A New Form of Longitudinal Joint of Large Cross-section Segmental Tunnel Linings

Abstract

The resistance of longitudinal joint is a crucial design parameter on the mechanical properties and structural behavior of precast tunnel segmental linings constructed by the Tunnel Boring Machine (TBM). Recently, with the increased dimensions and functions of the shield tunnel, the traditional bolted connection forms (e.g., straight bolts, inclined bolts, curved bolts) for segmental joints may not meet the requirement of safety or usage. This study tries an effort to propose an optimized form of bolted joint, which is a combination of both straight bolts and incline bolts, on the basis of a detailed three-dimensional (3D) finite element (FE) model. The developed FE model is first validated against the full-scale joint mechanical experimental results in terms of the joint failure mode and bearing capacity. The computed results agree well with physical observations at low bending moment and bearing capacity. An optimal study on the design parameters of bolted joints is then undertaken using the validated FE model. According to the test results, the bearing capacity of the optimized joint under the positive and negative moment case is approximately 70% and 200% of the short straight bolts joint, respectively. As the practical outcome of this study, a series of FE analyses are performed to investigate the joint behavior with different bolt parameters. Based on the numerical results, it is suggested that the proposed new form of joint is applicable to design cases where the axial force is moderate, especially for negative moment cases, for example, water-conveyance tunnel under internal load.