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.

中文翻译：

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基于3D FDEM方法研究层状围岩各向异性行为

层状围岩的各向异性行为一直是地下工程的研究热点。本文旨在利用三维（3D）FDEM方法研究开挖卸荷条件下层状围岩的变形特征和裂纹演化过程。首先简要介绍了3D FDEM方法的原理，并将横观各向同性本构方程嵌入到3D FDEM方法中。同时，通过实现基于CUDA的GPU并行算法，优化代码，提高3D FDEM方法的计算效率。随后，对层状岩石的巴西劈裂试件和单轴压缩试件进行数值模拟，研究不同层理倾角的岩石试件的强度和变形各向异性特征。结果表明，随着层理倾角的增大，模型的抗拉强度逐渐减小。此外，随着层理倾角的增大，模型的抗压强度呈现U型趋势。值得注意的是，模型内的裂纹扩展受到层理平面的显着影响。接下来，利用3D FDEM方法对夹金山隧道工程水平层状围岩变形破坏特征进行研究。研究发现，围岩存在三种类型的破坏裂缝：共轭剪切裂缝、沿层理面的剪切裂缝和垂直于层理面的拉伸裂缝。围岩变形与现场实测值基本一致。此外，还进行了敏感性分析，考察了不同层理角度下围岩的变形破坏特征。该研究有助于全面认识层状围岩的各向异性行为，特别是对于隧道工程，对于调整围岩支护措施具有重要意义。