Study on the Diffusion Mechanism and Influencing Factors of Permeation Grouting in Unsaturated Strata

During permeation grouting, the unsaturated characteristics of shallowly buried strata are often overlooked, leading to an overestimation of the diffusion range and reduced reinforcement effectiveness. Based on the generalized Darcy law, the Green–Ampt infiltration model and the van Genuchten unsaturated soil permeability function are introduced to establish a permeation diffusion model for the slurry in unsaturated strata. Laboratory experiments were conducted to verify the accuracy and rationality of the unsaturated permeation diffusion model. The relationships between the slurry diffusion radius and factors such as slurry self-weight, strata diffusion mode, and viscosity variability were analyzed. Three different types of strata (gravel soil, sandy soil, and silty soil) were selected to analyze the impact of strata saturation on the slurry diffusion radius. It was found that when considering strata saturation, the slurry diffusion radii in different types of strata exhibit varying degrees of attenuation compared to their saturated state. At 25% strata saturation, the slurry diffusion radius in gravel soil becomes74.03%, 33.29% in sandy soil, and only 11.29% in silty soil. The research findings can provide theoretical support for grouting engineering practices in shallow unsaturated strata.