Based on Terzaghi’s bearing capacity equation, there are three components in contribution to the bearing capacity:
(i) Surcharge pressure
Foundations are normally not placed directly on the ground level. Instead, they are installed at a depth below the existing ground level. The soil pressure arising from the depth of soils serves as a surcharge imposing a uniform pressure at foundation level. This is represented by ϒDfNq.
Where
ϒ = density of soils,
Df = Depth of foundation,
Nq = Bearing capacity factor
(ii) Self-weight of soils
The self-weight of soils contribute to the bearing capacity and is represented by 0.5ϒBNϒ
Where
ϒ = density of soils,
B = Width of foundation,
Nϒ = Bearing capacity factor
(iii) Shear strength
The shear strength of soils contributes to the bearing capacity and is represented by cNc.
Where
c = Shear strength or cohesion of soil,
Nc = Bearing capacity factor