Anisotropic characteristics and deformation behaviors of layered rocks surrounding tunnel: A review
Xiaoyun Shu, Zhende Zhu, Shen Qu, Linkai He, Hongyan Zeng, Chaoxuan Zhang, Yun Tian
Abstract
Layered rocks are widely distributed in sedimentary and metamorphic rocks and show anisotropic deformation and strength due to the layered structures with apparent weak surfaces. This study summarizes the findings on the deformation and damage characteristics of layered rock masses and surrounding rocks. The physicomechanical properties of layered rocks with different properties (e.g. inclination, shear strength, tensile strength, shear stiffness, roughness, and layer spacing) and different lithological and stress conditions are analyzed. The results revealed that with increasing layer inclination angles, the deformation and strength parameters of the rock masses present U-shaped, W-shaped, incremental, decremental, and basically unchanged trends, which are closely related to their strength and stress conditions. The increase in layer strength and confining pressure effectively suppresses the deformation and strength anisotropy caused by layer weakening, and the rock mass shifts from “structure-controlled” to “stress-structure-controlled” deformation mode. Water will increase the anisotropic behavior of layered rock masses due to the degradation of bedding and bedrock performance. The anisotropic behavior of the layered surrounding rocks is analyzed to reveal how it affects the deformation and failure behaviors of tunnels. The asymmetric characteristics of surrounding rock deformation are closely related to the layer weakening, layer thickness, and in situ stress. These findings are crucial for understanding layered rock mass deformation and failure mechanisms, facilitating prediction and control of tunnel deformation.