Patent ID: 7455479

Claim:
A method of preventing soil fracture during jet grouting, comprising: monitoring borehole pressure in a jet grouting borehole while the jet grouting is being performed; and determining whether the borehole pressure exceeds a predetermined limit or determining whether the borehole pressure increases at a rate exceeding a predetermined rate, wherein the step of monitoring the borehole pressure comprises: injecting pressurized air into the borehole at a flow rate sufficient for the pressurized air to travel through the borehole at a predetermined speed; determining a reference pressure of the pressurized air necessary for the pressurized air to travel at the predetermined speed into the borehole at a reference borehole depth; determining a second pressure of the pressurized air necessary for the pressurized air to travel at the predetermined speed into the borehole at a second borehole depth deeper than the reference borehole depth; and comparing the reference pressure to the second pressure to determine the borehole pressure.