In order to study the effect of soil salt content on the stray current distribution in the urban rail transit, a threelayer stray current resistance network distribution model of " rail -drainage net-ground" is established based on the method of resistance network. The mathematical model is established by using the equivalent circuit of micro-element, and the analytical expressions of voltage and current of each metal structure are derived. Then, the simulation model is established with MATLAB/Simulink software, and the simulation results are consistent with the analytical results. A small-scale experimental platform corresponding to the model is built, and the changes of leakage current and the stray current in soil samples with different NaCl content are measured. The experimental results show that the leakage current and stray current in soil samples increases with the increase of NaCl content. Finally, the experimental results are verified by the established simulation model and the simulation results are basically consistent with the experimental results, which proves the accuracy of the experimental results. The research results can provide a theoretical basis for the protection design of subway stray current.

In order to study the effect of soil salt content on the corrosion of buried metal by the stray current in urban rail transit, a small experimental platform for the buried metal corrosion is built. The corrosion rate and mass loss of buried carbon steel specimens in soil samples with or without DC stray current are measured and calculated when different content of NaCl is added into the soil samples, respectively. The experimental results show that the corrosion rate and mass loss of the buried metal increase with the increase of soil salt content. DC stray current will aggravate the corrosion of the buried metal. The corrosion degree of buried metal will be seriously aggravated under the coupling action of DC stray current and salt. When there is no DC stray curren, the corrosion degree of buried metal is relatively small, and the influence of soil salt content on the buried metal corrosion is also relatively small. Finally, a multiphysics simulation model corresponding to the experiment is established to verify the experimental results. The simulation results are basically consistent with the experimental results, which proves the accuracy of the experimental results. The research results can provide a theoretical basis for the corrosion protection design of subway stray current.