Collapse pits are highly susceptible to secondary hazards such as underground debris flows and slope instability under mining disturbances. These hazards significantly damage the ecological environment of the mining area. To reduce the geological hazards of collapse pits, grouting is used for management. The diffusion pattern and curing mode of slurry under different grouting pressures were investigated through indoor grouting simulation tests, and industrial tests were carried out to assess grouting effects. The results indicate that the slurry is dominated by penetration diffusion and supplemented by splitting diffusion in the moraine. The penetration distance and diffusion radius of the slurry increase linearly with grouting pressure, while the splitting uplift distance and cured volume increase exponentially with grouting pressure. Splitting diffusion consists of three stages: bulging compaction, splitting flow, and passive uplift. Horizontal splitting has a vertical uplift effect on the formation. The slurry primarily consolidates individual moraine particles into a cohesive mass by filling fractures, binding soil particles, and reinforcing interfaces with the rock mass. For different moraine layer structures, full-hole, segmented, and point-based grouting methods were applied. A composite grouting technique, layered grouting with ring solidification, was also introduced, achieving excellent grouting results. This study provides technical support for managing geological hazards in collapse pits caused by block caving mining disturbances and for green mining practices.

Coal occupies a dominant position in China's energy structure. However, overburden failure is the root cause of several safety and environmental issues. With the successive proposals of green mining and the dual-carbon strategy, the green development of coal-based energy has become the priority development direction. Overburden grout injection has become the preferred choice in the green mining technology system. The potential ecological health risk of heavy metal contamination in fly ash matrix soil was analyzed and evaluated in Xinyi coalmine. It is pointed out that only using fly ash as grouting material may cause irreversible harm to groundwater system. Based on the solid waste utilization and sustainable development, the close packing theory was adopted to determine that poorly graded gangue can be used as filling aggregate. Meanwhile, the passivation characteristics of loess to reduce the heavy metal in fly ash by increasing the water-stable aggregate content were elucidated. The properties and parameters of grouting materials composed of gangue, loess, and fly ash were analyzed, and a reasonable upper limit of slurry concentration was determined to be 72%. The field application indicates that the maximum surface subsidence is 473 mm, and the damage degree of buildings is within grade I, liberating 163 Mt of coal resources under the buildings. The harmless treatment of solid waste has been achieved, effectively reducing the negative external impact of coal mining. It is equivalent to saving 95.95 million yuan while promoting the green, safe, and sustainable development of coal enterprises.