Energy evolution and damage characteristics of coal with different bursting liability under uniaxial compression

In order to study the energy evolution law and damage characteristics of coal with different bursting liability under uniaxial compression based on the laboratory bursting liability and other mechanical parameter tests, the mechanical parameters of the PFC models are calibrated so that the PFC models truly reflect the macro-mechanical properties of coal samples. The energy evolution law and damage characteristics of coal with different bursting tendency under uniaxial compression tests were simulated and analyzed. The results show that the energy evolution laws of different bursting liability coals are similar. Before the peak stress, the boundary work was mainly converted into strain energy, and the proportions of dissipation energy, sliding energy, and kinetic energy were very small. After the peak stress, the strain energy was quickly released. The dissipative energy, sliding energy and kinetic energy began to increase rapidly. With the increase of bursting tendency, the rate of strain energy release and kinetic energy significantly increases. Two indexes of strain energy release rate and kinetic energy growth rate are proposed.It was found that the strain energy release ratio and kinetic energy growth ratio have a good correlation with the uniaxial compressive strength, bursting energy index and elastic energy index. This index can be used to assist in evaluating the coal sample bursting tendency. The evolution of micro-cracks in coal samples with different bursting liability before peak strength is similar,and the micro-cracks grow rapidly after the peak intensity point, and the growth rate is positively correlated with the bursting liability. Based on the method of determining crack initiation and volume strain curve, it is concluded that the cracking initiation stress levels of coal are mainly distributed between 44.18% and 51.67%,and the damage stress level is between 89.04% and 93.86%.The initiation stress level and damage stress levelof the coal samples with strong bursting liability are higher than those of the weak and non-bursting liability coal samples. The initiation stress level and damage stress level reflects the ability of strong bursting liability coal samples to accumulate high elastic strain energy and produce brittle impact failure.