Study on the failure law of overlying rock under coal seam in close distance coal seam and feasibility discrimination of upward mining
摘要
Upward mining of close-distance coal seams is technically challenging due to the complex nature of overburden failure and the potential hazards associated with water and gas. This study assesses the feasibility of mining the 4–3 seam above the 4–4 seam at the Hongliulin Coal Mine using a combined analytical, numerical, and field-based approach. An elastic mechanics model was developed to estimate the maximum roof instability depth, and a correction was introduced to account for mining height and caving features. A discrete element model (3DEC) was then used to simulate the deformation and fracture evolution of the overburden. Finally, two boreholes were drilled to observe the caving and fractured zones for field verification. Results show that the maximum instability depth calculated ranges from 12.46 to 16.00 m, while field measurements give a caving height of 14.43 m, indicating good agreement among theory, simulation, and observation. The overlying coal seam remains stable with limited inclination and deformation, confirming the feasibility of upward mining under the studied geological setting. This integrated method provides a practical framework for upward mining assessment. The study also notes limitations in parameter variability and limited sampling, highlighting the need for further data collection and risk control. The findings offer valuable guidance for safe and efficient mining in close-distance seams.