Dynamic Response of Curved Tunnels under Vertical Incidence of Transversal SV Waves

Long tunnels often have curved sections when alignment designs are influenced by topography, adverse geology, and environmental factors. When the transversal SV wave is incident vertically, the curved section of the tunnel is subject to a connection between longitudinal and transversal loads, which are asymmetrical about the tunnel longitudinal axis. Compared to straight tunnels, curved tunnels are more complex in terms of forces and deformations and may become a key control section limiting the seismic safety of curved tunnels. To investigate the seismic response of curved tunnels, numerical simulations of curved tunnels with different radii of curvature under transversal SV seismic waves were carried out in this study. Local artificial boundaries were programmed and used for the 3D rock tunnel interaction system model to simulate semi-infinite rock and to eliminate fake reflections of seismic waves on local boundaries. The results show that longitudinal deformation and cross-sectional deformation occurred simultaneously in curved tunnels when the transversal SV wave was incident vertically. As the curvature increased, the longitudinal deformation of the curved tunnel increased. The cross-section of the tunnel was in oblique compression, and the cross-sectional internal force showed significant asymmetry. When the radius of curvature was 250 m, the difference in bending moment between the left and right haunch was 35.2%. These characteristics differ from those of straight tunnels and should be paid attention in the seismic design of curved tunnels.