How was the bridge built? What was the hardest part? Why?

The Hong Kong-Zhuhai-Macao Bridge is the miracle bridge with the largest span, the longest length, the longest tunnel, the largest steel structure and the longest service life in the world. It is a superbridge of bridges, islands and tunnels in the world and has been named one of the Four Wonders of the Modern World by The Guardian. When it comes to modern bridge construction in China, we have to mention one person, and that is Mao Shengsheng.

He was the founder and guide of modern bridge construction in China. He designed and built China's first modern bridge, the Qiantang River Bridge, and was also involved in the construction of the Wuhan Yangtze River Bridge and invented several pier construction methods.

To build a bridge pier, you must first be familiar with the conditions of the ocean, such as depth, silt, rocks, etc., and finally according to the current technology, equipment, and then design drawings, the bridge pier is equivalent to a land foundation, the foundation is not firm, and the mountain is shaking. The caisson method is to transport it to the bridge pier construction site, and then control the amount of ballast water in the box, so that the special tank sinks to the bottom of the sea, and then input high-pressure air to prevent groundwater from entering the caisson. It's like an empty cup snapping into the bottom of the water, we fill it with air, and the water is quickly discharged, and the workers can enter the workshop under the caisson through the pressure change chamber and the lifting shaft.

The excavated soil is transported mechanically, the caisson is in a state of digging and sinking until the specified depth, the bottom of the tank is sealed, and finally the workshop is filled with concrete in order to obtain a pier. The so-called cofferdam, simply put, is to enclose the construction area of the pile foundation of the cross-sea bridge, pump the water clean, expose the underwater ground, and then directly install equipment for drilling. After the pile foundation and piers are completed, the cofferdam is removed and the waters around the piers are restored to their original state.

To put it simply, the pile sinking method is to drive each pile with different functions directly from the seabed to the seabed through a piling ship to reach a predetermined height. According to the different seabed geology, there are friction piles, end bearing piles, reinforced concrete piles, steel piles, wood piles, sand and gravel piles, etc.

The advantage of the pile sinking method is to use advanced piling equipment to improve efficiency and save labor costs, but it will hinder the waterway to a certain extent. Making piers in shallow water can save costs. There is one more problem.

The piers must be on a rock layer in order to be stressed. Some rock layers are buried very deep with silt, and some are very shallow with silt. Therefore, in the design, it was necessary to find rocks that were buried shallow by silt as piers.

If the rock is buried shallowly, the piers will be short. If it's short, it saves money. If the pier falls on the rock, it will not sink.

What if the design can't find shallow water and the rock is buried deep in silt? The design changed the design concept, they designed the friction pile, is to design the pile length, so that the silt around the pile produces upward friction, when the friction is large enough, the load transmitted by the bridge deck will not cause the pile to produce sliding force.

First of all, it is necessary to drive piles, there will be professional piling ships to measure the predetermined position, and then use special instruments to drive into the seabed, after the piling is completed, the bearing cap must be made, and the paving solitaire can be done after the bridge piers and bridge lights are repaired; I think the most difficult part should be piling, the economic level at that time, science and technology were not particularly developed, so the construction also depends on the specific water situation, and it is necessary to study the seabed and the soil quality of the seabed, so it will be particularly difficult.

The piers of the Haiqiao Bridge are formed by laying the foundation through offshore drilling and casting cement using the "caisson bridge construction technology". After the piers are built, the pavement is paved and the cable-stayed bridge reinforcement is used to stabilize the bridge body. China's bridge construction technology is the world's first.

The hardest part is that the bridge is highly corrosive.

The buoyancy is great.

The sea-crossing bridge is built with high-tech design, a lot of special materials, and humanized design concepts; The hardest part is the construction, the difficulty of the technology; Because the requirements for technology and construction are very high for sea-crossing bridges, it is necessary to make accurate judgments and clever designs.

First, the sea-crossing bridge was built on the inland seaTarget. First of all, the piers are operated by professional tools and are not built in deep seas. Most of the piers were built at the mouth of the river, and engineers did not choose to build them at a depth of several hundred meters or kilometers.

The engineer formulated according to local conditions and adopted a suitable construction plan for the smooth construction of the bridge. The most important thing is to look at the condition of the seabed underwater. For the construction of bridge piles, the quality of the soil on the seabed should also be checked.

The anti-corrosion standard of high-speed rail engineering structure is 100-year anti-corrosion, and the main anti-corrosion method for steel structure is to choose durable heavy anti-corrosion coating.

