Engineering
Retaining Wall Preliminary Design Calculator
Estimate Rankine active pressure for level drained cohesionless backfill, add uniform surcharge thrust, and compare calculated sliding and overturning factors with the entered requirements before reviewing resultant and base pressure.
Rankine active pressure coefficient Ka-
Triangular active earth force (kN/m)-
Uniform surcharge earth force (kN/m)-
Total horizontal driving force (kN/m)-
Overturning moment about toe (kN m/m)-
Total stabilizing vertical weight (kN/m)-
Resisting moment about toe (kN m/m)-
Base-friction sliding resistance (kN/m)-
Sliding safety factor-
Overturning safety factor-
Sliding safety-factor margin-
Overturning safety-factor margin-
Governing entered safety-factor margin-
Base resultant location from toe-
Absolute eccentricity from base center-
Eccentricity divided by B over 6-
Maximum linear base pressure-
Minimum linear base pressure-
Decision view
Active thrust and toe-moment stability diagram
Active thrust and toe-moment stability diagramTriangular soil thrust and uniform-surcharge thrust act at different heights; wall and heel-soil weights create resisting toe moments before sliding, overturning, and base-resultant checks.
Exact scenario comparisonDrained soil friction angle phi (degrees) changes while all other entered assumptions remain constant.
| Drained soil friction angle phi (degrees) | Rankine active pressure coefficient Ka | Triangular active earth force (kN/m) | Uniform surcharge earth force (kN/m) | Total horizontal driving force (kN/m) | Overturning moment about toe (kN m/m) | Total stabilizing vertical weight (kN/m) | Resisting moment about toe (kN m/m) | Base-friction sliding resistance (kN/m) | Sliding safety factor | Overturning safety factor | Sliding safety-factor margin | Overturning safety-factor margin | Governing entered safety-factor margin | Base resultant location from toe | Absolute eccentricity from base center | Eccentricity divided by B over 6 | Maximum linear base pressure | Minimum linear base pressure |
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How to use Retaining Wall Preliminary Design Calculator
- Enter soil and retained-height assumptions.
- Enter wall and heel-soil weights with centroids from the toe.
- Enter required sliding and overturning factors, then review their margins together with middle-third and base-pressure results.
Calculator guide
Understanding Retaining Wall Preliminary Design Calculator
A preliminary retaining-wall stability check must keep horizontal thrusts, vertical weights, toe moments, and base pressure on a consistent one-metre wall strip.
Detailed calculation process
Detailed retaining-wall stability calculation
The default case resolves the active thrust system and the base resultant.
General formula: K_a=(1-sin(phi))/(1+sin(phi))P_s=0.5gamma H^2K_aP_q=qHK_aM_o=P_sH/3+P_qH/2FS_s=mu W/(P_s+P_q)FS_o=M_r/M_omargin_s=FS_s-FS_s,reqmargin_o=FS_o-FS_o,req Triangular soil and rectangular surcharge pressure diagrams create distinct forces and lever arms.
What each symbol means
Worked substitution with the default inputs
The governing entered safety-factor margin is 0.527, and the average of maximum and minimum base pressures remains 62.5 kPa, equal to 150/2.4.
Worked situations
Practical examples
- Triangular soil thrust acts at H/3 above the base.
- Uniform surcharge thrust acts at H/2 and must not share the soil thrust lever arm.
Better inputs
Useful tips
- Use forces and moments per metre of wall.
- Add water pressure separately in a full design.
- Check bearing capacity with project geotechnical data.
Before relying on the result
Limitations and common mistakes
- Water, seismic action, cohesion, and sloping backfill are excluded.
- Passive resistance is not credited.
- Global stability, settlement, and reinforcement design are outside scope.
Reference
Key terms
- Ka
- Rankine active earth-pressure coefficient.
- Toe
- Front edge of the footing used as the moment reference.
- Safety-factor margin
- Calculated factor minus the entered required factor; a negative value is a shortfall.
- Middle third
- Base region where a linear compression-only resultant has eccentricity no greater than B/6.
Important note
A qualified engineer must include drainage, geotechnical capacity, global stability, structure, and governing load factors.
Frequently asked questions
Why is wall length absent?
Every force and moment is calculated per metre of wall.
What does negative minimum pressure mean?
The linear full-contact assumption predicts tension and the footing must be re-evaluated.
Can friction coefficient equal soil friction angle?
Not automatically; use an interface value supported by the project design.