On October 23, the world's longest cross-sea bridge Hong Kong-Zhuhai-Macao Bridge opened to traffic. In addition to being the world's longest bridge, the design standards of the Hong Kong-Zhuhai-Macao Bridge have broken the usual "hundred-year-old practice" in China, and formulated a 120-year design standard. Among them, the "SEBF / SLF high-performance coating plus sacrificial anode" joint protection technology independently developed by the Institute of Metal Research of the Chinese Academy of Sciences has played an important role.
Researcher Li Jing, head of the durability protection and engineering group of the Institute of Metals, Chinese Academy of Sciences, told reporters: "We have completed the design of the protective coating process for the steel pipe composite pile of the bridge foundation, the design of the cathodic protection system, and the design of the in-situ corrosion monitoring system. A new generation of high-performance epoxy-coated steel bars 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. "
The research on the durability protection and engineering of the Institute of Metals of the Chinese Academy of Sciences began in the 1990s. For more than 20 years, it has carried out research and development and production of heavy anticorrosive coating technology foundations and applications, and developed SEBF melt-bonded epoxy powder coatings and SLF high Molecular composite coatings, with an annual production scale of up to 1,000 tons. The first domestic fully automatic internal and external coating production line for 10,000-ton buried pipes and small and medium-sized coating production lines have been successfully designed in the country. Eight installations have been installed in the country; fast curing, conventional Three types of coating processes: thermal curing and room temperature curing; presided over the compilation of national standards for "corrosion-resistant coatings for fusion-bonded epoxy powder coatings" and "corrosion-resistant coatings for solvent-free epoxy liquid coatings"; "Corrosion Design and Construction" National Architectural Standard Design Atlas, more than 50 patents were obtained.
This technological achievement has been used in the seawater cooling circuit system of the Qinshan Nuclear Power Plant, the natural gas pipeline elbow for the National West-East Gas Pipeline Project, the steel pipe pile of the Hangzhou Bay Cross-sea Bridge, the steel pipe pile of the Zhoushan Liandao Jintang Bridge, and the Qingcaosha of Shanghai It plays an irreplaceable role in major basic anti-corrosion projects such as the water source raw water project and the water conveyance project.
Although it has withstood the test of many large-scale projects in China, according to the design requirements of 120 years, the original durability design scheme of the cross-sea bridge has not been able to meet the demand, which has brought new challenges to the researchers of the Institute of Metals of the Chinese Academy of Sciences.
The foundation protection project of the Hong Kong-Zhuhai-Macao Bridge is mainly for the anticorrosive construction of steel pipe composite piles. The steel pipe piles are located in the sea mud environment. The damage of the anticorrosive coating mainly comes from mechanical damage during pile driving, sand and gravel grinding scratches, and Long-term erosion and degradation of corrosion factors under the mud.
Li Jing told reporters that in view of the specific sea mud environment of the Hong Kong-Zhuhai-Macao Bridge, the research team has carried out research and development of relevant coatings since the demonstration of the bridge, and has successively evaluated key performance indicators such as the anti-penetration and cathodic peel resistance of the coating. Began to develop new coatings to solve the problem of coating durability. By adjusting the coating formula and improving the coating process, scientific researchers have reduced the water absorption and dissolution rate of the coating, effectively improved the anti-penetration ability of the coating, and enhanced the bonding strength of the coating to the metal.
The 120-year durability design requirements are far from being able to rely solely on the coating's anti-corrosion protection methods, 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, moving its potential to the negative direction, reaching a corrosion-free potential, and putting the metal structure in a protected state.
In the past, the cathodic protection of cross-sea bridges in China focused on steel pipe piles immersed in seawater, and most of the steel pipe composite piles of Hong Kong-Zhuhai-Macao Bridge were located in the sea mud under the concrete platform. There is no precedent for how to implement cathodic protection.
In response to the corrosion environment and structural characteristics, researchers from the Institute of Metal Research of the Chinese Academy of Sciences focused on the problems faced by cathodic protection of steel pipe composite piles after they were poured into different geological layers, and adopted ingenious methods to select the extreme boundary parameters to estimate the protection effect, that is, calculate the soil resistivity. Whether the potential of cathodic protection can meet the protection requirements under the maximum and minimum conditions, and this is used as a means of similar engineering cathodic protection design, which effectively solves the problem of cathodic protection design in complex environments.
In order to verify the feasibility of the cathodic protection design of steel pipe composite piles, the researchers carried out simulation experiments according to the ratio of 1:20, and simulated the geological environment of the steel pipe composite piles of the Hong Kong-Zhuhai-Macao Bridge as much as possible. Reduced-scale model experiments prove that the design calculation method is correct and feasible. Subsequently, a full-scale structural test of the 1: 1 project was carried out at the Hong Kong-Zhuhai-Macao Bridge site. The results show that the installation of highly efficient sacrificial aluminum anodes in seawater can fully protect the sea mud. Steel pipe piles, a new type of cathodic protection method, can meet the protection requirements of bridge foundations.
In order to convince users that cathodic protection can indeed protect the foundation steel pipe composite piles under the sea mud, after the simulation experiments, the researchers adopted the method of installing protective facilities monitoring probes on the inner wall of the steel pipe, and the probes were piled into the sea mud nearly 100 meters to implement the original Position monitoring effectively solves the problem of difficult installation of detection equipment under the sea mud. It is the first time to install detection equipment in this way in the global marine engineering community.
The concrete used for the foundation pier of the Hong Kong-Zhuhai-Macao Bridge is marine concrete. In addition to meeting the design and construction requirements, it has higher requirements in terms of impermeability, corrosion resistance, prevention of corrosion of steel bars, and resistance to construction impact. To this end, researchers from the Institute of Metal Research of the Chinese Academy of Sciences have developed a high-performance coated rebar technology. Demand for Zhu-Ao Bridge Project. 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 Chinese Academy of Sciences Metals. The steel bars in the concrete are not corroded, and the strength of the concrete is guaranteed. It is the application of the above-mentioned comprehensive technology that has enabled the Hong Kong-Zhuhai-Macao Bridge to reach a life span of 120 years.