Stress and microseismic activity in hard roof thick coal seams under varying mining rates.

To clarify the influence of mining rates on the fracturing of hard roofs in thick coal seams and the patterns of microseismic activity, a comprehensive approach combining field investigations, numerical simulations, and on-site validation was adopted. This study revealed the stress and energy evolution laws of hard roofs in mining faces under different mining rate effects, elucidated the spatiotemporal distribution characteristics of microseismic events under varying mining rates, and subsequently optimized the mining rates for different rock burst risk zones in the working face to ensure safe and efficient mining operations. Furthermore, the study optimized the mining rates for different rock burst hazard zones in the working face. The results indicate that as the mining rate of the working face increases, the peak abutment pressure ahead of the coal wall shifts closer to the exposed surface, leading to an increase in the accumulated elastic energy in the roof, which raises the likelihood of inducing rock bursts. Under low-speed mining, microseismic events are predominantly distributed ahead of the coal wall, while under high-speed mining, they are primarily concentrated behind it. On-site validation demonstrated that controlling the mining rates for moderate and low rock burst hazard zones at 6.4 m/d and 4.8 m/d, respectively, resulted in both the frequency and energy of microseismic events remaining at relatively low levels, thereby achieving the objective of ensuring safe and efficient mining operations.