Deep Cement Mixing

In construction of various structures on compressible, saturated soils
like soft clay, low bearing capacity and excessive settlement are a
common problem to deal with. The ground improvement technique using deep cement-soil mixing (DCM) is one of the most suitable methods
to overcome this problem. The sole purpose of DCM is to improve
shear strength of soil by in-situ mixing the soil with cement grout. Application of ground improvement method using DCM method allows excavation works, construction of embankments for highways, reservoirs, and use of soil foundation system in soft soil environment.

Deep Cement Mixing (DCM) method is a ground-improvement technique in which cement is used as a binding agent to mix mechanically with the existing soil. The cemented soil material that is produced generally has a higher strength, lower permeability and lower compressibility than the existing soil. The cement is injected through hollow, rotated mixing shafts attached with some type of cutting blades. The shaft above the tool may be further equipped with discontinuous auger flights and/or mixing blades or paddles. These shafts are mounted vertically on a suitable carrier, usually crawler-mounted.

In recent years, DCM technique has become increasingly popular due to its low vibration and low noise construction process. Two types of installation methods are generally considered with regard to the way the binder is injected into the ground (with or without water addition): the wet and the dry mixing methods.

In the wet mixing method, which is more frequently applied, a mixture of a binder and water with possibly sand or additives is injected and mixed with the soil. Depending on the type of soil and binder, a mortar-like mixture is created which hardens during the hydration process.

In the dry soil mixing process, the binder is directly mixed with the soil. The binding agents directly react with the prevailing soil and the contained water and form a soil mortar.

Depending on the applications, different improvement patterns can be designed with the wet and dry mixing methods with the help of soil-cement columns, rectangular soil mix panels, continuous barriers or global mass stabilization.

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