Geotechnical Engineering

Retaining Wall Pressure Calculator

Estimate active retaining wall pressure, surcharge contribution, and drainage sensitivity.

Engineering schematic

Retaining wall load components

Static symbolic figure. Enter project values in the calculator fields below.

Cantilever retaining wall with active soil and surcharge pressure components, drainage layer and outlet, and a note that hydrostatic pressure requires a separate check if drainage is ineffective. — Symbols
H
retained height
Kₐ
active earth-pressure coefficient
q
uniform surcharge
γ, φ
backfill unit weight and friction angle

Result

Estimated active force: 848.03 force/length

0.307

0.47

3.255

Selected K

0.307

Base pressure

221.23

Total force

848.03

Resultant above base

Drainage multiplier

Adjusted total active force

848.03

Surcharge contribution

184.2

Step-by-step calculation

Rankine coefficients
$K_a=0.307,\quad K_0=0.47,\quad K_p=3.255$
Selected pressure coefficient
$K=0.307$
Soil-weight resultant
$P_\gamma=\frac{1}{2}(0.307)(120)(6)^2=663.68$
Surcharge resultant
$P_q=(0.307)(100)(6)=184.36$
Drainage screening adjustment
$P_{a,\mathrm{adjusted}}=848.03\times1=848.03$

What this means

Drained granular backfill is assumed; water pressure still needs a separate check where drainage may clog or fail.

Assumptions

Rankine pressure coefficients
Level drained granular backfill
No wall friction or seismic increment
Simplified drainage multiplier for screening only

Formula Used

P_a=\frac{1}{2}K_a\gamma H^2+K_aqH

Step-by-Step Example

A 6 ft drained wall with phi=32 deg, gamma=120 pcf, and 100 psf surcharge has about 859 lb/ft active force.

Engineering Notes

Check units, assumptions, boundary conditions, groundwater, drainage, and whether the simplified method is appropriate before using a result in any project decision.

FAQ

Does this include water pressure?

No. Undrained or clogged-drain conditions need separate hydrostatic pressure checks.