The second is to rely on their own experience and advanced technology to determine the location of the bridge pier. It is not easy to lay the foundation of a bridge pier in the water, so it is necessary to put a steel ring in the water, then drive the steel ring into the seabed, and weld the second ring to the first ring until it becomes a large circle pipe. What should be considered is the accumulation of sediment on the piers.

The more docks, the more sediment that can block the passage of the waterway. First of all, it is necessary to consider the passage of waterways.

The second is the concrete composite beam, which is composed of a concrete bridge deck and a channel-shaped steel beam. The steel girder is lightweight, which is suitable for the construction of long-span bridges, while the concrete bridge deck improves the stiffness of the bridge. The combination of the two meets the requirements for the passage of high-speed trains.

On long-span sea-crossing bridges, the laying of ballastless tracks and the passage of high-speed trains have extremely high requirements for the structural stiffness, creep deformation and dynamic performance of the bridge. After several simulation tests, the design team found the structural parameters of the steel-concrete composite beam suitable for the long-span marine environment.

In addition, the steel is corrosion-resistant with nickel and streamlined box-shaped wind resistance. Compared with ordinary bridges, cross-sea bridges also face another test, that is, sea breeze and seawater corrosion, which is a common problem faced by marine engineering construction in all countries in the world. In humid air, the water film formed on the surface of the steel will dissolve carbon dioxide, sulfur dioxide, hydrogen sulfide and other gases in the atmosphere, so that the water film contains a certain amount of hydrogen ions to form a film containing electrolyte.

This is exactly the same as in steel. Iron and a small amount of carbon make up the galvanic cell.

Under each pier there is a cap, and in the shallow water near the shore, the cap is constructed using the cofferdam method.

There are two ways of cofferdam method, the first is to use steel sheet piles, and the other is to use earth-rock dams, where the water is blocked in shallow seawater, and the position where the bridge piers are to be built, and then the water and sediment in the enclosed area are drained by a pumping machine until the ground is exposed.

This creates a cofferdam in the middle, in which workers can work, similar to work on land. When the work is completed, the steel plate outside the cofferdam is removed. This method is suitable for construction in shallow water, and the difficulty is relatively low, but it requires a large amount of space, which is time-consuming and labor-intensive, and has a certain impact on the surrounding water environment and marine life.

The bridge is built using large-scale medical equipment combined with artificial and high-tech construction methods, and generally needs to be graded first, and gradually begin to rise after the foundation is built on the seabed. Most of the bridges were shot with instruments weighing hundreds of tons.

All the structures of the bridge will be built first, and then assembled by installation. The piers are secured by instruments and then locked below sea level.

How was the bridge built? How did the piers go down in such a deep sea? So how do you build so-called bridge piers beneath the seabed? In fact, China already has four sets of mature construction plans.

The first set: caisson method. As we mentioned earlier, the state of the seabed is best in the form of a mixture of sediment and sediment.

The so-called caisson method is to directly insert some very long hollow molds into the seabed, which is similar to a well from the surface, and then do a good job of watertight measures, and then use a pumping machine to drain the water in the space mold, at this time it is like an empty well, and then inject reinforced concrete into it, and after a few days, the mold is removed, and a submarine pier is built.

The second set: the cofferdam method, which can also be understood as a method of containment. To put it simply, it is to use the equipment prepared in advance to enclose the place where the bridge piers need to be built, and do a good job of watertight measures.

Then the water in the area is drained, and there is a clearing without water, and then the workers can go straight in, do the pile foundation and start building the piers, and the next steps are similar to what we do on land. After the construction is completed, the surrounding enclosure equipment is removed and the sea area is restored to its original appearance.

The third set: pile foundation, this method will involve piling, just like driving wooden piles to drive the stone pier into the seabed, so the stability of this kind of construction of the building is very high, generally able to bear a relatively large weight, but this kind of method has high requirements for construction technology, and the construction period is also relatively long. This method is often used in situations where the wind and waves are strong and the bottom of the sea is relatively deep.

This method is often used to construct the piers of high bridges on land.

The fourth set: pile sinking method. The implementation of the pile sinking method will rely on the engineering ship I worked on before, and with the help of the ship, the bridge pier built in advance will be driven directly into the seabed.

It is worth noting that the piers of this method are inclined and not too aesthetically pleasing, and they are fixed on the surface of the rock to ensure that the pile foundation can be firmly fixed in the sea. Generally, we use this method more when building ports, which is not only efficient, but also more stable.

