Steel pipe piles are widely used in building pile foundations, generally in the foundations of offshore buildings such as bridges and ports. However, with the continuous development of technology, they have gradually been used in the foundation process of high-rise buildings, transmission lines, etc. that require steel pile caps. However, with the continuous reduction of land resources, steel pipe piles are widely used in the single pile foundations of many power lines, especially for the promotion and use of wind power towers, which has become one of the most basic applications.
At present, many companies have adopted the method of single-tube landscape towers to use steel pipe pile single pile foundations. This method of use is not only safe and fast, but also can save a lot of costs. However, when it is used specifically, its anti-corrosion problem is one of the most urgent problems to be solved. This article further analyzes the principle of steel pipe column corrosion, explains the specific situation based on two specific steel pipe column application examples, and lists in detail the effective anti-corrosion methods for it, and uses it in actual projects, hoping to be of reference significance to relevant personnel.
In the field of communication towers, the large-scale use of steel pipe piles is a new type of foundation form, which can save a lot of manpower and material resources, and can also provide safe and fast protection. However, the foundation of the steel pipe pile is part of the facilities buried underground, so its anti-corrosion problem is one of the most urgent problems to be solved. Especially for those ports and offshore buildings, the erosion suffered by the foundation of the steel pipe pile is quite serious. Not only will it be corroded by seawater, but also by soil and microorganisms in the sea. It can be seen that the working environment of the steel pipe pile is quite harsh, and it will rust with water and oxygen in the environment. As for the corrosion rate, it depends on the amount of oxygen on the surface of the diffused steel per unit time. Therefore, the oxygen content of the steel pipe pile will mainly come from the concentration of oxygen in the water, flow rate and temperature. These problems should be considered in detail when applying anti-corrosion measures.
(I) Case 1 of steel pipe pile corrosion in transit soil
In 1958, Japan pulled out the Xinggu Bridge steel pipe pile that had been used for 17 years, and conducted a large-scale study on its corrosion morphology and degree. First, the attachments on its surface were observed with the naked eye to find the degree and specific morphology of its negative corrosion products; then, specific sampling tests were carried out. A detailed understanding of the specific corrosion amount of each part of the steel pipe is obtained. In addition to observation, it can be seen that the corrosion degree of some surface parts is relatively serious. For those parts with relatively small corrosion degree, interval sampling is adopted. And it is necessary to fully consider its specific changes in sampling, and the sample is placed in a diammonium citric acid aqueous solution for further immersion, and finally its specific dosage test can be obtained.
Through specific data, it can be known that the corrosion rate of steel pipe piles in the atmosphere or in the fourth layer, buried in silt no more than 2.5 meters deep, is quite fast. Secondly, the corrosion rate at its surface layer is significantly higher than that at a deeper level, especially for those parts in the silt and fine sand layer, which will be much greater than the parts in the fine sand layer; finally, although the corrosion rate has increased year by year, the ultimate corrosion resistance of this steel pipe is estimated by experts to be as long as 80 years.
(II) Corrosion of steel pipe piles in soil Case 2
Japan has also conducted a detailed corrosion investigation on the steel pipe piles of some buildings in use. For those steel pipe piles that have been used in the soil for 4 years, the land condition is negative three meters for fill, and below is silt. Three of the steel pipe piles were marked and the corrosion degree was tested. First, after removing the rust near the parts, ultrasonic testing was performed to further measure the wall thickness. It can be seen that there is uneven corrosion on the surface of the steel pipe pile. However, there is almost no corrosion inside. When the micrometer was used for measurement, it was found that the average annual corrosion rate was significantly reduced compared with the case 1.
When taking anti-corrosion measures for steel pipe piles, first of all, the corrosion resistance and acid oxidation degree of the soil where the steel piles are buried should be understood in detail. In addition, a comprehensive study should be conducted on bacterial corrosion, dissolved components and soil corrosion to obtain: except for soil with a particularly low pH value, the corrosion degree of steel pipe piles is quite small. Especially when the corrosion is located underwater, it has almost no great effect on the strength of some steel. It can be seen that the nature of the soil does not have a strong connection with the corrosion rate of the steel pipe.
Generally speaking, if there is no disturbance in the soil, the degree of corrosion of the steel pipe column is probably due to the sharp decrease in the amount of oxygen in the soil. This concept comes from a wide range of understanding and field corrosion surveys in the United States and Japan. And in many international advanced managements, most of them will have detailed restrictions on the specific corrosion amount of steel pipe piles in the fields of civil engineering, mountain management, and water management, and there are also specific regulations for their anti-corrosion methods.
Generally speaking, the methods adopted are: first, for steel pipe piles that have undergone corrosion resistance tests, the wall thickness is appropriately increased to continuously increase the anti-corrosion rate to extend their durability; secondly, for those steel pipe piles that do not undergo corrosion resistance tests, the wall thickness must be designed to increase by at least two millimeters. In the daily protection of steel pipe piles, a combination of coating and cathodic protection is generally adopted. The anti-corrosion materials produced in my country have very strong corrosion resistance, and effective cathodic protection measures are taken for the surface of steel. Its salt water resistance is extremely excellent. When combined with other materials, it can effectively play a role in the anti-corrosion of steel structures in the harbor. Moreover, due to the high solid content of the resin material, only one coat can achieve the characteristics of a thicker thickness, and it will also achieve the properties of no pinholes, anti-oxidation, low permeability to water vapor, etc.
