Consolidation MCQ with answer and solution

Concept

Constrained Modulus of Soil

Formula

M = Δσ'v / Δεv

Step-by-step solution

1. Identify the formula for constrained modulus: M = Δσ'v / Δεv, where Δσ'v is vertical effective stress change and Δεv is vertical strain under one-dimensional loading. 2. Recall that the consolidation test (oedometer test) measures one-dimensional consolidation with zero lateral strain. 3. Match the test that provides the required stress and strain parameters to Option C: Consolidation test.

Explanation

The constrained modulus measures a soil's resistance to compression under one-dimensional loading where lateral expansion is prevented. A laboratory consolidation test (also known as an oedometer test) applies vertical pressure while keeping the soil laterally confined, directly measuring this stress-strain relationship.

Shortcut

Remember "Con - Con": Constrained modulus comes from the Consolidation test (since both involve lateral confinement).

Common mistake

Many students confuse the constrained modulus with unconfined modulus or elastic modulus and select Option B (UCS test), or confuse consolidation with compaction and choose Option D (Compaction test), forgetting that constrained modulus requires the zero-lateral-strain condition provided specifically by a consolidation test.