The total length of the Hong Kong-Zhuhai-Macao Bridge is 55 kilometers, except for about 7 kilometers of undersea tunnels that do not need piers, the rest are supported by bridge piers, and there are as many as 224 piers of the whole bridge, which can be imagined how difficult it is. At present, the Hong Kong-Zhuhai-Macao Bridge has been successfully opened to traffic, and has been praised by the whole world, which can be described as a major architectural miracle of mankind in the 21st century.

The construction of a sea-crossing bridge is a complex process, the most important of which is to drive the piers to the bottom of the sea.

Piling, a professional piling ship transports the prefabricated piles to a predetermined location and drives them directly to the seabed using special machinery.

If it is a shallow water low pile cap, the steel sheet pile cofferdam is used to separate the water to make the cushion cap, and if it is a deep water high pile cap, the bottom box cofferdam is used to do the cushion cap.

The construction of the bridge is inseparable from the wisdom of engineers, who first measure the depth of the seabed. Then use the sinking column method to tie the steel bars and put them into the seabed before the construction can continue.

The bridge pier is a sub-structure that supports the bridge span structure and transmits the dead load and the live load of vehicles to the foundation, and the abutment is located on both sides of the bridge. The piers are between the two abutments. The piers are mainly composed of invisible pile foundation caps and piers and supports on the sea surface

1. Strong corrosiveness.

2. Seawater is different from freshwater, it is a very corrosive liquid. Seawater contains a large number of corrosive ions, such as sodium ions, chloride ions, sulfate ions, etc. They act on concrete structures and deteriorate the concrete on the surface.

Sulfate in seawater can even crystallize in concrete, and crystal growth can swell and crack the concrete, exposing the steel bar.

3. The steel itself is a very easy thing to corrode, once the protection of the concrete is lost, the water with ions and dissolved oxygen will contact the surface of the steel bar to form a galvanic cell, and the steel bar will quickly corrode or even break, and at this time, the whole structure will be broken. Of course, the difficulty of building a bridge at sea is too great, and some of the reasons that affect its difficulty are common, such as large span and high cost; In order to reduce the corrosion of seawater on the bridge body, the requirements for building materials are high, which leads to the selection and cost of building materials.

4. However, the influencing factors of construction in different regions are not the same, and the reasons for the difficulty of a certain offshore construction should generally be analyzed from the influence of natural factors and socio-economic factors. Climatic conditions affect the difficulty of construction; The cost of construction is high. At the same time, it is also necessary to analyze the reasons for the increase in construction difficulty in combination with the specific situation of the construction site.

The ocean is highly corrosive.

The reason why the construction of the bridge is very difficult is that the sea is highly corrosive. Bridges are subjected to the interaction of various corrosion factors in the marine environment, and even extreme weather such as typhoons and thunderstorms, which may damage the integrity and stability of the bridge structure. Therefore, bridge corrosion protection technology and corrosion protection management are extremely important for the construction of cross-sea bridges.

The sea-crossing bridge is a bridge that crosses the bay, strait, deep bucket sea, estuary or other marine waters, generally has a long span and route, the short is several thousand meters, and the length is tens of kilometers; Because the bridge is deeply rooted in the marine environment and the natural conditions are complex and harsh, the sea-crossing bridge can reflect the top technology of bridge engineering. Some sea-crossing bridges are relatively long and usually consist of multiple bridges within bridges; In order to avoid affecting the waterway or air route, a part of the sea-crossing bridge may also adopt an undersea tunnel project, which integrates the bridge, island and tunnel.

The longest sea-crossing bridge in China is the Hong Kong-Zhuhai-Macao Bridge. The total length of the bridge and tunnel is 55 kilometers, including the main bridge kilometer and the Hong Kong Port to Zhuhai-Macao Port kilometer. When completed, the Hong Kong-Zhuhai-Macao Bridge will not only be the longest sea-crossing bridge in China, but also the longest sea-crossing bridge in the world.

The Hong Kong-Zhuhai-Macao Bridge connects Hong Kong, Zhuhai and Macau, with the Hong Kong Special Administrative Region to the east and Zhuhai City and Macao Special Administrative Region of Guangdong Province to the west. It will strengthen the transportation links between Hong Kong and the west bank of the Pearl River, promote the economic development of the west bank of the Pearl River, and give full play to the advantages of Hong Kong and Macao. The bridge was jointly funded and built by ** and Guangdong, Hong Kong and Macao**, with a total cost of 126.9 billion yuan.