GATE 2026 CE (CE1) – Question 59
A shallow strip footing of width 2 m is embedded at a depth of 1.5 m below the ground surface in a homogeneous pure clay with an angle of internal friction zero. Consider unit weight of soil as 20 kN/m$^3$ and undrained cohesion of soil as 20 kN/m$^2$.
Due to rise of ground water table from far below the founding depth to the ground surface in monsoon season, the magnitude of percentage change in the net ultimate bearing capacity as per Terzaghi's theory is ____________________ (*rounded off to two decimal places*).
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Correct answer: -0.01 to 0.01
Explanation
For $\phi = 0$, Terzaghi's factors are $N_c = 5.7$, $N_q = 1$ and $N_\gamma = 0$. The net ultimate bearing capacity is $q_{nu} = q_u - \gamma D = cN_c + \gamma D(N_q - 1) = 20 \times 5.7 = 114$ kPa. The unit weight only appears through $\gamma D(N_q - 1)$, which is zero. So raising the water table does not change the net capacity, and the change is 0.00 percent.