Shandong University of Science and Technology,Qingdao,Shandong
The coal body of coal mining face is often under the combined stress environment of static load and dynamic load impact, and its mechanical response and energy evolution characteristics are closely related to the occurrence of coal mine dynamic disasters. For this reason, the split Hopkinson pressure bar (SHPB) experimental system was used to carry out the impact test of coal under the combined dynamic and static loads, and the mechanical properties and energy evolution laws of coal under different dynamic and static load combinations were analyzed. The results show that: 1) The dynamic strength of coal body has obvious axial compression and strain rate effects. With the increase of the former, it first increases and then decreases, but it is in direct proportion to the latter; 2) Under static and dynamic combined loading, the macroscopic failure mode of coal mass has two types: tensile shear failure and "explosive" crushing failure, and the axial pressure controls the transformation of the macroscopic failure of coal mass from the former to the latter; 3) Dissipated energy of coal can quantitatively characterize the degree of coal fragmentation under combined dynamic and static loading. Fractal dimension of coal fragmentation and dissipated energy show a weak power function growth relationship. This study can provide support for revealing the dynamic instability mechanism of deep coal and rock mass.