Effects of intermediate principal stress on the displacement around tunnels in visco-elastoplastic rock

To evaluate the effects of intermediate principal stress on the displacement around tunnels, this paper discusses the problem using a unified yield criterion and a non-associated flow rule. The time-dependent behavior is simulated by Kelvin model, consisting of a spring and a cohesive element with parallel connection. The effects of dilatancy and creep of rock are considered in the solution. The general tunnel engineering analysis is characterized by the usage of Mohr-Coulomb (MC) or Hoek and Brown yield criterions that neglect the effects of intermediate principal stress. The unified strength theory, with intermediate principal stress on failure surface concerned, is applied to tunnel engineering. It has been shown that the displacement around tunnels using linear MC criterion, a special case of those in the paper, may be overestimated in rock.