Permeation grouting is the process of injecting a fluid grout into a soil, aggregate or rock mass to decrease permeability, increase strength or increase stability. To be effective the material selected for the grout must be able to penetrate openings in the soil or rock and then harden. There are a wide variety of materials available to match the applications. Grouting materials include portland cements, ultrafine cements and chemical grouts. Applications for permeation grouting include earth retention, controlling water flow, environmental projects, tunneling, and improving soil capacity.
To determine the applicably of permeation grouting for a specific project it is necessary to obtain soil samples and the gradation of the material requiring consolidation. For rock formations analysis of core samples and packer permeability tests give an indication of the potential for improvement.
In soils the injection usually takes place through “Tube a Manchette” (TAM) pipes also referred to as “sleeve pipes.” Sleeve pipes are constructed from steel or pvc pipe will ports drilled at a specific spacing. The ports are covered with a rubber sleeve which allows grout to flow out of the pipe, but seals when grouting ceases.
Pneumatic or mechanical packers isolate individual ports to allow grout injection to be performed at a specific horizon. Because the sleeves seal grout from reentering the injection pipe, ports can be accessed multiple times if needed. Permeating rock is typically done utilizing packers to isolate a zone and seal the hole to allow pressure to be applied to the formation.
The spacing of holes is determined by the radius of influence of achieved. Typically work is done in a primary/secondary pattern completing the outer holes first to create containment. Tests must be completed at the beginning of the project to confirm the results.
The staff of TerraFirm has completed very technically challenging permeation grouting projects. Their team of geologists, engineers and technicians can assist with material selection, processes and successful construction for your permeation grouting project.
See below links for ICOG’s presentation Grouting of Deep Foundations at the Thames River Bridge