About this tool Check the stability of gravity and cantilever retaining walls against sliding and overturning. Enter the wall geometry, soil properties, and the tool calculates Rankine active earth pressure, factors of safety, and concrete volume.
Two wall types are supported: gravity walls (mass concrete, rectangular section) and cantilever walls (reinforced stem on a base slab, including the weight of soil on the heel). Results are colour-coded red when factors of safety fall below the required minimums.
This is a preliminary sizing tool — iterate the dimensions until the FoS values are acceptable, then use the concrete volume to estimate material quantities. For detailed design, a full EC7 analysis including bearing capacity and settlement checks is required.
How to use this tool 1. Select wall type — gravity (mass concrete) or cantilever (reinforced with base).
2. Enter wall geometry — height, thickness/stem width, and base dimensions for cantilever walls.
3. Enter soil properties — unit weight and effective friction angle (φ'). Typical values are shown below the input.
4. Check the factors of safety — sliding ≥ 1.5 and overturning ≥ 2.0. If red, increase wall dimensions or base width and recalculate.
Technical information Ka = (1 − sin φ') / (1 + sin φ') — Rankine active earth pressure coefficient
Pa = ½ × Ka × γ × H² — active force per metre run
FoS sliding = W × tan(⅔φ') / Pa. FoS overturning = M_resist / M_overturn.
Required FoS: sliding ≥ 1.5, overturning ≥ 2.0 per BS 8002 / Eurocode 7. Base friction uses ⅔φ' as the interface friction angle (concrete on soil).
Limitations This is a preliminary stability check only. It does not check bearing capacity beneath the base, structural adequacy of the stem/base, or settlement. Full EC7 design is required for construction.
The Rankine method assumes a vertical wall face, horizontal backfill, and no wall friction. For inclined backfill or rough wall faces, Coulomb's method should be used instead.
Surcharge loading, water pressure behind the wall, and seismic loading are not included. These can significantly increase the active force and must be considered in the full design.
Revision history 12 May 2026: Initial release
Disclaimer This tool is provided for educational and general information purposes only. It is not a substitute for professional engineering advice, design or verification.
Diggy and its contributors are not licensed engineering consultants and no results generated by this tool should be used directly for construction, design or safety-critical decisions.
All values and outputs are based on published empirical correlations and should be independently checked and confirmed by a qualified geotechnical engineer before use.
By using this tool, you accept full responsibility for how you interpret and apply the information provided.
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