Fuxia High-speed Rail Quanzhou Bay Bridge successfully closed and won many world tops in innovative technology
China's high-speed rail enters the cross-sea era
Our reporter Wang Yajing, correspondent She Pengye
In August, the sea breeze gusts in Quanzhou Bay, Fujian Province.
In the blue sea, a silver-white bridge winds its way from northeast to southwest.
On the wide bridge, my country's first cross-sea high-speed railway-Fuxia High-speed Railway has entered the final stage of construction.
On August 6, as the last steel box girder slowly dropped, my country’s first cross-sea high-speed rail bridge, the main bridge of the Fuzhou-Xiamen (Men) high-speed rail Quanzhou Bay Cross-sea Bridge, was successfully closed. Traveling only on land has entered a new era in which it can travel across seas.
"Across the mountains, over the plains, and across the rushing Yellow River and the Yangtze River." This is a lyric from the song "Singing the Motherland", which seems very suitable for the development of China's high-speed rail.
According to incomplete statistics, as of the end of 2020, my country's high-speed rail operating mileage has increased to 37,900 kilometers. Whether it is a high-cold plateau or a stormy bay, it has failed to stop the pace of China's high-speed rail.
Among them, the high-speed rail bridge is 18,000 kilometers long, ranking first in the world, and even many large railway stations are built on viaducts.
The high-speed rail crossing the sea relies on advanced bridge construction technology.
Among many bridges, railway bridges have extremely high requirements for road conditions and higher requirements for bridge building technology.
However, China Bridge dared to challenge high difficulty.
This time, the Fuzhou-Xiamen High Speed Rail Quanzhou Bay Cross-sea Bridge is not only the first cross-sea high-speed railway bridge in China, but also the world’s first long-span cross-sea cable-stayed railway bridge with a traveling speed of more than 300 km/h. Behind this super project, It is supported by a series of advanced technologies.
1 The train is speeding across the bridge in 90 seconds and there is no speed limit with 8 strong winds
The chief designer of the Quanzhou Bay Cross-sea Bridge of the Fuxia High-speed Rail-Yan Aiguo, the chief engineer of the Bridge Institute of China Railway Construction Fourth Survey and Design Institute Group Co., Ltd. The length of the bridge is 800 kilometers.
Looking back at the bridge construction process on this road, Yan Aiguo felt the deepest, and it was the rapid increase in the passage speed of domestic bridges over the years.
"What is the biggest feature of high-speed rail? It is fast. This speed of traffic requires the road facilities and conditions of the high-speed rail bridge to ensure it."
Yan Aiguo introduced that the early railway arch bridges in my country could only run 160 kilometers per hour.
The Pingtan Strait Road-Rail Bridge, my country’s first road-rail dual-use bridge in the true sense, can only travel at a speed of 200 kilometers per hour.
However, the design speed of the Quanzhou Bay Cross-sea Bridge on the Fuxia High-speed Rail reached 350 kilometers per hour.
This increase in speed stems from the technological innovation of bridge structures and pavements.
"The cross-sea high-speed rail bridge must ensure a large span. Generally, cable-stayed bridges are used. This structure is easy to deform. At the same time, Quanzhou Bay is located in the coastal high wind speed belt, where the sea is windy and the sea breeze will produce impact. It is necessary to innovate the structure to ensure the rigidity of the road surface. , Otherwise the bridge will cause serious lateral shaking and vortex vibration due to wind.” Zeng Jiahua, the design leader of the Tie Siyuan Bridge, said that high-speed railways have high requirements for bridge stiffness and later linear stability. For the cable-stayed bridge, a steel-concrete composite beam composed of concrete decks and channel-shaped steel beams was used for the first time. The steel beams have light weight and meet the weight requirements of long-span bridge construction; while concrete effectively improves the rigidity of the bridge.
In addition, the main girder of the bridge adopts a streamlined box structure with effective aerodynamic measures such as baffles, vibration damping railings, cable eddy current dampers, etc., which reduces wind-induced vibration in complex wind environments and avoids abnormal vortex vibrations. .
These designs allow the train to pass through the cross-sea bridge at a speed of 350 kilometers per hour in a level 8 wind without wind barriers and other wind protection measures, and will not be closed to traffic under a level 11 storm.
