采动效应微震特征及其变化规律

依据采动应力是煤与瓦斯突出的外在动力,构建煤巷采动微震监测系统,分析煤壁崩落过程及其诱因,研究顶板、煤壁破裂微震动态响应特征,了解采动应力显现、调整变化规律。优选小波基函数,按照频率顺序将半小时内396次采动效应触发的微震事件进行小波包4层分解、重构;根据采动顺序和信号优势频带,将采动微震响应信号划分为爆破、煤壁崩落、顶板和煤壁破裂4类信号,采用归一化频带能量分析顶板、煤壁破裂事件的变化趋势。爆破冲击和顶板压力导致煤壁崩落,顶板压力还会导致煤壁破裂,顶板和煤壁破裂是煤巷采动应力的具体显现。顶板压力初期显现剧烈,爆破结束1.6 s内煤壁发生5次崩落,1.933 s时达到峰值、24.89 min趋于稳定;顶板破裂事件主要集中在初期2 min内,相应的事件率为76.2%。煤壁压力滞后顶板压力5.8 s后显现,3.71 min后达到峰值、29.217 min稳定;煤壁破裂事件主要集中在初期5 min内,相应的事件率为45.9%。顶板、煤壁破裂事件及其优势频带能量变化趋势揭示采动应力转移、调整过程,采动效应稳定与否可用于煤与瓦斯突出预警,并值得进一步深入研究。

MICRO-SEISMIC CHARACTERISTICS AND ITS CHANGE LAWS RESPONDED BY MINING EFFECTS

According to the theory that the mining stress is the extrinsic impetus for coal and gas outburst，the micro-seismic monitoring system has been constructed to respond to the activities on the coal roadway mining. The process and its main causes of coal caving were analyzed，the characteristics responded by micro-seismic activities on the coal and its roof ruptures were studied. The monitoring system which is combined by sensors with three different levels of sensitivity is aimed to acquaint entirely the change law of mining stress emergence and development. Based on the selection of Wavelet basic function，the total signals which number is 396 activated by mining effects within half an hour were decomposed and reconstructed on the method of Wavelet packet into 4 layers based on the frequency sequence. The micro-seismic signals activated by mining were divided into four categories such as blasting，coal caving，roof and coal wall ruptures signals according to mining sequence and frequency band，and the change tendency of roof and coal wall ruptures events was analyzed on the normalized frequency energy. Coal caving and roof ruptures are caused by blasts；the roof pressure can lead to coal wall ruptures as well. Roof ruptures as well as coal wall ruptures represent the mining stress definitely. Roof pressure in the early stage responds tempestuously，which causes five sections of coal caving within 1.6 seconds after blasting，reached the peak after 1.933 seconds and stabilizes 24.89 minutes later；roof ruptures events are mainly concentrated in the early 2 minutes and its corresponding events rate is 76.2%. Comparatively，coal wall ruptures react with delay of 5.8 seconds relatively to roof pressure，reach the peak after 3.71 minutes and stabilizes 29.217 minutes later；coal wall ruptures events are mainly concentrated on the early 5 minutes and its corresponding events rate is 45.9%. Roof and coal wall ruptures events and the change tendency of its own normalized energy on the dominant frequency band disclose the process of transformation and adjustment of mining stress，and the result that the coal body itself can get stable or not responded by the mining effect can be used to predict and early warn the coal and gas outburst，which needs further thorough research.