Retaining Walls MCQ with answer and solution

Concept

Purpose of shear key in retaining wall

Formula

NONE

Step-by-step solution

1. Retaining walls must resist lateral earth pressure without experiencing sliding along the base soil. 2. A shear key is a concrete projection extending below the footing slab into the foundation base soil. 3. It mobilizes passive earth resistance in the soil to prevent sliding of the retaining wall. Answer: A

Explanation

A shear key is a projection below the base slab of a retaining wall designed to engage passive earth pressure against the surrounding soil. By mobilizing extra passive resistance, it significantly increases the factor of safety against horizontal sliding. It does not primarily affect the overturning or buckling behavior of the wall stem.

Why the other options are wrong

B) Overturning is prevented by adequate base width and wall proportions, not a shear key. C) Buckling is prevented by limiting the slenderness of the stem wall. D) Option A is correct because the shear key provides sliding resistance.

Shortcut

Shear key provides sliding resistance at the base.

Common mistake

Confusing sliding failure with overturning failure in retaining wall stability checks.