GATE 2020 CE (CE2) – Question 61
The shown concrete dam holds 10 m static water. Uplift decreases linearly from full hydrostatic head at heel to zero at toe. Dam–soil friction coefficient is 0.45; concrete and water unit weights are 24 and 9.81 kN/m³. Find minimum base width B preventing sliding (m), to two decimals.
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Correct answer: 15 to 16
Explanation
Per metre dam length, weight is $W=120B$ kN and uplift $U=49.05B$ kN. Horizontal water thrust is 490.5 kN. No sliding requires $0.45(W-U)\ge490.5$. Thus $B\ge490.5/[0.45(120-49.05)]=\mathbf{15.36}$ m.