Longitudinal equivalent shear stiffness of shield tunnel segmental joints under axial force: Experimental and numerical study

Abstract

The longitudinal shear stiffness of segmental joints is a key parameter affecting the structural response of shield tunnels. However, the overall mechanical behavior of interring joints under combined axial force and shear loading remains insufficiently understood. In this study, a series of model tests were conducted using 3D‐printed segments and aluminum alloy bolts. A dedicated loading system was developed to investigate the shear response of inter‐ring joints under different axial forces. The results show that the longitudinal equivalent shear stiffness exhibits significant nonlinear characteristics with increasing shear force, which can be qualitatively divided into three characteristic stages: static friction, elastic shear, and plastic shear stages. Axial force enhances inter‐ring contact and friction, thereby effectively restraining joint dislocation and improving shear stiffness. Numerical simulations were carried out and validated against experimental results, showing good agreement. Parametric analyses were further performed to quantify the effects of axial force and friction coefficient on shear stiffness. A logistic model was proposed to describe the nonlinear variation of equivalent shear stiffness. The results indicate that the stabilized shear stiffness increases with axial force and is significantly influenced by friction conditions. The findings provide useful references for longitudinal deformation analysis and design of shield tunnel linings.