Effects of Confining Stresses on Mechanisms of Heave-Inducing Compaction Grouting.

The control of surface heaving has been of interest in major applications of compaction grouting such as ground improvement and settlement compensation works. Some studies generalize compaction grouting as heave-inducing and thus the corresponding soil improvement increases with depth, while others do not. Effective planning of compaction grouting requires assessment of whether it is heave-inducing and understanding the effects of confining stresses on its mechanisms and effectiveness. Unfortunately, little effort has been made in this regard. The current paper addresses these issues through physical modeling of compaction grouting using a large-scale double-wall calibration chamber and injection system capable of injecting the stiff compaction grouts. The results of twenty-one test cases conducted under well-controlled conditions are presented, discussed, and compared with the results of actual compaction grouting. The confining stresses as represented in terms of the vertical stress (σ_V) and coefficient of earth pressure at rest (K₀). The presented results and discussions show the reliability of the adopted modeling. Empirical correlations that engineers can use to predict the occurrence of surface heaving as well as pre-heaving compression of soil, surface heave, creep deformation, and residual increase of K₀ for given confining stresses are newly introduced. The results of developed correlations show good comparison with those of actual compaction grouting. Implications for actual compaction grouting are also presented. [ABSTRACT FROM AUTHOR]