采动条件下底板潜在导水通道形成的微震监测与数值模拟

Microseismic monitoring and numerical simulation of the formation of water inrush pathway caused by coal mining

以某矿综放工作面开采过程为背景,利用微震监测技术进行现场监测,并借助有限差分FLAC^(3D)进行数值分析,研究在采动应力场不断变化过程中底板岩体微震破裂事件的时空演化规律,揭示煤层采动条件下潜在导水通道的孕育、发展和贯通过程.微震监测结果表明:微震事件数一定程度上反映了开采扰动对底板岩体破坏程度的影响;采煤期间,回采工作面附近微震事件呈现密集分布,底板岩体采动破坏严重,底板破裂深度达15m.数值分析表明:由于煤层采动导致采场周围应力重分布,工作面前方应力增高,采空区下方应力降低,底板岩体随工作面回采经历了应力集中、释放并最终破坏;底板塑性破坏区深度达14m.

Based on the condition of a fully-mechanized working face, two research means, i. e. microseismic monitoring and FLAC3D numerical simulation, were introduced to study the formation and evolution of floor failure and water conducted pathways caused by coal mining. The space-time evolution law of microseismic rupture events was studied for the floor rock mass during the changing process of the mining stress field. The process of inoculation, development and penetration of potential water channels was also revealed under the condition of coal mining. Field microseismic monitoring shows that microseismic event accumulation is directly proportional to drilling footage. The number of microseismic events to some extent reflects the disturbance degree of mining activities on the floor rock. The distribution of microseismic events is intensive near the coal mining face, which shows that the floor rock mass is seriously damaged during coal mining. The greatest failure depth of the floor estimated from mine microseismic monitoring is 15 m. Numerical analysis indicates that due to mining disturbance effect, the rock stress around the mine stope is redistributed during coal mining. The abutment pressure increases in front of the coal mining face and the stress reduces in the mined areas. Stress concentration and release make contribution to the destroying of the floor rock. The maximum failure depth is up to 14 m calculated from numerical simulation.