Using physical model test and numerical simulation for revealing the mechanism of stope collapse: a case study

After large-scale backfilling, understanding and controlling the collapse behavior of the roof and surrounding rock remain critical challenges in underground metal mining. Based on field investigations, an arch thickness formula for the collapsed pressure arch was derived. Laboratory-scale similarity experiments were conducted to study the collapse mechanisms following goaf failure, with particular focus on the dynamic impact characteristics and spatial influence range of roof and surrounding rock failure. The discrete element method was employed to analyze the dynamic failure process and stability evolution, leading to the design of an in-situ grouting reinforcement scheme. The results demonstrate that the newly developed grouting mold and method enhance both the efficiency and accuracy of similarity simulations. The failure patterns observed in the physical tests adequately represent the collapse characteristics of roof and surrounding rock under complex engineering conditions. The 3DEC simulation results show good agreement with the similar simulation experiments, both revealing a U-shaped collapse zone and similar displacement distribution characteristics, with the maximum displacement occurring at the roof. Under vertical load, the goaf collapsed instantly, showing prominent collapse impact characteristics; the slurry reinforcement method was consistent with the field application effect. It verifies the feasibility of the comprehensive method in studying roof and surrounding rock control methods after gob collapse in a large-scale backfill environment.