Hong Kong bridge: engineering marvel links three cities

The fantastic 1983 vision of a Hong Kong tycoon is now being realised with the construction of the mammoth Hong Kong-Zhuhai-Macao Bridge.

Builders of the Hong Kong-Zhuhai-Macao Bridge, which will be the world’s longest bridge over water, overcame one of the most complex challenges ever to confront engineers. The Y-shaped span, which will link the three cities, incorporates the latest engineering technology and design, enabling the structures to withstand a magnitude 8 earthquake, a super typhoon or a strike by a cargo vessel weighing 300,000 tons.

Engineers were confronted with complex geological and topographical conditions, taking into account prevailing winds and tidal forces.

From an artificial island near Hong Kong International Airport, the structure runs west to another artificial island off the eastern shore of Macao, a distance of 34.2 miles, 20 times the length of San Francisco’s Golden Gate Bridge. The bridge, which is expected to open by the end of the year, will also connect to a town being built on reclaimed land in Macao.

A journey by land, which can take up to four hours, will be shortened to as little as 30 minutes, according to official projections. Though officially called a bridge, it is in fact a series of bridges and tunnels crossing the Pearl River estuary – 18.6 miles above water, 4.3 miles of underwater tunnels and a number of artificial islands.

The major section will provide a dual three-lane expressway to handle traffic up to speeds of 100 km/h. The total bridge width is 108.6ft, with two 46.7ft tunnels and a vertical clearance of 16.7ft.

As many as 4,000 ships a day are expected to navigate waters above the tunnel, serving ports around the estuary.

The artificial islands constructed at the ends of the sea tunnel are reinforced by 120 giant steel cylinders, each 73.8ft in diameter and 180ft high, equivalent to the height of an 18-storey building. Each cylinder weighs 550 tons, about the same as the world’s largest passenger jet, the Airbus A380.

A total of 400,000 tons of steel was used in the project, equivalent to 60 times the steel used to build the Eiffel Tower. The bridge is designed for a 120-year lifespan. Most big, cross-sea bridges are designed to last 100 years, according to historical data.

The new bridge also required close attention to environmental issues in the Pearl River Delta, including corridors that sustain marine life. That meant the bridge design had to take into account river channels, fundamental hydrology and navigation routes to ensure the natural ecosystem was not disrupted and channels blocked.

Su Quanke, chief engineer of the Hong Kong-Zhuhai-Macao Bridge Authority, said in a briefing that his team had overcome more than 80 technical obstacles to lay a solid foundation for the bridge.

“All its major units are standardised,” he said. “The manufacturing is industrialised. The installation can be implemented on a large scale with refinement of detail.”

Moreover, it uses a digital control system and its maintenance can be easy and efficient. He said: “These practices have received recognition from the bridge design and construction industry around the world.”

Meng Fanchao, chief designer of the bridge, said the design team sought advice of experts in various fields, including environmental protection, navigation, hydrology, aviation, social economy, bridge engineering, engineering technology and meteorology.

Finally, the team selected the route from among a dozen final proposals after scientific appraisals, Mr Meng said.

A blueprint for the project first appeared in 1983 almost as a fantasy of the Hong Kong tycoon Gordon Wu Ying-sheung. His vision was to accelerate integration of the two sides of the Pearl River.

Originally, the project was not supposed to include tunnels between Tuen Mun in Hong Kong and Zhuhai, Guangdong province. Zhuhai was then in its early stages of development. As one of the first special economic zones set up by the central government in the 1980s to attract foreign investors, the city needed better transport linking it with Hong Kong, Mr Wu said in his proposal.

After 1997 the authorities saw potential in the plan. The original design was dropped and planning started on a link from Zhuhai and Macao, linking to Hong Kong’s new international airport.

After negotiations between the three cities’ authorities, in 2009, the State Council nailed down the final plan, and construction began the same year.

The cost of the bridge is estimated to exceed 115.9 billion yuan (£13.2 billion), the bridge authority said.

Source: telegraph.co.uk

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