Question Bank • QB_EXP_SWCE_COM_002 MCQ • 1 Mark

Section 4: Soil and Water Conservation Engineering

Soil Compaction, Consolidation & Earth Pressures

Subtopic: Consolidation settlement formula

Question Statement:

The ultimate primary consolidation settlement $S_c$ of a normally consolidated clay layer of initial thickness $H_0$ and initial void ratio $e_0$ subjected to an effective stress increment $\Delta \sigma'$ is given by:

Options:

  • (A) $S_c = \frac{C_c H_0}{1 + e_0} \log_{10} \left( \frac{\sigma_0' + \Delta \sigma'}{\sigma_0'} \right)$
  • (B) $S_c = \frac{C_c H_0}{1 - e_0} \ln \left( \frac{\sigma_0' + \Delta \sigma'}{\sigma_0'} \right)$
  • (C) $S_c = C_c H_0 (1 + e_0) \log_{10} \left( \frac{\sigma_0'}{\Delta \sigma'} \right)$
  • (D) $S_c = \frac{H_0}{C_c (1 + e_0)} \left( \frac{\Delta \sigma'}{\sigma_0'} \right)$

Answer Key:

A

Step-by-Step Solution & Explanation

From Terzaghi's 1D consolidation theory, change in void ratio is $\Delta e = C_c \log_{10}\left(\frac{\sigma_0' + \Delta \sigma'}{\sigma_0'}\right)$. Since settlement $S_c = \frac{\Delta e}{1 + e_0} H_0$, substituting yields: $S_c = \frac{C_c H_0}{1 + e_0} \log_{10} \left( \frac{\sigma_0' + \Delta \sigma'}{\sigma_0'} \right)$.
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