Abstract: The structure response of the underwater shield tunnel during operation is important in studying the overall stability of the tunnel. Based on the health monitoring system of Wuhan Yangtze River Tunnel, the strain and joint monitoring data of the tunnel structure over one year (from April 2022 to April 2023) were obtained. In this study, the response patterns and differences in strain and joint opening between the under-river section and the bank section were compared, and a method for calculating the normal stiffness of segment circumferential joints was proposed. The results show that: (1) the average annual amplitudes of segment strains and joints opening of the bank sections are much greater than that of the under-river section; (2) The influence of temperature on the strains and joints opening of the bank sections are greater than that of the under-river section; (3) The normal stress-joints opening curves of the circumferential joint are similar to the normal stress-displacement curve of the rock joints, but the curve shape differs at different monitoring positions. The average normal stiffness at multiple monitoring points is similar during both the opening and closing stages. The normal stiffness of the circumferential joint in the under-river section is significantly greater than that in the bank section.

Key words: shield tunnel, segment strains, segment joints, joint stiffness