills or gravel subbases can be pit-run gravel obtained

by the contractor from approved borrow sources on

Government right-of-way or from sources provided by the

contractor. The material should be less than 75 mm (3 in) in

size, reasonably well-graded, and contain a minimum amount

of fines. Sometimes, gradation limits are specified so there

is a reasonably good distribution of particle sizes from the

coarsest to the finest without a major deficiency of any size

or group of sizes. Uncompacted gravel fill is placed in

uniform layers to the required thickness. If compaction is

specified, it is accomplished according to the provision for

compacting cohesionless free-draining materials.

Provisions for one-course gravel surfacing (of prescribed

thickness), for operating roads and parking areas, require

material consisting of sand and gravel from which all rock

having a maximum dimension of more than 37.5 mm (1-1/2

in) have been removed. Material from gravel sources is

selected to include a sufficient quantity of natural

cementitious or binding material such that the surfacing will

bond readily under the action of traffic. The desirable

gradation conforms to ASTM D 1241 for Type I, Gradation

C, surface-course material that satisfies the requirements of

note 4 in D 1241 [23]. This gradation produces a good

distribution of all particle sizes with 8 to 15 percent fines to

provide imperviousness and binding material. These fines

are recommended to be in a limited range of plasticity such

that the PI is from 4 to 9, and the liquid limit, LL, is less

than 35. Surfaces to receive the gravel surfacing should be

bladed or dragged to secure a uniform subgrade. Surfacing

material is placed and spread uniformly on the prepared

subgrade to required depth and dimensions and moistened if

required. Geosynthetic fabrics may be used between the

subgrade and surfacing material to improve performance of

the surfacing material. Usually, minimum compaction is

required such as routing hauling and construction equipment

over the entire width of surfacing to distribute the

compacting effect of equipment to the best advantage.

However, where imperviousness and wearing surface are

important, the higher degree of compaction usually specified

for roller compaction is required.

3-31. Control Techniques.&

a. General.&Recognition of the importance of

controlling earth placement in embankments and canal linings

has increased concurrently with knowledge of factors

affecting stability of such structures. Not only must the

inspector be thoroughly familiar with provisions of the

specifications, but one must have a good understanding of

design and construction principles involved and of field and

laboratory tests used for control. The inspector should:

 ̆ Obtain all available information on design assumptions

 ̆ Obtain letters of instruction, laboratory reports, other

reports, and specifications

 ̆ Check whether field conditions revealed are

compatible with assumptions made on the basis of

preconstruction investigations

The principles are equally applicable to foundations, whether

under earth or concrete structures.

b. Subgrades and Embankment Foundations.&The

subgrade and embankment foundation for a canal may consist

of rock or soil. Canal sections excavated in rock should be

inspected to determine whether open structure or fissures

exist that will cause excessive seepage or piping which would

require canal to be lined. Rock foundation surfaces on which
EARTH MANUAL

282

compacted earth is to be placed should be moistened before

placing the first layer of earth, but standing water should not

be allowed.

When canal sections are excavated in soils, or embankments

are constructed on soil foundations, greater care is required

for inspection than for rock subgrades and foundations

because of the nature of the material. In addition to noting

possible seepage or piping conditions, the inspector must

identify and locate conditions that could lead to large

settlement and slope instability. During investigations for

design of a canal, it is not economically possible to

predetermine all conditions which may be encountered.

Therefore, during excavation or stripping operations, the

inspector should call to the attention of supervisors the

necessity for:

 ̆ Additional exploratory holes

 ̆ Field penetration tests

 ̆ Permeability or density tests

 ̆ Other sampling and tests

to determine the extent of any materials of doubtful

suitability for the foundation of embankments, for cut slopes,

or for canal subgrades.

Some canal specifications require that reaches of canal to be

lined shall be determined immediately in advance of

construction by exploratory excavations, such as bulldozer or

backhoe trenches dug by the contractor. In such cases, the

inspector must be familiar with the permeability

characteristics of soils encountered, making use of in-place

permeability tests as required.

The inspector should examine canal subgrade soils on canal

slopes and bottom with respect to possible future seepage and

erosion. If high seepage losses are anticipated or if soils may

be anticipated, to erode badly under proposed operating

conditions, the inspector should call these facts to the

attention of supervisors. If, upon further consideration, these

conditions appear to be critical, advice from the designers

should be sought. Lined sections in areas of high ground

water must be protected against uplift by using drainage

systems, and these are normally specified. If such areas

previously unknown are observed during construction,

provisions should be made for installing pressure relief

devices. Similarly, when high ground water is encountered

near silty or fine sandy subgrade soils of concrete-lined

sections in freezing climates, attention should be directed to

this fact so frost-action preventive measures can be instituted,

if necessary.

If fine-grained soils are to be placed as a sublining under

concrete or membrane linings, or will be used for earth

linings, the natural subgrade should be inspected for open

voids as in cobbly soils or fissure formations into which the

fine soil might erode. In such cases, the inspector should call

the conditions to the attention of supervisors so filter blankets

or geosynthetic filters can be installed.

The inspector should make certain that all organic matter and

any soils that may become unstable upon saturation, such as

highly organic soils, loose silts, fine sands, and expansive

clays, are removed or properly treated for embankments and

canal linings to the extent necessary to provide a safe, stable

foundation or subgrade under operating conditions.

Specifications requirements for stripping and scoring earth

foundations for all canal embankments, and special treatment

for preparation of foundation surfaces for compacted

embankments and earth linings, are important details that

require careful visual inspection during construction.

Determination of depth of stripping requires experience and

good judgment because of compromise between what would

be desirable from a design standpoint and excessive cost.

Good bond between the foundation and first layer of fill is

achieved by moistening the foundation rather than using a

very wet embankment layer.

Foundation control information should be included in the

earthwork portion of the monthly construction progress

report (L-29). If field density tests are made, the data can be

reported along with the compacted earthwork control data

(forms 7-1581A and 7-1581B), if properly identified. Other

test data, logs of holes, and observations can be included in

the narrative portion of the report. The forms above are

examples of how results of field and laboratory tests

performed in conjunction with construction control are

reported. Form 7-1581A is used when the materials are

controlled using USBR 7240: Performing Rapid Method of

Construction Control, 1

 or by USBR 5500 and 5515

laboratory compaction of soils. 2

 Form 7-1581B is for

materials controlled using USBR 5525, 5530 (minimum and

maximum index density), and USBR 7250: Determination of

Percent Relative Density. 3

 Other forms, such as those

1

 7240: Performing Rapid Method of Construction Control.

2

 5500: Performing Laboratory Compaction of Soils&5.5-lbm

Rammer and 18-in Drop.

5515: Performing Laboratory Compaction of Soils Containing

Gravel. 3

 5525: Determining the Minimum Index Unit Weight of

Cohesionless Soils.

5530: Determining the Maximum Index Unit Weight of Cohesionless

Soils.

7250: Determination of Percent Relative Density.
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

283

generated by computer program PCEARTH (see sec. 3-27),

can be used as long as all pertinent information is shown.

Information on current computer software programs is

available and can be obtained from the Denver Office.

c. Earth Embankments and Linings.&Depending

upon design requirements, earth embankments for canals and

laterals may consist of impervious or pervious soils placed

loose, partially compacted by equipment or well compacted

by rollers, or a combination of these. Earthwork control

inspection of loose embankments consists only of making

sure that proper types of materials are being used, that

material is uniformly placed, and that layers are of proper

thickness when layer thickness is specified. Normally, the

finest available material is placed on the canal prism side,

and coarser materials are placed toward the outside of the

embankment. When specifications require partial

compaction by routing equipment, inspection requirements

noted above are applicable, and the inspector should make

sure that hauling and spreading equipment is routed so as to

provide the most uniform coverage and best compaction. In

some instances, uniform moistening of partially compacted

fill material is specified. Normally, the water required is

that amount which will provide a total moisture equivalent to

optimum moisture content for the compactive effort being

applied. Standard laboratory optimum moisture content may

be used. Density tests are not taken for fill placed in this

manner.

Control of compacted impermeable soils in embankment and

compacted earth lining consists of:

 ̆ Inspecting materials used

 ̆ Checking amount and uniformity of soil moisture

 ̆ Maintaining thickness of layer

 ̆ Determining the percentage of standard laboratory

maximum dry density of the fill

Using the available logs of explorations and careful

observation of excavations for the canal, appurtenant

structures and borrow areas will be useful in selecting the

best soils for use in compacted embankments and earth

linings. In borrow areas, the depth of cut can be regulated

to obtain high quality and uniformity of soil. Deposition of

each load of material on the fill is directed to control

uniformity. The thickness of loose lift required to result in

a 150-mm (6-in) compacted layer must be determined and

regularly checked.

Blending of two or more materials is sometimes specified to

produce suitable soils for earth linings. Most commonly,

fine soil from borrow is added to pervious coarse soils

obtained from excavation to decrease permeability. Coarse

soils from borrow may be added to soils from excavation to

improve erosion resistance for lining or cover purposes.

Proportions of soils to be blended are determined earlier by

laboratory testing. The inspector has responsibility to ensure

that materials are properly proportioned and mixed.

Normally, excavation materials, to be used for one of the

blended materials, are required to be completely removed

from the section and to be placed in the lining layer to the

depth required for proper proportioning. The correct depth

of fine soil is placed first, followed by the correct depth of

coarse soil; then, blending is allowed.

Generally, blending is specified to be done by a machine

designed for mixing soils or by other equipment which

obtains comparable results. Therefore, the inspector must

ensure that equipment being used provides a uniform blend

of soils for the total layer depth. This is done by frequently

digging holes through the blended layer before compaction to

observe uniformity of the layer after blending. When soils

of different colors are blended, color of the mixture at

different depths in the layer is a useful index indicating

effectiveness of the mixing operation. Compaction should

not be allowed to proceed until a satisfactory blend has been

attained. Inspection trenches should be requested frequently

at the beginning of a blended lining contract, and at lesser

frequency as the job progresses, so results of the contractor' s

blending and lining operations can be visually observed.

Cobbles larger than specified, usually 75 or 125 mm (3 or

5 in), must be removed before compaction. This is

especially important in all types of compacted earth linings

where a relatively thin section is relied upon for seepage

control. Pockets of cobbles provide certain access for water

loss and piping. Often, cobbles are buried in the layer being

placed and are difficult to detect or to remove. Therefore,

if the percentage of oversize material is large, some means

should be provided for removing this material at the point of

excavation.

The inspector is responsible for controlling water content of

the soil to that which is "optimum for compaction" and to

ensure that moisture is uniform throughout the layer to be

compacted. If the soil is several percentage points dry of

desired moisture content, it is more efficient to add most of

the water at the location of excavation with only

supplemental sprinkling after the layer has been spread.

After sprinkling, mixing is required to produce a uniform

moisture condition throughout the layer before compaction

can proceed. Moisture uniformity should be evaluated

frequently by digging holes in the loose layer just before

compaction. Unless otherwise specified, optimum moisture

requirements must be enforced for canal embankments and

linings even though required density can be obtained at other
EARTH MANUAL

284

moisture conditions. Adverse settlement and permeability

properties may result if placement moisture is too low; and

adverse shear strength properties may result if placement

moisture is too high. Therefore, the inspector must be

prepared to request application or removal of moisture, as

required.

Control of pervious material includes visual inspection of

material for free-draining characteristics and uniformity of

material. Thickness of layer is controlled, depending on type

of compaction. A thickness of:

 ̆ Not more than 150 mm (6 in) after compaction is

specified if smooth or pneumatic-tire rollers are used

 ̆ Not more than 300 mm (12 in) after compaction is

specified if vibrating rollers or tractor treads are used

 ̆ Length of vibrator if internal vibrators are used

Each layer must be thoroughly wetted during the compaction

operation for all types of compaction.

Adequacy of compaction and moisture control of impervious

or pervious soils is controlled by field density test USBR

7205 or 7220 in conjunction with USBR 7240 Performing

Rapid Method of Construction Control for clayey and silty

soils, 4

 or the relative density tests USBR 5525, 5530, and

7250 for pervious sand and gravel soils. 5

 Unless otherwise

specified, minimum acceptable density is 95-percent

laboratory maximum density for the minus 4.75 mm (-No. 4)

fraction of clayey and silty soils and 70-percent relative

density for the minus 75-mm (-3-in) fraction of pervious sand

and gravel soils. For soils that are borderline between silty

and clayey soils controlled by the compaction test and

pervious sand and gravel soils controlled by the relative

density test, control is based on either 95-percent laboratory

maximum density or 70-percent relative density, whichever

produces the highest in-place density. Table 3-1 is a guide

for determining materials for which the relative density test

is applicable.

Inasmuch as the adequacy of compaction is specified in terms

of soil density achieved, the inspector is responsible to

arrange or perform sufficient tests to ensure adequacy of

compaction for acceptance purposes. At the beginning of

any work, a considerable number of tests are required to

ensure construction operations are producing required

results. Then, the number of tests required is that necessary

to ensure that specifications requirements are being satisfied.

Because of the widespread operations of canal work, the

number of field density tests required for adequate control

cannot be positively stated. The following is a guide for the

minimum number of field density tests:

 ̆ For all types of earthwork, one test for each work

shift

 ̆ For canal embankments, one test for each 2,000 m3

(2,000 yd3)

 ̆ For compacted canal linings, one test for each

1,000 m3

 (1,000 yd3)

 ̆ For compacted backfill or for refill beneath structures:

i. Hand tamped (mechanical tamping), one test for

each 200 m3

 (200 yd3)

ii. Roller or tractor compacted, one test for each

1,000 m3

 (1000 yd3)

 ̆ One complete permeability settlement test should be

made in the laboratory for each 10 density tests for

compacted canal linings, impervious embankments,

and impervious backfill.

When field density tests are performed in relatively narrow

compacted earth linings where equipment travel is essentially

along a constant route, density tests should not be taken in

the tractor or wheel tracks. At such locations, density may

be considerably higher than the average density of normally

rolled lining.

Horizontal and vertical control must be available so the

inspector can adequately locate each field density test.

Usually, locations are defined in terms of station, offset from

canal (or structure) centerline, and elevation above bottom

grade. The inspector is responsible for locating these tests so

a complete representative record of finished work is

available. Companion laboratory tests by the rapid method

of construction control for clayey and silty soils and relative

density tests for free-draining sand and gravel soils should be

made for each density test. A laboratory compaction test or

a relative density test is required for each control field

density test so the percent compaction or relative density,

respectively, can be computed.

4

 7205: Determining Unit Weight of Soils In-Place by the Sand-Cone

Method

7220: Determining Unit Weight of Soils In-Place by the Sand

Replacement Method in a Test Pit

7240: Performing Rapid Method of Construction Control

5

 5525: Determining the Minimum Index Unit Weight of

Cohesionless Soils

5530: Determining the Maximum Index Unit Weight of Cohesionless

Soils

7250: Determination of Percent Relative Density
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

285

F. Pipelines

3-32. Design Features.&Reclamation uses buried

pipelines for pumping plant discharge lines, irrigation

laterals, and distribution systems for domestic, municipal,

and industrial deliveries. These systems may be constructed

using one or more types of pipe such as:

 ̆ Reinforced concrete pipe

 ̆ Reinforced concrete cylinder pipe

 ̆ Steel pipe with a number of combinations of coatings

and linings

 ̆ Pretensioned concrete cylinder pipe

 ̆ Ductile iron pipe

 ̆ Fiberglass pipe

 ̆ Polyvinyl chloride (PVC) pipe

 ̆ High-density polyethylene (HDPE) corrugated pipe

Usually, the type of pipe is selected by the contractor from

several acceptable types described in Reclamation

specifications.

Buried pipe is a structure that incorporates both the

properties of the pipe and the properties of the soil

surrounding the pipe. Structural design of a pipeline is based

on certain soil conditions; construction control is important

to ensure these conditions are satisfied. Two basic types of

pipe are used&rigid and flexible. Pipe of 250-mm (10-in)

nominal inside diameter and smaller can be considered either

rigid or flexible, but Reclamation designs this size pipe to be

relatively independent of soil conditions. Installation

requirements for pipe are different for each condition: rigid,

flexible, and 250-mm diameter and smaller. Rigid pipe must

be supported on the bottom portion of the pipe. Flexible pipe

must be supported both on the bottom and on the sides of the

pipe.

Rigid pipe includes:

 ̆ Reinforced concrete pressure pipe

 ̆ Ductile iron pipe 500 mm (20 in) and less in diameter

 ̆ Reinforced concrete cylinder pipe

Rigid pipe is designed to transmit the backfill load on the

pipe through the pipe walls to the foundation beneath the

pipe. The pipe walls must be strong enough to carry this

load. A concentrated load at the top and bottom of the pipe

is the worst possible loading case. If load can be distributed

over a larger area on the top and at the bottom of the pipe,

the pipe walls do not have to be designed as strong as for a

concentrated load. Normally, soil backfill load is well

distributed over the top of the pipe. However, proper

support must be constructed on the bottom of the pipe to

distribute the load. Proper soil support on the bottom of the

pipe is necessary to maintain the grade of the pipe and to

prevent unequal settlement.

Flexible pipe includes:

 ̆ Steel pipe

 ̆ Pretensioned concrete cylinder pipe

 ̆ Ductile iron pipe over 500 mm (20 in) in diameter

 ̆ Fiberglass pipe

 ̆ PVC pipe

 ̆ HDPE corrugated pipe

Generally, steel pipe is lined with cement-mortar, either in

the factory or in place after installation. The coating can be

cement-mortar or some type of flexible coating such as

polyethylene tape wrap.

Flexible pipe is designed to transmit the load on the pipe to

the soil at the sides of the pipe. As load on the pipe

increases, the vertical diameter of the pipe decreases, and the

horizontal diameter increases. The increase in horizontal

diameter is resisted by the soil at the sides of the pipe.

Adequate soil support on the sides of the pipe is essential for

proper performance of the pipe. The side-soil support must

be strong enough to carry the applied load without allowing

the pipe to deflect more than the allowable amount for the

specific type of pipe. Proper soil support on the bottom of

the pipe is necessary to maintain the grade of the pipe and to

provide uniform support.

Pipe 250-mm (10-in) nominal inside diameter and smaller do

not require any compaction of the soil placed around the

pipe. While pipe less than 250 mm may be a type otherwise

considered rigid or flexible, Reclamation designs pipe of this

size to be strong enough to withstand the backfill load

without any special soil support. Figure 3-37 shows typical

installation requirements for pipe 250-mm diameter and

smaller. Pipe 250-mm diameter and smaller includes PVC,

steel, and ductile iron.

