General Infrastructure

bakgwailo said:
Ah, well, that then answers my theory, I had thought they were reusable. I guess making them more reusable/easier to extract at the end would be a good start to changing the market for Musk. Either way we should be doing more tunneling (or even cut and covers) in general.
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I've only heard of them being reused after pretty short and easy runs. The one you linked to in Chicago, if the geology isn't bad, might be such a case. The larger ones, as Jeff was saying, aren't designed to be used so much longer, and that is partly to do with the incredible extraction costs. All the English Chunnel TBMs are still down there, entombed under the Channel.

The Big Bertha example seems like a perfect storm of problems for Washington DOT. In other parts of town, another agency, Sound Transit, has two machines going for rail lines. Those TBMs are far smaller in diameter and so far have been performing mostly well. I haven't found dimensions for comparisons, but I've seen pics, and they are way the hell smaller than Bertha, but do not look so small as the 19 footer you found in Chicago. They had been called Brenda and Pamela until Bertha ran amok, now Sound Transit is calling them TBM1 and TBM 2. I guess the cute names were the jinx?

Anyhow, if you can find info on those TBMS that Sound Transit is running, they might provide better cost estimate for Boston projects. Hopefully we won't be crazy enough to try to push the envelope like they did with Big Bertha. Very reputable manufacturer, but that can happen when you ask for the biggest ever.

Sound Transit Project page, if you want to dig in:

http://www.soundtransit.org/Projects-and-Plans
 
Re: Dorchester Bay Tunnel:

http://www.barlettaco.com/projects/TunnelProjects/CsoTunnel/csotunnel.html

Barletta was a joint venture partner on the Massachusetts Water Resources Authority’s $148 million CSO Storage Tunnel project.

The North Dorchester Bay CSO Tunnel is designed to temporarily hold up to 19 million gallons of combined sewer and storm water overflows caused by heavy rainfall. For decades, combined sewer overflows have discharged at six outfalls along South Boston’s public beaches. This project eliminated CSOs to the Bay, protecting swimming beaches, shell fish beds and other sensitive waters.

A 350 ton custom-built tunnel boring machine drilled and lined a two mile long, 20 foot diameter tunnel through glacial outwash sands and Boston Blue Clay at depths of 30 to 50 feet below K Street, Columbia Road, Day Boulevard, and the M Street, L Street, and Carson public beaches in South Boston.

The machine was lowered into place through a 55-foot-deep, 50-foot-diameter mining shaft at the starting point alongside the Massachusetts Port Authority’s Conley Container Terminal near Castle Island. It was removed through a 40-foot-deep, 34-foot-diameter receiving shaft drilled at the end point of the tunnel, behind the Massachusetts State Police barracks.

The TBM typically traveled 88 feet a day, and completed the mining and lining of the tunnel 6 months ahead of schedule. Installation of the five horizontally drilled connections between the tunnel and the diversion system drop shafts at the existing outfalls was done, and the concrete lining and roof structures at the mining and receiving shafts were completed.

An average of 25 people worked underground and 30 people above ground at any given point during the construction.
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Are water tunnels built to the same structural specs as transit tunnels (ignoring size and location)? Or do they "cut corners" (for lack of a better term) with tunnels for water that they wouldn't be allowed to cut with tunnels for people?

Also could a Blue Line train hypothetically fit in a 20 ft diameter tunnel? I'm not saying this 20 ft tunnel, just one in the abstract.
 
I think drinking water can handle tighter turns and steeper grades than trains. (Drain / sewer pipes do have some very specific grade requirements in general so that gravity can move the waste; fresh water pipes generally just depend on having the water source at a higher elevation than the destination.)
 
JumboBuc said:
Are water tunnels built to the same structural specs as transit tunnels (ignoring size and location)? Or do they "cut corners" (for lack of a better term) with tunnels for water that they wouldn't be allowed to cut with tunnels for people?
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I don't know the answer to the structural part of your question, but when comparing costs, we have to remember that once a water or sewage pipe of this sort is lined with concrete, that's pretty much it. Once a transit tunnel is lined with concrete, then a railroad needs to be built through the tunnel. Lots of steel rail being laid to fine tolerances, lots of electrical equipment, some sort of passenger evacuation walkway, emergency generators to light the walkway in case of power outage, etc. Pricey stuff. I think when we see costs for transit tunnels, these are generally not broken out from the actual tunnel digging. So the price per mile of a transit tunnel most typically is the all-in cost, digging and fitting out to full railway usage. Whereas the price per mile of a water or sewage tunnel is the digging plus a very modest lining with concrete, and that's it. Maybe they can also go a bit cheaper on structural integrity since there won't be people in it, but..... I'm guessing since they don't want it to collapse any time soon, they might not go much cheaper.

JumboBuc said:
Also could a Blue Line train hypothetically fit in a 20 ft diameter tunnel? I'm not saying this 20 ft tunnel, just one in the abstract.
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I found the diameters of the Sound Transit TBMs that I linked to yesterday: 21.5 feet. Only a bit more than the MWRA's tunnel. Each of those Sound Transit TMBs is doing one direction of a line, one northbound, one southbound. If you look at Sound Transit vehicles, they look pretty typical for subway cars. This doesn't quite answer your question about a Blue Line car fitting into a 20 ft diameter tunnel .....

Oh yeah, back on the cost issue: transit tunnels often include a few underground stations. They just devour money. I've never yet seen a transit extension budget break that out, either. It's just $XB for a subway tunnel of Y miles including Z underground stations. Makes it very hard to do cost comparisons to tunnels like what the MWRA built - not to take any credit from them, seems like they did a great job. But we're into serious apples to oranges territory.
 
