Numerical modelling of the transverse dynamic behaviour of circular tunnels in clayey soils

In this paper different approaches aimed at investigating the dynamic behaviour of circular tunnels in the transverse direction are presented. The analysed cases refer to a shallow tunnel built in two different clayey deposits. The adopted approaches include one-dimensional (1D) numerical analyses performed modelling the soil as a single phase visco-elastic non-linear medium, the results of which are then used to evaluate the input data for selected analytical solutions proposed in the literature (uncoupled approach), and 2D fully coupled FE simulations adopting visco-elastic and visco-elasto-plastic effective stress models for the soil (coupled approach). The results are proposed in terms of increments of seismic-induced loads in the transverse direction of the tunnel lining. The different constitutive hypotheses adopted in the coupled numerical approach prove to play a significant role on the results. In particular, the plasticity-based analyses indicate that a seismic event can produce a substantial modification of the loads acting in the lining, leading to permanent increments of both hoop force and bending moment.