Study on deformation patterns of tunnel isolation layers and seismic response of a shield tunnel

Tunnel seismic isolation is an effective measure to reduce the seismic response of tunnels; however, the unclear mechanism limits the popularization and application of this measure. In this study, the deformation patterns of tunnel seismic isolation were investigated using theoretical analyses and shaking-table experiments. The analytical solution for the dynamic response of the seismic isolation tunnel under SH-wave incidence was derived using the wave-function expansion method. A novel loading device based on the reaction-displacement method was used to study the mechanism of the tunnel seismic isolation layer. It was found that the seismic isolation layer helped reduce and spread the deformation from the outer surface to the inner surface, effectively minimizing the deformation affecting the lining. The DSCF response of the lining is subsequently reduced. Moreover, the installation of seismic isolation did not result in a significant alteration in the acceleration response of the tunnel. These results provide a reference for the seismic isolation design of tunnels.