Earthwork
Compaction
The mechanical process of densifying soil by reducing air voids, using rollers, plate compactors, or jumping jacks to achieve specified density.
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In the Field
Compaction is tested with a nuclear density gauge or sand cone test. Most specs require 95% of maximum dry density per Proctor. Lift thickness matters — never compact lifts thicker than 8–12 inches for most soils.
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Rule of Thumb
Compact in 6–8 inch loose lifts for cohesive soils, up to 12 inches for granular soils. More passes on a thick lift do not substitute for proper lift thickness.