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Compaction grouting method called as CPG is becoming popular as a ground improvement technique due to its wide variety of applications and several advantages. However, so far, the application of the method has been mainly dependent on field tests, practical experience and empiricism. This paper presents a 2-D finite element model of CPG based on the elasto-plastic theory of strain hardening that takes variations in stress–strain fields along the depth and the impact of the ground surface conditions on the grouting process. This reveals densification and confining aspects of CPG with relative contribution of variables like injection pressure, spacing of injection points, overburden pressure and initial relative density of ground. This paper concludes that the ground improvement by CPG should not be taken as increased ground density alone but also as increased lateral earth pressure. Although no densification can be achieved for medium or dense soil, CPG process is found to be effective in increasing the lateral earth pressure of medium or dense soil significantly. The lateral earth pressure increases with increase in injection pressure only up to the some extent but with further increase in injection pressure its effect reaches to the farther radial distances.

Compaction grouting (CPG) involves the injection of high viscosity mortar-type grout under relatively high pressure that displaces and compacts the soil in-place. Many case studies around the world prove the effectiveness of CPG to treat liquefiable soils. In these studies, mostly CPG has been developed and used on the basis of practical experiences, its densification and confining effects are not well understood until now. The objective of the present study is to bring out densification and confining effects of CPG. This paper presents a laboratory experimental study carried out to model a CPG treated ground. The study includes the experiments performed to decide appropriate consistency of grout material and appropriate relative contribution of factors such as overburden pressure, grout volume, injection speed and injection pressure that ensures efficient grouting. The effects of CPG are quantified in terms of lateral earth pressures and lateral displacements that are further defined in terms of coefficient of lateral earth pressure, K, and densification factor in the soil around grout column. This leads to a better understanding of its densification and confining effects. Although in practice, majority of the works with CPG have been related to its densification effect and lesser attention has been given to its confinement effect, in present experimental study, its confinement effect were prominent. Also at the farthest locations usually where field tests are carried out, its densification effect could not be found experimentally but its confinement effect was clear.