POSTER PAPER PROCEEDINGS

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1 ITA - AITES WORLD TUNNEL CONGRESS April 2018 Dubai International Convention & Exhibition Centre, UAE POSTER PAPER PROCEEDINGS

2 Advanced Developments in Steel and RC Immersed Tunnels Hideki Sakaeda 1, Ozturk Ozgur 2, Chor Kin Tsang 3 1 Executive Director at AECOM, Hong Kong SAR, hideki.sakaeda@ aecom.com 2 Technical Director at AECOM, Hong Kong SAR, ozturk.ozgur@ aecom.com 3 Technical Director at AECOM, Hong Kong SAR, ck.tsang@ aecom.com ABSTRACT By the help of recent advanced technologies and innovative solutions in steel and reinforced concrete immersed tunnels, very deep and very long sea crossings under challenging ground and environmental conditions becomes feasible and competitive. Sandwich or hybrid immersed tunnels are popular in Japan where both internal and external surfaces are constructed by structural steel plates. Steel diaphragm plates and shear connectors are used between internal and external surfaces, filled with non-shrinkage self-compacting concrete, eliminating the necessity of reinforcement bars. 72 On the other hand, the mega highway immersed tunnel project, Hong Kong - Zhuhai - Macao Bridge Link (HZMB) is currently under construction as reinforced concrete immersed tunnel where segmental full-face casting technique has been applied. It is the first very long immersed tunnel project with two artificial islands in the open sea in China, connecting Hong Kong SAR, Zhuhai (PRC) and Macao SAR once completed. High quality concrete and full-face segmental casting minimized cracking risk. In addition, submersible floating tunnels are also being considered to be built in the future which may extend the immersed tunnelling technology one more step further. This paper discusses about the recent advancement of immersed tunnel construction technologies by giving examples from the recent projects. Key Words: Reinforced Concrete, Steel, Hybrid, Immersed 1. INTRODUCTION With the advanced technologies and the innovative solutions in immersed tunneling in the recent years, deeper and longer sea crossings with longer design life criteria under challenging ground and environmental conditions became feasible and competitive compared to other tunneling methods. Depending on various criteria such as material prices, workmanship, experience, robustness, durability and similar, construction method of immersed tunnels could be mainly reinforced concrete (with or without waterproof membrane) or steel. Examples are given below for both reinforced concrete and steel immersed tunnel design and construction referring to recent projects. 2. RC AND STEEL IMMERSED TUNNELS IN HONG KONG Immersed tunnels may have various advantages when crossing a river or sea. They can be built shallow, permitting shorter tunnels and flatter alignments than bored

3 tunnels. They do not require thick covers, minimizing excavation risk under water by pre-excavation of trench. Immersed tunnel cross sections are highly versatile, making them particularly suitable for wide highways and combined road/railway crossings. They can be prefabricated remotely from the final immersion site (i.e. at Dry Docks), allowing installation in extremely congested (e.g. urban) locations where nearby land is not available. A good example of this is Hong Kong, where there are five immersed tunnels under operation and two under construction as of The tunnel elements are prefabricated remotely from the final immersion site. Figure 1 shows immersed tunnels in Hong Kong which are under operation or construction. Figure 1. Immersed Tunnels in Hong Kong (Completed and Under Construction) Since the first Cross Harbour Tunnel was constructed using the immersed tube technique in 1972, four other immersed tunnels were successfully constructed to cross Victoria Harbour in Hong Kong. The sixth immersed tunnel crossing the harbour (no.7 in Figure 1) is currently under construction. Table 1 summarises the details of immersed tunnels which are under operation and under construction in Hong Kong. 73

4 Table 1. Immersed Tunnels in Hong Kong No Tunnel Year of Completion Tunnel Type Length (m) No. of Railway Track No. of Traffic Lanes 1 Cross Harbour Tunnel 1972 Singleshell Steel Binocular Section 1,602-2 x 2 2 MTR Harbour Crossing 1979 Reinforced Conc. Double Binocular 1, Eastern Harbour Crossing 1989 Reinforced Concrete Box 1, x 2 4 MTR Airport Railway Tunnel 1996 Reinforced Concrete Box 1, Western Harbour Crossing 1997 Reinforced Concrete Box 1,364-2 x 3 6 Central Wanchai By-Pass Ongoing Reinforced Concrete Box x 3 7 Shatin to Central Link Ongoing Reinforced Concrete Box 1, In Hong Kong both steel shell and reinforced concrete with all common crosssections were used. The following Figure 2 to Figure 8 shows all the structural forms and cross-sections of immersed tube tunnels in Hong Kong. Figure 2. Cross Harbour Tunnel Single-shell Steel Binocular Section 74

5 Figure 3. MTR Harbour Crossing Tunnel Pre-stressed Reinforced Concrete Binocular Section Figure 4. Eastern Harbour Crossing Reinforced Concrete Rectangular Section Figure 5. Airport Railway Immersed Tunnel Pre-stressed Reinforced Concrete Rectangular Figure 6. Western Harbour Crossing Reinforced Concrete Rectangular Section 75