3-33. Specifications Provisions.&Typical trench

details for buried pipe are shown on figure 3-38. The

specifications describe type of soil and compaction

requirements for the foundation, bedding, embedment, and

backfill.

The foundation is the in-place material beneath the pipe. If

the foundation is unsuitable, a minimum of 150 mm (6 in) of
EARTH MANUAL

286

Figure 3-37.—Installation requirements of pipe 250-mm in diameter and smaller.

material must be removed and replaced with compacted

material. Removal and replacement of material to 1 to 2 m

(3 to 6 ft) depth or more may be necessary to attain a suitable

foundation for the pipe.

Unsuitable foundations include potentially expansive material

such as shale, mudstone, siltstone, claystone, or dry, dense

fat clay (CH). These materials may expand when wetted.

Uplift pressures created from expansion of these materials

have been known to cause broken backs in rigid pipe.

Another type of unsuitable foundation includes soft, unstable

soils such as very wet soils that flow into the excavation,

low-density soils, peat or other organic material. A soft,

unstable foundation may result in uneven settlement of the

pipe. Low-density soils may collapse upon wetting. Very

wet, unstable soils must be removed to provide a stable

foundation that will maintain grade and provide uniform

support for the pipe. Peat or other organic soils are highly

compressible; significant settling of the pipe may occur if

these soils are left in the foundation. Foundation materials

disturbed during construction must be removed and replaced

with material that is compacted.

Material is placed and compacted to replace the excavated

foundation. Fat clays (CH) must not be used because

moisture changes can cause significant volume increase or

decrease. Elastic silts (MH), peat, or other organic material

must not be used because they are highly compressible; nor

should frozen soils be used. Material that allows migration

of fines should not be used for a replaced foundation; for

example, a crushed rock or gravel material containing

significant voids should not be placed next to a fine-grained

material. The fine-grained material can migrate into the

voids and result in the rock particles floating in a matrix of

fine-grained material. This would cause loss of support for
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

287

Figure 3-38.—Typical trench details.

the pipe and result in uneven settlement. Any method of

compacting the replaced foundation may be used; however,

specified density requirements must be satisfied.

For both rigid and flexible pipe, the bedding is a layer of

uncompacted select material placed over the foundation (or

the replaced foundation). The pipe is laid on the

uncompacted bedding. For pipe diameters between 300 and

1,375 mm (12 and 54 in), bedding is 100 mm (4 in) thick. 

For pipe diameters 1,525 mm (60 in) and over, bedding is

150 mm (6 in) thick.

The surface of the bedding shall be fine graded so that the

final grade of the pipe does not exceed specified departure

from grade. Settlement of the pipe into the uncompacted

bedding soil must be taken into account. For bell-and-spigot

jointed pipe, "bell holes" must be excavated in the bedding

to provide a space between the bottom of the bell and any

soil. This may require that material beneath the bedding also
EARTH MANUAL

288

be excavated. This bell hole prevents a point loading

condition on the bell end of the pipe.

After laying the pipe on the bedding, embedment soil is

compacted underneath and beside the pipe up to the specified

height. For rigid pipe, embedment soil is placed and

compacted to a height of 0.37 units of the outside diameter of

the pipe. Embedment soil must be a select material and must

be compacted to a relative density not less than 70 percent.

It is important that soil placed in the haunch area of the pipe

receive sufficient compactive effort to meet the 70-percent

relative density requirement. Compaction by saturation and

internal vibration is an effective method of working the select

material into the haunch area and of obtaining the required

density. For flexible pipe, embedment soil is placed to a

height of 0.7 units of the outside diameter of the pipe.

The select material used for pipe embedment must be

cohesionless and free-draining (5 percent fines or less), have

a maximum size of 19.0 mm (3/4 in), and not more than

25 percent of the soil shall pass a 300 μm (No. 50) sieve.

Where the pipeline grade exceeds 0.3 units, silty or clayey

material may be used instead of the specified select material

for bedding and embedment. This change is allowed because

of the difficulty encountered in compacting by saturation and

vibration on steep slopes. If cohesive soil is used for bedding

or embedment, density requirements must still be satisfied;

the inspector must be sure that soil placed in the haunch areas

is compacted as specified.

Most soil types may be used for backfill over the pipe,

except there are maximum particle size restrictions. A limit

is placed on the maximum particle size (limitation depends on

type of pipe) in a zone 300 mm (12 in) around the pipe.

Outside this zone, any rock particle with any dimension

greater than 450 mm (18 in) is not allowed in the backfill.

Frozen soils shall not be used. Where backfill is to be

compacted to the ground surface, such as at road crossings,

peat or other organic materials shall not be used. Local

requirements for compacted backfill under roads must be

satisfied. Backfill material must not be dropped on the pipe.

3-34. Construction Control.&Soil placed against the

pipe must be in firm, complete contact with the pipe.

Compacting soil in the haunch area of a pipe is the most

difficult part of pipeline construction; this compaction must

be carefully monitored. A test pit should be dug at regular

intervals to inspect the haunch area and to determine density

of soil in the haunch area. When using saturation and

vibration, the area under the bottom of the pipe must be

inspected to ensure the pipe did not "float" during

construction. "Bell holes" for bell-and-spigot pipe, sling

holes for large diameter pipe, and spaces left for joint

treatment&for other than bell-and-spigot pipe&must be filled

after the pipe is laid. Embedment soil must be compacted the

complete width of the trench. Embedment soil shall be

placed to about the same elevation on both sides of the pipe

to prevent unequal loading and displacement of the pipe.

Where trenches have been left open at pipe-structure

junctions, requirements (as previously stated) for pipe

embedment must be continued to the structure after it is

constructed but before the excavation is backfilled.

For silty or clayey soils, the thickness of each horizontal

layer after compaction shall not exceed 150 mm (6 in). For

cohesionless, free-draining material such as sands and

gravels, the thickness of the horizontal layer&after

compaction&shall not exceed:

 ̆ 150 mm if compaction is performed by tampers or

rollers

 ̆ More than 150 mm if compaction is performed by

treads of crawler-type tractors, surface vibrators, or

similar equipment

 ̆ More than the penetrating depth of the vibrator if

compaction is performed by internal vibrators

Backfill over the pipe should be placed to a minimum depth

of 1 m (3 ft) or one-half pipe diameter (whichever is greater)

above the top of the pipe before power-operated hauling or

rolling equipment is allowed over the pipe. In addition,

limitations may be imposed on weight of equipment traveling

over the pipeline. Equipment crossings, detours, or haul

roads crossing the pipeline must be approved prior to use.

Pipe 250-mm (10-in) diameter and smaller can withstand the

weight of backfill without special soil support. Compacted

soil around this pipe is used only on the outside of horizontal

curves or where the pipe crosses under another conduit, and

under a roadway, canal, ditch, or structure. Previous

comments on adequacy of a foundation, however, still

pertain to 250-mm pipe.

For pipe 80 to 250 mm (3 to 10 in) in diameter, 100 mm

(4 in) of uncompacted material are required as bedding

between the pipe and the foundation. Maximum particle size

of the bedding material is 19.0 mm (3/4 in). Peat or other

organic material shall not be used as bedding. The

uncompacted material can be imported or the bottom of the

excavation can be loosened by scarifying if the in-place

material is suitable. The main requirement for pipe 250 mm

and smaller is suitability of the foundation.
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

289

3-35. Construction Control Requirements.&

Trench dimensions, minimum installation width, slope of the

trench walls, trench depth, and side clearance of flexible pipe

must always be carefully checked.

A minimum installation width, W, is specified to ensure a

minimum distance between the pipe and the trench wall.

Enough clearance must be allowed to inspect pipe joints and

to compact the embedment. This clearance is particularly

critical for vertical trench walls. Minimum installation width

is measured at the top of the foundation. For trench slopes,

the most recent Reclamation or Office of Safety and Health

Administration requirements should be consulted. However,

State or local regulations may override these requirements.

The trench wall slope must begin at the bottom of the

excavation, which includes any additional excavation of

foundation material.

For flexible pipe, side clearance between the pipe at the

springline and the trench wall must be checked for all

conditions, including shored trenches, sloping trench walls,

and vertical walls. This clearance is required in addition to

the minimum installation width and may require, in some

cases, a wider trench bottom than the minimum installation

width.

Performance of flexible pipe depends on soil at the sides of

the pipe for support [24]. This side soil support results from

the combination of embedment and trench wall soil. The

width of the trench depends on the relative firmness of

embedment and trench wall material. If the trench walls are

firmer than the embedment, embedment soil is used to fill the

space between the pipe and the trench walls. If the trench

walls are soft and easily compressible, most of the side soil

support must come from the embedment. As shown on

figure 3-39, three types of trenches are specified which state

the minimum clearance between the pipe and the trench wall

measured at springline of the pipe [25].

Trench type 1 is where trench wall material is stronger or

firmer than the embedment. Typical trench wall materials

would be rock; materials described as:

 ̆ Claystone, mudstone, or siltstone

 ̆ Strongly cemented soils even though of low density

 ̆ Cohesionless soils with in-place relative densities over

70 percent

 ̆ Silty or clayey material with in-place densities over

95 percent compaction

For trench type 1 installation, minimum side clearance is 250

mm (10 in) for pipe 450 mm (18 in) and smaller, and 450

mm for pipe larger than 450-mm diameter.

Trench type 2 is where trench wall soil has a strength or

firmness equivalent to the embedment. These soils include:

 ̆ Silty or clayey material with in-place densities less

than 95 percent compaction&but over 85 percent

compaction

 ̆ Cohesionless soils with in-place relative densities

between 40 and 70 percent

Minimum side clearance for trench type 2 installation is

equal to the outside diameter of the pipe.

Trench type 3 is where trench walls are much softer than the

embedment. Soils in this category include:

 ̆ Peat or other organic soils

 ̆ Elastic silts (MH)

 ̆ Low-density silty or clayey material (below 85 percent

compaction)

 ̆ Low-density cohesionless soils (below 40 percent

relative density)

Minimum side clearance for trench type 3 is equal to two

pipe outside diameters&making a total trench width of five

pipe diameters measured at pipe springline. Generally, this

is impractical so, in trench type 3 areas, rigid pipe may be

specified. During construction, if unexpected areas of trench

type 3 conditions are encountered, changes to the type of

pipe or method of construction must be made to obtain a

proper installation.

During investigations where types 2 or 3 trench may be

required, areas along the pipeline must be identified.

Particular attention should be paid to stream crossings,

loessal deposits, talus slopes, and landfills.

The specifications requirements pertain to one method of

pipeline construction acceptable to Reclamation. Other

acceptable installation techniques may be used. Sometimes,

pipe design may have to be changed to be compatible with

the installation method. It is not uncommon to provide a

stiffer pipe than specified, so the density requirement for

embedment may be lowered.

3-36. Soil-Cement Slurry Pipe Bedding.&When

conditions warrant, the contractor may choose to install pipe

using soil-cement slurry as an alternate to the standard

compacted soil embedment. The trench is trimmed to a

semicircular cross section (or other approved shape) slightly

larger than the pipe (as shown on figure 3-40). A

soil-cement slurry is used to fill the gap between the pipe and

the in place soil. Since soil-cement transfers the load from
EARTH MANUAL

290

Figure 3-39.—Side clearance requirements for flexible pipe.
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

291

Figure 3-40.—Soil-cement slurry installation.

the pipe to the trench material, the native soil must be able to

provide the necessary support for the pipe. Typically, inplace materials that categorize as trench type 1 would

qualify.

The trimmed shape is advantageous because it reduces

excavation quantities and handling of excavated soil. Placing

soil-cement slurry is quicker than replacing and compacting

soil beneath and beside the pipe. This faster installation is a

distinct advantage where construction work space is limited

or where time of installation is critical.

Soil-cement slurry is a combination of soil, portland cement,

and enough water so the mixture has the consistency of a

thick liquid. In this form, the slurry flows readily into

openings and provides a hardened material with strength

greater than the in place soil.

Allowable ingredients and specific placement requirements

are given in the construction specifications. Typically,

soil-cement slurry contains about 6 to 10 percent portland

cement by dry mass of soil. Some cementitious fly ashes

have been successfully used in place of cement.

One distinct advantage in using soil-cement slurry is that soilcement may be produced using local soils. The soil can

contain up to 30 percent nonplastic or slightly plastic fines.

Although clean, concrete sands have been used, the presence

of fines helps keep the sand-size particles in suspension.

This allows the mixture to flow easier and helps prevent

segregation. The allowable maximum particle size, limit of

organic material, and other requirements are usually

specified.

Soil-cement slurry typically has a water-cement ratio of about

2.5 to 3.5 to attain required flow properties. Generally,

internal vibrators are used to ensure that the slurry

completely fills the annular space around the pipe.

Central batch plants&with the slurry delivered in ready-mix

trucks&or portable batch plants have been used to mix soilcement with the latter normally used when soil comes from

trench excavation. Materials to be used and method of

mixing depend on availability of local materials and

equipment.

Construction control of soil-cement slurry involves only two

factors: (1) proper proportioning of the mixture and
EARTH MANUAL

292

(2) ensuring that the slurry completely fills the annulus

between pipe and trench walls. Proper mixture is checked by

determining the unconfined compressive strength at 7 days

for minimum and maximum strength requirements of 700 and

1,400 kPa (100 and 200 lbf/in2

). Higher strength is not

desirable because structural characteristics of the pipe may be

altered.

G. Miscellaneous Construction Features

3-37. Highways and Railroads.&During

construction, public utilities, communication systems, or

transportation systems (including highways and railroads)

may need to be relocated. Normally, a relocation agreement

is entered into with the owner of the facility. Provisions of

the relocation agreement will require either the owner or

Reclamation to design and construct the relocation of

facilities according to design and construction standard

agreed upon.

a. Design Features.&The design of a highway or

railroad consists of selecting and laying out the roadway or

roadbed alignment, designing and detailing required

structures, and preparing specifications for constructing the

facility. As a basis for agreement on the design and

construction of relocated highways, Reclamation uses

American Association of State Highway and Transportation

Officials standards and manuals, the standards of the state

highway departments, and general highway construction

practice. For the design and construction of relocated and

access railroads, Reclamation uses American Railway

Engineering Association manuals, the railroad' s own

standards, and general railroad construction practice.

Access roads for use by the contractor and the Government

are designed and constructed by Reclamation according to

Reclamation standards. These standards are based on local

proven methods of road construction which permit using

local materials and services of local contractors experienced

with construction equipment designed for such work.

b. Earthwork Specifications Provisions.&

Specifications for constructing a railroad or highway will

contain a paragraph on roadway excavation. This paragraph

will require the contractor to construct the roadway to

dimensions shown on drawings or as staked and to prescribed

lines and grades. Drawings include profiles of gradelines

either to finished grade or to subgrade. The term "subgrade"

refers to the top of embankments and to the bottom of

excavations ready to receive the roadway surface or the

railroad ballast. In rock excavation, the bottom of the cut is

excavated to 150 mm (6 in) below subgrade; and, in common

excavation, all loose rock fragments, cobbles, and boulders

are removed or excavated to a depth of not less than 150 mm

(6 inches) below subgrade.

Excavation below subgrade is refilled to subgrade with

material obtained from excavation for the roadway or from

borrow pits; the refilled material is compacted equivalent to

the compaction required for embankments. Provisions are

made in the paragraph on roadway excavation for dealing

with slopes shattered or loosened by blasting and slides

extending beyond the established slope lines or below

subgrade. Provisions for constructing side drains and for

excavating around trees, poles, or other objects that are to

remain within the right-of-way for the roadway are also

given in the paragraph on roadway excavation.

Provisions are included in paragraphs on preparation of

surfaces under roadway embankments for surface treatment

and for removal of unsuitable materials. Surfaces of sloping

ground underneath embankments must provide bond with the

embankments and to prevent slipping. Where embankments

placed on smooth, firm surfaces and where low embankments

are placed, the original ground surface is thoroughly plowed

or stepped to ensure proper bonding of new and existing

material. When embankments are placed on steep rock

slopes, trenches are blasted into the rock surface for

"keying" the embankment to the rock surface. The

contractor must strip the area under an embankment of all

unsuitable material to depths as directed.

Roadway embankments are constructed to established lines

and grades and increased by such heights and widths as

necessary to allow for settlement. Brush, roots, stumps, sod,

or other unsuitable materials are not permitted in

embankments. Hard material or hard lumps of earth more

than 300 mm (12 in) in size must be broken down, or

removed, and boulders and cobbles more than 150 mm (6 in)

in diameter are not permitted in the upper 600 mm

(24 inches) of embankment. Given a choice of materials, the

best are used in the upper 300 mm of the embankment.

Material is not permitted in embankments when either the

material or the surface on which it is to be placed is frozen.

Good distribution of cobbles and gravel within the

embankment is required when such material is being used.

Rockfill embankments are constructed so large spaces are not
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

293

unfilled. When directed, rock fragments are deposited in the

outer portions of embankments to protect the slopes against

erosion.

The contractor' s combined excavation and placing operations

should ensure that material in the embankment will be

blended sufficiently to secure the best possible degree of

compaction and stability. The required thickness of layers is

300 mm (12 in) after compaction for earthfill and not more

than 600 mm (24 in) after compaction for rockfill. Layers

are constructed across the entire width of embankments and

must be built to the required slopes rather than widened with

loose material dumped from the top. On sidehill fills, where

the width is too narrow to accommodate hauling equipment,

end dumping is used until the width of the embankment

becomes great enough to permit using hauling equipment.

The contractor is required to route hauling equipment over

the layers already in place and to direct travel evenly over

the entire width of the embankment so as to obtain the

maximum amount of compaction possible.

Moistening and compacting roadway embankments may be

necessary where normal construction techniques will not

result in proper densification. Where sufficient moisture is

not available in the material, additional water must be

provided by sprinkling as the layers of material are placed on

the embankments. Moistening must be uniform; harrowing,

disking, or other working may be necessary to produce a

uniform moisture content. Material containing excess

moisture must be permitted to dry to the extent required

before being compacted.

The amount of embankment rolling depends on the nature of

the material compacted and the extent of compaction

required; rolling will be specified for each embankment or

portion of an embankment. Reclamation usually follows

State highway specifications when embankments are built for

a State highway department. Generally, highway department

specifications are of the performance type where only the end

result is specified. For this type of specification, the

contractor usually selects the equipment to obtain the end

result. If highway and railroad embankments are not built

according to State specifications, Reclamation will build

them using an end-result type of specification requiring the

fill to be compacted to 95 percent laboratory maximum dry

density.

