The Hong Kong-Zhuhai-Macau Bridge, the world's longest sea-based project, comprises four parts: a 22.9-kilometer steel bridge, two artificial islands, a submerged sea tunnel extending for 6.7 kilometers, as well as leading bridges that connect the bridge to the cities.
For a bridge project, designers prefer to build all the structure on the ground, and only choose the tunnel when there is no alternative. However, for the HZMB, the most practical design is to integrate bridge, island and tunnel to form a complete cross-sea channel.
"The Pearl River Estuary （河口）holds a world-level shipping channel. Smooth traffic should be guaranteed. And the location is near the Hong Kong International Airport. With about 2,000 flights taking off and landing at the airport, the bridge cannot be built too high for safety reasons, said Meng Fanchao, chief designer of the project. "But you cannot have a submerged sea tunnel without any support. That forced us to build the artificial islands."
Chinese engineers declared a trail in installing deep-immersed tunnel tubes. There is no model for us to refer to as all the cases are shallow-buried tubes, said Meng.
"For lack of experience, the installation of the first tube lasted for 96 hours," said Yin Haiqing, deputy manager of the Project Management Department. "Everyone was exhausted when we made it."
The 6.7-kilometer tunnel is the world's longest submerged sea tunnel.
Two artificial islands, covering an area of 200,000 square meters, help create a smooth transition between bridge sections and tunnels. Different from traditional island, the engineers put 120 steel cylinders （圆柱）with a 22-meter diameter （直径）into the seabed, make out the shape of an island, and fill the island with soil. It is an innovative way they adopted to build the artificial island, making it firmer, more efficient and friendly to the marine ecology.
The HZMB provides a fixed link between the two Chinese economic centres Hong Kong and Macau and the mainland of China at Zhuhai.
