Research Of Theory And Application Of Microseismic Monitoring Technology On Large Complex Gob Stability

Due to years of mining and other historical reasons, a lot of mines left untreated large complex gob. Monitoring and early warning the stability of large complex gob is the focus in safe production of mines. Microseismic monitoring technology increasingly shows its large superiority in stability monitoring of large complex gob. Based on the research of microseismic monitoring technology on large complex gob in Shizhuyuan polymetallic ore and Xianglushan tungsten ore, this article studies focal mechanism of the fracture of large volume rock mass, underground microseismic signals recognition and early warning of unstability of rock mass. The main contents and results are as follows:⑴This article uses the waveform of microseismic events to understand the mechanism of the fracture of large volume rock mass. According to the P wave first motion displacement radiation pattern generated during large-scale ore pillar fractued, we can calculate the attitude and slide angle of plane of fracture, and then get the moment tensor expression and failure mode of the large-scale ore pillar; seismic moment calculated based on microseismic events is compared with the seismic moment calculated based on measured fracture surface parameters, the release rate of seismic moment indicates that the large-scale pillar had been stable.⑵Artificial recognition based on the signal waveform characteristics achieves identification on most of singals; further discrete Fourier transform recognition based on signal frequency characteristics obtains good recognition results, then the original waveform is filtered by inverse Fourier transform. When signals are difficult to identify by artificial recognition and have high frequency range overlapping, the wavelet transform recognition which studies signal's time-frequency characteristics obtains good recognition results, wavelet theory in the underground microseismic signals recognition has tremendous potential.⑶This article studies the gray forecasting and correlation dimension of microseismic event rate time series before the rock mass becoming unstable. The main conclusions are as follows: First, the accuracy of gray prediction value is good at ordinary times, but when the microseismic event rate increasing suddenly the prediction value will be much less than the measured value; Second, the rapidly decreasing of correlation dimension values more occurs in the time of microseismic events rate increasing suddenly. Early warning should be released when the correlation dimension value downing quickly first, and the unstable of rock mass more occurs in the second time or above of correlation dimension value decreasing rapidly. At last we summarize the different quantitative criteria of early warning by experience based on microseismic event rate in above two mines.