Research on the influence mechanism of multiple mining of extremely thick coal seams on the damage of overburden and the load - bearing structure

The stability of overburden structure during slicing mining is critical for extra-thick coal seam extraction. Taking the Zhundong Mining Area as the background, this study integrates numerical simulation, theoretical analysis, and physical simulation to investigate the evolution of overburden structure, rock block size distribution, and force chain network characteristics. Results show that as slicing numbers increase, the near-field overburden transforms from discrete blocks into granular materials, following a structural evolution sequence of “masonry beam—short masonry beam—extrusion equilibrium arch.” Repeated mining causes degradation of the low-level bearing zone, with force chain strength progressively diminishing. Cumulative mining effects—including shortened rock blocks, increased transferred loads, and exacerbated internal damage—lead to instability of the bearing structure. Consequently, the loss of bearing capacity in the low-level key stratum forces the bearing structure to migrate upward, transforming from a “beam-type” to an “arch-type” system. Based on the concept of “enhancing bearing structure stability,” a full-life-cycle mine pressure control system for slicing mining of extra-thick coal seams is established.