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There are many nonpersistent joints in natural rock masses, and they play an important role in the mechanical and failure characteristics of rock masses. To investigate the shear failure behaviour of 3D nonpersistent jointed rock masses, laboratory tests and numerical simulations were conducted in this paper. The 3D nonpenetrating joints are created using a 3D printer, and five persistence ratios are considered. The experimental results show that the shear strength, cohesion and friction angle decrease with increasing joint persistence. A 3D DEM model containing 3D nonpersistent joints is established considering the joint persistence. The flat-joint model and smooth-joint model are used to model rock-like materials and prefabricated joints, respectively. The numerical results are consistent with the laboratory results in both shear strength parameters and failure characteristics. Combined with numerical results, the crack initiation, propagation and coalescence on 3D nonpersistent joint specimens were analysed at the microscale. [ABSTRACT FROM AUTHOR]

• Compressive-shear tests were conducted on transversely isotropic rock with different inclinations. • The micro-scale fracturing process of transversely isotropic rock with different inclination are analyzed. • The effects of bedding plane strength and spacing are analyzed. The failure and mechanical behavior of transversely isotropic rock are significantly affected by the original bedding planes. Until now, few studies have been performed to investigate the influence of the geometrical and mechanical parameters of the bedding planes on the fracture characteristics of transversely isotropic rocks under planar shear fracture loading conditions. For this purpose, experimental and numerical compression-shear tests on double-notched specimens are conducted to investigate the fracturing characteristics of transversely isotropic rock under planar shear fracture loading. The experimental study that focuses on the influence of bedding plane inclination on fracture load, fracture pattern and AE evolution, and six inclination angles is conducted in this study. Based on the flat joint contact model (for the rock matrix) and smooth joint contact model (for the original bedding plane) in PFC2D (particle flow code), the microscale fracturing process of transversely isotropic rock with different inclinations is simulated and analyzed. The results show that the inclination has an important influence on the fracture load and fracture pattern, and the maximum and minimum fracture loads are obtained for specimens with inclination angles of 30° and 60°, respectively. Moreover, the strength and spacing of the original bedding planes also play an important role in fracture loads. Higher bedding plane strength and wider bedding plane spacing result in higher fracture loads. In addition, with a moderate inclination angle, transversely isotropic rock with higher bedding plane strength tends to form cracks that cut through the rock matrix. However, with the decrease in the bedding plane strength, more fractures form along the bedding planes. [ABSTRACT FROM AUTHOR]

It is generally known that discontinuities have a remarkable influence on the mechanical behaviour of rock masses. To further understand the fracture mechanisms of jointed rock masses, substantial effort has been focused on the strength anisotropy and failure characteristics of rocks/rock-like specimens containing persistent joints with different geometric parameters. However, only a few laboratory tests have considered the failure mechanism of a rock mass with 3D joints, especially for non-persistent joints with different persistence levels. In the present work, experiments on cubic rock-like specimens containing non-persistent joints (in areal extent) subjected to uniaxial compression were conducted to further investigate the influence of the joint inclination (θ) and persistence (N) on the rock mechanical properties and failure characteristics. The strength of a 3D non-persistent jointed specimen is characterized by three stages as the joint inclination angle (θ) increases from 0° to 90°. The strength of jointed specimens decreases with increasing N for all θ values, with the highest strength obtained for N = 0.42 and the lowest strength recorded for N = 0.92. Based on CT scan results, four typical fracture modes were identified: splitting, splitting + sliding, sliding, and intact failure. Overall, as the joint inclination increases, the failure mode of the specimen transforms from splitting to sliding and then to the intact failure mode. However, with decreasing joint persistence, the failure modes of some specimens will change from sliding to mixed failure (splitting + sliding). • 3D printing technology was used to prepare cuboid rock-like specimens containing 3D non-persistent joints • The strength of the jointed specimen is characterized by three stages as the joint inclination angle (θ) increases. • The strength of the jointed specimen with the highest strength obtained for N = 0.42 and the lowest strength for N = 0.92. • Four typical fracture modes were identified: splitting, splitting + sliding, sliding, and intact failure. [ABSTRACT FROM AUTHOR]