The bearing capacity of soil is influenced by various factors. The bearing capacity for cohesive and cohesionless soil is different. The physical features of foundation such as type of foundation, size of foundation, depth of foundation and shape of foundation significantly affect the bearing capacity. The amount of total and differential settlement is one of the main controlling factors for the bearing capacity of the soil. The relative density in the case of granular soil and consistency in the case of cohesive soil play a decisive role in influencing the bearing capacity. The physical as well as engineering properties of soils such as density, cohesion and friction, position of water table and original stresses are the other factors governing the soil bearing capacity.
Bearing Capacity of Granular Soils
In the case of sands the cohesion, c is absent. Hence, for sands, the bearing capacity equation is of the form:
Qult = γDfNq + 0.5γ BNγ ———- (1)
The Equation (1) shows that the bearing capacity in sands increases as the depth and width of foundation and soil unit weight, increase. The presence of water table at the surface or at the base of the foundation reduces the bearing capacity significantly.
Bearing Capacity of Cohesive Soils
In the case of cohesive soils the angle of internal friction ɸ is zero. Accordingly, Nγ = 0 and Nq = 1. Hence, for clays, the bearing capacity equation is of the form:
Qult = γDf + cNc ———- (2)
The Equation (2) shows that the bearing capacity in cohesive soil increases as the depth of foundation and soil unit weight, increase. The presence of water table at the surface or at the base of the foundation reduces the bearing capacity significantly. The bearing capacity is independent of the width of foundation.
- Influence of Water table on Bearing Capacity
- Hansen’s Bearing Capacity Theory
- Bearing Capacity from in Situ Tests
- Bearing Capacity of Mat Foundation
- Teng’s method | Meyerhof’s method | Bowles method for net safe bearing pressure