Convergence - confinement analysis of deep circular rock tunnels based on unified strength theory

Based on the unified strength theory and a non-associated flow rule , a new analytical solution for ground reaction curve of a deep circular rock tunnel is presented taking into consideration the integrated effects of the intermediate principal stress, rock softening, dilatancy and a small Young’s modulus in the plastic zone. The Vlachopoulos’s formula due to its rationality is adopted to determine the relief ratio of longitudinal deformation of the tunnel . The support pressure differences anticipated from the convergence – confinement analysis between two methods for determining the initial location of support action are discussed. The results show that the influence of the unified strength theory parameter on the ground reaction curve and longitudinal deformation profile of the tunnel is significant. The strength potentials of rock mass are better achieved due to considering the effect of the intermediate principal stress. The effects of Young’s modulus in the plastic zone and dilatancy on the ground reaction curve are important. The differences of support pressure between two methods for determining the initial location of support action are remarkable.