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NUREG/CR-3545

Comparison of Energy Measurements

in the Standard Penetration Test

Using the Cathead and Rope Method

Phases I and II Final Report

Prepared by W. D. Kovacs, L. A. Salomone, F. Y. Yokel

National Bureau of Standards

Prepared for

U.S. Nuclear Regulatory

Commission
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NUREG/CR-3545

RA

Comparison of Energy Measurements

in the Standard Penetration Test

! Using the Cathead and Rope Method

Phases I and II Final Report

Manuscript Completed: July 1983

Date Published: November 1983

Prepared by

W. D. Kovacs, L. A. Salomone, F. Y. Yokel

! Geotechnical Engineering Group

National Bureau of Standards

Washington, DC 20234

Prepared for

Division of Health, Siting and Waste Management

Office of Nuclear Regulatory Research

U.S. Nuclear Regulatory Commission

Washington, D.C. 20555

NRC FIN B7457

!

ABSTRACT

Studies conducted on the Standard Penetration Test (SPT) and its present use in

engineering practice show that a wide variation in the use of different pieces

of SPT equipment, procedures and personnel results in a range of energy measured in the drill rods from 30 to 85 percent of the standard SPT energy. The

potential energy and kinetic energy of the hammer were measured prior to impact,

and the energy passing through the drill rods was calculated from a force-time

measurement in the rods. It was found that safety (type) hammers tend to allow

more kinetic energy to pass through the hammer-anvil system than donut (type)

hammers. The energy passing through the drill rods was calculated by using a digital processing oscilloscope and an SPT Calibrator. Lessons learned in

evaluating the energy measurement by these two methods are discussed. The

combined effect of the drill rig used, the operator and his procedures, and the

SPT equipment should be considered when energy is to be evaluated. The variation of average energy ratio within various drill rig models was found to be

about as large as that among drill rig models. It was therefore impossible to

make a statistically significant estimate of the reference energy which is

representative of the average energy delivered in the U.S. practice.

iii
ft .

.

. ei . •. ...

A. X« - • o 0. £
EXECUTIVE SUMMARY

The National Bureau of Standards performed 1087 energy measurements on various

drill rigs performing Standard Penetration Tests (SPT) on seven sites. The

data from these tests were combined with other available data and the following

conclusions were drawn:

1. The variability of the energy passing through the drill rod as delivered by present U.S. equipment and procedures is too great to be eliminated by a modification of procedures alone. Equipment, as well as procedures,

would have to be modified to achieve satisfactory results.

2. The adjustment of SPT N-value data to a common reference energy appears

to yield promising results; however, the energy would have to be measured in

the drill rod rather than the point of hammer impact. The method presently

used to measure the energy in the drill rod produces reasonable and checkable

results, but has not yet been verified by an independent theory or measurement

system.

3. While it is desirable that the reference energy approximate a current

or past national average energy, the data sample available is not large enough

to permit a statistically significant estimate of the national average energy.

4. The energy passing through the drill rod is not the only source of

variability in the SPT results. The use of liners in the SPT sampler is also

an important source of variability. The effect of the liner and the liner

clearance provided in U.S. samplers must be considered when evaluating SPT

results from other countries.

The following recommendations are made on the basis of these conclusions:

1. SPT equipment and procedures be established which minimize the

variability of the blow count. This would require a tripping mechanism, a standard hammer/anvil/drill rod system, a standard spoon with or without

liner, and standard drilling procedures.

2. Until the SPT equipment is standardized:

(a) The energy passing through the drill rod should be monitored and

the test results referenced to a standard energy, either the national average

or an internationally accepted energy level.

(b) The use of liners in the sampler should be eliminated.

(c) The test procedures be modified to minimize the test variability.

3. The following interim test procedures should be specified for

determining liquefaction potential:

(a) Safety (type) hammer with AW drill rod stem with a stroke of at

least 35 in (889 mm). v
(b) Two turns of new rope around the cathead.

(c) Use of an 8 in (203 mm) clean, shiny cathead.

(d) AW (parallel wall) drill rod.

(e) Rotary drilling with mud.

(f) Upward deflecting wash drilling bit.

(g) Blow count rate of 30 to 40 blows/minute.

(h) An SPT sampler with no liners [I.D. of 1.5 in (38.1 mm)].

(i) The mud fluid level in the bore hole should at all times be at

the top of the bore hole.

(j) A 2 in (50 mm) colored band shall be permanently marked on the

hammer guide pipe (from 28 to 30 in above the anvil) to help the operator

produce an average 30 in fall height.

(k) ERi should be constantly monitored and recorded.

[Procedures c, e, f, and h are based on findings by Schmertmann (1977).]

4. The following additional research be conducted:

(a) Check the present load cell integration method of determining

ERi by an independent energy theory and associated measuring system.

(b) ER-£ measurements for typical Japanese SPT practices to better

interpret available liquefaction data.

(c) Study of the effect of drill rod configurations on the energy

transmission.

vi
TABLE OF CONTENTS

Page

ABSTRACT iii

EXECUTIVE SUMMARY v

LIST OF FIGURES viii

LIST OF TABLES x NOTATION xili

PREFACE xv

1. INTRODUCTION 1 1.1 PURPOSE 1 1.2 SCOPE 1 1.3 BACKGROUND 2

2. EXISTING SPT EQUIPMENT AND FIELD TEST PROCEDURES 5 2.1 AVAILABLE DRILL RIGS 5

2.2 HAMMER TYPES 5 2.3 DRILL ROD TYPES 16

2.4 FIELD SPT PROCEDURES AND OPERATOR CHARACTERISTICS 16

3. CURRENT METHODS OF ENERGY MEASUREMENT 20

3.1 POTENTIAL ENERGY OF HAMMER BEFORE RELEASE 20

3.2 KINETIC ENERGY JUST BEFORE IMPACT 20

3.3 ENERGY PASSING THROUGH THE DRILL ROD 20

3.3.1 Theory 20

3.3.2 Application of Theory 21

3. 3. 2.1 Digital Processing Oscilloscope 23

3. 3. 2.

2

Other Equipment 23

3.4 RESULTS OF ENERGY MEASUREMENT STUDIES 26

3.4.1 General 26

3.4.2 Results of Energy Measurement 34

4. ESTABLISHMENT OF A REFERENCE ENERGY LEVEL (REL) 50

4.1 GENERAL 50

4.1.1

The Need to Establish a National Average Energy (NAE) ... 50

4.2 PRESENT DATA ON THE NAE 52

5. FINDINGS, CONCLUSIONS AND RECOMMENDATIONS 60

5.1 FINDINGS 60

5.2 CONCLUSIONS 62

5.3 RECOMMENDATIONS 63

6. ACKNOWLEDGMENTS 66

7. REFERENCES 67

APPENDIX A. TABULATION OF FIELD DATA ER^ PERCENT FROM SPT

CALIBRATOR A-l

APPENDIX B. TABULATION OF INDIVIDUAL MEASURED FALL HEIGHTS

DURING TESTING B-l

vii
LIST OF FIGURES

Page

Figure 1.1 Illustration of the various energies measured during this

study 3

Figure 2.1 Definitions of the number of turns and the angle a and E for (a) CCW rotation and (b) CW rotation of the cathead .... 8

Figure 2.2 SPT 140 lb (63.5 kg) hammers - (a) pin-guided hammer

(b) donut hammer with typical dimensions shown (c) safetytype hammer with two typical designs (d) donut-type hammer

and anvil used in Japan 9

Figure 2.3 Illustration of drill rod wall types - (a) parallel wall

(b) upset wall 15

Figure 2.4 Typical results of fall-height vs. blow number from

experienced drill rig operators performing the SPT - (a),

(b), and (d) usual rhythmic method; (c), hold-drop method .. 18

Figure 3.1 Schematic showing the key elements of an SPT energy

calibration instrument (modified after Hall, 1982) 24

Figure 3.2 Photograph of SPT energy Calibrator 25

Figure 3.3a Examples of typical force-time histories of safety hammers

and donut hammers 29

Figure 3.3b Examples of typical force-time histories of safety hammers

and donut hammers 30

Figure 3.4 Two examples of electronic shorting of load cells during

impact 31

Figure 3.5 Illustration of compressive wave return force-time history

and trigger duration (integration) time 33

Figure 3.6 Comparison of energy ratios using the SPT Calibrator and

the Digital Processing Oscilloscope (DPO) 43

Figure 3.7 Histograms of energy transfer ratio, ETR, for donut and

safety hammers 45

Figure 3.8 Comparison of force-time wave forms when a 2-ft (61 cm)

section of BW parallel wall drill rod is inserted just

below load cell 47

Figure 3.9 Variation of average energy ratio, ER-l vs. drill rod

length for two types of SPT hammers . All data include K2

correction 49

viii
LIST OF FIGURES (Continued)

Page

Figure 4.1 Comparison of SPT N values using alternative donut and

safety hammer with energy corrected Nc values to ER^

equal to 55 percent (after Robertson et al., 1982) 51

Figure 4.2 Comparison of SPT N values using safety hammer and F

(donut) hammer with energy corrected Nc values to ER^

equal to 55 percent (modified from Schmertmann and

Palacios, 1979) 55

Figure 4.3 Comparison of SPT N values using safety hammer and donut

hammer with energy corrected Nc values to ER^ equal to

55 percent 56

Figure 4.4 Summary of data to date of energy ratio for F(t), ER^

(a) safety hammers (b) donut hammers 57

ix
LIST OF TABLES

Page

Table 2.1 Characteristics of Some Drill Rigs Used to Perform the

SPT 6

Table 2.2 Summary of Drill Rig Models Used in Engineering Practice

with Numbers Greater than One 7

Table 2.3 Summary of Typical SPT Drill Rod Information from

Manufacturer's Catalogs 14

Table 3.1 Tabulation of Calibrator Display Numbers for Drill Rod

Areas 27

Table 3.2 Tabulation of Test Series Performed and Test Conditions .... 35

Table 3.3 Tabulation of Results and Testing Variables Using Two

Turns of Rope Around the Cathead 37

Table 3.4 Summary of Energy Data from Individual Blows 39

Table 3.5 Summary of Average Energy Ratios for Velocity 48

Table 4.1 Tabulation of Average Energy Ratio, ER^ 53

Table A-l Tabulation of Field Data, ER^, percent, from SPT

Calibrator, Series 79 - 90 A1

Table A-2 Tabulation of Field Data, ER^, percent, from SPT

Calibrator, Series 91 - 100.1 A2

Table A-3 Tabulation of Field Data, ER^, percent, from SPT

Calibrator, Series 100.2 - 100.10 A3

Table A-4 Tabulation of Reinterpretated Field Values of ER^,

percent, from SPT Calibrator A4

Table A-5 Tabulation of Field Data ER^ , percent, from SPT

Calibrator, Series 102 - 109 A5

Table A-6 Tabulation of Field Data ER^, percent from SPT

Calibrator, Series 110 - 119 A6

Table A-7 Tabulation of Field Data ER^, percent from SPT

Calibrator, Series 120 - 130 A7

x
LIST OF TABLES (continued)

Page

Table B-l Tabulation of Individual Fall Heights During Testing,

Series 82-98 B1

Table B-2 Tabulation of Individual Fall Heights During Testing,

Series 102-112 B2

Table B-3 Tabulation of Individual Fall Heights During Testing,

Series 113-123 B3

Table B-4 Tabulation of Individual Fall Heights During Testing,

Series 127-130 B4

NOTATION

A

2

= cross-sectional area of the drill rods, cm

c = theoretical compressive or p wave velocity of sound in the steel

drill rod, m/s

cm

= measured compressive or p wave velocity of sound in the steel drill

rod , m/

s

D = donut hammer

DPO = Digital Processing Oscilloscope

E

o

= Young's modulus of the drill rods, N/m^

Ei = energy passing through the drill rods at the point of measurement,

as determined by equation 3.2; J

Ev

= energy for velocity, i.e., kinetic energy just before impact, J

E* = theoretical free fall energy assuming a 30 in (762 mm) fall, equals

4200 in-lbs (475 J)

ER

±

= energy ratio for F(t) based on a 30 in (762 mm) fall, E^/E

ERi Calib 5= energy ratio for F(t) from SPT Calibrator

ERi DPO = energy ratio for F(t) from integration using the DPO

ERim := measured energy ratio for F(t)

ERic = the selected energy ratio for F(t)

wV = energy ratio for velocity, E

v

/E*

ETR = energy transfer ratio = ER-j/ERv = E^/Ev

Fi = incident compressive force, F(t) measured in the drill rods

F(t) = measured force-time history in the load cell during impact

g

= acceleration of gravity

H = measured hammer fall height

Ki = correction factor to account for the location of the load cell below

the anvil, eq. 3.3

k2

= correction factor based on drill stem length, eq. 3.4

xiii
Kc

l

Mh

N

Nc

S

t

tm

W

A£

P

<*i

= correction factor to take into account that the measured compressive

wave velocity is less than the theoretical wave velocity, eq. 3.5

= distance from the point of impact to the bottom of the sampler

= U - aa)

= mass of the hammer

= blow count, N-value, or penetrations resistance, blows per foot

= corrected blow count for a specified energy

= measured blow count

= safety hammer

= time

= measured integration time

= hammer weight

= distance from the point of impact to the load cell

= mass density of the drill rods

= incident stress measured in the drill rods

xiv
PREFACE

This is the final report of studies performed under phases I and II of

interagency agreement RES-80-121 between the U.S. Nuclear Regulatory Commission

and the National Bureau of Standards. Some of the data presented were generated in studies sponsored by the U.S. Bureau of Reclamation and the California

Department of Water Resources.

xv

1. INTRODUCTION

1.1 PURPOSE

One of the most significant recent developments in the evaluation of cyclic

liquefaction potential^/ of sands has been the identification of the large

number of factors which significantly affect the cyclic characteristics of any

given sand. It has been shown that all of these factors correlate with the

penetration resistance. Most factors which increase the resistance of a sand

to liquefaction also tend to increase the penetration resistance in the Standard Penetration Test (SPT) as defined by ASTM D 1586 ( Schmertmann , 1978; Seed,

1979). For this reason, reasonably good correlation has been observed between

cyclic characteristics and penetration resistance (Seed, 1979). Kovacs (1979),

Kovacs et al., (1977) and Schmertmann (1978) have demonstrated the wide variability in the conditions utilized in this supposedly standardized test procedure. For a given site, standard penetration resistance values can vary by a factor of 3 or more at a given depth and relative density. Schmertmann (1978)

presents a qualitative comparison of penetration resistance with liquefaction

factor of safety and suggests a useful degree of correlation between SPT

N-value and the factor of safety against liquefaction. However, a necessary

prerequisite for using the Standard Penetration Test as a measure of the cyclic

liquefaction potential of sands is an increase of its reliability by better

standardization. However, Serota and Lowther (1973) and Marcuson and

Bieganousky (1977) have pointed out from the consistency of their results that

the SPT is reproducible if test variables are controlled.

This study provides information which can be used to improve the reliability

and reproducibility of the Standard Penetration Test.

1.2 SCOPE

The plan of research consisted of two phases: Phase I, preliminary studies on energy calibration, and Phase II, establishment of a national average energy.

These phases involved:

Phase I :

• Information gathering on present SPT use and practice.

• Selection of methods and equipment to calibrate drill rig systems.

Phase II :

• Use of the calibration methods selected in Phase I to calibrate

representative drill rigs now being used in engineering practice, and

to assemble a data base that can be used to assemble a "national

average energy" (the average of the energies transmitted through the

drill rod in U.S. SPT practice).

1J As described by Seed et al., (1983).

1
1 . 3 BACKGROUND

Variables affecting the reproducibility of the Standard Penetration Test include

personnel, equipment, and procedures. While some of the equipment and procedures

that affect the test are standardized, many are not.

The variables affecting the SPT, which are summarized by Kovacs et al., (1981),

directly or indirectly affect the energy that is transferred through the drill

rods to the sampler. Schmertmann and Palacios (1979) concluded that the energy

reaching the sampler is inversely proportional to the blow count, N. Thus, if

the variability of energy passing through the drill rod can be reduced, the

N-value will be more reproducible and consistent.

Figure 1.1 illustrates the locations where energy was measured during this

study. In figure 1.1, a 140 lb (63.5 kg) hammer falls from, an assumed height

of 30 in (76 cm) (Point A) and has a potential energy of mgH, or 4200 in-lbf

(475 J). In an ideal free-fall system, all of the potential energy would be

converted into kinetic energy at Point B when the hammer impacts the anvil.

However, because the hammer release mechanism does not produce true free fall,

the kinetic energy prior to impact (Point B) is less than the potential energy.

Further energy loss occurs through the anvil (Point B’). The available kinetic

energy, Ev , produces compressive stress wave energy, E^, in the drill rod as measured at Point C by a load cell. Because of energy transmission losses

through the anvil and drill rod, the energy in the drill rod, Ej_ , is less than

the available kinetic energy, Ev. The efficiency of the anvil to transmit the

available kinetic energy has been defined by Kovacs et al., (1981), as the

energy transfer ratio, ETR.

The methods used to evaluate the energy available in the SPT test include:

a) measurement of actual hammer fall height (Potential Energy)

b) kinetic energy just before impact, Ev

c) energy passing through the drill rods as measured by a load cell

located at a minimum of ten drill rod diameters below the anvil, E^.

Kovacs et al., (1977), Kovacs (1979), Kovacs et al., (1981) and Goble and Ruchti

(1981) have measured a) and b) above. On the other hand, Schmertmann and Smith

(1977), Schmertmann and Palacios (1979) and Kovacs et al., (1981) have measured

the energy passing through the drill rods. The results of these studies have

documented the wide variation in the measured energies [30 to 85 percent of the

free-fall energy (Schmertmann and Palacios, 1979)] for the SPT using different

drill rigs. Because of this variation, the corresponding range in N values

could vary by a factor of three in the same soil at the same location. One

important key to improving the effectiveness of the SPT is a reduction in the

variability of the energy passing through the drill rod, E^. This can be

accomplished by either calibration of the test or standardization of the equipment used. Calibration of the test may be accomplished in three steps:

1) The selection of a measurement method which will allow reliable and

economic evaluation of the energy being delivered by drill rig

equipment now used in U.S. engineering practice.

2
I I

I STANDARD

SPT ENERGY

FOR 30 in. (76 cm] FALL:

-(a) POTENTIAL ENERGY

mg-H = 4200 in-lbf

SAMPLER

(b) kinetic energy of hammer

Ev = ’/2 m Vi

2

(c) ENERGY TRANSMITTED

THROUGH THE DRILL ROD

Ej = f (force 2 -time]

mg = Hammer weight

H = Hammer fall

E y = Kinetic energy just

before impact

m = Hammer mass

Vj = Hammer velocity

just before impact

Ej = Energy in drill rod

Figure 1.1 Illustration of the various energies measured during this study

3
2) Measurement of the energy delivered by various types of drill rigs

encountered in typical U.S. engineering practice.

