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Project brief
A precast concrete manhole section lowered by crane chains into an excavation shored with steel trench boxes

Calculator · Sheet T-204

Pipe bedding and backfill calculator

Granular bedding and embedment around a pipe, per metre and for the run, in cubic metres and tonnes.

Pipe bedding & backfill · Sheet T-204Metric
m
m
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t/m³
Use your supplier’s or the spec’s value.
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Estimates only. Check quantities against the drawings and your supplier before ordering.

STA 0+120How it works

Granular zone area per metre = trench width × (bedding + pipe OD + embedment) − π × OD² ÷ 4. Multiply by the run length for the volume, add the waste allowance, then multiply by density for tonnes.

STA 0+240Assumptions and sources

The default density of 1.9 t/m³ sits within the published bank (in-place) weight range for gravel of roughly 1.77 to 2.05 t/m³1; replace it with your material’s compacted density.

Questions people ask

How do I calculate pipe bedding?

Work out the area of the granular zone around the pipe (trench width times the zone height, minus the pipe’s circular area), multiply by the pipe length and then by the material density for tonnes.

What depth of bedding is required under a pipe?

It depends on the pipe type and the owner’s standard. Municipal and provincial specifications set bedding classes and dimensions; follow the one in your contract.

What density should I use for bedding gravel?

Use the compacted density from your supplier or spec. As a planning check, published bank weights for gravel run roughly 1.77 to 2.05 t/m³1.

Sources

  1. FM 5-434 Earthmoving Operations, Chapter 1, Tables 1-1 and 1-2U.S. Department of the Army (field manual; hosted copy on GlobalSecurity.org) · FM 5-434 (2000)