Cantilever Retaining Wall Stability (Overturning / Sliding / Bearing)
The three global-stability checks of a cast-in-place cantilever retaining wall.
Example
You enter
- Total wall height H (ft) 10
- Base width B, toe to heel (ft) 6
- Base slab thickness (ft) 1
- Stem thickness (ft) 1
- Toe length (ft) 1
- Soil unit weight (pcf) 110
- Concrete unit weight (pcf) 150
- Backfill friction angle phi (deg) 30
- Base friction coefficient mu 0.5
You get
- Sum v 6210
- Resisting moment (ft-lb/ft) 20565
- Overturning moment (ft-lb/ft) 6111.11
- Overturning FS (target 2.0) 3.37 (pass)
- Sliding FS (min 1.5) 1.69 (pass)
- Eccentricity e (middle third = B/6) 0.67 ft (in middle third)
- Q max 1731.02
- Q min 338.98
Checked against published worked examples from: CED Engineering (Weber).
Details, formula, and sources
ScopeThe restoring moments of the stem, base, and heel soil about the toe against the Rankine thrust's overturning moment, the base friction against sliding (both against the IBC 1807.2.3 minimum of 1.5), and the eccentricity-based toe / heel bearing pressures with a middle-third check. A 10 ft wall on a 6 ft base passes dry at 3.37 / 1.69 / 1,731 psf toe -- and the same wall fails sliding at 1.10 under a 300 psf surcharge (the surcharge drives the wall and is not counted as weight on the heel), the case that most often governs. Internal member design, passive toe credit, and seismic pressure are separate. A design aid, not a substitute for a licensed engineer's design.
Formula or tableFS_ot = Mr / Mo; FS_sl = mu x sum(V) / Pa; e = B/2 - (Mr - Mo)/sum(V); q_max,min = (sum(V)/B) x (1 +/- 6e/B); Rankine Pa = 0.5 Ka gamma H^2 + Ka q H.
Source and editionThe standard cantilever-retaining-wall global-stability checks as compiled in Das, Principles of Foundation Engineering, and NAVFAC DM-7.02, against the IBC 1807.2.3 minimum factor of safety of 1.5 for sliding and overturning, by name.
Free accessNAVFAC DM-7.02 is a free public US Navy design manual and the IBC is viewable through ICC's free online reader; the moment-ratio arithmetic is public.
What governsEstimate. AHJ and licensed professional govern.
API field namesh_ft, b_ft, t_base, t_stem, toe_ft, gamma_s, gamma_c, phi, mu, sum_v, mr, mo, fs_ot, fs_sl, ecc, q_max, q_min
- IBC 1807.2.3 targets minimum FS 1.5 against sliding and overturning (0.7 x seismic-included alternative not modeled); practice designs overturning to 2.0IBC 1807.2.3
- Rectangular idealization stem, base, and heel soil are rectangles; a tapered stem, a shear key, and passive toe credit are refinements the tool omits (conservative for passive)Das / NAVFAC DM-7.02
- Member design separate the stem and base are reinforced-concrete members with their own flexure / shear / development checks (see the ACI 318-19 tiles)ACI 318-19