3) Establishment of a Reference Energy such as the National Average

Energy suggested by Kovacs et al., (1981) with which penetration

resistance values (blow counts or N values) can be correlated.

This study addresses the calibration of the SPT (the three items above) and is

presented in accordance with the tasks outlined in section 1.2. Standardization of the test procedures and equipment would require a modification of SPT

standards to minimize the variables that now exist in the SPT.

4
2. EXISTING SPT EQUIPMENT AND FIELD TEST PROCEDURES

This section describes the wide variability in equipment and test procedures

encountered in engineering practice in the United States and abroad which

contributes to the drill rod energy, Ej^, variation.

2.1 AVAILABLE DRILL RIGS

Various manufacturers fabricate a wide variety of drill rigs for soil

exploration. These drill rigs have different features which influence the

penetration resistance obtained during the test. The standard penetration test

is performed primarily by means of using a rope and cathead to raise and lower

the 140 lb (63.5 kg) hammer. Other "lifting" devices are also commercially

available. They include, but are not limited to, automatic free fall hammers

and automatic and semiautomatic hydraulic hoisting devices. A partial listing

of available drill rigs used to perform the SPT is presented in table 2.1.

Figure 2.1 assists in defining the terms a, B, and cathead rotation direction

referred to in the table. The number of turns of rope around the cathead is

defined (Kovacs, 1980) as the angle in degrees of contact the rope makes around

a cathead divided by 360. The contact angle will vary with the drill rig used

and the direction of cathead rotation (see figure 2.1). For a "nominal 2

turns," the actual number of turns will be approximately 1 3/4 or 2 1/4 turns,

for counterclockwise (CCW) and clockwise (CW) rotation, respectively.

Two studies were made of the number and model of drill rigs presently being

used to perform the SPT in the U.S. In one study, the various State Highway

Departments were asked to list the drill rigs they used to perform the SPT.

In the second study, members of the Association of Soil and Foundation Engineers (ASFE) were asked through ASTM (Kovacs, 1982) to list the manufacturer,

model, and number of drill rigs they used to perform the SPT. In some instances, some of the consulting firms reported that they do not own drill

rigs and contract out their drill services. Thus, it is possible that some of

the drill rigs listed may have been mentioned more than once if more than one consulting firm within a city uses the same drilling contractor. Table 2.2

summarizes the results of the two studies on drill rig population. It is

recognized that the numbers in Col. 2 of table 2.2 are substantially below

what the individual manufacturer has actually built and represent only a partial listing of the actual drill rigs used in engineering practice.

2 . 2 HAMMER TYPES

A variety of types of 140 lb (63.5 kg) hammers are currently used to perform

the SPT. The present ASTM standard (D 1586) does not specify a particular type

of hammer. They include: a) pin-guided hammer; b) donut shaped hammer; c)

safety hammer; and d) Japanese donut hammer. Figure 2.2a, taken from Fletcher

(1965) shows the pin guided hammer. Note the presence of the hard wood cushion

block which strikes against the top of the exposed drill rod. The presence

of the cushion block tends to moderate the peak force. The 44 in (112 cm) long

pin inserted in the drill rod guides the hammer during its fall.

5
Table 2.1 Characteristics of Some Drill Rigs Used to Perform the SPT

Company

(1) Model(2) AT Turns(3)

Cathead Diameter

(inches)

(4)

C.H. Speed

(RPM)

(5)

C.H. Speed

(FPM)

(6)

Cathead Rotation( ^

)

Direction

(7)

Rope(^)

Angle

(degrees)

(8)

No. of Crown

Sheaves

(9)

Diameter

of Sheave

(inches)

(10)

Wgt. of Crown

Sheave

(pounds)

(11)

Dist. from Crown Sheave

to C.H.

14.5 to 19.5

(12)

Rope(^)

Diameter

(inches)

(13)

Acker N-5C -.25 6 123 193 CCW 2 1 12 18 14 1 N-5W +.25 6 123 193 CW 2 1 12 18 14 1 N-10 +.25 6 110 173 cw 4 1 12 18 16 1 N-18 +.25 8 68 142 CW 4 1 12 18 25 1 ADII -.25 8 160 335 CCW 7 2 8 8 24 1 MKII -.25 6 141 221 CCW 4 1 12 18 22 1 MP +.25 6 136 214 cw 3 2 10 10 23 1 Mot Cat +.25 4.5 172 203 cw -3 1 4.75 2 14 0.75

Soil Mech -.33 6 145 228 CCW -30 2 4.75 2 10 0.75

Central 45B +.18 8 454O) 950

(3) CW(4 ) 30 2 8 6 14.5 to 19.5 1 Mine 45C + .18 8 382 800 cw 30 2 8 6 13.5 1 Equipment 55 +.18 8 454 950 cw 30 2 8 6 20.5 to 24.4 1 75 +.25 8 454 950 b

( 6 ) 0-20 2 8 6 20.5 to 27.5 1 450 +.25 8 454 950 B 0-20 2 8 6 19.5 1 550 + .25 8 454 950 B 0-20 2 8 6 19.5 1 750 -.2 8 544 1139 CCW 0-20 2 8 6 20.5 to 24.5 1 750 YL +.25 8 463 970 B 0-20 2 8 6 26 1

Failing 1250 -.2 6.5 100 170 CCW 15 1 10 12 25 1.25 CF-15 -.2 6.5 100 170 CCW 15 1 10 12 25 1.25 1500 -.22 6.5 100 170 CCW 10 1 9.3 11 39.1 1.25 250 -.2 6.5 100 170 CCW 15 2 5.5 5 20 1.25 FA-100 -.2 6.5 100 170 CCW 15 1 10 12 20 1.25

Mobile B-30S +.25 6 249-781 391-1227 cw 0 2 7 4.5 NA 1 Drilling B-33 +.25 8 129-815 270-1707 cw 0 2 7 4.5 NA 1 B-47 + .25 6 280 440 cw 0 2 7 4.5 14 1 B-40L12 +.25 8 195 408 cw 0 2 7 4.5 11 1 B-40L17 +.25 8 195 408 cw 0 2 7 4.5 16 1 B-41L22 +.25 8 195 408 cw 0 2 7 4.5 21 1 B-50 +.25 8 72-190 151-398 cw 0 2 7 4.5 18 or 23 1 B-53 +.25 8 65-192 136-402 cw 0 2 7 4.5

‘ 18 or 23 1 B-56 + .25 8 228 478 cw 0 2 7 4.5 23.2 1 B-61 + .25 8 85-540 178-1317 cw 0 1 7 13.4 26 1 B-80 +.25 8 65-192 136-402 cw 0 2 7 4.5 20 1

Soil Test DR 2005A -.25 6.5 0-288 0-490 B - 2 6 1.5 14.5 1 Sprague & 142 -.25 8 48-305(5) 101-639 CCW 0 2 10 25 20 1 Henwood 40C -.25 6.5 124-774 211-1317 CCW 0 1 16 35-40 10 1 37 -.25 6.5 98-273 167-465 CCW 0 1 10 25 10 1

(1) See figure 2.1 for definition.

(2) See figure 2.1 for definition. Nominal angle o given for horizontal drill rig position.

(3) Maximum vaues given for CME rigs.

(4) Both directions possible.

(5) High range speed depends on gear used.

(6) Both directions.

(7) Manila rope recommended.
Table 2.2 Summary of Drill Rig Models Used in Engineering Practice with Numbers >1

MFGR & Model

Total

(3+4)

ASFE

Survey

Hiway

Survey

(1) (2) (3) (4)

Joy

B12 23 23

22 5 5 125

RAM ROD11

Misc. 5 1 4

Meyhew

200 5 5 500 3 3 600

1000 2 2 Misc. 3 1 2

Mobile Drill

B30 11 7 4 B305 7 4 3 B31 4 4 B33 10 3 7 B34 7 4 3 B40 2 2 B40L 43 20 23

B50 27 16 11 B52 11 4 7 B53 30 20 10

B56 27 8 19

B61 87 61 26

B80 4 2 2 Minute Man

Misc. 3 2 1

Penn Drill

Test Borer 5 5

SIMCO

2400 4 4 4000TR 10 8 2

Sprague & Henwood

36 4 4 37

40C 97 38 59

142 2 2 Monkey 4 4 Misc. 1 1

1 MFGR & Model

Total

(3+4)

ASFEa SurveyHiway

Survey

(1) (2) (3) (4)

Acker

AD II 16 14 2 Hillbilly 20 3 17 LD11 2 2 MC 23 7 16

MK II 14 5 9 MP 2 2 N10 4 4 SM 2 2 TH 4 4 Misc. 9 6 3

American Rig

550 M

Misc.

4 4

1

CME

45B 57 40 17 45C 40 25 15

55 120 85 35

65

75 27 19 8

85

450 3 3 550 12 12

750 6 6 750XL 17 12 5 Misc. 3 1 2

Concore

A-5 Senior 7 7 Misc. 1 1

Failing

36 16 16

250 8 5 3 750 11 11 1250

1500 53 33 20

2000 2 2 CDF 2 3 3 CF15

FA10D

MD-1

Misc. 5 3 2

The following model drill rigs were also mentioned in the surveys as having only one

rig.

BOYLES BBS25

Bucyrus Erie

Caldwell 150

CP 15

Damco 500

a Kovacs (1982).

Frankz

Houston HIVAC

Hydradrill

Knight & Stone

Little River

Longyear 1; 24; 34; Junior

Sullivan

Wint. W Portadrill

7
Figure 2.

P

a. CCW rotation (1.81 turns shown)

P

Definitions of the number of turns and the angle a and 3

for (a) CCW rotation and (b) CW rotation of the cathead
9
1

Figure 2.2 SPT 140 lb (63.5 kg) hammers - (b) donut hammer with typical

dimensions shown

10
11

Figure

2.2

SPT

140

lb

(63.5

kg)

hammers

-(c)

safety

hammer

with

typical

designs
KNOCKING

HEAD

12

Figure

2.2

SPT

140

lb

(63.5

kg)

hammers

-

(d)

donut-type

hammer

and

anvil

used

in

Japan
The donut (shaped) hammer is shown in figure 2.2b and is manufactured as a right circular cylinder as well as an oval cylinder. Generally, the inside

diameter of the hammer is larger than the outside diameter of the slip pipe by

approximately one quarter-inch. The "drive ring" is an optional piece of equipment that is used with a donut hammer by some operators to protect the face of

the hammer and the anvil during driving.

Figure 2.2c shows typical safety hammers which were developed in the mid 1950's

by the California Division of Highways. The bottom collar of the safety hammer

tends to maintain the alignment between the hammer and anvil during the fall.

One safety hammer manufacturer provides a stroke of 29.75 in (75.6 cm). Consequently, the average fall height using this hammer will be below the 30 in

(76 cm) standard. Safety hammers are manufactured with variable size drill

rods. The AW rod size is the most popular. In addition, the hammer rods used

may be either hollow or solid rods. The rod connection to the anvil or impact

block may be either welded or threaded with a lock pin. The implication of the

variable rod cross sectional area on energy transfer and measurement is

discussed in section 3.2.

For comparison purposes, figure 2. 2d shows the standard hammer, knocking head

(anvil), and rod size that are used in Japan (Japanese Industrial Standard,

JIS A1219-1961 (Reaffirmed: 1976). Generally the Japanese hammer is smaller in

diameter and taller than U.S. hammmers; the anvil is considerably smaller than

the U.S. anvil.

Some district offices of the U.S. Army Corps of Engineers and the Waterways

Experiment Station use a hydraulically operated chain driven trip hammer.

Marcuson and Bieganonsky (1977a, b) have used a hammer of this type in their

studies. The hammer itself is approximately 5 1/2 in (140 mm) in diameter and

15 3/4 in (400 mm) long, and consists of a steel casing that is filled with

lead. "The hammer is mechanically lifted to a 30 in (760 mm) drop height by

two lugs positioned on a continuous chain. The chain is driven by a hydraulic

motor connected to the hydraulic system of the drill rig. The rate of driving

(is) approx. 15 blows/min. .

. " (Marcuson and Bieganonsky, 1977a).

The following numbers summarize the distribution of hammer types obtained from

ASFE study (Kovacs, 1982) where 180 questionnaires were sent out and 116 replies

were received.

71 - Safety hammer (56 percent of total)

41 - Donut hammer (33 percent of total)

14 - Pin-guided hammer (11 percent of total)

126 Total (some respondents use more than one hammer type. Seven

respondents did not know what type of hammer was used and 6 did not

give a reply.)

13
Table

2.3

Summary

of

Typical

SPT

Drill

Rod

Information

from

Manufacturers

Catalogs

cd - CO *-H

X

X)

O XI *-H ON CO ON r-H CM CO COm o

Dei

•“H rH CM co vd- co -3- CO

m

<Xo -'N

m - co O • X

xm

x f-H o mm

—I CO r-H oo

rH r—i CM Csl CM r-H CNI rH CM co

M o O

0) co ~N

mmm

Pl, - X ONm • • • o O

<N rH • o co

X r-H

X

X

X co rH i-H CO •-H f-H

x

b0 X

0) co /—NX o m o 5 - X X • o o • o f-H •—* rH 'w' CO X r-H CO m ON rH

/>

CM

X

4J CO

XX

Q 0) 3 /"'S \ f-H f-H M CO X co — \ ex rH co X 3 *H CM »-H ^H CM

'w'

H

<u o

rH

X CO

X <r CO

Q

x e rH \ •-H \ \ M 3 X X "*—

rH

—s f-H co 3 CO m o 3 H *—H f-H f-H f-H CM

ex,

CM

X co

/—s rH CO ^ 00

X 'd- CO CO

es c m \ ON \ \ \ \ \ O X m m CNI co co CO r—

m

f-H r~H f-H CM f—

r-H CM CM

H3 o 3 /N O 3 <t rH ON m co r-H CM O X CD CM /-s CO o CO On p'- r-H X U 3 Mf CO 00 CO CM 1^ rH r-H CM CM O <3 x 'w' • • • • • • • • •

<U o o r-H »-H o r—

f-H

—• CM

CO V-/ 1 >cH

<u r—

rH

H rH /^N 3 3 co

X

XXX 3 3

cxX

<u

H /-N

CO CM

X

XX

X

X

ex 3 V-/ X 33N H X

CO /*mm\ 3 3 3 X »H Cd < 3 Cd <J 03 § M T3 Q o X

<o bO x 3 X x rt X >

ex 3 3O X O i—l3 u 5 3O X x: 3

4J CO X Cl, 3 33 3X0

14

Usually

furnished

with

parallel

wall

for 1

and 2

ft

lengths
COUPLING

03

03GW

03G

>>

4-1

03S

03O

S-i 034-> 4-) 0) 03

4-> 003

r-t J=,

CO• CM

03M3

bO

•H

15
2.3 DRILL ROD TYPES

A variety of drill rod sizes are available and permitted by ASTM D 1586 to

perform the SPT. The rods are available in 1, 2, 3, 5, and 10 ft (0.30, 0.61,

0.91, 1.52, and 3.05 m) lengths including coupling. Drill rods are available

in upset wall and parallel wall thicknesses. The parallel wall rods have a constant cross-sectional area throughout their length (except for the coupling);

while the upset wall rods have a reduced wall thickness in the interior of the

rod, just past the threads (see figure 2.3). Table 2.3 summarizes typical

dimensions of drill rods available for the SPT. For the single letter size

rods, either parallel wall or upset wall is available. For the double letter

size (W symbol for heavier wall thickness), both wall types are available.

For the AW size, both wall types are available for different lengths. Usually

only the 1 and 2 foot sections of BW and NW size are parallel wall sizes,

while the 5 and 10 foot sections come in upset wall. The importance of crosssectional area in energy measurement will be discussed in section 3.2. Since

1961, the problem of drill rod size variation has been solved in Japan by

standardizing the equipment (Yoshimi and Tokimatsu, 1983) where the "conepulley method" (cathead and rope) is used.

2.4 FIELD SPT PROCEDURES AND OPERATOR CHARACTERISTICS

Variation in procedures and operator characteristics were observed during this

study. Differences in the number of turns of rope around the cathead, the

speed in which the blows are made and the inability of the operator to achieve

the 30 in (76 cm) fall height were observed. In addition, there is a lack of

conformity in the use of SPT sampler liners during the test, as described below.

From the ASFE survey, 83 of 116 stated that they stipulate the number of turns

of rope around the cathead that the driller or operator may use. When asked

how many turns of rope were ordinarily used, ninety respondents replied as follows

Using 1 turn only: 2

Using 1 & 2 turns only: 7 Using 2 turns only: 68

Using 2 & 3 turns only: 5 Using 3 turns only: 8.

From this breakdown it appears that two turns of rope around the cathead is the

most popular practice.

When the engineer was asked if the driller was allowed to switch the number of

turns during the day, 19 said yes; 84 said no; 4 did not know one way or another; and 9 did not reply.

The rate and manner in which operators perform the test varies substantially.

Some operators will use a continuous motion achieving a rate of 50 + 10 blows

per minute, the "rhythmic" procedure, while others will use a "hold-drop"

procedure at an approximate rate, from 15 to 25 blows per minute. In the hold

drop procedure, the operator slowly raises the hammmer (by rope) until the

16
30 in (76 cm) mark is visible. Then, the operator quickly releases the rope

into the cathead, completing the blow.

Figure 2.4 illustrates how the fall height varied with each blow for three

experienced operators. Operator 1 performs the test using a continuous motion

(figure 2.4a, b) while operator 2 attempts the 30 in (76 cm) fall using the

hold-drop method (figure 2.4c). Note how the fall height with each blow varied

for operator 1. Operator 2, who was experienced but used the hold-drop method,

appears to have held the rope at the same locations during sampler penetration

and changing his position at the four times when the fall height was below the

gradual increasing trend (for example, at blows 4, 12, 14, and 17). Figure

2.4d, shows a third experienced operator who used a cathead and rope. There is

considerable variability in the fall height produced by operators 1 and 3.

There also seems to be a tendency for the average produced in any one run by

the same operator to differ from the standard 30 in (76 cm) fall height. These

examples plus those published elsewhere (Kovacs, et al., 1981) illustrate the

wide variation in fall height that occurs with experienced drillers when

performing the SPT.

Figure 2.4 also shows some tendency for a warm up effort during the performance

of the SPT, with fall height and therefore energy tending to increase with

additional blows. Figure 2.4c shows this trend most strongly. The blows

needed for 0 to 6 in (0 to 150 mm) penetration allow the operator to establish

his rhythm and are not counted to establish the N value or "blowcount". However, all the average energy ratios (later discussed) reported herein are comprised from all the blows and not the last 12 in (300 mm) of the prescribed

18 in (450 mm) drive. Perhaps this aspect must be addressed in future

reporting of energy ratios (ER^).

