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| Re: Second Ave Alignment Change (637599) | |||
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Re: Second Ave Alignment Change |
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Posted by JournalSquare-K-Car on Sat Jun 21 21:12:00 2008, in response to Re: Second Ave Alignment Change, posted by SelkirkTMO on Sat Jun 21 01:14:32 2008. So 6av was local only originally?Was it just under the PATH? How long did it take to add the express, and did they use a shield? Also, did local service continue to run during the process? Also, i read that the BSS was local only at first, until they expanded it to have one of the best express runs in the world. Did they wuild the local and express tunnels at the beginning, or did they use a shield to just widen the tunnels? The problem with TBM structures is that since it is a tube, you can't dig into its side without enough support, because you undermine the interity of the arched roof. With a square tunnel with STEEL and CONCRETE beams, this is not a problem. You can leave the beams there, and dig between them. |
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