Calculator
Example data
Use this dataset to validate the calculator outputs and learn typical magnitudes.
| Case | z | hw | γw | γsoil | q | u | σv | σ'v |
|---|---|---|---|---|---|---|---|---|
| SI sample | 8 m | 5 m | 9.81 kN/m³ | 18.5 kN/m³ | 12 kPa | 49.05 kPa | 160.00 kPa | 110.95 kPa |
| Imperial sample | 20 ft | 12 ft | 62.4 pcf | 115 pcf | 250 psf | 748.8 psf | 2,550 psf | 1,801.2 psf |
Note: σv is computed with a single soil unit weight for the full depth. For layered soil profiles, compute σv by summing layer contributions.
Formula used
- u = γw × hw (hydrostatic pore water pressure at depth hw below the water table).
- σv = γsoil × z + q (total vertical stress from self-weight and surface surcharge).
- σ'v = σv − u (Terzaghi effective stress).
- ru = u / σv (stress ratio for quick checks and comparisons).
This calculator assumes hydrostatic conditions. For seepage, pumping, or artesian flow, pore pressures may deviate from γw × hw.
How to use this calculator
- Select a unit system and keep all inputs consistent.
- Enter z to the point where stresses are needed.
- Enter hw as depth below the water table at that point.
- Provide γsoil for the soil above the point (use a weighted average if needed).
- Optional: Add surcharge q for surface loads.
- Press Calculate to see u, σv, and σ'v. Export the report if required.