Most modern subways, such as the 7 Subway Extension to Hudson Yards and the Second Avenue Subway are TBM drilled. Most subway construction is cut and cover, however, most subway construction occurred before 1980.
Thank you. I haven't been paying too much attention to modern subway construction techniques, living as I do in the Philadelphia area, where I'm pretty sure the short stretch under the Schuylkill River is the only non cut and cover portion.Is deep bore cheaper than cut and cover, or elevated or surface? It looks like Vsmith started this line of thought"even if we had to elevate or redirect parts of the routes its still 30-40% the costs and 3 -4 time faster to build then a subway"blue streak 1 said"the problem of utilities running underneath that line is still there. ... who would have to pay for their relocation or hardening under this ROW"I questioned "how taking care of possible utilities for a surface or elevated line could be more expensive than for a subway"I get the impression BaltACD thinks deep bore is cheaper than elevated or surface, otherwise why would he say it represented 'dodging' the problem, or perhaps he meant they throw money at the problem to 'dodge' it, which kind of misses the point I think vsmith's trying to make
Patrick Boylan
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A lot depends on nature of the soil and ground in general as to what type of subway construciton is least expensive. One example would be a built-up area where the desire is for a direct subway line to go diaganaly with respect to the street grid, and underneath all the buildings is hard rock. Deep bore is the only solution. But note that deep stations require elevators as well as escalators, all with their maintenance, adding costs. The other extreme would be a subway under a wide boulevard where disruption of two or three or four lanes can be tolerated and the soil is soft or clay.
But subway construction ALWAYS costs between four and ten time the cost of a street-based streetcar line, even with massive utility relocation.
New York's original IRT subway was mostly cut-and-cover. But 145th - Dykman-200th Street was bored, and this 1904-1906.
In Chicago, the State Street subway was tunneled by deep-bore in 1942, with perhaps some cut-and-cover work where it connected with the L. The steeple of Holy Name Cathedral has a slight but visible lean to the southwest that apparently occured when the subway was tunneled.
I believe that the Dearborn Subway (Congress-Milwaukee line) was also tunneled by deep-bore.
Google Books covers this very topic in 1911
By American Electric Railway Engineering Association. Convention
IIRC, the Chicago subways were bored through blue clay, which is much easier to cut through than hard rock. It also had the advantage of being reasonably water tight, so no air was needed to keep water out.
- Erik
gardendance I get the impression BaltACD thinks deep bore is cheaper than elevated or surface, otherwise why would he say it represented 'dodging' the problem, or perhaps he meant they throw money at the problem to 'dodge' it, which kind of misses the point I think vsmith's trying to make
I get the impression BaltACD thinks deep bore is cheaper than elevated or surface, otherwise why would he say it represented 'dodging' the problem, or perhaps he meant they throw money at the problem to 'dodge' it, which kind of misses the point I think vsmith's trying to make
Not cheaper - just a different set of challenges - One tends to forget all the 'utilities' that exist in near proximity to routes that are above ground and must be rerouted and secured against the operation of the transportation medium. And the owners of the utilities must coordinate their own actions with all the owners of the other utilities.
Among the utilities that must be accounted for - Water, Storm Sewer, Waste Water Sewer, Electric, Telephone, Steam Lines - and probably half a dozen other things I can't comprehend - all owned by different entities and all with their own operating parameters that must be protected and accounted for in allowing todays usage as well as planning for tomorrows usage.
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