The deep mixing (DM) method involves enhancing weak soils by mechanically blending them with a hardening agent such as cement, lime, slag, or other binders at specified depths using augers. This method can be executed using either a wet or dry approach.
Dry Deep Soil Mixing:
Dry soil mixing is an effective ground improvement technique used to enhance soft, high-moisture clays, peats, and weak soils by mechanically blending them with dry cementitious binders. This method employs high-speed drills equipped with radial mixing paddles near the bottom of the drill string. As the tool advances into the ground, it shears the soils, preparing them for mixing. Dry binder powder is then introduced through the drill string under air pressure, blending with the soil during withdrawal. The process results in the construction of individual columns, rows of overlapping columns, or achieves 100% mass stabilization, all designed to meet specified strength and stiffness requirements suitable for various engineering applications.
Wet Deep Soil Mixing:
Wet soil mixing, is utilized to improve weak soils by mechanically blending them with cementitious binder slurry. This method involves powerful drills equipped with contra mixing tools that advance into the ground while binder slurry is pumped through the connecting drill string. The mixing action occurs throughout the depth of the soil, enhancing its properties. As the mixing tool is withdrawn to the surface, additional blending of the soil and binder occurs. Wet soil mixing typically forms individual mixed columns or rows of overlapping columns, designed to provide the necessary strength and stiffness for supporting foundation or embankment loads. Detailed finite element analysis is often used to optimize the design for specific engineering requirements.
Applications of Deep Soil Mixing:
- Support of superstructures, including buildings, walls, and embankments
- Waterfront and marine applications including quay walls, wharf structures, and breakwaters
- Stabilization of slopes
- Lateral support
- Containment of water and pollutants
- Liquefaction mitigation
- Vibration reduction
- Support new embankments
- Mitigate ground heave due to expansive soil
Advantages of Deep Soil Mixing:
- Quiet and vibration-free operations
- Environmentally-friendly as it utilizes readily available materials
- Generates almost no spoil
- Can operate effectively at low temperatures
- Can replace more expensive deep foundation methods
- Flexible in application
- Reduces construction time
