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煤柱蠕变失稳诱冲机理与防治体系

Mechanism and prevention and control system of coal pillar creep instability inducing rockburst

  • 摘要: 针对采区上(下)山中间煤柱在无明显采掘扰动条件下,冲击地压事故频繁出现的问题,以赵楼煤矿、耿村煤矿多次发生的煤柱冲击地压事件为例,开展煤柱蠕变诱发冲击地压的机理研究,由于此类事故的发生往往表现出显著的“滞后性”,因此卸压时机难以把握,发生机理尚难明确,使这种冲击地压事故成为一种典型的隐蔽性灾害,对煤矿的安全高效开采构成严重威胁。以煤体蠕变力学特性分析为基础真三轴煤体蠕变声发射试验为依据,构建了煤岩体蠕变失稳与冲击力学模型,试验结果表明:高地应力作用是煤柱发生“滞后型”冲击地压的必要条件,并得出了煤柱进入加速蠕变诱发冲击地压的力学判定标准和能量判定标准;真三轴蠕变试验中,三向应变曲线与声发射(AE)事件的时空分布存在内在耦合;蠕变失稳本质是应变能积累−耗散的失衡过程,可从“能量−损伤”角度揭示灾变前兆;当煤柱长期处于应力峰值的85%及以上时,蠕变作用会使煤柱内部逐渐储存大量弹性应变能,当达到煤体长期强度时,即发生失稳冲击。通过FLAC3D数值模拟软件引入改进的Burgers本构模型,模拟计算得出了真实地应力条件下进入加速蠕变的时间节点,为后续卸压时机的掌握提供指导。根据此类冲击事故的发生机理,提出了针对性的煤柱深孔爆破卸压防治措施,建立了此类冲击地压事故的防治技术体系。

     

    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 FLAC3D 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.

     

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