A very important detail regarding the practice of performing the SPT involves

the use of liners inside the SPT sampler. Present construction of the SPT

sampler, according to ASTM D 1586, requires that the inside diameter of the

cutting shoe be 1 3/8 in (35 mm) and the inside diameter of the barrel be

1 1/2 in (38 mm). Schmertmann (1979) points out that most drillers do not use

liners with the 1 3/8 in (35 mm) inside diameter SPT sampler shoe. This extra

space reserved for a liner allows for reduced frictional resistance during

sampling and may account for a 30 percent reduction in N value for insensitive

clays and a 10 percent reduction for sands (Schmertmann, 1978). According to

the ASFE survey, 60 respondents stated that they use the 16 gauge liner while

43 do not; seven respondents did not know and there were five "no responses."

However, W.L. Acker estimates that 5 percent or less obtain the liners at the

time of purchasing SPT split barrel samplers. Further, he estimates that 5 percent or less purchase of the ASTM (D 1586) SPT sampler shoe (personal com- munication, 1983). Attention to this detail is very important, and it is

recommended that a decision be made which practice to use, and subsequently one

or the other practice be used consistently.

SPT standards in Japan (Japanese Standards Association, 1976) and the United

Kingdom (British Standards Institution, 1975) do not allow a space for liners;

the inside diameter of the barrel remains identical to the cutting shoe at

1 3/8 in (35 mm)

.

17
MEASURED

FALL

HEIGHT

|in|

MEASURED

FALL

HEIGHT

(inj

33 r

32 -

31 -

30

29

28

27

26

10 20

BLOW NUMBER

30

SERIES 120

EXPERIENCED OPERATOR 1 (first time ever measured]

18 in. (46 cm] PENETRATION

37 BLOWS/MINUTE

NATURAL RHYTHM

a.

32 r

31

30

29

28

27

26

SERIES 130

EXPERIENCED OPERATOR 1 (blow 19 missed]

40 BLOWS/MINUTE

NATURAL RHYTHM

b.

25

24

23

10 20 30

BLOW NUMBER

Figure 2.4a Typical results of fall-height vs. blow number from experienced

drill rig operators performing the SPT - (a), (b)

,

and (d) usual

rhythmic method; (c), hold-drop method

18
MEASURED

FALL

HEIGHT

[in)

MEASURED

FALL

HEIGHT

(in)

35

34

33

32

31

30

• • •

«

• •

29 -

28 -

SERIES 102

EXPERIENCED OPERATOR 2

(first time ever tested)

26 BLOWS/MINUTE

HOLD DROP METHOD

c.

27

j I— 10 20

BLOW NUMBER

j

30

33 i32 -

31

30

29

• • •

• • • • • • •

• •

28

10 20

BLOW NUMBER

30

SERIES 83

EXPERIENCED OPERATOR 3

38 BLOWS/MINUTE

d.

Figure 2.4b Typical results of fall-height vs. blow number from experienced

drill rig operators performing the SPT - (a), (b)

,

and (d) usual

rhythmic method; (c), hold-drop method

19
3. CURRENT METHODS OF ENERGY MEASUREMENT

Presently (1983), NBS measures the SPT energy at three points in the SPT system:

The potential energy of the hammer is measured via the fall height; the kinetic

energy of the hammer is measured via the hammer impact velocity; the energy

passing through the drill rod is measured via the force in the drill rods.

These energy measurements are now described.

3.1

POTENTIAL ENERGY OF HAMMER BEFORE RELEASE

The potential energy of the hammer is calculated from the measured fall height.

The measurement of the fall height is accomplished together with the measurement of the hammer impact velocity as described by Kovacs et al., (1981). The

accuracy of this measurement is to the nearest 1/8 in (3 mm).

3.2

KINETIC ENERGY JUST BEFORE IMPACT

The kinetic energy just before impact is determined by measuring the fall-time

relationship of the hammer during its fall. From this relationship, the fall

height and the instantaneous velocity just before impact are obtained, from

which the kinetic energy is computed. Detailed procedures to accomplish the

velocity measurement for the three types of hammers mentioned in section 2.2

has been described by Kovacs et al., (1981), and by Goble and Ruchti (1981)

for safety hammers. We denote this energy as Ev and the corresponding energy

ratio for velocity, ERV , which is defined as the ratio of Ev divided by mg of

the hammer times the measured fall height. A second measure of the energy

ratio for velocity is ER

v

, which is defined as Ev divided by 4200 inch-pounds.

This latter energy ratio is referenced to the prescribed energy of the 140 lb

(63.5 kg) hammer falling 30 in (760 mm). The accuracy of the hammer impact

velocity measurement is as good as the accuracy of the time and the distance

measurements involved and there is no ambiguity in the interpretation of its

results. The next section describes the measurement of the energy passing

through the drill rods. The percentage of the energy just before impact that

is measured in the rods is further discussed in section 3.4.2.

3.3

ENERGY PASSING THROUGH THE DRILL ROD

3.3.1 Theory

A useful summary of the one-dimensional wave theory as applied to drill rods

is provided by Schmertmann and Palacios (1979) with further details given

Palacios (1977) and is discussed further by Hall (1982). For convenience to

the reader, a short summary is provided below. The energy transmitted from

the hammer to the drill rods in the form of the first compressive stress wave

is given in terms of stress as

t

E-£ = ^ dt (3.1)

°

and in terms of force as

20
cAE

1

(3.2) E

i "

/ dt = A/Ed/ dt

where E-^A

cE

P Fi

t

energy passing through the drill rod at the point of measurement

drill rod cross-sectional area compressive wave velocity in the steel drill rod

Young's modulus of the steel drill rod, above and below the load

cell mass density of the steel drill rod

incident compressive force, F(t) measured in the drill rods

the time from impact until the return of the reflected tensile

stress wave to the hammer/anvil interface.

Once the force-time relationship is known, the energy in the stress wave in the

drill rod may be computed using equation 3.2.

3.3.2 Application of Theory

The force-time relationship is measured by a load cell placed at least ten

drill rod diameters below the anvil to be a sufficient distance from a discontinuity. The theory assumes that the stress in the drill rod above and

below the load cell is F/A, where F is the measured force in the load cell and

A is the cross-sectional area of the drill rod. However, because of combinations of couplings, reducers, and upset wall and/or parallel wall drill rods,

the theory is seldom completely satisfied in practice. Also, the load cell

introduces a discontinuity in the drill stem cross-sectional area. Several

corrections to equation 3.2 are required to account for departures from theory.

They are:

a) K]_, a correction to account for the load cell not being at the point

of impact,

b) K2 , a correction to account for drill rod length, and

c) Kc , a correction which accounts for deviations from assumed rod

characteristics. One deviation which was observed is that the actual

compressive stress wave velocity in the steel drill rod tends to be

less than the theoretical velocity.

Since the point of impact is some distance, Afc, from the load cell, a correction

factor must be included (revised, from Hall, 1982).

1 - exp [-4ApA/M^]

1 - exp [-4Ap (£-A£)/M^]

(3.3)

where = a correction to account for the load cell not being at the point of

impact

l = distance from the point of hammer impact to the bottom of the

sampler

Ail = distance from the point of impact to the location where F^ is

measured

21
Mh = mass of the hammer

exp = base of the natural logarithm raised to some power.

The second correction, K2 , involves the total length of the rod and its effect

on the duration of the first compressive wave pulse (Hall, 1982). If the total

length of the rod is "short”, then the compressive wave returns prematurely to

limit the energy being "pumped in" by the hammer. The second correction is

necessary to compare drill rods at the same (infinite) length.

K2 = 1

, (3.4)

1 - exp [-4Ap &/M^]

where K2 = a correction to account for drill rod length

The last correction factor, , was suggested by Schmertmann (Private

Communication 1982) and involves a small correction to account for the fact

that the time required for a tensile stress wave to return from the end of the

sampler to the point of force measurement is longer than the theoretical time

required. Even though this phenomenon has not been fully explained at this

time, it is tentatively attributed to a deviation from the assumed elastic rod

properties and perhaps rod coupling effects and the calculated energy is

modified accordingly.

Thus

Kr = m

(E/p)T72

(3.5)

where Kc = a correction to account for the actual compressive wave velocity in

the steel rods and couplings.

cm = compressive wave velocity as calculated from the measured time of

return of a reflected wave.

When these corrections are applied, equation 3.2 becomes:

Kl K2Kc S 2 E

± =

1 j [F(t)] Z dt (3.6)

A /Ep 0

and E = 29.7 x 10^ psi, (0.20 TPa)

p = 7.24 x 10“^ lb-secVin^ (7.85 Mg/m^)

While the accuracy of the measurements of the potential energy and kinetic

energy is only limited by the accuracy of the distance and time measurements

involved, the measurement of E^ depends on theoretical assumptions and idealizations and at this time it has not been validated by an independent energy

measurement. However, the measurement is at a point which is below the anvil

and closer to the sampler and thus accounts for energy losses which occur after the hammer impact, and therefore conveys important and necessary information on hammer and anvil characteristics. The data on E^ obtained in this

study appear reasonable when compared to the E v data, and it is also reasonable

22
to assume that for the same drill rod size and configuration a valid comparison

of different hammer and anvil configurations can be made. The data in this

report will be re-evaluated by NBS if and when independent calibration data for

the measurement of E^ become available.

There are several methods by which equation 3.6 may be readily evaluated.

These methods are described below.

3. 3. 2.1 Digital Processing Oscilloscope

The digital processing oscilloscope (DPO) is a real time oscilloscope that

converts the analog force-time history into digital form at an adjustable,

desired rate. The entire time history may be displayed for viewing. The

output from the load cell is recorded in analog form in the field on tape at

60 in/s (1.54 m/s) and later played back at 1 7/8 in/s (48 mm/s) providing a time expansion of 32.00. The tape is played back into the DPO and a digital

force-time history is obtained. The DPO is programmable and performs the

integration of equation 3.6 automatically once the integration limits are set

manually. The details of this procedure have been discussed elsewhere (Kovacs

et al., 1981).

3. 3. 2. 2 Other Equipment

Hall (1982) documents the use of an electronic analog instrument that can be

utilized in the field to obtain the energy passing through the drill rod, E^,

in real time after each blow of the SPT hammer. Figure 3.1 presents a block

diagram of the key elements of this device described as the SPT Energy Calibrator or just Calibrator .-/ A photograph of the device is shown in figure 3.2

with three cables attached. The left most cable connects the Calibrator to the

load cell mounted in the drill stem. The remaining two cables, labeled

"trigger" and "force” in figure 3.2, connect the Calibrator to a field oscilloscope or a tape recorder. The trigger cable output allows the integration time

of the Calibrator (performing equation 3.2) to be monitored. On the other hand,

the force cable output allows the force-time history to be monitored. A cable

from the force jack to the tape recorder allows a permanent analog record to be

made that can later be reproduced on the DPO.

The Calibrator used in this study was modified in several ways to maximize its use.

a. The internal circuitry has been altered to allow two different load

cells to be used interchangeably with the flip of a switch instead of

going through an elaborate internal instrument calibration;

"Certain commerical equipment, instruments, or materials are identified in

this report to specify adequately the experimental procedure. Such identification does not imply recommendation or endorsement by the National Bureau

of Standards, nor does it imply that the materials or equipment identified

are necessarily the best available for the purpose."

23
HAMMER

IMPACT

24

Figure

3.1

Schematic

showing

the

key

elements

of

an

SPT

energy

calibration

instrument

(modified

after

Hall,

1982)
Figure

3.2

Photograph

of

SPT

energy

calibrator
b. A new circuit was added to allow a new, higher capacity piezoelectric

load cell to be used for field use.

c. A new circuit was added to allow the use of a tape recorded F(t)

signal as input to the Calibrator to check actual field readings.

d. Provision to use an external (12 volt) battery as a backup power

source.

To use this instrument, a three-step field calibration is necessary prior to

each field test: 1) the first step involves setting zero load on the load cell

when the 140 lb (63.5 kg) hammer rests on the anvil prior to testing; 2) the

second step introduces an electronic signal equivalent to a 20,000 lb

(8.9 x 104 N) load into the Calibrator for use in step 3; and 3) the third step

involves adjusting a pot until the required calibration number shown in table

3.1 for the rod size used appears on the Calibrator display. The display on the face of the instrument shows the output from the Calibrator's integration

of equation 3.2, using a 20,000 lb (8.9 x 10%) square wave as the force history

and an integration time of t = 8.192 ms, divided by the standard SPT energy of

4200 in-lbs (475 J), E*. For example, for AW (parallel wall) rod, the Calibrator display number is 452 using equation 3.7. When the pot is adjusted so that

this number appears on the display, one can be assured that the electronic

device is working properly.

452AW

" 100 c _/

t [F (t )

]

2 dt

AE °

, 4200 in-lbs (3.7)

It should be pointed out that the Calibrator is programmed for using a theoretical value of c = 16878 ft/s (5144 m/s). There is a need to correct

equation 3.3 for the experimental value of c, according to equation 3.5,

including corrections Kq and K£.

3.4 RESULTS OF ENERGY MEASUREMENT STUDIES

3.4.1 General

The tables and figures in this section provide information on the energy

delivered by the various drill rig systems as measured by the kinetic energy

at impact and the energy passing through the drill rod. Following introductory

comments about typical energy output from the hammer kinetic energy and the

force time approaches, a detailed discussion of the data is provided.

Typical results of the kinetic energy just before impact have been presented by

Kovacs et al. (1981). This report primarily presents data on Eq , the energy

passing through the drill rods. The kinetic energy at impact is discussed as required to document the differences between the kinetic energy just before

impact and the energy in the drill rod.

26
cr

pi

Table 3.1 Tabulation of Calibrator Display Numbers for Drill Rod Areas

Calibrator

Display No. Rod Size

Area

(in2

) (1) (2) (3)

493 A 1.079

452 AW 1.177

413 N 1.288

[466] [BW] [1.141]

235 NWa 2.264

[439] [NWb

] [1.212]

Parallel wall rod

Upset wall rod

Numbers in brackets do not appear on Calibrator selection switch area.

27
Typical measurements of the force-time history for safety and donut hammers are shown in figures 3.3a and 3.3b taken from four different test series. In these

four cases, NW upset wall drill rod of the same length was used. In each of

these four blows, the energy ratio for velocity, ER$, was different and

varied from 0.63 to 0.80. The energy ratios for were evaluated by the DPO

and the Calibrator and were generally within two or three percentage points of

each other. An important feature of the force-time history shown in figure 3.3

is the location where the force curve crosses zero force and becomes negative.

The time, tm , at which the crossover occurs is the time when the returning

tensile wave cancels the downward compressive wave. This time may be computed

theoretically by dividing two times the drill rod length, (from the load cell

to the bottom of the sampler) by the theoretical compressive wave velocity, c,

of the steel drill rod. Note that the measured compressive wave velocity

varied from 14,400 ft/s (4389 m/s) to near the theoretical value of 16,878 ft/s

(5144 m/s). From these examples and the figures that will be presented subsequently, it should be apparent that each individual blow is different in small

ways from any other, just as the fall height varies substantially from one blow

to another (see figure 2.4).

For some of the test series performed, deviations from the typical force-time

relationships shown in figures 3.3a and 3.3b were observed. The deviations

observed can be classified into two groups.

a) Group 1 - Those force-time histories that contain electronic glitches

as shown in figures 3.4a and 3.4b.

b) Group 2 - Those force-time histories that contain a significant

returning compressive wave (figure 3.5) without the usual initial

tensile wave return (figure 3.3a, b).

Electronic shorts in the load cell wires were the cause of the deviations

observed in Group 1. Typically, the load cells take substantial punishment

with peak forces averaging 20 to 25 kips (89 to 111 kN) for each blow. Because

the load cell serves as input to the DPO and the Calibrator, both instruments

can experience the same problem.

The presence of glitches can cause the Calibrator to prematurely cut off the

integration time prior to the actual crossover point from compressive to^

tensile stress, resulting in a reduced value of energy ratio, ER^ = E^/E (see

figures 3.4a and 3.4b).

For this study, where glitches occurred, the DPO was used to bypass the glitches

and approximately compute the energy in the drill rods for the correct time

interval.

The deviations in Group 2 can be explained by referring to Timoshenko (1934).

When a prismatic bar is struck, in the case of a free end (drill) rod, a com- pressive wave is reflected as a similar tension wave. In the case of a fixed

end (drill) rod, a compressive wave is reflected as a similar compressive

wave (Timoshenko, 1934). Under certain SPT driving conditions which have not

been well defined thus far, except as "hard driving," compressive wave returns

have been observed randomly within a series of blows.

28
sdW - 33M0J

So

•u

a)

<4-4 CO

CO

4-4O

CO

CD •H

I-i O

•u

CO JZ

<vB

•H

4JIoo

4-4a

so

4-1

4-1o

CO

<d co .h p

a. a; X co w js

cO CO• CO

a>u3

bO

•H

ftt

29

and

donut

hammers
•U

(U cm

Cd0]

<4-1 o

CDa> •Huo

•U

CD

a)S

•H

MlI(Vouo

cm

cdoa

4J CMo

CD<Da.0

cdxw

CDM

a)

cd x:

-Qcn

co

<u3

bO

•m

Cm

sd(>| - 33a0d

30

and

donut

hammers
Series

59,

blow

9,

safety

hammer,

C

=

33.4

ft.

ER

i

=

30

calibrator,

t

=

1.2

ms

ER

j

=

29

integration,

t

=

1.2

ms

03

sd(H - 33H0J

31

Figure

3.4a

Two

examples

of

electronic

shorting

of

load

cells

during

impact
Series

55,

blow

10,

safety

hammer,

l'

-

13.4

ft.

sdi4 - aoaod

32

Figure

3.4b

Two

examples

of

electronic

shorting

of

load

cells

during

impact
54

%

</> = E

.2 io

:E w $2

a>

sd!M - 3380J

33

Figure

3.5

Illustration

of

compressive

wave

return

force-time

history

and

trigger

(duration)

time
Figure 3.5 illustrates a blow where such a compressive wave returned from the

SPT sampler which caused the Calibrator to integrate the force-time curve well

above the computed value of 2 V / c. (8.92 ms assuming C = 16,500 ft/s).2/ Similar compressive wave returns have been observed in pile driving (Gravare and

Hermansson, 1980). A value of ER^ = 0.90 was determined from the Calibrator

with an integration time (based on the trigger measurement) of 13.5 ms. When

the integration is performed on the DPO with an integration time of 13.2 ms,

ER-l = 0.88, showing close agreement to the Calibrator value. Naturally, the

DPO operator would recognize what was occurring and choose an integration time

of 9.4 ms, close to the computed value of 2V/c. However, the first crossover

point of the force-time curve occurs at 8.3 ms for this blow and the resulting

ER-l = .53, or almost one-half of the Calibrator reading. The writers have

observed many instances where the Calibrator reading would sometimes double

randomly, during a series of blows. A solution to this problem is to monitor

the integration (trigger duration) time of the Calibrator. Blows that have

integration times that are inconsistent with the computed value of 2 V/c.

should be discarded. This measurement may be made either by a commercially

available digital timer that attaches directly to the trigger jack of the Calibrator or by means of attaching a storage oscilloscope to the oscilloscope jack

of the Calibrator. Under these circumstances, it may be necessary for two

individuals to take data depending on experience: one who reads the Calibrator

data (using a hand held tape recorder); the second observing the blow on the

scope or reading (and verbally recording) the digital timer.

