The effective flexural stiffness of segment joints in large‐diameter tunnel under various loading conditions

Abstract

AbstractLarge‐diameter shield‐driven tunnels are widely adopted in road projects to accommodate the increasing traffic load all over the world. As the diameter of lining ring increases, the jointed segmental lining will be subject to more complex external loading condition, which results in highly nonuniform and nonlinear internal forces. The segment joints, depending on loading condition, would exhibit different mechanical behaviors. An accurate characterization of the effective flexural stiffness of the joints is essential to the accurate evaluation of the lining internal forces. In this work, the mechanical behaviors of the joints are categorized into six different cases, and in each case the effective flexural stiffness of the joints is derived accordingly. To calculate the lining internal forces, the force method equations are first established, with the consideration of various external loading condition (e.g., earth pressure, grout buoyancy force). In the force method equations, the effective joints stiffness is also a variable, which will be adjusted based on the mechanical behavior of the joints. The nonlinear force method equations are then solved by the fixed‐point iteration method. The proposed framework is applied to a large‐diameter shield‐driven tunnel in China. It is found that the joints at different locations exhibit distinct effective flexural stiffness. The joints subject to positive moment exhibit quite greater flexural stiffness than that subject to negative moment. The grout buoyancy force is shown to have significant impact on internal force distribution and deformation of the lining. A field monitoring was carried out on the tunnel segments during the construction, and the monitoring data are in good agreement with the calculation results, which further confirms the correctness of the conclusions mentioned above.