Abstract
Based on SOS microseismic (MS) monitoring system of a certain mine, time-, frequency-, and energy-domain characteristics of MS signals are analyzed by comprehensively applying one-dimensional discrete Fourier transform (DFT) and one-dimensional discrete wavelet transform (DWT). The technology is employed to explore MS signals from incident and transmitted waves on the fault plane. The research results show that, within the time domain, the transmitted waves are found to have the rapidly reducing velocity and a few wave crests; within the frequency domain, the fault plane presents a low-pass filtering effect on incident waves; within the energy domain, the fault generally shows the vibration-attenuating effect on MS signals. The analysis method is used for the No. 3307 working face of a certain mine to realize the prediction on a buried fault in the middle part of the working face, and it is validated to have a favorable effect.
Highlights
It is widely known that the analysis based on vibration signal is used for detection of mechanical and electrical faults of the motor, and the change of generated vibration signals can help detect the type of fault [3,4,5,6], which can provide a reference for the MS effect analysis in underground coal mining
Based on signal analysis theory, Cai et al [6] developed a series of software for postprocessing of MS signals. ese studies provide equipment and software bases for analyzing the time, frequency, and energy-domain characteristics of MS signals; they focus on exploring the timedependent law of MS signals. e frequency- and energydependent laws of MS signals are maturely applied in the geological exploration field, while their MS signal source generally needs to be actively activated
The wave files are required to be a continuous function in fast Fourier transform (FFT) method, while the measured MS data in underground coal mines are stored as a group of arrays with the fixed frequency. erefore, it is necessary to process the wave files by using the DDT [15]. e DDT delivers the same principle as the FFT method, while it realizes the data discretization. e DDT method is expressed as
Summary
Underground coal mines exhibit complex geological environment. e complex geological structures centered on faults influence the continuity of mine production, and probably trigger some dynamic disasters such as fault-induced rockburst, which greatly threatens the safety production of coal mines [1, 2]. e time-, frequency-, and energy-domain curves of a microseismic (MS) signal, as the concomitant signal during the deformation and fracture of coal-rock mass, can indirectly reflect the generation, propagation, and attenuation processes of the signal. Erefore, the existing SOS MS monitoring system and monitored MS data during mining of the working faces of mines were applied On this basis, the time-, frequency-, and energy-domain characteristics of MS signals from incident and transmitted waves within the fault zone were separately analyzed by comprehensively using multiple signal analysis methods. All data were taken from the SOS MS monitoring system of a certain coal mine in Shandong Province, China. e mined No 3 coal seam of
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