Retaining & slopes · Earth pressures
Seismic earth pressure (Mononobe–Okabe) calculator
Static and seismic active coefficients, thrusts and overturning moment on a retaining wall.
Standard: Mononobe–Okabe · Seed & Whitman (1970) 0.6H increment
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Inputs in the worked example
The live calculator starts with these values; change any of them and every result, check and diagram updates instantly.
| Input | Value | Unit |
|---|---|---|
| Wall height | 5 | m |
| Backfill γ | 19 | kN/m³ |
| Backfill φ′ | 32 | ° |
| Wall friction δ | 16 | ° |
| Backfill slope β | 0 | ° |
| Wall back inclination θ (from vertical) | 0 | ° |
| Horizontal coefficient kh | 0.1 | |
| Vertical coefficient kv | 0 |
Worked example — results
| Result | Value | Unit |
|---|---|---|
| Seismic inertia angle ψ = atan(kh/(1 − kv)) | 5.71 | ° |
| Static KA (Coulomb) | 0.278 | |
| Seismic KAE | 0.342 | |
| Static thrust PA | 66.1 | kN/m |
| Total seismic PAE | 81.2 | kN/m |
| Increment ΔPAE (at 0.6H) | 15.1 | kN/m |
| Overturning moment about base | 155.4 | kNm/m |
| Limit kh (φ − β = ψ) | 0.625 |
- ✓ kh below limiting value
Method, formulas and assumptions
- ψ = atan[kh/(1 − kv)]
- KAE = cos²(φ − θ − ψ) / {cosψ·cos²θ·cos(δ + θ + ψ)·[1 + √(sin(φ + δ)sin(φ − β − ψ)/(cos(δ + θ + ψ)cos(β − θ)))]²}
- PAE = ½γH²(1 − kv)KAE; static part at H/3, increment at 0.6H
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For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.