Failure characteristics of jointed rock-like material containing multi-joints under a compressive-shear test: Experimental and numerical analyses

Extensive efforts have been made to gain a better understanding of the failure behaviour of rocks and rock-like materials, but crack propagation and failure processes under compressive-shear loading have not yet been comprehensively investigated. To address this area of research, the peak shear strengths (τ) and failure processes of specimens with multiple joints are studied by lab testing and particle flow code (PFC2D). Four types of failure modes are observed: (a) shear failure through a plane (Mode-I), (b) intact shear failure (Mode-II), (c) oblique shear crack connection failure (Mode-III), and (d) stepped path failure (Mode-IV). The failure mode gradually transformed to Mode-III as α (joint inclination angle) increases from 0° to 90° in the specimens. In addition, with increasing joint distance (d) in the specimens, the failure mode changes to Mode-II. As the non-overlapping length between joints (c) in the specimens increases, the failure mode changes to Mode-IV. The joint geometry has a major influence on the shear strength of the jointed specimens. The peak shear strength of specimens with different joint inclination angles is obtained when α = 45°. Additionally, the peak shear strength increases as the joint distance (d) and non-overlapping length (c) increase.