Historically soil mixing, which involves the mixing of cement or lime into the in-situ soil, has been performed using single or multiple paddles at the toe of the kelly drill string or counter rotating continuous flight augers to form columns of treated ground or panels of interlocking columns. These mixing tools are generally mounted on a conventional piling mast.
Frequently the primary application of soil mixing is for the improvement of the engineering properties of the soil, in particular its shear strength, which leads to the improvement of the modulus and settlement characteristics of the treated soil as well as reduced permeability. Hence the most common application is predominantly in soft and weak soils, essentially water charged fine grained soils such as clay.
Applications of soil mixing have been extended to treating contaminated material in-situ; in some instances cement or lime, the more traditional additives, are used to bind the contaminated material but other additives, aimed at neutralising the in-situ material are used depending on the nature of the contamination to be addressed. This decontamination activity demands blanket coverage of the treatment area, whereas the ground improvement is usually installed as isolated columns or rows.
Recent developments have introduced the CSM system of wet soil mixing, the installation equipment which is derived from diaphragm wall cutter technology, in that it comprises two cutting and mixing drums, driven by compact hydraulic motors, as opposed to the simple paddle or auger equipment. The drums operate in counter rotation and are kelly mounted, on a conventional piling mast, providing a high degree of precision. This configuration is designed to combine high penetration rates with excellent soil/cement mixing.
The shape of the treated soil is rectangular and can therefore the soil mixing can be installed as individual units or continuous walls.
