Crack coalescence patterns and local strain behaviors near flaw tip for rock-like material containing two flaws subjecte
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ORIGINAL PAPER
Crack coalescence patterns and local strain behaviors near flaw tip for rock-like material containing two flaws subjected to biaxial compression Yanlin Zhao 1 & Jian Liao 1 & Yixian Wang 2 & Qiang Liu 1 & Hang Lin 3 & Le Chang 1 Received: 30 March 2020 / Accepted: 14 November 2020 # Saudi Society for Geosciences 2020
Abstract To understand crack coalescence patterns and local strain behaviors near flaw tip for flawed rock subjected to biaxial compression, a series of biaxial compression tests with a lateral stress of 2.0 MPa were carried out on rock-like specimens containing two flaws. The paper classified crack coalescence patterns, measured the local strain concentration near the flaw tip, and analyzed the stress–strain behavior related to crack initiation, propagation, and coalescence. Some interesting cracking behaviors of flawed specimens subjected to biaxial compression were observed. Seven basic crack types (wing crack, anti-wing crack, oblique and coplanar shear cracks, lateral crack, remote crack, and en echelon cracks) are identified and ten patterns of crack coalescences are observed subjected to biaxial compression. In general, the crack coalescence varies from the shear crack coalescence (S-mode) to the tensile wing crack coalescence (T-mode), and then to mixed shear/tensile crack coalescence (TS-mode), with the increase of the rock bridge ligament angle β, ranging from 25 to 120° subjected to biaxial compression. Crack initiation and coalescence usually can be reflected by a load stress rapid drop, a measured strain jump, or turning near flaw tip subjected to biaxial compression. The measured tensile or compression strains near flaw tip tend to increase almost simultaneously with higher axial stress before crack initiation; however, become very complex after crack initiation, due to the stress relaxation and adjustment near flaw tip induced by the combination of crack development and constant lateral stress. The existence of lateral stress results in many fragments in a shear failure mode with local surface spallings in flawed specimens containing two flaws. Keywords Crack propagation . Flawed specimen . Biaxial compression . Strain concentration
Introduction Crack coalescence refers to the linkage of pre-existing flaws in flawed material due to the initiation, propagation, and coalescence of new cracks and existing flaws. Due to rock material
containing natural fractures in different scales, a comprehensive understanding of the cracking processes initiating from exiting flaws subjected to various stress conditions can benefit geological engineering design and implementation, including rock slope stability analysis, tunnel support design, and fluid
Responsible Editor: Murat Karakus * Yanlin Zhao [email protected] Jian Liao [email protected]
Le Chang [email protected] 1
Hunan Provincial Key Laboratory of Safe Mining Techniques of Coal Mines, Work Safety Key Lab on Prevention and Control of Gas and Roof Disasters for Southern Coal Mines, Hunan University of Science and Technology, Xi
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