Abstract:
To address the issue of frequent rock bursts in intermediate coal pillars of mine district inclines (rises and dips) under conditions of no obvious mining disturbance, this study investigates the mechanism of rock bursts induced by coal pillar creep, taking multiple coal pillar burst events in Zhaolou Coal Mine and Gengcun Coal Mine as examples. Since such rock burst accidents often exhibit significant “latency-type” rockburst, the timing of pressure relief is difficult to grasp, and their occurrence mechanism remains unclear, making them a typical concealed disaster that poses a serious threat to the safe and efficient mining of coal mines. Based on the analysis of the creep mechanical properties of coal and the true triaxial creep acoustic emission (AE) tests on coal, this paper establishes a mechanical model of creep instability and rock burst in coal-rock mass. The test results show that high in-situ stress is a necessary condition for the occurrence of “latency-type” rockbursts in coal pillars, and the mechanical and energy criteria for determining rock bursts induced by coal pillars entering accelerated creep are derived. In true triaxial creep experiments, there is intrinsic coupling between the triaxial strain curves and the spatiotemporal distribution of acoustic emission (AE) events. The essence of creep instability is an unbalanced process of strain energy accumulation and dissipation, and catastrophic precursors can be revealed from the perspective of “energy-damage”. When coal pillars are subjected to 85% or more of the peak stress for a long time, creep will gradually lead to the accumulation of a large amount of elastic strain energy inside the pillars; instability and burst will occur once the long-term strength of coal is reached. By introducing the improved Burgers constitutive model into the FLAC
3D numerical simulation software, the time nodes for entering accelerated creep under actual in-situ stress conditions are obtained through simulation calculations, providing guidance for grasping the subsequent pressure relief timing. According to the occurrence mechanism of such burst accidents, targeted prevention and control measures of deep-hole blasting for pressure relief in coal pillars are proposed, and a prevention and control technology system for such rock burst accidents is established.