Study on macro and micro damage mechanisms of layered rock under Brazilian splitting

Layered rocks were prepared to conduct Brazilian splitting tests with different laminar inclinations. Cracks on the surface are identified and quantitatively characterized based on digital images. The discrete element numerical software PFC3D was utilized to model the Brazilian splitting of laminated rocks with different inclinations. The effect of cohesion strength, tensile strength, and joint roughness coefficient (JRC) of smooth joints on tensile strength was investigated. The findings reveal that with increasing the inclination angle ( β ), the properties of the laminar surface gradually play a dominant role in the specimen damage, demonstrating that the peak load decreases continuously. The variation in the fractal dimension of the cracks primarily undergoes three stages: continuous increase, sharp decrease, and increase again. The tensile strength and failure patterns of the numerical simulations correlate well with the test. When β = 0°, the tensile strength of the specimen is independent of the joint properties; As β increases, the influence becomes apparent. Specifically, the tensile strength gradually increases with the increase in joint cohesion. Except when β = 90°, the tensile strength shows initially increasing and then leveling off with increasing the tensile strength of joints. Whereas, under the influence of the bedding plane roughness, it exhibits a continuous decrease at low inclination and an increase at high inclination with increasing JRC.