Scientific and Technological Innovation and Operation-related Issues for Island-Tunnel of Hong Kong-Zhuhai-Macao Fixed Link Project
【Abstract】The author explains why a giant undersea immersed tube tunnel was selected for the sea area of the main channel of the east side of the Hong Kong-Zhuhai-Macao Fixed Link Project, instead of employing a bridge or shield tunnel; and summarizes several domestic and international leading innovative technologies applied in the island-tunnel construction of the Hong Kong-Zhuhai-Macao Fixed Link Project, including the use of huge self-stabilized steel cylinders as retaining structure of foundation pits for constructing the artificial islands, the large-area and ultra-deep “sand compaction pile (SCP) composite foundation” reinforcement technology, “semi-rigid segment joints”, “sandwich” steel-RC combined inverted-trapezoid closure joints, and crack control and anti-corrosion/durability design for RC tube structure. All these technologies reflect Chinese wisdom and Chinese speed. The author also points out some technical issues to which attention should be paid after the immersed tube tunnel of the project is put into operation: (1) Will the post-construction settlement and differential settlement of the immersed tube tunnel further develop after the project is open to traffic? How much is the final convergence value? If it exceeds the limit, what control measures should be taken? (2) How to deal with the issue that the joints of large/small elements or segments are open? How to ensure that all the large and small joints between segments of the tube are “watertight”? Furthermore, the author presents some suggestions and control measures: (1) For excessive post-construction settlement (especially differential settlement) spotted on large joints, it is suggested to incorporate “micro-disturbance grouting” for post treatment. (2) If a joint opens under the excessive positive bending moment at the floor slab, it is believed that the open joint on the floor slab can be closed again by cutting off some prestressed tendons in the roof slab of the segment to reduce the positive bending moment of the section.
【Keywords】 Hong Kong-Zhuhai-Macao Fixed Link Project; immersed tube tunnel; island-tunnel works; huge self-stabilized steel cylinder retaining structure; “8-hammer synchronous vibration-sinking” technology; “SCP composite foundation” technology; semi-rigid segment joints; steel-RC combined inverted-trapezoid closure joints; concrete crack contro; anticorrosion/durability design; post-construction settlement; differential settlement; joint leakage and treatment;
 CHEN Yue. Review on construction technology of tunnel and artificial islands for Hong Kong-Zhuhai-Macao Bridge [J]. Construction Technology, 2013, 42 (9): 1 (in Chinese).
 SUN Jun. Countermeasures for deep and thick soft foundation under serious back-silting condition: Case study of artificial island and immersed tunnel of Hong Kong-Zhuhai-Macao Bridge Project [J]. Tunnel Construction, 2014, 34 (9): 807 (in Chinese).
 CHEN Shaozhang, SU Zongxian, CHEN Yue. New technologies used for immersed tunnel of Hongkong-Zhuhai-Macao Bridge Project [J]. Tunnel Construction, 2015, 35 (5): 396 (in Chinese).
 YIN Haiqing. Key technologies applied in design and construction of artificial islands and immersed tunnel of Hong Kong-Zhuhai-Macau Bridge (HZMB) Project [J]. Tunnel Construction, 2014, 34 (1): 60 (in Chinese).
 SUN Jun. Exploration on structural treatment of segment joint of immersed tunnel of Hong Kong-Zhuhai-Macau Bridge Fixed Link Project with serious back silting on soft ground foundation [J]. Underground Engineering and Tunnels, 2014 (1): 1 (in Chinese).
 LIN Ming, LIU Xiaodong, LIN Wei, et al. General discussion on steel-concrete composite sandwich immersed tunnel structure [J]. China Harbour Engineering, 2016, 36 (11): 1 (in Chinese).
 YOU Chuan, HU Zhi, WANG Li. Manufacturing technology of closure joint for immersed tube of Hong Kong-Zhuhai-Macao Bridge [J]. Roads, 2018 (8): 94 (in Chinese).