How is the soil classified? What is the slope to be given for each type of soil while excavating?
The following is a short explanation of soil classifications. You should check the standard for detailed information regarding classifying soils
Type A soils
i) Cohesive soils that have an unconfined compressive strength of 1.5 tsf or greater.
E.g., clay, salty clay, sandy clay & clay loam
Type A soils cannot have or be subjected to the following:
Subjection to vibration from traffic, pile driving or similar conditions
Been previously disturbed
Or if it has been subjected to other factors that would change it’s classification
Type B soils
i) Cohesive soils that have an unconfined compressive strength greater than 0.5 tsf but less than 1.5tsf
E.g., angular gravel, silt, silt loam, sandy loam and previously disrobed soils except those which would be classified as Type C soil
Also includes soils that meet some of the requirements of Type A soils but is fissured or subject to vibration; or dry rock that is not stable.
Type C soils
i) Cohesive soils with an unconfined compressive strength of 0.5tsf or less
E.g. granular soils including gravel, sand and loamy sand
Also submerged soil or soil from which water is freely seeping or submerged rock that is not stable
ii) A natural solid mineral material that can be excavated with vertical sides and will remain intact while exposed.
Maximum allowable slopes
iii) Stable rock: vertical (90degrees)
Type A: ¾ :1 (53degrees)
Type B 1:1 (45degreed)
Type C : 1 ½ : 1 (34degrees)
½ : 1 (63 degrees ) slope is allowed for only short term excavations that are 12feet deep or le