Mechanical & Civil Engineering
Coulomb Earth Pressure (Sloping Backfill) Calculator
Calculate active earth pressure on a retaining wall using Coulomb's theory with a sloping backfill.
Your inputs
Change any value to update the result instantly.
Active earth pressure coefficient (Ka)
0.315
Total active force per meter
45.4 kN/m
Pressure at wall base
22.7 kPa
Resultant application height
1.33 m
What this calculator does
Coulomb Earth Pressure (Sloping Backfill) Calculator: Applies the standard civil and geotechnical relationship for this problem so the flow, pressure, settlement or capacity can be worked out from measured site inputs.
What your result means
The headline figure is the hydraulic or geotechnical quantity implied by your site inputs. Compare it against the design criteria in the applicable code before acting on it.
Formula and working
Ka = cos²(φ−θ) / [cos²θ×cos(δ+θ)×(1+√(...))²]
- 1
Collect the inputs
Soil internal friction angle (φ) = 32 deg; Wall friction angle (δ) = 15 deg; Backfill slope angle (β) = 10 deg; Wall back batter (θ) = 0 deg; Soil unit weight = 18 kN/m³; Wall height (H) = 4 m
- 2
Apply the formula
Ka = cos²(φ−θ) / [cos²θ×cos(δ+θ)×(1+√(...))²]
- 3
Result
Active earth pressure coefficient (Ka) = 0.315
Frequently asked questions
Symbols and assumptions
- frictionAngle
- Soil internal friction angle (φ) (deg)
- wallFriction
- Wall friction angle (δ) (deg)
- backfillSlope
- Backfill slope angle (β) (deg)
- wallBatter
- Wall back batter (θ) (deg)
- unitWeight
- Soil unit weight (kN/m³)
- wallHeight
- Wall height (H) (m)
- • Steady-state, single-phase conditions are assumed unless the page says otherwise.
- • Site inputs (soil properties, flow, roughness) come from the user's own survey or testing.
Sources and review
Reviewed 2026-09-22 · Next review 2027-09-22
- • This is an educational estimate for learning and checking, not a design deliverable.
- • Real design must follow the governing code or standard for your jurisdiction and be reviewed and signed off by a qualified engineer.
- • Safety factors, load combinations and material certification are the responsibility of the designer, not of this page.
Important limitation
This is an educational estimate based only on the values and formula shown. Verify current rates, rules, units, and professional standards before relying on the result. It is not personalized financial or investment advice.
Report a mistake or request an improvement
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