Retaining Wall Overturning & Sliding Check
Check the two classic failure modes of a gravity or cantilever retaining wall — tipping over and sliding forward — from the total weight, the horizontal earth thrust and the base geometry. The tool returns the overturning and sliding factors of safety per metre run of wall and flags whether each meets the usual minimum targets of 2.0 and 1.5.
Enter Values
Before you rely on this: First-pass guide only. Verify safety-critical or regulated work against the relevant standards, your project requirements and a qualified professional.
How to use this calculator
- Enter the total weight W of the wall plus the soil sitting on the heel, in kN per metre run.
- Enter the active horizontal thrust Pa (from a Coulomb or Rankine calculation), the wall height H and the base width B.
- Optionally adjust the base friction coefficient μ (default 0.5), then read the overturning and sliding factors of safety and their OK / review status.
How it works
Moments are taken about the toe of the base. The resisting moment is M_res = W·(B/2), assuming the weight acts at the mid-width of a uniform base, and the overturning moment is M_ot = Pa·(H/3), since the active thrust acts one-third of the height up the wall. The overturning factor of safety is M_res / M_ot and the sliding factor of safety is μ·W / Pa, comparing the frictional resistance at the base against the driving thrust.
Worked example
Worked example. For W = 120 kN/m, Pa = 40 kN/m, H = 4 m, B = 2.0 m and μ = 0.5: M_res = 120 × 1.0 = 120 kNm/m and M_ot = 40 × 4/3 = 53.33 kNm/m, so the overturning FoS = 120 / 53.33 = 2.25 (≥ 2.0, OK). The sliding FoS = 0.5 × 120 / 40 = 1.5 (≥ 1.5, OK).
Common mistakes
- Assuming the weight acts at B/2 when the real wall is not symmetric — a cantilever wall's centroid is offset, so use the true lever arm of each weight component for a final design.
- Leaving out the soil wedge on the heel, or forgetting surcharge and water pressure, which change both W and Pa.
- Treating passing these two checks as a complete design — bearing capacity, eccentricity (middle-third), settlement and global slope stability must also be verified.
Frequently asked questions
What factors of safety should a retaining wall achieve?
Common working-stress targets are a factor of safety of at least 2.0 against overturning and at least 1.5 against sliding, though the exact minimums depend on the code, whether passive resistance is included and the consequences of failure. Limit-state codes apply partial load and material factors instead of a single global factor, so check the standard that governs your project.
Does this tool include passive resistance at the toe?
No. The sliding check uses only base friction (μ·W) against the active thrust, which is conservative. Passive earth pressure in front of the toe can add resistance, but it is often discounted because the soil there may be removed or disturbed. If you rely on passive resistance, verify it separately and apply a suitable factor.
Related tools
- Gabion Wall Stability Check
- Coulomb Earth Pressure Calculator
- Footing Reinforcement Calculator
- Fatigue Life Estimator
- Factor of Safety Calculator
- Active Earth Pressure (Rankine) Calculator
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