Additional material for construction of embankments and for

excavation refills in rock cuts is obtained by widening the

cuts, flattening the slopes on either or both sides of the

centerline, or from borrow pits. If additional material is

taken from borrow pits adjacent to the roadway, a berm of

original unbroken ground, not less than 3 m (10 ft) wide, is

required between the outside toe of the embankment and the

edge of the borrow pits, with provisions for a side slope of

1.5h:1v to the bottom of the borrow pit. Where directed for

drainage or other requirements, the berm between the toe of

the embankment and the borrow-pit slope should be no less

than 12 m (40 ft) wide. Provisions are made for connecting

pit to pit with waterways, unless otherwise directed, and to

provide ample drainage and leave no stagnant pools. Unless

otherwise approved, the bottoms of pits near bridge and

culvert openings are not permitted to be excavated below the

culvert or bridge. The borrow pits should be left in a

reasonably smooth and even condition.

c. Control Techniques.&Many of the control

techniques discussed in preceding paragraphs are applicable

to highway and railroad embankments. Moisture contentdensity relationship of soils and related field control methods

are fundamental for any earthwork construction where

compaction of soil is required. However, the same degree of

control may not be practical nor required for highway and

railroad embankments.

Control requirements vary depending on standards adopted

by the various agencies involved with Reclamation in the

relocation agreement. The inspector should first become

familiar with the appropriate requirements and standards and

adapt the techniques discussed for embankment dam

embankments to the requirement. The principal differences

in control are:

1. Moisture, if required, for the most part will be added

to material on the fill. Usually, moisture content should

be as near as possible to the optimum required for

maximum compaction.

2. Density requirements are usually specified as

percentages of laboratory maximum dry density and vary

according to the maximum dry density of soil.

3. The frequency of testing required to maintain control

on these embankments is not standardized. For each fill

location, the quantity of water and the amount of rolling

required must be determined rapidly so the information

may be used when constructing the fill. Since

construction of a fill may be a relatively short operation,

moisture and rolling requirements must be established

quickly. The rapid method of construction control

(USBR 7240) can be used for compacted highway and

railroad embankments. 6

 Where compaction is required

by the specifications, one in-place density test should be

made for each 2,000 m3

 (2,000 yd3) of compacted fill.

6

 7240: Performing Rapid Method of Construction Control
EARTH MANUAL

294

4. Conformance with certain specifications provisions

can be determined by visual inspection, such as

preparation of foundation soils, and deposition of

material. Selection of borrow materials required in

embankment dam construction may not be required for

highway or railroad work.

5. Thickness of layers, whether they are to be

compacted by roller or equipment, is normally specified;

control of layer thickness is the inspector' s

responsibility. Where embankment is to be compacted

by equipment travel, distribution of travel over the

embankment should be directed to obtain the maximum

amount of compaction.

3-38. Miscellaneous Structures.&

a. General.&In addition to large earth structures such

as dams and embankments, many earthwork features relate

to smaller structures built by Reclamation. These structures

include:

 ̆ Pumping plants

 ̆ Powerplants

 ̆ Bridges

 ̆ Substations

 ̆ Warehouses

 ̆ Residences

various types of canal structures such as:

 ̆ Checks

 ̆ Drops

 ̆ Turnouts

 ̆ Siphons

 ̆ Pipelines

 ̆ Overchutes.

Although foundation loadings for most of these structures are

normally light, moderately heavy loadings on soils are not

uncommon for larger units. Even for small structures soft,

highly compressible, or expansive soils&at natural moisture

content or in a future wetted state&must be examined

carefully. Care must be exercised when compacting

embankment and compacting backfill about these smaller

structures.

b. Structure Foundations on Soil or Rock.&The

contractor is required to use methods of foundation soil

preparation, including moistening and tamping if necessary,

which will provide appropriate foundation soil conditions.

Excavation is made to lines and grades shown on drawings or

as directed when subsurface conditions become known.

Additional excavation is refilled and compacted, as specified.

Loosened or disturbed natural material must be either

compacted or removed and replaced with suitably compacted

material. When excavation for concrete structures is in rock,

rock should be excavated so there will be more than 150 mm

(6 in) between rock points and the bottom of the concrete

slab. This space is filled with compacted soil. For other

structures, concrete is often placed directly on rock which

has been previously cleaned and dampened. Large unit

loadings may be used in this case.

Construction of small miscellaneous structures usually

involves a variety of earthwork problems because of the

numerous structures involved, the extent of the work, and the

many different soils encountered in foundation soils and

backfill materials. For larger structures (i.e., powerplants

and pumping plants), where loadings are moderately high and

settlements must be small, explorations are normally

conducted before designs are prepared to determine

competency of foundation soils. Measures to improve the

competency of foundation soils, if needed, are usually known

ahead of time and are included in plans and specifications.

Often, it is impractical to perform adequate predesign

explorations, so provisions for drilling exploratory holes or

performing tests&after the excavation has been

completed&are contained in the specifications. Usually, it is

impractical to perform detailed investigations of foundation

soils for the numerous small structures built by Reclamation.

Regardless of the amount of prior exploration, the inspector' s

responsibility is to make sure that soil conditions, which can

be observed upon completion of excavation to grade, are

compatible with design assumptions. If any doubt exists

concerning adequacy of foundation soils, this fact should be

brought to the attention of the supervisor.

Several methods can be used to check properties of

foundation soils. When sands are involved, the field

penetration test, with split-tube sampler (USBR 7015),

provides a rapid method for determining the relative density

of soil. 7

 The relationship of blow counts to relative density

was shown on figure 1-15. Unless otherwise specified,

70 percent relative density of sands can normally be

considered adequate for all but very heavy loadings. For

very fine sands, 80 percent relative density is often used.

Gravelly soils containing at least 50 percent gravel and

graded up to coarse sizes can be considered to have adequate

shear strength and satisfactory consolidation properties for

most Reclamation structures if the in-place relative density is

60 percent or greater. In-place density tests (USBR 7205,

7

 7015: Performing Penetration Resistance Testing and Sampling of

Soil.
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

295

7206, 7215, 7220, 7221, or 7230)8 and the index unit weight

tests (USBR 5525 and 5530) can be used with USBR 7250 to

determine the relative density of sand, sand-gravel, and

gravel soils. 9

As presented on figure 1-16, the relative consistency of

saturated fine-grained soils can be estimated using data from

the standard penetration test (USBR 7015). 10

Cone penetration tests (USBR 7020 or 7021)11 and

pressuremeter tests (ASTM D 4719) [26] may be used to

evaluate the adequacy of foundation soils. Both tests may be

performed in cohesive or cohesionless soil deposits.

Hard, saturated fine-grained soils normally will support

moderately heavy to heavy loads. Very firm soils usually are

adequate for light loadings. When fine-grained cohesive

soils are not saturated, data from most in situ test methods

are misleading and should not be used for evaluating

foundation soils for hydraulic structures because properties

of the soils in a later saturated condition cannot be

determined. In-place density tests provide a good index as to

the supporting capacity of saturated or unsaturated

fine-grained soils.

Fat clays (CH), lean clays with liquid limits above

40 percent, or high plasticity clay shales should be checked

to determine whether they are sufficiently expansive to cause

undesirable uplift of a structure. This can be accomplished

by determining the gradation, plasticity index, and shrinkage

limit of the soil. Any such soils falling into the "low

expansion" grouping of table 1-2 are satisfactory.

When qualitative tests indicate doubtful support more detailed

testing is necessary. Usually, this is accomplished by

securing undisturbed soil samples and testing them in the

laboratory.

When bottom grade of a structure is known to be below the

water table, provisions are usually contained in the

specifications for dewatering foundation soils and unwatering

the excavation. When water is encountered, the inspector

must ensure that foundation soils are not disturbed by

removal of the water. This may be accomplished by

beginning the dewatering operations as soon as ground water

is encountered or at an elevation at least 1.5 m (5 ft) above

bottom grade elevation. During dewatering operations, the

water level should be maintained continuously at least

300 mm (12 in) below base grade until 48 hours after

sufficient concrete has been placed to overcome uplift

pressure. Dewatering may be performed by well points,

deep wells, trenches, or sumps, or by other methods which

will prevent upward movement of water through soils within

the area of the structure foundation.

After excavation has proceeded to grade, care should be

taken to ensure that foundation soils are not disturbed by

equipment working in the area. Excessive drying or wetting

may damage certain types of soils. Shales may require a

cover of pneumatically applied mortar, soil, or a thin cover

of concrete to prevent slaking; however, placement

immediately after final cleanup is usually sufficient.

When a structure is designed for placement on impervious

soils, the inspector should ascertain that the material is

adequately impervious and that strata or lenses of permeable

soil do not exist which might cause subsequent piping.

Cutoff walls should be constructed to the depth shown on the

drawings and into impermeable soils as required.

Construction of cutoff walls into soil must be such that piping

cannot occur around the walls. Normally, specifications

require either that concrete for transitions and cutoff walls be

placed against the sides of the excavation without use of

intervening forms or that compacted backfill of silty or

clayey soils be used between the concrete and natural ground

after the forms are removed.

When the foundation area consists of more than one type of

soil, care should be taken to prevent appreciable differential

settlements. Often, pockets of soft or loose materials must

be removed and be replaced with suitable compacted soil to

provide uniform bearing over the entire foundation area.

When a foundation area is partially on soil and partially on

rock, sometimes it is necessary to remove the soil to rock

and refill with lean concrete. At times, excavating additional

rock and replacing it with compacted soil is desirable. The

8

 7205: Determining Unit Weight of Soils In-Place by the Sand-Cone

Method.

7206: Determining Unit Weight of Soils In-Place by the Rubber

Balloon Method.

7215: Determining the Unit Weight of Soils In-Place by the Sleeve

Method.

7220: Determining Unit Weight of Soils In-Place by the Sand

Replacement Method in a Test Pit.

7221: Determining Unit Weight of Soils In-Place by the Water

Replacement Method in a Test Pit.

7230: Determining Unit Weight and Moisture Content of Soil InPlace & Nuclear Moisture-Density Gauge. 9

 5525: Determining the Minimum Index Unit Weight of

Cohesionless Soils.

5530: Determining the Maximum Index Unit Weight of Cohesionless

Soils.

7250: Determination of Percent Relative Density.

10 7015: Performing Penetration Resistance Testing and Sampling of

Soil. 11 7020: Performing Cone Penetration Testing of Soils&Mechanical

Method.

7221: Determining Unit Weight of Soils In-Place by the Water

Replacement Method in a Test Pit.
EARTH MANUAL

296

type of treatment depends upon the type of structure,

structural loadings, and strength and compressibility of the

soil.

c. Pile and Drilled Shaft Foundations.&When piles

are required to provide desired bearing capacity or to

minimize settlement, specifications contain requirements as

to the type of piles, the cross-sectional area, and, in some

cases, the length of the pile. Frequently, minimum depth of

penetration is specified. A pile must never have a minimum

penetration less than that shown on the drawings. Piles are

of such length that the top of the pile will be at the specified

elevation even after any damaged or battered portion of the

top of the pile is cut off. Piles are required to be driven

accurately to required lines and depths with either drop

(gravity) hammers&single acting or double acting diesel

hammers&or vibratory or hydraulic drivers. To reach the

minimum penetration specified on the drawings, preboring or

jetting prior to driving may be required. A usual

requirement is that the number of jets and the volume of

water, with adequate pressure, be available to freely erode

material adjacent to the pile. When the minimum penetration

called for is reached, the jets shall be removed and the pile

finally set to grade using normal driving techniques. When

holes are prebored, the diameter of the prebore holes shall be

slightly smaller than the diameter of the pile, and the depth

of the holes shall be such that the piles will reach the

specified minimum penetration.

The pile driving specifications contain detailed provisions

for:

 ̆ Shoes

 ̆ Cutoff

 ̆ Preboring or jetting

 ̆ Cutting

 ̆ Splicing

 ̆ Pile materials

 ̆ Preservative materials

 ̆ Preservative treatment

 ̆ Miscellaneous accessories

The inspector is required to ensure that all piles are located

properly and are driven to specified lines, grades, and

tolerances. The inspector must ensure that piles are not

damaged during driving and that required penetration is

obtained. Damaged piles or piles not driven to correct line

and grade are ordered removed. When piles are in place in

freezing weather, the top elevation should be checked before

placing of concrete. If heaving has occurred, the piles

should be redriven to grade.

Sometimes, static pile load tests are specified for determining

bearing capacity or tensile capacity of single piles or pile

groups. When pile load tests are required and, unless

otherwise specified, they are in accordance with:

 ̆ ASTM D 1143: Piles Under Static Axial

Compressive Load [27] (or USBR 7400: Testing

Foundation Members Under Static Tensile Load)12

 ̆ ASTM D 3689: Individual Piles Under Static

Compressive Load [28]

 ̆ ASTM D 3966: Piles Under Lateral Loads [29]

In special cases, other tests may be required; special

instruction will be provided for those tests.

When pile load tests are performed, the inspector is

responsible to verify that:

 ̆ Test piles are placed to specified line, grade, and

length

 ̆ Driving records are secured

 ̆ Test loadings are applied in proper manner, amount,

sequence, and period of time

 ̆ Data are obtained and recorded as required

Static load capacity of individual piles also may be

determined using dynamic testing methods. When using

dynamic test methods, transducers are mounted to the top of

a pile to obtain force-time or velocity-time data from

individual hammer blows. The data can be analyzed using

wave equation theory to determine:

 ̆ Pile integrity

 ̆ Static load capacity (bearing capacity)

 ̆ Hammer performance

 ̆ Stresses in the pile during driving

Dynamic testing should be performed in accordance with

ASTM D 4945: High-Strain Dynamic Testing of Piles [30].

Drilled shaft foundations (also called caisson, drilled pier,

drilled caisson, or bored pile foundations) sometimes are

used in lieu of pile foundations when it is necessary to

transfer heavy foundation loads to deep, competent bearing

strata. Drilled shaft foundations may be of constant

diameter, tapered, or belled-out at the bottom. Belled-out

shafts (piles) have been used in expansive clay as anchors to

prevent structure uplift. Usually, shafts are drilled with

large auger boring equipment, belled if needed, and cleaned;

12 7400: Testing Foundation Members Under Static Axial Tensile

Load.
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

297

then, reinforcing steel and concrete are placed as specified.

The inspector is responsible to ensure that:

 ̆ All loose soil is removed from the bottom of the shaft

 ̆ Soil at the bottom is competent for design loadings

 ̆ The bells, if required, are properly excavated in

undisturbed material

Shafts may be cased or uncased&depending on soil and

ground-water conditions. If water is encountered, the hole

must be dewatered by approved methods until some specified

time after the concrete is placed (usually 6 hours), unless

tremie concrete is allowed in the specifications.

For more information on pile and drilled shaft foundations,

see references [31, 32, and 33].

d. Backfill.&Backfill is specified in specifications

variously as:

 ̆ Backfill about structures may be specified simply as

backfill for which compaction is not required, or as

compacted backfill for which the compacted dry

density is specified.

 ̆ Backfill may be further classified on the basis of

material required, for example, "cohesionless freedraining materials of high permeability, commonly

called pervious material," or "clayey and silty

materials of low permeability, commonly called

impervious material."

 ̆ Compacted backfill is normally specified if backfill

under structures is required.

 ̆ Compacted backfill may be specified as compacted

clayey or silty materials for which compaction is done

by tamping rollers, power tampers, or other similar

suitable equipment.

 ̆ Compacted backfill may be specified as compacted

cohesionless free-draining materials for which

compaction is accomplished by thorough wetting

accompanied by operation of surface vibrator, internal

vibrator, tractor, or other similar suitable equipment.

Backfill, or compacted backfill is placed as shown on the

drawings or where prescribed by the contracting officer.

Type of material used, amount, and manner of depositing

backfill are subject to approval of the contracting officer.

Insofar as possible, backfill materials are normally secured

from required excavation. When suitable materials required

for a specific structure are not available from required

excavation, the materials are secured from approved borrow

sources. Distribution of material must be uniform and such

that compacted backfill is free from lenses, pockets, streaks,

or other imperfections.

When silty and clayey soils are placed as compacted backfill,

required dry density of soil is 95 percent of laboratory

maximum dry density (USBR 5500) unless otherwise

specified. 13 Prior to compaction, these soils normally are

required to have a uniform moisture content. When

cohesionless, free-draining soils are placed as compacted

backfill, required dry density of soil is that equivalent to 70-

percent relative density (USBR 7250) unless otherwise

specified. 14 Higher density requirements may be specified

for fine sands for large structure loadings, when structure

vibrations are severe, or when only very small settlements

can be tolerated. After compaction, the depth of layers,

unless otherwise specified, is 150 mm (6 in) when rollers are

used, or not more than 300 mm (12 in) when vibrators or

surface tractors are used. A normal requirement is that these

fine sands be thoroughly wetted during compaction.

To provide adequate protection for compacted backfill about

structures where backfill adjoins embankment, specifications

often provide that the contracting officer can direct the

contractor to place a sufficient amount of embankment

material over the compacted backfill within a specified length

of time (often 72 hours) after compaction of backfill has been

completed. This provision is included so the backfill will not

dry and shrink and cause cracking and pulling away from the

structure.

Sand and gravel backfill material is often specified for

placement:

 ̆ Under and about structures

 ̆ Under canal linings

 ̆ For filters

 ̆ At bridge approaches

 ̆ At weep holes, or against retaining walls

 ̆ For other purposes

Various gradations of material may be specified for different

structural purposes. Laboratory tests should be made at

frequent intervals to ensure that materials meet specified

gradation limits. Unless otherwise specified, maximum

particle size for backfill materials is 75 mm (3 in); and, the

amount of material finer than the 75 μm (No. 200) sieve size

for sand-gravel backfill is limited to 5 percent or less.

Generally, control techniques given for compacted earth

embankments and compacted linings apply to backfill.

Control of compacted backfill consists of:

13 5500: Performing Laboratory Compaction of Soils&5.5-lbm

Rammer and 18-in Drop. 14 7250: Determination of Percent Relative Density.
EARTH MANUAL

298

 ̆ Inspecting materials

 ̆ Checking amount and uniformity of soil moisture

 ̆ Maintaining thickness of layers being placed

 ̆ Determining the percentage of laboratory maximum

dry density or relative density obtained by compacting

operations

Also, determination should confirm that the soils are fully

compacted to specified lines and grades.

e. Filters.&Protective filters for canals and

miscellaneous structures consist of one or more layers of

free-draining soil placed on less pervious soil. The soil to be

protected by the filter is commonly referred to as the base

soil or the base material. The purposes of a protective filter

are to:

 ̆ Safely carry off seepage from the base soil

 ̆ Prevent erosion or piping of the base soil

 ̆ Prevent damage to overlying structures from uplift

pressure

The base soil can be protected by filter materials that have a

certain range of gradation. Gradation of the filter material

bears a definite relationship to the gradation of the base

material. Filters may consist of a single layer or several

layers, each with a different gradation. Multiple layer filters

are known as zoned filters.

