Stability of Slopes MCQ with answer and solution

Concept

Slope Stability Analysis of Earth Dams

Formula

N/A

Step-by-step solution

1. Consider the standard assumptions for slope stability analysis of homogeneous earth dams. 2. Note that potential failure surfaces are modeled as circular slip surfaces on both the upstream and downstream faces. 3. Select Option C as the correct answer.

Explanation

For stability analysis of a homogeneous earthen dam, potential slope failures are analyzed using circular arc failure surfaces (circular slip surfaces). These failures can occur on the upstream slope during rapid drawdown or on the downstream slope under steady seepage conditions, making a circular slip surface on both faces the standard assumption.

Shortcut

To remember failure surface assumptions for earth dams, use the rule "Both Sides Circle": - Circular: The failure surface for a homogeneous earth dam is always assumed to be a circular arc (circular slip surface). - Both Sides: Failure can happen on both the upstream face (during rapid drawdown) and the downstream face (during steady seepage).

Common mistake

A common mistake is selecting option D by incorrectly assuming that slope failure only occurs on the downstream face under steady seepage, forgetting that the upstream slope is critically vulnerable to failure during rapid drawdown. Another frequent mistake is selecting option A by confusing the phreatic line, which represents the upper surface of seepage flow, with the actual arc-shaped physical failure surface of the dam.