GATE 2020 CE (CE1) – Question 57
Upward water flow passes through 2.5 m saturated sand in the shown tank. Sand void ratio is 0.58, specific gravity 2.7 and water unit weight 10 kN/m³. Find effective stress at A, 1 m above the base (kPa), to two decimals.
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Correct answer: 8.7 to 9.3
Explanation
Point A is 1.5 m below sand top. Submerged unit weight is $(G_s-1)\gamma_w/(1+e)=17/1.58=10.7595$ kN/m³. Upward gradient is $i=1.2/2.5=0.48$. Thus $\sigma_A^{\prime}=1.5(10.7595-0.48\cdot10)=\mathbf{8.94}$ kPa.