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Shallow Tunnel Not Aligned with the Geostatic Principal Stress Directions
Despite the well-known stress anisotropy that may be present in rock masses, tunnel design is often done with the assumption that the tunnel is aligned with one of the geostatic principal stress directions. However, this alignment is improbable and so axial shear stresses may be unintentionally neglected. These shear stresses distort the tunnel cross-section in the axial direction, which is not accounted for in 2D analyses. In this paper, the effects of axial shear stresses on shallow tunnels misaligned with the principal in situ stress directions are assessed. 3D FEM models are conducted for that purpose and the results are compared with 2D plane strain models, often used in practice. Two scenarios are studied: competent rock mass, which behaves as a linear-elastic material, and soft ground, which undergoes plastic deformations. For soft ground, the axial stresses increase the size and change the shape of the plastic zone around the tunnel, thus inducing larger ground deformations.
Shallow Tunnel Not Aligned with the Geostatic Principal Stress Directions
Despite the well-known stress anisotropy that may be present in rock masses, tunnel design is often done with the assumption that the tunnel is aligned with one of the geostatic principal stress directions. However, this alignment is improbable and so axial shear stresses may be unintentionally neglected. These shear stresses distort the tunnel cross-section in the axial direction, which is not accounted for in 2D analyses. In this paper, the effects of axial shear stresses on shallow tunnels misaligned with the principal in situ stress directions are assessed. 3D FEM models are conducted for that purpose and the results are compared with 2D plane strain models, often used in practice. Two scenarios are studied: competent rock mass, which behaves as a linear-elastic material, and soft ground, which undergoes plastic deformations. For soft ground, the axial stresses increase the size and change the shape of the plastic zone around the tunnel, thus inducing larger ground deformations.
Shallow Tunnel Not Aligned with the Geostatic Principal Stress Directions
Vitali, Osvaldo P. M. (author) / Celestino, Tarcisio B. (author) / Bobet, Antonio (author)
Eighth International Conference on Case Histories in Geotechnical Engineering ; 2019 ; Philadelphia, Pennsylvania
Geo-Congress 2019 ; 214-222
2019-03-21
Conference paper
Electronic Resource
English
Shallow Tunnel Not Aligned with the Geostatic Principal Stress Directions
| British Library Conference Proceedings | 2019
Analytical solution for tunnels not aligned with geostatic principal stress directions
| British Library Online Contents | 2018
| Engineering Index Backfile | 1950