Experimental and analytical study on longitudinal joint opening of concrete segmental lining

Abstract

Longitudinal joint opening is a common distress in shield tunnel operation. Existing longitudinal joint models are mainly developed for the design of segmental lining, but the real behavior of longitudinal joints in operational tunnels may exceed the normal design range. The aims of this paper are to study the development of longitudinal joint opening with bending moment under different axial stress levels, and investigate the longitudinal joint opening in the Ultimate Limit State (ULS). Firstly, full-scale tests on the longitudinal joints that are adopted in the Shanghai Metro Line No. 13 are conducted. The longitudinal joints are continuously loaded until completely damaged. Secondly, based on the test observations, a progressive model is proposed to predict the mechanical behavior of the joint. The proposed model is then verified by the test results. Lastly, using the proposed model, the influences of the axial stress level, bolt pretightening force, concrete delamination depth and bolt corrosion depth on the mechanical behavior of the joint are investigated. The following conclusions are drawn from the analysis: (1) Longitudinal joint opening is highly dependent on the axial stress level. For the joint subjected to the same bending moment, the larger the axial load, the smaller the joint opening. (2) Generally, the joint opening decreases with the increasing of bolt pretightening force, and increases with the increasing of concrete delamination depth and bolt corrosion depth. (3) The joint opening in the ULS increases with the increasing of axial load for the sagging moment case, and decreases for the hogging moment case. The structural state based on joint opening and the effects of joint configuration are also discussed.