| Rapid development of the rail transit is the major strategic needs of our country. Rail transit is the most effective way to solve the transportation pressure with the advantages of large transport capacity and high speed etc. However, new problems have been caused by rail transit, stray current corrosion damage(SCCD) has a serious threat to the safety of critical infrastructure. Generation of the stray current(SC) in rail transit system and corrosion mechanism, numerical simulation method and experimental verification, and corrosion protection approaches for the reinforced concrete viaducts and buried metal pipeline are investigated in this dissertation. The major contents are as follows:The corrosion mechanism of SC was investigated,and pointed out that SCCD has strong, dynamic and local notable features. There are series of complex electrochemical corrosion process in electrolyte area around the cathode and anode after SC acting on, thus having a serious effect on the safe service of reinforced concrete viaducts and buried metal pipeline. Furthermore, equivalent circuit models to quantitatively analyze SC in viaduct and pipeline were proposed and given the values or calculation methods of parameters according to the applicable codes and standards. In addi tion, the simplified calculation model of single-span deck was given combining with practical engineering.A three-dimensional numerical simulation method of electric field distribution of SCCD was built by using the coupling of current interface in ACDC module and secondary current distribution interface in electrochemical corrosion module of COMSOL and combined with potentiodynamic polarization curve of reinforced. Through the systematic analysis of the relation between corrosion status of cathode and anode and voltage amplitude, founding that the SC couldn’t interfere the piers and substructures when the resistivity of insulated bearing between deck and piers is larger than 5 ? 105 Ω●m. Besides, the half-cell potential of reinforced surface shifted towards negative as cathode is in reasonable protection, less protection or over protection near the leak point of SC. And the half-cell potential shifted towards positive as a node is in accelerated corrosion near the return point of SC. Moreover, a reduced-scale viaduct model was built based on the numerical simulation model, the half-cell potential distribution situation of reinforced surface under a variety of conditions was tested and the results were compared with simulation results.The numerical simulation method of SC distribution in soil domain was built and a practical method to judge the minimum safe distance between buried metal pipeline and rail transit was presente d. Through the systematic analysis of buried metal pipeline with no coating, with local defects of coating, with perfect coating using the established numerical simulation method in combination with potentiodynamic polarization curve of metal pipeline. The corrosion rate(8.1200 mm/a) of pipeline with local defects of coating is larger than the pipeline’s with no coating(1.2858 mm/a) near the leak point when applied voltage is 10 V, and there is no SCCD interference on the pipeline with perfect coating. Mor eover, a reduced-scale buried metal pipeline model was built based on the numerical simulation model, the half-cell potential distribution situation of pipeline surface under a variety of conditions was tested and the results were compared with simulation results.The common measures of SCCD protection were summarized respectively from the source of SC leakage and structures level of the infrastrucures. Furthermore, quantitative analysis effect of the rail-earth transition resistance and rail longitudinal resistance on the SC combining with the practical engineering. Moreover, the basic frame and indicators of SCCD monitoring were suggested based on the built numerical simulation method. |
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