Abstract:
During the process of reclaiming residual coal resources in integrated mines, the existing abandoned adits and areas damaged by small-scale mining operations are characterized by irregular spatial configurations, missing boundary data, fractured roof structures, and complex stress environments. The morphology of these cavities, their internal damage conditions, and their spatial relationships with the working face roadways are highly concealed, making them prone to triggering sudden roof collapses, support instability, and advancement obstructions when the working face passes through these areas. To address the difficulty in accurately identifying the spatial structures of abandoned roadways and small-scale mining-damaged zones, the lack of targeted remediation methods, and the difficulty in ensuring safety during re-mining, a large-space visual inspection and sensing device integrating video imaging, laser ranging, and pan-tilt attitude control was developed using the 13204 fully mechanized top-coal caving face at Chejiazhuang Coal Mine as the engineering background. A multi-source collaborative detection system combining geophysical exploration, drilling, inspection, and geochemical exploration. A segmented and layered backfilling technique for re-mining was proposed, combining the complete backfilling of abandoned drifts with the layered backfilling of areas damaged by small-scale mining. Key backfilling parameters and the effectiveness of the engineering application were verified through theoretical calculations, numerical simulations, and on-site monitoring. The results indicate that the developed large-space inspection and sensing device can simultaneously acquire video images and distance data within hidden cavities inaccessible to personnel. Once the device enters a cavity, it can commence operations and perform multi-angle scans. Through repeated fitting of cavity cross-sections, the device can reconstruct the overall contour of small-shaft mining damage zones, providing empirical evidence for identifying the location, morphology, boundaries, and spatial parameters of empty drifts and small-shaft mining damage zones. Survey and mining operations at the 13204 working face revealed a total of 11 small-scale mining damage zones and 27 abandoned adits within the working face, with a cumulative length of approximately 2,000 m and a total cavity volume of approximately 9,600 m
3. The abandoned drifts and mine tunnels are interconnected or intersect. In some areas of the small-scale mining damage zones, over-mined high voids and accumulations of collapsed rock have formed, which significantly affect the location of roof fractures, the stability of the support structures, and the continuous advancement of the working face. Based on the differences in the spatial structures of the abandoned drifts and the small-scale mining-damaged areas, a zoned backfilling remediation plan was proposed: for clusters of abandoned drifts, structural reinforcement was achieved through sealing, grouting, and complete backfilling, with the critical strength of the backfill material determined to be 2.23 MPa. For the small-scale mining-damaged areas, layered backfilling was employed to improve the load-bearing conditions of the roof in the fractured zones, with the critical backfill height determined to be 7 m. After backfilling, the backfill material and the surrounding coal and rock mass formed a synergistic load-bearing structure, reducing high stress concentrations around the abandoned tunnels and small-scale mining-damaged zones and leading to a more balanced stress distribution in the surrounding rock mass. Field application demonstrated that during the 13204 working face’s passage through the empty drift and the small-scale mine-damaged zone, support resistance remained generally stable, with no occurrence of severe mining pressure phenomena such as roof collapse, support crushing, or large-scale pressure surges; the operation achieved a cumulative safe increase in coal production of 105.6×10
4 t. The research findings form an integrated technical pathway for precise identification, zoned remediation, and safe mining, which can provide a reference for the safe recovery of residual coal resources in similar abandoned roadways and small-scale mining-damaged zones left by small-scale mining operations.