Expermental And Theoretical Studies On Chloride Diffusion Model Of Segment Of Shield Tunnel

Segment of shield tunnel has often been in underground corrosive environment and eroded by various ions in which chloride ions are the main factors to cause the corrosion damage of the reinforcement. In order to provide theoretical references for the rational design and scientific maintenance of China’s urban rail transit construction, the paper relying on the issues of the National Key Basic Research and Development Program(973:2011CB013802) has had a systematic study on the scientific issues that is chloride diffusion model of segment of shield tunnel on erosion environment, through the method of combining indoor artificial simulation test with theoretical analysis.The main contents have been included as follows:(1) The paper has designed the artificial environment simulation test, and considered that in the different chlorine salt erosion environment the chloride ion diffusion is affected by a variety of factors, also obtained the segment structure’s chloride ion concentration of the different positions and depths under the coupling effect of various factors. This thesis has analyzed the influence on the chloride ion concentration and diffusion coefficient made by solution concentration, load level and erosion time, also gained corresponding influence function.(2) Based on the impact of various factors made on the chloride ion diffusion mechanism,this paper has analyzed the shortcomings of the existing diffusion equation, and considering the diffusion coefficient together with the depth change, a multi-factor coupled chloride ion diffusion equation of segment of shield tunnel has been derived on the basis of the Fick’s second law.(3) According to the similarity of the chloride diffusion equation and the heat conduction equation, this paper has verified the correctness of the theoretical model and has done research on the influence of reinforcement spacing, diameter and thickness of the protective layer made on chloride ion diffusion by using thermal analysis module of ANSYS finite element software.