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Civil & Structural Geotechnical Design guide Calculate a value

Checking a retaining wall will not overturn, slide or sink

The three limit states every retaining wall must satisfy, and which one usually fails first on a narrow base.

The engineering question

A wall looks adequate but the ground behind it is pushing it over. Which check does it fail first, and how do you fix the right one?

Worked example

The figures below were produced by running the Retaining Wall Stability Calculator with the same inputs — during the build, from its authoritative engine.

Results
Active earth pressure coefficient 0.3333 Ka
Active thrust 48 kN/m
Factor of safety — overturning 0.1477 –
Factor of safety — sliding 0.0955 –
Factor of safety — bearing 0.8377 –
Maximum bearing pressure 179.0667 kPa
Assessment Not stable: FS(o) 0.15, FS(slide) 0.10, FS(bearing) 0.84. Widen the base or drain the backfill.
  1. Compute the active thrust from the retained soil and any surcharge.
  2. Resisting moment is the wall weight acting about the toe; overturning moment is the thrust acting at its own lever arm.
  3. Check sliding with base friction of two thirds of φ, then check bearing pressure at the toe.

Sanity check

On a narrow base overturning usually governs before sliding. Widening the base fixes overturning; adding a toe key fixes sliding.

Tools for this problem

These are the EngiMetric calculators that compute the numbers in this topic. Each one shows its formula, its units and its limits rather than returning a bare result.

Engineering review required

This topic supports professional engineering work; it does not replace a sealed design. The result depends on site data, the governing standard and engineering judgement, and should be confirmed by a competent engineer before it is built.

References & standards

  • BS EN 1997-1 — retaining structures
  • GECP 7 / CIRIA C580 — design of retaining walls

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