Question

The inclination of failure plane with horizontal in passive case behind a Retaining wall with smooth vertical with sand Backfill having angle of shearing resistance of \( ϕ = 30^\circ \) is ___

• A. \( 62^\circ \)
• B. \( 56^\circ \)
• C. \( 28^\circ \)
• D. \( 39^\circ \)

Hint:

For passive failure behind smooth walls, the failure plane angle is \( 45^\circ + \frac{\phi}{2} \).

Answer 1

The Correct Option is D

For passive failure behind a retaining wall, the angle of failure plane is \( 45^\circ + \frac{\phi}{2} \). Given that \( \phi = 30^\circ \), the angle of inclination of the failure plane becomes: \[ 45^\circ + \frac{30^\circ}{2} = 45^\circ + 15^\circ = 39^\circ \] Hence, the correct answer is \( 39^\circ \).