| With the vigorous development of China’s urban rail transit industry,the subway has become an important part of the urban three-dimensional transportation network,which has brought great convenience to the travel of the majority of urban residents.However,while urban rail transit brings people a comfortable riding experience,it also brings some potential problems.For example,the corrosion of metal structures caused by stray current leakage has huge safety hazards to passengers.Therefore,it is of great practical significance to explore the distribution law of stray current in urban rail transit and predict its corrosion hazards.Based on the current status of stray current research in China and abroad,this paper summarizes and analyzes the current research status of stray current distribution,stray current corrosion experiment and stray current corrosion prediction.Aiming at the dynamic leakage of stray current in the subway section and the threat of corrosion to the metal of buried metal pipelines,a research method combining finite element method numerical simulation and experiment is put forward.Meanwhile,a partial least squares(PLS)prediction model for predicting the corrosion current of buried pipelines through ground surface potential was established based on the simulation data of the finite element model.The study provides a systematic solution,which ranges from clarifying the distribution of stray currents to quantitatively calculating the amount of corrosion of buried pipelines,and finally realizing accurate prediction of corrosion.For the subway section,a three-dimensional finite element method stray current distribution model simulating the dynamic operation of subway vehicles is established.The model compares and analyzes the changes of soil potential,soil current density,rail potential,and buried pipeline current density under single and bilateral power supply conditions.The study found that the interference of stray current is directly affected by the operating conditions of subway vehicles.Compared with unilateral power supply,the bilateral power supply reduces the interference caused by the stray current to a certain extent.Several groups of pipe-to-ground voltage measurement experiments were carried out to simulate metro stray current interference and the measurement results have been verified by the corresponding finite element method models.The experiment and simulation results show that under the influence of subway stray current interference,soil resistivity,applied voltage and buried depth of the pipeline are the three main factors that affect the pipe-to-ground voltage.Based on the finite element distribution model of stray currents,this paper designs an experimental program to simulate the corrosion of buried pipelines under the interference of stray currents in subways.The corrosion experiments respectively studied the corrosion laws of dynamic and static stray currents on pipeline specimens.At the same time,based on the multi-physics coupling technology,finite element corrosion simulation models for simulating corrosion experiments were established,which realized the accurate simulation of the corrosion process of buried pipelines.The conclusion shows that the finite element numerical simulation can be used for the location of stray current corrosion area and the quantitative calculation of corrosion.Based on the finite element numerical calculation data,a partial least squares(PLS)corrosion prediction model between the surface potential and the corrosion current density of the pipeline specimen was established,and the purpose of predicting the corrosion of buried pipelines from the surface potential was realized.The PLS prediction model reduces the dependence on the amount of input data under the premise of ensuring the prediction accuracy,which provides a new idea for the prediction of subway stray current corrosion.A systematic scheme for predicting stray current corrosion based on ground potential has been established. |
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