Dynamic Fluctuation Characteristics of Pipe-to-Soil Potential on Buried Pipelines under Interference of Stray Current from Subway

The pipe-to-soil potential data of underground pipeline under dynamic DC interference caused by subways and monitored in Beijing, Shanghai, Shenzhen and Wuxi were analyzed systematically. The dynamic characteristics such as fluctuation period, period distribution and fluctuation amplitude of the pipe-to-soil potential under the disturbance of subway stray current were calculated in different cities. The effect of pipe-to-soil switch-on potential on switch-off potential was studied, and the law of pipe-to-soil potential fluctuation dynamically caused by the stray currents from subways was summarized. The results show that in the running periods of subways, the pipe-to-soil switch-on potentials fluctuated drastically, and the fluctuations were periodic. The distribution proportions of fluctuation periods of the pipe-to-soil swtich-on potentials were nearly the same for different monitoring points in the same city, and were similar for different cities. The fluctuation amplitudes and interference degrees of pipe-to-soil potentials were different in different cities. The fluctuation periods of pipe-to-soil switch-on and switch-off potentials were coincided, and the fluctuation of switch-on potential had a small effect on switch-off potential.