Based on electromagnetic radiation characteristics, the present research studied the damage evolution of rock under uniaxial compression. Besides, this research built the coal-rock damage evolution model considered residual strength. The applicability and accuracy of the model were verified through experiments. The results show that coal-rock damage evolution consists of four periods. The first period is from the beginning of compression to nearly 20% of the stress peak value, during which the damage variable changes stably about 0.1, and accordingly a few of electromagnetic radiation signals emerge. The second period is from about 20% to 70% of the stress peak value. The damage has stable development, and the parameter of electromagnetic radiation characteristics turns larger continuously with the increase of stress. The third period is when the damage has accelerated development, the coal-rock was broken which result from sharp increasing of the damage variable, meanwhile a great quantity of electromagnetic radiation signals emerge. The fourth period is after the coal-rock fracture, during which the damage variable corresponding to the parameter of electromagnetic radiation characteristics has a stable development. This research has great academic and realistic significance for further studies the electromagnetic radiation characteristics of coal-rock under loading and damage and the forecasting of coal-rock dynamic disasters.
Jin PeijianWang EnyuanLiu XiaofeiHuang NingWang Siheng
An experimental system for monitoring the acoustic signals generated in coal during gas sorption and/or desorption was designed and the acoustic signals were observed under different gas pressures. The experimental results show that signals generated by the coal during gas adsorption are attenuated over time. Also, the signals are not continuous but are impulsive. The intensity of the signals generated during gas desorption is far smaller than that observed during adsorption. The signal seen during desorption remains essentially stable. Cycles of sorption and desorption cause acoustic emission signals that exhibit a memory effect, which depends upon the maximum gas pressure the sample was exposed to in earlier cycles. Lower pressures in subsequent cycles, compared to the maximum adsorption pressure in previous cycles, cause both the energy and impulse frequency to be lower than previously. On the contrary, a gas adsorption pressure that exceeds the maximum pressure seen by the sample during earlier cycles causes both the energy and impulse frequency to be high.
Ma YankunWang EnyuanXiao DongLi ZhonghuiLiu JieGan Lijia
