How do they ventilate subway tunnels when they are building them? Obviously they cant use just electric vehicles to create stations and tunnels. TBMs are electric but they must use excavators, loaders, etc when building stations beneath the surface. How do they ventilate these tunnels?
There are several methods that have and are employed to make tunnels.1 Why do you feel it is obvious that electric machines cannot be used? Tunnels are the type of spaces with limited air that are ideal for the use of non polluting vehicles. Rather than say We have to make pollution, how can we move it somewhere else engineers have asked, How can we not pollute the air. Subways are electrically powered. Modern tunneling machines are probably the very largest electric vehicles.2 Some of the machines have their own power stations located outside of the tunnels and some of the machines will use a grid connection. In most pictures of tunneling you will notice either a conveyor belt or a railroad removing debris.Both of these are also easily electrified. Formerly shafts were sometimes run to the surface for removing debris. And this may continue to be a solution for ongoing operations. There is an island in the middle of the East River in NYC outside of the UN that was formed from tunneling debris for the #7 subway line.3
There is a fan plant built next to an access shaft. The fans blow fresh air through the duct that runs down the shaft and into the tunnel, suspended from the tunnel's arch, all the way to the TBM. As the TBM advances, workers add new sections of the duct. The air then flows through the tunnel back to the access shaft. The section of the NYC's Third Water Tunnel I've been to, used very little engine powered heavy equipment. The train that brought workers and supplies to and from the TBM run on the CNG. Everything else run on electricity.
