Consolidation MCQ with answer and solution

Concept

Consolidation of Soils

Formula

Cv = (Tv × d²) / t, Cv = k / (mv × γw), S = mv × H × δσ

Step-by-step solution

1. Review the statements regarding soil consolidation. 2. Identify that consolidation involves the expulsion of pore water from saturated cohesive soils (Statement 1 is correct) and Cv determines the rate of settlement (Statement 2 is correct). 3. Recognize that expulsion of air is compaction, not primary consolidation (Statement 3 is incorrect). 4. Select Option (a) as the correct choice.

Explanation

Option A ("1 and 2 only") is correct because:1. Statement 1 is correct: Consolidation is a time-dependent process where water is squeezed out from the voids of saturated clay/cohesive soil under sustained loading. 2. Statement 2 is correct: The Coefficient of Consolidation (Cv) directly determines how fast this water escapes and controls the rate of settlement over time. 3. Statement 3 is incorrect: Primary consolidation is caused by the expulsion of pore water, whereas the expulsion of air from soil voids is called compaction.

Shortcut

To remember the key facts about consolidation, use the phrase "Water for Consolidation, Air for Compaction": - Consolidation = Water out (time-dependent process in saturated soils; Cv controls the rate of settlement) - Compaction = Air out (expulsion of air from voids) Statement 3 is incorrect because primary consolidation expels pore water, not air.

Common mistake

A common mistake is confusing consolidation with compaction and assuming that primary consolidation involves the expulsion of air from soil voids rather than pore water. This leads students to incorrectly consider Statement 3 as correct and select Option D (or B/C) instead of Option A.