Investigating dynamic mixed-mode I/II fracture behavior of sandstone using the modified generalized maximum tangential stress criterion

Dynamic mixed-mode I/II crack growth under various engineering disturbances can result in rock failure and even catastrophic events. Nevertheless, the dynamic cracking behavior of rock and fracture criterion for mixed-mode I/II remain poorly understood. Cracked straight-through Brazilian disc tests were performed on sandstone specimens to examine the effects of strain rate ( ) and loading angle ( β ) on the dynamic fracture behavior of mixed-mode I/II using a split Hopkinson pressure bar system. The generalized maximum tangential stress (GMTS) criterion was modified by considering the influence of β and crack propagation velocity (CPV) to estimate the dynamic fracture parameters. The results indicate that the CPV increases with increasing , while remaining nearly independent of β . β and strongly affect the dynamic mixed-mode fracturing process. The crack initiation angle changes slightly with increasing , and it first increases and then stabilizes as β increases. When β exceeds 60° and is lower than approximately 10 2 s -1 , the crack initiation location transitions from the crack tip to the centre region of the crack. When is greater than approximately 10 2 s -1 , the non-tip cracking disappears gradually. The dynamic failure characteristics of specimens can be divided into four main types, which occur successively with increasing β and . Additionally, the dynamic stress intensity factors and crack initiation angles predicted by the modified GMTS criterion are generally consistent with the experimental results for different CPVs. This study provides valuable insights into the detailed dynamic mixed-mode cracking behavior and fracture criterion of rock.