Material selected for the protective filter must satisfy four

main requirements:

1. Filter material should be much more pervious than

base material. This requirement prevents excess

hydraulic pressures from building up in either the filter

material or the base material.

2. Voiding the compacted filter material must be small

enough to prevent base material from penetrating the

filter. Penetration of the filter can cause the filter to clog

with base material or piping of the base soil through the

filter. Either condition can result in failure of the filter

system.

3. The filter must be thick enough to provide good

distribution of particle sizes throughout the filter to

provide adequate hydraulic capacity for the volume of

water flowing out of the base soil.

4. Filter material must be prevented from moving into

drainage pipes by providing sufficiently small slot

openings or perforations, or by additional coarser filter

zones if necessary.

Filter design based on gradation criteria is generally credited

to G.E. Bertram, with the assistance of Karl Terzaghi and

Arthur Casagrande [34]. Over the years, studies by the U.S.

Army Corps of Engineers [35], Reclamation [36, 37], and

the Natural Resources Conservation Service [38] have

produced various, and sometimes conflicting, filter criteria.

Stability criteria are the oldest criteria and are the only

criteria having successfully been demonstrated in laboratory

studies; they are the only criteria that seem to be universally

accepted. Stability criteria (also referred to as the stability

ratio) state that the ratio of the D15 size of the filter soil to the

D85 of the base soil must be equal to or less than 5. The

stability ratio has been shown to be conservative but effective

in preventing penetration of the base soil into or through the

filter.

Permeability of filter material should be at least 25 times

larger than permeability of the base material. Generally,

permeability criteria are satisfied if the D15 size of the filter

material is equal to or greater than 5 times the D15 size of the

base material.

In addition to stability and permeability criteria, filters should

satisfy the following requirements: ([14], ch. 5; and [35,

38]).

1. Filter material should be clean, cohesionless sands or

gravels with Cu (coefficient of uniformity) between 1.5

and 8. Filter material should pass the 37.5-mm

(1-1/2 in) sieve to minimize particle segregation and

bridging during placement. Smaller maximum particle

sizes may be specified. Filters must have less than 5

percent minus 75 μm (No. 200) sieve size material to

prevent clogging caused from excessive movement of

fines in the filter and drainage pipes and to maximize

permeability of the filter.

2. Filter material adjacent to drainage pipes should have

sufficient coarse sizes to prevent movement of filter

material into the drainage pipes. The maximum size of

perforations or joint openings of drainage pipe is

selected as one-half of the D85 grain size of the filter

material.

The specifications will normally describe the following

requirements for filter construction:

1. Before filter placement, the base soil should be firm

and, if necessary, be lightly tamped or rolled.

2. Clean filter material should be protected from

contamination during and after placement; the placement

method should minimize segregation in the filter.

3. Filters are compacted to 70-percent relative density

unless otherwise specified, in a manner similar to freedraining sand-gravel backfill to prevent settlement.
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

299

4. Filter layers are often specified at a 150-mm (6-in)

minimum thickness. However, for extreme conditions

such as high heads, variations in base material, or filter

gradations that are near the extreme coarse limit, a

minimum thickness of 200 mm (8 in) may be specified.

For zoned or graded filters these minimum thicknesses

may be specified and are maintained for each layer.

5. Where drainage pipe is used in a filter system,

hydraulic capacity of the pipe should be sufficient to

collect the expected volume of seepage water and to

convey it to a place for discharge.

6. While drainage pipe is being laid, the openings are

often protected from inflow of fines from the filter

material.

Figure 3-41 shows an example using filter criteria. For

additional information on filter design, see references [38,

39]. Often ASTM C-33 concrete sand can serve as a

protective filter material for many materials.

Recently, geosynthetic materials (geotextiles, geonets, and

geocomposites) have gained wide acceptance for use as filters

and drains in civil engineering works. These specialized

materials have been used successfully in:

 ̆ Landfill liner systems

 ̆ Highway edge drains

 ̆ Retaining walls and basement walls drains

 ̆ Highway subgrade drains

 ̆ Strip or wick drains

Design methods for these materials, while similar to the

design of soil filters, require specialized testing to determine

required properties of the geosynthetics. Design methods

and applications for these special materials is discussed in

reference [40].

H. Stabilized Soils

3-39. General.&Soil stabilization is the chemical or

mechanical treatment of soil to improve its engineering

properties. Chemically stabilized soils consist of soil and a

small amount of additive such as cement, fly-ash, or lime.

The additive is mixed with the soil, and the mixture is used

in compacted fills, linings, or blankets. Quality and

uniformity of the admixture and the uniformity of moisture

are closely controlled to produce a high quality end product.

Therefore, processing equipment and procedures are

specified to ensure that the relatively small amount of

additive is uniformly distributed throughout the soil mixture

before placement and compaction. Uniformity of soil in the

mixture is a major factor in controlling desired uniformity of

the final product; and soil gradation, plasticity, and moisture

content should be controlled prior to mixing with the

additive&or prior to adding the stabilizer for in-place mixing.

A mixing plant must be calibrated over the range of soil

gradation stated in the specifications. Adjustments to the

mixing plant should then be made during construction to

accommodate variation in soil gradation or for other variable

conditions. These adjustments are based on mixing plant

calibrations obtained before and during construction.

Sometimes, soils are stabilized to deeper depths by grouting

or by injection methods to solve particular foundation

problems (see sec. 3-19). These methods for stabilization

require specialized knowledge and understanding of the

materials being used, and quality control procedures are

specifically developed for the particular situation.

3-40. Compacted Soil-Cement.&

a. Design Considerations.&Compacted soil-cement

has been used as upstream slope protection for embankment

dams and as blankets, linings, or other applications. Soilcement used as upstream slope protection is placed in

successive horizontal layers ranging from 150 to 300 mm (6

to 12 in) in compacted thickness to protect the slope from

wave action. The layers are placed successively up the

slope, and the outer edges form a stairstep pattern. When

soil-cement is placed as a blanket or lining it is usually

placed in layers up to 600 mm (2 ft) thick with the layers

parallel to the slope. Although roads are a minor part of

Reclamation work, compacted soil-cement has been used

extensively for construction of road bases by others.

Figures 3-42 and 3-43 show soil-cement facings constructed

on the upstream slope of two Reclamation structures.

To satisfy design requirements for slope protection, a layer

must be:

1. Formed into a homogeneous, dense, permanently

cemented mass that fulfills the requirements for

compressive strength

2. In intimate contact with earth slopes, abutments, or

concrete structures
EARTH MANUAL

300

Figure 3-41.—Filter gradations.

3. Durable and resistant to "wetting and drying" and

"freezing and thawing" action of water

4. Stable with respect to the structure and of sufficient

thickness (mass) to resist displacement and uplift

Performance of soil-cement facings on Reclamation dams has

generally been excellent. However, inspections of these

facings have revealed that the bond between lifts is a weak

point in the facing. Test results on cores taken from these

faces show that the bond is much weaker than the remainder

of the soil-cement [41, 42]. Since the layers are not well

bonded, they perform as a series of nearly horizontal slabs on

the slope of a dam. Each slab is offset from the previous one

by a distance equal to the layer thickness multiplied by the

slope of the dam. If the layers were well bonded, the entire

facing would act as a massive unit instead of as individual

layers, and damage by wave action would be greatly

minimized.

Several studies have been performed to identify methods for

enhancing bond between layers. Currently, the most

promising method investigated is to apply a water-cement

slurry to a layer just before placing the overlying layer. This

technique was used at Davis Creek Dam in Nebraska to
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

301

Figure 3-42.—Soil-cement facing at Lubbock Regulating Reservoir in Texas.

improve bonding between layers and to improve overall

durability of the facing for an elevation of about 6 m (20 ft)

at normal reservoir operating level.

b. Construction Provisions.&The specifications

describe the type and amount of cement, the quality and

amount of water, and the borrow area for soil or aggregate.

The permissible range of soil and aggregate gradation also is

specified. If investigations show the deposit is variable,

selective excavation and processing may be required to

produce uniformity. Oversize particles and other

objectionable materials must be removed.

A stationary mixing plant is usually required. Either a batch

type or a continuous-feed pugmill type plant is acceptable.

Control over mixing time; positive interlocking of cement

and soil flow; and controls for accurately proportioning soil,

cement, and water&all from appropriate storage&should be

incorporated into the plant design. A mixing plant used at

Lubbock Regulating Reservoir in west Texas is shown on

figure 3-44.

Trucks for transporting the soil-cement mixture should have

tight, clean, smooth beds and protective covers. The soilcement spreader used for laying the soil-cement must

produce a smooth uniform loose layer of required width and

thickness. Usually, layers are placed horizontally; however,

a slope toward the outer edge as steep as 8h:1v is sometimes

permitted to increase working width. The maximum time for

hauling and spreading the soil-cement after mixing is usually

specified as 30 minutes. The tractor and spreader box used

for placing soil-cement on Merritt Dam and Reservoir in

Nebraska is shown on figure 3-45.

Generally, compaction must be completed within 60 minutes

after spreading with no more than 30 minutes between

operations. Compaction is accomplished by several passes

of a sheepsfoot tamping roller, followed by several passes of

a pneumatic-tire roller, as shown on figure 3-46. The

minimum number of passes by each roller should be

determined by constructing a test section. The rollers should

have provisions for ballast loading so the masses can be

adjusted to provide optimum compaction. Vibratory, smooth
EARTH MANUAL

302

Figure 3-43.—Soil-cement facing at Merritt Dam in Nebraska.

steel drum rollers have been used to compact coarse grained

soil-cement. A combination of vibratory and static mode

may be used. The roller mass and the frequency and

amplitude of vibration should be set for optimum compaction

without damage to the soil-cement and to minimize localized

shear failure in the upper part of a layer. A test section

should always be constructed to determine: optimum

equipment usage, roller mass, and number of passes&and

vibratory characteristics if a vibratory roller is used. Rollers

may be towed or self-propelled. After compaction, the

compacted layer is cured by keeping the exposed surfaces

continually moist using a fog spray until the overlying or

adjacent layer is placed, or for a minimum of 7 days. A

blanket of moist earth may be used for permanently exposed

surfaces. The surface of a completed layer may require

brushing to remove soil or other debris just before placing an

overlying layer, as shown on figure 3-47.

c. Control Techniques.&Compacted soil-cement is

similar to compacted earthwork in that careful observations

and additional control tests are required during the early

stages to check planned control against results obtained under

field conditions. These observations and tests are used to

establish placing conditions and to develop procedures for

use in the remaining construction. Control should begin

during excavation and stockpiling of the soil to ensure that

the material is within gradation requirements and has a

uniform moisture content. Gradation and moisture content

are controlled by:

 ̆ Directing the excavation

 ̆ Mixing the stockpile by spreading and cross-dozing

 ̆ Sloping the stockpile surfaces to provide runoff

without water catchments

 ̆ Sampling and testing during stockpiling

After the mixing plant is set up, the cement, soil, and water

feeds must be calibrated individually to establish curves (or

tables) of equipment settings versus quantity produced. The

plant must be calibrated over the full range of anticipated

production rates. A cement vane feeder and soil feed belt to

a pugmill are shown on figure 3-48. Calibration is

accomplished by timing and weighing quantities of moist

soil, cement, and water to check feed and meter settings. To

facilitate computation of dry soil production, moisture

content of the wet soil should be determined at the plant by
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

303

Figure 3-44.—Soil stockpile and pugmill for mixing soil-cement at Lubbock Regulating Reservoir in Texas.

a quick method, such as the calcium carbide reaction device

(USBR 5310), a microwave oven (USBR 5315), or the

Moisture Teller device (USBR 5305). 1

 The cement feed is

perhaps the most crucial calibration because of variation in

the amount of cement can critically affect the properties of

soil-cement. The cement feed is calibrated over the range of

required cement content by varying the feeder speed. The

cement feed is usually quite consistent because cement is a

fairly uniform product and is fed under reasonably uniform

conditions in a well-designed plant. Cement feed calibration

allows accurate adjustment if soil feed rates change during

progress of the job. Plant performance and production is

checked under full load by:

 ̆ Timing and weighing truckloads of the soil-cement

mixture

 ̆ Checking mixing time

 ̆ Inspecting the mixture for:

- Uniformity in texture

- Moisture

- Distribution of cement

The soil and soil-cement mixture is sampled to determine:

 ̆ Cement content

 ̆ Moisture content by both quick and ovendry methods

 ̆ Occurrence of "clay balls" (rounded balls of clayey

fines and sand which do not break down during

ordinary processing)

During construction, the inspector should check plant

operation periodically. Inspection frequency will depend on

performance of the plant and uniformity of soil gradation and

moisture content. The soil feed rate should be checked at the

beginning of each shift by timing and weighing a truckload

of moist soil. By using a quick method to determine

moisture content, the feed rate of dry soil can be computed,

and the proper cement and water feed rates can be set. At

regular intervals, the moisture content of the soil and soilcement mixture should be determined by a quick method to

1

 5310: Determining Moisture Content of Soils Using the Calcium

Carbide Reaction Device.

5315: Determining Moisture Content of Soils by the Microwave

Oven Method.

5305: Determining Moisture Content of Soils Using the Moisture

Teller Device.
EARTH MANUAL

304

Figure 3-45.—Soil-cement placement at Merritt Dam in Nebraska.

provide a basis for making adjustments in the water feed if

necessary. Also, the inspector does a check calibration each

time a record control test is performed by timing the

production and weighing a truckload of soil-cement. Based

on water content and cement feed rate, the soil feed rate can

be determined. The soil and soil-cement are sampled for

moisture tests at the plant and for record tests in the

laboratory.

The placement inspector should observe placing and

compaction procedures and should verify that loose lift

thickness, texture, and surface are uniform and that the lift

is to specified dimensions.

Compaction begins with the roller starting at the outer edge.

The number of passes and adequacy of overlap should be

checked. When using a sheepsfoot roller, each pass over the

entire width of the lift should be completed before the next

pass begins, as the tamping feet tend to follow previous

tracks if successive passes are made without overlap.

Because of the sandy material, the sheepsfoot roller usually

does not "walk out" completely but should begin to "walk

out" on the last passes. Each layer is completed by

compaction with a pneumatic-tire roller. This is in contrast

to normal earthwork where successive layers are compacted

together with a sheepsfoot roller. With the time limits used

in soil-cement construction, it is usually not feasible to place

successive layers quickly enough to compact them together;

hence, each lift must be compacted individually.

The pneumatic-tire roller also starts compaction at the outer

edge of the lift to minimize the amount of lateral spreading

of the soil-cement. Smooth, even surfaces after compaction

are desired. Rutting usually indicates a high placement water

content. Thickness and width of the completed compacted

lift should be checked. The placement inspector should be

sure that the surface of the compacted layer is kept

continuously moist until the overlying layer is placed, or for

a minimum of 7 days. If required, the surface should be

thoroughly cleaned by brooming (brushing) just before

placing an overlying layer (fig. 3-47).

Access ramps for trucks hauling soil-cement are built of soil

on the soil-cement facing; these should also be checked to

verify that they satisfy specified thickness requirements

[usually 600 mm (2 ft)]. Ramps are constructed to

adequately protect the edge of the top layers on which soilcement is being placed. Inadequate ramps will result in
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

305

Figure 3-46.—Compaction of soil-cement at Lubbock Regulating Reservoir in Texas.

damage to the outside edges of soil-cement layers and

decrease durability of the finished product.

d. Control Testing.&During construction, control

testing is required for every 500 m3

 (500 yd3) of soil-cement

placed, or a minimum of one test per shift. The control test

consists of timing a sample through the process to ensure that

specified time constraints are met. Times recorded are

(1) when the truck leaves the plant, (2) when the load is

spread, (3) when compaction is completed, and (4) when the

control test is taken in the compacted material. Procedures

for performing construction control of soil-cement are

outlined in USBR 5830.

Control testing begins by timing the production of a truckload

of soil-cement and obtaining a representative sample of soil

from the soil feed. The mass of the timed truckload is

determined, and a representative sample of soil-cement is

obtained for laboratory testing. When the load is spread, the

approximate center of the load is marked by the placement

inspector. Moisture contents of the soil and soil-cement are

determined by a quick method at the time of sampling, and

the remainder of the samples are used for laboratory tests.

For the soil, the percentage of fines is determined, and the

moisture content is obtained by the standard ovendrying

method. The cement content of the soil can be determined

by chemical titration. If the untreated soil contains a

significant amount of calcium, a chemical analysis of the soil

is performed. The presence of calcium should have been

determined when the soil was being stockpiled. A complete

gradation and specific gravity should be determined on

specimens from every fourth control test.

For the soil-cement, the percentage of "clay balls" is

determined, and the percentage of cement is determined by

either the heat of neutralization method or the chemical

titration method. A three-point compaction test is performed

using the rapid method of construction control. The

compaction test should be performed at the same time that

material (from the sampled truck load) is being compacted.

This is necessary to allow for time effects on compaction

properties of soil-cement caused by hydration of cement. 
EARTH MANUAL

306

Figure 3-47.—Power brooming of surface prior to placement of next lift at Lubbock Regulating Reservoir in Texas.

The remainder of the soil-cement sample is used to prepare

three or four compression test specimens to be tested at ages

7, 28, and 90 days. One 7-day and two 28-day specimens

should be formed for each control test with an additional

specimen for a 90-day test for every fourth control test.

Specimens tested at 90-days are for design verification only

and not for construction control. Specimens are placed at the

density determined from the field density test of the

compacted soil-cement layer. These specimens should be

formed as soon as possible after the field density has been

determined. Procedures for preparing specimens for

compressive strength testing are discussed in USBR 5806 and

testing of soil-cement cylinders is described in USBR 5810.

A field density test is performed at the point marked by the

placement inspector when the timed load was spread. This

test should be performed as soon as compaction is complete.

Care should be taken so the test is not performed where

roller overlap has occurred. When the test hole is complete,

but before determining the volume, the depth of the lift is

measured and recorded.

Control testing includes obtaining record cores from the

compacted soil-cement at least 28, 90, and 360 days after

completion. One hole should be drilled for each 5,000 m3

(5,000 yd3) placed. Locations of core holes should be spaced

to be representative of the area covered, with some cores

near abutments or structures. In drilling, care should be

exercised to obtain a continuous core; comments on bond

strength should be included with other information

accompanying the cores. The core holes should be carefully

backfilled with cement grout and a reinforcing bar placed

flush with the surface and located for future reference.

