Motion response of immersing tunnel element under random waves

Abstract

The Hong Kong–Zhuhai–Macau Link project crosses the ocean water of Ling Ding Yang and includes a 10 km long bridge section and a 6 km submerged tube tunnel section. The submerged tube tunnel is to be placed in the base trench at the seabed under 40 m water depth (d). Each tunnel element is 180 m in length, 11.4 m in height and weighs 72,000 tons in air. All tunnel elements are to be constructed on yards onshore, towed to the site location, linked to two stabilising floating pontoons and then ballasted and immersed at the site location with an exposed open wave environment. To ensure that the tunnel element can be immersed and then landed safely and accurately on the base trench during the process, an experimental study with scale model tests was performed to investigate the motion responses of the immersing tunnel element linked to the floating pontoons under random waves. The experimental measurements revealed quantitatively the motion behaviour under different wave climates, immersion depths and negative ballasted buoyancy. The results also demonstrated that the dynamic response of the tunnel element was most severe during the stage of freeboard elimination. The experimental measurements during the freeboard elimination stage were also compared to the numerical simulations for further analysis. Overall, an important conclusion from this study is that the freeboard elimination scenario should be checked against cable breakages and the stability of the tunnel element in the design stage, which has not been highlighted in the literature so far. Also, with the quantitative information, the study illustrates how the weather window for the tunnel element immersion can be determined.

Keywords:

• tunnel element immersion
• random waves
• motion responses
• freeboard elimination
• weather window

Acknowledgements

The work is supported by the Fundamental Research Funds for the Central Universities of China through Grant No. DUT14QY08 and the State Key Laboratory of Coastal and Offshore Engineering Research Foundation, China, through Grant No. SL2012-2. The authors would like to thank Project Management Department for Island and Tunnel Project of Hong Kong–Zhuhai–Macau Bridge Joint Venture of China Communications Construction Co., Ltd. for the kind permission to publish this paper. The authors would like to thank the anonymous reviewers for their valuable comments, which improved the quality of this manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The work is supported by the Fundamental Research Funds for the Central Universities of China [grant number DUT14QY08] and the State Key Laboratory of Coastal and Offshore Engineering Research Foundation, China, [grant number SL2012-2].