Mechanics of longitudinal joints in segmental tunnel linings: A semi-analytical approach

Abstract

To meet basic structural serviceability and durability requirements throughout the life of tunnels, the design and evaluation of segmental tunnel linings requires accurate structural models. Considering that segmentation introduces non-trivial kinematics to the lining system, it is important to properly evaluate the moment-rotation relationship for longitudinal joints. In this study, a nonlinear semi-analytical model is proposed to assess the mechanical behavior of the longitudinal joint, taking into account the nonlinear behavior of the concrete in the vicinity of the joint and the contact deformation induced by the roughness of the contact surface. Through the proposed model, the moment-rotation relationship of the joint and the stress distribution in the vicinity of the joint are obtained simultaneously without the need for highly resolved finite element analyses. It is demonstrated how the proposed model can be applied to parametric analysis of joint configurations and to predict tensile stresses that may cause spalling and splitting cracks. The performance of segmental joints is systematically investigated, revealing a more accurate distribution of the contact pressure and the deformations and the stress field within the joint influence zone. To fully consider the influence of the joint, the effective joint rotation angle is defined to consider the additional rotational flexibility resulting from the joint-induced deformations, which attributes to the contact deformation and the disturbed stress field within the joint influence zone. Since the joint rotation angle calculated based on the classical rigid plate assumption (nominal joint rotation angle) tends to overestimate the effective joint rotation angle, a correction factor relating the nominal and the effective joint rotation angles is proposed for practical applications.