![]() The concept of compartmentalization of the tunnel led to the development of different solutions to seal tunnel segments susceptible to an extreme event such as a fire. The elevated cost of interrupting the tunnel operations or making major infrastructure modifications have also discouraged attempts to improve the tunnel resilience by these means. Typically, space constraints inhibit the installation of new protective devices such as automatic or manually operated mechanical gates. However, it can be difficult, if not impossible, to install or repair in an existing tunnel all the elements required for compartmentalization. To mitigate the effects of any eventual threat, a possible approach is to compartmentalize the tunnel system. These relatively new incidents and others that occurred in the past decades, such as fires that occurred in different tunnels across the world have demonstrated the need for planning and researching ways to mitigate vulnerabilities or, at least, minimize the consequences of catastrophic events.Īlthough it is impossible to prevent all situations that can lead to flooding, damage can be substantially minimized by reducing the area affected by the event. In 2012, in New York City, seven subway tunnels under the East River, as well as three road tunnels, flooded during Hurricane Sandy and remained inoperable for several days. The flooding left the tunnel damaged and closed for nearly a month. During this event, more than 167,000 m 3 (~ 44 million gallons) of water from the Elizabeth River flooded the tunnel system in just 40 min. In 2003, Hurricane Isabel caused flooding of the Midtown Tunnel in Virginia. Some examples of such incidents in the United States include the 1992 Chicago freight tunnel flood, which forced the shutdown of the subway system, caused damage to numerous businesses, and required the evacuation of about 250,000 people from the area. In particular, rail transit tunnels running under bodies of water or large-diameter pipes are susceptible to disruptions due to flooding originated by extraordinary climatic events such as hurricanes or human-made events. The protection of underground civil infrastructure continues to be a high priority for transportation and security agencies. The culmination of the work was 12 large-scale flooding demonstrations where the inflatable tunnel plug was shown able to be deployed remotely and withstand a simulated flooding event. Over 400 coupon and specimen tests, 200 reduced scale tests, and 100 full-scale tests were conducted to demonstrate the efficacy of the design of different prototypes over a 10-year research and development project. The main test results and lessons learned are presented to demonstrate the viability of implementing large-scale inflatable plugs for the containment of flooding in rail tunnels systems. This work presents a compilation of the main aspects of the activities completed for the development of large-scale inflatable structures as part of the Resilient Tunnel Plug (RTP) Project. Primary design constraints include having the plug stowed away from the dynamic envelope of the trains and being able to withhold the pressure of the flooding water. The sealing effectiveness depends on the ability of the inflatable structure to self-deploy and fit, without human intervention, to the intricacies of the perimeter of the conduit being sealed. The internal plug pressure imparts a normal force against the tunnel wall surface with the friction between the plug and tunnel surfaces opposing axial movement of the plug. In such an application, the inflatable structure is prepared for placement, either permanently or temporally, and maintained ready for deployment, inflation, and pressurization when needed. One way to create a temporary barrier is by the deployment of a large-scale inflatable structure, also known as an inflatable plug. To minimize the effects of an event, a possible approach is to compartmentalize the tunnel system by creating temporary barriers that can contain the propagation of flooding until a more permanent solution can be implemented. Although it is impossible to prevent all situations that can lead to flooding, damage can be substantially decreased by reducing the area affected by the event. Several events have taken place in the past decades that have demonstrated the need to mitigate vulnerabilities or, at least, minimize the consequences of catastrophic events. In particular, rail transit tunnels running under bodies of water are susceptible to disruptions due to flooding caused by extraordinary climatic events such as hurricanes or other events resulting from human activities. The protection of underground civil infrastructure continues to be a high priority for transportation and transit security agencies. ![]()
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