Abstract: Collapsed goaf poses a serious threat to deep mining safety,and the induced progressive instability of overlying strata,surface subsidence,and residual ore retention urgently require breakthrough solutions.To address this challenge,this study proposes a coupled "artificial key stratum-backfilling and mining synergy" control system based on the key stratum theo ry and synergistic mining technology,which reconstructs a structurally stable load-bearing roof to simultaneously resolve the technical challenges of collapsed goaf hazard mitigation and efficient residual ore recovery.The failure mechanism of overlying strata in collapsed goaf is analyzed based on the key stratum theory.Taking a fluorite mine in Inner Mongolia as a case study, an innovative multi-parameter-constrained pillarless mining-backfilling replacement scheme is proposed by integrating the syn ergistic mining concept,achieving full coupling of material flow and spatial flow to ensure stope stability.The competitive and unstable factors of the collapsed goaf system and their control parameters are systematically investigated.According to different overlying strata instability and pillar failure conditions,hazard control measures and 4 types of pillarless mining-backfilling re placement schemes are proposed.The results show that the "artificial key stratum" as a regenerated roof can effectively control surface subsidence and ensure deep mining safety,while the application of backfilling and mining synergy technology enables safe and efficient recovery of fragmented ore.This study provides scientific guidance and technical support for goaf treatment and residual ore recovery in similar mines.

Key words: collapse of mine and rock,treatment of hidden hazard in goaf,recovery of residual ore,synergistic mining technology