The factor of safety due to sliding of the retaining wall is generally taken as
- A1
- B1.5Correct
- C2
- D4
Solution
Concept
Factor of safety against retaining wall sliding
Formula
NONE
Step-by-step solution
1. Retaining walls must be safe against sliding caused by lateral earth pressure. 2. Factor of safety against sliding is defined as the ratio of total resisting friction force to the driving horizontal force. 3. According to standard design codes such as IS 456, the minimum factor of safety against sliding is taken as 1.5. Answer: B
Explanation
Retaining walls must provide adequate resistance against horizontal sliding caused by lateral earth pressure from retained soil. Standard design codes require a minimum factor of safety of 1.5 against sliding under service loading conditions. This safety margin ensures the resisting frictional force along the base is 50 percent greater than the lateral sliding force, making option B correct.
Why the other options are wrong
A) A safety factor of 1 indicates critical equilibrium with zero margin against sliding failure. C) A safety factor of 2 is typically required against overturning or bearing failure rather than sliding. D) A safety factor of 4 is excessively conservative for evaluating sliding stability in retaining wall design.
Shortcut
Factor of safety for retaining walls: 1.5 for sliding, 2.0 for overturning.
Common mistake
Confusing the factor of safety against sliding (1.5) with the factor of safety against overturning (2.0).
Correct answer: B) 1.5