The term soil mixing commonly refers to any process by which reagents (wet or dry) are added to and mixed with unsuitable or contaminated soils. Other terms such as deep mixing method, shallow soil mixing, deep soil mixing, cutter soil mixing and trench cutting remixing deep wall are commonly used by engineers and contractors in the geotechnical industry to refer to soil mixing or a particular type of equipment. The purpose is similar: the efficient creation of a soil-reagent composite with improved properties relative to the in-situ soils. Improvements for contaminated soil mixing generally include factors such as strength increase, permeability reduction and contaminant mobility reduction.
Contaminated soil mixing is commonly performed in-situ using single axis large diameter auger mixing with wet reagent addition. Large diameter auger mixing in this application is performed by pumping a liquid reagent mixture down through a hollow drill stem into a large auger (auger diameters in the 0.9 m to 3.7 m [3 ft to 12 ft] range) where the fluid is allowed to exit the system via ports on the back of the auger and is mixed with the soils. The result is a soil column evenly mixed or treated with the reagent. Subsequent columns are installed in an overlapping pattern to confirm 100% coverage of the target treatment area.
In the geoenvironmental industry, the terms used to describe the application of soil mixing to the stabilization/solidification and treatment of contaminated soils are in-situ stabilization/solidification (ISS) and in-situ (chemical) treatment (IST).