Record cross sections of the compacted soil-cement are

obtained at locations where 28-day core samples are taken.

The compressive strength of a section of core from each of

the holes should be determined in the field laboratory; this

strength is compared to those of the record construction

control cylinders representative of the immediate vicinity.

The remainder of the cores should be sent to the laboratory

for durability, direct shear, and compression tests. A

summary of compressive strength and age of record core,

and compressive strength of specimens of material in the

immediate vicinity, should accompany the cores. Procedures

for performing record coring and cross sectioning of

compacted soil-cement are detailed in USBR 5835.

3-41. Compacted Soil-Lime.&

a. General.&Use of lime as a soil additive is the oldest

known method of chemical stabilization; it was used by the

Romans to construct the Appian Way. Soil-lime is a mixture

of soil (usually clay), lime, and water which is compacted to

form a dense mass. Experience has shown that mixtures of

most clay soils, either quick or hydrated lime, and water will
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

307

Figure 3-48.—Cement vane feeder and soil feed belt to pugmill at Cheney Dam in Kansas.

form cementitious products in a fairly short period of time.

Reclamation applications for water resources work have been

limited to use of lime to stabilize expansive clay soils and

dispersive clay soils.

b. Adding Lime to Highly Plastic Clay Soils.&Adding

lime to highly plastic clay soils produces several effects on

physical properties:

1. The liquid limit decreases, and the plastic limit

increases, radically decreasing the plasticity index

(sometimes, by a factor of 4 or more)

2. The finer clay-size particles agglomerate to form

larger particles, which makes the soil more friable and

easier to work. By absorbing water, lime also assists in

breaking up clay clods during mixing.

3. Lime dries the soil by absorbing water to hydrate the

lime and makes wet soils easier to handle and compact.

4. Unconfined compressive strength increases many

fold.

Reclamation' s Friant-Kern Canal, California, was

constructed during 1945-51; about 87 km (54 mi) of the canal

traverse an area of expansive clay. Of these 87 km, 37 km

(23 mi) are earth lined, and the remaining 50 km (31 mi) are

concrete lined. After 3 years of operation, portions of the

canal traversing expansive clay soils began cracking,

sloughing, and sliding with failures occurring in both the

concrete-lined and earth-lined sections. Because these

conditions caused continuing, expensive maintenance

problems, in 1970, rehabilitation began for the worst failed

areas. Lime stabilization was selected as the most effective

method of treatment [43].

Riprap that had been dumped into slide areas was removed.

Then, all material to be stabilized with lime and recompacted

was removed by a benching operation. A series of long

sloping benches or ramps were cut from the top of the bank

down to the canal bottom, with the cut extending far enough

into the slope to remove the entire depth of required

excavation material. Two-percent quicklime was spread over

the bench surface, and 0.3 m (1 ft) of material from the

bench was mixed with the quicklime, and the lime-clay

mixture was pushed into the canal bottom. The material was

spread on the canal bottom and an additional 2 percent lime

was added. Water was added to at least 2 percentage points

above optimum moisture, and about 0.3 m depth of material

was mixed with dozers and graders. After about 2 m (6.6 ft)
EARTH MANUAL

308

of material had been mixed and cured for 24 hours, dozers

began spreading the material on the slopes, which were then

compacted with a sheepsfoot roller moving up and down the

slope. The side slopes were constructed in three compacted

lifts for a 1.1 m (3.6 ft) compacted depth normal to the

slope.

In subsequent rehabilitation work, the lime-treated soil was

placed and compacted in successive horizontal layers stepped

up the slope in the same manner in which soil-cement is

placed on the face of an earth embankment. This placement

method was found much more desirable than placing material

parallel to the slope. Placing and compaction were much

more efficient, and the finished product was of higher

quality.

The amount of lime used was controlled by periodically

placing a canvas on the ground where lime was to be spread,

and after spreading, mass of lime was determined for a given

area.

Four-percent lime by dry mass of soil was used during

rehabilitation of Friant-Kern Canal; compressive strength

increased to 20 times that of untreated soil. The

rehabilitation has proved durable after about 20 years of

additional service.

c. Adding Lime to Dispersive Clay Soils.&Dispersive

clay soils are those that erode in slow-moving or even quiet

water by individual colloidal clay particles going into

suspension and then being carried away by the flowing

water. A concentrated leakage channel (crack) must be

present for erosion to initiate in dispersive clay. This

mechanism is totally different than that for piping where

erosion begins at the discharge end of a leak and progresses

upstream through the structure until it reaches the water

source.

The design lime content for controlling dispersive clay soils

is generally defined as the minimum lime content required to

make the soil nondispersive. In addition, it may be desirable

to increase the shrinkage limit to near optimum water content

to prevent cracking from drying when using lime-treated soil

in surface layers. In all known cases investigated to date,

dispersive clay soils were made nondispersive by addition of

1 to 4 percent lime by dry mass of soil. However, in

construction specifications, the design lime content is often

increased 0.5 to 1.0 percent to account for losses, uneven

distribution, incomplete mixing, etc.

Dispersive clay soils were identified throughout the borrow

and foundation areas during investigations for McGee Creek

Dam, Oklahoma; it was determined to be practical to

stabilize these soils with lime during dam construction. Since

dispersive clay soils were not concentrated in specific areas,

lime treatment was considered more economical than

attempting to identify the randomly occurring dispersive

clays and selectively wasting them. Treating these clay soils

with lime rendered them nondispersive and allowed their use

in constructing the embankment-foundation contacts as

erosion resistant material on the downstream slope of the

embankments, and for placement as specially compacted

backfill in areas of high piping potential such as along

conduits through the embankment. Material was used

directly from the borrow areas to construct the remainder of

the dam and dike embankments. Specially designed filters

were used to guard against any possible erosion of dispersive

clay soils in untreated areas. Another benefit of using limetreated soil was the improved workability of some of the

highly plastic clay soil encountered.

d. Construction Procedures for Lime.&Treated

Dispersive Clay Soils.&The following general procedures

have proved satisfactory for handling, mixing, and placing

lime-treated soil.

Soil to be lime treated is pulverized in a high speed rotary

mixer or with a disk harrow prior to applying lime, and the

moisture content is brought to within 2 percent of optimum.

Lime is uniformly spread on the pulverized soil to the

specified percent lime by dry mass of soil. Lime is mixed

with the soil using a rotary mixer, and additional water is

added as necessary to again bring the mixture to within

2 percent of optimum (or other specified value). When

mixing is completed, the soil-lime mixture is cured for at

least 96 hours before placing and compacting. Exposed

surfaces of the mixture are either lightly rolled to prevent

moisture loss or the mixed material is stockpiled and the

surface sealed.

Each section of the foundation is carefully prepared

coincident with final mixing and pulverization of the limetreated material. The soil-lime is mixed until 100 percent

passes the 25 mm sieve and 60 percent passes the 4.75-mm

sieve (1 in and No. 4). Immediately after final mixing, the

lime-treated earthfill is placed and compacted in horizontal

lifts of no more than 150 mm (6 in) after compaction. The

material is compacted to no less than 95-percent laboratory

maximum dry density, using a tamping roller followed by a

pneumatic-tire roller. The top of each compacted lift is

scarified or disked before the next lift is placed [44].

The following items should be monitored to ensure high

quality earthwork construction control:
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

309

1. Soil pulverization (gradation)

2. Lime content

3. Soil dispersivity (before and after lime treatment)

4. Compacted density

5. Moisture content of both soil and soil-lime mixture

If embankment materials are placed on the compacted limetreated earthfill within 36 hours, special curing provisions

are not required. Otherwise, the exposed surface of the 

lime-treated earthfill is compacted with a pneumatic-tire

roller to seal the surface, and it is sprinkled with water for

7 days or until embankment material is placed.

Construction control testing is the same as that for other

earthwork.
EARTH MANUAL

310

BIBLIOGRAPHY

[1] Bureau of Reclamation, Embankment Dam Instrumentation Manual, 250 pp., Denver, Colorado, January 1987.

[2] National Research Council, Liquefaction of Soils During

Earthquakes, Committee on Earthquake Engineering,

Commission on Engineering and Technical Systems, National

Academy Press, Washington, DC, 1985.

[3] Jansen, R.E., Dams and Public Safety, Water Resources

Technical Publication, U.S. Department of the Interior,

Bureau of Reclamation, U.S. Government Printing Office,

pp. 106-108, 1983.

[4] American Society for Testing and Materials, D5519-94:

Standard Test Method for Particle Size Analysis of Natural

and Manmade Riprap Materials, Annual Book of ASTM

Standards, vol. 04-09, Philadelphia, Pennsylvania.

[5] Jones, C.W., Long-Term Changes in the Properties of

Soil Linings for Canal Seepage Control, Bureau of

Reclamation Report No. REC-ERC-87-1, Denver CO, July

1987.

[6] American Society of Civil Engineers, Soil Improvement,

History, Capabilities, and Outlook, Geotechnical

Engineering Division, February 1978.

[7] Mitchell, J.K., Soil Improvement - State of The Art

Report, Proceedings of the International Society for Soil

Mechanics and Foundation Engineering, 1985.

[8] Anderson, Loren, Editor, Geotechnical Practice in Dam

Rehabilitation, Special Publication No 35., American Society

of Civil Engineers, New York, 1993.

[9] American Society for Testing and Materials, ASTM

Special Technical Publication STP 1129, Slurry Walls,

Design, Construction, and Quality Control, Philadelphia,

Pennsylvania, 1992.

[10] Farrar, J.A., Heat of Neutralization Method for

Determining Cement Content in Soilcrete&Jackson Lake Dam

Modification, Report No. R-89-15, Bureau of Reclamation,

Denver, Colorado, December 1989.

[11] Dise, K., M. Stevens, and L. Von Thun, Dynamic

Compaction to Remediate Liquefiable Embankment

Foundation Soils, Insitu Deep Soil Improvement,

Geotechnical Special Publication No. 45, American Society

of Civil Engineers, New York, 1994.

[12] Solymar, Z.V., Earth Foundation Treatment at Jebba

Dam Site, Journal of Geotechnical Engineering, American

Society of Civil Engineers, vol. 110, No. 10, pp. 1415-1430,

Oct 1984.

[13] "Grouting, Soil Improvement, and Geosynthetics,"

Borden, Holtz, and Juran Editors, Geotechnical Special

Publication No. 30, American Society of Civil Engineers,

New York, 1992.

[14] Bureau of Reclamation, Design Standards No.

13&Embankment Dams:

Ch. 2: Embankment Design, 123 pp., June 1992.

Ch. 3: Foundation Surface Treatment, 16 pp.,

September 1984.

Ch. 5: Protective Filters, 20 pp., May 1987.

Ch. 7: Riprap Slope Protection, 54 pp., July 1992.

Ch. 8: Seepage Analysis and Control, 42 pp., March 1987.

Ch. 10: Embankment Construction, 55 pp., July 1991.

Ch. 16: Cutoff Walls, 24 pp., June 1991.

[15] "Dewatering and Groundwater Control,"

U.S. Department of the Army, Navy and Airforce, TM

5-818-5, AFM 88-5, NAVFAC P-418, Headquarters,

Department of Army, The Air Force, and the Navy,

Washington, DC, November 1983 .

[16] Bureau of Reclamation, Linings for Irrigation Canals,

1st ed., out-of-print, Reclamation library cat. No. 141604,

149 pp., Denver, Colorado, 1963.

[17] Glickman, A. and R.A. Baumgarten, Compacted Earth

Canal Linings of Low-Plasticity Soil, Bureau of Reclamation

Report No. R-90-11, 63 pp., Denver, Colorado, May 1990.

[18] Jones, C.W., Compaction of Soil on Canal Side Slopes,

Bureau of Reclamation Report No. R-89-05, 39 pp., Denver,

Colorado, June 1989.

[19] Morrison, W.R. and J.G. Starbuck, Performance of

Plastic Canal Linings, Bureau of Reclamation Report No.

REC-ERC-84-1, 114 pp., Denver, Colorado, January 1984.

[20] Farrar, J.A., "Bureau of Reclamation Experience in

Testing of Riprap for Erosion Control of Embankment

Dams," Rock for Erosion Control, ASTM STP 1177, ASTM,

Philadelphia, Pennsylvania, 1993.
CHAPTER 3—CONTROL OF EARTH CONSTRUCTION

311

[21] American Society for Testing and Materials, D 4992:

Evaluation of Rock to Be Used for Erosion Control, Annual

Book of ASTM Standards, vol. 04.08, Philadelphia,

Pennsylvania.

[22] Jones, C.W., Performance of Granular Soil Covers on

Canals, Bureau of Reclamation Report No. REC-ERC-81-7,

66 pp., Denver, Colorado, August 1981.

[23] American Society for Testing and Materials, D 1241:

Specification for Materials for Soil-Aggregate Subbase,

Base, and Surface Courses, Annual Book of ASTM

Standards, vol. 04.08, Philadelphia, Pennsylvania.

[24] Howard, A.K., "Modulus of Soil Reaction Values for

Buried Flexible Pipe," Journal of the Geotechnical

Engineering Division, ASCE, vol. 103, No. GT 1, pp. 33-

43, January 1977, 

[25] Bureau of Reclamation, Pipe Bedding and Backfill,

Geotechnical Branch Training Manual No. 7, Denver,

Colorado, August 1979.

[26] American Society for Testing and Materials, D 4719:

Pressuremeter Testing in Soils, Annual Book of ASTM

Standards, vol. 04.08, Philadelphia, Pennsylvania.

[27] American Society for Testing and Materials, D 1143:

Piles Under Static Axial Compressive Load, Annual Book of

ASTM Standards, vol. 04.08, Philadelphia, Pennsylvania.

[28] American Society for Testing and Materials, D 3689:

Individual Piles Under Static Compressive Load, Annual

Book of ASTM Standards, vol. 04.08, Philadelphia,

Pennsylvania.

[29] American Society for Testing and Materials, D 3966:

Piles Under Lateral Loads, Annual Book of ASTM

Standards, vol. 04.08, Philadelphia, Pennsylvania.

[30] American Society for Testing and Materials, D 4945:

High-Strain Dynamic Testing of Piles, Annual Book of

ASTM Standards, vol. 04.08, Philadelphia, Pennsylvania.

[31] Vesic, A.S., "Design of Pile Foundations," National

Cooperative Highway Research Program&Synthesis of

Highway Practice 42, Transportation Research Board,

National Research Council, Washington, DC, 68 pp., 1977.

[32] Reese, L.C. and J.D. Allen, Drilled Shaft Manual,

"Drilled Shaft Design and Construction Guidelines Manual,"

vol. I and II, U.S. Department of Transportation, Federal

Highway Administration, Washington, DC, July 1977.

[33] Fang, H.Y., Foundation Engineering Handbook, 2d ed,

Van Nostrand Reinhold, New York, 923 pp., 1991.

[34] Bertram, G.E., " An Experimental Investigation of

Protective Filters," Soil Mechanics Series 7, Pub. No. 267,

Graduate School of Engineering, Harvard University,

Cambridge, Massachusetts, Jan. 1940.

[35] U.S. Army Corps of Engineers, "Filter Experiments

and Design Criteria," Tech. Memo. No. 3-360, Waterways

Experiment Station, Vicksburg, Mississippi, April 1953.

[36] Karpoff, K.P., Laboratory Tests on Protective Filters

for Hydraulic and Static Structures, Bureau of Reclamation

Report No. EM-132, Denver, Colorado, April 7, 1947.

[37] Karpoff, K.P., The Use of Laboratory Tests to Develop

Design Criteria for Protective Filters, Bureau of Reclamation

Report No. EM-425, Denver, Colorado, June 20, 1955.

[38] Sherard, J.L., L.P. Dunnigan, and J.R. Talbot, "Basic

Properties of Sand and Gravel Filters," Journal of

Geotechnical Engineering, ASCE, vol. 110, No. 6, pp. 684-

700, June 1984.

[39] Design of Small Dams, 3d ed., 860 pp., Bureau of

Reclamation, Denver, Colorado, 1987.

[40] Koerner, R.M., Designing With Geosynthetics,

Prentice-Hall Inc., Englewood Cliffs, New Jersey, 652 pp.,

1990.

[41] DeGroot, G., Bonding Study on Layered Soil-Cement,

Bureau of Reclamation Report No. REC-ERC-76-16, 33 pp.,

Denver, Colorado, September, 1976.

[42] Casias, T.J. and A.K. Howard, Performance of SoilCement Dam Facings&20 Year Report, Bureau of

Reclamation, Report No. REC-ERC-84-25, 8 pp., Denver,

Colorado, 1984.

[43] Howard, A.K. and J.P. Bara, "Lime Stabilization on

Friant-Kern Canal," Bureau of Reclamation Report No.

REC-ERC-76-20, Denver, Colorado, December 1976.

