Mechanistic study on the influence of bedding angles on impact susceptibility and crack evolution in coal samples

As a kind of rock mass with abnormal bedding development, the burst tendency of coal is deeply affected by bedding. In this paper, the mechanical properties, impact propensity, and damage modes of coal samples with different laminations under uniaxial loading are studied from the macroscopic point of view by combining indoor experiments and numerical simulation studies with the object of research of bedding development coal body, and the bedding effect of the microcracking evolution law of coal samples is revealed from the mesoscopic point of view. The results show the following: (1) The bedding angle has a significant effect on the uniaxial compression stress–strain curve of coal samples. Under the same experimental conditions, the dynamic failure time increases exponentially with the increase in the bedding angle. The impact energy index shows a trend of decreasing first and then increasing with the gradual increase in bedding angle. The uniaxial compressive strength decreases first and then increases with the increase in bedding angle. (2) The numerical simulation results show that after a 45° bedding angle, the degree of influence of the bedding plane on the coal sample intensifies. Before 45°, the crack of the coal sample is intersected or perpendicular to the bedding plane, and the influence of the bedding plane is small. After a 45° angle, the cracks are mainly bedding planes, and the cracks of coal samples at a 90° angle are basically coincident with the bedding plane, which is the most affected by bedding. When the bedding angle is 0°, the coal sample is mainly dominated by shear failure. When the bedding angle is greater than 45°, the main cracks are primarily bedding planes, accompanied by tensile and tensile-shear composite cracks. The results of this study can provide a reference for multi-level research on the mechanical properties and impact tendency of jointed rock bodies, which is conducive to improving the mechanism of impact ground pressure prevention and control.