Ground Improvement

Ground improvement is carried out for various objectives: to improve bearing capacity and reduce settlement of soft ground, prevent earthquake liquefaction, control groundwater, stabilize excavation bottom, prevent deformation of surrounding ground, or clean up contaminated ground. Based on improvement objectives and ground and site conditions, the most suitable method is selected from 3 different technologies: Mechanical Soil Mixing, Grouting, and Jet Grouting.


The auger and mixing paddles attached to the rod drill the ground and mechanically mix in-situsoil with cementitious materials to produce homogenous solidified columns of well-defined dimension and strength. Raito Kogyo provides a full range of soil mixing techniques including deep soil mixing, shallow soil mixing, dry jet mixing, hybrid soil mixing combined with jet grouting. Equipment to be used is ranging from a large pile driving rigs to ones as small as a backhoe.

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Shallow Soil Mixing is one variety of Mechanical Soil Mixing technology. As the name indicates, it improves the soft ground shallowly. The compact mixing equipment, attached to a standard 0.7m3 to 1.0 m3 excavator, can improve the soft ground to the depth of up to 7 m. This technique is applied to improve the foundation soil and prevent settlement of road, embankment, and building as well as to solidify and stabilize the contaminated soil.

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Jet Grouting is a technique of mixing in-situ soil with the energy of high-pressure jet of slurry. A small-diameter rod drills down to the improvement bottom. Then the rod, while being withdrawn, jets the cement-base slurry and air to produce an improved column. Jet Grouting enables improvement closely contacted to or, in some cases, encompassing existing underground structures without causing damage to them.

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Grouting is a technique to inject various types of grout into the ground at a deliberately controlled pressure and flow rate. The grout is based on cement, silicate, or other materials, selected to suit particular ground conditions and improvement objectives. The grout fills in voids and cracks of the ground and permeates into soil pores to produce a solidified soil-grout mass. The grouting is often applied to improve the ground underneath existing structures such as large oil tanks, railroad tracks and others. Directional drilling technique is often employed for drilling boreholes to circumvent underground obstructions to reach the target improvement zone.

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