Facts about Stray Currents in MSE walls

Reinforced Earth® MSE walls have been used for direct support of electrified rail since the early 1970’s on five continents, and in the United States since 1977. The major metropolitan areas in the U.S. continue to use MSE walls with steel soil reinforcements to support electrified rail. On early projects, it was questioned whether stray currents from a rail system might negatively affect the corrosion rate of the soil reinforcements. A stray current in a rail system can be discharged into the ground when the railway is not completely insulated from the soil below. Three independent studies were conducted in the 1970’s and 1980’s by corrosion experts, and all concluded that the influence of stray currents is negligible in discrete steel soil reinforcements used in MSE walls.

The evidence points to four major factors. First, the discrete soil reinforcements are very short in comparison to the length of the rail tracks, and other common buried structures such as pipes and conduits. Second, the reinforcements in the soil are electrically discontinuous. Third, the MSE wall soil reinforcements are typically perpendicular to the direction of the rails and the system’s return current flow. Lastly, the MSE wall select backfill is specified to have a high resistivity, meaning current flow will seek a less resistive path such as the rails and in-situ soil.

Detailed information can be found in a 1999 technical paper in the Transportation Research Board’s journal, titled The Effects of Stray Currents on Performance of Metallic Reinforcements in Reinforced Earth Structures.