Bending performance of Y-shaped joints of subway station built by enlarging two parallel shield tunnels

Abstract

Based on the characteristics of the Y-shaped joint of a subway station built by enlarging two parallel shield tunnels, a bending mechanical model of the segmental joint was proposed. The model was used to characterize the cracking and crushing of concrete, the yielding of the bolt, and the damage of the segmental joint. Theoretical equations were derived for the bending stiffness of the joint under various forms of joint opening. Bending experiments were conducted on full-scale models of the joints under different structural configurations. The results demonstrated that the nonlinear properties of the joint structure were evident under loading and that the bending stiffness of the joint initially increased and then decreased. The computed values were in good agreement with the experimental results for the pre-embedded connector joint when lc was 0.5 times the height of the compression zone, where lc was the effect depth of the compressive deformation of the outer edge of the concrete. The axial force had a great influence on the bending stiffness. The mechanical performance of the joint was influenced not only by the change in the stress–strain curve of the concrete from the rising stage to the descending stage but also by the structural morphology of the rotational angle of the joint.