Roof collapse in a retained top coal roadway induced by high-energy seismic events: implications from a case study

Fully mechanized top-coal caving inevitably results in a certain thickness of retained coal above the roadway, which compromises roof stability and increases the difficulty of roof management. This study presents a dynamic disaster phenomenon in the Binchang mining area of China, where high-energy seismic events (HESEs) induced roof collapse in roadways with retained top coal. Disaster characteristic analysis indicates that in high-stress zones, the support system in roadways with retained top coal gradually deteriorates under mining-induced stress loading, and HESEs lead to roof support failure and roof collapse. A mechanical model of the anchored coal mass in the roof was established, and a dynamic instability criterion for the roadway roof was derived by considering the mode of dynamic disturbance. PFC2D simulations show that when the lateral pressure coefficient exceeds 1.25 and a HESE occurs within 17 m of the roadway, 84.19% of the total kinetic energy is contributed by the vertical velocity component, greatly intensifying roof damage. However, compared with conventional support, the extended cable bolt design reduces dynamic energy by 57.41%. The results imply that roof collapse in retained top coal roadways induced by HESEs can be significantly reduced by eliminating dynamic sources through main roof fracturing and enhancing roof reinforcement with extended cable bolts.