Crack coalescence between two non-parallel flaws in rock-like material under uniaxial compression

• The initiation stresses of primary crack in the two tips of each flaw are different for non-parallel flaws.
• The stress distribution between the non-parallel flaws is more complicated than that of the parallel flaws.
• The complicated stress distribution affects the stress for crack initiation and the pattern for coalescence.

Crack coalescence between parallel flaws has been extensively studied in brittle rock and rock-like materials. Due to the nature of rock masses that contain more than one joint set, the cracking process cannot be completely studied using specimens that contain parallel flaws. To address this area of research, crack coalescence between two non-parallel flaws is studied numerically using parallel bonded-particle models in which one flaw does not overlap or partially overlaps the other (varying α) and in which one flaw completely overlaps the other (varying β). Five types of linkage are observed between two flaws: tensile crack linkage, tensile crack linkage with shear coalescence at tip, shear crack linkage, mixed (tensile-shear crack) linkage and indirect crack linkage. The geometries of the two non-parallel flaws strongly influence the crack trajectories and coalescence patterns. At large angles of α (135°) and β (60°), coalescence occurs more easily by tensile crack(s) before the peak stress is reached. The stress distribution in bridge area of the non-parallel flaws is more complicated than that of the parallel flaws. This difference affects the stress for crack initiation as well as the pattern for coalescence.