While watching videos of the NYC subways, I’ve noticed that the tunnels have different shapes. Sometimes rounded or tubular and other times square or box shaped. Seems that the tubular shape is predominantly where the line goes under a waterway. Yet, you can also see sections where the shape of the tunnel changes back and forth between different bore shapes. I find the subway system to be a fascinating engineering feat.
Box-shaped tunnels were built using cut-and-cover methods. Tubular tunnels were bored using shield tunneling.
A good look at the Pennsy ‘proposed’ North and East River tunnel sections which were displayed at the 1904 St. Louis World’s Fair:
Penn-Station_tubes by Edmund, on Flickr
Still in use today, of course. I wonder just how many of those bolted, cast iron segments were used to construct the six ‘tubes’?
Another fascinating and innovative design is the Detroit River tunnels, opened in July, 1910. Pre-made sections floated into place and set into a dredged trench.
Detroit Tunnel floating in place by Edmund, on Flickr
Also still in use today.
Regards, Ed
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To my mind - B&O and later CSX ‘missed the boat’ in solving the Howard Street Tunnel problem when they did not ‘piggyback’ on the construction of the Baltimore Harbor Tunnel in the middle 1950’s or the construction of the Fort McHenry Tunnel in the 1970’s. Both of these tunnel had trenches dredged for their under water sections and had prebuilt segments sunk
I remain frankly amazed to this day that Gibbs and Hill managed to shoehorn 11kV AC catenary into that clearance profile… with peak power draw for a 1.3% grade. Now with bilevel equipment, too.
No tunnel project even in the 1970s would likely have predicted double-stack clearances, although they might well have been designed for 25kV overhead catenary installation. A PSE&G powerline extension across the Jersey Meadows was built with integral cat bridges… on which catenary was never installed.
An interesting consideration can be seen on the Lexington Avenue ex-IRT, where portions of the route were deep-trenched and the local track and platform are stacked on top of the express. There is no underground connection between uptown and downtown llnes at many of these stations.
What condition would the cast iron shields be in after all the decades of exposure? Seems that eveventually they are going to start to fail and need replacement. As for the float in place tunnel construction, I don’t see how they accuraetly lined all that up and then got it joined together. Amazing work.
MANPOWER! Divers to align and bolt together the sections, that would be flooded to sink them into position. After everything is bolted up, each section is pumped dry and all the finishing work would then take place.
Remember, early in the 20th Century - life was cheap.
Which was the way that BART’s Trans-Bay tunnel was built in the late 1960’s, though with some provisions for flexing to handle earthquakes (it handily survived the 1989 Loma Prieta earthquake).
Mentioning the BART. I have seen several of their transit cars passing through the Indianapolis area on trucks headed east on I-70. Any idea on what this is?
Also, I thank all of you guys for responding to my question.
Chicago’s subways under the river also used the same method. In addition Chicago also used bored tunnels under the streets rather than cut and cover due to the shallow water table in the city.
City was basically built on a swamp.
This is also how the Ted Williams (I-90) across Boston Harbor and the South Boston Piers Transit way (Silver Line BRT) across the Fort Point Channel were constructed in Boston as part of the Big Dig in the late '90’s.
The TWT was possibly the easiest segment of tunnel construction on that project. Much easier to build in a shipyard and in the middle of water than underneath an existing expressway in a dense urban area built most on 18th-century landfill.
Dan
Former business partner and remaining close friend provided the followimg URL:
https://www.westsiderag.com/2024/07/18/look-closely-you-just-might-see-the-uws-91st-street-ghost-station-photos
A comment:
Around1959, not omly was the 96th Street Station extended south with
94th Street entrances, but a very major change occurred in West Side
IRT operation. Before February 1959.10-car trains from Van Cortlandt
Park West 242nd Street switched from the outside track just north of
96th St. Sta. to the inside express track and ran express, ending up
in Brooklyn in most normal service. Locals were onl
And fellow Branford (Shore-Line Trolley) and ERA member William Wall provides a URL of even greater interest:
://www.youtube.com/playlist?list=PLNa6mCAY5NOSkARCIFadmA_POYXMsZXhw