Response characteristics of grouting-induced ground heave and evolution of grout diffusion patterns in soft stratum

[Objective] Grouting technology is an important ground improvement method in underground engineering and plays a significant role in enhancing foundation bearing capacity and improving the mechanical properties of soft soils. However, grout diffusion within the soil may disturb the original in-situ stress equilibrium, thereby inducing soil deformation and ground heave, which may pose potential risks to surrounding buildings, structures, and underground engineering works. [Methods] This study conducted a series of laboratory model tests to systematically investigate the effects of grouting pressure, burial depth, and water-cement ratio on ground heave response. In addition, three-dimensional reconstruction technology was employed to analyze the morphological characteristics of grout bodies, and the relationship between grout body morphology evolution and grout diffusion patterns was further explored. [Results] The results indicate that the heave evolution can be divided into three stages: initial stress accumulation, rapid uplift, and subsequent rebound or stabilization. The heave is primarily concentrated near the grouting center and attenuates with increasing radial distance. Increasing grouting pressure markedly enhances the maximum heave, whereas greater burial depth suppresses its development. Under a constant grouting pressure of 300 kPa, as the water-cement ratio increases from 0.3 to 0.9, the maximum heave exhibits a non-monotonic trend, first increasing and then decreasing. Three-dimensional reconstruction further reveals that the grout diffusion pattern transitions from compaction-dominated to fracture-dominated with increasing water-cement ratio. [Conclusion] These findings contribute to a better understanding of the quantitative relationship between grouting parameters and ground heave, as well as the evolution of grout diffusion patterns, and provide a theoretical basis for parameter optimization in underground grouting engineering.