In addition, it will have better insulation, good toughness, and wear resistance. These anti-corrosion primers have a good effect on the outer corrosion protection of steel pipe piles in coastal areas. The specific method is: first apply primer to the pile body, and then apply asphalt paint after two coats. After using this method, there has been no serious quality accident so far.
In addition, some areas also adopt the method of hot-dip galvanizing the steel pipe pile as a whole, and after spraying asphalt paint, use glass cloth to strengthen it.
(I) When the Dongjiazhuang base station in Shenzhen, Guangdong Province, China was built in 2014, the foundation design of steel pipe piles was adopted. In the process of selecting anti-corrosion materials, the overall hot-dip galvanizing method was first adopted, and the pile body was sprayed with epoxy resin asphalt paint, and finally strengthened with glass cloth. After the piling was completed, each base was subjected to a vertical compressive static load test, and the data was recorded in detail. After the normal installation, all indicators were qualified during the acceptance. After that, the steel pipe pile was inspected for three months, six months, and one year, and it was found that there was no obvious rust within a range of one meter below the ground. The ground at the top of the one-meter range was also encapsulated with concrete to further isolate the contact between air and water, greatly enhancing the anti-corrosion effect. The anti-corrosion effect is still very good to date, indicating that this method is quite feasible.
(II) During the pilot project of base stations in Hebei Province, China Tower Co., Ltd. adopted a steel pipe pile foundation when selecting a 45-meter-high single-tube internal flange tower. During the specific construction, by changing the original cast-in-place pile, the number of days for the foundation was greatly shortened, which not only saved a lot of costs, but also reduced the construction time, creating huge economic and social benefits for the company.
When taking anti-corrosion measures for steel pipe pile foundations in the field of communication towers, it is necessary to first effectively understand some basic experiences at home and abroad, and combine relevant regulations to produce anti-corrosion measures that meet local specific conditions. And for the foundation of information towers, strict implementation measures must be implemented according to specific engineering conditions. A series of methods should be carefully selected, and detailed acceptance should be carried out after construction. For subsequent inspections, protective measures should be taken before putting them into specific use. This can not only reduce a lot of construction costs for the company, but also ensure that there will be no repeated maintenance during use, greatly extending the service life of the communication tower.
At present, many companies have adopted the method of single-tube landscape towers to use steel pipe pile single pile foundations. This method of use is not only safe and fast, but also can save a lot of costs. However, when it is used specifically, its anti-corrosion problem is one of the most urgent problems to be solved. This article further analyzes the principle of steel pipe column corrosion, explains the specific situation based on two specific steel pipe column application examples, and lists in detail the effective anti-corrosion methods for it, and uses it in actual projects, hoping to be of reference significance to relevant personnel.
In the field of communication towers, the large-scale use of steel pipe piles is a new type of foundation form, which can save a lot of manpower and material resources, and can also provide safe and fast protection. However, the foundation of the steel pipe pile is part of the facilities buried underground, so its anti-corrosion problem is one of the most urgent problems to be solved. Especially for those ports and offshore buildings, the erosion suffered by the foundation of the steel pipe pile is quite serious. Not only will it be corroded by seawater, but also by soil and microorganisms in the sea. It can be seen that the working environment of the steel pipe pile is quite harsh, and it will rust with water and oxygen in the environment. As for the corrosion rate, it depends on the amount of oxygen on the surface of the diffused steel per unit time. Therefore, the oxygen content of the steel pipe pile will mainly come from the concentration of oxygen in the water, flow rate and temperature. These problems should be considered in detail when applying anti-corrosion measures.
1. Steel pipe pile corrosion case
(I) Case 1 of steel pipe pile corrosion in transit soilIn 1958, Japan pulled out the Xinggu Bridge steel pipe pile that had been used for 17 years, and conducted a large-scale study on its corrosion morphology and degree. First, the attachments on its surface were observed with the naked eye to find the degree and specific morphology of its negative corrosion products; then, specific sampling tests were carried out. A detailed understanding of the specific corrosion amount of each part of the steel pipe is obtained. In addition to observation, it can be seen that the corrosion degree of some surface parts is relatively serious. For those parts with relatively small corrosion degree, interval sampling is adopted. And it is necessary to fully consider its specific changes in sampling, and the sample is placed in a diammonium citric acid aqueous solution for further immersion, and finally its specific dosage test can be obtained.
