Question

The net ultimate bearing capacity of a Purely cohesive soil

1. Depends on both, width and depth of footing
2. Depends on only width of footing
3. Depends on only depth of footing
4. Is independent of both, depth and width of footing

Answer 1

Correct Answer - Option 4 : Is independent of both, depth and width of footing

Explanation:

The ultimate bearing capacity of any soil is given as

Q = CNc + qNq + ½ BγNγ

Note:

For purely cohesive soil (Clay)

ϕ = 0, Nc = 5.7, Nq = 1, Nγ = 0

Ultimate bearing capacity, Qu = 5.7C + q

Net ultimate bearing capacity, Qnu = Qu - q = 5.7C

Net ultimate bearing capacity of a foundation placed on purely cohesive soil is independent of width and depth of footing (as Nγ = 0).

Net ultimate bearing capacity is nearly unaffected by the rise of the water table to ground level (GL).