Composite solid sand reinforcement grouting material preparation and diffusion characteristics of slurry-water replacement grouting

The complexities of geological conditions and the intensifying disturbances from mining in deep mines present significant challenges to safety and stability, particularly in controlling groundwater disasters and ensuring rock mass stability. To address these issues, especially the instability, fluidity, and high water pressure of Cenozoic sand layers above deep coal seams, a novel green grouting material has been introduced. This eco-friendly material combines calcined coal gangue powder and fly ash as Material A with a chemical slurry of silica sol as Material B, enhanced with curing agents and catalysts. Utilizing the Box-Behnken design within the response surface methodology, the physical and chemical properties of the raw materials were thoroughly investigated. This approach led to an optimal mix ratio: 33.2% coal gangue, a water-cement ratio of 0.756 for Material A, and an equal mass ratio of Materials A and B. The study revealed a direct correlation between the amount of slurry in the solidified mixture and its compressive strength, and an inverse relationship with its permeability, confirming the grouting's transformative effect on the sand layer. Further analysis using COMSOL's porous medium two-phase flow module examined the diffusion characteristics of the grouting material in the water-bearing sand layer. The research focused on the grouting diffusion mechanism under drainage pressure and optimized the positioning and spacing of the drainage pipe layer. These findings offer a pioneering method for the grouting reinforcement of deep wells and thick, loose strata, advancing the field of deep mining safety and stability.