Effect of oblique incident wave perturbation on rock spalling: An insight from DEM modelling

In order to study spalling failure characteristics of rock under oblique incidence of stress wave, a split Hopkinson pressure bar (SHPB) spalling test with a special shaped striker was simulated by Particle Flow Code (PFC). The oblique section angles selected in this study were 30°, 45° and 60°, respectively. The spalling failure characteristics of rock with oblique incidence of stress waves at 5.2 m/s, 5.6 m/s and 6.2 m/s impact levels were analyzed and compared with those for 90° section incidence. The results show that when the angle of the oblique section greater than 45°, the stress wave will be directly reflected into a tensile wave when it encounters the oblique section, and then the reflected tensile waves and compressive waves will alternately appear. When the angle of the oblique section is less than 45°, the reflected stress wave is superimposed multiple times with the incident stress wave in the oblique section, and induces the spalling of the oblique section. Based on the longitudinal wave propagation theory, the function of stress in the 30° oblique section has been derived. The possible fracture position of the oblique section is obtained, which is consistent with the simulation results.