Civil Engineering > GATE 2026 SET-1 > Bearing Capacity
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/m3 and undrained cohesion of soil as 20 kN/m2.
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).
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).
Correct : 13.16%
For a strip footing on pure clay (φ = 0) using Terzaghi''s theory with Nc = 5.7, Nq = 1, Nγ = 0:
GWT far below founding depth:
qu = 5.7c + γDf = 5.7 × 20 + 20 × 1.5 = 114 + 30 = 144 kN/m²
qnet,u = 144 − 30 = 114 kN/m²
GWT rises to ground surface:
Effective unit weight γ'' = γsat − γw = 20 − 10 = 10 kN/m²
Effective overburden q'' = γ'' × Df = 10 × 1.5 = 15 kN/m²
qu'' = 5.7c + q'' = 114 + 15 = 129 kN/m²
qnet,u'' = 129 − γDf = 129 − 30 = 99 kN/m²
Percentage change in net ultimate bearing capacity:
% change = (114 − 99)/114 × 100 = 15/114 × 100 = 13.16%
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