Numerical experimental study on mechanical properties and deformation and failure characteristics of the dirt band rock mass

Based on the particle flow PFC2D numerical simulation software, the uniaxial loading numerical experimental models of the dirt band rock mass with different coal line layers, thicknesses and inclination angles were established. The influence mechanism of the number of coal line layers, coal line thickness, and coal line inclination on the mechanical properties and deformation failure of the dirt band rock mass, as well as the energy evolution characteristics during the deformation and failure process of the dirt band with different coal line inclination angles are studied in order to explore the mechanical properties and deformation and failure characteristics of the dirt band rock mass containing different coal lines. The research results show that when the proportion of coal is the same, the thickness of the coal line has a much greater effect on the dirt band than the number of coal line layers, and the change of the number of coal line layers has a greater impact on the elastic modulus and compressive strength of the dirt band while it has little effect on the failure form of the dirt band. It is easy for the change of coal line thickness to cause the change of the failure form; The elastic modulus and uniaxial compressive strength of the dirt band rock mass relative to the inclination of the coal line are approximately "U" Shape which means both show the inclination of first decreasing and then increasing with the inclination of the coal line increasing, but the two approximate minimum angles are different. The elastic modulus reaches the minimum at about 45°, while uniaxial compressive strength reaches the minimum when the inclination angle is about 60°; With the increase of the inclination of the coal line, the failure mode of the dirt band shows the evolution characteristics of rock main control fracturing failure-coal line main control slip failure-coal line main control fracturing failure. Energy evolution exhibits a certain inclination effect during the deformation and failure process of the dirt band. At each loading stage, the proportion of strain energy, cohesive energy, friction energy, and kinetic energy within the dirt band relative to the boundary energy increases with the coal line inclination angle increasing, which is approximately presents a "U" shape with the symmetry axis of 45°and relatively gentle slopes on both sides. © 2022, Editorial Board of Journal of Mining & Safety Engineering. All right reserved.