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GATE 2017 CE (CE1) – Question 20

Geotechnical Engineering · Shallow foundations: bearing capacity, combined footing, raft, settlement · 1 mark · Multiple choice

A strip footing rests on the ground surface of purely clayey soil with undrained cohesion $c_u$. Its ultimate bearing capacity is

  1. $2\pi c_u$
  2. $\pi c_u$
  3. $(\pi+1)c_u$
  4. $(\pi+2)c_u$

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Correct answer: (D) $(\pi+2)c_u$

Explanation

For undrained clay, $\phi=0$, so the bearing-capacity factors are $N_q=1$, $N_\gamma=0$, and $N_c=\pi+2$. At ground level the surcharge is zero. Thus $q_{ult}=c_uN_c=(\pi+2)c_u\simeq5.14c_u$, giving D for the ideal strip-footing solution.

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