[44] Knodel, P.C., Lime in Canal and Dam Stabilization,

Bureau of Reclamation Report No. GR-87-10, 14 pp.,

Denver, Colorado, June 1987.
313

Index

A

"A" line, 12

Absorbed moisture, 7a, 16

Access roads, 292 (see also Highways and railroads)

Additives, 46, 101-103, 221, 232, 274

Aerial photographs, 64, 66, 77, 81, 185

coverage of, United States, 64

mosaics, 203

orthophotographs, 66

remote sensing, 66, 73, 74, 76 (see also Remote

 sensing)

U.S. Department of Agriculture, 64

U.S. Geological Survey, 64, 66

use of, 68, 76, 185, 186, 188

Air content, 30

Airport construction, 220

Alluvial deposits, 35, 77, 78, 80

alluvial fan, 78

floodplain, 77

stream channel, 77

terrace, 77

Appurtenant structures, 86

Artesian pressure, 190, 227

Asphalt, 98, 102, 144, 274

Atterberg limits, 3, 7, 10-12, 47, 54, 57, 70, 81, 198 (see

 also Soil consistency, tests)

Auger borings, exploratory, 108, 110, 112, 116 (see also

 Test holes)

continuous-flight augers, 110

double-tube augers, 112

enclosed augers, 116

helical, disk, and bucket augers, 112, 116

hollow-stem augers, 110, 112

advantages of, 112

sizes of, 112

Augers for sampling

hand, 143

hollow-stem, 151, 153

power auger drills, 143

B

Backfill, 5, 51, 225, 226, 235, 280

percussion casing hammer drills, used with, 132

piezometer installation, used for, 135

slurry walls, used for, 235

types of, 225

Backfill about structures, 297

required density of, 297

Backfill grouting, 171

Backfill in pipe trenches, 285, 288

materials for, 288

Backhoe, 104, 105, 235, 263

Ballasting, 222

Bearing capacity, 6, 19, 35, 38, 63, 94, 167, 168, 173,

 225, 226, 233, 296

foundations, evaluation of, 226

piles, 296

Becker penetration test, 132, 170, 171, 189

Bearing strength (see Foundations (investigations))

Bedrock, 63-65, 69, 70, 80, 98, 103, 110, 112, 116, 125,

 129, 132, 136, 161, 165, 170, 187, 194, 196, 201, 203,

 226, 230, 231, 242, 243, 245

contours, 65, 203

Benchmarks, 68, 186, 187, 254

Berm, 274, 293

Blanket, 46, 51, 95, 96, 101

cut slopes, for, 227

description, 218, 222

drainage, 97, 230, 245, 260

materials, earth, for canals, 95 (see also Impervious

 soil (materials))

materials, earth, for dams, 96

protective, 278, 281

riprap, for canals, 101

riprap, for stilling basins, 100

riprap, under, 97

rockfill, 97, 98, 101, 223

sand and gravel, 223

stabilized soils, 299, 302

topsoil or zones, 224

Blasted rock, 223

Blasting, 98, 125, 205, 239, 240, 263, 292

vibratory densification, used for, 240

Blended earthfill, 218, 220, 224

control of, 221

Boils, 245

Borderline classifications, 81, 284

Borehole shear device test, 28

Borrow areas, 47, 96, 102, 105, 143, 164, 189, 194, 204,

 219, 226, 250, 253, 267, 283, 301

alluvial deposits, 77, 78, 80

construction history reports, described in, 268

haul distance from, 95

investigation of, 96, 110, 201, 267

lacustrine deposits, 80

moisture control costs, 54
EARTH MANUAL

314

restoring, 224

slope wash or colluvial deposits, 80

stream deposits, 77

subsurface exploration for, 85, 86, 92, 164

kinds of materials available, 92

Borrow materials, 96, 167, 204, 261, 277, 294

Borrow pit, 53, 183, 217, 219, 221, 250, 254, 260, 261,

 292

cut, depth of, 204, 250

evaluation of, 53, 54

excavation, 226, 254, 277, 293

operations, to obtain proper water content, 250, 254

Borrow-pit inspector, 254

Boulders, 3-5, 10, 24, 80, 81, 96, 103, 104, 108, 116,

 125, 132, 165, 170, 194, 196, 223, 226, 240, 276, 292

size of, 5, 10

Bridge piers, 86, 101

Bridges, 232, 294

Brooming, 304

Bucket augers, 112, 143

Bulldozer pits, 104 (see also Test pits)

Bureau of Reclamation, 1, 58-60, 94, 97, 156, 205, 206,

 211, 242, 250, 289, 298, 310

Buried membranes, 275

C

Caissons, 112, 217, 230, 232

Calcium carbide reaction device, 303

Calyx drill, 136, 140

Canal banks, 46, 224, 233, 276

Canal construction, 95, 101, 226, 273, 275

control techniques, 281-284

dumped fill, 218

selected impervious fill, 218

Canal embankments, 273, 276-278, 280

compacted, 273

moisture requirements for, 280, 283, 284, 286

earth, construction control, 281-284

foundation treatment for, 276

Canals, 54, 64, 85, 86, 230, 232

blanket materials, subsurface exploration for, 92

blankets, impervious (see Impervious blankets)

blankets to prevent erosion, 224, 278 (see also Sand

 and gravel (mixtures) (soils))

borrow areas, 273, 280 (see also Borrow areas)

subsurface explorations for, 283

construction control techniques, 281-284

design features, 273-278

embankments (see Canal embankments)

filter (layer), 275, 281, 282 (see also Filters)

gravel fill, 278, 281

gravel subbase, 281

materials and placing requirements for various fills,

 280

monthly construction progress report (L-29), 282

operation and maintenance roads for, 274, 281

pervious foundation, lining for, 232

riprap for, 101, 278, 281

rock foundation, inspection of, 276, 281

seepage losses, 164, 273, 274, 282

specifications, provisions for, 275, 276, 278, 280, 281

structure backfill, 280

subsurface exploration for (see Subsurface

exploration, line structures)

Canals, lined

buried asphalt membrane, 274

buried bentonite membrane, 274

concrete, 230, 274

description of, 274

earth (see Earth-lined canals)

flexible, 230

Canals, unlined, 273, 307, 308

excavated in rock, 281

Capillary stresses, 33, 54

Casagrande, Arthur, 58

Cement, 101, 221, 291, 301, 302, 305, 306

grout, 103, 243

hydration of, 305

Chalk, 262

Chemical titration, 305

Chutes, 227, 230

Clamshell, 104

Classification group, 3, 52 (see also Soil group)

Classification system, 1- 4, 7, 47, 49, 58, 69, 70, 81, 85,

 95, 191, 203

Clay (clay soil), 3-7, 16, 51, 52, 54, 173, 178, 230, 232,

 241, 245, 261, 288, 295, 306

characteristics of, 3, 4, 30

consistency determined by field vane tests, 174, 178

contraction of, 4

dispersive, 54, 57, 308, 309

expanding, 5

expansive, 4, 41-46, 102, 282, 294-296, 307

modifying, 41

failures, 4

fat, CH, 295

kaolin group, 5

lean, CL, 35

lime, addition of, 307-309

methods for reducing movement of structures due to,

 230

moisture and density effect on, 10, 33

montmorillonite group, 5, 41
INDEX

315

plasticity of, 10, 12

sensitive, 53

Clay balls, 96, 102, 303, 305

definition of, 102

Clay shales, 41, 295

Coarse grains, 4

Coarse-grained soils, 3, 10, 28, 169, 170

Cobbles, 3-5, 10, 24, 77, 80, 81, 96, 103, 108, 125, 132,

 138, 142, 143, 167, 170, 194, 196, 218, 223, 250, 261,

 276, 283, 292

size of, 4

Coefficient of curvature, Cc, 8

Coefficient of permeability, 27, 42, 46, 47

Coefficient of uniformity, Cu, 8, 298

Cofferdams, 64, 235

Cohesion, c, 4, 27, 28, 30

Cohesive strength, 81

Colloids, 41, 69

Compacted backfill in pipe trenches, 285-289

Compacted backfill of clayey and silty soils, 225, 294, 295

Compacted backfill of cohesionless free-draining soils,

 225, 288

construction methods, 225, 288

materials, selection of, 225, 288

Compacted earthfill for rolled earth dams, 247-263

control techniques for, 247, 251-258

design considerations, 247, 250

impervious earthfill zones, design criteria for, 247,

 250

number of passes, 219

placement water content, specifications provisions for

 control of, 254

specifications provisions for earth dams, 250, 251

suitable excavated materials from foundation, use of,

 250

Compacted embankments, 5, 273, 274, 276, 282, 283

Compacted layer, 5, 247, 256, 261, 278, 283, 302, 304

Compacted pervious fill for rolled earth dams

control criteria for construction of, 258

design considerations, 258

Compacted soil-cement, 299, 306 (see also Soil-cement

 and Stabilized soils)

clay balls, 305

compaction requirements, 302

construction provisions, 301, 302

control techniques, 302, 305

control tests (testing), 302, 305, 306

curing, 302

description of, 299

design considerations, 299, 301

materials for, 301

record cores, 306

sampling, 305-307

uses for, 299

Compacted soil-lime, 306-309

Compaction curves, 19, 33, 144, 253, 261

Compaction equipment, 220, 261, 262

Compaction grouting, 240, 241

Compaction of soil, 3, 20, 23, 27, 30, 33, 46, 52, 218-220

curves, 19, 23, 33, 253, 257, 261

definition of, 33

degree, 70

degree required, 219, 257, 289, 292, 293

deviation from, 16

effort, 16, 18

field and laboratory, 257

lifts, thickness of, 219, 262

half-lift, 221

loose, 283

number of passes, 220, 251, 257, 262, 301, 302, 304

tests, 16, 19, 198, 219, 250, 305

Compactive effort, 13, 16, 18, 19, 20, 52, 219, 220, 261,

 264, 269, 283, 288

Bureau of Reclamation standard, 16, 18, 19

Compressibility of soil, 1, 4, 10, 12, 13, 33-35, 51, 52,

 64, 168, 171, 173, 176 (see also Soil, compressibility)

fine sand, 41

Compression, 7, 19, 24, 33

control of, 33, 34

definition of, 30

pressure-compression characteristics, 35-42

pressure-expansion characteristics, 35, 41, 43-45, 47

Compression specimens for soil-cement, 306

Computers

accuracy of, 216

computerized logs, 189, 190

data bases, 66, 67

remote sensing, used in, 75

software, 66, 267, 270, 283

Concrete, 95, 140, 235, 274, 281, 294, 295

Concrete aggregate, 77, 92, 96, 103, 204, 267

procedures for investigation of, 96

sources of, 77, 81, 92, 95, 96, 103, 110, 116

Concrete dams, 142, 157, 182, 262

Concrete Manual, 27, 58, 96, 202, 204, 205

Conduits, 308

Cone penetration test, 28, 86, 94, 105, 116, 146, 171,

 173, 174, 176, 206, 227, 294, 295

Consistency of fine-grained foundation soils, 295

Consolidation, 6, 33, 35, 41, 53, 59, 76, 77, 94, 132, 144,

 146, 176, 217, 220, 221, 226, 227, 233, 235, 236, 245,

 250, 259, 269, 294

definition of, 33

Consolidation tests, 227
EARTH MANUAL

316

Construction control, 7, 8, 15, 16, 19, 20, 27, 167, 198,

 211-218, 220, 221, 306

changed condition, 211

compacted fill unit weight, 20

frequency distribution, 269

importance of, 211

letter instructions for, 220

organization, functions of, 211

pipelines, for, 288, 289

principles of, 211-216

relation to design requirements, 211

when specified, 219

Construction engineer, 212

Construction materials, locating sources of, 68, 69, 77,

 95, 104, 141, 161

Construction stage, 85, 92, 96

Contract administration, 211

Contracting officer, 211, 250, 280, 297

Control testing (see Testing, construction control)

Core barrel, 116, 135, 138, 140

bits, 159

double-tube, 157, 158

large diameter, 157, 158

single-tube, 157

Core barrel samplers, 125, 153, 156

Core box, 158, 161

Core recovery, 127, 129, 135, 136, 138, 159, 190, 191,

 205, 235

Coulomb, 27, 30, 59

Cross sections, 65, 85, 188, 306

Crushed zones, 103

Cumulative grain-size curve, 8, 9 (see also Gradation)

Cut slopes, 227, 229, 230

erosion protection, 229

evaluation of during construction, 227

ground-water effect on, 227

loessial soils, 229

sloughing, prevention of, 227

Cutoff trenches, earth, 218, 242, 243, 246, 247

sloped cutoffs, 243

sloping-side trenches, 242

vertical-side trenches, 243

Cutoff walls, 60, 95, 235, 242, 243, 258, 295, 310

Cuts, 64, 74

D

Damsites

subsurface exploration for, 86, 92

surface exploration for, 74, 86, 108

Darcy' s law, 42

Deep soil mixing, 241, 242

Degree of compaction, 70, 219, 220, 257, 258, 281, 293

Degree of saturation, S, 8, 14

Deltas, 233

Denison sampler, 153 (see also Sampling of soil)

Density

compacted fill, 269, 270, 273

definition of, 7

dry, ıd, 16, 17, 20, 27, 167

dry, ıdmax, in densest state, 49

fill, 270, 283

in place, 164, 168, 263-267, 295

minimum acceptable for canals, 284

natural or in place, 63, 85, 94, 164, 168

procedure for, 49

reduction from frost action, 233

relative, Dd (see Relative density)

test (field) (natural) (in place), 164, 168 (see also

 Field density test)

wet, ıwet, 20, 23

Desiccation, 35, 53

Design Considerations, 235, 236, 240-242, 247, 250, 251,

 258, 299

Diamond Core Drill Manufacturers Association

 (DCDMA), 117

large-diameter high-recovery core barrels, 156

rock core barrels, standardized dimensions for, 157

Diamond drilling, 140, 205

Diatomaceous silts, 53 (see also Silt)

Dilatancy, definition of, 4

Direct shear, 28, 30, 181, 182, 275, 306

large-scale in-place direct shear tests, 182

portable direct shear rock testing device, 181, 182

sliding resistance, relationship to, 30

test, 28

Double-tube sampler, 125

Dragline, 104, 105

Drainage wells, 247

Drains, 37, 46, 96, 97, 134, 235, 236, 247, 292

filter materials, subsurface exploration for, 92

Drifts, 105 (see also Tunnels)

Drill bits, 112, 117, 118, 125, 127, 134-141

Drill holes (see Test holes)

Drill rig, 112, 116, 123, 125, 146, 147, 174

accessories for, 123

Drill rod, 119, 123, 125, 127-129, 134, 135, 138, 140,

 141, 143, 151, 157, 159, 161, 168

Drilling in embankment dams, 140, 141

Drilling machine, 161

Drilling mud, 103, 136, 190

Drilling program planning, 140

Drive samplers, 7

Dry density (dry unit weight), ıd, 8, 35, 40, 273
INDEX

317

Dry unit weight (see Density)

Dumped fill, 218

Dune sands, 81

Dynamic compaction, 236

Dynamic penetrometers, 116, 173

E

Earth, 1, 282 (see also Soil)

Earth dams (see Rolled earth dams)

Earth Manual, 1, 8, 58, 101, 205

Earth-lined canals, 224, 230, 281 (see also Linings)

compacted, thick, 95, 96, 275, 281

compacted, thin, 283

construction control techniques, 284

foundation treatment for, 276, 281

gravel cover for, 278, 281

materials for, 226

materials, subsurface exploration for, 92

recommended thickness for frost prevention, 283

riprap or coarse gravel cover, 278, 281

silting, description of, 274

stabilized soils for, 274

thin, loose earth blankets, 274

types of, 274

typical sections, 275

Earthquake, 19, 53, 57, 65, 67, 206, 221, 235, 240, 310

Ecological and environmental requirements, 224

"Effective" size of soil particles, 8, 9

Elastic rebound, 230

Elastic silts, 286, 289 (see also Silt)

Electrical methods of geophysical exploration, 161,

 164-166

Embankment, 132, 135, 164, 218-222, 252

construction, factors affecting placement of, 257

description of, 218

materials for, 226

rockfill, 262, 263

test section, 252

types of, 218

Embedded instruments, 252

End dumping, 218, 263, 293

Engineering properties of soil, 1-7, 10-16, 27-57, 63, 146,

 168, 188, 201

development of, 219

dynamic, 57, 168, 169

improvement of, 218-220

in situ load testing, prediction by, 174

soil groups, 47, 49-53

Engineering use chart for soils, 49, 51, 53, 95, 224

Eolian deposits, 81 (see also Loess)

Erodibility, 54, 194

Erosion, 308

cohesionless soils, 54

cohesive soils, 54

definition of, 54

Erosion protection, 101, 224, 229, 275

from flowing water, 229, 275

from wave action, 229, 263, 299

from wind and rain, 224

Erosional features, 73, 185

Eskers, 81

Excavation, 3, 54, 196, 220, 221, 226, 288, 289, 291

factors affecting unit cost of, 54

requirements for, 226

Expansion, definition of, 33

Expansive clays, 41-46, 59, 230, 234, 282 (see also Clay

 (clay soil))

Expansive soils, 12, 35, 41, 43, 64, 230 (see also Clay

 (clay soil);

Exploratory holes (see Test holes)

Exploratory methods, 102-141

accessible, 103-105

nonaccessible, 105, 108-116

Explosives, 104, 105, 262

F

Failures, 6, 33, 35, 41, 57, 221, 233, 263, 269, 274, 307

Feasibility stage of investigation

land forms, knowledge, importance of, 77, 80, 81

test hole requirements for, 86, 92

Field classification of soils, 24

Field control laboratories, 212, 213

equipment for, 213

mobile type, 213

purpose of, 212

reports, 216-218

satellite, 213

size and type of, 213

test data, checking and rounding, 213, 216

test data, use of, 212

Field density test, 92, 94, 164, 168, 252, 258, 265, 266,

 282, 284, 288, 306

frequency of, for canal construction, 282

frequency of, for compacted earth fill, 258

frequency of, for highway and railroad fill

construction, 293

location for compacted earthfill, 265

Field investigations for feasibility stage

cost of, 69

initial planning, 69
EARTH MANUAL

318

Field investigations, recording, and reporting data,

 183-205

logging of exploratory holes, 188-201 (see also

Logging (logs) of exploration holes)

maps, 183-188

Field penetration test, 94, 168, 170, 171, 173, 174, 282,

 294

Becker and standard tests, correlations between, 171

Becker penetration test (BPT), 132, 170, 171, 189

cone penetration test, 28, 94, 168, 171, 173, 176,

 178, 189, 295

piezocone, 171, 173

standard penetration test (SPT), 23, 24, 94, 105, 146,

 168, 170, 171, 189, 227, 240, 295

Field permeability test, 47, 164 (see also Permeability)

Field tests, 164, 167, 168, 170, 171, 173, 174, 176, 178,

 179, 182, 183, 216, 217, 305

compacted earthfill for rolled earth dams, summary

 of, 261

compacted pervious earthfill for rolled earth dams,

summary of, 261

in-place density, 94

penetration, 164, 168, 170, 171, 173, 174, 188

reports of, 216, 217

soil-cement, 305

Field tests for exploring foundations, 94, 95, 164

Field vane tests , 174

pocket (Torvane), 178

Fills, 64, 97, 101, 135

types of, 218

Filters, 46, 81, 96, 97, 243, 263, 282

blankets, 222, 243, 282

canals and miscellaneous structures, construction of,

 298

criteria, 224

two-layer, 224

Fine-grained soils, 4, 10, 12, 24, 35, 54, 282, 295

Fines, 3, 4, 225, 239

clayey, GC or SC, 4

definition of, 3, 10

influence of, 3, 4, 10, 52, 236, 262

limitation in amount of, 220

silty, GM or SM, 4

Fixed-piston type samplers, 146

Flap valves, 230

Flat blade dilatometer, 28, 94

Flat plate dilatometer, 176, 178

Flood-plain or valley fill deposits, 77, 96, 97

Foundation Improvement Technology and Dam

Rehabilitations, 235-242

dynamic compaction, 236

fill loading with sand or wick drains, 235, 236

grouting and soil mixing, 240-242

compaction grouting, 240, 241

jet grouting and deep soil mixing, 241, 242

slurry walls, 235

types of foundation problems, 235

vibratory densification, 239, 240

vibrating probes (terraprobes) (vibrorods)

