The critical slip circle in a slope of saturated clay will always be a toe circle if slope angle is
- A> 53°Correct
- B< 53°
- C> 30°
- Dnone of these
Solution
Concept
Critical Slip Circle in Slope Stability
Formula
No mathematical formula exists for this conceptual rule; slope stability analysis uses Taylor's stability number equation: Sn = c / (γ × H).
Step-by-step solution
1. Identify the critical slope angle condition: For slopes in saturated clay, if the slope angle is greater than 53° (i.e., \> 53°), the critical failure plane always forms a toe circle. 2. Match with the options: Option A (\> 53°) represents this condition. 3. Select Option A as the correct answer.
Explanation
When the slope angle is steeper than 53°, the failure surface is forced to pass directly through the toe of the slope, making the critical failure plane always a toe circle. For flatter slopes (less than 53°), the critical slip circle can be a toe, slope, or base circle depending on the location of hard underlying strata.
Shortcut
Remember "Steep > 53° = Toe Circle": If the slope angle is steep (greater than 53°), the failure always passes through the toe.
Common mistake
Many students confuse the inequality sign and select option B (< 53°), mistakenly believing that toe circles occur for flatter slopes rather than steeper slopes (> 53°).
Correct answer: A) > 53°