A three-dimensional numerical study on the stability of layered rock spillway tunnels in alpine canyon areas
Peng‐Zhi Pan, Fuyuan Tan, F Li, Fudong Chi, Xufeng Liu, Zhaofeng Wang
Abstract
The rock mass in alpine canyon areas exhibits strong heterogeneity, discontinuity, and is subject to strong tectonic effects and stress unloading, resulting in extremely complex distribution of in-situ stress. In addition, the occurrence of layered rock masses makes it more complex, with obvious anisotropic mechanical properties. This study proposes a comprehensive method for evaluating the stability of layered rock spillway tunnel in a hydropower station in alpine canyon area. First, the failure criterion and mechanical model of layered rock mass considering the anisotropy induced by the bedding plane and the true triaxial stress condition are presented. Then, an inversion theory and calculation procedure for in-situ stress in alpine canyon areas are introduced. Finally, by using a self-developed numerical tool, i.e. CASRock, the stability of the layered rock spillway tunnel in a hydropower station is numerically studied. The results show that, affected by geological structure and stratigraphic lithology, there is significant differentiation in the in-situ stress in alpine canyon areas, with horizontal tectonic stress as the main factor. The occurrence of layered rock masses in the region has a significant impact on the stability of surrounding rock, and the angle between the bedding strike and the tunnel axis as well as the bedding dip both have a significant impact on the failure characteristics of surrounding rock.