Deformation characteristics of weakly cemented overburden in Western mining areas in China

Understanding the deformation behavior of weakly cemented overburden in western coalfields is critical for assessing mining-induced instability and groundwater hazards. Taking the 23 - 2 coal seam of Yili No. 4 Mine as the research object, this study integrates FLAC3D numerical simulations with high-precision transient electromagnetic field monitoring data to quantify the influence of mining thickness and face advance on overburden responses. The actual mining thickness of the target coal seam is 9.5 ~ 10 m, and the mining depth ranges from 150 m to 1000 m. Results reveal a characteristic "progressive growth-stabilization" evolution of vertical displacement, with the maximum vertical displacement reaching 2.2 m when the working face advances to 600 m. Meanwhile, a distinct development of the caving zone, water-conducting fracture zone, and plastic deformation zone is observed. The caving zone stabilizes at a height of 30 m with a caving-to-mining ratio of 3.0 when the working face advances beyond 260 m. The water-conducting fracture zone stabilizes at a height of 45 ~ 52 m, corresponding to a fracture-to-mining ratio of 4.7-5.3. The heights of these zones exhibit strong sensitivity to mining thickness and depth, reflecting the inherent mechanical vulnerability of weakly cemented strata. The close agreement between simulation outputs and in situ measurements confirms the robustness of the modeling framework. Overall, this work provides essential quantitative parameters for water-inrush prevention in western mining areas, offering scientific guidance for designing waterproof coal-pillar heights (≥ 52 m) and predicting fracture-zone propagation during mining operations.