Longitudinal Equivalent Flexural Stiffness of Rectangular Pipe-jacking Tunnel in Integrated Pipe Gallery

Abstract

The rectangular pipe-jacking tunnel (RPJT) has a high section utilization ratio and is one of the primary forms of urban integrated pipe gallery (IPG) at present. This kind of tunnel will produce uneven longitudinal displacement under adjacent construction. Longitudinal bending stiffness is the crucial parameter to analyse its longitudinal stress characteristics. Combined with the structural elements of RPJT, the calculation models of the longitudinal bending stiffness of RPJT with round corners was put forward. The influence of longitudinal bolt number, ring width, and segment thickness on the neutral axis position and the longitudinal equivalent stiffness (LES) efficiency was further analysed. The influence of bending moment on the opening angle of the inter-ring joint was also analysed. The results show that increasing the number of longitudinal bolts, width of segment ring, and thickness of segment are beneficial to enhancing the LES efficiency and promoting the upward shift of the neutral axis. In addition, an increase of bending moment leads to the increase in the opening of the inter-ring joint, which is not conducive to structure safety. The research results can provide theoretical support for the structural design and longitudinal safety analysis of RPJT.