3.4.2 Results of Energy Measurements

Field test data from six drill rigs and eleven operators are presented, and

field test results and implications are discussed. Table 3.2 summarizes the

test Series and test conditions. A series is defined as a collection of SPT

hammer blows performed under a given set of conditions; e.g., rig, hammer,

operator, depth, rod, etc. In many of the cases studied, the fall height, H,

and kinetic energy just before impact, Ev , have been obtained along with the

energy transmitted through the drill rods, E^, calculated using the DPO.

For Series 79 through 130, SPT Calibrator data are also presented.

When the measured energies are compared with the standard potential energy

[4200 in-lbf (475J)], a useful parameter, the energy ratio, is defined for the

purpose of discussing test results. The ratio of kinetic energy just before

impact, Ev , to t^e standard potential energy is defined as the energy ratio

for velocity, ER

v

«

E— x 100, percent (3.8)

U The Calibrator is programmed to cease integration when the force becomes

zero upon the return of the reflected tensile stress wave. When a compressive stress wave is returned, the Calibrator will not cease integration at

2 V/c and thus overestimate the energy passing through the rods.

34
Table 3.2 Tabulation of Test Series Performed and Test Conditions

1

1jite Series Drill Rig Hammers3 Personnel Test Procedures Other

:n (2) (2) (3) (5) (6) (7)

A 48-61 CME 45 D, S 1 experienced

operator

2 turns (of rope

around cathead)

Depth varied,

AW rod

B 79-101 Mobile

B-61

S, D 4 experienced and

3 inexperienced

operators

1, 2, & 3 turns;

free fall and

hold drop tests

Constant depth,

NW rod

C 102-109 Mobile

B-61

S, D 3 experienced

operators

1, 2 & 3 turns;

free fall tests

Constant depth,

BW rod

i D 110-112 Longyear

AC-150

S 2 experienced

operators

2 turns constant depth,

BW rod

( E 113-119 CME 75 S 3 experienced

operators

1, 2, & 3 turns;

free fall tests

Constant depth,

BW rod

i F

1 120-130 Failing

1500

S 3 experienced

operators

1, 2, & 3 turns;

free fall tests

constant depth,

BW rod

1 D denotes donut (type) hammer and S denotes safety (type) hammer.
The ratio of the kinetic energy transmitted through the drill rod, E^, divided

by the standard potential energy is defined as the energy ratio for F(t), ER^.

E

i ERf = — x 100, percent (3.9) E*

In subsequent paragraphs, the energy ratios defined above will be used to:

* a) Establish the efficiency of the hammer delivery system, ERV

«

b) Compare the results between the energy passing through the drill rod,

ER^ as measured by the DPO and the SPT Calibrator.

c) Study the relative efficiency of the various hammer-anvil systems in

transmitting the kinetic energy just before impact to the drill rod.

d) Study the effects of personnel (operators), equipment (drill rig,

hammer, drill rod) and procedures (fall height, rate of blow count,

depth) on the energy transmitted through the drill rod, ER^

.

A summary of results and test variables for Series 48 through 130 is presented

in table 3.3. Individual field data of ER^ , percent from the SPT Calibrator are presented in appendix tables A-l through A-7 while tabulation of individual fall

heights for some series are given in appendix tables B-l through B-4.

The average energy ratio for velocity, ER

v , from columns 13 in this table for

all the drillers using two turns of rope around the cathead is approximately 73

percent, with a standard deviation of 10.2 percent and a range from 50 to 90

percent

.

The energy ratio ER^ was determined using the DPO and the SPT Calibrator.

Individual data points for selected blows for Series 48 through 130 (excluding

free-fall test data) are presented in table 3.4 where energy ratios from the

Calibrator and those computed using the DPO are listed. To facilitate the

comparison between the two methods, figure 3.6 has been drawn. Data points

that had integration times greater than 2 Vic were not used and are identified

by the superscript "d" on table 3.4.2/ The equation of the line on figure 3.6

based on a linear regression analysis is:

ERi Calib “ 1*076 ER^ DP0 - 3.37 (3.10)

where ER-[ Calib = ERi f rom the SPT Calibrator,

ERi DPO = ERi computed using the DPO,

and has a correlation coefficient of 0.976. The least square's fit line is

very close to the one-to-one equality line in the range of interest (0.4 to

0.7).

The Energy Transfer Ratio, ETR, has been defined (Kovacs et al., 1981) as:

36
Table 3.3 Tabulation of Results and Testing Variables Using Two Turns of Rope Around the Cathead

Calibrator DPO

No . of Avg. ERi No. of Hammer Data Fall Fall Hgt Avg Stnd ERi Data Avg Avg Test

Type Rig Series Type Operator Points Height Stnd Dev. ERi Dev. CV Points ERi ER$ AX. i Rate

(in) (in) (%) (%) (%) (%) (%) (Ft) (Ft) (b/min)

(1) (2) (3) (4) (5) (6 (7) (8) (9) (10) (ID (12) (13) (14) (15) (16)

CME 45 48 D A 5 33.1 0.6 5 30 90 2.9 21.3

49 D A 5 32.5 0.5 - - - 5 38 90 2.9 26.3 - 50 D A - - - - - - 5 36 - 2.9 31.3 -

51 D A - - - - - - 4 34 90 2.9 36.3 -

52 D A 1 31.8 - - - - 5 33 88 2.9 41.3 -

54 S A 5 29.0 1.2 - - - 5 33 67 5.2 13.6 -

55 S A 5 31.8 0.8 - - - 5 38 77 5.2 18.6 -

56 S A 5 34.0 0.8 - - 9 5 42 82 5.2 23.6 -

57 S A 5 33.9 0.5 40 0 0 5 41 86 5.2 28.6 -

58 S A 5 33.5 1.2 - - - 5 42 83 5.2 33.6 -

59 S A 5 34.3 0.6 - - - 5 43 83 5.2 38.6 -

60 S A 5 34.3 1.4 - - - 5 42 88 5.2 43.6 -

61 S A 5 34.8 0.9 — “ 5 40 88 5.2 48.6

Mobile B-61 79 S B 30 _ _ 47.2 3.4 7.2 4 43 _ 7.3 45.8 41 80 S B 22 - - 51.8 2.3 4.3 4 52 - 7.3 47.8 47

81 S C 21 a a 54.5 6.7 12.2 a a a 7.3 50.8 54

82 D C 15 31.4 1.0 43.1 6.1 14.2 5 39 73 1.3 44.8 34

83 S C 19 30.8 1.0 55.6 5.8 10.5 3 56 70 7.3 50.8 38

84 S D 22 29.8 1.0 53.6 4.9 9.0 3 58 71 7.3 52.8 30

85 D D 21 30.1 0.5 41.4 5.2 12.6 4 47 71 1.3 46.8 32

86 D D 22 a a 59.8 9.6 16.1 a a a 1.3 46.8 35

87 D D 20 a a 47.4 6.1 12.9 a a a 3.5 49.0 33

88 S D 20 a a 62.8 4.5 7.2 a a a 7.3 52.8 39

89 S D 20 a a 52.8 6.1 11.5 a a a 7.3 52.8 36 90 S E 25 a a 58.1 6.5 11.1 a a a 7.3 52.8 39

91 S E 25 a a 68.0 6.1 9.6 a a a 7.3 52.8 43

92 S E 20 30.3 0.9 46.9 7.7 16.4 3 53 67 7.3 54.8 39

93 D E 47 a a 57.5 8.4 14.6 a a a 3.3 50.8 41

94 D E 21 30.3 0.8 55.1 6.3 11.4 3 53 71 3.3 50.8 43

Mobile B-61 95 S C 52 _ _ 45.8 2.3 5.0 4 48 _ 7.3 47.3 40

96 S C 20 a a 45.1 1.9 4.3 a a a 7.3 47.3 41

97 S E 20 a a 46.7 1.9 4.0 a a a 7.3 47.3 39

98 S E 20 29.2 0.5 44.7 2.0 4.5 3 49 59 7.3 47.3 41

99 S2 C 20 a a 47.4 2.3 4.8 a a a 5.7 45.7 40 100.1 S2 E 20 a a 49.1 1.7 3.4 a a a 5.7 45.7 41 100.2 S2 C ll b a a 55.5 1.1 2.0 a a a 5.7 45.7 11 100.3 S2 C 14c a a 32.8 2.5 7.6 a a a 5.7 45.7 22 100.4 S2 C 14 a a 49.7 1.8 3.7 a a a 5.7 45.7 29 100.5 S2 F 15 a a 50.9 1.0 2.0 a a a 5.7 45.7 -

100.6 S2 G 1 a a 45 - - a a a 5.7 45.7 - 100.7 S2 G l b a a 48 - - a a a 5.7 45.7 -

100.8 S2 G l c a a 31 - - a a a 5.7 45.7 -

100.9 S2 G 1 a a 43 - - a a a 5.7 45.7 - 100.10 S2 H 10 a a 50.1 1.8 3.6 a a a 5.7 45.7 ** _

37
Table 3.3 Tabulation of Results and Testing Variables Using Two Turns of Rope Around the Cathead

(Continued)

Calibrator DP0 j No. of Avg. ER± No . of Hammer Data Fall Fall Hgt Avg Stnd ERi Data Avg Avg Test Type Rig Series Type Operator Points Height Stnd Dev. ER± Dev. CV Points ER-l ER* AZ i Rate

(in) (in) (%) (%) (%) (%) (%) (Ft) (Ft) (b/min)

(1) (2) (3) (4) (5) (6 (7) (8) (9) (10) (11) (12) (13) (14) (15) (16)

Mobile B-61 102 S I 17 32.3 2.4 60 6.0 10.0 15 59 68 6.0 44.6 26 103 S J 21 30.3 0.4 49 4.0 8.2 4 47 57 6.0 44.6 19 104 s K 22 30.8 0.3 54 5.1 9.5 4 51 65 6.0 44.6 17

I 105 s I 18d 31.9 2.2 60 5.4 8.9 4 57 70 6.0 46.6 17 106A s I 9C 33.6 0.7 43 5.5 12.8 4C 43 46 6.0 46.6 17 106B s I 10b 33.8 0.9 72 7.2 10.0 4b 67 76 6.0 46.6 17 108 D I 20 28.4 0.3 63 6.1 9.7 4 58 73 1.7 42.3 14 109 D I 19 28.1 0.4 65 12.0 18.3 4 62 75 1.7 45.3 15

Longyear HC 150 110 S K 25 69 3.9 5.6 a a a 5.0 78.6 15 111 S K 20 29.8 0.4 72 2.4 3.3 4 70 71 5.0 78.6 20 112 S J 20 29.6 0.1 85 15.3 18.0 4 48 50 5.0 78.6 13

1

| CME 75 113 S J 24 29.6 0.1 67 7.5 11.3 4 66 69 5.9 89.5 13 114A S J 5C 30.0 0.7 56 12.4 22.2 5C 55 57 5.9 89.5 11 114B S J 6b 29.8 0.7 79 2.1 2.7 4b 78 79 5.9 89.5 n j 115 S K 19 30.0 0.4 74 5.4 7.3 4 69 75 5.9 89.5 20

117 S I 23 29.9 0.1 79 6.2 7.8 5 72 70 5.9 91.5 12 119 S J 17 e 29.7 0.3 76 4.1 5.4 4 73 76 5.9 91.5 14

Failing 1500 120 S L 14 28.4 2.0 58 6.7 11.7 5 53 57 4.0 46.5 37 121 S L 20 29.6 1.0 68 3.4 5.1 4 58 68 4.0 46.5 36 122 S M 20 30.0 1.0 74 2.6 3.5 4 68 70 4.0 46.5 29 123 s N 10 30.3 1.0 74 3.4 4.6 5 69 70 4.0 46.5 30 127A s L 10b 29.7 1.2 75 5.5 7.3 4b 66 73 4.0 46.5 21 127B s L 10 29.9 1.3 64 3.4 5.4 4 53 61 4.0 46.5 40 127C s L 10c 29.2 2.3 55 3.7 6.7 4

C 44 44 4.0 46.5 21 128A s L 10b 30.0 0.5 81 2.6 3.2 4b 66 76 4.0 48.5 15 128B s L 10 28.3 1.9 74 4.7 6.3 4 62 63 4.0 48.5 42 128C s L 7 C 29.8 1.2 57 4.0 7.1 4

C 42 47 4.0 48.5 40 130 s L 30 28.5 1.9 81 6.3 7.8 6 58 64 4.0 48.5 40

1 ! NOTES: a.

b.

c

.

d.

e

Tape recorder not used. Only data on ER^ from Calibrator obtained.

1 1/4 turns of rope around the cathead.

31/4 turns of rope around the cathead. A 2 ft section of BW parallel wall rod was added below the load cell, above 35.2 ft of BW upset wall

drill rod for Series 105, and added above 40.0 ft of drill rod for Series 128. A 2 ft section of BW parallel wall rod was inserted at 40 ft in the 80 ft upset wall drill rod.

1 ft = 305 mm.

38
Table 3.4 Summary of Energy Data from Individual Blows

Series Blow

No. Hammer

Type

ERi

Calib.

ER-l DPO ER$ ETR

(5/6) Series

Blow

No. HammerType ER± Calib.

ER-t DPO ER$ ETR

(5/6)

(1) (2) (3) (4) (5) (6) (7) (1) (2) (3) (4) (5) (6) (7)

48 9 D 23 81 28 56 8 S 43 89 48

10 28 85 33 13 42 77 55

11 34 93 37 15 43 87 49

12 34 93 37 16 40 83 48

13 32 100 32 18 42 72 58

49 15 D 38 86 44 57 1 S 40 42 82 51

16 37 89 42 2 40 40 84 48

17 36 95 38 3 40 43 86 50

18 35 89 39 7 40 42 88 48

19 43 92 47 9 — 39 88 44

50 1 D 35 — — 58 6 s 38 80 48

2 36 — — 8 42 80 53

3 37 — — 9 44 85 52

4 34 — — 10 42 85 49

5 36 — — 11 44 86 51

51 8 D 34 93 37 59 8 s 42 84 50

9 34 88 39 9 44 88 50

13 29 93 31 10 42 86 49

17 38 87 44 11 45 83 54

12 40 72 56

52 11 D 32 85 38 60 3 s 40 80 50

12 32 93 34 16 42 91 46

14 34 91 37 17 42 84 50

15 32 87 37 18 44 91 48

16 33 84 39 19 43 93 46

54 20 S 30 65 46 61 8 s 33 84 39

21 35 63 56 9 39 84 45

23 31 65 48 10 42 93 45

24 33 70 47 11 43 89 48

26 35 74 47 12 41 89 46

55 6 S 37 80 46 79 9 s 45 42 — —

7 39 79 49 13 48 45 — —

8 38 77 49 22 35 34 — —

9 36 70 51 30 48 50 — —

10 38 77 49

i

totes: After the data was collected for Series 48 through 61, it was found that the F(t) curves contained glitches,

similar to figure 3.4 thus, the Calibrator ER.^ data should not be used. The F(t) cures were adjusted using

the DPO to remove the glitch and replace it with a smooth line approximation. Series 57 did not contain

any glitches. Only column 7 should be used in this table for Series 48 through 61. Data in column 5 contain corrections and K£

1

39
1

I

I

Table 3.4 Continued

Series

Blow

No. HammerType

ERi

Calib.

ERi DPO ER$ ETR

(5/6) Series

Blow

No. Hammer

Type ERt Calib.

ERj DPO ER$ .

ETR

(5/6)

(1) (2) (3) (4) (5) (6) (7) (1) (2) (3) (4) (5) (6) (7)

80 3 S 51 53 102 1 S 61 58 74 78

8 46 46 — — 3 63 62 71 87 14 50 51 — — 4 64 61 64 95

22 54 57 — — 5 58 56 63 89

6 62 62 65 95 82 1 D 42 42 83 51 7 60 61 71 86

2 42 43 62 69 10 54 58 69 84

3 44 44 77 57 11 58 60 65 92

11 38 36 75 48 13 57 61 69 88

12 28 29 67 43 14 51 55 70 79 15 75? 72 69 104

83 6 S 55 58 68 85 17 56 56 71 79

7 55 57 71 80 18 63 64 67 96

13 54 55 69 80 19 53 57 65 104

20 71? 68 73 93 84 2 S 55 58 69 84

3 57 59 72 82 103 4 s 46 47 59 80

4 56 58 72 81 12 49 48 53 91

17 49 51 57 89 85 6 D 47 50 71 70 20 47 47 59 80

7 46 49 80 61

8 46 49 83 59 104 4 s 54 53 64 83 14 37 39 73 53 9 53 55 65 85

13 53 54 64 84

92 5 S 50 52 63 83 15 53 53 65 82

8 49 52 65 80

15 51 54 68 79 105 5 s 61 62 69 90

8 56 58 69 84

94 8 D 58 56 67 83 13 62 61 72 85

11 56 53 75 71 15 58 57 70 81 15 57 49 70 70 106 2b s 43 46 47 98 95 2 S 47 47 — — 3b 41 44 47 94

3 48 48 — — 4b 42 42 49 86

9 45 47 — — 10b 45 40 41 98 25 45 51 — — 12 a s 69 68 78 87 13a 77 70 74 95

98 2 S 48 51 62 82 16 a 70 66 72 92

6 46 50 59 85 18a 67 62 79 78

8 44 46 57 81

40
Table 3.4 Continued

Series

Blow

No. HammerType ER± Calib. ER± DPO ER$ ETR

(5/6) Series

Blow

No. HammerType

ER± Calib.

