Study On The Acoustic Electric Response Rules Of The Fault In The Front Of The Tunneling Work

Abnormal geological structures including faults in front of driving working faces often cause unexpected events such as coal and gas outburst, water inrush and so on, which affect the production of coal mine and lives of miner seriously. Coal or rock would generate acoustic emission(AE) and electromagnetic radiation(EMR) during the course of loading and cracking. The stress and mechanical properties of coal and rock will change in the area of geological structures, which would affect the Acoustic emission and electromagnetic radiation. Therefore, it is of great significance to the safety of coal mine to monitor and analyze the change and its rules of AE and EMR during roadway excavation and to identify the geological structures in front of the working face.The stress distribution in the front of driving working face was simulated through FLAC3 D. The influence scope and laws of fault on the stress was analyzed. The AE and EMR of pre-cracked coal or rock Samples were tested during the course of deformation and fracture by using the experimental system for acoustoelectric effect of pre-cracked coal or rock samples during deformation and fracture. The influence laws of pre-crack on AE and EMR were analyzed during deformation and fracture. The change rules and spectrum characteristics of AE and EMR were tested and analyzed during the course of tunneling face going through the fault. The results of the study are as follows:(1)In the surrounding rock of roadway, the vertical stress in the front of tunneling working face is biggest, and the strike stress smallest. The influence of fault on the distribution of vertical stress is most obvious, and the range is also the largest.(2)The influence of pre-crack on AE and EMR in the process of deformation and failure of coal and rock samples is different. The influence of the pre-cracks on the AE is greater than that of the EMR because of the differences of the structures of coal and rock and generation mechanism of AE and EMR. The compressive strength of coal or rock samples with different crack angle is different. In the course of deformation and failure of coal and rock samples, the sensitivity of EMR to stress is higher than that of AE.(3)The variation laws of the intensity of AE and EMR during the process of driving face going through the fault has obvious stage. The laws of change are mainly: step upward trend when closing the fault and step downward trend when away from the fault. The wave of AE and EMR is increased during the process of going through the fault(4)During the process of going through the fault, the frequency of AE and EMR has frequency shift phenomenon, and the amplitude would increase first and then decrease. When the working face is close to and far away from the fault, the main frequency of the AE and EMR is larger, the signal distribution is more dispersed, and the amplitude of the waveform is relatively small. When going through the fault, the main frequency of the AE and EMR is small, the signal distribution is more concentrated, and the amplitude of the waveform is relatively larger.