Abstract
Using discrete element software, namely, particle flow code as two‐dimensional program (PFC2D), two types of models were established: vertical fissure hole combination and horizontal fissure hole combination with ratios of major and minor axis of ellipse being 1, 1.2, 1.5, 2, and 3, which corresponded to a total of ten samples. The failure mode, mechanical behavior, and stress state before and after crack generation in elliptical hole crack combination models with different ratios of major and minor axis were analyzed. The crack development, stress field evolution, and acoustic emission characteristics of the vertical fissure model and horizontal fissure model were studied at the optimized ratio of major and minor axis of ellipse being 1.5. The results showed that elliptical hole fissure with different ratios of major and minor axis resulted in the decrease in the strength and elastic modulus of rock and increase in the peak strain of rock. The effect of the horizontal fissure model on the peak strength, peak strain, and elastic modulus of rock was found to be greater than that of the vertical fissure hole model. Ellipses with different ratios of major and minor axis in various models slightly influenced the rock failure modes, and their failure modes corresponded to tensile shear failure and tensile failure. Before crack formation, the tensile stress concentration areas of each model were, respectively, distributed at the upper and lower ends of the vertical fissure and the major axis of ellipse, and the compressive stress concentration areas were distributed at both ends of the major axis of ellipse and the fissure in the horizontal direction. After the model failed, the compressive stress concentration areas of the vertical fissure model and the horizontal fissure model transferred to the left upper part and the right upper part of the model along the left end of the hole and the right end of the fissure, respectively. When the ratio of major and minor axis of ellipse was 1.5, cracks in the vertical model and the horizontal model of fissure developed along the axial direction at the ends of cracks and holes, respectively, and then secondary cracks were generated at the ends of left and right sides. The maximum compressive stress in each stage of the vertical fissure model was greater than that of the horizontal fissure model, and when the model was damaged, its stress release was more.
Highlights
Wong et al [13] conducted a series of uniaxial compression physical and numerical tests on single-hole samples with different diameters and sample widths and further studied the splitting failure, failure mode, and strength characteristics of samples caused by crack propagation
Huang et al [14] carried out uniaxial compression test and numerical simulation study on granite samples containing three noncoplanar holes; analyzed the relationship between stress, acoustic emission (AE), and crack propagation process via AE measurement and image monitoring technology; and determined four typical crack coalescence modes
For the comprehensive understanding of the strength and failure behavior of rock materials with fissure holes, this study investigated the deformation characteristics, force chain distribution, and stress field evolution of rocks with the combination of vertical fissure ellipse and horizontal fissure ellipse by changing the ratio of major and minor axis of ellipse
Summary
Numerous defects such as cracks, holes, and weak structural planes are present in natural rock mass. e existence of these defects significantly influences the structural characteristics and mechanical properties of rock, and the instability and failure of rock engineering are closely related to the crack initiation and extension characteristics of fissure and holes in rock [1,2,3,4,5,6]. erefore, in-depth study on the failure characteristics and mechanical properties of defective rocks is of great significance for the comprehensive understanding of the stability and safety of rock engineering. To analyze the fracture coalescence behavior of rock, Yang et al [11] conducted uniaxial compression test on Advances in Materials Science and Engineering rectangular prismatic sandstone specimens containing three fissures; studied the influence of ligament angle on the peak strength, peak strain, and crack initiation stress of specimens; and analyzed their strength and deformation behavior. Huang et al [14] carried out uniaxial compression test and numerical simulation study on granite samples containing three noncoplanar holes; analyzed the relationship between stress, acoustic emission (AE), and crack propagation process via AE measurement and image monitoring technology; and determined four typical crack coalescence modes. Yang et al [16] adopted two-dimensional (2D) particle flow numerical simulation and experimental methods to study the strength, deformation, and crack evolution behavior of sandstones with single elliptical holes under uniaxial compression. For the comprehensive understanding of the strength and failure behavior of rock materials with fissure holes, this study investigated the deformation characteristics, force chain distribution, and stress field evolution of rocks with the combination of vertical fissure ellipse and horizontal fissure ellipse by changing the ratio of major and minor axis of ellipse (changing the ratio of major and minor axis of ellipse is equivalent to changing the area of ellipse)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
