Abstract
Rock masses may present remarked stress anisotropy or fabric structure, such as foliation and bedding; thus, it is likely that a tunnel is misaligned with the geostatic principal stress directions, with the principal material directions, or with both. Anti-symmetric axial displacements and axial shear stresses are induced as a consequence of the tunnel misalignment. However, the effects of the misalignment near the face are still unknown. In this paper, the 3D face effects on tunnels misaligned with the geostatic principal stress directions and/or with the material principal directions are investigated. 3D FEM modeling is conducted for unsupported and supported tunnels. A transversely anisotropic elastic model is selected to represent the structured rock mass. The results show that misaligned tunnels undergo asymmetric deformations near the face. The radial deformations far-behind the face are symmetric for unsupported tunnels, but they are asymmetric for supported tunnels. The reason for this is that asymmetric deformations near the face affect ground-support interaction. As a consequence, the internal forces in the tunnel support are also asymmetric; further, the support forces may be larger than those of a tunnel aligned with the geostatic principal stress.
Published Version
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