Through specific data, it can be known that the corrosion rate of steel pipe piles in the atmosphere or in the fourth layer, buried in silt no more than 2.5 meters deep, is quite fast. Secondly, the corrosion rate at its surface layer is significantly higher than that at a deeper level, especially for those parts in the silt and fine sand layer, which will be much greater than the parts in the fine sand layer; finally, although the corrosion rate has increased year by year, the ultimate corrosion resistance of this steel pipe is estimated by experts to be as long as 80 years.
(II) Corrosion of steel pipe piles in soil Case 2
Japan has also conducted a detailed corrosion investigation on the steel pipe piles of some buildings in use. For those steel pipe piles that have been used in the soil for 4 years, the land condition is negative three meters for fill, and below is silt. Three of the steel pipe piles were marked and the corrosion degree was tested. First, after removing the rust near the parts, ultrasonic testing was performed to further measure the wall thickness. It can be seen that there is uneven corrosion on the surface of the steel pipe pile. However, there is almost no corrosion inside. When the micrometer was used for measurement, it was found that the average annual corrosion rate was significantly reduced compared with the case 1.
2. Protection methods for steel pipe piles
When taking anti-corrosion measures for steel pipe piles, first of all, the corrosion resistance and acid oxidation degree of the soil where the steel piles are buried should be understood in detail. In addition, a comprehensive study should be conducted on bacterial corrosion, dissolved components and soil corrosion to obtain: except for soil with a particularly low pH value, the corrosion degree of steel pipe piles is quite small. Especially when the corrosion is located underwater, it has almost no great effect on the strength of some steel. It can be seen that the nature of the soil does not have a strong connection with the corrosion rate of the steel pipe.Generally speaking, if there is no disturbance in the soil, the degree of corrosion of the steel pipe column is probably due to the sharp decrease in the amount of oxygen in the soil. This concept comes from a wide range of understanding and field corrosion surveys in the United States and Japan. And in many international advanced managements, most of them will have detailed restrictions on the specific corrosion amount of steel pipe piles in the fields of civil engineering, mountain management, and water management, and there are also specific regulations for their anti-corrosion methods.
Generally speaking, the methods adopted are: first, for steel pipe piles that have undergone corrosion resistance tests, the wall thickness is appropriately increased to continuously increase the anti-corrosion rate to extend their durability; secondly, for those steel pipe piles that do not undergo corrosion resistance tests, the wall thickness must be designed to increase by at least two millimeters. In the daily protection of steel pipe piles, a combination of coating and cathodic protection is generally adopted. The anti-corrosion materials produced in my country have very strong corrosion resistance, and effective cathodic protection measures are taken for the surface of steel. Its salt water resistance is extremely excellent. When combined with other materials, it can effectively play a role in the anti-corrosion of steel structures in the harbor. Moreover, due to the high solid content of the resin material, only one coat can achieve the characteristics of a thicker thickness, and it will also achieve the properties of no pinholes, anti-oxidation, low permeability to water vapor, etc.
In addition, it will have better insulation, good toughness, and wear resistance. These anti-corrosion primers have a good effect on the outer corrosion protection of steel pipe piles in coastal areas. The specific method is: first apply primer to the pile body, and then apply asphalt paint after two coats. After using this method, there has been no serious quality accident so far.
In addition, some areas also adopt the method of hot-dip galvanizing the steel pipe pile as a whole, and after spraying asphalt paint, use glass cloth to strengthen it.
3. Use cases of steel pipe piles
(I) When the Dongjiazhuang base station in Shenzhen, Guangdong Province, China was built in 2014, the foundation design of steel pipe piles was adopted. In the process of selecting anti-corrosion materials, the overall hot-dip galvanizing method was first adopted, and the pile body was sprayed with epoxy resin asphalt paint, and finally strengthened with glass cloth. After the piling was completed, each base was subjected to a vertical compressive static load test, and the data was recorded in detail. After the normal installation, all indicators were qualified during the acceptance. After that, the steel pipe pile was inspected for three months, six months, and one year, and it was found that there was no obvious rust within a range of one meter below the ground. The ground at the top of the one-meter range was also encapsulated with concrete to further isolate the contact between air and water, greatly enhancing the anti-corrosion effect. The anti-corrosion effect is still very good to date, indicating that this method is quite feasible.(II) During the pilot project of base stations in Hebei Province, China Tower Co., Ltd. adopted a steel pipe pile foundation when selecting a 45-meter-high single-tube internal flange tower. During the specific construction, by changing the original cast-in-place pile, the number of days for the foundation was greatly shortened, which not only saved a lot of costs, but also reduced the construction time, creating huge economic and social benefits for the company.
When taking anti-corrosion measures for steel pipe pile foundations in the field of communication towers, it is necessary to first effectively understand some basic experiences at home and abroad, and combine relevant regulations to produce anti-corrosion measures that meet local specific conditions. And for the foundation of information towers, strict implementation measures must be implemented according to specific engineering conditions. A series of methods should be carefully selected, and detailed acceptance should be carried out after construction. For subsequent inspections, protective measures should be taken before putting them into specific use. This can not only reduce a lot of construction costs for the company, but also ensure that there will be no repeated maintenance during use, greatly extending the service life of the communication tower.
