State-of-the-Art Technology in the Construction of Sea-Crossing Fixed Links with a Bridge, Island, and Tunnel Combination

In general, two kinds of structures are used to provide a way across a river, canal, sea, or other obstacle: bridge structures that pass over the obstacle, and tunnel structures that pass below the obstacle. Although the construction of both bridges and tunnels can be traced back over thousands of years, bridge–tunnel combinations that use an island as a sea-crossing fixed link (SCFL) have only been built over the past 82 years. The first such combination was probably the 6.4 km long San Francisco–Oakland Bay Bridge in the United States, which was completed in 1936. The most recently constructed SCFL combining a bridge, tunnel, and island is the Hong Kong–Zhuhai–Macau (HZM) Bridge, which opened for traffic on October 24, 2018 with the longest SCFL combination in the world, at a total length of 29.6 km. Over the 82-year construction history of SCFL combinations, 10 famous projects have been built around the world [1]. After the San Francisco–Oakland Bay Bridge, the Hampton Roads Bridge–Tunnel, also in the United States, was the second SCFL combination to be constructed. This SCFL combination is 9.72 km long and was completed in 1956; it was the first SCFL to be built with an artificial island between the bridge section and the tunnel section. Next, built in the United States in 1964, the Chesapeake Bay Bridge–Tunnel was the longest SCFL combination until the recent completion of the HZM Bridge. The Chesapeake Bay Bridge–Tunnel project includes 22.2 km of bridge, 3.2 km of tunnel, and four artificial islands. During the 1990s, three bridge– island–tunnel (BIT) combination projects were completed around the world: the Monitor–Merrimac Memorial Bridge–Tunnel in the United States, the Trans-Tokyo Bay Highway in Japan, and the Great Belt Fixed Link in Denmark. In the 21st century, three more BIT combination projects have been constructed thus far, in addition to the HZM Bridge: the Øresund Fixed Link linking Denmark to Sweden, the Shanghai Yangtze River Tunnel and Bridge in China, and the Busan–Geoje Fixed Link in Korea. Table 1 provides basic information on these 10 SCFLs with a BIT combination. Since an SCFL combination is usually comprised of one or more bridges, tunnels, and natural or artificial islands, along with the connections between these components, the construction technology for an SCFL system must include key techniques for building bridges, tunnels, and artificial islands. In order to make a comparison between the HZM Bridge and other SCFLs with a BIT combination, a state-of-the-art review of the construction technology has been performed on the bridges, tunnels, and artificial islands of eight of the abovementioned projects, in addition to the HZM Bridge, the Monitor–Merrimac Memorial Bridge–Tunnel was left out of the comparison because detailed information on this project was lacking.