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Flooding due to natural disaster or breaks in water mains is a major threat to subways and tunnels, and stopping the flow of water becomes the No. 1 issue among authorities. In Chicago in 1992, for example, a flooded tunnel did $2 billion in damage to city property and 50,000 workers were affected. And Superstorm Sandy in 2012 devastated New York City’s subways.
To prevent or limit such disasters, a team of engineers at the Pacific Northwest National Laboratory developed a giant, inflatable structure that can be filled with pressurized air in less than 12 minutes—creating a flexible but extremely strong barrier large enough to fill a subway tunnel. In a demonstration, the device, the Resilient Tunnel Plug (RTP), held back simulated floodwater pushing at 11.5 lb per square inch against it.
The Department of Energy’s Pacific Northwest National Laboratory helped develop the Resilient Tunnel Plug in partnership with Northwest National.
“This is one of those things where we had an idea that was pretty simple but we needed to take that concept to reality,” PNNL engineer Greg Holter says. “The big problem wasn’t just designing the plug, but ensuring it could be stored without interfering with trains passing through their tunnels.”
The RTP is made from three layers of Vectran, a liquid crystal polymer, which ILC, a partner in the RTP project, had used to build landing pods for the Mars Rover. A webbed-fabric outer layer covers and protects the inflatable Vectran bladder. The device is designed to be pre-installed in a compact container and deployed at strategic locations in underground tunnels.
The development team also worked with West Virginia University for the Department of Homeland Security’s Science and Technology Directorate.
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