Study on the influence of bursting liability on coal dynamic characteristics

The study of coal dynamic characteristics plays a key role in exploring the formation mechanism of rock burst during underground coal mining. In order to explore the impact of bursting liability on the coal dynamic characteristics, uniaxial cyclic loading and unloading tests and impact dynamics tests are carried out on three types of coal specimens. The test results show that there is a linear function relationship between the strain energy U_eⁿ and the corresponding input energy U_inⁿ of the three types of coal after cyclic loading and unloading test with variable stress upper limit. Meanwhile, the index of residual elastic energy C_EF of the above three types of coal is 25.35 kJ/m³, 30.34 kJ/m³ and 33.26 kJ/m³, respectively, indicating that the coal specimens of Tunbao Coal Mine and Yutian Coal Mine have strong bursting potential, while the coal specimens of Buertai Coal Mine have weak bursting potential. After SHPB test, the dynamic compressive strength of the corresponding coal increases by 1.32, 1.40 and 1.45 times, the dynamic elastic modulus increases by 1.21, 1.34 and 1.39 times, and the failure deformation increases by 1.34, 1.47 and 1.53 times, respectively. That is, with the increase of the index of residual elastic energy, the growth factor of coal dynamic parameters gradually increases, indicating that the larger the coal bursting liability is, the more the parameters related to the impact dynamics increase compared with the static state. With the increase of the bursting liability, the average equivalent diameter of the fragments after the coal collapse under dynamic load keeps decreasing, and the fractal dimension of the fragmentation keeps increasing, which indicates that the coal with large bursting liability is more complicated and broken after the impact load, and the dynamic response becomes more significant.