(vibrowing), 239, 240

vibro-compaction/replacement (vibroflotation)

(stone columns), 239

Foundations (investigations), 1, 15, 28, 63, 85, 86, 95,

 102, 103, 108, 168, 267

bearing strength, 94

compressibility, 33, 35, 39

cutoff, 63, 64, 69, 85, 86, 94, 95

description of, 63

evaluation of, 63, 85

excavation and refill, 294

investigation, 63, 164

poor, 63, 86

questionable, 37

satisfactory, 63, 64, 69, 77, 80, 85, 86

settlement, 64

soils, description of, 15

stability of, 103

uplift, 64, 226

Foundations and subgrades (evaluation and control of

during construction) 226-242, 294-296

adequacy of, 226

bearing capacity, 225-227 (see also Bearing capacity)

excavation below ground water, methods of, 227

grouting, 243, 276

inadequate (poor), 225, 232-235, 242, 262, 273

judgment in evaluation of, 226

permeability, 226, 276 (see also Permeability)

piles and drilled shafts, used for, 296, 297

prewetting, 233

rock, 292

settlement and uplift, 57, 281, 282

solution channels, open holes, or cracks, treatment of,

 276

stability, 227-230 (see also Stability)

tests for evaluation of, 226, 294

unwatering of, 295

water movement, damage to, 57

Foundations for miscellaneous structures, 296, 297

Foundations for rolled earth dams, treatment of

abutment contacts, 243

construction control techniques, 247

diversion and care of stream, 245

earth surface, preparation of, 247

embankment, 247, 251

excavation and stockpiling of suitable construction

 materials, 250
INDEX

319

firm formation, preparation of, 247

shale surfaces, preparation of, 246

specifications provisions for, 245-247

stability control, 242-245

stabilizing fills, 245

toe drains, 243

type of pipe for, 245

unwatering, 243, 246

Freezing index, 230

Friant-Kern Canal, 307, 308

Friction factor, tan 1, 28, 30, 49

relative density relationship for coarse-grained soils,

 28

Frost action, 54, 230, 275, 282

conditions for, 230, 233

definition of, 54

factors affecting, 53

frost heave, 54, 219 (see also Clay (clay soil),

 expansive)

Frozen embankment, 250, 260

Frozen soil, 250, 260

G

Geologic (soil) profile, 86

Geologic data, 69, 187, 188, 198, 201

Geologic profile, 86

Geologic section, 68, 201, 243

Geological information, comprehensive list of sources, 69

Geologist, 69, 141, 188, 198

Geophysical methods of subsurface exploration, 161-165

favorable conditions for, 162

hazardous waste sites, 163

types of, 161, 164

usefulness of, 161

Glacial deposits, 80

Glacial deposits (glacial drift), 80, 81

Glacial till, 98

Global positioning system, 186, 188

Gradation (grain-size distribution), 3, 8-10, 96, 219

10-percent-finer-than size, D10, 8, 9

30-percent-finer-than size, D30, 8

60-percent-finer-than size, D60, 8

description of, 8

gap, 8

laboratory test procedure, 8

processing to improve, 219

riprap, 263

skip, 8, 80, 96, 142, 143

upper size limits, 10

Gradation analyses tests, 7

Gravel, 3, 4, 96, 108, 219, 224, 261, 274, 292

definition of, 3

fine, surfacing, 281

well-graded, 8

Gravel blanket, 222-224, 227, 229, 278

placement, 222

rock sizes for various thickness of for canals, 278

Gravel soil, 52, 220

definition of, 51

poorly graded, GP, definition of, 51

well graded, GW, definition of, 51

Gravel surfacing for roads and parking areas, 281

Ground water, 63, 67, 69, 135, 227, 229, 246

artesian zones, 63

contamination studies, 163

control of, 246

level, 63, 108

removal of, 227

table, 63, 65, 77, 81, 103, 104, 108, 110, 227, 229

normal, 63

perched, 63

Grout (grouting), 135, 136, 242, 243

bituminous, 243

chemical, 243

Grout curtain, 242, 243

Grouting, compaction, 240, 241, 299

Grouting, jet, 241, 242

H

Halloysite, 6, 7, 16

Hand augers, 108, 143

Hand sampling, 142-146

Hardpan, 70, 226, 227

Hazardous waste studies, 163

Heart Butte Dam, 213

Heave, definition of, 33

Heaving, 4, 41, 54, 157, 230, 245, 296

Helical augers, 112

High compressibility, soils of, CH, MH, 4, 33

Highly organic (peaty) soils, Pt, 51

Highways and railroads, 64, 92, 97, 183, 220, 292-294

base course material, 222, 224

borrow pits, specifications provisions for, 293

control techniques, 293, 294

design features of, 292

earthwork, specifications provisions for, 292, 293

embankment, construction control of, 292-294

embankments, construction specifications provisions

 for, 292, 293

State highway specifications, 293
EARTH MANUAL

320

subgrade, preparation of, 292

subsurface explorations for, 92

surfacing, base course, ballast, 92, 97, 222, 224

Hydraulic fill, 218, 221, 222

engineering assistance, 222

Hydraulic fracturing, 140

Hydraulic gradient, 42, 46, 227, 243

Hydrometer analysis, 8, 213, 261

I

Ice lenses, 54, 230

Impervious blankets, 222, 224, 243

Impervious linings, 80

Impervious soil, 96, 226, 231, 280

Impervious soil (materials), 95, 96, 140, 222

sources of, 77, 80, 95

use for, 95, 96, 132

Impervious, range of permeability, 46

In situ tests, 24

importance of, 174

in-place tests, distiction between, 174

penetration tests, 23

shear strength, 28, 174

Inadequate foundation conditions, 242, 262 (see also

 Foundations and subgrades (evaluation and control of

 during construction)

common methods of treatment, 232-235

Inclinometer, 134, 135

Index properties of soils, 7-27, 46, 63

Index tests, 63, 92, 202, 226

use for, 7, 24, 27, 94

Indirect methods of exploration, 63

geological interpretation, 63

geophysical, 63

In-place density test (see Density and Field density test)

In-place moisture (see Moisture content, w)

In-place permeability tests (see Permeability, field test for)

Inspection, 211, 212, 219, 220

final, 256

report, 256

Inspection trenches, 278, 283

Inspector, 212, 281, 282, 305, 306

borrow pit, 254

compacted earthfill, duties of, 256, 265

duties of, 212, 254, 282, 284, 294-296, 304-306

embankment, 254

foundation, 250

miscellaneous fills, 264

riprap and rockfill, 262

soil-cement, 303-306

Instrument installation, 264, 265

Instrument installation for rolled earth dams, 265, 269

final report on earth dam instrumentation (L-16), 265

inspection, 265

instructions, 269, 270

record tests, 265

Internal friction, 10, 24, 27, 28, 30, 259

Internal vibrators, 225, 280, 284, 288, 291

J

Jet grouting, 241, 242

L

Laboratory (see Field control laboratories)

Laboratory classification of soils, 49, 198

Laboratory testing, 1, 141, 201, 204, 269, 297

density, definition of, 16, 53

field testing, compared to, 94, 174, 175

logs, recorded on, 196, 198

Laboratory testing for construction control, 15, 16, 305,

 306

when required, 218, 219

Lake sediments or lacustrine deposits, 80

Land forms or topographic features, 77-85

Landslides, 65, 74, 77, 86, 135, 187

Laterals, 64, 218, 273, 283, 285

Layers of thickness, 283

Layers, thickness of, 220, 221, 288, 293, 298

adjusted for oversize, 220

Lean clay, 5, 30, 35, 51, 275

Lifts, thickness of, 219, 262, 263

half-lift, 221

loose, 283

Lime, 41, 47, 57, 59, 95, 102, 205, 217, 221, 299,

 306-310

Limestone, 53, 165

Limiting moisture tests, 251

Linings, 95, 96, 221-225, 274 (see also Canals, lined and

 Earth-lined canals)

description, 218

hard surfaced, 95

materials selection, importance of, 226

Liquefaction, 19, 52, 53, 58, 81, 168, 169, 171, 206, 221,

 233, 235, 236, 240, 310 (see also Quicksand)
INDEX

321

Liquid limit, LL, 4, 10-14, 23, 35, 40, 41, 49, 281, 307

definition of, 10

Load-consolidation testing, 94 (see also One-dimensional

 consolidation test)

Load-expansion characteristics, 41 (see also Clay (clay

 soil), expansive)

Loess, 35, 37, 38, 46, 53, 81, 112, 156

characteristics of, 6, 81

Kansas and Nebraska, in, 37

Logging (logs) of exploratory holes, 104, 105, 188-201,

 265, 269, 282

computerized log, 189

geologic logs of drill holes, 190-194

identification of, 189, 194, 196

information required, 189, 190

log forms, 189-201

log of test pit or auger hole, 194, 196, 198, 201

requirements, 5

rock cores, 191, 194

M

Manual tests, 3, 220

Maps, 64, 96, 183

accuracy of, 186

agricultural soil maps, 69-72

extent of, in United States, 69

base, 186, 188

contours for, 68, 185, 186

coordinate systems for, 184-187, 189

datums, 186, 187

details required for, 187

geologic maps, 68, 69, 86

areal, 69, 86

bedrock, 65, 69

structural, 65, 69

surficial, 65, 69, 86

geophysical, 65

global positioning system (GPS), 186, 188

hydrologic, 65

projections, 186, 187

river surveys, 65, 68

scale ranges of, 183

site geologic, 186-188

detailed surface geologic mapping, 188

drawings for, 187, 188

phases of, 187

preliminary surface geologic mapping, 188

requirements for, 187

site-specific, 184-186

sources of information, 64-72, 77, 96

strip, 68

topographic maps, 65, 68, 77

coverage, 68, 185

index to, for States, 73

scales, 65, 68, 183

Mass, definition of, 7

Materials (soils) investigation, 63, 64, 108

Materials of specific properties, 100, 299

exploration for, 95-101, 301

sources, economics of, 95

Mats, 33

Maximum dry density, 16, 35, 49, 51, 257, 269, 273, 283,

 293, 297, 298, 308

Mechanical tamping, 257, 266, 284

Menard pressuremeter, 28

Mica, 6, 70, 72

Microwave oven, 303

Mineralogy, 5

Miscellaneous fills in dam embankments, 264

record tests for, 265

Miscellaneous structures, 294-299

foundation excavation, specifications provisions for,

 294-296

foundations, checking properties of, 294, 295

pile and drilled shaft foundations for, 296, 297

Mixing, 218

Mixing machines, 308

Modified soil, 92, 101, 102, 218, 221 (see also Stabilized

 soils)

inspection of, 221

Modulus values, 28, 94, 165

deformation, 174, 182

shear, 57, 164, 174

Mohr strength envelope, 49

Moisture content, w, 3, 4, 6, 8, 10-24, 27, 30, 33, 35, 52,

 63, 102, 170, 219, 221, 256, 258, 273, 283, 305, 308

descriptive terms, 10, 15

gravel, wg, 16

in place, 63, 85, 103

Moisture control, 20, 23, 24, 27, 33, 80, 218, 219, 254,

 256, 269, 273, 284

costs of, 54

nuclear devices, use of, 256

Moisture Teller device, 303

Monthly reports, 216

Montmorillonite (bentonite), 5, 33, 41, 95, 103, 123, 136,

 141, 159, 235, 243, 274

Morainal deposits, 80
EARTH MANUAL

322

N

Natural water content

moisture tests, 94

Needle-density test, 23

Nonplastic fines, 4 (see also Silt)

Normal stress, ), 28, 30, 175

Normally consolidated, definition of, 35

Nuclear devices for determining moisture content, 167

Number of passes, 219, 220, 251, 257, 262, 301, 304

O

One-dimensional consolidation test, 41

Open-end push tube sampling, 94

Optimum moisture content, wo, 16-19, 23, 33, 35, 49, 53,

 80, 102, 219, 250, 254, 261, 269, 273, 283, 308

Organic clay, OL, 51

Organic material, 1, 85, 102, 226, 286, 288, 291

Organic matter, 4, 16, 53, 102, 218, 232, 282

Organic silt, OL, 51

Osterberg-type sampler, 147

Outcrops, 185, 187

Outwash fans, 81

Ovendrying, 16, 305

effects of, 16

temperature, 16

Overburden, 92, 100, 103, 110, 112, 127, 135, 245

Overconsolidated, definition of, 35

Oversize, 9, 53, 96, 102, 112, 142, 194, 196, 219, 220,

 250, 256, 258, 261, 262, 266, 268, 283, 301

Oversize materials, 142, 194, 196, 220, 250, 258, 268,

 301

removal of, 283, 301

special embedding of, 266, 268

P

Palisades Dam, 213

Parking areas, 281

Particle shape, 97

diameter, D, 8, 9

rounded, subrounded, subangular, and angular, 97

PCEARTH, 267, 270, 283

Peat, 51, 218, 232, 286, 288, 289

Pedological system of soil classification, 69, 70, 72

description of, 69, 70, 72

divisions of, 69

example of, 70, 72

limitations and value for engineering purposes, 72

soil series of, 69

soil type, 70

textural classification of "A" horizon, 69, 70

Penetration resistance, 20, 23-26, 132, 157, 190, 191, 295

field, 168, 170

needle curves, examples of, 20, 23

Percentage and decimal use, 8

Percolation, 42, 190, 191

control of, 42

Periodic progress (L-29) reports, 266, 267

Permeability, 10, 27, 30, 33, 41-49, 52, 53, 64, 69, 81,

 86, 94, 96, 97, 101, 138, 220, 222, 226, 259, 264

coefficient of, determining, 47

control of, 46, 47

definition of, 41

effect of gravel, 46

field test for, 94, 164

horizontal, 46

in embankments, 46, 47

laboratory test for, 41

ranges of, 42, 47

sand-gravel mixtures, 46

through foundations, 46

vertical, 46

Permeable soils, compaction of, 220

Pervious blankets under concrete structures, 224 (see also

Sand and gravel (mixtures) (soils), blankets)

Pervious materials

construction control of, 297

sources of, 81, 95-97

Pervious soils, range of permeability of, 46

Piers, 33, 86, 101, 230, 232

Piezocone, 171, 173

Piezometers, 265

installation of, 135

Piles, 33, 230, 232, 233, 296, 297

driving tests, 94

jetting systems for, 296

loading tests, 63, 94, 296

specifications provision for, 296

Pipe bedding, 102, 287, 288

soil-cement, 289, 291, 292

Pipe trenches (see Pipelines)

Pipelines, 85, 86, 102, 225, 285, 286, 288, 289, 294

alternate types of pipe, 285

backfill materials and placement requirements for,

 285, 288, 291

design features, 285

excavation for, 285, 288, 289, 291

safety requirements, 289

soil-cement bedding for, 289, 291, 292

construction control, 291
INDEX

323

materials for, 291

unconfined compressive strength limits, 292

specifications provisions for, 285-288

trenches, 285, 288, 289, 291, 292

uncompacted bedding requirements, 285, 287-289

Piping, 46, 96, 219, 231, 283, 295

control of, 57, 235, 245, 258

Piston-type (drive) sampling, 94, 103

Pitcher sampler, 153

Plastic fines, 4, 102, 291 (see also Clay (clay soil))

Plastic limit, PL, 4, 10-13, 35, 41, 307

definition of, 12

Plasticity, 3, 10, 11

chart, 12, 13

index, PI, 4, 12-14, 41, 230, 234, 275, 281, 295, 307

needle (Proctor), 20

Plasticity index, PI, 4, 12-14, 41, 230, 275, 281, 295, 307

Plowing, 221

Pneumatic rollers, 222, 225

Point-load strength test, 178

consistency determined by field vane tests, 181

Pore fluids, 28, 49

freezing of, 54

Pore pressure, 33, 52, 171, 173, 176, 221, 236, 239, 240,

 250, 269

buildup in cohesive soils, 269

construction, 57, 251, 259, 264, 269

Pore-air pressure, 29, 30

Pore-water pressure, u, 28-31

Porosity, n, 12-14, 194

Porosity, n, 8, 12, 13

definition of, 8, 12-14

Portable direct shear rock testing device, 181, 182

Post hole augers, 108

Power auger drills, 143

Powerplants, 232, 294

Preliminary investigations, 187, 188, 219

objectives of, 219

Pressure pipe, 285

Pressure relief wells, 46

Pressure-compression characteristics, 35-42

unsaturated deposits, in, 35

Pressure-expansion characteristics, 35, 41, 43-45, 47

Pressuremeter testing, 174, 175

purpose of, 174

rock, 174

Prewetting, 230, 233

Proctor compaction test, 16-18, 20

Proctor needle-moisture test, 20, 23

Puddled fill, 221, 222

Pugmill, 101, 301, 302

Pump sumps, 235

Pumping plants, 86 (see also Miscellaneous structures)

Q

Quarrying, 97, 262

Quartz, 70, 81

Quicksand, 52 (see also Liquefaction)

R

Railroads, 72, 183, 187, 292

Rapid compaction control method, 23, 220, 267, 293

Rebound, 33, 35, 41, 230

Reclamation Instructions, 206

Reconnaissance design, 80

Reconnaissance stage of investigation, 72, 77, 80, 202

land forms, knowledge, importance of, 77

surface exploration, 77-81, 85

Record tests, 265, 304

Refill, foundation, 294

Relative density, 19, 20, 23, 24, 28, 41, 51, 198, 222,

 224, 267, 288

effects on friction factor, 28

examples of, 20

field penetration relationships for sand, 168

maximum, 16, 19-22

minimum, 15, 19-22

Relative density tests, 222, 267, 284, 288, 295

frequency for compacted pervious fill, 261

materials applicable for, 289, 294, 295

Relative firmness, 289

Relief wells, 46, 234, 243, 245

Remote sensing, 72-77

aerial photographs, 73, 74

applications to geotechnical engineering and geology,

 76

availability of imagery, 76

definition of, 72

mission planning, 76

multispectral scanner imagery, 75

nonphotographic, 72

radar imagery, 76

resolution, 72

thermal infrared imagery, 74

Reports for construction control, 265-269

canals, 268

earth dam instrumentation, 269, 282

final construction, 217, 218

final embankment construction, 267-269

inspectors' daily, 216, 265

monthly administrative, 216

rolled earth dams, 266, 267

summary construction progress (L29), 217, 267
EARTH MANUAL

324

summary of earthwork construction data, 267

transmittal of, 269

types required, 216

Reports of investigations, 202-204

construction materials, 203, 204

contents of, 203

final, 203

foundations and earthwork, 203

grouting test holes, 103

progress, 203

reconnaissance stage, 202

specifications stage, 103

Required excavations, 64, 226

materials, sources of, 64

Reservoir floor, 242

Reservoir sites, subsurface exploration for, 86 (see also

 Subsurface exploration, damsites)

