Retaining wall stability: If W is the self-weight of the wall and P is the horizontal active earth pressure, what minimum factor of safety against sliding is generally adopted at working loads?

Introduction / Context:
Sliding resistance of retaining walls is checked by comparing available resisting forces with the driving horizontal earth pressure. Design guides commonly recommend a minimum factor of safety (FS) at service loads.

Given Data / Assumptions:

• Retaining wall on soil or rock foundation.
• Service load combinations (working state).
• FS_sliding = (frictional resistance + passive resistance, if any) / P.

Concept / Approach:

A typical target is FS ≈ 1.5 for sliding under service loads, unless otherwise required by project codes or seismic provisions.

Step-by-Step Solution:

Verification / Alternative check:

Many texts align on 1.5 for sliding and 1.5–2.0 for overturning (varies by standard). Ultimate limit-state methods convert to partial factors instead.

Why Other Options Are Wrong:

1.0 and 1.25 are too low; 2.0–2.5 may be overly conservative for routine static cases unless specified by the client or code.

Common Pitfalls:

Ignoring base key contribution; overestimating passive resistance without proper compaction; neglecting uplift water pressure.

Final Answer:

1.5