Deep Soil Mixing
Deep Soil Mixing (DSM) is a ground improvement technique through blending a hardening agent (usually cement grout) with the native soils, in situ. The process improves the strength and stiffness of the soil to increase bearing capacity, decrease settlement, and mitigate seismic issues. Also used to form walls for excavation support, erosion control, or contamination barriers.
A revolving hollow shaft with mixing paddles and/or a section of auger (the mixing tool) is advanced into the soil. As the mixing tool is advanced, the cement grout is pumped through the hollow stem of the revolving shaft and discharged laterally along the lower mixing paddle where it is mixed with the native soil. When the design depth is reached, the tool is withdrawn while maintaining, or often increasing, the rotational speed of the mixing tool. The resulting column is a well-blended mixture of soil and cement grout which will cure over time to the required design strength. DSMs can also provide uplift capacity by introduction of tie-down rebar.