GATE 2023 CE (CE2) – Question 42
The figure shows a vertical retaining wall with backfill consisting of cohesive-frictional soil and a failure plane developed due to passive earth pressure. The forces acting on the failure wedge are: P as the reaction force between the wall and the soil, R as the reaction force on the failure plane, C as the cohesive force along the failure plane and W as the weight of the failure wedge. Assuming that there is no adhesion between the wall and the wedge, identify the most appropriate force polygon for the wedge.
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Show answer and explanation
Correct answer: (C) Option C in the figure
Explanation
The wedge tends upward along the failure plane under passive loading, so cohesion acts down the plane. Weight is vertically downward; wall friction acts downward on the wedge, while the failure-plane reaction is inclined by friction from its normal. The wall reaction P points rightward and downward; the closing polygon with these directions is C.