Experimental Study on Stress Evolution and Microseismic Signals under Vibration Conditions of Coal during Excavation and Subsequent Waiting Time

Qifei Wang,Dihao Ai,Chengwu Li,Yuechao Zhao,Pingyang Lyu,Beijing Xie

doi:10.1155/2019/3235984

Abstract

An experiment designed to simulate coal during excavation was conducted. Microseismic signals of coal under vibration conditions during excavation and subsequent waiting time of the coal roadway at different excavation speeds were collected and analyzed. During the excavation and subsequent waiting time, the stress in coal is redistributed, and the concentrated stress is gradually transferred to the deeper section of the coal seam. The Hilbert–Huang transform (HHT) is used to effectively denoise the collected signals. According to the noise-reduced signal, the amplitude and pulse number of the microseismic signals emitted during the excavation process are much larger than those of the waiting time process. During excavation, the energy and event numbers of microseismic signals increase first and then decrease as the excavation speed increases. The faster the excavation speed, the more the energy, and the higher the event numbers of the microseismic signals released during the subsequent waiting time. When the excavation speed is faster, more elastic potential accumulates in the coal seam and the concentration stress is greater. As the concentrated stress moves forward in time without excavation, more coal seams fail, and more microseismic signals are released. The microseismic signal and the stress evolution law can provide a reasonable explanation for the forward movement of the concentrated stress and coal failure during roadway excavation.

Highlights

In underground mine mining, rock and coal are subjected to tremendous overlying strata pressure and tectonic stress.e original stress balance state of the mine is disrupted during the mining operation, which may trigger the transfer of stress and the concentration of local stress. is process is often accompanied by the rupture of coal, which can cause release of microseismic and acoustic emission signals. e main causes of microseismic events are slip and dislocation of existing cracks in mines under the action of tectonic and mining stress [1]
E original stress balance state of the mine is disrupted during the mining operation, which may trigger the transfer of stress and the concentration of local stress. is process is often accompanied by the rupture of coal, which can cause release of microseismic and acoustic emission signals. e main causes of microseismic events are slip and dislocation of existing cracks in mines under the action of tectonic and mining stress [1]
Stress Change during the Excavation and Waiting Time. e test chamber is a steel cylindrical tank, and the tank provides stress to the inner coal seam based on the reaction of the expansion agent. e stress at each tank position represents the stress state of the coal seam at that position. e reserved tunneling holes must be opened before the tunneling process is simulated

Summary

Introduction

Rock and coal are subjected to tremendous overlying strata pressure and tectonic stress.e original stress balance state of the mine is disrupted during the mining operation, which may trigger the transfer of stress and the concentration of local stress. is process is often accompanied by the rupture of coal, which can cause release of microseismic and acoustic emission signals. e main causes of microseismic events are slip and dislocation of existing cracks in mines under the action of tectonic and mining stress [1]. Rock and coal are subjected to tremendous overlying strata pressure and tectonic stress. Is process is often accompanied by the rupture of coal, which can cause release of microseismic and acoustic emission signals. Real-time monitoring of coal-rock microseismic signals has become an important means to predict coal-rock dynamic disasters in underground mining [2]. Since the 1970s, the United States has used microseismic monitoring in mines to ensure the safety of underground personnel and developed supporting software and hardware for this purpose [7]. As the technology has matured, the microseismic technique has become the fundamental monitoring approach for mine safety and ground control. Mansurov demonstrated that the microseismic signal is a highly efficient and accurate predictor of strong impact ground pressure [9].

Results

Discussion

Conclusion