Full-scale tests on bending behavior of segmental joints for large underwater shield tunnels

This paper presents an experimental and numerical study on the bending behaviour of segmental joints for large underwater shield tunnels. A series of full-scale tests of segmental joint for underwater shield tunnel are carried out to investigate the bending performance under compression-bending loads. And comparative numerical simulations are conducted to compare with the test results and analyze the occurrence and development process of joint failure. The results indicate that the joint opens linearly and deforms nonlinearly after the visible concrete cracking occurred, the shape of joint interface is a curved surface during joint opening. The time when the bolt becomes stressed depended on axial force, and the bolt stress increased linearly with the growth of bending moment. Joint bending stiffness can be divided into three stages according to turning point of visible concrete cracking' and bolt yield', large axial force has a great influence on keeping it. The joint waterproof material could hardly promote the bending stiffness and capacity of segmental joint for its small rigidity. The failure process of segmental joint was different between under positive and negative bending moment, the compressive capacity of concrete in compression zone near the intrados played a vital role in the process of improving the bending capacity of segmental joint. The numerical results of joint opening and bending stiffness were in good agreement with tests during small deformation stage, while after visible cracking the results differ relatively. It is reasonable to simulate joint bending performance before visible concrete cracking, and estimated joint failure mode and its approximate range by using the proposed numerical model.