Abstract Phyllite, which is a low-grade metamorphic rock with well-developed foliations, is encountered frequently during the construction of tunnels in western China. First, uniaxial compressive creep tests were performed to study the time-dependent behavior of phyllite specimens from Zhegu mountain tunnel. Then, a numerical approach was put forward based on the particle discrete element method to describe the typical creep behavior of phyllite, including its decay, steady, accelerated creep stages, and its transverse isotropy. Finally, the numerical model was adopted to investigate the failure process of secondary tunnel lining in the phyllite stratum. The following results were obtained: Ai et al. (2014) (1) The creep behavior of phyllite was affected significantly by the weak plane-loading angles and water content. Its creep strength decreased as the water content increased, and the maximum and minimum values occurred at θ = 90° and 30°, respectively; Carrillo et al. (2016) (2) The fractal dimension of fracture surface for θ = 0° was the smallest due to the shear and tensile failure along foliations. For each angle, fractal dimension increased with the increase of water content; Chen et al. (2018) (3) Micro-cracks were initiated at the initial loading stage and propagated during the entire loading process at θ = 0°, while they appeared at a higher stress level after specimens had accumulated sufficient energy at θ = 30° or 90°; Chen et al. (2019) (4) The evolution of micro-cracks was affected jointly by the inclination angle of foliations and the geo-stress field, and the cluster of cracks shows evidently asymmetric features. The results revealed the transversely isotropic creep behavior of phyllite and proposed a method which can aid more accurate predictions for design and construction with respect to geotechnical engineering structures related to layered rock mass.

中文翻译：

---

千枚岩横向各向同性蠕变行为及其对隧道二次衬砌长期安全性的影响

摘要 千枚岩是我国西部地区隧道施工中经常遇到的一种页理发育的低品位变质岩。首先，进行了单轴压缩蠕变试验以研究来自浙古山隧道的千枚岩标本的时间相关行为。然后，提出了一种基于粒子离散元方法的数值方法来描述千枚岩的典型蠕变行为，包括其衰减、稳定、加速蠕变阶段和横向各向同性。最后，采用数值模型研究了千枚岩地层二次隧道衬砌破坏过程。获得了以下结果：Ai 等人。(2014) (1) 千枚岩的蠕变行为受弱平面加载角和含水量的显着影响。其蠕变强度随着含水量的增加而降低，最大值和最小值分别出现在θ=90°和30°处；卡里略等人。(2016) (2) 由于沿叶理的剪切和拉伸破坏，θ = 0° 的断裂面的分形维数最小。对于每个角度，分形维数随着含水量的增加而增加；陈等人。(2018) (3) 微裂纹在初始加载阶段开始并在整个加载过程中在 θ = 0° 扩展，而在试件在 θ = 30° 或 90° 积累足够能量后，微裂纹出现在更高的应力水平°; 陈等人。(2019) (4) 微裂缝的演化受叶理倾角和地应力场的共同影响，裂缝群呈现明显的不对称特征。