ERi DPO ER$ ETR

(5/6)

(1) (2) (3) (4) (5) (6) (7) (1) (2) (3) (4) (5) (6) (7)

107 l cS 87 88 91 99 116 l c

S 93 92 91 101

2

C 92 93 97 96 2C 94 90 93 97

4C 92 93 91 102 3

C 95 98 98 100

5C 92 90 98 92 5C 106 97 97 100

6 C 104e 65 62 105

108 13 D 63 60 79 76

15 61 64 71 90 117 2 s 66 66 65 102

18 60 56 70 80 3 70 69 64 106

19 62 57 72 79 5 70 67 65 103

7 83 80 78 103

109 3 D 71 65 71 92 8 84 80 72 111

8 61 60 71 85 9 83 84 73 115

14 66 66 71 93 10 81 79 74 107

15 67 63 90 70

118 2

c » f D 69 79 90 88 111 7 S 78 73 71 103

9 78 71 72 99 119 1 S 75 73 78 94

10 77 70 71 99 3 73 73 72 101

14 76 69 71 97 5 79 77 85 91

9 77 73 71 102

112 15 S 82 e

4\7 50 94

16 90e 53 54 98 120 3 S 58 55 58 95

18 85e 52 50 104 5 56 52 56 93

19 80e 41 47 87 10 57 53 57 93

14 62 59 56 105

113 6 S 67 69 69 100 18 58 56 56 100

10 65 65 66 98

11 70 69 72 96 121 4 S 68 64 67 96

12 70 68 70 97 10 67 64 65 100

11 67 55 66 83

114 6a

S 78 73 73 100 15 67 60 67 90

7 a 78 78 85 92

9 a 81 75 78 96 122 4 S 75 70 73 96

ll a 78 71 81 88 7 75 71 72 96

14 73 69 64 99 115 2 S 74 72 73 99 15 74 71 71 100

7 76 75 79 95

9 73 73 76 96 123 1 S 70 65 70 93

11 75 72 73 99 4 75 73 74 99

6 75 69 70 99

7 72 69 63 110

8 72 69 72 96

41
Table 3.4 Continued

Series

Blow

No. HammerType

ERi

Calib. ER1 DPO ER* ETR

(5/6) Series

Blow

No. Hammer

Type

ERi

Calib.

ER± DPO ER* ETR

(5/6)

(1) (2) (3) (4) (5) (6) (7) (1) (2) (3) (4) (5) (6) (7)

124 l c S 97 92 95 97 130 l d S 81 64 63 102

2C 97 93 97 96 4d 84 62 63 98

3

C 96 93 98 95 8

d 82 63 66 95

15d 81 63 63 100

125 l c D 96 81 97? 84? 21 d 78 59 62 95

2C 76 71 97 73 29d 80 63 63 100

3 C 96 95 91 104

126 l c Trip 97 93 93 100

127 13 S 63 62 53 117

17 62 60 62 97 19 66 61 65 94 20 65 61 64 95

4a 74 71 71 89

7 a 77 73 73 95

8a 75 74 74 91

9a 74 73 73 88

21b 59 47 47 83

23b 52 41 41 76 25b 56 43 43 86 26b » d 53 43 43 105?

128 lld S 73 69 69 100

13d 79 66 62 106

16d 72 63 57 111

19d 71 64 65 98

la 80 68 74 92

4

a 82 65 78 83

7a 82 66 77 86 10a 81 66 76 87 24b 58 35 43 81 25b 57 37 42 88 29b » d 62 44 50 88 30b » d 63 44 53 94

129 l c S 97 93 93 100

2C 100 98 91 108

3

C » d 106 97 93 104

Notes: All tests are two (nominal) turns of rope around the cathead unless stated otherwise.

a. One turn of rope around the cathead

b. Three turns of rope around the cathead

c. Free fall test, where hammer is string suspended 30 in (760 mm) above anvil, then cut

d. Integration time of Calibrator greater than computed value of 2 V /c

e. Spurious shape of F(t) curve

f. Fall height = 28.0 (71 cm)

42
•

Safety

hammer

(1

blow)

o

Safety

hammer

(2

blows)

Donut

hammer

(1

blow)

a

Donut

hammer

(2

blows]

a> LO OLo O> <4— CT> o

CO 00 cvT *7" cn LO k_

irT -1—

«

oo CO CM

CM -o OO

03 Q 00 oo

1 00 -4-> 00

O)

r- of +-» o

CO

03

-I-' ss

00

03 03

03

i_

o o 03 i-*- 03 r^* 03 oo

00

Eok_

LO

i CM

00

.top

M— oo

1 4—

03 »—U03

CO OO o

"co 00

o

Q_o

CSC O

03

CD 3 LU .s LU

6c

LU

dOlVdSIlVO !U3

43

Figure

3.6

Comparison

of

energy

ratios

using

the

SPT

Calibrator

and

the

Digital

Processing

Oscilloscope

(DPO)
(3.11)

Data from table 3.4, col. 7, together with other data taken from Kovacs et al.,

(1980) are shown in figure 3.7 for both donut and safety hammers. The

accuracy of the data presented is affected by two parameters:

1. Instances where a compressive stress wave is returned, and thus for

the calculator is overestimated. The instances account for most of

the data where ETR > 1, which is physically impossible.

2. Effect of the drill rod geometry and possibly other parameters on the

results of the calculated E^ which are not yet fully understood. The

validity of the caluclated E^ was not yet corroborated by an independent energy measurement.

Nevertheless the data provide an indication of the importance of considering

the effect of the hammer-anvil assembly on energy transmission. Figure 3.7

gives a clear indication that ETR is more variable for donut hammers than it is

for safety hammers, and that there are apparently significant differences

between different safety hammers. This latter observation is derived from a comparison of the three histograms for three different safety hammers at the

bottom of the figure. To what extent the difference between those histograms

is also attributable to the drill rod geometry (AW, NW, and BW rods were used)

has not been determined at the present time.

The drill rig, SPT equipment and procedures, and the dri^l rig operator have a combined effect on the magnitude of the energy ratios ER

v and ER^. The data

from table 3.3 can be used to separate these variables and evaluate the effects

of personnel, equipment, and procedures on the energy delivered in the test.

* In Series 48 through 52, operator A consistently delivered an ER of

approximately 90 percent (column 13), leading to reasonably consistent results

of ER^ of 30, 38, 36, 34, and 33 percent for the donut hammer (col. 12). In

these tests, the average fall height (where measured) was 32.5 in (826 mm),

which is higher than the standard. The same operator, when using the safety

hammer (usually used) produced smaller values of ERV

. The reason for this

performance can be further examined by calculating the ratio of Ev/mgH and

thereby filtering out the effects of fall height fluctuation. This ratio

varies from 0.815 to 0.830, with an average of 0.825 for the donut hammer; and

from 0.69 to 0.76, with an average of 0.74, for the safety hammer. Thus, the

safety hammer in this instance lost significantly more of the energy before

impact than the donut hammer. The resulting average values of ER-^ for the

safety hammer were 33, 38, 42, 41, 42, 43, 42, and 40 percent at depths measured from 5 to 40 ft (1.5 to 12 m) . It should be noted that the average

value of ER-£ for Series 54 (col. 12) is low relative to other tests. In

this case, the operator used the safety hammer after a day of testing with the

donut hammer.

44
NUMBER

OF

BLOWS

15

10

5

0

DONUT HAMMER

Series 32-35

AW rod (left) izi

0

5

0

rnrTI

Series 28-31

AW rod (right)

In

n

5 - b

nil K1 n i

Series 48-52 AW rod

I I L

Series 82, 85, 94 (NW rod)0

± EFE1.

Series 108-109, 118,

Same hammer^ 125-126 (BW rod)

mm n 1 z

i n n

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

Ei ERj

ENERGY TRANSFER RATIO, ETR = — = zrr

tv tKw

Figure 3.7 Histograms of energy transfer ratio, ETR, for donut and

safety hammers

45
An example of three operators using the same drill rig but getting different

values of ER-^ is given in Series 102, 103, and 104 where operators I, J, & K

obtained average ERj[ values (col. 8) of 60, 49, and 54 percent, respectively.

When operator I came back to redo the series (Series 105), he again obtained

60 percent for ER^ (col. 8). Other examples of operators obtaining consistent

results can be seen in table 3.3. It is interesting to note that only part of

the difference in ER^'s produced by the three operators is attributable to

differences in fall height. There are also differences in the ETR, and to a lesser extent in the percentage of energy lost before hammer impact.

When the results of ER^ are listed for the usual operator of his rig and

equipment, we again observe a variation of results: ER-^ = 40, 47, 46, 60, 69,

67, and 58 percent (col. 8) from Series 57, 79, 95, 102, 110, 113, and 120,

respectively. A further discussion of average ER^ values for drill rigs tested

to date is given in section 4.2.

The differences in ER^ due to hammer type have been described before (Kovacs et

al., 1981; Martin and Douglas, 1981; Robertson et al., 1982; and Schmertmann

and Palacios, 19^9) and are observed, for example, in Series 52 and 60 where

the depth and ER

v are the same. The values of ER^ are 33 percent for the

donut hammer and 42 percent for the safety hammer. In Series 82 and 83, ER^

for the donut and safety hammer are 43 and 56 percent, respectively. Usually

the safety hammer provides a larger ER-^ in the drill rods than does the donut

hammer. Youd and Bennett (1983) found that the N values are generally more

with a donut hammer than with a safety hammer. They attributed the difference

to a more efficient energy transfer of the safety hammer. In six check tests

at one site in holes drilled with a hollow stem auger, the donut hammer gave N

values which were on the average 45 percent higher than those obtained with the

safety hammer.

It was found that a wide variety of drill rod size is used in engineering

practice. Brown (1977) found no significant difference in his field studies

between SPT N values obtained with A rods and N rods up to 110 ft (34 m) depth

in loose to very dense granular soils. From equation 3.2 we see that E^, the

energy in the drill rods, is inversely proportional to the cross-sectional

area of the drill rod. The typical drill rod sizes and their cross-sectional

area have been given in table 3.1. It is not uncommon to install short sec- tions (one to three feet) of parallel wall rod on top of upset wall rod to

attach the SPT hammer. One might expect adverse effects from the abrupt discontinuties of cross-sectional area. Figure 3.8 illustrates the force-time

history for three blows of a safety hammer under three different rod configurations. The insertion of a 2 ft (0.7 m) section of parallel wall rod below the

load cell resulted in a higher peak force but no real difference in ER^. In

Series 128B, blow 16, a compressive wave return is noted (similar in shape to

figure 3.5) resulting in an incorrect ER^ Calibrator reading.

* Table 3.5 shows the differences between ER

v delivered by different operators

using safety hammers with different drill rigs^ Again, it can be seen that

the differences are considerable. When the ER values are adjusted to the

v actual fall height, column 5, it can be seen that the differences are not

substantially diminished. Thus, other parameters contribute to the energy

46
47

Figure

3.8

Comparison

of

force-time

wave

forms

when a

2-ft

(61

cm)

section

of

BW

parallel

wall

drill

rod

is

inserted

just

below

load

cell
loss during the hammer fall. To what extent these parameters are operator

dependent has not been established.

Table 3.5

Summary of Average Energy Ratios for Velocity

Series Operator

* er

y

(%)

H, in

(in)

ER* x 30/Ha V

(%)

(1) (2) (3) (4) (5)

83 C 70 30.8 68.2

84 D 71 29.8 71.5

102 I 68 32.3 63.2

103 J 57 30.3 56.4

104 K 65 30.8 63.3

111 K 71 29.8 71.5

112 J 50 29.6 50.7

115 K 75 30.0 75.0

117 I 70 29.9 70.2

119 J 76 29.7 76.8

121 L 68 29.6 68.9

122 M 70 30.0 70.0

123 N 70 30.3 69.3

a Energy ratio for velocity adjusted for actual

fall height.

The rate at which the SPT is performed may vary by a factor of three or more.

Some operators are very deliberate with rates between 11 and 26 blows per minute

(Series 102 to 119), while others use higher rates (40 to 50 blows per minute).

Operator C reduced his rate from 54 to 38 blows per minute when energy measurements were taken (see Series 81 and 83, col. 16). We observed no relationship

between ER-^ and blow count rate.

Figure 3.9 illustrates the variation of average energy ratio, ER^ , versus drill

rod length from field tests at four different sites. The energy ratio is

adjusted for drill rod length effects and, therefore, should remain constant

with depth unless the SPT procedure is altered by the operator for some reason

or another. As expected, the safety hammers are seen to have higher energy

ratios than the donut hammers. Observe the wide range of energy ratios measured,

from about 25 to 75 percent.

48
0.2 0.8 1.0

ENERGY RATIO - ERi

0

10

50

60

0.4 0.6

T T THEORETICAL MAXIMUM FOR

140 lb. (63.5 kg) HAMMER

(BEFORE K2 CORRECTION)

O DONUT

A SAFETY

(ROBERTSON et al. f 1982) • F (DONUT)

SAFETY

O DONUT

A SAFETY

V SAFETY

(SCHMERTMANN & PALACIOS, 1979) TEST DEPTHS REPORTED;

ADD 5 FEET TO EACH POINT TO OBTAIN ROD LENGTH.

SERIES 48 - 52

SERIES 54 - 61

LAW ENGRG. TESTING CO.

Figure 3.9 Variation of average energy ratio, ER-j , vs. drill rod

length for two types of SPT hammers. All data include

l<2 correction.

49
4. ESTABLISHMENT OF A REFERENCE ENERGY LEVEL (REL)

4 . 1 GENERAL

It has been previously noted (see section 1.3) that the accuracy of the SPT

could be improved in two ways:

1. Standardization of equipment and procedures.

2. Determination of the energy delivered by typical U.S. equipment and

procedures and referencing of all SPT data to a common reference

energy level.

The information previously discussed deals with energies delivered by

miscellaneous equipment and procedures. This section deals with the establishment of an energy level to which SPT data can be referenced.

The question arises what this energy should be, and at which point in the SPT

system it should be defined. In ASTM Standard Method D 1586, the potential

energy is defined as 4200 in-lbf (475J). However, the data presented indicate

that a specified potential energy does not lead to uniform test results because

of the wide variations in the energy actually transmitted through the drill rod

(E^). Greater uniformity could be achieved by specifying the energy transmitted

through the drill rod. One problem which has to be solved if this approach is

to be used is the calibration of the measurement methods used to determine E^ by

an independent measurement. To date this has not been accomplished. A second

problem to be addressed in the future concerning the use of our present design

correlations with the SPT N value is the past average energy.

The following sections present available data that can be used in the

determination of an average value for E-^, which is typical of present U.S. SPT

practice. The data may have to be re-evaluated when data on the accuracy of

the E.£ measurements becomes available.

4.1.1 The Need to Establish a National Average Energy (NAE)

The concept of the NAE was first brought to the attention of the profession by

Kovacs et al. (1981). The average energy ratio, ER^ , for a given drill rig

model is the average energy ratio determined from a statistically significant

number of drill rigs of that particular model. When all the data are averaged,

based on the number and availability of drill rigs used throughout the United

States, then a weighted NAE for the drill rigs used in U.S. practice under

normal operating conditions (drill rig, hammer, and operator) can be determined.

Once known, the NAE can then be used as a reference energy for SPT practice.

The next three figures show SPT blow count data versus depth performed by

three separate drill rigs (at three different sites) all using two types of

hammers in the same or adjacent borings. The average energy ratio, ER^, was obtained for each SPT. Figure 4.1 from Robertson et al., 1982, shows a blow

count profile for both the safety hammer (triangle data points) and donut

hammer (circle points). The average energy ratio, ER-ji, is located adjacent to

the data point, in parentheses. The donut hammer, transferring less energy

50
SPT N, BLOWS/FT

(MEASURED)

0 10 20 30 40 50

SPT Nc , BLOWS/FT

(CORRECTED TO ERj = 55%)

o DONUT HAMMER, AVERAGE OVERALL ENERGY RATIO, ERj = 43%

a SAFETY HAMMER, AVERAGE OVERALL ENERGY RATIO, ERj = 62%

| 45 | MEASURED AVERAGE ENERGY RATIO, ERj, %

• SPT BLOW COUNT CORRECTED TO ERj = 55%

(After Robertson et al., 1982)

Figure 4.1 Comparison of SPT N values using alternative donut and safety

hammer with energy corrected Nc values to ER^ equal to 55

percent (after Robertson et al., 1982)

51
into the drill rods, has the higher blow count. Robertson et al. chose to

correct each data point to an energy ratio of 55 percent. Their correction was carried out assuming an inverse variation of N value with E^ , as suggested by

Schmertraann and Palacios, 1979, according to equation 4.1, and dividing Ej[ E*.

NC = Hn

( ERl>m

< ERl>c

(4.1)

where Nc the corrected blow count for the selected Energy Ratio, (ER^) C

Nm = the measured blow count

(ERi) m = the measured energy ratio

(ERj;) c = the selected energy ratio.

When the blow counts from both hammers are corrected using equation 4.1, the

resulting N value profile is more consistent with depth. Figures 4.2 and 4.3

show other examples where when blow counts are corrected to 55 percent average

energy.

4.2 PRESENT DATA ON THE NAE

As was stated previously: Because there are approximately 37 drill rig

models used in the United States, a significant amount of data will have to be

accumulated and a statistical analysis performed before an NAE can be established. Using a common reference energy as the rod energy should allow reproducible and consistent blow counts among different drill rigs. Since the

publication of data by Kovacs et al. , (1981), the number of data points for

drill rigs has increased from 33 to 56. The data are summarized in table 4.1.

The data presented in table 4.1 are based on either the integration of the

F(t) curve by a DPO or from the direct readout of the SPT Calibrator, or both.

Where both values are available, the Calibrator was used unless review of F(t)

time history indicated "hard driving" and the integration times were in excess

of 2&'/c. The notes appended to table 4.1 document how the data in table

4.1 were used to present the values of ER^ graphically for safety hammers in

figure 4.4a and for donut hammers in figure 4.4b. Note that there are two

different scales for the energy ratio ER^ for figures 4.4a and 4.4b. The top

scale is based on the results of equation 3.2 with corrections Kj and K2

. The

lower scale is based on equation 3.6 that includes corrections , K2 and Kc

.

The arithmetic average of the ER^ data shown on figure 4.4 which is not a weighted average, is 56.2 percent, uncorrected for the actual compressive wave

velocity. Applying the Kc correction (16000/16878), a value of 53.3 percent

is obtained. However, since not every drill rig model is used with the same frequency, a weighted average must be determined.

