Influence of bedding anisotropy on the dynamic fracture behavior of layered phyllite

Layered phyllite, a typical anisotropic rock caused by the existence of beddings, is common in rock engineering. To evaluate the influence of beddings and loading rates on the dynamic fracture behavior of layered phyllite, notched semicircular bending (NSCB) specimens were measured using a split-Hopkinson pressure bar (SHPB) system. Static fracture testing using a servocontrolled material testing system was also conducted for comparison. The results of this study indicate that three typical fracture paths can be found for NSCB specimens under both static loading and dynamic loading. The fracture path evidently exhibits dependence on the loading rate. For specimens under static loading, dominated fractures are more likely to propagate along the bedding planes while the dominated fractures tend to ignore bedding planes as the loading velocity increases. Consequently, the fracture length ratio along the bedding plane is considerably lower under dynamic loading than under static loading. Anisotropic effects on static and dynamic fracture toughness are evident; however, the anisotropy of fracture toughness decreases as impact velocity increases. The results of this study confirm that a reduced fracture length ratio along the bedding plane induced by an increase in loading rate weakens the dependence of dynamic fracture toughness on anisotropy.