The key condition for forming the effect of compacting grouting is to use low-slump grout, usually low-slump cement mortar. Currently, the process of compacting grouting using low-slump mortar that has been successfully developed is the Controllable Compaction Grouting Method (CCG Method) jointly developed by Shanghai Tunnel Engineering Co., Ltd. and Shanghai Shentong Group Co., Ltd. This method, through research on equipment, materials, and processes, has achieved compacting grouting with cement mortar having a slump less than 50mm, and has been successfully applied in saturated soft clay in the Shanghai area.

The CCG grouting method primarily utilizes special high-pressure, low-flow grouting equipment to force high-viscosity, low-slump mortar into the foundation soil of the reinforcement area according to design requirements. Under pump pressure, the mortar does not mix with the soil mass or penetrate into the soil with less resistance in a streaky manner; instead, it expands in place to form a slurry bubble, squeezing the soil around the grouting point. As the grouting pipe is lifted, it forms a葫芦-shaped or cylindrical solidified mortar pile with controllable early strength, achieving the purposes of enhancing soil strength and density, improving foundation bearing capacity, correcting deviations, and underpinning foundations.

The CCG method belongs to the compacted grouting process. The presence of a good drainage channel has a direct impact on the reinforcement effect of the soil mass. Therefore, generally speaking, the reinforcement effect of the CCG method in sandy soil is better than that in clayey soil. When constructing in clayey soil, auxiliary drainage measures should be considered, such as well points and sand wells.

The low-slump cement mortar used in the CCG grouting method typically consists of cement, sand, fly ash, bentonite, water, and additives. Depending on the actual project requirements, its unconfined compressive strength can be selected within the range of 3 to 15 MPa.