California Code of Regulations › Title 8 - Industrial Relations › Division 1 - Department of Industrial Relations › Chapter 4 - Division of Industrial Safety › Subchapter 4 - Construction Safety Orders › Article 6 - Excavations › Appendix A - Soil Classification

Current through Register 2024 Notice Reg. No. 28, July 12, 2024
(a) Scope and application.
(1) Scope. This appendix describes a method of
						classifying soil and rock deposits based on site and environmental conditions,
						and on the structure and composition of the earth deposits. The appendix
						contains definitions, sets forth requirements, and describes acceptable visual
						and manual tests for use in classifying soils.
(2) Application. This appendix applies when a sloping or
						benching system is designed in accordance with the requirements set forth in
						Section 1541.1(b)(2) as a
						method of protection for employees from cave-ins. This appendix also applies
						when timber shoring for excavations is designed as a method of protection from
						cave-ins in accordance with Appendix C to this article, and when aluminum
						hydraulic shoring is designed in accordance with Appendix D. This appendix also
						applies if other protective systems are designed and selected for use from data
						prepared in accordance with the requirements set forth in Section
						1541.1(c), and the
						use of the data is predicated on the use of the soil classification system set
						forth in this appendix.
(b) Definitions.
Cemented soil. A soil in which the particles are held
						together by a chemical agent, such a calcium carbonate, such that a hand-size
						sample cannot be crushed into powder or individual soil particles by finger
						pressure.
Cohesive soil. Clay (fine grained soil), or soil with a
						high clay content, which has cohesive strength. Cohesive soil does not crumble,
						can be excavated with vertical side slopes, and is plastic when moist. Cohesive
						soil is hard to break up when dry, and exhibits significant cohesion when
						submerged. Cohesive soils include clayey silt, sandy clay, silty clay, clay and
						organic clay.
Dry soil. Soil that does not exhibit visible signs of
						moisture content.
Fissured. A soil material that has a tendency to break
						along definite planes of fracture with little resistance, or a material that
						exhibits open cracks, such as tension cracks, in an exposed surface.
Granular soil. Gravel, sand, or silt (coarse grained
						soil) with little or no clay content. Granular soil has no cohesive strength.
						Some moist granular soils exhibit apparent cohesion. Granular soil cannot be
						molded when moist and crumbles easily when dry.
Layered system. Two or more distinctly different soil or
						rock types arranged in layers. Micaceous seams or weakened planes in rock or
						shale are considered layered.
Moist soil. A condition in which a soil looks and feels
						damp. Moist cohesive soil can easily be shaped into a ball and rolled into
						small diameter threads before crumbling. Moist granular soil that contains some
						cohesive material will exhibit signs of cohesion between particles.
Plastic. A property of a soil which allows the soil to be
						deformed or molded without cracking, or appreciable volume change.
Saturated soil. A soil in which the voids are filled with
						water. Saturation does not require flow. Saturation, or near saturation, is
						necessary for the proper use of instruments such as a pocket penetrometer or
						sheer vane.
Soil classification system. A method of categorizing soil
						and rock deposits in a hierarchy of Stable Rock, Type A, Type B, and Type C, in
						decreasing order of stability. The categories are determined based on an
						analysis of the properties and performance characteristics of the deposits and
						the environmental conditions of exposure.
Stable rock. Natural solid mineral matter that can be
						excavated with vertical sides and remain intact while exposed.
Submerged soil. Soil which is underwater or is free
						seeping.
Type A soil. Cohesive soils with an unconfined,
						compressive strength of 1.5 ton per square foot (tsf) or greater. Examples of
						cohesive soils are: clay, silty clay, sandy clay, clay loam and, in some cases,
						silty clay loam and sandy clay loam. Cemented soils such as caliche and hardpan
						are also considered Type A. However, no soil is Type A if:
(1) The soil is fissured; or
(2) The soil is subject to vibration from heavy traffic,
						pile driving, or similar effects; or
(3) The soil has been previously disturbed; or
(4) The soil is part of a sloped, layered system where
						the layers dip into the excavation on a slope of four horizontal to one
						vertical (4H:1V) or greater; or
(5) The material is subject to other factors that would
						require it to be classified as a less stable material. Type B soil:
(1) Cohesive soil with an unconfined compressive strength
						greater than 0.5 tsf but less than 1.5 tsf; or
(2) Granular cohesionless soils including: angular gravel
						(similar to crushed rock), silt, silt loam, sandy loam and, in some cases,
						silty clay loam and sandy clay loam.
(3) Previously disturbed soils except those which would
						otherwise be classed as Type C soil.
(4) Soil that meets the unconfined compressive strength
						or cementation requirements for Type A, but is fissured or subject to
						vibration; or
(5) Dry rock that is not stable; or
(6) Material that is part of a sloped, layered system
						where the layers dip into the excavation on a slope less steep than four
						horizontal to one vertical (4H:1V), but only if the material would otherwise be
						classified as Type B.
Type C soil:
(1) Cohesive soil with an unconfined compressive strength
						of 0.5 tsf or less; or
(2) Granular soils including gravel, sand, and loamy
						sand; or
(3) Submerged soil or soil from which water is freely
						seeping; or
(4) Submerged rock that is not stable, or
(5) Material in a sloped, layered system where the layers
						dip into the excavation or a slope of four horizontal to one vertical (4H:1V)
						or steeper.
Unconfined compressive strength. The load per unit area
						at which a soil will fail in compression. It can be determined by laboratory
						testing, or estimated in the field using a pocket penetrometer, by thumb
						penetration tests, and other methods.
Wet soil. Soil that contains significantly more moisture
						than moist soil, but in such a range of values that cohesive material will
						slump or begin to flow when vibrated. Granular material that would exhibit
						cohesive properties when moist will lose those cohesive properties when
						wet.
