急倾斜巨厚煤层复杂空间结构区微震时空演化规律及诱冲机理

Temporal and spatial evolution law of microseisms and induced impact mechanism in complex spatial structure area of steep and extremely thick coal seam

煤矿冲击地压灾害的发生与空间结构密切相关,尤其在复杂空间结构区灾害发生更频繁。掌握煤层开采复杂空间结构区煤岩灾变规律并揭示其发生机制对于冲击地压防控具有重要意义。以乌东煤矿为研究背景,采用数值模拟、微震监测、理论分析等方法,研究了岩柱应力异常尺寸效应,分析了复杂空间结构区微震时空演化规律,揭示了复杂空间结构下冲击地压发生机理,评估了煤层开采不同区域的冲击危险性。研究结果表明:①急倾斜岩柱厚度更窄、出露高度更大其撬动效应更强,岩厚变异应力异常形成5个分区。②岩柱厚度更窄区域微震频次更多,能量更高,时空活动度更强,离散性更高。高应力区、应力梯度区、应力平稳区依次呈现“低频次-高能量”、“高频次-高能量”、“低频次-低能量”的微震响应特征。③特殊空间结构区域微震事件簇集且能级增大,时空活动度及离散性陡增,尤其在结构边缘该特征更明显,能量积聚及释放速率增大,冲击地压发生的概率及强度更高。位于岩柱更窄区域的特殊空间结构内微震活动更剧烈。④岩柱厚度越窄(煤柱高度越大)则岩柱向深的弯矩及能量增长速率越快,冲击危险性更高。依据结构面强度效应推断出断裂带发生滑移错动,是能量积聚与释放的优势区域。揭示冲击地压发生机理为高静载及低临界载荷共同作用,基于应力集中特征评估煤层开采不同区域的冲击危险性。

The occurrence of coal mine rock burst disasters is closely related to the spatial structure,especially in the com-plex spatial structure area.It is of great significance to master the law of coal and rock catastrophe and reveal its mechan-ism in the complex spatial structure area of coal seam mining for the prevention and control of rock burst.Taking the Wudong Coal Mine as the research background,using numerical simulation,micro-seismic monitoring,theoretical analys-is and other methods,the abnormal size effect of rock pillar stress is studied,the temporal and spatial evolution law of mi-croseisms in the complex spatial structure area is analyzed,the mechanism of rock burst under the complex spatial struc-ture is revealed,and the impact risk in the different areas of coal mining is evaluated.The research results show that:①The steeply inclined rock pillar with narrower thickness and higher exposed height has stronger prying effect,and the abnormal stress of rock thickness variation forms five divisions.②The area with narrower rock pillar thickness has more micro-seismic frequency,higher energy,stronger spatio-temporal activity and higher dispersion.The high stress region,the stress gradient region and the stress plateau region show the micro-seismic response characteristics of“low frequency-high energy”,“high frequency-high energy”and“low frequency-low energy”in turn.③The micro-seismic events in spe-cial spatial structure area are clustered and the energy level increases,and the temporal and spatial activity and dispersion increase sharply.This feature is more obvious especially at the edge of the structure,the energy accumulation and release rate increases,and the probability and intensity of rock burst are higher.The micro-seismic activity of special spatial struc-tures located in the narrower area of rock pillars is more acute.④The narrower the thickness of rock pillar(the greater the height of coal pillar),the faster the growth rate of bending moment and energy in the depth of rock pillar,and the higher the impact risk.According to the strength effect of structural plane,it is inferred that the fault zone has slip and disloca-tion,and fault zone is the dominant area for energy accumulation and release.It is revealed that the mechanism of rock burst is the joint action of high static load and low critical load.The impact risk in the different areas of coal mining is evaluated based on stress concentration characteristics.