Soil mixing is used for temporary and permanent deep excavation projects. The method is used to mix cement slurry with soil in situ to create a cohesive soil block. Strength of mixed soil is variable and tailored according to project requirements and site conditions.
Mechanical soil mixing is performed using single or multiple shafts of augers and mixing paddles. The auger is slowly rotated into the ground. Cement slurry is pumped through the hollow stem of the shaft(s) feeding out at the tip of the auger as the auger advances. Mixing paddles are arrayed along the shaft above the auger to provide mixing and blending of the slurry and soil. Slurry lubricates the tool and assists in the breaking up of the soil into smaller pieces. Spoils come to the surface since fluid volume is being introduced into the ground. These spoils comprise cement slurry and soil particles with similar cement content as what remains in the ground. Pre-determined mixing patterns are followed to meet design requirements.
Steel beams are typically inserted in the fresh mix to provide reinforcement for structural reasons. A continuous soil mix wall is constructed by overlapping adjacent soil mix elements. Soil mix sections are constructed in an alternating sequence; primary elements are formed first and secondary elements following, once the first have gained sufficient strength.
The soil mix method can be very effective at providing very stiff and waterproof retaining systems.