| With the development of rail traffic system in city, an increasing strictness of problem with metro stray current corrosion induced by the power supply in a fashion of direct traction current and rail circumfluence has caused widespread concern. The existence of stray current will lead to serious corrosion of rail, buried metal pipe, main structure of tunnel and its internal steel etc. This not only reduce the intensity of the metal structure, shorten the life span; but also cause the main structure of concrete cracking and reduce the structural strength and durability, increase the probability of failure of a structure. They will pose a serious threat to the safe operation of metro.The Beijing Subway tunnel affected by stray current corrosion as an engineering background, this paper makes a relevant analysis on stray current distribution, the influence of stray current corrosion on reliability and durability of tunnel structure, stray current protection measures and the need for protective measures in metro system. First, a brief introduction of the formation of stray current, analysis of the stray current distribution of mathematical model, stray current distribution as well as access to the influence of factors through theoretical analysis and numerical simulation, which have been implemented. Followed, paper outlines the stray current corrosion mechanism and stray current corrosion of metal structures affected by factors, determines the steel equivalent of electrochemical and the strength of the concrete legal changes by experimental study on stray current corrosion of the reinforcing steel in concrete and the influence of corrosion on concrete strength, expounds the main structure of tunnel durability limit state and durable life prediction model as well as establishes concrete corrosion cracking model, and completes the main structure durability calculation of subway tunnel through theoretical analysis. In addition, paper introduces the features of reliability analysis in subway tunnel under the stray current corrosion, expounds the load effect and structural resistance of the tunnel structure and the statistical characteristics of random variables, achieves the load effect's numerical simulation of tunnel lining through stochastic finite element method and completes the load effect's distribution fitting test of tunnel lining through x~2 fitting test method used, establishes ultimate strength corrosion decay model of concrete and tunnel lining structure limit state equation through theoretical analysis, and uses computer programs to achieve structural reliability analysis and calculation of the subway tunnel based on checking point method of a linear two rank moment theory. Finally, this paper also introduces the stray current corrosion hazards in brief as well as presents the necessity of metro stray current prevention, furthermore, from the source control method, current drainage method and new type method, a detailed analysis of stray current protection measures in metro system is carried out.Through the above-mentioned studies, some achievements can be drawn, which can be summed up as follows: stray current distribution functions and distribution plans of subway tunnel, and the influence of various factors on the distribution of stray current; term durability of the tunnel lining structure under the metro stray current corrosion; reliable indicators and failure probabilities of the tunnel lining structure, and decay curves of the reliable indicator ofβalong with etching time; reliability and durability of the tunnel structure by the impact of stray current corrosion; stray current protection of specific measures in metro system. The above conclusions only provide reference for subway tunnel design and stray current protection in metro operation for the future.
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