The track is another reason for the high speed per hour of the Quanzhou Bay Cross-sea Bridge of the Fuxia High-speed Railway.
Anyone who has ever taken a train has seen that underneath the rails are usually gravel beds. The maximum operating speed of this ballasted track is only 250 kilometers.
The ballastless track is a track structure with a whole foundation such as concrete and asphalt mixture, which has a higher speed per hour.
However, compared to land, laying ballastless tracks on long-span bridges and passing high-speed railways requires extremely high structural rigidity and creep deformation of the bridge.
There is no precedent abroad for laying ballastless tracks on such a large-span sea-crossing bridge.
According to Liu Fuxing, the person in charge of the Fuxia Railway Project of the Second Aviation Administration of China Communications, the approach bridge of the Quanzhou Bay Sea-crossing Bridge adopts double-block ballastless tracks, and the main navigation channel uses a polyurethane cured track bed structure for the first time on cable-stayed bridges at home and abroad. "The ballast has the effect of making the ballasted track run out of the ballastless track.
It is these measures that enable the Fuxia High-speed Rail Quanzhou Bay Cross-sea Bridge to realize the "speedy speed" of the high-speed rail crossing the bridge in 90 seconds.
2 The accuracy deviation of the closing accuracy of the operation in the 7th level of strong wind is only 1 mm
Building bridges across the sea is also an engineering problem in the world.
One of the reasons is that the span across the sea is often longer than that across rivers or rivers.
Yan Aiguo said: "The speed of my country's high-speed rail development over the past few years is amazing. When I first worked in the 1990s, most of the railway bridges I designed had a span of 32 meters, and the maximum was no more than 100 meters. The structure was mostly concrete with a small amount of steel. Nowadays, there are various types of bridges. High-speed rail bridges are getting longer and longer, spans are getting bigger and bigger, and their structures are getting more and more diverse."
Technological innovation is the password behind the success of the Changhong Transverse Railway Bridge in China.
The Pingtan Strait Rail-Road Bridge is currently the longest cross-sea road-rail bridge in the world.
The channel bridge with the largest span of the bridge, Yuanhong Channel Bridge, has a main span of 532 meters, and two 50,000-ton ships can pass under the bridge side by side without any problem.
The main span of the Quanzhou Bay Bridge on the Fuxia High-speed Railway also reached 400 meters.
How was the long-span bridge built?
"Like building blocks, it must be refined." According to Weng Fangwen, chief engineer of the Fuxia Railway Project of the China Communications Second Aviation Administration, as a key control project for the entire Fuxia high-speed rail line, the main girder of the Quanzhou Bay Cross-sea Bridge uses steel boxes. The beam form is divided into 77 sections, of which the heaviest beam section amounts to 365.18 tons.
During the hoisting, in order to effectively cope with the problems of heavy lifting weight, high positioning accuracy requirements, and complicated offshore construction environment, the team adopted the overall construction technology of sectioned cantilever hoisting of the main beams, with the side spans first and the middle spans closed.
Among them, the mid-span closing adopts the "active" closing method of hoisting on the north side and pushing on the south side.
In order to ensure that each piece is tightly closed, Weng Fangwen and his colleagues have developed and applied a set of intelligent monitoring and control system for the closure of the joint, using intelligent equipment such as level gauges and inclinometers to conduct advanced intelligent monitoring of the state of the closure of the joint. Ultra-high precision with a height difference of 0.5mm.
Xiang Haifan, an academician of the Chinese Academy of Engineering, said that since the reform and opening up, we have not only made new breakthroughs in bridge construction technology, but also have advantages in the speed of bridge construction.
We built the bridge in 3 years, and it will take at least 5 to 7 years or even longer abroad.
Such high efficiency is inseparable from the infrastructure weapon designed and developed by Chinese engineers.
For example, the world's first thousand-ton bridge erecting machine, the "Kunlun" thousand-ton transport and erection integrated machine, was unveiled during the construction of the Fu-Xia high-speed rail.
What is the power of "Kunlun"?
In tunnel operation, the traditional bridge erecting machine needs to be disassembled and assembled before passing through the tunnel. However, the "Kunlun" bridge erecting machine can directly pass through the tunnel, saving time to complete the 400-meter-long bridge erection .
