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How It Works
Buried corrugated metal pipes must resist three external forces: soil weight, wheel loads from surface traffic, and internal vacuum. The total design pressure is the sum of all three. Once you know the design pressure you can calculate the thrust (force per unit length) in the pipe wall to verify it does not exceed the corrugation's crushing strength.
Example Problem
A 36-inch corrugated pipe is buried under 4 ft of soil. The soil pressure is 480 lb/ft², wheel pressure is 100 lb/ft², and vacuum pressure is 0. What is the design pressure and wall thrust?
- P = 480 + 100 + 0 = 580 lb/ft²
- T = 580 × 36 / 24 = 870 lb/ft
Frequently Asked Questions
What is wall crushing in corrugated pipe?
Wall crushing occurs when external pressure compresses the corrugation profile flat. The pipe fails when the thrust per unit length exceeds the corrugation's rated crushing strength, typically provided by the manufacturer.
How deep should corrugated metal pipe be buried?
Minimum cover is usually 12 inches for driveway crossings and 24 inches under roads. Greater depth reduces wheel-load pressure but increases soil pressure, so both must be checked.
Does pipe diameter affect wall thrust?
Yes. Thrust is proportional to outside diameter. A 48-inch pipe under the same pressure as a 24-inch pipe experiences twice the wall thrust, so larger pipes need stronger corrugation profiles.
Related Calculators
- Buried Plastic Pipe Calculator — pressure, thrust, and wall area for plastic pipes.
- Pipe Soil Pressure Calculator — soil weight and buoyancy calculations.
- Pipe Wheel Loading Calculator — wheel load on buried pipes at various depths.
- Buried Spiral Rib Pipe Calculator — pressure and thrust for spiral rib pipes.
- Pressure Converter — convert between psi, kPa, bar, and other pressure units.
National Resources Conservation Service. National Engineering Handbook. 1995. United States Department of Agriculture.