Underground coal mining induces significant surface deformation and environmental damage, particularly in deeply buried mining areas with thin bedrock and thick alluvial layers. Based on the case study of the Zhaogu No.2 coal mine in Xinxiang City, Henan Province, China, this study employs a comprehensive research methodology, integrating field investigations, numerical simulations, and theoretical analyses, to explore the surface subsidence features at deeply buried mining areas with thin bedrock and thick alluvial layers, to reveal the effect of alluvial thickness on the surface subsidence characteristics. The findings indicate that the surface subsidence areas span 4.2 km2 with an advanced influence distance of 540 m. The rate of surface subsidence primarily depends on the panel's position and its advancing rate. Moreover, the thickness of the alluvial layer amplifies both the extent and magnitude of surface deformation. The displacement of overlying rock primarily exhibits a two-stage progression: the thin bedrock control stage and the alluvial control stage. In the thin bedrock control stage, surface subsidence initiates with relatively low subsidence values and amplitudes. Subsequently, in the alluvial control stage, surface subsidence accelerates, leading to a rapid increase in both subsidence values and amplitudes. These characteristics of rock formation displacement result in distinct phases of surface subsidence. Furthermore, the paper addresses the utilization of surface subsidence areas and proposes a method for calculating reservoir storage capacity in these areas. According to calculations, the storage capacity amounts to 1.05e7 m3. The research findings provide valuable insights into the surface subsidence laws in regions with similar geological conditions and practical implications for the management and utilization of subsided areas.

Investigating deformation and failure mechanisms in shafts and roadways due to rock subsidence is crucial for preventing structural failures in underground construction. This study employs FLAC3D software (vision 5.00) to develop a mechanical coupling model representing the geological and structural configuration of a stratum-shaft-roadway system. The model sets maximum subsidence displacements (MSDs) of the horsehead roadway's roof at 0.5 m, 1.0 m, and 1.5 m to simulate secondary soil consolidation from hydrophobic water at the shaft's base. By analyzing Mises stress and plastic zone distributions, this study characterizes stress failure patterns and elucidates instability mechanisms through stress and displacement responses. The results indicate the following: (1) Increasing MSD intensifies tensile stress on overlying strata results in vertical displacement about one-fifth of the MSD at 100 m above the roadway. (2) As subsidence increases, the disturbance range of the overlying rock, shaft failure extent, and number of tensile failure units rise. MSD transitions expand the shaft failure range and evolve tensile failure from sporadic to large-scale uniformity. (3) Shaft failure arises from the combined effects of instability and deformation in the horsehead and connecting roadways, compounded by geological conditions. Excitation-induced disturbances cause bending of thin bedrock, affecting the bedrock-loose layer interface and leading to shaft rupture. (4) Measures including establishing protective coal pillars and enhancing support strength are recommended to prevent shaft damage from mining subsidence and water drainage.