Dynamic load response law and limit of pressure relief drilling for coal seam prevention and control of rock burst

The surrounding rock of the impact hazard roadway is often disturbed by external dynamic loads, which often leads to the occurrence of impact ground pressure. In order to explore the anti impact and pressure relief effects of large-diameter pre relief boreholes in coal seams under dynamic load disturbance conditions, a comprehensive method including theoretical analysis, laboratory experiments, and numerical simulations was used to study the dynamic load response law and limit of coal seam anti impact and pressure relief boreholes. The results indicate that the coal body in the pressure relief zone of large-diameter drilling forms a weak structure, increases the ability to attenuate dynamic loads, and reduces the possibility of impact. Under low dynamic load disturbance, the expansion of pores and cracks, and the cumulative acoustic emission events show an upward trend with the increase of disturbance period; Under higher dynamic load disturbances, the degree of damage and rupture of coal samples in boreholes intensifies, and acoustic emission events are mainly high-energy. As the dynamic load level and disturbance period increase, the distance between the stress concentration zone, elastic high-energy zone and the borehole shortens, the influence range increases, the rock movement trend strengthens, and the degree of elastic energy accumulation increases. Under low dynamic load level disturbances, drilling plays a role in energy dissipation, pressure relief, and anti-collision, which can maintain the stability of the surrounding rock. However, under high-energy dynamic load disturbances, the anti-collision of large-diameter drilling fails, and the drilling wall is prone to dynamic instability and damage, causing instability of the surrounding rock. Overall, large-diameter pressure relief boreholes have weakened structures that can dissipate energy, reduce impact, and lower the degree of dynamic load disturbance. However, under high-energy and high-frequency dynamic load disturbances, the movement trend of the surrounding rock of the pressure relief borehole increases, the degree of fracture response is severe, and the anti impact effectiveness is limited.