Tensile behavior of Brazilian disks containing non-persistent joint sets subjected to diametral loading: experimental and numerical investigations

Structural defects are part of the inherent characteristics of rock masses. They can be found in fishers, joints, and beddings and can be divided into persistent or non-persistent ones. The coalescence of non-persistent cracks may lead to the formation of persistent joints under the tensile stress field, leading to rock mass instability. The mechanical behavior of non-persistent jointed disks under tensile stress has important implications for rock structures. In this paper, experimental and Discrete Element Method (DEM) numerical simulation approaches were adopted to investigate the effect of joint continuity factor (the relationship between joint length and rock bridge length), bridge angle, joint spacing, and loading direction in relation to joint angle on the tensile strength and stiffness as well as failure pattern. Cement-mortar-based Brazilian disks containing open non-persistent joints were constructed and subjected to diametral loading and simulated using a two-dimensional Particle Flow Code (PFC2D). The investigations revealed that the tensile strength, stiffness, and failure pattern of Brazilian disks are highly affected by non-persistent pre-existing cracks. The increase of joint continuity factor and loading direction leads to the reduction of both tensile strength and stiffness. However, when spacing increases, tensile strength and stiffens have a minimum at the average spacing, but it was concluded that bridge angle does not affect both parameters. Finally, the results showed that the experimental and numerical approaches are in good agreement, and almost all the parameters affect the failure pattern, and some failure patterns such as step-path failure, splitting, or sliding may occur as a function of non-persistent joint sets.