Soil mixing is a technique that combines cement grout with existing soil in-situ to form a soilcrete mixture that has both increased strength and reduced permeability. Steel piles are typically placed in the soilcrete while it is still wet when soil mixing is used for excavation support. The increased strength allows the soilcrete to span between the piles and the reduced permeability allows the excavation to take place under relatively dry conditions with limited draw down of the water table outside the excavation.
Soil mixing can also be used to create an impermeable barrier below the ground surface where no excavation takes place such as to reduce seepage through a dam or to contain contaminated groundwater. Another use for soil mixing is the improvement of foundation soils to reduce the probability of liquefaction during an earthquake and increase their strength.