Trench, bedding and backfill

Excavation, bedding, pipe surround, backfill and spoil to cart away for a pipe trench. Enter the pipe size and the bedding depths.

✓ Free, no sign-up ✓ Works on your phone, standing at the problem ✓ The formula and the assumptions are always shown

IT CIVILS  ·  IT ADMIN BUSTER
1 Enter the job

Trench, bedding and backfill

Worked out at itcivils.com/free/calculators/  ·  Free construction calculators for site teams.
Check every quantity against your own specification and your supplier's own figures before ordering.

A worked example

This is the job the page opens with, already worked out. Change any figure above and the answer changes with it.

The job

Trench length
100 m
Trench width
600 mm
Trench depth
1 200 mm
Pipe outside diameter
160 mm
Bedding under the pipe
100 mm
Surround over the crown
150 mm
Bulking of the spoil
25 %
Truck capacity
6 m³

The answer

72m³  ·  Excavation

Excavation
72 m³
Bedding stone under the pipe
6 m³
Surround stone around and over
16.59 m³
Pipe displaces
2.011 m³
Imported stone, total
22.59 m³
Backfill from the spoil
47.4 m³
Cart away, loose at 25%
30.75 m³
Loads at 6 m³
6 loads

The working

Trench 100 × 0.6 × 1.2 m = 72 m³.
The surround zone is 0.31 m deep, less the pipe at π/4 × 0.16² × 100 = 2.011 m³.
Backfill is what is left, and the spoil to cart is the rest, bulked.

What it assumes

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On the job

2 Stay in the loop

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Why these are free, and what they assume

These come from ten years on site: first in contracting on production and civil works, then in consulting doing construction monitoring for consultants appointed by the City of Cape Town. Working a quantity out twice, because the first answer was on a piece of board that blew away, is a thing that happens to everybody.

Every calculator shows the formula it used and the assumptions it made, because a number with no working behind it is worth nothing on site. Where a figure varies by material or supplier, it is an input you can change rather than something hidden. Check the answers against your own specification and your supplier's own figures before you order. These help you work faster, they do not replace your own judgement.

If they save you time, the paid IT Admin Buster packs cover the admin side: progress report templates, daily diaries, inspection checklists and the wording banks that go with them.