In addition, the "Kunlun" is not afraid of strong winds and waves on the sea, and its organization remains stable even in strong winds of magnitude 7.
In addition, it can also be compatible with box girder of different lengths. It can use a robotic arm to hoist a box girder weighing up to 4 aeroplanes, span the gap between the piers, and quickly and accurately place the box girder on the required position. .
During the previous construction of the Pingtan Strait Highway and Railway Bridge, facing the “world-class tuyere” known as the “bridge construction restricted area” Pingtan Strait, the construction party independently developed the world’s most advanced KTY5000 hydraulic power head drilling rig and Heavyweight equipment such as the double-boom crane ship with the largest lifting capacity and the highest lifting height in China has successfully solved the problem of bridge building under harsh and complicated marine environmental conditions.
3 The technology of corrosion-resistant and weather-resistant steel for a hundred years without painting is in the forefront of the world
Compared with ordinary bridges, cross-sea bridges also face another test, that is, sea breeze and sea water corrosion.
The anti-corrosion standard of high-speed railway engineering structure is 100-year anti-corrosion.
"In coastal areas with high salt and high humidity, it is difficult to achieve this standard by relying on the traditional anti-corrosion method of painting the surface of steel beams." Weng Fangwen said. The steel anchor beams and bearings of the pylons of the bridge are made of a new type of weathering steel independently researched and developed in China. It is the world's first large-scale sea-crossing project with coating-free weathering steel.
The weathering steel in Weng Fangwen’s mouth is one of the world’s leading-edge steel grades of super steel technology. By adding trace nickel to the steel, the steel itself generates a dense and stable passivation rust layer to prevent the penetration of chloride ions in the seawater. The long-lasting anti-corrosion effect of "rust with rust".
It is understood that the main bridge of Quanzhou Bay Bridge has 60 sets of steel anchor beams, all of which are made of nickel-based marine atmospheric corrosion-resistant steel.
In addition, the relevant team has also developed high-strength bolts and welding materials that are matched with this steel, and successfully made the steel into the steel anchor beam required for the bridge.
It is precisely because of such steel anchor beams that the Fuxia High-speed Rail Quanzhou Bay Cross-sea Bridge not only realizes painting-free, but also does not need to set up a dehumidification system.
The reporter learned that this kind of weathering steel is also used in some large-span bridges on the Sichuan-Tibet Railway, such as the Yarlung Zangbo River Bridge.
In fact, with the development of my country's bridge construction technology, a variety of high-quality and efficient new materials have continuously emerged in construction materials, and the localization rate of materials has also been increasing.
The kilometer-level high-speed rail cable-stayed bridge opened to traffic in July 2020, the Shanghai-Sutong Yangtze River Highway Bridge, uses a high-performance new material independently developed by my country-a zinc-aluminum coating with a tensile strength of up to 2000 MPa. Steel wire.
The entire bridge has 72 pairs of stay cables, all made of this kind of steel wire.
Although the diameter of each steel wire is only 7 mm, it can withstand 80 tons of pulling force, reaching the international advanced level.
Since the Shanghai-Sutong Yangtze River Highway and Railway Bridge is the first use of this material, considering that this high-performance material will be widely used in the bridge industry in the future, the state has issued the "Wire Rope for Suspension Bridge Sling" standard in 2020.
The relevant person in charge of the China Railway Bridge Bureau who participated in the drafting of the standards stated: "Previously, foreign standards were much higher than those in China. Most of our projects abroad were constructed and accepted in accordance with European and American standards. In recent years, with the continuous breakthroughs in Chinese material technology Some standards are already in the forefront of the world. The release and implementation of the national standard highlights the technical gold content of China’s new materials, which will further promote the technological progress of China’s long-span suspension bridge construction and promote China’s new materials and infrastructure construction to "go global". positive effects."
Graphene coatings, nano-coatings...These new materials "made in China" have also been increasingly used in bridge construction in recent years.
Xue Qunji, academician of the Chinese Academy of Engineering and director of the Science and Technology Committee of the Ningbo Institute of Materials of the Chinese Academy of Sciences, said: “In recent years, we have conducted very good research on the corrosion protection technology of marine materials. Used on the bridge. The graphene-containing anti-corrosion coating we have studied is also the first internationally."