One of the big issues when using a synthetic slurry for foundation drilled shafts is losing slurry through coarse, unconsolidated formations. If the level of the slurry drops below the required level to maintain adequate hydrostatic head pressure, the shaft can collapse. If drilling is completed too late in the day to pour concrete, contractors often have someone either stay the night on the jobsite or make frequent trips to the jobsite throughout the night so that they can top off the shaft to maintain adequate hydrostatic head pressure.
Many contractors resort to conventional bentonite slurry when certain soil conditions, such as gravel and cobble, are noted on bore logs. These situations necessitate the use of drilling fluid recycling/cleaning equipment. CETCO recently developed a fluid-loss additive that can dramatically reduce and even eliminate the loss of synthetic slurry in a foundation drilled shaft when drilling through coarse, unconsolidated soil conditions. This product can broaden the range of soil conditions that can be drilled with synthetic slurry.