The Canarsie Tunnel, along the L-Line of the New York subway network, links Manhattan with Brooklyn. The tunnel was flooded in 2012 during Hurricane Sandy, resulting in damage to electrical cables and the concrete duct banks. The initial refurbishing of the Canarsie Tunnel project plans called for a complete closure of the tunnel for 18 months to replace the duct banks and cables, causing significant disruption to L-Train commuters.
Governor Cuomo encouraged MTS to consider innovative alternatives to maintain service during repairs. With the support of Cornell and Columbia University experts, an alternative plan was adopted implementing a new racking system for the power cables and leaving the original bench wall in a place where structurally stable. Short sections of the bench wall were demolished and others were reinforced in fiber-reinforced polymers.
As an additional safety measure distributed “Smart” optical fiber sensor cables were installed along the remaining bench wall to detect and localize future shifts and cracks. MTA selected Smartec and Roctest to supply and implement this advanced fiber-optic monitoring system.
The rehabilitation of The Canarsie Tunnel project was completed in June 2020.
The measurements are performed using SMARTEC’s Hydro & Geo sensing cable with a total length of more than 4’000m, covering both duct banks in the two parallel tunnels. The measurement cabinet includes redundant DiTeSt distributed strain sensing systems combined with DiTemp temperature sensing interrogators. The DiView data management system combines information from both systems to analyze strain and temperature variations in the two tunnels and displays the results in a single user interface. Alerts can be set based on different conditions for strain and temperature variations and enable easy localization of the triggering events.