Design and Research of the Bending Test Set-up for the Longitudinal Joints in Segmental Tunnel Linings

As a weak link of the segmental lining ring in the shield tunnel, joints are main reasons for large deformation which further lead to various diseases during the tunnel construction and operation. These diseases, including water leakage, dislocation, joint opening, concrete crack etc., are detrimental to the safety and durability of the tunnel structure. In order to better understand the mechanical behaviour of joints, especially the longitudinal joints, much more attention have been paid to carry out corresponding experimental study. However, the design of the test-up is rarely covered in a lot of literature, which is also a critical factor for a successful experiment. In this paper, a test-up used for experimental study of the longitudinal joints in segmental tunnel rings was designed and executed in detail. The test device met both the test site requirements of the Building Structure Laboratory of Tongji University and the bearing capacity requirements under the maximum test load. After calculating the maximum horizontal and vertical test loads, the design of the test device system was completed. The setup included a short column, transverse and longitudinal loading beams, hinge supports, segment sleeves, supporting platforms and pillars. The test device can realize bidirectional loading and meet the requirement of large deformation of the test members during the test, which can provide a reference for the design of similar or even more sophisticated segmental joint test devices in the future.