3F22 STUDY ON THE AREA OF CAUTION FOR CHLORIDE ATTACK IN SUBWAY BOX TYPE TUNNELS(Condition Monitoring-Infrastructure)

Abstract

Tokyo Metro has been studying chloride-induced deterioration of subway tunnels by investigating tunnel bodies and taking countermeasure methods. From the resent results of the study, it had become clear that chloride-induced deterioration of subway tunnels almost always occurs at boundaries of areas leaking with chloride. For this reason, we studied potential areas that have chloride-induced deterioration in cut&cover tunnels by investigating the positional relation between tidal rivers and chloride leakage areas. As the result, it was found that the areas are 50m or more below the edges of tidal rivers. Then, seen from the viewpoint of advection-diffusion of chloride in the underground water, we verified the validity of the result by underground density flow analyses.