Drainage Aggregate Wrap Calculator — Stone and Geotextile Quantity
Estimate the amount of drainage stone surrounding a perforated pipe and the geotextile area needed to wrap the assembly. Keep aggregate volume, pipe displacement and fabric overlap visible.
Drainage assembly inputs
Mass and quantity scenarios
—
| Scenario | Aggregate volume | Estimated mass |
|---|
Aggregate quantity formula
The gross aggregate envelope is treated as a rectangular prism around the pipe:
The pipe occupies part of this cross-section, so its cylindrical volume is subtracted:
The result is an estimate of the nominal aggregate volume inside the stated envelope.
How the fabric area is estimated
The calculator treats the fabric as wrapping around the outer width and height of the aggregate envelope. That perimeter is then multiplied by run length and increased by the specified allowance.
Overlap is represented by adding the entered overlap width to the developed fabric width at the wrap seam. The exact fabric cutting pattern can differ at ends, corners and connections.
Worked example
For a 25 m run, a 160 mm pipe, a 500 mm aggregate width, 100 mm below and 200 mm above the pipe, the envelope height is 460 mm. The gross envelope is 5.75 m³ and the pipe displacement is about 0.503 m³, giving approximately 5.25 m³ of nominal aggregate before any project allowance.