What are the bearing capacity values of different types of soils such as clay, sand, gravel, rocks etc.?

Hi, In gross bearing capacity, the gross load is taken. Loads from the superstructure, self-weight of the foundation, and overburden pressure are the gross loads. Gross bearing capacity value is not taken in design as it is very high. Safe bearing capacity is the bearing capacity value that neglectsRead more

Hi,

In gross bearing capacity, the gross load is taken. Loads from the superstructure, self-weight of the foundation, and overburden pressure are the gross loads. Gross bearing capacity value is not taken in design as it is very high.

Safe bearing capacity is the bearing capacity value that neglects the overburden pressure and stress due to the footing weight. It is obtained by considering the factor of safety, i.e. net load is taken into consideration. More detailed explanation is given below.

**GROSS BEARING CAPACITY OF SOIL (q _{u})**

- It is also called as Ultimate Bearing Capacity of Soil
- It is represented by q
_{u} - Minimum gross pressure or load on the soil that can cause shear failure of the soil just below the footing.
- Gross bearing capacity of the soil is defined based on gross load.
- Gross load includes: Loads from superstructure, self-weight of the foundation and overburden pressure.

**NET ULTIMATE BEARING CAPACITY OF SOIL (q _{nu})**

- Represented by q
_{nu} - Net ultimate bearing Capacity = Gross bearing Capacity – (Stress due to weight of the footing + Stress due to overburden or surcharge)
- As shown in below figure, the depth of footing is Df, if the density of footing and soil are same, equal to γ. Then, q
_{nu}= q_{u}– γDf

**SAFE BEARING CAPACITY OF SOIL**

- Safe Bearing capacity of soil is obtained after applying the factor of safety.
- It is divided into two:
- Safe Net Bearing Capacity
- Safe Gross Bearing Capacity

**Safe Net Bearing Capacity**is defined as the**net soil pressure**that can be safely applied to the soil considering shear failure alone. It is obtained as q_{ns}= Net Ultimate Bearing Capacity (q_{nu})/Factor of Safety, i.e. q_{ns }= q_{nu}/FS**Safe Gross Bearing Capacity or Safe bearing Capacity**is defined as the**maximum gross pressure**that soil can carry without shear failure. It is given by safe gross bearing capacity q_{s}= q_{ns}+ γDf

## aviratdhodare

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 (sandRead more

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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