A three-dimensional transversely isotropic equivalent continuum model for layered rock and numerical implementation

The failure of layered surrounding rock tunnel is significantly related to bedding occurrence and in situ stress orientation, and often shows asymmetry. This is because the layered rock has a special bedding structure, resulting in its deformation and failure showing significant anisotropy. After excavation, the bedding loading angles of layered rock around the tunnel are different, resulting in different bearing capacity of each part of the tunnel. To reflect this characteristic, a three-dimensional equivalent continuous model considering the deformation and strength anisotropy of layered rock is developed, and the model is embedded in CASRock numerical software. The simulation of tunnel excavation in layered surrounding rock shows that the change of bedding dip angle will lead to the change of failure position of the tunnel, and with the increase of the angle between bedding strike and tunnel axis, the failure degree of surrounding rock will be greatly reduced. This model can be used to investigate the influence of in situ stress and bedding occurrence on the stability of layered surrounding rock tunnels.