On the water and under water – Hong Kong and Macau getting ever closer

Hong Kong/Zhuhai/Macau – Three Chinese cities with special status are to grow together physically and economically thanks to a project which is in a class of its own. Approximately 35 kilometres must be bridged, literally, to connect Hong Kong to Macau via Zhuhai. Between these cities lies the wide stretch of water of the Pearl River estuary. Hong Kong intends to pull off this huge task using a six-lane road bridge – except for the section that cuts across an area of international shipping lanes, which will instead see the construction of the world's longest underwater road tunnel. This will require engineering and planning expertise, as well as highperformance technology from the German construction machinery manufacturer Putzmeister

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The project office of the Hong Kong-Zhuhai-Macau Bridge has an ambitious project to tackle. To facilitate driving from the Hong Kong metropolis to the Chinese mainland along the fastest route, a link is to be created to Macau via Zhuhai. The aim is to reduce the driving time from Hong Kong to Zhuhai down from the current four hours to just one hour. The main part of this expensive project will involve a link bridge, and, where the route crosses the shipping lane, a tunnel at a great depth under water. This is why the project includes two artificial islands, on which the entry and exit portals for the tunnel can be constructed. A stretch of approximately 6 km in a tunnel at a depth of 40 m, i.e. below the shipping channels, will soon be in place. Planners and contractors contractually agree to ensure that the bridge and tunnel design will be able to withstand forces of nature, such as wind speeds of up to 200 kilometres an hour and earthquakes of up to magnitude 8. Once finished, the tunnel will consist of 33 sections, each of which will be 180 m long. It is estimated that the project will cost around 11 billion US dollars. The foundation stone was laid in May 2010, and the project is due for completion in 2016.

On the safe side with Putzmeister
In order to carry out the project reliably and successfully, the client has joined forces with experienced partners. Companies such as the international consulting group COWI A/S, Peri and Putzmeister were already successfully involved in the spectacular construction of the technically comparable Öresund Tunnel between Denmark and Sweden. The two projects are similar in that it stood to reason to make use of the expertise and experience of these companies to make a success of this construction project as well.

As early as the planning phase, close collaboration was going on between Putzmeister and Peri, manufacturer of the two formwork casings, which are made of large sections and will be opened hydraulically. "In a mammoth project such as this, it is absolutely imperative to be fully agreed on the details", explains Michael Höss, the Putzmeister engineer responsible for this project. "The plan is to manufacture all 33 sections of tunnel on land. Each tunnel section consists of eight individual segments, 22.5 m long, 40.5 m wide and 11.3 m high. In order to meet the project aims, this calls for expert, professional planning – as much during the formwork placing and positioning phase as during concrete placement".

On the two production lines, each formwork (designed by PERI) consists of one stationary bottom formwork, one anchorless outer casing, three casings inside the tunnel to house two motorway carriageways and one service gallery. For concreting each segment with 3600 m3 of concrete, there is a window of just 24 hours. The fully automatic formwork is then stripped, the segment moved forward by 22.5 m and the next segment concreted against it. Then, using an incremental launching facility, the segment is moved out of the production hall and into the flood basin. Once eight segments are ready, they are joined together and sealed. The basin is flooded, and the eight segments are then towed by ship as a complete, 180 m-long tunnel section to the installation position, sunk in a controlled operation and overfilled to secure the section in its position. Until the operation is complete, 890,000 m3 of concrete is processed for the 264 segments.

Harmonized equipment and expertise are the recipe for success
On the island of Guishan, off the coast from Zhuhai, Putzmeister has six BSA 2109 stationary concrete pumps in operation. Four MX 32-4 stationary booms, all of which move on rails, place the concrete. To convey the volume of concrete that has to be placed within 24 hours, the four stationary booms work simultaneously on one segment. For optimum, speedy concrete placement, RV 8 rotary distributors hang from the formwork support structure, above the base plates. The concrete is conveyed from the stationary concrete pumps to the four stationary booms via ZX 125/5 high pressure delivery lines, designed for 130 bar, with an overall length of approx. 120 m. "This set-up ensures that approx. 150 m³ concrete per hour can be poured into the formwork within the time allowed", affirms Mr Höss. Work is being taken care of by employees from the Putzmeister branch in Shanghai during the entire production period. They provide maintenance and other services within the quickest of lead times.

Hong Kong
Hong Kong is situated on China's southern coast, and, since the British handed it back to China in July 1997, is a city with a special status, as are Zhuhai and Macau in fact. With its seven million inhabitants, this metropolis is the third largest city in China, and lies precisely at the point where the Pearl River empties into the South China Sea. The total territory of Hong Kong covers the peninsula and a further 262 islands, such as Lantau, Hong Kong Island and Lamma. The financial and business centre of the city is situated in the north of Hong Kong Island. According to a doctrine developed by Deng Xiaoping, the role of Hong Kong as one of the greatest financial centres in the country would be maintained at least 50 years later. This is because, in addition to the socialist system of the People's Republic of China, the democratic economic system also remains. The influence of the mainland on internal politics makes itself felt. The Hong Kong-Zhuhai-Macau link project is also in the political and economic interest of China. The plan is to merge Hong Kong with Macau, with the aim of creating an important economic centre. Guangdong, the province to which Zhuhai belongs, should also benefit from this plan.