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Hong Kong-Zhuhai-Macao Bridge Has A Design Life Of 120 Years. Special Steel And Aluminum Are Used.
Nov 04, 2018

On October 23, the opening ceremony of the Hong Kong-Zhuhai-Macao Bridge was held. In addition to being the world's long bridge across the sea, the design standards of the Hong Kong-Zhuhai-Macao Bridge have broken the usual “hundred-year practice” and set a 120-year design standard. Among them, the "SEBF/SLF high-performance coating plus sacrificial anode" joint protection technology independently researched and developed by the Institute of Metal Research of the Chinese Academy of Sciences is indispensable.


Researcher Li Jing, the head of the Durability Protection and Engineering Research Group of the Institute of Metals of the Chinese Academy of Sciences, told the author: "We have completed the process design of the protective coating for the composite steel pipe composite foundation, the design of the cathodic protection system, the design of the in-situ corrosion monitoring system, etc. A new generation of high-performance epoxy-coated steel reinforcement for the concrete structure of the bridge, and participating in the anti-corrosion coating construction of the bridge foundation, ensuring the 120-year durability design requirements of the Hong Kong-Zhuhai-Macao Bridge foundation."


Challenge 120 years of durability design


The durability protection and engineering research of the Institute of Metals of the Chinese Academy of Sciences began in the 1990s. In the past 20 years, it has obtained more than 50 patents. However, for the design requirements of 120 years, the original design of the durability of the cross-sea bridge has been unable to meet the demand. This poses new challenges for researchers at the Institute of Metals of the Chinese Academy of Sciences.


Li Jing introduced that in response to the specific sea mud environment of the Hong Kong-Zhuhai-Macao Bridge, the research team started the research and development of related coatings from the time of the bridge demonstration, and successively made key performance indicators such as permeability resistance and cathodic disbondability of the coating. Start with the development of new coatings to address the durability of coatings. By adjusting the coating formulation and improving the coating process, the researchers reduced the water absorption and dissolution rate of the coating, effectively improved the penetration resistance of the coating and enhanced the bond strength between the coating and the metal.

Effectively solve protection problems in complex environments


The 120-year durability design requirement is far from being achieved by the protective means of coating corrosion protection and must be used in conjunction with cathodic protection technology. Cathodic protection technology refers to the electrochemical method of polarizing the metal structure to be protected, causing the potential to move in a negative direction to achieve a corrosion-free potential, so that the metal structure is in a protected state.


According to reports, in the past, the cathodic protection of China's cross-sea bridge was focused on steel pipe piles immersed in seawater, and most of the steel pipe composite piles of Hong Kong-Zhuhai-Macao Bridge are located in the sea mud under the concrete cap. There is no precedent for how to implement cathodic protection. Jian.


In response to the corrosive environment and structural characteristics, the scientific research personnel of the Institute of Metals of the Chinese Academy of Sciences focused on the problems of cathodic protection of steel pipe composite piles after being poured into different geological layers. The ingenious method was adopted to select the extreme boundary parameters to calculate the protection effect, that is, calculate the soil resistivity. Whether the potential of cathodic protection can meet the protection requirements in the two cases of zui big and zui small, and as a means of similar engineering cathodic protection design, effectively solve the cathodic protection design problem in complex environment.


The world's ocean engineering community is still the first


In order to verify the feasibility of the cathodic protection design of the steel pipe composite pile, the researchers carried out the simulation experiment according to the ratio of 1:20, and simulated the geological environment of the steel pipe composite pile crossing of the Hong Kong-Zhuhai-Macao Bridge as much as possible. The scaled model experiment proves that the design calculation method is correct and feasible, and then the 1:1 full-scale structural test is carried out on the site of the Hong Kong-Zhuhai-Macao Bridge. The results show that the installation of high-efficiency sacrificial aluminum anode in seawater can fully protect the sea mud. Steel pipe piles, ie new cathodic protection methods, can meet the protection requirements of the foundation of the bridge.


In order to convince the user that the cathodic protection can protect the basic steel pipe composite pile under the sea mud, after the simulation experiment, the scientific researcher adopts the method of monitoring the probe with the inner wall of the steel pipe, and the probe is carried out with the piling deep into the sea mud nearly 100 meters. The position monitoring effectively solves the problem of installing the detection equipment under the sea mud. It is the first time in the global ocean engineering community to install detection equipment in this way.


Develop high performance coated steel bar technology


The concrete used in the foundation pier of the Hong Kong-Zhuhai-Macao Bridge is a marine concrete. In addition to meeting the design and construction requirements, it has higher requirements in terms of impermeability, corrosion resistance, prevention of steel corrosion and resistance to construction impact. To this end, the scientific research personnel of the Institute of Metals of the Chinese Academy of Sciences have developed a high-performance coated steel bar technology. Experts believe that its technical performance exceeds the technical indicators of relevant domestic and foreign coated steel bars, and it is at the international leading level among similar products, which can meet the port. Zhuhai-Australian Bridge project needs. The design and construction process of the Hong Kong-Zhuhai-Macao Bridge has adopted the high-performance coated steel bar technology and standards developed by the Institute of Metals of the Chinese Academy of Sciences. The steel in the concrete is not corroded and the strength of the concrete is guaranteed. It is the application of the above comprehensive technology that enabled the Hong Kong-Zhuhai-Macao Bridge to meet the 120-year design standard.