Electromagnetic appearing characteristics of damage properties of coal under impact loading

The electromagnetic technology is an important means for predicting coal or rock dynamic disasters. The relationship between characteristic of electromagnetic signals and degree of damage is the premise of accurate prediction. Through coal SHPB experiments and transient electromagnetic monitoring, the characteristics of electromagnetic signals (0~3 kHz) of coal are analyzed in the process of rupture. The damage properties are analyzed from the degree of crushing and rupture energy. Then the relationship between the characteristics of electromagnetic signals (amplitude, energy) and the properties of coal damage is studied. The results show that the laws of fractal dimension and eventual rupture degree are similar. The fractal dimension can be used to quantitatively evaluate the extent of fracture specimens. The electromagnetic signals have transient pulse characteristics, and last only a few microseconds. The amplitude and energy of signals increase with the fragmentation degree. They exhibit a good linear relationship. The characteristics of electromagnetic signals can be used to monitor the damage degree of coal. Owing to the presence of the defects of inherent uncertainty coal materials and the resonance damage phenomenon, the correlation between damage degree and rupture energy is weak. The research results are important to the evaluation of the damage degree and to the prediction of dynamic disasters of coal or rock by use of the characteristics of electromagnetic signals.