107 / 2023-06-15 17:00:18

Mechanism and prevention of rockburst induced within the underlying coal face when passing through overlying goaf boundary area

Rockburst mechanism; Multi-seam mining; Goaf boundary; Hard roof; Overburden movement; Rockburst control

Rockbursts pose serious threats to mine safety. In this paper, rockburst of the underlying coal face passing through the overlying goaf boundary area has been investigated by comprehensively employing theoretical analysis, numerical simulation, and on-site real-time monitoring methods. Furthermore, the nature of the overburden rock movement and stress evolution at different mining stages have been examined. The physical and mechanical models are constructed. The calculation formula of rockburst at the boundary area of the goaf is derived. The analysis of the obtained results shows that two types of rockburst, i.e. dynamic coal pillar instability type and key block rotary movement type, are induced when the underlying coal face passes through the boundary area of the overlying goaf. When the superposition of the coal face advancing induced stress and the boundary supporting stress induced by overlying goaf exceeds the bearing capacity of the coal pillar, the dynamic coal pillar instability burst is induced. The key block rotary motion burst is induced by the overburden rock formation of an unstable masonry beam structure with three key blocks hinged. When the rotary motion space of the masonry beam structure is reached, the first key blocks near the coal face has the rotary instability movement, causing the coal pillar to break, and inducing the second and third key blocks to undergo the relative rotary motion. According to the rockburst mechanism and the potential range, a targeted pressure relief plan for the roof and coal seam was proposed as the preventive measure, and through the analysis of the borehole video recording results and micro-seismic monitoring data, it is evident that the pressure relief plan has played a good prevention and control effect, and the coal face passed through the rockburst danger area safely.