Question

While designing a footing foundation which of the following bearing capacities should be considered?
1. Ultimate bearing capacity
2. Net bearing capacity
3. Safe bearing capacity
4. Any one of the above

Answer 1

Correct Answer - Option 3 : Safe bearing capacity

Concept:

The maximum pressure a soil can withstand without the occurrence of shear failure is called ultimate bearing capacity of soil (q_u).

The net pressure at the base of foundation in excess of initial overburden pressure which a soil can withstand without shear failure called net ultimate bearing capacity.

Q_nu = q_u­  - Overburden pressure(q)

When factor of safety is applied on the net ultimate bearing capacity, then it is called net safe bearing capacity (q_ns).

Safe bearing capacity: q_s = q_ns + Effective overburden pressure

While designing the foundation, safe bearing capacity is considered, because it is less than the true bearing capacity of soil and we are on safer side.