Compaction Grouting and Foundation Repair
Compaction Grouting is the stabilization of poor soils under buildings, structures, roadbeds, railroads, or runways, by driving injection pipes down to stable ground and then injecting low-mobility grout to densify soft soils and form grout columns. Injection is continued in a pattern to cover all of the target area until the ground, building, or slab is raised back to original elevation, eliminating all voids. The amount of grout injected and pressures at each lift are closely monitored on every hole to adjust for differing soil conditions for quality control.
Foundation repair - Compaction Grouting is an excellent alternative to helical piles in raising foundations for several reasons:
- With helical piles excavation is needed to get under the foundation far enough to try and drive piles as vertical as possible and then to get jacks underneath with a bracket to lift the foundation. Most foundations are designed to have continuous contact with the ground to be stable.
Compaction grouting injection pipes are driven in from the surface and slightly angled to reach stable soil under the foundation. When the soft soils are densified and stabilized, the ground, along with the building is raised. Injection pipes are removed as injection continues and no backfill is necessary.
- With helical piles, there is point loading on each pile and as the foundation is jacked up, voids are created between the piles under the foundation. Also if there is a slab-on-grade attached, voids will be created or increased, putting more stress on the slab. All voids should be grouted and the slab raised in an additional operation to stabilize the rest of the foundation.
Compaction grouting densifies the soft soils and raises the foundation by raising the ground so there are no voids and no point loading. Injection pipes can be angled to reach up to 20' from perimeter walls, depending on soil conditions. In very poor soil conditions interior slabs can also be compaction grouted to stabilize the ground and raise the slabs.
- With helical piles, there is usually much more time involved due to excavation, inserting piles, jacking foundation, backfilling, and then grouting the voids.
With Compaction grouting we can often drive injection pipes and grout the same day for a typical garage size building.
Project Gallery
Kodiak - Warehouse has settled on one side, so injection pipes were driven down under the foundation first to densify and lift.
Kodiak - Angling injection pipes to raise inside office area not accessible from inside.
Kodiak - Pipes driven down 18' to stable ground to densify and lift building.
Kodiak-Densified ground under slab and raised to original elevation.
Healy - Inserting grout pipes in tight quarters to lift building.
Healy -Finishing injection at lowest point, raising close to original elevation as ground lifts.
Palmer - garage settled due to frozen fill with voids to 6" and settlement to 3". After the interior monolithic slab was stabilized and raised, compaction grouting was done also to the perimeter to stabilize.
Palmer - small drill rig used in 8' headroom to insert pipes down to stable ground to densify and lift with low-mobility grout. The large void and initial lift was done with fluid cellular grout first.
Boeke Ice Arena - A large area about 40' in diameter in the center of the rink settled up to 3". Compaction grouting was used with low-mobility grout injected down to 18' to stabilize soft layers and raise the slab. Injection pipes had to inserted between coolant tubes 3" on center.
Anchorage-Storage buildings built on peat settled up to 12" over many years. Compaction was used to reach 20' under the center footings to densify and raise the long buildings.
Anchorage-Elevation measurements were taken on top of the building so the units did not have to be emptied and be out of service.
Ground Testing-The first step in fixing poor soils underlying problem areas is to drill test holes with a hammer and split spoon sampler to check soil composition and densities down to stable ground.
