COAL WORKING FACE IMAGING BY SEISMIC INTERFEROMETRY - USING CONVEYER BELT NOISE AS SOURCE

The real-time monitoring of stress conditions around the working faces of coal mines has been found to be an effective method to prevent geological disasters, such as roof collapses and water bursts. In this research study, a seismic interferometry method was proposed based on conveyor belt noise, for the purpose of implementing working face real-time imaging. In order to examine the seismic interferometry induced by conveyor belt noise, a stationary phase integration analysis of the cross-correlation of the thread seismic source was first conducted. Then, a numerical simulation of the discrete linear array noise traces was discussed. The analysis showed that the seismic interferometry of the thread seismic sources produced some fake events, which were observed prior to the true events. Therefore, the arrival-time of true events could be picked up by using a simple cross-correlation. The results of this study's field data suggested that the conveyor belt noise was a wide band signal. At the same time, it was also found to have an intense time structure. The Green's function, which was retrieved using deconvolution interferometry, displayed a higher time resolution than those obtained by the cross-correlation. Finally, this study's field data illustrated that the conveyor belt noise could be potentially applied to monitor the stress variations around longwall mining panels. As a result, the proposed method was expected to be an effective method for the reduction of coal mine disasters.