6 Figure 7. Central Wanchai By-Pass Reinforced Concrete Rectangular Section Figure 8. Shatin to Central Link Reinforced Concrete Rectangular Section 3. ADVANCED RC IMMERSED TUNNELLING FULL-FACE SEGMENTAL METHOD The reinforced immersed tunnels in Hong Kong were constructed by traditional casting method which is also called Monolithic Method having construction joints between each casting phase. The traditional casting method has higher risk of cracks when casting fresh concrete against old concrete. One of the advanced methods to minimize cracking risk, a new technique of full-face casting was introduced at Oresund Link tunnel between Denmark and Sweden and this method was also adopted to Busan-Geoje Fixed Link in South Korea (2010) and HZMB Link connecting Hong Kong, Zhuhai and Macau which is under construction. The construction of the HZMB Link, including bridges, immersed tunnel and two artificial islands construction is now ongoing. The tunnel and bridges will accommodate a dual carriageway with 3 traffic lanes in each direction. Since the project is being built in the Zhujiang River Estuary and open sea, the design and construction of tunnels and artificial islands face a series of grand engineering challenges, for example, the long distance ventilation and safety design (6-kilometers in length and 40-meters in depth) of the tunnel, fabrication of precast elements weighing nearly 80,000 tons, severe environmental conditions, foundation, siltation as well as construction of the west and east artificial islands. 76

7 Figure 9. HZMB Link Longitudinal Profile Figure 10. HZMB Link Cross Section In order to ensure the intended design life of the tunnel, low permeable, crackfree concrete is important for reinforced concrete immersed tunnels. In HZMB project, each tunnel element consisted of 5~8 nos of shorter sections which is called segments. Each segment is approximately 22.5m in length. The segments are cast continuously without any construction joint (full-face casting). This method helped to minimize the cracking risk. 77

8 Figure 11. HZMB Link Tunnel Element During Prefabrication 4. STEEL IMMERSED TUNNELS NAHA UMISORA TUNNEL (JAPAN) There are few types of steel immersed tunnels such as single shell, double shell, open-sandwich or full sandwich (hybrid). Steel provides a robust formwork as well as waterproofing. In Japan, some immersed tunnels are constructed as fullsandwich or Hybrid method. This method has superior advantages in terms of waterproofing and seismicity. In principle, steel plates are used at both outer and inner surfaces of the tunnel element, and reinforcement is eliminated. Steel diaphragm plates and shear connectors (steel profiles, flat bars) are welded to the steel surfaces, and filled with self compacting concrete (SCC). Using self compacting concrete also eliminates the need of using vibrators. One of the good example of this method is Naha Umisora Tunnel in Okinawa, Japan (2011). Figure 12. Naha Umisora Tunnel Longitudinal Profile 78 Steel boxes were prefabricated in factories in several locations and transported by semi-submersible barge to the site with a distance of approx. 1500km of open

9 sea (Figure 13). Near the construction site, in-fill self-compacting concrete with 30MPa compressive strength was cast afloat at a jetty (Figure 14). The tunnel had a minimum radius of R=1000m on the horizontal alignment. Figure 13. Naha Umisora Tunnel Transportation of Steel Elements Figure 14. Naha Umisora Tunnel Afloat Self Compacting Concrete Casting 5. STEEL IMMERSED TUNNELS A CASE STUDY FOR EXTRA WIDE AND HIGH TUNNEL ELEMENTS Currently BART immersed tunnel (Bay Area Rapid Transit San Francisco) is the longest immersed tunnel under operation. Hong Kong Zhuhai Macau Bridge Link (HZMB Link), under construction, will reach approximately 6km once completed. AECOM is the Construction Management consultant for the contractor`s JV at HZMB Link project. Fehmarnbelt Fixed Link to connect Denmark and Germany is planned to be approximately 18 km. Total 79 nos standard elements (each approximately 217m long) and 10 nos extra wide and high (special) tunnel elements are planned for technical installations. During tender design of Fehmarnbelt Fixed Link, AECOM designed special elements as full-sandwich (hybrid) method (Figure 15). Both Eurocode and Japanese codes were taken into account and due to contract requirement Eurocode was adopted. 79

10 Figure 15. Full Sandwich (Hybrid) Cross Section Sandwich (hybrid) type of immersed tunnels were mainly constructed in Japan until now and one tunnel element was partially constructed with the same method in Turkey (Bosphorus Crossing). Advantages and Disadvantages of this method may include the following in general: Advantages: Very high quality Structurally sound and robust No crack concern No rebar installation Very good water-tightness Concrete can be cast even at immersion site Disadvantages: Steel prices affect overall cost due to larger amount of steel use compared to RC tunnels Significant welding and testing, qualified shipyard, SCC (self compacting concrete) required Cathodic Protection is usually required 6. CONCLUSION With the advanced technologies and the innovative solutions in sub-sea tunnel crossings in the recent years, very deep and very long sea crossings with immersed tunnel under challenging ground and environmental conditions becomes feasible and competitive. Depending on various factors, immersed tunnels can be designed and built by reinforced concrete or steel as samples given in this paper. It requires careful analysis to determine the most suitable method for a particular immersed tunnel project. 80

11 7. CITATIONS AND REFERENCES 1) Joseph Y.C. Lo, C.K. Tsang (2008) The State-Of-Art Technology for Immersed Tube Tunnel In Hong Kong and Korea. 2) Reference materials by Penta-Ocean Construction Co. Ltd Japan 3) Hong Kong Zhuhai Macau Bridge Link Design and Construction Methodology Documents by CCCC 81

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