Study On Distribution And Corrosion Protection Of Stray Current From Metro In Red Soil Region

With the rapid development of the economy,the construction of metro is speeding up in the first-line cities or second-line cities in the south-central region of China.And up to January 2018,the number of cities where metros have been in operation,has reached 17,and the operating mileage of metro has reached 2000 km in total in the south-central region of China.The red soil is mainly distributed in south-central region of China.And the stray current from metro has the characteristics of very strong electrochemical corrosion in this region.It is significant for the safe and stable operation of metro and the corrosion protection of buried metal pipelines through studying the distribution of stray current as well as putting forward the protection measures from stray current.Firstly,the model of stray current is established by using CDEGS software in this thesis.This model mainly includes some important conductors,such as segment concrete reinforcement,road bed,bars of collection network,rails and power supply conductors.And the model is verified by comparing with the R-network model under the condition of same railground transition resistance.Secondly,the potential gradient method used in the field of buried pipeline is introduced into the CDEGS software.The density and the distribution of stray currents in the area is studied through calculating the potential gradients in the vicinity of the tunnel in three-dimensional model.Finally,the distribution range and corrosion area of metro stray current in red soil area are studied in the ideal state and non-ideal state respectively,and the scopes of corrosion and protection of buried metal are obtained in these two states.And the study shows that the distribution of stray currents in the red soil area is wide and the dense area of stray current distribution in this area is nearly twice times of the northeastern China.Based on the above conclusions,the effect of protection from stray current is studied mainly in the aspects of rail construction,power supply design,locomotive operation,construction of collection network and reflow line addition,and then some protective measures are put forward.