Study on Mechanical Characteristics of Segmental Joints of a Large-Diameter Shield Tunnel under Ultrahigh Water Pressure

Abstract

At present, there is no clear design standard for segmental joints of large-diameter shield tunnels under high water pressure. In this paper, a theoretical calculation model for the bending stiffness of segmental joints under high water pressure is proposed. The numerical simulation method is used to investigate the failure and crack formation processes of single-layer and double-layer lining segments under large axial forces. The effects of axial force, bolt strength, and concrete strength on the bending stiffness of joints are then studied using a theoretical calculation model of segmental joints. The results show that under extremely high water pressure, the influence of double lining on joint stiffness is limited. It is more rational and safe to compute the bending stiffness of segmental joints using this theoretical model rather than the numerical simulation method. The parameter analysis reveals that increasing the bolt strength has a minor impact on bending stiffness and deformation, whereas increasing the concrete strength has the opposite effect. The influence of ultimate bearing capacity and deformation decreases non-linearly as the axial force increases.

The Optimization of Secondary Lining Construction Time for Shield Tunnels Based on Longitudinal Mechanical Properties

“…In response to these phenomena, some shield tunnel projects [14,15] adopted double-layered lining structures, using a secondary lining as a safety reserve or reinforcement measure to ensure the safety of the shield tunnel structure. Compared with single-layered shield tunnels, double-layered structures are applied in smaller areas and remain concentrated in large-diameter river-crossing or sea-crossing tunnels [16] and water transfer tunnels [17]. In the early double-layered shield tunnel projects, the segment lining was generally used as the load-bearing structure, while the secondary lining was used as an auxiliary structure to improve the durability and water resistance of the shield tunnel.…”