MOORE & TABER                     

 

 

Soil Grouting and Ground Improvement Specialists

 

         

Compaction grouting is a ground treatment technique that involves injection of a thick-consistency soil-cement grout under pressure into the soil mass, consolidating, and thereby densifying surrounding soils in-place.  The injected grout mass occupies void space created by pressure-displacement.  Energy from a high-pressure pump at the surface is transmitted through confined delivery lines and casing to target soils at depth, using low-mobility grout as a medium.  Compaction is produced in weak soils through pressure displacement until the energy imparted to the soil exceeds the effective stress.  Slight uplift is then noted at the ground surface, the casing is withdrawn to the next injection stage and the process is repeated.

Where injected into very dense soils or bedrock, compaction grout remains somewhat confined, since the surrounding material is quite dense.  However, when injected into under-consolidated or poorly-compacted soils, grout is able to "push" these materials aside.  This is depicted in the images to the left, showing an excavated grout column in the local bedrock (top image), and higher in the treatment profile in a zone of weak fill (bottom image).  The images were obtained by a geologist during a down-hole inspection of a 24-inch bucket auger drill hole through a completed grout column.

When grouting treatment is applied on a grid pattern, the result is improved compaction of displaced soils, and greater uniformity of the treated soil mass.  As a secondary benefit, the resulting grout columns add strength in the vertical axis, as typical grout compressive strengths exceed those of the surrounding soils.

Compaction grouting applications include densification of foundation soils, raising and releveling of structures and foundation elements, mitigation of liquefaction potential, augmentation of pile capacity and pile repair, and densification of utility trench backfill soils.

Although densification of foundation soils subject to long-term settlement remains to be the principal application, ground improvement methods incorporating compaction grouting methods have become increasingly accepted by the engineering community as a means of mitigating liquefiable soils influencing existing facilities.  Inherent in the grouting process is the capacity to work in areas of limited access and existing improvements to treat discrete zones within the soil profile.

If you would like to learn more about the compaction grouting process, or wish to discuss your project requirements, please contact us.