13, the world's largest bored pile, the 6.3-meter super-large diameter bored pile, made its debut in the No.5 main tower pier of Xihoumen Rail-cum-Road Bridge, which not only achieved a major breakthrough in the construction of super-large diameter bored piles in China from 0 to 1, but also filled in the construction technology of deep-water super-large diameter bored piles in China. It also fired the first shot to overcome the difficulties of bridge deep-water foundation technology in the complex marine environment above 60 meters of water depth, and promoted the whole industry chain of "China Bridge" to take a solid step in the field of deep-sea environment with greater water depth. At the construction
site of the
bridge, the construction of the bridge has crossed the highest peak
of the construction difficulty of the whole bridge. Xihoumen Rail-cum-Road Bridge is the key control project of Yongzhou Railway, and the foundation construction of No.5 main tower is the key control process of the whole bridge construction. It can be said that the construction of "6.3-meter super-large diameter bored pile" of No.5 main tower pier is the most important and difficult part in the construction process of Yongzhou Railway. The success of the first show will provide important guidance and valuable experience for the construction of the remaining 17 '6.3-meter super-large diameter bored piles' of the bridge. Xiao Haizhu, chief engineer of China Railway Bridge Institute Group and chief designer of Xihoumen Highway and Railway Bridge, said. Technical difficulties
of
"6.3m super-large diameter bored pile" 1
. The construction conditions are harsh, such as strong wind, deep water, Rapids, bare rock, inclined rock surface, and it is difficult to bury the steel casing of pile foundation. The second
difficulty is that the geological conditions are complex, the bedrock is broken, the hardness is uneven, and the pile foundation is difficult to form holes. The third
difficulty is that the single pile area is large, and it is not easy to control the pile quality of the conventional single pipe pouring pile body concrete. The fourth
difficulty is that the hydration heat effect of pile body concrete is obvious, which is easy to cause cracking of pile body concrete. The fifth
difficulty is that the single pile area is large, the conventional acoustic tube layout is difficult to cover the whole section of the pile body, and the detection path is too long to ensure the accuracy of the detection results.
Difficulty 6
The diameter of the pile body is large, the problem of collision between the pile foundation and the steel bar of the bearing platform is prominent, and the site construction is difficult. The purpose of the first concrete pouring
of the 6.3m super-
large diameter pile foundation site is to solve practical problems-only around the concrete pouring of the "6.3m super-large diameter bored pile". The construction of the bridge also "carelessly" created six "firsts" by the way:
①
For the first time, the process of "hammering initial stabilization + graded drilling + graded hammering follow-up" was adopted in the process of embedding the steel casing and the final stabilization was achieved.
(2)
Drive the innovation chain of the industrial chain, and jointly develop the super rotary drill and super rotary drill matching the "6.3m super-large diameter bored pile" for the first time, so as to solve the problem of super-large diameter pile foundation.
(3)
It is the first time to adopt the technology of synchronous pouring of pile body concrete with multiple ducts, which successfully solves the problem of pouring of super-large diameter bored pile concrete.
(4)
It is the first time to study and put forward the hydration heat control technology of super-large diameter pile foundation by burying steel pipe in the center of pile and adopting water circulation, which effectively reduces the adverse effects of hydration heat effect of pile foundation.
(5)
It is the first time to invent a method for detecting the quality of super-large diameter pile foundation by arranging acoustic pipes in layers and carrying out ultrasonic detection in different areas, so as to ensure the accuracy and reliability of the detection results.
⑥
It is the first time to adopt the anti-collision design of pile body and bearing platform reinforcement, which eliminates the collision problem between pile foundation and bearing platform reinforcement and reduces the difficulty of site construction. The three-dimensional
design of
pile foundation is the soul of the project, and the construction is the flesh and blood of the project.
In order to ensure the success of the first show of "6.3m super-large diameter bored pile", the designers of China Railway Bridge Institute and the construction personnel of the project team of China Railway Bridge Bureau carried out 1:1 prototype process test for each construction link, including land test pile and underwater test pile. In addition to the design itself, how about the related construction equipment? How about the construction environment and conditions? Can design be consistent with the construction? Can design guarantee the construction safety and quality? Can we speed up the construction progress by optimizing the design? All of them are stuffed into the brains of designers, and they are constantly combined and optimized.
Just as the builders were overcoming difficulties for the first show of "6.3-meter super-large diameter bored piles", Typhoon No.5 "Du Suri" and Typhoon No.6 "Kanu" fired fiercely at the coastal areas of China one after another, resulting in the suspension of offshore operations for more than 10 days.
As for the "platform" of the bridge itself, the design team has already considered it thoroughly in the early stage of the design. For example, the foundation of No.5 main tower adopts streamlined bearing platform, and the main beam adopts streamlined three-box structure, which can withstand typhoons above 17 levels.
For the "anti-Taiwan" in the construction process, designers dare not relax their vigilance at all. In addition to the design representative who must be stationed 24 hours a day to give guidance and precautions for "anti-typhoon" in real time, it is also necessary to sort out and analyze the construction processes, possible problems or potential safety and quality hazards one by one after the typhoon, so as to ensure the safety of personnel, structure and construction equipment.
Designers are well aware that, regardless of the size of the project or the difficulty of the node, only with the awe of "nothing lost" can they harvest the joy of "nothing lost".
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