New crack initiation model for open-flawed rock masses under compression–shear stress. (December 2021)

• Record Type: Journal Article
• Authors: Yang, Chao; Tang, Jitao; Huang, Da; Wang, Lehua; Sun, Qiancheng; Hu, Zhangxin
• Is Part Of: Theoretical and applied fracture mechanics. Volume 116(2021)
• Publication Date: 2021-12
• Subjects: Crack initiation model -- Open-flawed rock mass -- Compression–shear stress -- Uniaxial compress test; Fracture mechanics -- Periodicals; 620.1126
• DOI: 10.1016/j.tafmec.2021.103114
• Languages: English
• ISSNs: 0167-8442

Abstract

Highlights: A new crack initiation model was proposed considering the interaction of τ and σ y . The σ y was considered in crack initiation analysis of open fractured specimens. The crack initiation stress of middle crack is close to that of tip crack. Abstract: Many tests and numerical calculation results have demonstrated that the relationship between the strength of a rock mass with an open single-flaw and the flaw angle ( β )is not a symmetrical U-shaped distribution at β = 45°, as calculated using the slide crack model. In this study, based on a comparison between previous tests by other investigators and the slide crack model, uniaxial compression tests were conducted on sandstone specimens containing a single flaw. The peak strength ( σ c ), initiation stress ( σ ci ), crack initiation, and failure of the specimens were analyzed in detail. In contrast to the sliding crack model, in which cracks in all the specimens initiate in the form of wing cracks, two other modes of crack initiation were observed for specimens with β = 0°–40°: the anti-wing and middle cracks. The results indicated that the compressive stress ( σy ) on the flaw surface contributes significantly to the crack initiation process. Therefore, a crack initiation criterion is proposed: when the sum of the I-type stress intensity factor ( K I ) generated by the shear stress ( τ ) and σy attains the fracture toughness ( K IC ), cracks will initiate from the tip of the pre-existing flaw (when σy > τ, crack initiation is in the form of an anti-wing crack, otherwise it is a wing crack). When the tensile stress ( σt ) on the flaw surface reaches the tensile strength of the rock before K I at the crack tip reaches K IC, cracks in the specimen will initiate in the form of middle cracks.