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首先对声发射信号进行分频处理,分析岩石损伤破裂演化过程中声发射信号频段分布规律。根据岩石断裂模式与声发射频率存在一定的对应关系,证明了岩石破裂监测中声发射前兆优势频段的存在,进一步构建前兆优势频段的计算方法,确定声发射监测岩石破裂的最优短临预报参数。通过开展花岗岩圆形隧洞模型水平卸荷试验,分析整个过程的声发射信号,寻找前兆优势频段,以此验证方法的可靠性。研究结果表明,水平方向卸荷瞬间,隧洞两壁发生劈裂破坏,频段(31.25~62 k Hz)的小波能量占比达73%以上。临近最终破裂,频段(7.8125~15.625 k Hz)变能系数CD6?由前一刻的0.5突增到15,具有典型的灾变响应特征,可以确定该频段为声发射前兆优势频段。选择CD6??作为宏观破裂的短临预报参数,再结合临近最终破裂前声发射主频在频段(90~105 k Hz)和(13~20 k Hz)所出现的响应突现规律,可以为预测花岗岩圆形隧洞模型的失稳破坏提供预警参量。
Firstly, the acoustic emission signal is frequency-divided to analyze the frequency distribution of acoustic emission signal in the process of rock damage and rupture evolution. According to the relationship between rock fracture mode and acoustic emission frequency, the existence of preponderance acoustic emission precursors in rock burst monitoring is proved, and the calculation method of preponderance predominant frequency bands is further established to determine the optimal short-term prediction parameters of acoustic emission monitoring rock fracture . Through the horizontal unloading test of the granite circular tunnel model, the acoustic emission signals of the whole process are analyzed and the preponderance frequency band is searched to verify the reliability of the method. The results show that splitting failure occurs on the two walls of the tunnel at the moment of unloading in the horizontal direction, and the energy of the wavelet in the frequency band (31.25-62 k Hz) accounts for more than 73%. Near the final rupture, the energy coefficient CD6? Of the frequency band (7.8125-15.625 k Hz) suddenly increases from 0.5 to 15 at the previous moment, and has the typical catastrophic response characteristics. It can be determined that this frequency band is the predominant frequency band of acoustic emission precursors. Choosing CD6 as the short-term and long-term prediction parameter of macroscopic rupture, combined with the emergent law of the response frequency of acoustic emission in the frequency band (90 ~ 105 k Hz) and (13 ~ 20 k Hz) before the final rupture, The failure parameters of granite circular tunnel model provide early warning parameters.