Dynamic mechanical behaviors and cracking mechanisms of non-straight flaws in tuff

The cracking mechanisms in rock containing non-straight flaws under dynamic loading remain poorly understood. To study the effect of flaw inclination on the mechanical properties and cracking mechanism in tuff with non-straight flaws under dynamic load, a dynamic compression test was carried out using a large-diameter split Hopkinson pressure bar device. Based on the uni-bond dual-parameter peridynamics model, a rate-dependent rock dynamic damage model was constructed. The paired-particle algorithm was combined with OpenMP parallelization to establish an efficient method for simulating the dynamic failure of flawed rock. The method was used to investigate the 3D crack propagation process and cracking mechanism in tuff specimens with non-straight flaws. The results show that with the increase in the flaw inclination angle, the dynamic strength, crack initiation stress, and the ratio of crack initiation stress to peak stress gradually decrease, and the failure mode of the specimen changes from shear failure to tensile-shear failure and then to conjugate shear failure. Cracks in rock specimens with non-straight flaws will not only initiate from the tip of a pre-existing flaw, but also from the convex point of the pre-existing flaw. The maximum crack propagation speed observed is 762∼1040 m/s, which is 0.35∼0.48 times the Rayleigh wave velocity. The displacement trend lines on both sides of the crack surface and the calculated normal and tangential displacement components enable discerning five cracking mechanisms. The research results reveal the cracking mechanisms in flawed rock masses and provide a theoretical basis for underground engineering projects.