Ground Improvement

Compaction Grouting

Compaction Grouting is a specialized technique used for controlled densification of in place (in-situ) soils at depth. Essentially, it is the injection of a stiff mortar like grout into a compatible soil mass to achieve controlled densification of that mass by physically moving the soil particles, radially from a growing "bulb" of Grout, into a closer spacing. After maximum densification of the soils is achieved, continued controlled injection can be used to raise and re-level structures.

Compaction grouting is done by using the split spaced, ascending stage method. Stage lengths will be 2 to 3 feet. Grout injection points will be installed on a regular grid. Primary injection points will be installed at alternate point locations. If Secondary points are required, Secondary points will be installed midway between the primary points. Injection points shall be installed to full depth, then grouted in stages as the point is withdrawn from the hole. Depths shall be as required per point below existing ground surface to ground surface. Grouting will not be permitted in a secondary point until the adjacent primary points are completed.

Grouting of a stage will continue uninterrupted until refusal to take grout occurs. Refusal is defined as a sustained pumping rate of 0.5 cf. per minute at 400 psi, or the first signs of soil shearing (normally indicated by a sudden pressure drop of 50 psi or more at the point of injection), or measurable surface uplift.

Permeation Grouting

The purpose of the Permeation grouting is to permeate cohesiveless soils with a solution or fine particulate colloidal solution, which will react to form a gel in the pore spaces of the soil. The gel will impart properties of cohesion and reduced permeability to the treated soils.  The intent of permeation grout

The grouted zone essentially becomes a sandstone mass which increases the soil’s compressive and shear strength, increases the effective load bearing of the sand material, mitigates settlement due to consolidation by loading and seismic forces, and decreases the soil’s permeability.