Discrete element simulation on failure mechanical behavior of transversely isotropic rocks under different confining pressures

A large number of experimental investigations on anisotropic behavior of transversely isotropic rock have been conducted recently, and the strength and deformation anisotropy and macroscopic failure behavior and failure mechanism were studied in detail. However, the internal variation and microscopic failure mechanism of transversely isotropic rock have been rarely determined by laboratory tests, and few studies have reported these types of results. This paper presents an investigation of particle flow code in 2 dimensions (PFC2D) simulation on transversely isotropic rock under different confining pressures based on laboratory experiments. The transversely isotropic PFC2D model is established by the bonded-particle model (BPM) and the smooth-joint model (SJ) to represent the layer materials and weak planes, respectively. To reflect the experimental specimens accurately, BPM and SJ microparameters are calibrated first. The simulated strength and deformation anisotropy of transversely isotropic rock under different confining pressures are all consistent with the experimental specimens and can reflect the macroscopic failure behavior and failure mechanism of experimental specimens very well. On a microscopic level, the internal variation and microscopic failure mechanisms of transversely isotropic rock are studied in detail, and four types of microcracks, namely PB tensile cracks and PB shear cracks, which exist in the layer materials, and SJ tensile cracks and SJ shear cracks, which exist in the weak planes, are recorded and counted to reveal the microscopic failure mechanisms of transversely isotropic rock at different orientation angles. The evolution processes of microcracks and PB forces are also analyzed to investigate internal variations during the failure of transversely isotropic rock under different confining pressures.