Structural & Geotechnical
Retaining Wall Stability
Cantilever retaining wall factor of safety against overturning and sliding, from Rankine active earth pressure.
Retaining Wall Stability
This calculator checks the overturning and sliding stability of a cantilever retaining wall using Rankine active earth pressure theory. It idealizes the wall as a standard L-shaped cantilever section — footing, stem, and heel — and sums the resisting weight of the concrete and retained soil against the overturning thrust of the active earth pressure wedge.
Overturning stability compares the resisting moment of the wall's self-weight and heel soil (about the toe) against the overturning moment of the active earth pressure. Sliding stability compares the base friction resistance against the horizontal component of that same earth pressure, conservatively ignoring any passive resistance in front of the toe.
Ka = tan²(45° − φ/2) Pa = 0.5 · Ka · γ · H²
FS_overturning = ΣM_resisting / ΣM_overturning (about toe)
FS_sliding = (ΣV · μ) / Pa [min: OT ≥ 2.0, sliding ≥ 1.5]
A 9-ft cantilever wall (1-ft footing, 1-ft stem, 6-ft base with a 1.5-ft toe) retaining φ = 30° backfill at 120 pcf develops an active thrust of Pa = 1,620 lb/ft. Against a total wall-plus-soil weight of 5,460 lb/ft, the overturning check gives FS = 3.99 (≥ 2.0 required) and, at a base friction coefficient of 0.5, the sliding check gives FS = 1.69 (≥ 1.5 required) — both comfortably adequate for this geometry.
Retaining Wall Stability Calculator
Cantilever L-wall · Rankine active pressure · imperial units