Tuesday, March 29, 2011
Tunneling under 2nd Ave Resumes
TBM Run No. 2 Now Underway
Update - 3/30/11
Two recent images of the TBM under 2nd Avenue
have now been added to this posting.
The MTA announced on its web site on Monday that the Second Avenue Subway Tunnel Boring Machine (TBM) is once again on the move.
The machine will now mine the second (east) tunnel for the project - from a point about just south of 92nd Street down to 63rd Street - a length of 7,800 linear feet.
Near the end of this run, the machine will make a relatively tight westerly curve into the existing 63rd Street Station / Lexington Avenue station. (A map of the TBM's route can be found on this Google Map link.)
The connection at 63rd Street will be to a short piece of tunnel, known as a bellmouth, that was constructed at this station back in the late 1970s. (A diagram showing the 63rd Street bellmouth can be found on this link.)
During the first 200 feet of this run, the TBM will be mining through an area under Second Avenue that contractors had recently frozen solid. This was done intentionally so that the TBM could safely bore through the weak rock structure in this area.
The TBM previously mined 7,162 feet for the first (west) tunnel. The 485-ton, 450-foot-long machine began mining in June 2010 from 92nd Street to 65th Street and was then disassembled and pulled back to the TBM launch box at 92nd Street.
Phase I of the Second Avenue subway (i.e. the extension of Q Line service to the Upper East side) is currently scheduled to be completed by December 2016.
The MTA's press announcement can be found on this link:
Tunneling Mining for Second Avenue Subway Continues
MTA web site - 3/28/11
Update - 3/30/11
These two images, which were provide to me by e-mail late today, show the TBM as it is now positioned at the head of east tunnel.
In this image you are looking at the southern end of the Second Avenue subway TBM launch box. The soon to be minded east tunnel is on the left and the new west tunnel is on the right.
The head of the TBM is positioned inside a 40-foot starter tunnel that was blasted out about a year ago.
This zoom shot provides more detail. Look closely and you will see a number of interesting things. (left-click either image for a larger view)
As example -
Look on the left-hand side of the image and you will see an open umbrella that has been mounted on a yellow boom. Its hard to tell, but it looks like this umbrella has been setup to protect one of the total stations that keep the TBM lined up as it mines.
Also on the left, on the floor, you can see a temporary conveyor belt. Normally the muck from the TBM mining process is transported to waiting muck cars via a conveyor that runs down the middle of the machine.
The sunlight in these images is coming in through the glory hole in front of Delizia's Ristorante & Pizza on the SE corner of East 92nd Street and Second Avenue.
Posted by Ben H on 3/29/2011 11:00:00 PM