Compaction grouting is a form of soil stabilization that's done by pumping grout into the ground through threaded steel casings under high pressure to seal the limestone and compact soils. It may, for example, be used to fill subsurface voids or fissures in limestone bedrock. Where slurry grouting permeates and solidifies soils, compaction grouting densifies and replaces soils.
Compaction grouting is often used in combination with slurry grouting. The former is typically stopped above depths of 20 feet in order to avoid heaving and damaging the structure.
Slurry grouting, injected at lower pressures, is then be used to stabilize the remaining soil strata.