ABSTRACT
Chloride attack is the main cause for deterioration of subway tunnels. Tokyo Metro studied on the potential area of chloride induce deterioration in the box type tunnel with investigating positional relations between tidal rivers and saltwater leakage parts. As the results, it is found that the influenced areas are within the range of 50 m from edge of the tidal river. And we confirmed generality of the result by a ground water density flow analysis. Moreover, it is also found that the area of chloride ion attack is limited on area of leakage and trace part of it on the lining. For chloride penetration route, it is cleared that chloride ion in the tidal river move into underground, enter into subway tunnel through clacks or joints of tunnel lining and penetrate into lining from inside surface of the tunnel. The report describes procedure and results of the study.