Reservoirs, 95, 96, 222, 224, 233

protective covers, materials for, 96, 101

water loss from, 86

Residences, 294

Residual soils, 53, 77, 81, 85

field test sections, 85

special laboratory tests, 85

Retaining walls, 297, 299

Rigid structures, 35, 140, 218, 226, 227, 230, 233

Riprap, 15, 95, 97-101, 219, 222, 263-269, 278

blast test for, 98

competitive sources for, 100

fragments, size of, 98

gradation of, 263

investigative procedures for, 101

laboratory tests for, 98, 101

other sources of, 98-101

placing of, 262, 263

quarrying and blasting for, 263, 292

requirements for, 223

rock sizes for various thicknesses of, for canals, 268,

 275, 278

satisfactory materials for, 97

specified sizes, 281

subsurface exploration for, 92, 110

Roads, 4, 64, 66, 68, 72, 85, 86, 184, 218, 222, 224, 232,

 274, 281, 288, 292, 299 (see also Highways and

 railroads)

Rock, 4, 95, 125, 156, 222, 262

crushed, 5

sound, in embankments, 262, 263

uniaxial and radial jacking tests in, 182, 183

unsound, in embankments, 263

Rock (firm) foundation surfaces, preparation of, 247, 281

Rock blanket, 227

Rock core drilling, 136-140

conventional and wireline core drills, 138-140

core diameters, 136

logging cores, 191, 194

shot or calyx drills, 140

Rock fines, 97, 222, 223

Rock foundation, 64, 246, 262, 265, 281

Rock fragments, 78, 80, 95, 97, 98, 101, 103, 108, 138,

 204, 223, 247, 250, 261, 266, 292, 293

grading for, 223

requirements for, 223

Rock rippability, 164

Rock slopes, stability of, 181, 182

Rock sources

investigative procedures for, 101

requirements for, 95, 97, 98

Rockfill, 15, 97, 101, 132, 219, 222, 262, 263

advantages of, 262

placing of, 262, 263

specifications, 262

uses of, 262

Rockfill (rock) blankets, 101, 223, 224, 227, 229

construction of, 223, 224

Rocky Mountains, 80

Rolled earth dams, 86, 92, 96-98, 219, 220, 242-273

abutments for, 86, 105

compacted earthfill for (see Compacted earthfill for

 rolled earth dams)

concrete cutoff walls, 243

control criteria for embankment, 269, 273

cutoff trench, 246

downstream drainage blankets, 96, 97, 224

downstream slopes, protection of, 223, 224

drilling procedures, 140, 141

foundation, pervious, treatment for, 51, 218, 219,

 243, 252, 258

foundation treatment (see Foundations for rolled earth

dams, treatment of)

instrument installations (see Instrument installation for

 rolled earth dams)

materials investigation for, 98, 226

grid system for, 86

miscellaneous fills for, 264

riprap for (see Riprap)

rockfill for (see Rockfill)

subsurface investigation for, 86 (see also Subsurface

 exploration, damsites)

upstream slopes, protection of, 97, 101, 223, 264, 299

Rolled earthfill, 218-220, 250

compactive effort for, 219

construction of, 219, 220, 251

inspection (see Inspection and Inspector)

variables affecting, 227

moisture content for, 219
INDEX

325

Rolled embankment, 246, 247, 258, 265

Roller data, reporting of, 267

Rotary drilling, 105

Rotary drilling methods, 116-140

churn/cable tool drills, 136

Diamond Core Drill Manufacturers Association

 (DCDMA), 117

dimensional standards, 117-123

Rotary drills, 123-135

definition of, 123

drill hole logs, 190-194

drive hammers, 123

fluted Kelly, 129, 130

Kelly rods, 129

uses of, 129

hollow-spindle, 127-129

advantages of, 127

borehole sizes, 129

uses of, 127

horizontal rotary, 134, 135

borehole sizes, 135

reverse-circulation (rotary and percussion), 129, 131,

 132, 143

advantages of, 132

Becker drill, 132

borehole sizes, 129

rotary-table, 125

top-head drive, 125, 127

top-head drive with percussion casing hammer,

 132-134

borehole sizes, 127

types of, 125

Rounding of test data, 216

S

Safety (safety requirements), 47, 104, 105, 212, 227

Safety and Health Regulations for Construction, 212

Sampling (samples) of soil, 10, 63, 102-183, 191, 201,

 202, 302, 305-307

casing advancer, 157

cohesionless sands, 108

contamination of, 103, 143

continuous, 151

disturbed, 63, 94, 108, 110, 127, 142-144, 168

shipping, 143, 144

size of, 201, 202

for laboratory testing, 102, 103, 141, 143, 144, 156,

 174

hand sampling methods, 142-146

mechanical sampling methods, 143, 144, 146-157, 168

medium to hard soils and shales, 153, 156

purpose of, 94, 141, 201

representative, 94, 142, 201

riprap, 202

saturated cohesionless, 146, 149

selection of, 92, 94

shipping, 143, 144, 146

soft to moderately firm cohesive, 149, 151-153

soil-cement, 302, 305, 306

compression test specimens, 306

undisturbed, 16, 23, 49, 63, 80, 94, 103, 105, 108,

 127, 144-146, 149, 151, 153, 156, 157, 174, 201,

 227, 265, 282, 284, 288, 293-295

importance of, 28

requirements for, 201

unsaturated water sensitive, 156, 157

visual examination of, 92, 102, 142, 158, 201

Sampling for construction control, 212, 302, 303, 305, 306

Sampling of dam embankments, 141

Sampling of rock, 157, 176

accuracy and dependability of data, 159

core boxes, 161

double-tube core barrel, 157, 158

large diameter core barrel, 157, 158

point-load strength test, 178, 181

rock pressuremeter (dilatometer), 174

single-tube core barrel, 157

triple-tube core barrel, 158, 159

Sampling of soil, 294, 295

Sampling test holes, 103

Sampling, during subsurface exploration, 201, 202

Sand, 41, 46, 51, 96, 146, 174, 178, 235 (see also Silt or

 sand)

clean, 168, 173

limits for, 10

poorly graded clean, SP, 8

properties of, 52, 168, 169

well-graded clean, SW, 8

with silty fines, SM, 261

Sand and gravel (mixtures) (soils), 77, 95, 110, 116, 220,

 224-226, 258, 275, 281, 284, 299

blankets, 222-224, 242, 245, 258

compaction of, 220, 224

filter, 281

investigating using bucket augers, 116

natural deposits of, 224, 226

permeability, effect of gravel and density, 46

under riprap, 222

uses for, 95, 239

Sand dunes, 233

Sandbars, 233

Sandstone, 5, 53, 80

Satellite imagery, 66, 76
EARTH MANUAL

326

Satellites, 186

Saturation collapse, 33

Scarifying or loosening, 33, 257, 288

Sealing wax, 146

Sedimentary rocks, processes, 77

Sedimentation, 77, 80 (see also Gradation)

Seeding, 217, 225

Seepage, 52, 74, 77, 81, 85, 96, 227, 273, 274, 281

control of, 235, 241, 247, 273, 283

losses in canals, 164, 273, 282

water, 219, 245, 247, 258

Seismic methods of geophysical exploration, 161, 164, 165

Seismic problems for dams, 236, 240, 241

Selected fill, 218, 219

Selected impervious fill, 218

Selected material, 221, 222

Selected sand and gravel fill, 218, 219

Selective excavation, 102, 218, 301

Semipervious fill, 261, 262

Semipervious soils, permeability range of, 46

Separation plant, 250

Settlement, 5, 64, 173, 174, 225-227, 230, 240, 241, 250,

 251, 264, 269, 276, 294, 295

differential, 269, 295

settlement-plate monitoring systems, 135, 136

Shale, 5, 30, 41, 53, 80, 101, 146, 153, 158, 166, 198,

 223, 227, 230, 246, 262, 263, 286, 295

Shear planes, localized, 269

Shear strength, 27, 28, 30, 49, 173, 174

apparent, 30, 41

borehole shear testing, 175, 176

definition of, 27, 28

direct measurement of, 28, 30 (see also Field vane

 tests)

direct shear, 28

flat plate dilatometer, measured with, 176

in situ, 28, 174

indirect measurement of, 33 (see also Field

 penetration test)

in place, 28

pocket vane shear test, 178

residual, 30, 32

rock slopes, of, 181, 182

soil groups, of, 52

triaxial, 28, 29

Shear testing, 28, 30, 58, 174-178, 182 (see also Triaxial

 shear)

Shear tests, 41, 49, 50, 59, 63, 182, 191, 206, 227, 275

 (see also Triaxial shear)

Sheepsfoot roller (see Tamping rollers)

Shipping samples, 143, 144, 146

Shrinkage limit, SL, 10, 12, 295

definition of, 12

Shrinkage of soil, 5, 33

definition of, 33

Shrinking, 95, 224

Sieving, 16, 213

Silt, 3, 4 (see also Silt or sand)

characteristics of, 53

loose, ML, 35

Silt or sand, 261, 291

foundations of, 282

Sinkholes, 231

Slag, 5

Sliding resistance, 30

Slope protection, 97, 98, 101, 223, 263, 275, 299

alternate methods, 95, 101

downstream of dam embankments, 98, 101, 223, 224

downstream of stilling basins, 223

Slopes (see Cut slopes)

Slopewash deposits, 97

Sluiced fill, 221, 222 (see also Hydraulic fill)

construction of, 222

inspection of, 222

Slurry walls, 235

Soil

blending (mixing) two soils, 53

chemical composition of, 69, 70

classification, 47, 63, 95, 143

components, 3, 5, 6

compressibility, 10, 33-35

elastic silt, MH, 49

identification of, 24

mixing, deep, 241, 242

moisture, 7, 10, 11, 15

mortar, 20

physical properties of, 14-16, 20

upper size limits for various applications, 10

Soil classification systems, 85

pedological (see Pedological system of soil

 classification)

textural (see Pedological system of soil classification)

unified (see Unified Soil Classification System)

Soil consistency, 11, 12, 24, 235, 295

degree of, 10, 12

relative, Cr

, 12

states (stages) of, 10

tests, 168

Soil group, 1, 3, 194

great groups on agricultural soil maps, 69

properties of, 12, 47, 49-53

Soil mechanics, 12, 28, 58, 59, 205, 310

Soil profile, 70, 72, 86

Soil properties, 14-16, 20, 53, 69, 77, 85, 110

changes in, 53

delineation of with continuous-flight augers, 110
INDEX

327

Soil stratum, description of, 63, 94, 110

Soil Survey Manual, 72, 204

Soil-cement, 95, 98, 101, 102, 159, 267, 289, 291, 292,

 302 (see also Stabilized soils and Modified soil)

materials for, 101, 102

slurry, 102

testing required, 102

Soil-cement bedding for pipelines, 289, 291, 292

construction control, 291

materials for, 291

Soil-cement slurry, 102

Soils (materials) investigation, 108

objectives, 63

purpose of, 63, 102, 108, 141, 142

Solid state, 3, 12

Soluble solids (salts), 16, 24, 27, 46, 53, 64, 69

effect on concrete and earth structures, 27

Special compaction, 222, 225, 247, 251, 264 (see also

 Backfill and Rolled earthfill)

Special processing, 76, 95, 97, 219

Specific gravity, Gs, 8, 13-15

apparent, 13, 14, 20

bulk specific gravity, 14, 15, 20

use of, 13, 15

Specifications, 211, 212, 225, 262, 299

definite requirement type of, 212

performance type of, 211

procedures type of, 211

requirements, 212, 219

Specifications stage of investigation, 92, 94

exploration requirements, 86, 108

field tests for, 94

selection of samples, 92

test hole, requirements for, 86

Spillway apron slabs, 230

Spoil piles (see Talus and spoil piles)

Spread footings, 33

Spreader, 264, 301

Stability, 101, 181, 219, 277

cut slopes, of (see Cut slopes)

foundations, of, 227, 229, 230

pervious saturated sands, of, 52

Stabilized soils, 92, 101, 102, 299, 301-309

compacted soil-cement, 299, 306

description of, 101

materials for, 101, 102

testing, 102

uses of, 101, 299

Standard penetration test, 23, 24, 28, 146, 170, 171, 189,

 295

State highway specifications, 293

Statistical analysis, 269

Stilling basins, riprap for, 100, 101

Stockpiling, 96, 102, 143, 225, 250, 259, 277, 302

Stratification of soils in place, 80, 85

Stream deposits, 98

Strength of soil, 49-54, 57 (see also Shear strength)

Stripping, 217, 224, 226, 232, 243, 247, 267, 268, 276,

 282

Structure foundations, 63, 64, 201

classes of, 63, 64

on rock, 64, 201

Subgrades (see Foundations and subgrades (evaluation and

 control of during construction))

Subgrades, heaving of, 54

Sublaterals, 273

Subsidence, 59, 230

Substations (see Miscellaneous structures)

Subsurface exploration, 72, 85-95, 108, 127

damsites, 86, 92, 164

geologic features, 86

geophysical techniques of, 161

line structures, 86

point structures, 86

purpose for, 72, 85, 108, 127

borehole sizes, 127

Subsurface sections, 201

reports, use in, 201

Surface sodding, 229

Surface vibrators, 222, 225, 280, 288

Swell, 33, 41, 92, 96, 167, 198, 274

definition of, 33

Swelling, 5

Swelling soils, 33, 53

embankments of, 33

Switchyards, 224

T

Talus and spoil piles, 86, 97, 98

Tamping rollers, 225, 267, 280, 297

curves for, 253

form for recording data on, 266, 267

Terms and units of measure, 7, 8

Terrace deposits, 77, 96

Test holes, 85, 86, 92, 94, 103, 108, 282, 283, 294

borehole shear testing, 175, 176

depths of, 86, 103, 105

designation of, 189

foundation, for, 103

location of, 85, 86, 92

log of (see Logging (logs) of exploration holes)

number required, 86

order of, 143
EARTH MANUAL

328

outlet works and spillway structures, for, 86

protection of, 103

sizes of, 103

spacing of, 86

support of, 103, 108

tunnels, for, 92

use of, 103

Test pits, 103-105, 142, 143, 167, 258

depth of, 104

hand-dug, 104

pumping system for, 104

safety, 104

Test sections of earthfill material, 252

Test sections of residual soils, 85

Testing, construction control, 15, 20, 258, 265, 302, 305

modified soil, for, 221

soil-cement, for, 302, 305

Tests on soils, 92, 94

purpose of, 92

Textural classification of soils (see Pedological system of

 soil classification)

Thinwall push samplers, 149, 151

Topsoil, 70, 198, 222, 224, 225, 232, 234, 243, 246

Topsoil blanket or zones, 224, 225

construction and inspection requirements, 225

material sources, 224

Total material, determination of consistency, 10

Tractors, 222, 225, 261, 288, 297, 301

Transmission lines, 184, 232

Transmission towers, 86

subsurface exploration for (see Subsurface

 exploration, point structures)

Trench, 142, 283, 292, 295

pipe, 285, 288, 289, 291, 292 (see also Pipelines)

Trenches, 92, 96, 103-105, 108, 140, 142-144, 187-189,

 194, 198, 201, 204, 218, 235, 242, 243, 246, 247, 278,

 282, 283, 288, 289, 292, 295

Triaxial shear, 28-30, 49

test, example of, 28

Trinity Dam, 213, 265

Truck-dumped fill, 218

Tunnels, 92, 103-105, 135, 142, 161, 179, 194, 267

test holes for, 92

U

U.S. Agricultural Stabilization and Conservation Service,

 64

U.S. Coast and Geodetic Survey, 185

U.S. Department of Agriculture, 64, 67, 69

Aerial Photography Field Office, 64

agricultural soil maps of, 69, 70, 72

U.S. Forest Service, 64

U.S. Geological Survey (USGS), 64-68, 73, 108, 185

access to data bases, 67

bulletins of, 66

products, 65

quadrangle maps, 68

remote sensing products, 66, 67

software, 66

technical reports of, 65

U.S. Natural Resources Conservation Service, 64

Unconfined compressive strength, 23, 24, 292, 307

Underdrains, 230, 234

Uniaxial and radial jacking tests in rock, 182, 183

Unified Soil Classification System, 1, 3, 4, 7, 47, 58, 70,

 81, 95, 191, 198, 203 (see also Soil, classification)

basis of, 3

Unit weight

compacted-fill, 20, 23

definition of, 8

dry, ıd, 19-22

dry, ıdmax, in densest state, 20-22

dry, ıdmin, in loosest state, 20-22

laboratory maximum, 19, 20

theoretical, ıt

, 20

wet, ıwet, 19

Units of measure, 7, 8

Unlined waterway, 232

Uplift, 41, 64, 97, 234, 282

expansive soils, cause of, 230

hydrostatic, 282, 286

pressure, 41

V

Vane feeder, 302

Vane test (see Field vane tests)

Vibratory densification, 239, 240

influence of, 239

Vibratory rollers, 222, 225, 260, 262

Vibratory-compacted embankment, 218, 220, 222

construction, inspection of, 220

Visual examination for identification of soils, 7 (see also

 Soil, classification)

Void ratio, e, 8, 12, 13, 35, 41, 42, 263

definition of, 12, 14

densest state, emin, 14, 19

loosest state, emax, 19

volume of voids, Vv, 13

Volume change, 30, 33-41
INDEX

329

W

Wall stabilizer, 103, 123

Warehouses (see Miscellaneous structures)

Waste banks, 274, 277

Water loss from reservoirs, 86

Water table, 24, 46, 52, 63, 65, 77, 81, 103, 104, 108,

 110, 112, 116, 143, 146, 151, 153, 157, 164, 165, 194,

 220, 226, 227, 234, 245, 295

Water testing, in test holes, 103

Water volume, Vw, 54

Water-cement ratio, 291

Wave erosion, 97, 98, 219, 229, 263, 299

Wearing surface, 219, 281

Weathering, 63, 70, 78, 80, 81, 97, 194, 262

Weight, definition of, 7

Well points, 110, 227, 246, 295

Well-graded sands and gravels, 4

Wick drains, 235, 236

Wireline drilling, 123, 128, 138, 151

casing advancer, 157

continuous cores, required for, 127

core barrel systems for rock coring, 159

drill rod sizes, 120

Workability of materials, 27, 41, 52-54, 64, 92

Z

Zoned embankments, 243

Zoning, 33, 46, 57