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Sinkhole Pressure Grouting
 Foundation Services performs pressure grouting in areas that geotechnical engineers have found to be sinkhole conditions. This involves the injection of a low slump grout, which mainly consists of cement, sand, water and fly ash, into the soils at or above the limestone layer.
The purpose of the pressure grouting is to seal off the limestone surface and prevent soils from further raveling into the solution cavities. This process is accomplished by installing injection pipes to the depth of the limestone layer. The depth may vary considerably from one side of a structure to the other. Engineering reports generally provide this information before the job begins. Once these injection pipes are installed, a concrete pump is connected to the pipes.
A pressure gauge is utilized between the concrete pump and the injection pipes. The grout is then pumped into the pipes while the structure is monitored for movement and the gauge is monitored for high pressures. Once the pressure gauge reaches 300 psi, the grout pipe will be extracted in 5' increments and the process starts over until the soils have been stabilized within 10 to 15 feet of the surface. The pumping ceases and the pipe are pulled at this point to prevent any damage to the structure.
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