(c) Requirements.
(1) Classification of soil and rock deposits. Each soil
						and rock deposit shall be classified by a competent person as Stable Rock, Type
						A, Type B, or Type C in accordance with the definitions set forth in paragraph
						(b) of this appendix.
(2) Basis of classification. The classification of the
						deposits shall be made based on the results of at least one visual and at least
						one manual analysis. Such analyses shall be conducted by a competent person
						using tests described in paragraph (d) below, or in other approved methods of
						soil classification and testing such as those adopted by the American Society
						for Testing Materials, or the U.S. Department of Agriculture textural
						classification system.
(3) Visual and manual analyses. The visual and manual
						analyses, such as those noted as being acceptable in paragraph (d) of this
						appendix, shall be designed and conducted to provide sufficient quantitative
						and qualitative information as may be necessary to identify properly the
						properties, factors, and conditions affecting the classification of the
						deposits.
(4) Layered systems. In a layered system, the system
						shall be classified in accordance with its weakest layer. However, each layer
						may be classified individually where a more stable layer lies under a less
						stable layer.
(5) Reclassification. If, after classifying a deposit,
						the properties, factors, or conditions affecting its classification change in
						any way, the changes shall be evaluated by a competent person. The deposit
						shall be reclassified as necessary to reflect the changed circumstances.
(d) Acceptable visual and manual tests.
(1) Visual tests. Visual analysis is conducted to
						determine qualitative information regarding the excavation site in general, the
						soil adjacent to the excavation, the soil forming the sides of the open
						excavation, and the soil taken as samples from excavated material.
(A) Observe samples of soil that are excavated and soil
						in the sides of the excavation. Estimate the range of particle sizes and the
						relative amounts of the particle sizes. Soil that is primarily composed of
						fine-grained material is cohesive material. Soil composed primarily of
						coarse-grained sand or gravel is granular material.
(B) Observe soil as it is excavated. Soil that remains in
						clumps when excavated is cohesive. Soil that breaks up easily and does not stay
						in clumps is granular.
(C) Observe the side of the opened excavation and the
						surface area adjacent to the excavation. Crack-like openings such as tension
						cracks could indicate fissured material. If chunks of soil spall off a vertical
						side, the soil could be fissured. Small spalls are evidence of moving ground
						and are indications of potentially hazardous situations.
(D) Observe the area adjacent to the excavation and the
						excavation itself for evidence of existing utility and other underground
						structures, and to identify previously disturbed soil.
(E) Observe the opened side of the excavation to identify
						layered systems. Examine layered systems to identify if the layers slope toward
						the excavation. Estimate the degree of slope of the layers.
(F) Observe the area adjacent to the excavation and the
						sides of the opened excavation for evidence of surface water, water seeping
						from the sides of the excavation, or the location of the level of the water
						table.
(G) Observe the area adjacent to the excavation and the
						area within the excavation for sources of vibration that may affect the
						stability of the excavation face.
(2) Manual tests. Manual analysis of soil samples in
						conducted to determine quantitative as well as qualitative properties of soil
						and to provide more information in order to classify soil properly.
(A) Plasticity. Mold a moist or wet sample of soil into a
						ball and attempt to roll it into threads as thin as 1/8 -inch in diameter.
						Cohesive material can be successfully rolled into threads without crumbling.
						For example, if at least a two inch length of 1/8 -inch thread can be held on
						one end without tearing, the soil is cohesive.
(B) Dry strength. If the soil is dry and crumbles on its
						own or with moderate pressure into individual grains or fine powder, it is
						granular (any combination of gravel, sand, or silt). If the soil is dry and
						falls into clumps which break up into smaller clumps, but the smaller clumps
						can only be broken up with difficulty, it may be clay in any combination with
						gravel, sand or silt. If the dry soil breaks into clumps which do not break up
						into small clumps and which can only be broken with difficulty, and there is no
						visual indication the soil is fissured, the soil may be considered
						unfissured.
(C) Thumb penetration. The thumb penetration test can be
						used to estimate the unconfined compressive strength of cohesive soils. Type A
						soils with an unconfined compressive strength of 1.5 tsf can be readily
						indented by the thumb; however, they can be penetrated by the thumb only with
						very great effort. Type C soils with an unconfined compressive strength of 0.5
						tsf can be easily penetrated several inches by the thumb, and can be molded by
						light finger pressure. This test should be conducted on an undisturbed soil
						sample, such as a large clump of spoil, as soon as practicable after excavation
						to keep to a minimum the effects of exposure to drying influences (rain,
						flooding), the classification of the soil must be changed accordingly.
(D) Other strength tests. Estimates of unconfined
						compressive strength of soils can also be obtained by use of a pocket
						penetrometer or by using a hand-operated shearvane.
(E) Drying test. The basic purpose of the drying test is
						to differentiate between cohesive material with fissures, unfissured cohesive
						material, and granular material. The procedure for the drying test involves
						drying a sample of soil that is approximately one inch thick and six inches in
						diameter until it is thoroughly dry:
1. If the sample develops cracks as it dries, significant
						fissures are indicated.
2. Samples that dry without cracking are to be broken by
						hand. If considerable force is necessary to break a sample, the soil has
						significant cohesive material content. The soil can be classified as an
						unfissured cohesive material and the unconfined compressive strength should be
						determined.
3. If a sample breaks easily by hand, it is either a
						fissured cohesive material or a granular material. To distinguish between the
						two, pulverize the dried clumps of the sample by hand or by stepping on them.
						If the clumps do not pulverize easily, the material is cohesive with fissures.
						If they pulverize easily into very small fragments, the material is
						granular.
Note: Authority cited: Section
						  142.3, Labor
						  Code. Reference: Section
						  142.3, Labor
						  Code.