GATE 2016 CE (CE2) – Question 51
The soil profile at a site consists of a 5 m thick sand layer underlain by a c-φ soil as shown in figure. The water table is found 1 m below the ground level. The entire soil mass is retained by a concrete retaining wall and is in the active state. The back of the wall is smooth and vertical. The total active earth pressure (expressed in kN/m2) at point A as per Rankine's theory is _________
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Correct answer: 69.0 to 70.5
Explanation
Effective overburden is16.5·1+(19−9.81)·4+(18.5−9.81)·3=79.33kPa. At A use the lower layer’s Ka=tan²(45°−24°/2)=tan²33°. Effective active pressure is Ka·79.33−2·25sqrtKa≈0.9855kPa. Add pore pressure9.81·7=68.67kPa to get **69.655kPa** total.