Effects of rock mass anisotropy on deformations and stresses around tunnels during excavation

rock mass where the in situ state of stress is uniform. The rock mass was assumed to behave elastically and two cases were examined: whether the rock mass has an isotropic elastic property or not. A two-dimensional plain strain elastic-plastic Jointed Rock model was used to study the response of the rock mass to excavation. The elastic behaviour of the rock mass was assured in the model by simply providing adequate cohesion. The study reveals that the distribution of excavation-inducedstresses and deformations in the space surrounding rock mass having anisotropic properties differs from that obtained under the assumption of isotropic properties. The neglect of the effect of elastic anisotropy can result in a significant underestimation of stresses and displacements in rock and thus also in the design of support measures and the final pressure tunnel linings. Additionally, when the tunnel geometry is circular and the rock mass contains one joint set where the plane of elastic anisotropy strikes to the tunnel axis, the results obtained for one dip angle will be identical to another dip angle by rotating the x- and y-axis accordingly