Abstract
In recent decades, a number of studies have been reported that exposure of concrete structures to the high concentration of chloride ions near marine causes the chloride attack, leading concrete to deteriorate. However, current studies on this issue have insufficient information to assess the mechanisms of deterioration and countermeasures. In order to understand the details of chloride attack phenomena and select an appropriate countermeasure systematically. In this study, follows were investigated; the various factors affecting concrete deterioration, including the variation of chloride ions levels in tidal zones and tunnels with leakage, and the penetrating routes of chloride ions into tunnel structures, as well as influence range of chloride ions on concrete structures induced by leakages. Consequently, we clarified the mechanisms of chloride attack occurred at box type tunnels in subway lines. In addition, an appropriate and simple method of investigation was conducted to estimate the influence range of chloride attack for subway tunnels under short hours and tight spaces for work. Furthermore, the most suitable repaired material and method were selected for repair works. Based on this research and study, the countermeasure system for preventing the chloride attack which is able to identify locations need repair work and countermeasure under various environmental conditions was developed.
