Calculator Inputs
Choose a method, enter values, and submit. The calculator uses a responsive three-column form on large screens, two columns on medium screens, and one column on mobile.
Example Data Table
| Case | Input Summary | Output Focus | Typical Use |
|---|---|---|---|
| Layered soil profile | z = 5 m, γ = 18, zwt = 2 m, γsat = 20, q = 15 | Total stress, effective stress, pore pressure | Subsurface stress checks for foundations and retaining systems |
| Point load | Q = 800 kN, z = 3 m, r = 1 m | Stress increase and influence factor | Load transfer from isolated heavy equipment or columns |
| Rectangular footing | q = 180 kPa, B = 2 m, L = 3 m, z = 2 m | Additional stress with depth | Preliminary settlement and stress distribution studies |
Formula Used
1) Layered Overburden Stress
Total vertical stress depends on unit weight, depth, and surcharge. Below the water table, pore pressure reduces effective stress.
σv = γ·z + q u = γw·(z - zwt) for z > zwt σ′v = σv - u2) Boussinesq Point Load
This model estimates stress increase at a depth z and radial distance r below a concentrated surface load Q.
σz = (3Q / 2πz²) · [1 / (1 + (r/z)²)^(5/2)]3) Rectangular Footing by 2:1 Method
The 2:1 distribution gives a quick engineering estimate for stress increase beneath a uniformly loaded rectangular area.
Δσz = qBL / [(B + z)(L + z)] σtotal = σ0 + ΔσzHow to Use This Calculator
- Select the appropriate stress method for your engineering scenario.
- Enter dimensions, load values, and soil parameters in consistent units.
- Click Submit to display the result above the form.
- Review the graph to understand how vertical stress changes with depth.
- Use the data table for reporting, checking, or exporting results.
- Download CSV for spreadsheets or PDF for design notes.
- Compare methods when you need screening-level estimates for different loading conditions.
- Validate final design assumptions against detailed geotechnical analysis when required.
FAQs
1) What does vertical stress mean in soil or rock?
Vertical stress is the normal stress acting downward through a point in the ground. It comes from soil self-weight, surface surcharge, and structural loads transmitted into the subsurface.
2) What is the difference between total and effective stress?
Total stress includes all overlying weight and surcharge. Effective stress is the portion carried by the soil skeleton after subtracting pore water pressure. Effective stress controls strength and settlement behavior.
3) When should I use the point load option?
Use the point load model when a concentrated load acts over a very small area compared with the depth of interest. It is often used for idealized checks and influence studies.
4) Why does stress decrease with depth in the 2:1 method?
The 2:1 method spreads the applied load over a larger area as depth increases. Because the same load acts on a growing distributed area, the additional stress becomes smaller.
5) Is the 2:1 footing method exact?
No. It is a practical approximation for quick design checks. For sensitive settlement problems, layered soil profiles, or irregular foundations, more detailed elastic or numerical analyses are better.
6) Which units should I use?
Use consistent engineering units. This page assumes depth in meters, loads in kilonewtons, unit weight in kilonewtons per cubic meter, and stress in kilopascals.
7) Does groundwater always reduce effective stress?
Below the water table, pore water pressure develops and reduces effective stress compared with total stress. That reduction can strongly affect bearing capacity, consolidation, and shear resistance.
8) Can I use this for final foundation design?
It is best for screening, education, and preliminary design. Final design should consider site investigation data, layered stratigraphy, drainage conditions, and applicable code requirements.