Study the anisotropic behavior of layered surrounding rock based on 3D FDEM method

The anisotropic behavior of layered surrounding rock has always been a hot topic in underground engineering. This paper aims to investigate the deformation characteristics and crack evolution process of layered surrounding rock under excavation unloading conditions using the three-dimensional (3D) FDEM method. Firstly, the principle of 3D FDEM method is briefly introduced, and the transversely isotropic constitutive equation is embedded in the 3D FDEM method. At the same time, by implementing the GPU parallel algorithm based on CUDA, the code is optimized to improve the computational efficiency of the 3D FDEM method. Subsequently, the Brazilian splitting specimens and uniaxial compression specimens of layered rocks are numerically simulated to study the strength and deformation anisotropy characteristics of rock specimens with different bedding dip angles. The results indicate that the tensile strength of the model gradually decreases as the bedding dip angle increases. Moreover, the compressive strength of the model exhibits a U-shaped trend with an increase in the bedding dip angle. Notably, crack propagation within the model is significantly influenced by the bedding plane. Next, the 3D FDEM method is utilized to investigate the deformation and failure characteristics of horizontally layered surrounding rock in the Jiajinshan tunnel project. It is found that there are three types of failure cracks in the surrounding rock: conjugate shear cracks, shear cracks along the bedding plane, and tensile cracks perpendicular to the bedding plane. The deformation of surrounding rock is basically consistent with the field measurement value. Furthermore, a sensitivity analysis is conducted to examine the deformation and failure characteristics of the surrounding rock under different bedding angles. This research contributes to a comprehensive understanding of the anisotropic behavior of layered surrounding rock, especially for tunnel engineering, which is of great significance in adjusting the supporting measures for the surrounding rock.