Soil Classification (2)
For the design of sloping or benching systems, the Occupational Safety and Health Administration (OSHA) classifies soils from excavation operations as presented in the table below.
The soil classification, according to [OSHA 29 CFR 1926 Subpart P App A], are based on the definitions in whole or in part, the following; American Society for Testing Materials (ASTM) Standards D653-85 and D2488; The Unified Soils Classification System; The U.S. Department of Agriculture (USDA) Textural Classification Scheme; and The National Bureau of Standards Report BSS-121.
Table:
Classification of soil and rock deposits based on site and environmental conditions, and on the structure and composition of the earth deposits [OSHA 29 CFR 1926 Subpart P App A]
| Soil or Rock Type | Soil Description |
|---|---|
| Stable Rock | Natural solid mineral matter that can be excavated with vertical sides and remain intact while exposed. |
| Type A | Cohesive soils with an unconfined compressive strength of 1.5 ton per square foot (tsf) (144 kPa) or greater. Examples of cohesive soils are: clay, silty clay, sandy clay, clay loam and silty clay loam and sandy clay loam. |
| Type B |
Cohesive soils with an unconfined compressive strength greater than 0.5 ton per square foot (tsf) (48 kPa), but less than 1.5 tsf (144 kPa) OR
Granular non-cohesive soils including: angular gravel (similar to crushed rock), silt, silt loam, sandy loam and in some cases silty clay loam and sandy clay loam OR
Dry rock that is not stable
|
| Type C |
Cohesive soils with an unconfined compressive strength of 0.5 ton per square foot (tsf) (48 kPa) or less OR
Granular soils including gravel, sand and loamy sand OR
Submerged soil or soil from which water is freely seeping OR
Submerged rock that is not stable OR
Material in a sloped, layered system where the layers dip into the excavation or a slope of four horiozntal to one vertical (4H:1V) or steeper.
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