Proposal of a Salt-damage Countermeasure Flowchart for Efficient Maintenance in Urban Railway Tunnels

Abstract

 To efficiently maintain and manage infrastructure within limited budgets, domestic infrastructure operators must understand the mechanisms of deterioration. They need to develop medium- to long-term plans and implement them by appropriately utilizing existing repairing methods and developing new ones. This study focused on RC tunnels degraded by salt damage. Field surveys were conducted, in terms of visual inspections, hammering tests, cover thickness, and reinforcement corrosion levels. The results confirmed that cover thickness significantly affects reinforcement corrosion levels. Furthermore, for cut-and-cover tunnels in the accelerated corrosion phase to the deterioration phase due to chloride attack, we identified the characteristics of deterioration and selected highly effective countermeasure methods based on railway-specific constraints. Finally, based on the field survey results and selected countermeasures, we proposed a flowchart for rational salt damage countermeasures and established a sustainable and efficient maintenance management system.