Dynamic Damage Evolution of Surrounding Rock Mass in Super-Large Room-and-Pillar Mining of Metal Mines

In deep metal mines, repeated blasting during ore extraction causes progressive damage to surrounding rock masses that accumulates under long-term loading and may ultimately lead to rock mass instability. This study investigates the damage characteristics of the overlying rock mass under static and dynamic loads through integrated laboratory testing, physical modeling, and FLAC3D numerical simulations. Taking the large-scale mining operations at Luohe Iron Mine as a case study, the dynamic damage evolution of the overlying rock mass is examined under multi-panel, multi-stope mining conditions. Results indicate that one-step mining produces minimal damage and subsidence in the surrounding rock mass, whereas two-step mining significantly increases both the extent of damage and the magnitude of subsidence. The most severe damage occurs at the inter-layer rock beams and at the roof and floor of mining panels. This intensified damage reflects the combined effects of frequent dynamic loading and inter-layer damage superposition, which together exceed the damage produced under static loading alone and become the dominant factor controlling rock mass damage. Under sustained loading, blast-damaged rock masses exhibit a characteristic deformation pattern, converging inward from the lateral boundaries toward the central floor.