Failure Behaviour Simulation of Shale Layer Under Brazilian Test with Particle Flow Code

In this paper, Particle flow code in two dimensions was used to simulate the failure behavior of shale rock under Brazilian test conditions. The meso-mechanism and failure characteristics of shale under different bedding dip angles and bedding cementation strength were studied. The results show that: (1) Three major failure patterns under Brazilian test are tensile failure along shale matrix, tensile failure occurs along the bedding and tensile and shear composite failure along shale matrix and bedding; (2) Microcracks begin at the top and bottom loading points of the disk. When the load reaches the peak strength, a large number of microcracks expand and appear dense force chains until macroscopic fractures are formed. (3) The tensile strength anisotropy of shale samples is obvious, and the tensile strength decreases with the increase of bedding angle; The failure mode and tensile strength of specimens under different cementation strength ratio of bedding plane are also quite different. In this paper, the micro-macro fracture evolution mechanism of layered shale is analyzed by combining the micro-crack and force chain evolution process, and the research results and models can provide theoretical basis for the analysis of mechanical properties of anisotropic rocks and reservoir fracturing.