Category: Quantities & pricing
Prepared by Eng. Ahmed Fathy, Projects Manager ·
Definition
The swell factor is the ratio of loose soil volume after digging to its volume in the ground. Sandy soil swells less than clay, and broken rock swells more. It is used to work out haulage trips and tip volumes.
Why it matters on a project
BOQs measure excavation in place, but haulage cost follows the loose volume. Ignoring the difference loses the contractor money on carting.
Worked example
400 m³ dug in place with a 1.25 swell factor: loose volume 400 × 1.25 = 500 m³; with 20 m³ trucks that is 500 ÷ 20 = 25 trips.
Common mistake
Pricing spoil removal on the in-place volume, so actual trips run about a quarter higher or more.
Frequently asked questions
What swell factor is typical?
It varies with soil and comes from experience or the soil report; broken rock is higher.
Is excavation measured loose?
No, excavation is measured in place per the method of measurement; swell goes into the haulage rate.
Related terms
- ExcavationRemoving soil down to the required foundation level.
- BackfillRefilling excavations around foundations with suitable soil in compacted layers.
- Equipment costThe cost of plant used in the work, hired or owned.
- Method of measurementThe agreed rules for measuring each BOQ item.
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