Impact of Marine Chloride Ion Erosion Environment on the Durability of Deep Sea Pile Foundation

Yan, Y.; Tian, T., and Wang, B., 2019. Impact of marine chloride ion erosion environment on the durability of deep sea pile foundation. In: Li, L.; Wan, X., and Huang, X. (eds.), Recent Developments in Practices and Research on Coastal Regions: Transportation, Environment and Economy. Journal of Coastal Research, Special Issue No. 98, pp. 6–9. Coconut Creek (Florida), ISSN 0749-0208.Subject to the chloride-induced corrosion, pipe pile foundations will suffer losses of the cross-sectional area of the steel bar, the bond strength between the steel bar and the concrete, as well as its bearing capacity. Even worse, it will malfunction. It is of great engineering significance to explore the corrosion initiation time and evaluate the service life of steel bars in pipe pile foundations under a marine environment. Based on Fick's law, this paper investigates the bilateral diffusion of chloride ions in pipe pile foundations in coastal areas and analyzes how the chloride ion diffusion effect is subjected to some key parameters such as bilateral erosion from chloride ions, mortar and concrete stratification, and temperature. In the end, the service life of prestressed high-strength concrete (PHC) pipe piles withstanding the bilateral diffusion of chloride ions is discussed. The findings show that when the temperature difference between the inner and outer walls of the pipe pile foundations is greater than 15°C, the wall temperature correction factor is quite different. It should be corrected according to the actual service conditions of the pipe pile foundations. Based on the hollow structure of PHC pipe piles, one should consider the simultaneous diffusion of chloride ions from the inner and outer walls and the centrifugal stratification of the pipe pile foundations when designing its service life. The mortar layer thickness and the ambient temperature are dominant factors that the service life of PHC pipe piles will be subject to. If the service year of the pipe pile foundation is 50 years, given the impact of the mortar layer, the thickness of the pipe pile foundation should be greater than 95 mm, and the mortar layer should be less than 10 mm; given the temperature effect, the pipe wall thickness should be greater than 100 mm. If the service year is 100 years, given the impact of the mortar layer, the wall thickness should be greater than 145 mm, and the mortar layer should be less than 25 mm; given the temperature effect, the wall thickness should be greater than 150 mm.