Rock control mechanism of gangue grouting and interval backfilling in post-mining space under aquifer in China's western mining area
摘要
Existing backfill technologies prove insufficient to ensure coordinated water conservation and overburden control requirements for high-productivity longwall mining beneath aquifers in western Chinese coal fields, primarily attributed to compromised extraction efficiency and scarcity of conventional backfill materials. This necessitates innovative advances in backfill theory and technology to achieve non-interference between mining and backfilling, as well as secure mining operations under aquifers in one unified process. This research proposes a method of gangue grouting and interval backfilling in post-mining space. A gangue fluidised grouting diffusion simulation system is developed, and the diffusion characteristics and laws of gangue slurry in the mining space are tested. A numerical model of gangue grouting and interval backfilling in post-mining space is established, and the deformation and stress evolution laws of key aquiclude strata at different equivalent backfilling rates are studied, revealing the control mechanism of gangue grouting interval backfilling for rock layers under aquifers in mining space. The research results demonstrate that the method of gangue grouting and interval backfilling in post-mining space and its key parameters are proposed, with the equivalent backfilling rate defined to characterise the volume of grouted filling. The gangue slurry exhibits significant lateral and longitudinal extension during its spread in the mining space. The lateral spreading range of the slurry shows an approximately linear growth trend from top to bottom, with a final distribution shape resembling a circular table. As grouting pressure increases, both the lateral and longitudinal extension of the gangue slurry are gradually enhanced. The lateral diffusion diameter decreases with increasing slurry concentration. The subsidence reduction rate of key aquiclude strata increases exponentially as the equivalent backfilling rate rises. An equivalent backfilling