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

Abstract 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. Numerical simulation of roadway instability conducted using PFC2D shows that when the lateral pressure coefficient exceeds 1.25 and a HESE occurs within 17 m of the roadway, the vertical dynamic energy increases by 84.19%, intensifying roof damage. However, the the use of an extended cable bolt anchoring design can reduce the dynamic energy by 86%. 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.