自震式微震监测技术及其在浅埋煤层动载矿压预测中的应用
Self-shocking microseismic monitoring technology and its application in prediction of dynamic pressure in shallow coal seam
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摘要: 震源定位是利用微震监测技术研究煤岩体破裂机制、分析矿震活动规律、预测煤岩动力灾害的基础。为了提高微震监测系统的定位精度,提出一种自震式微震监测技术,利用自激震源发射震动信号反演监测区域波速场,再将反演的波速场应用于微震定位计算。根据自震式微震监测技术研发出KJ768煤矿微震监测系统。在一定的拾振器网度和空间布置条件下,通过煤矿井下定点爆破和同类监测系统对比试验,测得KJ768微震监测系统的定位误差小于10 m。基于开发的KJ768煤矿微震监测系统开展浅埋煤层动载矿压预测,通过现场实测,研究微震监测结果和工作面矿压观测结果的关联关系,选定微震事件数和微震总能量作为周期来压和动载矿压的监测预警指标,并确定了预警阈值,准确预测了3次动载矿压和近20次周期来压,为防治异常矿压显现提供了借鉴。Abstract: Microseismic monitoring technology is widely used in the coal mine safety and coal-rock dynamic disasters prediction.Source location is the basis of application of microseismic monitoring technology to study the fracture mechanism of coal and rock mass, analyze the law of mine activity and forecast the coal and rock dynamic disasters.In order to improve the source location accuracy of the microseismic monitoring system, a self-shocking microseismic monitoring technique was proposed.In this technique, a self-excited source was used to transmit the vibration signals which were used to inverse the wave velocity field of the monitoring area, and the inversed wave velocity field was applied to calculate the location of the microseismic source. Based on this technology, a coal mine microseismic monitoring system named KJ768 was developed.Both the fixed point blasting underground and comparison test of similar monitoring system were adopted to monitor the positioning accuracy of the KJ768 microseismic monitoring system, and the results shown that under a certain detector net and space arrangement its positioning accuracy could reach less than 10 m.The developed KJ768 coal mine microseismic monitoring system was applied to predict dynamic mining pressures in shallow coal seam.After the experimental study on the relationship between the results of the microseismic monitoring andthe working face pressure observation, the numbers and total energy of microseismic events were selected as the period indexes of the cycle pressure and dynamic mining pressure, and the warning threshold were also determined. Finally, three times of dynamic mining pressure and nearly 20 times of cycle pressure were accurately predicted, which had provided a scientific basis and effective guidance for the prevention and control of abnormal mining pressures.