Module 12
Retaining walls
The structure whose design is dominated by its loads — where the pressure depends on how much the wall moves, and where most failures are drainage failures.
What this module covers
- Derive the active earth pressure coefficient, and say what it assumes about movement
- Choose between active, at-rest and passive pressure from how the wall is restrained
- Carry out the three stability checks, and say which normally governs
- Explain why water is so much more severe than soil
- Design the stem as a cantilever, using the right height
- State plainly which quantities are geotechnical inputs rather than structural ones
Lessons
- 12.1
Earth pressure
Why the load on a retaining wall depends on the wall, and why water is the thing that actually breaks them.
Start lesson → Three checks before any reinforcement, and the one that usually governs.
Start lesson →
Module checkpoint
Check what you have taken in
6 questions
Question 1
A soil has φ = 25°. What is Ka?
Question 2
A basement wall is propped by the ground floor and the basement slab. Which pressure applies?
Question 3
A 4 m wall retains soil with Ka = 0.33 and γ = 18 kN/m³. What is the overturning moment about the base, in kNm/m?
Question 4
If that wall were 6 m instead of 4 m, by what factor does the overturning moment increase?
Question 5
A cantilever retaining wall fails its sliding check. Which change does NOT help?
Question 6
Water stands 3 m deep behind a wall. What is the horizontal force from the water alone, in kN/m? Take γw = 9.81 kN/m³.