DEVEROPMENT OF THE METHOD TO PREDICT TIMING OF CHLORIDE ION ATTACK ON A TRANSMISSION SHIELD TUNNEL

Abstract

 At coastal areas, there exist most of the shield tunnels for power transmission line, whose reinforcing bars are going to be suffered with corrosion by chloride ion attack. To plan rational maintenance countermeasure of such shield tunnels, the method to predict the start of chloride ion attack is needed. By the occurrence of water leakage and salt concentration in these tunnels, the chloride ion concentration on the concrete surface increases due to the heat generated by transmission lines. In this study, we discussed the chloride ion concentration on the surface of the concrete, and estimated increasing rate in the chloride ion concentration on the concrete surface. Then, a method for predicting the start of chloride ion attack were devised in the case of that the chloride ion concentration on the concrete surface increases.