How is the soil classified? What is the slope to be given for each type of soil while excavating?


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:

Fissures

  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

Stable rock

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
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