Abstract:

In order to explore the mechanism of rock burst induced by the instability of coal rock combinations under different dip angles, a particle discrete element program was used to conduct uniaxial compression tests on five sets of coal and rock combination models with different dip angles: 0, 15, 30, 45 and 60°. The research results indicate that coal is the main cause of instability and failure in coal-rock combinations. When the dip angle of the coal-rock combination increased from 0° to 30° and from 30° to 60°, the uniaxial compressive strength of the coal-rock combination decreased by 2.01% and 9.59%, and the number of microscopic cracks decreased by 22.9% and 4.0%, respectively. The appearance time of the acoustic emission signal is advanced, indicating that the increase in dip angle led to a decrease in the uniaxial compressive strength of the coal-rock combination, and the instability failure time is advanced, but the degree of failure is reduced. In the early stage of uniaxial loading, the movement of coal and rock particles at the interface of different dip angle combinations led to an expansion trend at the interface. The dip angle affected the movement of coal and rock particles near the interface, leading to a gradual transition of the failure area of the combination from the coal body to the coal-rock interface. When the cracks in the coal body extend to the coal-rock interface, the interface slip effect generated by the high dip angle coal-rock combination causes its failure mode to change from compression shear failure to slip failure, with a 30° dip angle as the boundary.

Key words: uniaxial compression, different dip angles, coal-rock combination, mechanical property, failure characteristics, crack propagation, numerical simulation