Energy instability mechanism of existing goaf roof under impact load

The stability and fracture behavior of a goaf roof beneath an open-pit bench are critical concerns, especially under impact loading. However, the effect of the thickness-to-span ratio on dynamic failure modes remains largely unexplored, as existing research focuses mainly on static stability. Energy dissipation and instability evolution under impact loading require further study. To address this gap, this study conducts drop-weight impact experiments on specimens with circular perforations, complemented by numerical simulations. By integrating dimensional analysis, cusp catastrophe theory, and strength reduction techniques, the dynamic instability mechanism of goaf roofs with varying thickness-to-span ratios is revealed. Results show that the thickness-to-span ratio significantly influences energy accumulation and dissipation during roof failure. A higher ratio increases both the magnitude and rate of energy dissipation, particularly during crack initiation and stable propagation, while its impact diminishes in the final failure stage. Optimizing the thickness-to-span ratio within a critical range enhances structural stability, improving the safety factor by up to 83%. However, beyond a certain threshold, additional thickness yields diminishing benefits. This study provides new insights into the energy-based instability mechanism of goaf roofs under impact loads, establishing a theoretical foundation for early warning systems and optimized safety design.