基于微震监测的煤矿突水前兆特征及其数值计算研究

The water inrush catastrophe in coal mines is essentially the result of mining-induced progressive failure to instability of coal and rock masses, and the diffusion of micro-cracks to cascade through catastrophe. The static mechanism of the catastrophe gestation of water inrush in coal mines is investigated by means of numerical analysis based on failure process simulation. The dynamic evolution characteristics of micro-cracking precursor laws of inrush in coal mines are revealed under mining conditions using microseismic monitoring. Breaking through the single application of microseism to location of coal and rock mass damage, four source parameters, i.e. microseismic source location, source dimension, source direction and rupture velocity, are adopted to establish displacement and stress jump model of micro-cracks. The element stiffness of coal and rock masses is weakened to realize the real-time feedback calibration of micro-cracking information to damage mechanical parameters. Then, a numerical computation method considering the feedback of micro-cracking damage of coal and rock masses is proposed, which is used to study the catastrophe mechanism and precursor laws of water inrush in coal mines from the perspective of the combination of dynamic and static state. The research results will be of great significance to perfect the catastrophe theory of water inrush in coal mines, break the threat of water disaster the coal mines suffer and guarantee the safe production of coal in China

煤矿突水灾变本质上是开采诱发煤岩体渐进破裂到失稳，弥散微破裂到串级贯通灾变的结果。本项目采用基于破裂过程模拟的数值分析方法来研究煤矿突水灾变孕育的静态力学机制；以微震监测为手段来揭示采掘条件下煤矿突水灾变微破裂前兆规律的动态演化特征。突破微震对区域煤岩体损伤定位的单一作用，采用微震震源位置、震源尺度、震源方向和破裂速度四种参数，建立微破裂位移与应力跳跃模式，弱化煤岩体单元刚度，实现微破裂信息对损伤力学参数的实时反馈标定，进而提出一种基于煤岩体微破裂损伤反馈的数值计算方法，从动静结合的角度研究煤矿突水灾变机理与前兆规律。其成果对完善煤矿突水灾变基础理论，破除煤矿所受的水害威胁，保障我国煤矿安全生产具有重要的意义。

煤矿突水灾变本质上是开采诱发煤岩体渐进破裂到失稳，弥散微破裂到串级贯通灾变的结果。本项目采用基于破裂过程模拟的数值分析方法来研究煤矿突水灾变孕育的静态力学机制；以微震监测为手段来揭示采掘条件下煤矿突水灾变微破裂前兆规律的动态演化特征。以董家河煤矿工作面为例，通过工作面布置的微震监测系统，采用矩张量理论反演了底板微震事件异常区域的震源机制解，通过应力反演方法识别了底板隐伏断层，并结合数值模拟获取了底板的应力场。提出一种基于煤岩体微破裂损伤反馈的数值计算方法，从动静结合的角度研究煤矿突水灾变机理与前兆规律。研究表明：（1）工作面过断层前断层浅部受压深部受拉，破坏方向为沿断层向上扩展；过断层后由于底板结构变形差异，断层破坏变为浅部受拉深部受压，破坏方向变为沿断层向下扩展。（2）底板变形影响断层围岩渗透特征，工作面临近断层过程中断层处渗流量逐渐降低，过断层后随断层破坏迅速增加。（3）通过微震事件Es/Ep值判断断层围岩微破坏性质，过断层前，底板深部较厚的隔水层未发生失稳破坏，位于拉压破坏过渡区的煤层下方10~25m断层发生微破坏，微震事件Es/Ep值位于4~8之间；过断层后，最大微破坏深度为35m，微震事件Es/Ep值小于3，围岩发生拉伸破坏。通过现场数据，对矩张量反演方法及数值模拟的结果进行分析验证，其结果可为类似煤矿突水风险的预警和评估提供参考。