Compaction Grouting

Compaction grouting is a grouting technique employing relatively high pressure and is used to increase the density of the soil into which it is introduced.

Its application is appropriate for loose soils and involves introducing a pumpable but very stiff grout into the soil with the aim of achieving compaction of the soil by the imposition of high horizontal stresses. The consistency of the grout is designed to avoid the phenomena of impregnation or claquage, which can result form high pressure application to more fluid grouts.

Installation of the grout is effected either as a continuous column or as a series of interlocking bulbs with the expectation that the volume of grout injected will be in the range of 5% to 10% of the soil volume being treated.

The benefits available form compaction grouting are:

• A denser less compressible soil.
• An improvement of the global shear strength of the soil whereby the columns act as rigid inclusions.
• Consolidation by drainage through the grout in the case, where porous grout is used.

The principal applications for compaction grouting are for:

• Underpinning existing structures.
• Recompression of soil following the passage of a tunneling machine.
• Slope stabilization.
• Reduction in the risk of soil liquefaction under seismic loading.