复合厚煤层巷道掘进冲击地压机制及监测预警技术

Mechanism and monitoring and early warning technology of rock burst in the heading face of compound thick coal seam

  • 摘要: 针对我国西部矿区复合厚煤层工作面掘进期间煤粒弹射现象频繁、震动持续时间长、冲击破坏范围集中在掘进工作面附近的特点,以新疆硫磺沟煤矿复合厚煤层巷道掘进为工程背景,采用现场调研、理论分析和现场监测等方法,对复合厚煤层掘进工作面煤粒弹射和冲击地压发生机制及监测预警技术进行了研究。 复合厚煤层掘进工作面频繁发生煤粒弹射和冲击地压的主要原因是巷道开挖后围岩中软煤部分会快速卸荷破坏产生煤粒弹射现象,软煤破坏后导致硬煤局部产生剪应力集中,当应力集中程度超过硬煤极限强度时,硬煤发生剪切失稳破坏,进而诱发掘进掘进工作面冲击地压。现场监测结果表明,复合厚煤层掘进工作面冲击前后煤体应力及锚杆索压力监测无明显征兆,地音监测能够捕捉到冲击地压信息,但复合厚煤层工作面掘进期间频繁煤粒弹射产生的众多小能量震动事件严重影响了地音监测预警结果的准确性。 据此提出了基于“地音大事件”概念的监测预警方法,即只监测对掘进工作面冲击地压有明显影响的大能量地音事件,这些地音事件具有的明显特征为发生的总频次相对较低,但总能量较高,根据统计分析,将(4-5)04胶带巷掘进工作面能量大于1 000 mV的地音称之为地音大事件。通过与原预警方法进行对比,基于“地音大事件”概念的预警方法预警准确率更高,也更符合现场实际情况。

     

    Abstract: For the characteristics of frequent ejection of coal particles,long duration of vibration,and concentrated im- pact damage range near the heading during the excavation of the compound thick coal seam face in the western mining area of China,taking the compound thick coal seam heading face in Liuhuanggou coal mine as an engineering back-ground,the mechanism of coal pellet ejection and rock burst and the monitoring and early warning technology in the heading face at compound thick coal seams were studied using field investigation,theoretical analysis and on-site moni- toring methods. The results show that the soft coal part of the surrounding rock will quickly unload and destroy the coal particle ejection after the roadway is excavated,and the soft coal damage will cause local hard coal shear stress con- centration. When the degree of stress concentration exceeds the ultimate strength of hard coal,the shear failure of hard coal occurs,which in turn induces head-on rock burst. The on-site monitoring results show that there is no obvious sign of coal body stress and anchor cable pressure monitoring before and after rock burst in the heading face of compound thick coal seams. Acoustic emission monitoring can capture the information of rock burst,but many small energy vibra- tion events caused by frequent coal burst seriously affect the accuracy of the monitoring and early warning results. Therefore,this paper propose a monitoring and early warning method based on the concept of “high energy acoustic e- mission events”,that is,only the high-energy acoustic emission events that have a significant impact on the rock burst of the heading face are monitored. These acoustic emission events have the obvious feature that the total frequency of occurrence is relatively low,but the total energy is high. According to statistical analysis,the acoustic emission in the working face of (4-5)04 headgate with the energy greater than 1 000 mV is called the high energy acoustic emission events. Compared with the original early-warning methods,the early-warning methods based on the concept of “ high energy acoustic emission events” have a higher accuracy and more in line with the actual situation on site.

     

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