Fracture Mechanical Properties of Double-Edge Cracked Flattened Brazilian Disc Samples Under Compressive Loads

The shear-based fracturing of deep fractured rocks under compression-shear loading is one of the most prevalent failure modes due to the existence of in situ stress. In order to study the shear fracture mechanical properties of fractured rocks, a double-edge cracked flattened Brazilian disc (DCFBD) sample was developed by introducing two platforms into a double-edge cracked Brazilian disc (DCBD). Extensive finite element analyses were conducted on DCFBD samples to determine the stress intensity factors (SIFs) and T-stress. A comprehensive dataset of SIFs and T-stress was obtained, which provided accurate descriptions of the compression-shear fracture tests performed on this specimen. Furthermore, the effects of the load distribution angle γ, dimensionless crack length α, and crack inclination angle θ on dimensionless SIFs Y_I, Y_II, and T-stress T* were discussed. It showed that the effect of load distribution angle γ on the dimensionless SIFs Y_I and Y_II can be disregarded when the dimensionless crack length α ≥ 0.60 and load distribution angle γ ≤ 20°. However, it should be considered for the T-stress for larger crack inclination angles. Moreover, it was experimentally validated that the DCFBD samples with appropriate crack lengths and load distribution angles can achieve shear (true mode II) fracture, as demonstrated through a series of fracture tests conducted on these specimens. The results will advance the development of rock shear fracture testing technology.