Retaining Walls MCQ with answer and solution

Concept

Structural behavior of counterfort retaining wall toe

Formula

NONE

Step-by-step solution

1. A counterfort retaining wall consists of a vertical stem, base slab (toe and heel), and counterforts placed at regular intervals. 2. The counterforts tie the stem and heel slab together on the backfill side. 3. The toe slab projects forward from the vertical stem without counterfort support on top, thus acting as a cantilever slab fixed at the stem. Answer: A

Explanation

In a counterfort retaining wall, the toe slab projects horizontally outward from the front face of the vertical wall stem where counterforts are absent. Because it is fixed at the stem junction but completely free at its outer edge, it resists upward soil reaction pressure as a cantilever. Thus, the toe slab behaves structurally as a cantilever slab.

Why the other options are wrong

B) Continuous slab behavior occurs in the stem and heel slabs spanning across counterforts, not the toe slab. C) Simply supported slab behavior does not apply as the toe slab projects freely as a cantilever. D) Option A is correct because the toe slab acts as a cantilever.

Shortcut

In counterfort walls, the toe slab acts as a Cantilever, while stem and heel act as continuous slabs.

Common mistake

Confusing the toe slab, which acts as a cantilever slab, with the heel slab or stem, which act as continuous slabs.