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.
One application for soil mixing is in the construction of earth retaining structures where a groundwater cut-off is also required. Schnabel typically drills a series of overlapping soilcrete columns simultaneously to create a continuous groundwater cutoff wall. Steel piles are typically placed in the soilcrete while it is still wet to improvr it’s strength. The increased strength of the soil mix treated ground allows it span between the piles. The reduced permeability of a soil mix wall 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.