Grouting can be used to solve a variety of geotechnical construction issues. Grouting programs can be used to densify existing soils (compaction grouting, consolidation grouting), to fill voids in soil, rock, and underneath existing structures (remediation grouting, pressure grouting), and to provide groundwater cutoffs in soil and rock (curtain grouting). Grouting can also be used to underpin existing foundations, as well as to elevate or “jack up” slabs and foundations which have experienced unwanted settlement.
While each grouting program has its own unique characteristics, most possess a number of similarities. Generally speaking, a series of drill holes are laid out in advance. A pattern of primary holes are laid out first, and may be spaced 10 to 20 feet apart. A pattern of intermittent secondary, tertiary, and/or quaternary holes are then laid out at a closer spacing between each of the primary holes. After primary holes have been completed, subsequent holes are used not only to augment the initial grout placement, but also to gauge the success of the initial grouting, through the careful observation of grout encountered during the drilling of any following holes.
Once the grouting program commences, a drilled hole is first advanced to a targeted depth. This depth is selected based upon the desired goal of the grouting program, as well as the subsurface conditions present. The drilled hole will generally be created by advancing a temporary outer drill casing, and may also include the advancement of inner drill rods. When the required tip elevation is reached, the grout can be placed in a number of ways. Grout can be placed under relatively low pressures (typical when filling large voids), or can be pumped under high pressures (when infiltrating fractures in rock, densifying soil masses, or elevating structures). The volume and placement of grout can also be controlled through the use of flow meters and packers, allowing for more calculated execution of the work. Grouting can be performed in one or more “stages” depending upon the desired goals of each project, allowing for further control of the grout placement.