Question

Two circular footings of diameters D and 3D are resting on the surface of same purely cohesive soil. The ratio of their ultimate bearing capacity is

• A. 1
• B. 9
• C. 1/3
• D. 3

Answer 1

The correct option is A 1

Ultimate bearing capacity of soil (Under circular footing)

$q_u=1.3C{N}_C+\gamma D_f{N}_q+0.5D\gamma N\gamma$

Since soil is purely cohesive

$N_c=5.7,N_q=1,N\gamma =0$

(Bearing Capacity Parameters)

D= Diameter of footing

$D_f=0$ (Depth of footing) (since footing is kept on surface)

$q_u=1.3C{N}_C$. independent of Diameter

So, ratio will be 1