Compaction grouting has some problems that are basically attributed to the little understanding of grouting mechanisms. Large-scale double-wall calibration chamber and injection systems have recently been developed to physically model and investigate the technique in the laboratory. This paper describes the main features of the developed systems and presents and discusses results of injections performed into sand samples under different confining pressures. The grouting mechanisms are discussed in terms of the variation with injection of the vertical displacement of soil surface, the volume change of soil, and the coefficient of earth pressure at rest (K₀). The results and discussions reveal that during injection the soil exhibits large deformations and increases in the lateral stress. After termination or during suspension of injection, the soil experiences creep deformation and lateral stress relaxation. The initial stress condition of soil highly influences the soil deformation. The soil volume change increases with injection, but at an attenuating rate. A unique relationship between the increase of K₀ with injection and the volume of injected grout is established.