In late October 2012, Hurricane Sandy created havoc in New York City’s transit systems, flooding seven of the city’s 14 under-river subway tunnels and several major highway tunnels. Dr. Ever J. Barbaro, a West Virginia University professor of advanced materials engineering, is hoping this never happens again. He has been working for five years on a fix—an inflatable plug that can sustain up to 17 pounds per square inch (psi) of pressure inside a subway tunnel.
The U.S. Department of Homeland Security approached the professor for ideas about preventing subway systems from flooding, and “I said, ‘We’ll put an air bag in a tunnel,’” says Barbaro, who knew of European efforts to seal tunnels after a series of deadly tunnel fires.
ILC Dover, Frederica, Del., designs high-strength soft structures, including the air bags that cushioned the Mars rover landing, and suggested fabric made of Vectran™ yarn spun from a liquid-crystal polymer. The first full-scale model, made of a single layer of Vectran, ripped down the middle, necessitating several more designs and trials. The current model, successfully tested in November 2012, has three layers, the outer layer consisting of honeycombed Vectran belts. The one-ton folded fabric bag plugged a 16-foot-diameter tunnel within three minutes of being deployed.
“It’s a pancake, and then it becomes a burrito,” says Barbaro. Research continues, on everything from where to place the plug, how to fold it so it inflates properly and whether Vectran is rat-proof.