If it is assumed that the data presented in table 2.2, "A Summary of Drill Rig

Models Used in Engineering Practice with numbers >1,” is representative of the

frequency of present-day use, then the weighted average of the energy ratio

data shown in figure 4.4 may be computed by:

52
Table 4.1 Tabulation of Average ERj

[Computed Assuming Compressive Wave Velocity in Rods = 16848 ft/s (5144 m/s)]

ER± (%)

Hammer

Type Drill Rig Model

No. of Turns

Rod

Type Remarks Reference

(1) (2) (3) (4) (5) (6) (7)

71 S CME 45 3 AW Schmertmann and Smith ( 1977

)

a

74 S CME 45 3 AW Schmertmann and Smith (1977) a

53 s CME 45B 4 AW Schmertmann and Smith (1977) a 59 s Failing 1500 3-4 NW Schmertmann and Smith ( 1977

)

a

47 s Mayhew 1000 3 AW Schmertmann and Smith ( 1977

)

a

57 s Failing 1500 3 NW Schmertmann and Smith (1977) a

55 s CME 45 3 AW Schmertmann and Smith (1977) a 56 s CME 45 3 AW Schmertmann and Smith (1977) a

54 s CME 65 3 AW Schmertmann and Smith (1977) a

71 s CME 55 4 AW Schmertmann and Smith (1977)a

57 s Failing 1500 N/A NW Wire-Drum Schmertmann and Smith (1977)a

56 s Acker M-2 2 Brown, R.E. (1980) Private Communication

53 s Acker M-2 2 Brown, R.E. (1980) Private Communication

55 s Mobile B-34 N/A Safe-T-Driver Brown, R.E. (1980) Private Communication

76 D CME 55 3 Brown, R.E. (1980) Private Communication

44 s CME 55 2 Brown, R.E. (1980) Private Communication

64 s Mobile B-33 ATV 2 Brown, R.E. (1980) Private Communication

50 s Mobile B-80 N/A Safe-T-Drive Schmertmann, J.H. (1980) Private Communication

41 s Mobile B-80 2 Schmertmann, J.H. (1980) Private Communication

60 s CME 45 2 Mud Bug Schmertmann, J.H. (1980) Private Communication

51 D CME 45 1 Swamp Buggy Steinberg, S.B. (1980) Private Communication

36* D CME 45 2 Swamp Buggy Steinberg, S.B. (1980) Private Communication

45 D CME 45 2 Steinberg, S.B. (1980) Private Communication

71 D CME 55 2 Oper. D Steinberg, S.B. (1980) Private Communication

60* D CME 55 2 Oper. F Steinberg, S.B. (1980) Private Communication

42 D Joy B-12 2 Oper. A Steinberg, S.B. (1980) Private Communication

55* D Joy B-12 1 Oper. G Steinberg, S.B. (1980) Private Communication

46 S Mobile B-34 N/A Safe-T-Driver, J Steinberg, S.B. (1980) Private Communication

32 D Mobile B-61 3 Oper. A Steinberg, S.B. (1980) Private Communication

40* D Mobile B-61 2 Oper. B Steinberg, S.B. (1980) Private Communication

37* D Mobile B-61 2 Oper. C Steinberg, S.B. (1980) Private Communication

68 S CME 55 2.2 N Old Rope Kovacs, et al., 1981, Series l'5 69 S CME 55 2.2 N Old Rope Kovacs, et al., 1981, Series 3 71 S CME 55 2.2 N Old Rope Kovacs, et al., 1981, Series 6 75 S CME 55 2.2 N Old Rope Kovacs, et al., 1981, Series 8 81 S CME 55 2.2 N New Rope Kovacs, et al., 1981, Series 9

C 77 S CME 55 2.2 N New Rope Kovacs, et al., 1981, Series 11

73 S CME 55 2.2 N New Rope Kovacs, et al., 1981, Series 17

62 S CME 750 2.75 AW Kovacs, et al., 1981, Series 19^

63 S CME 750 2.75 AW Kovacs, et al., 1981, Series 20

65 S CME 750 2.75 AW Kovacs, et al., 1981, Series 22

70 S CME 750 2.75 AW Kovacs, et al., 1981, Series 25

57 D CME 55 2.2 AW Kovacs, et al., 1981, Series 28e

Notes: The combination of the usual operator, his drill rig with cathead and rope, and the hammer are considered

as a separate data point. When a second operator uses a rig that is not his own, that data point is denoted by an asterisk, *, and is not plotted on figure 4.4.

a. The values shown in column (1) have been revised to reflect a theoretical compressive wave velocity of

16,848 ft/sec. (5144 m/s). The original data were computed using C=16000 ft/s (4877 m/s). The text discusses how all the data in table 4.1 are used in figure 4.4.

b. The weighted average of Series, 1, 3, 6, and 8 taken as 72%

c. The weighted average of Series 9, 11, and 17 taken as 77%

d. The weighted averge of Series 19, 20, 22, and 25 taken a9 63%

e. The weighted average of Series 28 and 31 taken as 57%

f. The weighted average for Series 32 and 33 taken as 35%

g. The weighted average for operator A taken a 66%

h. These data reduced using K<. correction from actual wave velocity measurements. The corresponding corrected

values are 60, 70 and 64 percent, respectively.

53
Table 4.1 Continued

ER± (%)

Hammer

Type Drill Rig Model

No . of TurnsRod

Type Remarks Reference

(1) (2) (3) (4) (5) (6) (7)

55 D CME 55 2.2 AW Kovacs, et al., 1981, Series 31 31 D CME 45 2.2 AW Kovacs, et al., 1981, Series 32^

46 D CME 45 2.2 AW Kovacs, et al., 1981, Series 33 78 S CME 55 2 AW Brown, R.E. (1981) Private Communication

40 S Failing 1500 2 AW Schmertmann, J.H. (1982) Private Communication

51 S Failing 1500 2 AW Schmertmann, J.H. (1982) Private Communication

63 S Failing 1500 2 AW Schmertmann, J.H. (1982) Private Communication

68 S CME 45 1 AW N~25 Schmertmann, J.H. (1982) Private Communication

31 D Longyear 34 3 - N~14, Lg. Anvil Schmertmann, J.H. (1982) Private Communicatio

57 D Failing 1500 2 N V. Small Anvil Schmertmann, J.H. (1982) Private Communication

59 S Failing 250 2.75 N Oper. A, N=15 Schmertmann, J.H. (1982) Private Communication®

69 s Failing 250 2.75 N Oper. A, N=62 Schmertmann, J.H. (1982) Private Communication®

59* s Failing 250 2.75 N Oper. B, N=23 Schmertmann, J.H. (1982) Private Communication

71* s Failing 250 2.75 N Oper. C, N=22 Schmertmann, J.H. (1982) Private Communication

55 s Mobile B-50 2 AW N=10 Schmertmann, J.H. (1982) Private Communication

62 s Failing 1500 2.75 N Oper. A, N=41 Schmertmann, J.H. (1982) Private Communication

59* s Failing 1500 2.75 N Oper. B, N=17 Schmertmann, J.H. (1982) Private Communication

64* s Failing 1500 2.75 N Oper. C, N=28 Schmertmann, J.H. (1982) Private Communication

50* s Failing 1500 2.75 N Oper. D, N=19 Schmertmann, J.H. (1982) Private Communication

62 s Failing 1500 2.75 N Oper. C, N=6 Schmertmann, J.H. (1982) Private Communication

63 s Failing 1500 2.75 N Oper. C, N=14 Schmertmann, J.H. (1982) Private Communication

49* s Failing 1500 2.75 N Oper. D, N>100 Schmertmann, J.H. (1982) Private Communication

60* s Failing 1500 2.75 N Oper. A, N=15 Schmertmann, J.H. (1982) Private Communication

64 s CME 55 1.75 aW Oper. A, N=12 Schmertmann, J.H. (1982) Private Communication*1 75* s CME 55 1.75 AW Oper . B Schmertmann, J.H. (1982) Private Communication

68 s CME 45C 1.75 AW Oper. A. (Ser. H) Schmertmann, J.H. (1982) Private Comunication

43 D Longyear 34 2 Campanella, R.G. and Robertson, R.K. (1982),

Private Communication

62 s Longyear 34 2 Campanella, R.G. and Robertson, R.K. (1982),

Private Communication

39 D Longyear 38 2 Campanella, R.G. and Robertson, R.K. (1982),

Private Communication

47 S Mobile B61 2 NW Oper. A Table 3.3, Series 79 48 S Mobile B61 2 NW Oper. B Table 3.3, Series 95 60 s Mobile B61 2 BW Oper. A Table 3.3, Series 102 49* s Mobile B61 2 BW Oper. B Table 3.3, Series 103 54* s Mobile B61 2 BW Oper. C Table 3.3, Series 104

70 s Longyear HC150 2 BW Oper. C Table 3.3, Series 111

72 s CME 75 2 BW Oper . B Table 3.3, Series 113 and 119

60 s Failing 1500 2 BW Oper. D Table 3.3, Series 128B and 130

33 D CME 45 2 AW Table 3.4, Series 52 40 S CME 45 2 AW Table 3.4, Series 61

54
0

5

10

GO

LU

15

20

25

30

35

Figure 4.2

BLOW COUNT, N - BLOWS/FT.

Comparison of SPT N values using safety hammer and F (donut)

hammer with energy corrected Nc values to ER^ equal to 55

percent (modified from Schmertmann and Palacios, 1979)

55
SPT

N,

BLOWS/FT

SPT Nc,

BLOWS/FT

(MEASURED)

(CORRECTED

TO

ERj =

55%) !

CO

LO CO1 CO LO

GO

GO LU

UJ oc

Q£ UJ

UJ GO ’GO

^p

--P o"^ CO

CO

CO

II

II

o^- IO

lO

II = C 2 oq go

<c §3E

O < C*5

CD

h—

Qu

GO• 33

.3 4-1 s

4-1 3 3 o 3 u O <u T5 a

TJ

m 3 in

03 o M 4J 3

•H § 3 3 3

X! o*3

•u •H

Pi

>4-1

W 3

CO

O

4J W)3 CO •H a)

CO 3 3 rH3

CO > 33 o

iH !3 3> TJ3

53 4-) o H 3

CU

U

C/3 l-i o

y-i o o3 bo o M

CO 3

•H 3 M 3 3a ,3 s 4-1 o •H o £ J 111 ' \ 1 u • ? 5 i : x ) ,o

S\ It

i' 1 2 { H I < 1 IT ! >0 : X r “ I u

CO

0)u3

bo

•H I 1

(id) I - SQOU JO H19N3T

56
ENERGY

RATIO

FOR

F(t) =

Ej/E* =

ENTHRU -

ERj

57

CORRECTED

ENTHRU,

ERj

FOR Kc=

0.948

COMPRESSIVE

WAVE

VELOCITY =

16,000

ft/s

(4877

m/s]
ENERGY

RATIO

FOR

F(t]

=

Ej/E*

-

ENTHRU

=

ERj

CD

oo

CO

t/3

CO

r-» S 2 <=i ^

ii ^

o «-'

CO

=» £

ID

y

*

r>- LU

o > O OO

00

LU

OC

Q_

CO

ca

oc

CM

i Z ID

ooID

o

ID ID ID ID

CD

ID

ID

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58

Figure

4.4b

Summary

of

data

to

date

of

energy

ratio

for

F(t),

ER^

(a)

safety

hammers

(b)

donut

hammers
ER. (Avg for Fig 4.1) = Z 2L x 100 (4.2)

'! ZB

where

A = average value of ER^ for a given drill rig model, data from table 4.1

B = frequency of use as determined by the number of drill rigs of a given

model, column 2 of table 2.2, divided by the sum of all the drill rig

models in column 2, table 2.2 (952 ea).

Such a computation for table 4.1 leads to a value of 58.8 percent. When this

value (58.8 percent) is corrected for a compressive wave velocity of 16,000 ft/s

(4877 m/s) (16,000/16,878) the corresponding average would drop to 55.7 percent,

rounded off to 56 percent.

The wide scatter in the data shown in figure 4.4a and b raises the question

whether the observed differences between the measured energy ratios among the

various drill rig models are statistically significant (not caused by scatter

of data for individual rigs) or whether the differences can be explained by

the natural variation in the data. To test this hypothesis, a one-way analysis

of variance (ANOVA) was performed for each of the two sets of data (safety and

donut hammers). The results of the ANOVA indicate that a comparison of the

differences within a drill rig model are about as large as the differences in

energy ratios between drill rig models themselves. The comparisons are not

large enough to obtain statistical significance (at the 5 percent level) based

on the available data. Based on this result, there is n£ strong reason to use

any specific weighting procedure to compute an average energy ratio for figures

4.4a and 4.4b. At this time (1983), a simple unweighted average will suffice.

The observed trend of energy variability underscores the need to standardize

the SPT equipment and procedures and/or measure energy on some prescribed

basis so that blow counts may be compared among various drill rigs on a common

basis. A method for energy measurement based on the theory discused in

section 3.3.1 is now (1983) under discussion with ASTM D 18. The intent

is to permit blow count adjustments and comparisons using equation 4.1.

59
ENERGY

RATIO

FOR

F(t)

=

Ej/E*

=

ENTHRU

=

ERj

5.

FINDINGS, CONCLUSIONS, AND RECOMMENDATIONS

5.1 FINDINGS

i

t<

<

i

c

t

Based on this investigation, it was thought that:

1. The hammer potential energy, kinetic energy just before impact, the energy

passing through the drill rods, and the energy transfer ratio, ETR, vary

from blow to blow during the SPT.

2. A wide variety of drill rigs are used to perform the SPT in engineering

practice.

3. Three types of SPT hammers are primarily currently used in engineering

practice. In the order of decreasing popular use they are the safety

hammer, donut, and the pin-guided hammer.

4. Based on the studies described in this report, the use of the safety hammer

is almost twice as much as the donut hammer in current SPT practice. The

arithmetic average energy ratio, ERi, for the safety hammer is 59 percent,

while that for the donut hammer is 47 percent based on results in figure

4.4a, 4.4b.

5. Some district offices of the U.S. Army Corps of Engineers and the Waterways

Experiment Station have used a hydraulically operated, chain driven triphammer whose dimensions are approximately 5 1/2 in (140 mm) in diameter

and 15 3/4 in (400 mm) long and consists of a lead filled steel casing.

No published energy ratio data is available on these hammers.

6. At least five sizes of drill rod are used to perform the SPT. They are

A, AW, BW, N, and NW rod sizes. Depending on size, some drill rods are available both in upset wall and parallel wall. When required, short sections of parallel wall rod may be used with longer sections of upset wall

rod with relatively no change in energy ratio, ERi, reading.

7. Two procedures for raising and lowering the SPT hammer are used in

practice. They are the hold-drop procedure with a rate of 15 to 25

blows/minute and the regular (or continuous) rhythmic procedure with

a rate of 30 to 60 blows/minute.

8. Most drill rig operators use 2 turns of rope around the cathead.

9. Based on results from experienced drill rig operators performing the SPT,

a wide, random variation of fall heights can be expected with each blow,

as well as the corresponding energy ratio for velocity, ERV . A3 in (76

mm) difference in fall height in sequential blows is not uncommon. The

average fall height of the average of seventy-five test series was found

to be 30.98 in (787 mm) with a standard deviation of 1.48 in (38 mm) and a coefficient of variation of 4.8 percent.

60
10. The SPT sampler as manufactured in the U.S. today has an enlarged inside

diameter past the cutting edge or shoe to allow for the inclusion of

liners, bringing the I.D. equal to that of the cutting shoe. However,

liners are seldom used in engineering practice in the U.S. The use of

liners inside the SPT sampler varies internationally. Liners are not used

in the U.S.; but the inside diameter of the split barrel is 1.5 in (38 mm)

while the standard samplers used in Japan and the United Kingdom are 1 3/8 in (35 mm), the same diameter of the cutting shoe.

11. When the energy is measured in the drill rods by a load cell, it is

necessary to correct the computed energy for: the load cell not being at

the point of impact; the drill rod length not being infinite; and for the

actual compressive stress wave velocity being less than the theoretical

value.

12. The cross-sectional area setting on the SPT Calibrator may be used only

for NW parallel wall rod. If NW upset wall rod is used, a correction

factor of 1.873 (2.27 in^/1.212 in^) must be applied (multiplied) to the

ER.^ reading.

13. Electronic glitches and compressive wave returns are two situations that

caused abnormally high readings of ER^ by the SPT calibrator. This

phenomena goes undetected unless the wave form is monitored and/or the

actual integration time (of equation 3.6) is compared with the computed

value of 2 Jl'/c.

14. It is imperative to measure the integration time of the Calibrator in the

field in order to insure that the load cell is working properly, as well

as to interpret the data properly. In the event an excessively high reading occurs due to a compressive wave return instead of the usual tensile

wave return, the integration time can be compared with the computed return

time based on the rod length and a return compressive wave identified and

the data rejected.

15. The energy transfer ratio of the donut hammer and the safety hammer are different. It appears that the donut hammer transfers the available

kinetic energy just before impact in a much more random way than the

safety hammer.

16. Nearly identical values for the energy ratio ER^ were obtained from the

SPT Calibrator and the Digital Processing Oscilloscope (DPO). However,

the SPT Calibrator by itself does not permit viewing of the force-time

wave form. An oscilloscope must be attached.

17., The insertion of a 2 ft (0.7 m) section of BW parallel wall below the load

cell and above a 35 ft (10.7 m) and a 40 ft (12.2 m) section of BW upset

wall drill rod resulted in higher peak forces but no appreciable

differences in ER^.

61
ENERGY

RATIO

FOR

F(t]

=E

j/E*

=

ENTHRU

=

ERj

18. When SPT N values are corrected for a common energy, more consistent N

values are obtained when comparing test results for safety and donut

hammers at the same site (see figures 4.1, 4.2, and 4.3).

19. Since the introduction of the concept of the national average energy (NAE)

in 1981, information on the average energy ratio, ER^ of drill rigs has

increased from 33 to 56 drill rigs. The present (1983) observed variation

in energy derived by a given drill rig model is almost as great as the

variation of ER^ among drill rig models.

5.2 CONCLUSIONS

4

ii

(

i

i

i

Based on the data and findings in this report, the following conclusions are drawn:

1. The hammer to rod transfer of energy (ETR) is important, variable, and

unpredictable. Therefore, the energy in the drill rods, ER^ cannot be

predicted from hammer kinetic energy but needs to be measured directly

in the rods.

2. The variability of the energy passing through the drill rod as delivered by

present U.S. equipment and procedures is too great to be eliminated by a modification of procedures alone. Equipment as well as procedures would

have to be modified to achieve satisfactory results.

3. More than one drill rig- SPT system (which includes the operator in the

rope-cathead method) at a site can produce N-value variability due to ER^

variability among the drill rigs. N-value varies approximately inversely

with ER^. Correcting blow counts with known average energy ratios to a specified common energy ratio provides a more consistent profile of N

values with depth.

4. While it is desirable that the reference energy level approximate the

national average energy, the data sample presently available is too

variable to permit a statistically significant estimate of the national

average energy.

5. The methods presently used to measure the energy in the drill rod appear

to give reasonable and consistent results but have not yet been verified

by an independent theory and measurements.

6. The energy passing through the drill rod is not the only source of

variability in the SPT results. The use of liners in the SPT sampler is

also an important source of variability. The effect of the I.D. clearance

when omitting the liner in U.S. samplers must be considered when evaluating

SPT results from other countries.

62
7. The potential energy and kinetic energy of the hammer just before impact

are the most reliable (checkable) energy measurements. The use of equation 3.6 to compute the energy passing through the drill rods by either

the DPO or the Calibrator is considered satisfactory but not as reliable

as the other two energies mentioned.

8. The drill rig, the SPT equipment (hammer, cathead and rope), and the

operator should be considered as a unit when SPT energy is being evaluated

9. The use of blow count data across international borders should be used

with caution as the energy passing through the drill rods is not known in

other countries and because of the equivalent use of liners in other

countries.

10. In order to assure the actual occurrence of a tension wave cutoff as assumed in the use of equation 3.6 (integration of the force squared-time

curve), it is necessary to confirm that the integration time compares

favorably with the computed cutoff time of 2 £'/c.

