1. What is Factor of Safety?

The Factor of Safety (FoS) is a measure of structural reliability that compares the capacity of a structure to the actual loads it must withstand. For retaining walls, it specifically evaluates the stability against overturning.

2. How Does the Calculator Work?

The calculator uses the Factor of Safety equation:

Where:

• Resisting Moment — Sum of all moments resisting overturning (lb-ft)
• Overturning Moment — Sum of all moments causing overturning (lb-ft)

Explanation: A FoS greater than 1.5 is typically required for retaining wall stability, with higher values needed for critical structures.

3. Importance of Stability Calculation

Details: Proper calculation of retaining wall stability is essential for preventing structural failure, ensuring public safety, and meeting building code requirements.

4. Using the Calculator

Tips: Enter both resisting and overturning moments in lb-ft. Values must be positive numbers. The calculator will compute the ratio automatically.

5. Frequently Asked Questions (FAQ)

Q1: What is a good Factor of Safety for retaining walls?
A: Typically 1.5-2.0 for static loads, and higher for seismic zones or critical structures.

Q2: How do I calculate resisting and overturning moments?
A: Resisting moment comes from wall weight and soil above the heel. Overturning comes from lateral earth pressure.

Q3: Does this include sliding stability?
A: No, this only calculates overturning stability. Sliding stability requires separate calculation.

Q4: Should I consider surcharge loads?
A: Yes, any additional loads behind the wall should be included in the overturning moment calculation.

Q5: What about water pressure behind the wall?
A: Hydrostatic pressure must be considered if proper drainage isn't provided, as it significantly increases overturning forces.