Uniaxial Compressive Damage Characteristics of Rock-like Materials with Prefabricated Conjugate Cracks

Joined fractures are an important factor affecting natural rock masses' mechanical and deformation properties. In this paper, indoor uniaxial compression experiments reproduce prefabricated cracks' generation, extension, and coalescence in rock-like specimens. For the fractured specimens, a single crack with an inclination of alpha = 45 degrees was placed on the left and right sides, and a third crack with an angle of beta = 30 degrees, 45 degrees, 60 degrees, and 90 degrees to the single crack on the right side was placed in groups III-VI, respectively. All cracks extended in the thickness direction. Vertical pressure was applied at a constant loading rate of v = 0.1 mm/min until the stress dropped dramatically. In addition, numerical calculations were performed on the rock specimens using PFC2D, a sub-module of the Discrete Element Method (DEM). The experimental results agree with the numerical simulations in that the strength of the specimens containing a conjugate crack is significantly reduced, and the mechanical and deformation properties of the specimens are related to the internal angle of the conjugate crack, with the lowest peak strength and lowest percentage energy dissipation at beta = 45 degrees.