This study introduces a unified cylindrical and spherical cavity reverse expansion model to simulate the formation of compaction grouting bodies and grout diffusion along pile shafts. Stress field expression employs the superposition method, while displacement field analysis utilizes the nonassociated Mohr-Coulomb criterion. By combining the displacement expression for cylindrical cavity reverse expansion with the fluid flow equation, a calculation method is proposed to compute the upward and downward diffusion heights of grout, considering the unloading effect. The parameter analysis demonstrates that ultimate grouting pressure increases with increasing soil strength and grouting depth, with the ultimate grouting pressure at the pile tip being greater than that at the pile side. The value of grout diffusion height is negatively correlated with unloading ratio and grouting depth while positively correlated with grouting pressure and pile diameter. The deeper the grouting depth, the greater the impact of unloading on grout diffusion height. Three case studies validate the effectiveness of the proposed model. Analysis reveals that when grouting pressure exceeds the ultimate pressure, the size of the grout body is related to the grouting volume. Neglecting the unloading effect in the prediction of grout diffusion height for pile foundations would lead to conservative results.

This study evaluated the performance of cement-based grouts in compaction grouting. In the experimental study carried out, the simultaneous effects of fly ash (FA) and nano-silica (NS) on rheological and fresh-state as well as strength performances were investigated. In this context, 16 samples were prepared using 0%, 10%, 20%, and 30% FA replacement levels and 0%, 1%, 2%, and 3% NS content ratios at w/b = 0.75. Rheological characteristics and behavioral performance were defined with shear stress, apparent viscosity, yield stress, and plastic viscosity. Fresh-state performances, flow time with mini-slump, stability capacity with bleeding, and hardening periods with setting time were determined. In terms of mechanical performance, 28-day unconfined compressive strength (UCS) tests were carried out on grout samples. After the tests, the correlation relationship between them was examined using experimental data. The experimental results were performed with statistical analysis, and then, the contribution and impact levels of important parameters were evaluated. Test results showed that the simultaneous FA and NS influence resulted in reasonable outcomes in both the rheological and fluidity properties and caused a visible enhancement in the strength features., Statistically, NS content was dominant in rheological and fresh-state performance, while FA replacement was effective in strength features.

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 (sigma 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.