Research and development of gold mine paste filling materials in the Dandong region and their role in controlling abandoned mine area stability and surface subsidence

The extensive abandoned mine voids formed during historical artisanal mining constitute a critical factor constraining both safety production in metal mines and surface stability. A gold mine in the Dandong region developed complex room-and-pillar abandoned voids and surface subsidence areas during its early artisanal mining phase, necessitating systematic assessment and remediation of its long-term stability and potential subsidence risks. Therefore, this paper uses the gold mine as an engineering case study, focusing on the development of paste filling materials and their role in controlling the stability of abandoned areas and surface subsidence. First, based on principles of material availability, cost-effectiveness, and engineering adaptability, a gangue-like paste filling material was developed using coal gangue, fly ash, and ordinary Portland cement as primary raw materials. A rational mix design was determined using particle size distribution theory. Subsequently, a similar model of the room-and-pillar mining area was constructed based on similarity theory and the Froude similarity criterion. The flow, settlement, and compaction characteristics of the paste filling slurry within the complex pillar structure were systematically investigated, revealing the spatial distribution patterns of the filled body’s geometric morphology, ultimate flow distance, and compaction rate. Ultrasonic non-destructive testing was further introduced to monitor wave velocity evolution in different filling zones, quantitatively evaluating the static segregation resistance of the paste filling slurry. Finally, integrating FLAC3D numerical simulations, the study comparatively analyzed the evolution characteristics of the surrounding rock stress field, displacement field, and plastic zone under unfilled and filled conditions in the goaf. Results indicate that paste filling significantly reduces roof deformation and surface settlement in the goaf, with surface settlement decreasing from approximately 15 mm to about 5 mm, while the extent of the surrounding rock plastic zone is markedly constrained.