Impact of surface-reflected seismic waves on the seismic isolation performance of circular tunnel isolation layers

Seismic isolation is an effective strategy to mitigate the risk of seismic damage in tunnels. However, the impact of surface-reflected seismic waves on the effectiveness of tunnel isolation layers remains under explored. In this study, we employ the wave function expansion method to provide analytical solutions for the dynamic responses of linings in an elastic half-space and an infinite elastic space. By comparing the results of the two models, we investigate the seismic isolation effect of tunnel isolation layers induced by reflected seismic waves. Our findings reveal significant differences in the dynamic responses of the lining in the elastic half-space and the infinitely elastic space. Specifically, the dynamic stress concentration factor (DSCF) of the lining in the elastic half-space exhibits periodic fluctuations, influenced by the incident wave frequency and tunnel depth, while the DSCF in the infinitely elastic space remain stable. Overall, the seismic isolation application of the tunnel isolation layer is found to be less affected by surface-reflected seismic waves. Our results provide valuable insights for the design and assessment of the seismic isolation effect of tunnel isolation layers.