Is more dirt necessary because of compaction?
More dirt is necessary when the supplier gives loose dirt and the project specifies the volume after compaction.
Divide the specified volume by 1 minus the settlement loss as a decimal.
| Settlement loss | Loose quantity | Multiplier |
|---|---|---|
| 0% | 1.00 yd³ | 1.000 |
| 5% | 1.05 yd³ | 1.053 |
| 10% | 1.11 yd³ | 1.111 |
| 15% | 1.18 yd³ | 1.176 |
| 20% | 1.25 yd³ | 1.250 |
| 25% | 1.33 yd³ | 1.333 |
Use a project value or a supplier value when one is specified.
Compaction formula
Change the percentage to a decimal. Subtract that decimal from 1.
Divide the specified volume by the result. For a 20% loss, divide by 0.80.
Calculation example
A project specifies 4.00 yd³ after compaction. For a settlement loss of 20%, 5.00 loose yd³ are necessary.
An overage of 5% increases the order to 5.25 yd³.
Settlement loss and overage
Settlement loss replaces the volume that compaction removes. Overage includes grade changes and spillage.
Apply the settlement calculation first. Then, add the overage.
Project requirements
Soil type, water, lift depth, and equipment change the compaction result. A universal percentage is not available.
For structural work, obey the project specification. The USDA NRCS soil compaction note gives more information about compaction and bulk density.
Important information
- Do not use a universal compaction value for structural work.
- Ask the supplier how it measures loose material.
- Obey the project test and density requirements.