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| Re: why are subway lines in south Brooklyn mostly overground? (1349691) | |||
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Re: why are subway lines in south Brooklyn mostly overground? |
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Posted by LA Scott on Sun Apr 26 11:16:56 2015, in response to Re: why are subway lines in south Brooklyn mostly overground?, posted by Tramrunner on Sun Apr 26 08:41:30 2015. It all depends on the type of rock/soil.To tunnel in soil you either need some type of shield mechanism (like most of the older underwater tunnels used), or you need to freeze the ground first (as was done for part of the 7 extension). Tunneling in solid rock is less complicated, although still expensive. |
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