Jim Piasecki takes a look at pumping the grouting material, grout mixing equipment and grout pump selection.
For many years now, state and federal government agencies have identified bentonite grouting materials and placement methods and strongly have recommended that positive placement of grout by tremie under pumping pressure be used for all types of wells where bentonite grout is to be placed. It is essential that the bentonite grout always be introduced from the bottom of the space being grouted and pumped upward to avoid separation or bridging of the grouting materials and to remove undesirable cuttings from the bore hole.
The bentonite grout is pumped into the annular space through a tremie pipe that has been inserted to the bottom of the borehole along with the casing. The annular space between the borehole and casing is usually 2 inches or larger. This can vary depending on state regulations, depths and drilling conditions. Grouting is complete when the grout slurry leaving the borehole at the surface is of the same weight and consistency as the grout slurry being introduced into the bottom of the borehole. This method assures that the entire length of the annulus is grouted in a consistent manner and is the recommended grouting technique for most well installations.