Free · IS 456:2000 Cl. 20 stability checks

Retaining Wall Design Calculator

Check a cantilever RCC retaining wall for overturning, sliding, bearing pressure and tension under the base, using Rankine earth pressure and surcharge. It sizes the base automatically and checks the stem thickness and steel.

Inputs (per metre run)

Wall & loading

Total height H (m)

Surcharge q (kN/m²)

Backfill & foundation soil

Unit weight γ (kN/m³)

Friction angle φ (°)

SBC (kN/m²)

Base friction μ

Concrete γc (kN/m³)

Base depth below front GL D_f (m)

Geometry (m)

Keep auto-sizing as I change the inputs

Base width B

Toe length

Base thickness

Stem top

Stem base

Materials (stem check)

Concrete

Steel

Stability checks

Required FoS 1.55 = 1.4 / 0.9 (IS 456 Cl. 20.1, 20.2)

Stem at base (limit state, IS 456)

Calculation details

Assumptions: level, well-drained, cohesionless backfill (Rankine, wall friction ignored), with weep holes or a drain so there is no water pressure. Passive resistance in front of the toe is ignored for sliding (conservative). The surcharge over the heel is ignored as a stabilising load but included for bearing pressure. For cohesive or sloping backfill, water pressure, or seismic loads, have a structural engineer carry out the design.

If sliding fails but everything else passes: add a shear key under the base (usually below the stem) rather than widening the base. The calculator sizes the key from the passive resistance of the soil in front, over the depth D_f plus the key. Make sure that soil will never be excavated.