Optimization of the mooring configuration on a typical tunnel-pontoons system

Guoxing Huang, Yue Song, Yuguo Pei, Ningchuan Zhang, Zhong'an Shao

Friday 3 july 2015

13:30 - 13:45h at Amazon (level 1)

Themes: (T) Water engineering, (ST) River and coastal engineering

Parallel session: 16E. Engineering - River

In South China, the Hong Kong-Zhuhai-Macau Link is constructed to connect Hong Kong, Zhuhai and Macau. The traveling time from Hong Kong to Zhuhai or Macau will be reduced from 4.5 hours to approximately 40 minutes upon completion. This mega infrastructure consists of three kinds of section: a man-made island, a bridge section as well as a tunnel section crossing the offshore water of Ling Ding Yang, which is supposed to be the world longest and widest immersed tunnel after completed. The dimensions of the largest element are of 180 m in length, 11.4 m in height and 72,000 tons weight in air. All tunnel elements are to be constructed in nearby yards on shore, towed to the immersion location, and then moored on the sea surface above the trench on standby for immersion. During the standby stage, the tunnel-pontoons system may expose to harsh offshore wave and weather conditions, and the mooring lines might experience excessive tension or even breakage. For this reason, an experimental study was carried out on the hydrodynamic responses of tunnel element during immersion standby under waves and currents. Based on Froude number similarity, models of one tunnel element, two pontoons and the mooring system were constructed at a scale of 1:65. The tensions on the mooring lines with various angles were measured under pure wave and combined wave-current conditions with various wave heights and current velocities. After comparing the dynamic responses of the tunnel-pontoons system under various mooring configuration, the optimal mooring configuration of the tunnel-pontoons system was recommended for ensuring the safety of the tunnel element during immersion standby.