11. Based on limited tests, the inclusion of or intermixing of parallel wall

drill rods with upset wall drill rods does not appear to affect ERj[ values

5.3 RECOMMENDATIONS

Based on the conclusions from this report, the following recommendations are

made:

1. SPT equipment and procedures be established which minimize the variability

of the blow count. This would require a tripping mechanism, a standard

hammer/anvil/drill rod system, a standard sampler with or without liner,

and standard drilling procedures.

2. Until the SPT equipment is standardized:

(a) The energy passing through the drill rod should be monitored and test

results referenced to a standard energy, either the national average

energy or an internationally accepted energy level.

(b) The use of liners in the sampler should be eliminated, but the 1.5 in.

barrel I.D. retained.

(c) The test procedures be modified to minimize the test variability.

3. If we were to recommend SPT testing conditions to use in evaluating the

liquefaction potential of an important structure on a site, we would

recommend the following conditions:

(a) Safety (type) hammer with AW drill rod stem with an available stroke

of at least 35 in (889 mm).

(b) Two turns of new rope around the cathead.

63
ENERGY

RATIO

FOR

F|t)

=

Ej/E*

=

ENTHRU

=

ERj

(c) Use of an 8 in. (203 mm) clean, shiny cathead.

(d) AW (parallel wall) drill rod.

(e) Rotary drilling with mud.

(f) Upward deflecting wash drilling bit.

(g) Blow count rate of 30 to 40 blows/minute.

(h) An SPT sampler with no liners [I.D. of 1.5 in (38.1 mm)].

(i) The fluid level in the bore hole should be at all times higher than

the groundwater level. This can be accomplished by requiring that the

surface of the drilling mud be at the top of the bore hole at all

times.

(j) A 2 in (50 mm) colored band shall be permanently marked on the hammer

guide pipe [from 28 to 30 in (711-762 mm) above the anvil] to help the

operator produce an average 30 in fall height.

(k) ERi and integration time should be monitored and recorded as needed

during penetration from 6 to 18 in (300 to 450 mm).

[Procedures c, e, f, and h are based on findings by Schmertmann (1977).]

4. It is suggested that the blow count rate used in performing the Standard

Penetration Test remain consistent for a given site and job. This is

especially true in the case of performing the SPT in saturated silts where

negative pore pressures may develop. In loose silts, the opposite may

result where positive pore water pressures are induced. It is recommended

that a rate of 30 to 40 blows per minute be specified, which is not that

difficult for operators to obtain. Until further testing is performed in

the field, this could provide a compromise and eliminate another variable

in the SPT. However, with the advent of automatic SPT hammers operating at

50 to 60 blows per minute, field studies should be performed to determine

the effect of testing rate on the N value with the above mentioned soil

conditions.

5. To be consistent with present engineering practice, it is recommended that

liners not be used in the SPT sampler during the performance of the SPT.

This approach is presently being suggested in the revision of ASTM Standard

D 1586. Because of the wide variation in energy ratio for velocity, it is

recommended that only the ER^ measurement be made which does, in fact,

control the blow count unless it is desired that energy transfer ratio

information be obtained.

6. When ER^ data is reported, it is suggested that it contain the three

corrections (one for load cell location with respect to the point of impact,

Kj_, length of drill stem, K. 2 , and effect of the measured compressive

wave velocity in the rods, Kc ).

64
7. Thus, if the energy ratio is to be measured for the purpose of

establishing an equivalent blow count to some specified ER^, then it is

recommended that the energy ratio be determined during the performance of

the SPT rather than on an infrequent basis. ERj[ measurements, along with

a check on the integration time, should be made to give the engineer confidence that the system (drill rig, operator, and hammer) average ER^ falls

within a band of +_ 5 percent. The number of measurements of ERj[ may

require a once per hour or once per day or once per month check of ER^,

depending on experience and changes in the system.

8. Sufficient data to recommend a reference energy level (REL) appears to

be available in the report. The earliest ERi measurements led others to

suggest that the current average ERi values in practice were around 50 to

55 percent. Our data base also gives overall weighted and unweighted

averages of about 55 percent. We therefore tentatively recommend using a reference ERi of 55 percent for N-value adjustments based on ERi measurements.

9. The following additional research be conducted:

(a) Check the present load cell integration method of determining ERi by an independent energy theory and associated measuring system.

(b) ERi measurements for typical Japanese SPT practices to better interpret

available liquefaction data.

(c) Acquisition of a larger database to determine the national average

energy.

(d) Study of the effect of drill rod and anvil configurations on the

energy transmission.

(e) Study the effect of borehole diameter and drilling method on N value.

(f) Study the types of SPT hammers used historically so as to evaluate the

"past national average energy." Such a study would allow a comparison

of past energy levels with present and future automatic hammer energy

levels when using SPT design correlations established in the past.

65
ENERGY

RATIO

FOR

F|t)

=E

j/E*

=

ENTHRU

=ER

j

6 . ACKNOWLEDGMENTS

This study was primarily sponsored by the Division of Health, Siting, and Waste

Management, Earth Science Branch of the Office of Nuclear Regulatory Research

of the U.S. Nuclear Regulatory Commission (NRC) and partially by the Division

of Research of the United States Bureau of Reclamation, the Department of Water

Resources, State of California, and by the Structures Division, Center for

Building Technology, National Engineering Laboratory of the National Bureau of

Standards

.

Keith R. Eberhardt of the Statistical Engineering Division, The Center for

Applied Mathematics of NBS provided the Analysis of Variance (ANOVA) of the

data presented in figure 4.1. R.E. Brown of Law Engineering Testing Company

provided some energy ratio data with depth that were used in figure 3.9.

Critical review and helpful suggestions concerning this report have been

provided by R.E. Brown and J.H. Schmertmann. Their contribution is greatly

appreciated

.

i

i

t

i

i

<

i

i

i

66
7 . REFERENCES

British Standards Institution (1975), "Methods of Test for Soils for Civil

Engineering Purposes," BS 1377, Test 19, Determination of the Penetration

Resistance Using the Split-Barrel Sampler, pp. 103-104.

Brown, R.E. (1977) "Drill Rod Influence on Standard Penetration Test," Journal

of the Geotechnical Engineering Division, ASCE, Vol. 103, No. GT11, pp.

1332-1336.

Casagrande, A. (1976), "Liquefaction and Cyclic Deformation of Sands: A

Critical Review," Presented at the Fifth Panamerican Conference on Soil

Mechanics and Foundation Engineering, Buenos Aires, Argentina, November,

1975; Reprinted as Harvard Soil Mechanics Series No. 88, January 1976, 27 pp

.

and figures.

Casagrande, A. and Casagrande, L. (1968),

" Report , to American Electric Power

Service Corporation on Foundation Investigations for the Donald E. Cook

Nuclear Power Plant," Appendix G of Amendment 5, Cambridge, Mass.

Castro, G. (1975), "Liquefaction and Cyclic Mobility of Saturated Sands,”

Journal of the Geotechnical Engineering Division, ASCE, Vol. 101, No. GT6,

pp. 551-569.

Fletcher, G.F.A. (1965), "Standard Penetration Test: Its Uses and Abuses,"

Journal of the Soil Mechanics and Foundations Division, ASCE, Vol. 91,

No. SM4, pp. 67-75.

Goble, G.G. and Ruchit, P. (1981), Measurements of Impacts Velocity on Penetration Testing Systems," Dept, of Civil, Environmental and

Architectural Engineering, University of Colorado, October, 171 pp.

Gravare, G-J . and Hermansson (1980), Practical Experiences of Stress Wave

Measurement," International Seminar on the Application of Stess Wave

Theory on Piles , A. A. Balkema, Rotterdam, pp. 99-120.

Hall, J.R. (1982), "Drill Rod Energy as a Basis for Correlation of SPT Data,"

Proceedings of the Second European Symposium on Penetration Testing,

Amsterdam, A. A. Balkema, Rotterdam, Vol. 1, pp. 57-60.

Japanese Standards Association (1976), "Method of Penetration Test of Soils,"

Japanese Industrial Standard (JIS) 1219-1961 (Reaffirmed: 1976), Edition

6, Tokyo, Japan, 3 pp.

Kovacs, W.D. (1979), "Velocity Measurement of a Free-Fall Hammer," Journal of

the Geotechnical Engineering Division , ASCE, Vol. 105, No. GT1, pp. 1-10.

Kovacs, W.D. (1980), "What Constitutes A Turn," Geotechnical Testing Journal,

ASTM, Vol. 3, No. 3, pp. 127-130.

67
ENERGY

RATIO

FOR

F(t)

=

Ej/E*

=

ENTHRU

=

ERj

Kovacs, W.D. (1982), "Results and Interpretation of SPT Practice Study,"

Geotechnical Testing Journal , ASTM, Vol. 4, No. 3, pp. 126-129.

Kovacs, W.D., Evans, J.C., and Griffith, A.H. (1977), "Towards a More

Standardized SPT," Proceedings , Ninth international Conference on Soil

Mechanics and Foundation Engineering, Tokyo, Japan, Vol. II, Paper 4-18,

pp. 269-276.

Kovacs, W.D., Salomone, L.A., and Yokel, F.Y. (1981), "Energy Measurement in

the Standard Penetration Test," Building Science Series 135 , U.S. Government

Printing Office, Washington, D.C., 99 pp.

Marcuson, W.F., III, and Bieganousky, W.A. (1977a), "Laboratoary Standard

Penetration Tests on Fine Sands," Journal of the Geotechnical Engineering

Division , ASCE, Vol. 103, No. GT6, June, pp. 565-588.

Marcuson, W.F., III, and Bieganousky, W.A. (1977b), "SPT and Relative Density

in Course Sands," Journal of the Geotechnical Engineering Division, ASCE,

Vol. 103, No. GT11 , pp. 1295-1309.

Palacios, A. (1977), "The Theory and Measurement of Energy Transfer During

SPT Test Sampling," Thesis Presented to the University of Florida at

Gainesville, Florida, in 1977, in partial fulfillment of the requirements

for the degree of Doctor of Philosophy, 391 p.

Robertson, P.K., Campanella, R.G. and Wightman, A. (1982), "STP-CPT

Correlations," Soil Mechanics Series No. 62, University of British Columbia,

Dept, of Civil Engineering, October, 19 p.

Schmertmann, J.H. (1978), "Use the SPT to Measure Dynamic Properties? - Yes,

But...!," Dynamic Geotechnical Testing , ASTM STP 654, American Society for

Testing and Materials, pp. 341-355.

Schmertmann, J.H. (1979), "Statics of SPT," Journal of the Geotechnical

Engineering Division , ASCE, Vol. 105, No. GT5, pp. 655-670.

Schmertmann, J.H. and Palacios, A. (1979), "Energy Dynamic of SPT," Journal

of the Geotechnical Engineering Division, ASCE, Vol. 105, No. GT8,

pp. 909-926.

Schmertmann, J.H. and Smith, T.V. (1977), "A Summary of SPT Energy Calibration

Services Performed for the Florida DoT Under Service Contact 99700-7150-010,"

Final Research Report 245*D73 , College of Engineering, University of Florida,

Gainesville, Florida, 21 pp. Appendices.

Seed, H.B. (1979), "Soil Liquefaction and Cyclic Mobility Evaluation for

Level Ground During Earthquakes," Journal of the Geotechnical Engineering

Division, ASCE, Vol. 105, No. GT2, pp. 201-255.

68
Seed, H.B., Idriss, I.M., and Arango, I (1983)", Evaluation of Liquefaction

Potential Using Field Performance Data," Journal of Geotechnical Engineering , ASCE, Vol. 109, No. 3, pp. 458-482.

Serota, S. and Lowther, G. (1973), Dicussion of "Accuracy of Relative Density

Measurements by Travenas, F. and La Rochelle, P. (1972), GEOTECHNIQUE,

Vol. XXIII, No. 2, pp. 301-303.

Timoshenko, S. (1934), Theory of Elasticity , 1st Ed., McGraw-Hill Book Co.,

New York, 416 pp.

Yoshimi, Y. and Tokimatsu, K. (1983) "SPT Practice Survey and Comparative

Tests," to be published in Soils and Foundations , Japanese Society of Soil

Mechanics and Foundation Engineers.

Youd, T.L. and Bennett, M.J. (1983), "Liquefaction Sites, Imperial Valley,

California," Journal of Geotechnical Engineering , ASCE, Vol. 109, No. 3,

pp. 440-457.

69
ENERGY

RATIO

FOR

F(t]

=

Ej/E*

=

ENTHRU

=

ERj
I!

Table A-l Tabulation of Field Data ER-^ , Percent from SPT Calibrator

Series 79 through 90

J Blow No. Test Series

79 80 81 82 83 84 85 86a 87 a 88 a 89a 90a

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (ID (12) (13)

1 50 56 42 55 56 54 77 75 58 73

2 51 — 53 42 — 55 — 69 51 65 53 65

3 50 51 50 44 64 57 — 142 48 65 59 56

4 49 52 46 47 54 56 — 91 45 57 49 62

5 50 55 48 44 — 60 37 65 41 62 59 53

6 50 54 55 48 55 63 47 54 75 81 49 64

7 49 50 55 47 55 58 46 42 44 60 64 68

8 47 46 58 35 — 58 46 101 45 69 55 53

9 45 50 63 46 55 55 49 81 55 63 55 116

10 48 50 51 54 58 50 41 96 91 65 65 55

11 48 52 45 38 — 53 44 59 76 69 91 47

12 51 50 62 28 75 49 34 52 47 61 48 52

13 48 49 49 44 54 46 46 57 42 57 76 '60 14 45 50 68 41 — 51 37 61 41 67 48 69

15 49 52 55 47 52 49 35 60 87 80 46 51

16 50 52 64 52 47 47 74 45 57 49 55

17 43 51 52 54 46 33 106 47 57 44 53

18 51 53 64 52 54 42 45 105 98 49 53

19 45 54 49 53 — 39 90 49 68 49 78

20 45 52 55 60 39 74 64 72 52 68

21 49 — 46 50 61 56

22 35 54 53 70 84

23 47 55 58

24 43 55 107

25 46 52 64

26 47

27 42

28 47

29 49

30 48

Average ER^ 47.2 51.8 54.5 43.1 55.6 53.6 41.4 72.9 58.7 67.4 55.9 64.3

Standard Deviation 3.4 2.3 6.7 6.1 5.8 4.9 5.2 23.7 19.4 10.1 11.3 16.7

Coef. of Variation 7.2 4.3 12.2 14.2 10.5 9.0 12.6 32.4 33.0 15.1 20.3 25.8

Operator B B C C D D D D D D D E Hammer S S S D S S D D D S S S

i. Erroneous readings observed. Interpretation given in table A. 4. The symbol — indicates data were not obtained.

A1
ENERGY

RATIO

FOR

F(t]

=

Ej/E*

=

ENTHRU

=

ERj

Table A-2 Tabulation of Field Data ER^ , Percent from SPT Calibrator

Series 91 through 100.1

l

I4

J

i

i

i

Test Series

Blow No. 91 92 93a 93 a 94 95 95 96 97 98 99 100.1

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (ID (12) (13)

1 63 51 55 94 57 44 45 41 49 48 40 50

2 60 51 115 102 67 47 47 41 49 48 46 49

3 56 50 87 92 50 48 49 43 44 45 47 51

4 58 54 59 99 45 45 50 47 47 47 49 48

5 59 50 122 75 52 45 42 43 45 45 49 52

6 62 30 57 82 58 47 50 46 44 46 49 51

7 59 33 53 59 59 49 45 46 44 44 47 51

8 68 49 55 56 58 41 45 45 47 44 48 49

9 61 49 53 114 61 45 49 43 47 43 46 50

10 64 49 38 89 51 43 49 45 47 43 49 48

11 67 50 40 52 56 44 47 45 47 43 47 47

12 63 50 140 66 52 45 44 45 48 46 50 48

13 66 55 82 71 52 42 44 47 45 43 50 45

14 67 39 106 56 65 46 45 46 48 46 49 47

15 65 51 109 82 57 45 44 46 46 46 49 50

16 76 46 62 73 62 48 45 48 48 42 48 49

17 63 51 90 86 49 48 45 45 46 42 47 49

18 56 29 65 45 45 44 46 45 42 47 49

19 54 49 69 48 46 44 47 47 42 46 49

20 70 51 121 51 46 49 46 51 43 45 50

21 78 62 62 45 42

22 54 103 45 43

23 57 82 49

24 64 55 45

25 64 66 45

26 114 43

27 90 47

28 104 48

29 81 45

30 98 49

Average ER^ 63.0 46.9 80.5 55.1 45.8 45.1 46.7 44.7 47.4 49.1

Standard Deviation 6.1 7.7 24.1 6.3 2.3 1.9 1.9 2.0 2.3 1.7

Coef. of Variation 9.6 16.4 29.9 11.4 5.0 4.3 4.0 4.5 4.8 3.4

Operator E E E E C C E E C E Hammer S S D D S S S S S S

i

A2
Table A-3 Tabulation of Field Data ER^ , Percent from SPT Calibrator

Series 100.2 through 100.10

1 Test Series

Blow No. 100.2 100.3 100.4 100.5 100.6 100.7 100.8 100.9 100.10

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)

1 57 40 52 52 45 48 31 43 52

2 56 33 51 52 51

3 56 32 49 50 51

4 55 33 52 52 50

5 55 33 50 50 52

6 53 32 49 51 52

7 57 33 51 50 47

8 56 31 52 52 48

9 55 30 48 51 49

10 55 — 51 49 49

11 56 33 47 50

12 31 — 50

13 30 48 51

14 35 49 52

15 47 52

Average ER^ 55.5 32.8 49.7 50.9 45 48 31 43 50.1

1 Standard Deviation 1.1 2.5 1.8 1.0 — — — — 1.8

Coef. of Variation 2.0 7.6 3.7 2.0 — — — — 3.6

Operator C C C F G G G G H

Hammer S S S S S S S S S

Turns 1.25 3.25 1.25 3.25
ENERGY

RATIO

FOR

F(t]

=

Ej/E*

=

ENTHRU

=

ERj

Table A-4 Tabulation of Reinterpretated Field Values of ER^

Percent from SPT Calibrator

Test Series

Blow No. 86 87 88 89 90 93 93

(1) (2) (3) (4) (5) (6) (7) (8)

1 54 * * 58 * 55 A

2 69 51 65 53 65 * A 3

* 48 65 59 56 A A 4 * 45 57 49 62 59 A

5 65 41 62 59 53 * A

6 54 * * 49 64 57 A

7 42 44 60 64 68 53 A

8

a 45 69 55 53 55 A

9 a 55 63 55 * 53 A 10 * a 65 65 55 38 A 11 59 a 69 * 47 40 A 12 52 47 61 48 52 * 59

13 57 42 57 — 60 * 56

14 61 41 67 48 69 * * 15 60 a — 46 51 A A 16 74 45 57 49 55 62 52

17 * 47 57 44 53 * 66

18 45 * * 49 53 65 71

19 * 49 68 49 — 69 56

20 74 64 * 52 68 A A

21 61 56 62 A 22 70 — A A 23 58 * 24 * 55

25 64 66

Average ER^ 59.8 47.4 62.8 52.8 58.1 57.5

Standard Deviation 9.6 6.1 4.5 6.1 6.5 8.4

Coef. of Variation 16.1 12.9 7.2 11.5 11.1 14.6

Operator D D D D E E

Hammer D D S S S D

Notes:

i

(

1

' The symbol indicates data was not obtained.

