Simulated Research on Dynamic Mechanical Properties and Crack Evolution Laws of Fractured Red Sandstone

Using the two-dimensional Particle Flow Code (PFC2D), a model of red sandstone containing fractures with different inclination angles under impact load was established to study the influence of fracture inclination angles on the dynamic compressive strength, stress wave attenuation, and crack evolution laws of the model. The results indicate that, under the same impact load, the dynamic compressive strength of the cracked specimens exhibits a “V”-shaped variation, with the specimen at a 45° inclination angle showing the lowest strength. The influence of inclination angles on strength is most significant in the 30° to 45° inclined specimens. As the inclination angle increases, the reflection coefficient rises, the transmission coefficient decreases, stress wave attenuation intensifies, and the time for specimen penetration shortens, making the specimen more prone to failure. The location of crack initiation shifts toward the middle of the fracture as the inclination angle increases, and the cracks tend to develop parallel to the impact load. When the inclination angle is ≥45°, stress concentration at fracture tips prolongs the shear-dominated phase during failure progression. However, the tensile ratio k consistently exceeds 0.7 at ultimate failure, indicating tensile mechanisms remain the dominant failure mode. Both absorbed energy and total crack number generally decrease with increasing inclination angle, while no clear correlation exists between absorbed energy and fragment number. Large fragments are distributed on both sides of the fracture during the fragmentation process. In contrast, small fragments concentrate near the through cracks. Specimens with 45° and 60° inclination angles exhibit a higher number of fragments and more significant fragmentation. In the initial loading stage, the specimen with a 90° inclination angle shows the weakest resistance to failure, while the 0° inclination angle specimen exhibits the strongest resistance. The research findings contribute to elucidating the dynamic failure mechanisms of fractured red sandstone, analyzing slope stability, and optimizing blasting designs.