Seismic performance study of immersed tunnel with longitudinal limit device of flexible joint

Flexible joints represent the most vulnerable aspect of the immersed tunnel, necessitating effective waterproofing and the transmission of forces between tunnel segments. However, the role of longitudinal limit devices in the seismic behavior of immersed tunnels is frequently overlooked in contemporary research on their seismic robustness. This study develops a longitudinal force model for flexible joints that incorporates the longitudinal limit device, building upon the beam-spring model of the immersed tunnel. Concurrently, a scaled partial experiment on the immersed tunnel's flexible joint is undertaken, and validated and compared to the theoretical model. Subsequently, this model is utilized in the seismic assessment of the Ruyifang immersed tunnel. The computational findings revealed a considerable improvement in the seismic resilience of the immersed tunnel following the integration of longitudinal limit devices. With the incorporation of these devices, the opening of flexible joints diminished by 20% to 50% compared to scenarios lacking such devices. In addition, the peak acceleration of the tunnel segments' mid-point structural response decreased by approximately 50%, accompanied by a significant reduction in the internal force response within the tunnel segments. As proposed in this research, the longitudinal force model for flexible joints under longitudinal limit devices represents the behavior of immersed tunnels under seismic stress more accurately. These numerical simulation outcomes also offer valuable insights for designing flexible joints in immersed tunnels.