Abstract
A condition monitoring system for corrosion and stray current monitoring is being supplied and installed into the new metro line in Copenhagen known as the Cityringen project.
The objective of the system is to provide a combination of :
1. Pre-warning system for corrosion occurring within the concrete cover so as to spot the onset of corrosion at reinforcement depth using a number of anode ladder sensors and electrical resistance (ER) sensors.
2. To understand the areas of stray current flow through the tunnel and station walls through the use of sense electrode sensors.
The data will be used to refine the uncertainties and assumptions in service life model predictions of concrete durabilities developed prior to the structure design 1.
This paper describes the implementation of the monitoring system and the design consideration/ philosophy used when determining measurement location throughout the system and the challenges presented and overcome.
Introduction
The Copenhagen Metro is a rapid transport system serving Copenhagen, Frederiksberg, and Tarnby in Denmark and is owned and operated by Metroselskabet. The system first opened in 2002 and with two lines, M1 and M2. In 2011, construction began on the new circle line M3 (Cityringen) around Copenhagen that will consist of 2 × 17.4 km tunnels and 17 new stations all at 30 m below ground.
The Cityringen metro system, like the two lines M1 and M2, will be a driverless metro system which will operate 24 hrs a day. The metro system will operate on a 3rd rail floating 750V direct current (DC) system and incorporate a stray current collecting steel mesh reinforcement under the rails for the entire length. In the existing systems, a corrosion protection system has also been installed at Islands Brygge station (IBS) to provide protection to the reinforcing steel in the station diaphragm walls.
