Jet grouting is a procedure for mixing soil with injected cement grout in-situ (on site) to create a cement-stabilized soil column. With proper quality control, the stabilized soil exhibits increased strength and decreased permeability. These modified properties allow the stabilized soil to be used as an engineered product for foundation support and groundwater control. Underpinning of existing structures and cutoff walls for excavation support are two typical applications.
Jet grouting involves the drilling or jetting of a small-diameter pipe, typically around 4 inches in diameter, to the bottom of the desired treatment depth. Once that depth is reached, contractors inject a neat cement grout under high pressure, typically around 6,000 psi, through ports at the bottom end of the drill pipe as the pipe is rotated and withdrawn to create a circular column of treated soil. The rate of withdrawal can be varied to increase or decrease the diameter of the jet grout columns. These columns are located as required for vertical support or overlapped to create a wall or barrier to the horizontal movement of weak soil and groundwater.