Elastoplastic solutions to deep-buried circular tunnels in transversely isotropic rock masses considering intermediate principal stress

The influence of intermediate principal stress is usually ignored for the problem of a deep-buried circular traffic tunnel under plane strain condition. But the deformation of surrounding rocks in plastic area has greater error. A number of layered rock masses occur in geotechnical and underground engineering and they are often treated as the transversely isotropic solid materials. To consider the influence of the intermediate principal stress on deep-buried circular tunnels, plane strain hypothesis is given and the new Drucker-Prager criterion compatible with the transversely isotropic materials is obtained. Then Mohr-Coulomb criterion is precisely matched to the new Drucker-Prager criterion. The analytical expression of the intermediate principal stress in plastic state for the transversely isotropic perfect elastoplastic materials with dilatancy is deduced based on the criterion. According to the expression of the intermediate principal stress, the analytical expressions of the displacement and stress in plastic area for a deep-buried circular tunnel in transversely isotropic rock masses can be obtained. A practical engineering case is given and the regularities that transversely isotropic parameters and dilation angle act on the displacements in the plastic area of the deep-buried circular highway tunnel in transversely rock masses are discussed. So, the elastoplastic solutions may provide a more reasonable theoretic basis for the calculation and design of the deep-buried circular traffic tunnels.