Cutter soil mixing (CSM) improves the engineering properties of soils by mechanically blending the in-situ soils with a designed cementitious binder slurry.
The result of CSM is a stiffened rectangular soilcrete element with a target unconfined compressive strength and permeability. Soil treatment is possible at depths of up to 165 ft; however, typical panel depths are 80 to 115 ft.
Process
Cutter soil mixing is performed using vertically aligned cutter wheels that, as they rotate along a horizontal axis, penetrate the in situ soils and mix them with binder to form a rectangular element of improved soil.
During penetration, the cutter wheels disaggregate the soil while a bentonite or light grout slurry is pumped through the tool and mixed with the soil.
During withdrawal, a cementitious slurry is pumped through the tool and blended with the soil at high rotation speed, creating a well-mixed in situ product commonly referred to as soilcrete.
Ideal cutter soil mixing ground conditions
Cutter soil mixing is applicable to most cohesive and granular soils; however, ease of mixing depends on soil type, strength, density, water content, plasticity, stratigraphy, and texture.
Equipment and tooling are selected based on the subsurface soil conditions. Pre-drilling can be used to improve productivity in very dense soils or soft rock, or if obstructions are anticipated.
Common uses
- Temporary shoring for deep excavations
- Cut-off walls to mitigate seepage or contaminant transport
- Mitigate liquefaction
- Improve slope stability
- Reduce lateral loads for earth retention structures
- Provide structural and foundation support
Advantages
- Quiet and vibration-free
- Rectangular elements limit overlap requirements and material usage
- Uses readily available materials
- Replaces more expensive deep foundation and earth retention methods
- Groundwater control can be considered
- Can be used individually or combined with other solutions to reduce costs
- Reduces construction time
- Can be used to solve numerous geotechnical and groundwater issues
- Elements can be installed to form various efficient geometries
Quality assurance
Pre-production laboratory testing is used to evaluate the required grout mix design and validate the installation methodology. A pre-production field test program is often conducted to validate grout mix and installation parameters (grout volume, mixing energy, penetration rate), as well as batching and pumping operations.
Data acquisition systems are used on all mixing rigs to monitor mixing parameters in real time. Test columns can be excavated for visual inspection of the soilcrete. Wet sampling in fresh elements and coring of cured elements can be used to verify strength and permeability. Visual inspection of the in situ soilcrete elements is possible with a camera lowered into a core hole. In situ testing options for the elements are also available.
Related projects
Institutional
University of Portland, Franz River Campus
Keller provided a ground improvement solution to mitigate lateral spreading and foundation support for new structures on the 35-acre Franz River campus.
Residential
One Park
One Park is a three-tower, mixed-use complex featuring 333 luxury condominiums, retail and office spaces in downtown Richmond.
Commercial
The Paramount
Keller completed wall construction ahead of the client’s aggressive schedule.
Commercial
Aragon Development Complex
Keller successfully completed their first cutter soil mixing (CSM) project in Canada one week ahead of schedule.
