Interaction between flaws and failure characteristics of red sandstone containing double flaws under compressive-shear loading

•The effect of flaw configuration on crack coalescence and failure behavior under compressive-shear loading was studied.•Two parameters, i.e., independent parameter and reinforced parameter, were proposed to characterize the interaction between flaws.•The macro-and microscopic failure features of specimens were characterized.•Three typical crack coalescent modes were determined for specimens with two flaws. The failure characteristics of the fractured rock mass and the interaction between flaws were significantly affected by the flaw configurations. This study quantitatively investigated the effect of flaw geometries on the interaction between flaws under compressive-shear loading. The evolution of the surface strain field was recorded and analyzed using digital image correlation (DIC) technology, enabling the localization of crack paths and the determination of crack initiation mechanisms. Combined with DIC and scanning electron microscopy, both the macroscopic and microscopic failure characteristics of specimens with double flaws subjected to compressive-shear loading were comprehensively investigated. The results showed that the axial peak force of flawed specimen was sensitive to the flaw configuration, and the axial peak forces of flawed specimens with parallel flaws were greater than those with coplanar ones. The tensile strain was the primary factor dominating the initiation and propagation of cracks from flaw tips, whereas the cracking mechanism of edge cracks was a combination of tensile and shear strains. In addition, two novel parameters, namely independent parameter Ri and reinforced parameter Rr, were proposed to quantitatively characterize the independent effect discovered between coplanar flaws and the reinforced effect between parallel flaws, respectively. Besides, it was observed that the flaw configuration has a significant effect on rock failure characteristics, and three typical crack coalescent modes were found. The findings of this paper could facilitate a better understanding of the interaction between flaws and rock failure characteristics subjected to compressive-shear loading conditions.