The influence of stress path and flaw morphology on the failure mechanism and mechanical properties of rock masses

The macroscopic failure of rock masses is essentially the result of the propagation, interaction, and eventual coalescence of internal defects such as flaws under stress. Given the widespread presence of three-dimensional (3D) flaws in rock mass engineering, it is crucial to investigate their failure mechanisms and mechanical properties. This research employs a meso-damage numerical simulation method to systematically investigate the failure process and mechanical parameters of heterogeneous rock masses containing surface flaws, through-going flaws, and internal flaws under various stresses, focusing on the influence of stress path on flaw propagation behavior and the mechanical properties of the specimens. The study reveals: (1) Rock mass flaw propagation primarily manifests as the extension of wing and anti-wing flaws, and the coalescence of secondary flaws with these or with the pre-existing flaw. (2) Under uniaxial compression test, conventional triaxial and true triaxial compression test with specific intermediate principal stress directions, rock masses exhibit tensile coalescence failure, while changing the intermediate principal stress direction leads to transverse coalescence failure. The direction of the intermediate principal stress plays a decisive role in flaw propagation path. (3) Confining pressure significantly enhances the peak strength of the rock mass. For embedded and through-going flaws, the peak strength is generally higher when the intermediate principal stress direction is oriented towards the flaw plane compared to when it is parallel. Whereas the peak strength of surface flaws is not significantly affected by the intermediate principal stress direction. (4) The magnitude of the intermediate principal stress affects the mechanical properties of rock masses with different flaw types to varying degrees. The results of this study can provide valuable references for theoretical research and physical experiments on the propagation mechanisms of 3D flaws in rock masses.