Acoustic emission characteristics and damage evolution of coal-rock under different confining pressures

Using PCI-2 acoustic emission(AE) system, the AE experiments of different confining pressures (0, 8, 16, 5 MPa) were carried out in Baijiao coal mine in Furong, Sichuan Province, in order to reveal the change rule of ringing count rate, the temporal and spatial distribution of AE, b value of AE and damage characteristics of damaged coal-rock under different confining pressures, and to provide a theoretical basis for prediction of coal-rock damage. The results show that the AE phenomenon can reflect the crack propagation of coal-rock and the confining pressure can restrain the damage of coal-rock. With the increase of confining pressure, the calmer period of ringing count rate was longer. The frequency range of ringing count rate is different under single and triaxial condition. In the uniaxial state, the AE registration points are uniformly distributed in the coal-rock, while in the triaxial state, they are centrally distributed in the failure section. With the increase of confining pressure, the fluctuation of pre-peak AE value b increases, and the change of value b can be used to predict the failure of coal-rock. Based on the cumulative ringing count and the failure stress of coal-rock, the damage failure model of coal-rock was established, and the precursor stress point of effective failure of coal-rock could be predicted by combining the AE ringing count rate, spatial and temporal distribution, value b and damage variables. The results will lay a foundation for the monitoring and analysis of coal-rock damage.