Seismic Response of Shield Tunnel with Double-Layer Lining

Abstract

A shield tunnel is an assembly structure composed of connecting bolts and segments, generally considered to have good seismic performance. However, there is still a possibility of damage occurring in shield tunnels under strong seismic action. Therefore, a secondary lining can be applied on the inner side of the segment lining to improve the overall seismic performance of the shield tunnel. Using the Shiziyang Shield Tunnel as a case study, this paper employs numerical analysis to examine the seismic response characteristics of the shield tunnel with overlapped double-layer lining. Subsequently, it investigates the influence of segmental lining stiffness degradation and tunnel burial depth on the internal forces of the tunnel under seismic loads. The results indicate that under seismic loading, the stress in the segmental lining exceeds that in the secondary lining, with the maximum stress being three times higher. As the segmental lining stiffness decreases, the bending moment of the segmental lining decreases accordingly, while the secondary lining bending moment remains relatively constant. The bending moment of the segmental lining consistently surpasses that of the secondary lining. Furthermore, the variation in the axial force of the segmental lining is not significant, whereas the axial force in the secondary lining notably decreases. With increasing burial depth, the bending moment of the tunnel structure initially increases and then decreases. As the burial depth of the tunnel increases from 0.5D to 2D and 5.0D, the ratio of the maximum positive bending moment between the segmental lining and secondary lining first decreases and then increases, which are 7.56, 4.78, and 7.70, respectively. Similar patterns are also observed in axial forces. A burial depth of 2D is the critical depth between shallow and deep burial. When the tunnel is shallowly buried, the overlying strata have a significant impact on the seismic internal forces of the tunnel, which continue to increase with increasing burial depth. When the tunnel is deeply buried, it is subjected to the confining action of the strata, making it relatively safe, and the internal forces of the tunnel continue to decrease with increasing burial depth. Overall, under seismic loading, the segmental lining remains the primary load-bearing structure in a tunnel structure with double-layer lining.