Flexural behavior of segmental joint containing double rows of bolts: Experiment and simulation

Flexural behavior of segmental joints plays a crucial role in the design of lining structure of shield tunnels, and many novel joints are proposed to enhance its flexural behavior. This paper presents a comprehensive investigation of the flexural behavior of a new segmental joint containing double rows of bolts, proposed for a deepburied shield tunnel in Shanghai, via the full-scale experimental tests and refined numerical simulation. Both the positive and negative moment loading scenarios are considered. The flexural behavior of segmental joints containing double rows of bolts shows obvious nonlinear characteristics and the moment-rotational angle curve can be divided into three stages: linear growth stage, plastic development stage and ultimate failure stage. Thus, a tri-fold line stiffness model is proposed to describe the nonlinearity of joint stiffness, which can be easily implemented into the spring-beam model. Compared to the segmental joints using only single row of bolts, the joint containing double rows of bolts has a higher joint stiffness and bearing capacity. Meanwhile, the bending capacity of joints increases with the axial force. For the failure mode, the positive bending condition is characterized by the spalling of concrete in the compression zone and the fracture of joint panel; while the tensile failure of bolt is found under negative moment scenario. All these characteristics are obtained in the tests and well interpreted by the simulation.