急倾斜特厚煤层工作面非对称冲击矿压机理

Mechanism of asymmetric coal bursts on the working face in steeply inclined and extra-thick coal seam

针对急倾斜特厚煤层水平分段综放开采工作面冲击矿压灾害,以窑街三矿为工程背景,采用离散元数值模拟(UDEC),研究了急倾斜特厚煤层水平分段开采顶板破断及结构演化规律,再现了矿震作用下工作面非对称冲击矿压孕育和发生过程;理论分析了工作面底煤应力非对称分布特征;基于动静载叠加原理揭示了工作面非对称冲击矿压发生机理;最后提出了防治对策。研究结果表明:急倾斜特厚煤层水平分段综放开采工作面在顶底板非对称错峰支承压力作用下,煤体受载特征沿倾向呈现分区差异性:顶板侧挤压、中部剪切、底板侧拉-剪。工作面底煤中形成浅部汤匙状卸压区和深部非对称应力集中区,顶板侧煤体垂直应力峰值和剪切应力峰值均为底板侧的5倍。进入深部开采后,工作面悬顶长度增大,同时采空区内关键岩块发生回转、滑移和倾倒的可能性增加,导致矿震强度增大。当动载应力与工作面底煤应力集中区中的静载应力叠加大于“煤体+液压支架”系统的极限应力时,发生急倾斜特厚煤层水平分段综放开采工作面非对称冲击矿压。研究结果与现场实测相吻合。

In view of coal bursts that occur on the horizontal section of top-coal caving mining working face in the steeply inclined and extra-thick coal seam,based on the engineering background of Yaojie No.3 Coal Mine,the evolution of roof fractures and structures during horizontal section mining in the steeply inclined and extra-thick coal seam is studied using UDEC numerical simulation.The asymmetric coal burst on the working face under the action of mining-induced seismicity is reproduced.The characteristics of asymmetric stress distribution in the bottom coal are theoretically analyzed.The mechanism of asymmetric coal bursts is proposed based on the superposition principle of dynamic and static loads. Finally,prevention measures are proposed. The results show that under the action of asymmetric peak-staggeredmining-induced stresses of the working face in the steeply inclined and extra-thick coal seam,thestress in coal shows regional differences along the inclination—compression on the roof side,shear onthe middle,and tension-shear on the floor side. A spoon-shaped pressure relief area in shallow and anasymmetric stress concentration area in deep are formed in the bottom coal. And the peak value of verticalstress and shear stress of the coal on the roof side is 5 times that of the floor side. As the miningdepth increases,the length of the hard roof increases,and the possibility of rotation,slipping,and thetoppling of the key rock blocks in goaf also increase,leading to an increase in mining-inducedseismicity. When the superposition of the static stress and the dynamic stress is greater than the ultimatestress of the“coal body+hydraulic support”system,asymmetric coal bursts occur on the horizontal sectiontop-coal caving mining working face in the steeply inclined extra-thick coal seam. The research resultsare consistent with the field measurements.