What are the natural reasons for the difficulties in the construction of Hangzhou Bay Bridge?

Hangzhou Bay Bridge is a convenient passage across Hangzhou Bay, the trunk line of China National Highway. It starts from Zhengjiadai, Haiyan, Jiaxing City in the north and ends at Shuilu Bay, Cixi City, Ningbo City after crossing the wide Hangzhou Bay, with a total length of 36 kilometers, of which the bridge is 35.67 kilometers long. Hangzhou Bay Sea-crossing Bridge is the longest sea-crossing bridge built or under construction in the world. After the completion of the bridge, the land distance between Ningbo and Shanghai will be shortened by about 1.20 km.

Hangzhou Bay Bridge is designed as a two-way six-lane expressway with a design speed of 100km/h, a design service life of 100 years and a total investment of about11800 million yuan. The bridge has two passages, north and south. Among them, the North Channel Bridge is a rhombic steel box girder cable-stayed bridge with twin towers and double cable planes with a main span of 448 meters, with a navigation standard of 35,000 tons; Nanhang Road Bridge is a type A steel box girder cable-stayed bridge with single tower and double cable planes, with a main span of 3 18m and a navigation standard of 3,000 tons. The remaining approach bridges are all made of prestressed concrete continuous box girder structures of 30 ~ 80m. The bridge project is guaranteed to start in 2003, be completed in 2008 and be opened to traffic in 2009.

Characteristics of engineering environment

The weather in Hangzhou Bay is complex and changeable, and typhoons, tornadoes, thunderstorms and sudden small-scale disastrous weather occur from time to time. The natural conditions of Hangzhou Bay have the following characteristics:

(1) The sea area is vast, with many typhoons, large tidal range and fast current, which has typical maritime climate characteristics and few effective working days;

(2) Deep soft soil and deep bearing stratum bring a series of problems to the design and construction of offshore foundation;

(3) The South Beach is long, and the construction conditions are complicated, so it is difficult to meet the requirements of the construction period by using conventional design schemes and construction methods;

(4) The environment is corrosive;

(5) Shallow gas is enriched in many places in the south beach, which endangers the construction safety.

2. Difficulties in engineering construction

(1) The project scale is large, and the offshore engineering quantity is large. The total length of the bridge project is 36 kilometers, and the offshore section is 32 kilometers. The whole bridge has a total of 2.45 million cubic meters of concrete, 820,000 tons of various kinds of steel,+03,565,438 steel pipe piles, 3,550 bored piles, 0/272 caps/kloc and 65,438 piers, and the project scale is huge.

(2) The natural environment is harsh. The tidal range is large, the flow velocity is fast, the flow direction is chaotic, the waves are high, and the erosion is deep. In some areas, the soft soil layer is thick and the shallow gas is rich. Among them, the south bank 10 km beach area is dry and wet alternately, and most offshore projects are offshore operations, so the construction conditions are poor. Affected by hydrometeorology, there are few effective working days. According to on-site construction statistics, the annual effective days of offshore construction operations are less than 180 days, and the tidal flat area is about 250 days.

(3) It is very difficult to make the overall design scheme. The design requirements are new, in which the approach bridge in the underwater area (18.27km) and the approach bridge in the south bank beach area (10. 1km) are the key points of the whole project. The problem of structural corrosion protection is very prominent, and there is no standard to follow; In the process of bridge operation, the driving environment on the bridge deck is affected by unfavorable factors such as strong wind, dense fog, heavy rain and driver's visual fatigue. It is the key to ensure the driving safety on the bridge deck to adopt reasonable and effective design countermeasures. The design scheme involves the application of new materials, new processes and new technologies and the development of a number of large-scale special equipment.

In terms of construction technology, it faces many key construction challenges, such as overall prefabrication, transportation and erection of large-tonnage box girder in high pier area of offshore rapids, long-distance transportation and erection of large-tonnage box girder in wide beach area, design of super-long spiral steel pipe pile, anti-corrosion and pile sinking construction. In the aspect of measurement control, the deformation of structure measurement caused by the effect of super-long bridge length and earth surface is very prominent. Due to the limitation of marine environment, the traditional measurement methods can no longer meet the requirements of construction accuracy and progress. How to realize rapid and efficient survey construction with the help of GPS technology is the core technical problem that restricts the construction period of the whole bridge.

(4) The construction objectives are demanding, and the construction organization and operation management are difficult. This large-scale bridge project has attracted worldwide attention. At the beginning of the construction, Ningbo Municipal Party Committee and Municipal Government clearly put forward that the bridge project should be implemented according to the standard of "three first-class goals". Facing the complex construction environment and challenging projects, how to organize and manage the bridge project is a great challenge for the headquarters. Due to the large number of construction sites and long battle lines, there are synchronous and overlapping processes, which brings difficulties to organizing construction and controlling project quality, progress, safety and funds. How to take effective engineering control and operation management measures under meteorological and hydrological conditions such as typhoon, strong wind, spring tide, huge waves, rapids, heavy rain, fog and lightning is a new topic that needs to be faced in engineering management.