Follwoing are the values of safe bearing capacity as per IS:1904–1978 –

Rocks –

a) hard sound rock – 330 t/m2 or 3240 KN/m2

b) leminated rock – 165 t/m2 or 1620 KN/m2

c) residual deposit of shattered and broken rocks- 90 t/m2 or 880 KN/m2

d) soft rock – 45 t/m2 or 440 KN/m2

Non Cohesive Soil (sand & gravel ) –

a) compact gravel, sand and gravel – 45 t/m2 or 440 KN/m2

b) compact and dry coarse sand – 45 t/m2 or 440 KN/m2

c) compact and dry medium sand – 25 t/m2 or 245 KN/m2

d) find sand – 15 t/m2 or 150 KN/m2

e) loose gavel or sand – 25 t/m2 or 245 KN/m2

f) loose and dry fine sand – 10 t/m2 or 100 KN/m2

Cohesive soil –

a) hard or stiff clay, soft shale – 45 t/m2 or 440 KN/m2

b) medium clay – 25 t/m2 or 245 KN/m2

c) moist clay and sand clay mixture – 15 t/m2 or 150 KN/m2

d) soft clay – 10 t/m2 or 100 KN/m2

e) very soft clay – 5 t/m2 or 50 KN/m2

f) black cotton soil , peat – by soil investigation

This is bit difficult to state like this. Generally, in fields, we deal with layered soil systems where in you need to work out settlement of each layer and then compare the same to allowable settlement of the subject structure. The allowable settlement for each structure in different and hence the criterion changes all the time.

More than shear criteria, the settlement criteria generally governs the safe bearing capacity of a soil. So, it is difficult to standardize the bearing capacity values in case of soils. May be, in the case of rock, you can standardize the values as the rock does not settle more than 3–4 mm.

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