近直立特厚煤层采动应力分层分区特征及对矿压活动的影响规律

Stratification and zoning characteristics of mining-induced stress in nearly vertical ultra-thick coal seam and its influence on mine pressure activity

  • 摘要: 明确近直立特厚煤层采动应力时空演化特征是研究矿压显现规律和防治冲击地压的关键科学问题。以乌东煤矿为研究背景,综合采用数值模拟和现场监测分析的方法,系统研究了近直立特厚煤层水平分段开采的采动应力空间分布特征、微震活动时空演化规律及其与冲击显现的耦合机制,结合现场微震监测数据与5次典型冲击案例,验证了数值模拟结果的可靠性。讨论了近直立煤层矿压活动的原因,并定量对比了与水平/缓倾斜煤层在应力分布模式、震源机制及冲击特征的本质差异。研究表明:近直立特厚煤层采动应力场呈现典型三维非对称分布,水平构造应力主导的应力集中区具有显著分层分区特性。垂直方向上,开采层位下方形成范围25 m的应力集中带,峰值位于层位下方8 m;走向上,超前应力影响范围达60 m,峰值位于工作面前方10 m;倾向上,巷道两侧35 m为卸压区,上下方呈现双驼峰型应力集中区。微震事件分布呈现超前和横向扩展特征,微震频次随能级增加呈指数衰减,高能事件集中分布于工作面前方50~75 m、两侧30~40 m的高梯度应力区,能量密度与应力梯度呈显著正相关。冲击显现以巷道顶板下沉和底板鼓起为主,破坏形态与巷道上下方应力集中区强相关。不同于水平煤层垂直应力主导的工作面超前和巷道两侧应力集中以及顶板破断诱发矿震扰动,近直立煤层微震事件主要源于高水平构造应力驱动下的煤岩局部破裂,形成独特的高静载+矿震扰动致灾模式,而静载集中和矿震扰动区近似重叠,导致近直立煤层巷道顶底部破坏为主的冲击显现特征。研究结果为明确近直立特厚煤层开采矿压规律和冲击地压特征的基础问题提供了科学依据。

     

    Abstract: The identification of the spatiotemporal evolution characteristics of mining-induced stress in near-vertical extra-thick coal seams is a key scientific issue in studying strata behavior and rockburst prevention. Taking Wudong Coal Mine as the research background, this study systematically investigates the spatial distribution characteristics of mining-induced stress, the spatiotemporal evolution patterns of microseismic activity, and their coupling mechanism with rockburst occurrence during horizontal sublevel mining in near-vertical extra-thick coal seams through numerical simulations and field monitoring analyses. The reliability of the numerical simulation results is verified using large-scale microseismic monitoring data and five typical rockburst cases. The causes of strata behavior in near-vertical coal seams are discussed, and the fundamental differences in stress distribution patterns, seismic source mechanisms, and rockburst characteristics between near-vertical and horizontal/gently inclined coal seams are quantitatively compared. The results indicate that the mining-induced stress field in near-vertical extra-thick coal seams exhibits a typical three-dimensional asymmetric distribution, with stress concentration zones dominated by horizontal tectonic stress showing distinct stratified and partitioned characteristics. Vertically, a 25 m stress concentration zone is formed below the mining level, with the peak stress located 8 m beneath the seam floor. Along the strike direction, the influence range of the abutment stress extends 60 m ahead of the working face, with a peak at 10 m. Along the dip direction, a pressure-relief zone exists within 35 m on both sides of the roadway, while the upper and lower parts exhibit a double-peak stress concentration pattern. The distribution of microseismic events shows both an advanced and lateral expansion pattern, with microseismic event frequency exhibiting an exponential attenuation trend with increasing energy level. High-energy events are mainly concentrated in high-gradient stress zones 50 to 75 m ahead of the working face and 30 to 40 m on both sides, where energy density is significantly positively correlated with stress gradient. Rockburst manifestations are primarily characterized by roadway roof subsidence and floor heave, with failure patterns strongly associated with the stress concentration zones above and below the roadway. Unlike horizontal coal seams, where vertical stress dominates stress concentration ahead of the working face and on both sides of the roadway, leading to mining-induced seismic disturbances triggered by roof breakage, microseismic events in near-vertical coal seams mainly originate from local coal-rock failure driven by high horizontal tectonic stress. This results in a unique disaster-causing mode of high static load coupled with mining-induced seismic disturbances, where the static load concentration zone and the seismic disturbance zone nearly overlap, leading to rockburst manifestations predominantly characterized by roadway roof and floor failure. The research results provide a scientific basis for clarifying the basic problems of mining pressure behavior and rockburst characteristics in near vertical extra-thick coal seam.

     

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