2 The symbol * indicates data not used as compressive wave reflection

i suspected by abnormally high field reading.

i

i

A4
Table A-5 Tabulation of Field Data ER^ , Percent from SPT Calibrator

Series 102-109

Blow No.

Test Series3

102 103 104 105 b 106AC 106BC 108 109

(1) (2) (3) (4) (5) (6) (7) (8) (9)

1 61 46 55 75 61 56

2 59 45 57 60 43 69 64 53

3 63 55 61 — 41 77 60 71

4 64 46 54 69 42 81 66 51

5 58 46 52 61 35 85 70 72

6 62 54 45 63 36 70 45 47

7 60 56 52 54 49 65 68 55

8 — 50 50 56 48 68 55 61

9 — 56 53 67 51 67 64 56

10 54 44 62 68 45 63 56 56

11 58 45 61 59 66 79

12 — 49 55 64 59 56

13 57 53 53 62 63 71

14 51 43 59 57 68 66

15 75 46 53 58 61 67

16 60 49 55 54 68 83

17 56 49 59 53 68 83

18 63 48 45 54 60 —

19 53 48 50 58 62 77

20 71 47 57 62 70 84

21 46 48

22 46

Average ER^ 60.3 48.6 53.7 60.4 43.3 72.0 62.7 65.5

Standard Deviation 6.0 4.0 5.1 5.4 5.5 7.2 6.1 12.0

Coef. of Variation 10.0 8.2 9.5 8.9 12.8 10.0 9.7 18.3

Operator I J K I I I I I Hammer S S S S S S D D

a. All tests conducted on a Mobile B61 Rig using 2 nominal turns using BW

upset wall unless noted otherwise.

b. A 2 foot section of BW parallel wall rod was inserted above the 40 foot

section of BW upset drill rod.

c. Series 106A-used 1 nominal turn of rope while 3 nominal turns of rope

around the cathead used in Series 106B.

A5
Table A-6 Tabulation of Field Data ER^ , Percent from SPT Calibrator

Series 110-119

Test Series3

Blow No. 110 111 112 113 1 14Ad

1 14B d 115 117 1 1

C (1) (2) (3) (4) (5) (6) (7) (8) (9) (10)

1 79 66 80 43 84 86 68 80

2 78 — 68 61 49 84 79 71 74

3 77 78 69 65 67 87 69 75 78

4 80 83 70 64 67 87 — 87 86

5 76 81 72 57 74 81 — 75 85

6 83 79 69 72 84 80 88 77

7 74 78 105 67 81 89 76

8 76 76 100 77 71 90 76

9 69 78 101 66 78 89 82

10 71 77 113 70 77 87 86

11 72 82 102 75 80 86 86

12 75 74 107 75 68 85 85

13 74 75 101 77 83 86 83

14 70 76 103 54 80 86 85

15 84 75 88 61 79 88 85

16 75 76 97 78 78 85 77

17 73 75 115 76 77 84 —

18 77 76 91 80 82 78 87

19 68 74 86 74 90 91

20 69 75 100 78 89 90

21 72 76 81 79 92

22 — 75 80 90

23 72 78 81

24 71 80

25 71

26 73

Average ER^ 74.4 77.0 91.2 71.9 60.0 84.5 79.3 84.4 81.7

Standard Deviation 4.2 2.6 16.4 8.1 13.3 2.3 5.8 6.6 4.4

Coef. of Variation 5.6 3.4 18.0 11.3 22.2 2.7 7.3 7.8 5.4

Operator K K J J J J K I J

Hammer S S S S S S S S S

a. Tests from 110 to 112 performed using a Long year HC 150 rig, 2 turns, using BW

upset wall rod; tests from 113 to 119 performed using a CME 75 rig, 2 turns

using BW upset wall rod unless noted otherwise. The cross-sectional area reported in the Sprague & Henwood catalog shows the BW upset rods to be 0.966

in^. The SPT Calibrator will not accommodate such a small area directly and a value of ”500" was used to set the device in step 3 of the calibration procedure. Subsequently, an error was found in the S&H catalog by NBS and the

correct cross-sectional area of the BW upset wall rods is 1.141 square inches.

Thus to correct the field data for the correct area, multiply each value by

446/500 or 0.932. The average values reported in table 3.3 have been corrected.

This table contains actual field data only .

b. Series 114A used 1 turn of rope while series 114b used 3 turns on rope around

the cathead.

c. A 2 foot section of BW parallel wall rod was inserted above the 40 foot section

of BW upset rods.

A6
Table A- 7 Tabulation of Field Data E% , Percent from SPT Calibrator

Series 120-130

Test Series3

Blow No. 120 121 122 123 127AU 127B U 127C° 128AC 128BC 128Cc 130°

CD (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12)

i

1 l 67 65 79 75 94 73 63 86 87

2 — 70 80 86 84 65 62 89 80

3 62 70 82 84 75 68 56 88 81

4 — 73 80 80 79 62 59 88 90

5 60 77 79 75 84 65 60 90 79

6 58 69 78 80 73 72 57 89 78

7 64 78 80 77 83 67 61 88 79

1 8 52 71 74 77 81 72 63 80 88

i 9 — 78 80 78 80 71 64 86 80

10 61 72 83 79 77 70 51 87 86

11 82 72 80 78 95

12 60 75 78 79 97

13 54 73 78 85 101

14 66 69 78 74 83

15 59 72 79 74 87

16 — 68 79 77 94

17 57 75 77 79 92

18 62 79 82 81 89

19 — 73 81 76 82

20 70 75 90 94

21 — 84

22 — 89

23 — 93

24 58 103

25 57 77 26 64 85

27 55 84

28 67 92

29 62 86

30 63 84

Average ER^ 61.7 72.5 79.4 79.1 81.0 68.5 59.6 87.1 79.3 60.9 87.3

Standard Deviation 7.2 3.7 2.8 3.6 5.9 3.7 4.0 2.8 5.0 4.3 6.8

Coef. of Variation 11.7 5.1 3.5 4.6 7.3 5.4 6.7 3.2 6.3 7.1 7.8

Operator L L M N L L L L L L L

Hammer S S S S S S S S S S S

a. All tests conducted using a Failing 1500 drilling rig using 2 nominal turns of rope around the

cathead and BW Sprague & Henwood upset wall rod unless stated otherwise. The cross-sectional area reported in the Sprague & Henwood catalog shows the BW upset rods to be 0.966 in^. The SPT

Calibrator will not accommodate such a small area directly and a value of "500" was used to set the

device in step 3 of the Calibration procedure. Subsequently, an error was found in the S&H catalog

by NBS and the correct cross-sectional area of the BW upset wall rods is 1.141 square inches. Thus

to correct the field data for the correct area, multiply each value by 466/500 or 0.932. The

average values reported in table 3.3 have been corrected. This table contains actual field data

onl£.

b. Series 127 A, B, & C, used 1, 2, and 3 nominal turns of rope, respectively.

c. Series 128 A, B, & C, used 1, 2, and 3, nominal turns of rope, respectively. A 2 foot section of

BW parallel wall was placed just below the load cell on top of 40 feet of BW upset wall.

d. A 2 foot section is included above the 40' rod, just below the load cell.

Table B-l Tabulation of Individual Fall Heights During Testing,

Series 82-98

Test Series

Blow No. 82 83 84 85 92 94 98

(1) (2) (3) (4) (5) (6) (7) (8)

1 31.0 29.75 30.13 33.13

2 31.25 30.25 30.00 — 30.50 30.37 29.75

3 32.75 31.25 30.50 30.5 28.50 30.37 29.50

4 32.25 28.5 29.63 30.5 30.25 30.50 30.13

5 33.0 30.75 30.13 30.25 28.75 30.62 29.13

6 31.88 30.25 30.50 31.0 30.00 28.37 29.37

7 — 30.75 29.75 29.75 30.50 30.75 28.87

8 — 30.75 30.00 31.13 28.75 29.63 28.75

9 — 31.25 29.75 30.50 30.37 30.37 29.63

10 — 32.25 29.75 30.50 29.5 29.00 28.63

11 30.38 33.25 31.00 29.50 30.53 30.5 28.75

12 30.00 29.25 29.50 30.13 28.50 31.37 27.5

13 30.75 30.75 28.13 29.75 31.50 30.00

14 30.87 30.25 29.25 30.00 29.25 30.37

15 30.75 31.25 29.25 30.37 30.00 30.00

16 30.75 31.00 29.50 30.5 29.75

17 31.0 30.75 30.25 29.5 30.63

18 31.25 30.75 29.50 32 30.0

19 31.00 26.75 29.25 30.00 31.50

20 30.87 29.50 30.00 29.63

21 28.75 29.63

22 30.50

23

24

25

Average Fall Height, in 31.4 30.8 29.8 30.1 30.0 30.3 29.2

Standard Deviation, in 1.0 1.0 1.0 0.5 0.9 0.8 0.5

Coef. of Variation, % 3.2 3.2 3.4 1.7 3.0 2.6 1.7

Operator C C D D E E E

Hammer D S S D S D S

B1
Table B-2 Tabulation of Individual Fall Heights During Testing,

Series 102-112

Test Series

Blow No. 102 103 104 105 106A 106B 108 109 111 112

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (ID

1 30.50 30.00 30.50 31.00 33.75 33.25 28.00 28.50 29.75 29.50

2 — 30.50 30.75 31.00 34.25 34.25 29.00 28.25 29.75 29.75

3 31.75 30.50 30.50 32.00 33.75 34.50 28.50 28.00 30.00 29.50

4 26.00 30.25 30.50 32.00 33.75 34.25 28.50 28.50 29.75 29.75

5 32.25 29.00 30.25 32.00 33.75 33.75 29.50 28.25 29.00 29.75

6 32.50 30.00 30.50 27.75 33.50 34.25 28.00 28.25 29.50 29.50

7 32.50 30.50 30.50 26.00 34.00 31.50 28.25 — 30.00 29.50

8 32.75 30.75 31.25 31.75 32.00 — 28.25 28.00 29.50 29.75

9 33.00 30.50 30.75 30.00 33.00 34.25 28.50 28.00 29.75 29.50

10 33.00 29.75 30.75 32.50 34.50 34.25 28.50 28.25 29.75 29.75

11 33.75 30.25 31.00 — 28.50 28.00 30.00 29.50

12 32.25 30.50 30.75 32.25 28.25 28.25 29.25 29.50

13 34.00 30.75 30.75 33.25 28.25 28.25 30.25 29.50

14 26.75 30.25 30.50 33.25 28.50 28.50 29.75 29.75

15 34.25 30.50 31.00 33.25 28.50 28.25 29.75 29.75

16 — 30.50 30.75 33.50 28.25 — 30.25 29.75

17 33.74 30.25 30.75 33.25 28.25 — 30.25 24.50

18 34.25 — 31.00 33.25 28.50 27.25 29.50 29.75

19 34.25 30.00 31.00 34.00 28.25 — 30.00 29.50

20 34.75 30.50 31.25 34.50 28.50 27.25 30.00 29.50

21 30.50 30.75 29.25

22 31.00 30.50

23

24

25

26

2728

29

30

Average Fall Height, in 32.3 30.3 30.8 31.9 33.8 33.6 28.4 28.1 29.8 29.6

Standard Deviation, in 2.4 0.4 0.3 2.2 0.9 0.7 0.3 0.4 0.4 0.1

Coef. of Variation, % 7.5 1.3 0.9 6.8 2.8 2.1 1.2 1.3 1.2 0.4

Operator I J K I I I 1 I K J Hammer S S S S S S D D S S

Turns 2 2 2 2 3 1 2 2 2 2

Note: Operator I used a "hold-drop” lifting procedure to perforin the SPT. His safety hammer usually hit

the underside of the anvil, surpassing the 30 in (76 cm) mark each time.

B2
Table B-3 Tabulation of Individual Fall Heights During Testing,

Series 113-123

Test Series

Blow No. 113 1 14A 114B 115 117 119 120 121 122 123

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (ID

1 29.75 29.75 30.00 30.00 30.25 29.50 30.00 29.50 29.75

2 29.50 29.75 30.00 29.25 29.75 29.75 31.50 28.50 29.00 31.00

3 29.50 29.75 30.00 29.50 29.75 29.75 27.25 28.75 30.00 31.75

4 30.00 29.75 29.50 30.00 — 29.50 28.00 29.50 30.25 31.00

5 29.50 31.25 29.75 30.00 30.00 29.25 27.00 30.75 30.75 29.75

6 29.50 29.50 30.50 — 29.75 26.25 29.25 30.75 30.50

7 29.75 29.75 30.00 29.75 28.25 31.50 30.25 29.25

8 29.25 31.00 30.00 29.75 — 29.25 29.75 30.00

9 29.75 30.00 30.00 29.75 — 31.25 31.00 28.25

10 29.50 30.50 30.00 30.00 30.25 29.25 31.00 31.25

11 29.50 30.25 — 29.50 33.50 28.75 29.75

12 29.50 29.75 30.50 30.25 30.25

13 29.75 30.00 26.00 28.50 30.75

14 29.50 30.25 28.75 28.75 30.00

15 29.50 28.00 29.75 30.50

16 — 26.50 30.25 27.00

17 29.75 27.25 30.25 29.50

18 29.75 28.25 31.50 31.25

19 27.50 26.50 30.50 30.50

20 29.75 28.50 29.00

21 30.00

22

23

24

25

26

2728

29

30

Average Fall Height, in 29.6 30.0 29.8 30.0 29.9 29.7 28.4 29.6 30.0 30.3

Standard Deviation, in 0.2 0.7 0.3 0.4 0.1 0.3 2.0 1.0 1.0 1.0

Coef. of Variation, % 0.2 2.2 0.8 1.5 0.4 0.9 7.2 3.3 3.2 3.5

Operator J J J K I J L L M N Hammer S S S S S S S S S S

Turns 2 3 1 2 2 2 2 2 2 2

B3
Table B-4 Tabulation of Individual Fall Heights During Testing

Series 127-130

Test Series

Blow No. 127A 127B 127C 128A 128B 128C 130

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (ID

1 30.75 30.00 29.75 29.50 29.75 29.25

2 31.00 32.25 24.75 30.00 27.75 — 26.50

3 29.25 28.50 30.25 29.50 29.25 — 22.75

4 29.75 30.25 26.75 30.50 30.00 29.75 28.50

5 30.50 29.75 28.50 31.00 25.25 29.75 24.25

6 27.25 31.50 29.25 30.50 28.25 32.25 28.75

7 30.00 29.50 32.00 29.75 25.00 29.25 28.50

8 30.50 27.75 31.25 29.75 27.50 29.75 28.25

9 29.25 30.25 30.50 29.75 30.00 28.75 29.25

10 28.50 29.25 — 30.00 30.25 29.00 28.75

11 29.50

12 29.00

13 25.75

14 30.50

15 29.00

16 29.25

17 30.25

18 29.25

19 —

20 30.25

21 28.75

22 27.25

23 31.25

24 29.75

25 27.00

26 27.25

27 27.75

28 31.00

29 28.75

30 29.0

Average Fall Height, in 29.7 29.9 29.2 30.0 28.3 29.8 28.5

Standard Deviation, in 1.2 1.3 2.3 0.5 1.9 1.2 1.9

Coef. of Variation, % 3.9 4.4 7.8 1.6 6.8 3.9 6.6

Operator L L L L L L L Hammer S S S S S S S

Turns 1 2 3 1 2 3 2

B4
1 NRC FORM

U.S. NUCLEAR REGULATORY COMMISSION

BIBLIOGRAPHIC DATA SHEET

1. REPORT NUMBER lAssignad by DDC)

NUREG/CR-3545

4. TITLE AND SUBTITLE (Add Volume No., if *>praprie»J

Comparison of Energy Measurements in the Standard

Penetration Test Using the Cathead and Rcpe Method

2. (Leave blank )

3. RECIPIENT S ACCESSION NO.

7. AUTHOR IS) William D. KovacSj Lawrence A. Salomone and

Felix Y. Yokel

5. DATE REPORT COMPLETED

MONTH 1 YEAR

July 1983

9. PERFORMING ORGANIZATION NAME AND MAILING ADDRESS (Include Zip Code

)

\ National Bureau of Standards

| Department of Commerce

i Washington, D. C. 20234

DATE REPORT ISSUED

MONTH | YEAR

November 1983

6. (Leave blank)

8. (Leave blank)

12. SPONSORING ORGANIZATION NAME AND MAILING ADDRESS (Include Zip Code

)

Division of Health, Siting and Waste Management

Office of Nuclear Regulatory Research

U.S. Nuclear Regulatory Commission

Washington, DC 20555

10. PROJECT/TASK/WORK UNIT NO.

11. FIN NO.B7457

13. TYPE OF REPORT 1 period COVERED (Inclusive dates) Final Report

15. SUPPLEMENTARY NOTES 14. (Leave olank)

16. ABSTRACT (200 words or less

)

Studies conducted on the Standard Penetration Test (SPT) and its present use in

engineering practice show that a wide variation in the use of different pieces of SPT

equipment, procedures and personnel results in a range of energy measured in the drill

rods from 30 to 85 percent of the standard SPT energy. The potential energy and kinetic

energy of the hammer were measured prior to impact, and the energy passing through the

drill rods was calculated from a force-time measurement in the rods. It was found that

safety (type) hammers tend to allow more kinetic energy to pass through the hammer-anvil

system than donut (type) hammers. The energy passing through the drill rods was calculated

by using a digital processing oscilloscope and an SPT Calibrator. Lessons learned in

evaluating the energy measurements by these two methods are discussed. The combined

effect of the drill rig used, the operator and his procedures, and the SPT equipment

should be considered when energy is to be evaluated. The variation of average energy

ratio within various drill rig models was found to be about as large as that among drill

rig models. It was therefore impossible to make a statistically significant estimate

of the reference energy which is representative of the average energy delivered in U.S.

practice.

17. KEY WORDS AND DOCUMENT ANALYSIS

calibration; donut hammer; drill rods; energy;

energy ratio; engineering practice; equipment;

field tests; hammers; in-si tu testing; safety

hammer; soil tests; SPT; test procedures.

17a DESCRIPTORS

17b. IDENTIFIERS/OPEN-ENDED TERMS

18. AVAILABILITY STATEMENT 19. SECURITY CLASS (This report) 21 NO OF PAGES

Unlimited Unclassified

20. SECURITY CLASS (Thu page)

unclassified

22 PRICE

S NRC FORM 335 ni-«1l
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. '
.
UNITED STATES

NUCLEAR REGULATORY COMMISSION

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