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How It Works
Soil pressure on a buried pipe equals the soil unit weight multiplied by the depth of cover. A buoyancy factor (Rw) adjusts for groundwater, and the soil load per linear foot distributes that pressure across the pipe diameter. These three checks ensure the pipe can handle the dead weight of the overburden.
Example Problem
A pipe is buried under 5 ft of soil weighing 120 lb/ft³. Soil pressure:
- Ps = 120 × 5 = 600 lb/ft²
Frequently Asked Questions
What is a typical soil unit weight?
Dry loose soil is about 90–100 lb/ft³. Compacted fill is 110–130 lb/ft³. Saturated soil can reach 130–140 lb/ft³. Use the value specified in your geotechnical report.
What is the buoyancy factor Rw?
Rw reduces the effective soil weight when the water table is within the soil cover. It ranges from 1.0 (dry) to about 0.5 (fully saturated). The exact value depends on the water height relative to pipe and ground surface.
How does deeper burial affect the pipe?
More depth means more soil pressure but less wheel-load pressure. There is an optimal cover range (typically 2–6 ft) that balances both loads for most pipe materials.
Related Calculators
- Pipe Hydrostatic Pressure Calculator — external water pressure.
- Pipe Wheel Loading Calculator — wheel loads at various depths.
- Buried Corrugated Pipe Calculator — combined design pressure and thrust.
- Pipe Vacuum Load Calculator — internal vacuum load on buried pipe.
- Geotextile Calculator — design geotextile wrapping for buried pipe bedding.
- Pressure Unit Converter — convert soil pressure between units.
National Resources Conservation Service. National Engineering Handbook. 1995. USDA.