Joel N. Weber II said:
At what point does a Tesla Powerwall or Powerpack become a better choice than a generator?
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I haven't the slightest clue... whatever works.

I once had to evacuate from a Green Line Train about halfway between Arlington and Copley. There were a few senior citizens needing significant assistance. With emergency lights? Not really a big deal, albeit not a lot of fun, either. Without emergency lights? That would've been a nightmare for all concerned. I've carried a little mini flashlight in my briefcase ever since.

So from my perspective, they can switch over to generator alternatives any time they want, so long as they function in a crisis ....
 
At this point, smartphones are generally usable as flashlights.

I also think the T ought to be putting battery packs in all subway trains sufficient to advance to the next station at 5-10 MPH, which would probably avoid some but not all situations where passengers end up having to walk along the tracks (although such batteries might also make certain runaway train situations more dangerous if cutting third rail power is no longer an effective way to stop a train, but if you're concerned about that, maybe there could be some mechanism to require dispatcher authorization before the computer on the train would allow the battery to be used for traction power).
 
^ If we get into the territory of putting battery packs on trains then we can also probably just scrap electrifying the rails all together. Have charging stations at designated stops and let the trains run on their own power (with regenerative braking) between them. This doesn't make any sense where electrified rails already exist, but for new construction it could be practical.

The technology obviously isn't there yet, but it might not be that far away.
 
Joel N. Weber II said:
At this point, smartphones are generally usable as flashlights.
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Not worth a damn they aren't. I mean yes, in a pinch for a few moments -fumbling key into lock if porch light is off, e.g. But for any distance over any rough ground like in the Green Line tunnel, nope, they suck - just not enough lumens. Also, when things are going wrong, I want to conserve my phone battery for phone usage. Using the phone as a flashlight for a serious evacuation can lead to a compounding effect: start off with one problem, a dead train, finally get out of that problem to find oneself with another problem, a dead phone unable to call Uber or friends for a ride.

Your other point is worth consideration, I like that. I have no idea if it's practical for space / maintenance reasons.
 
JumboBuc said:
^ If we get into the territory of putting battery packs on trains then we can also probably just scrap electrifying the rails all together. Have charging stations at designated stops and let the trains run on their own power (with regenerative braking) between them. This doesn't make any sense where electrified rails already exist, but for new construction it could be practical.

The technology obviously isn't there yet, but it might not be that far away.
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http://www.dallasnews.com/news/tran...wered-streetcars-for-downtown-oak-cliff-route

Dallas and Detroit
 
I find my smartphone light works quite well indoors and is plenty bright when I'm shining it on something 10' or maybe 15' away, which was what I was making assumptions based on, but of course I'm typically looking at white walls, and the transit tunnel walls and track surfaces probably tend to be much less reflective. But I don't get the impression that a few minutes of flashlight use would have any substantial effect on the state of the smartphone's battery charge.

A typical Tesla Model S / Model X battery pack has a nominal voltage in the 300V to 400V range, and with the Ludicrous mode they were talking about upgrading the fuse from 1300A to 1600A IIRC; the pack probably weighs something in the ballpark of 1000 pounds, which is not too significant in the grand scheme of a subway car if one battery pack turns out to provide sufficient power. It should be noted that, at least with the technology available when Ludicrous mode first came out, the battery pack needed to be close to full to get the full amperage out of it. I'm not sure what the subway wattage requirements are, though.
 
JumboBuc said:
^ If we get into the territory of putting battery packs on trains then we can also probably just scrap electrifying the rails all together. Have charging stations at designated stops and let the trains run on their own power (with regenerative braking) between them. This doesn't make any sense where electrified rails already exist, but for new construction it could be practical.

The technology obviously isn't there yet, but it might not be that far away.
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There are some buses doing this in Korea. And they are using induction charging, so no contact needed at the stops for the recharge.

Probably more practical in a tunnel than outdoors with a bus, because of things like snow getting in the way of charging.
 
JumboBuc said:
^ If we get into the territory of putting battery packs on trains then we can also probably just scrap electrifying the rails all together. Have charging stations at designated stops and let the trains run on their own power (with regenerative braking) between them. This doesn't make any sense where electrified rails already exist, but for new construction it could be practical.

The technology obviously isn't there yet, but it might not be that far away.
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Look at the tram in Zaragoza (Spain). This is exactly how it works inside the historic city center (for aesthetic reasons). I am not sure about reliability but it is absolutely beautiful.

The technology is definitely there.

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Don't think that there's a specific thread for this, but work is progressing on the Woods Memorial Bridge (Route 16 over the Malden River) replacement in Medrord/Everett. The new westbound span is open to traffic, but as of a couple weeks ago the new sidewalk was still closed. So there is still time to experience the old, slippery, open deck sidewalk next to 50mph traffic if there are any thrill-seekers out there.

xt5UiuY.jpg
 
Uncivil_Engineer said:
Don't think that there's a specific thread for this, but work is progressing on the Woods Memorial Bridge (Route 16 over the Malden River) replacement in Medrord/Everett. The new westbound span is open to traffic, but as of a couple weeks ago the new sidewalk was still closed. So there is still time to experience the old, slippery, open deck sidewalk next to 50mph traffic if there are any thrill-seekers out there.

xt5UiuY.jpg
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Thanks. Unless I'm confusing it with another Route 16 bridge, this one is a former drawbridge and the reconstruction is wrapped up with a bunch of bike and pedestrian improvements. Sorry, to lazy to google and confirm I've got the right bridge.
 
jass said:
I was at this corner this weekend:
https://goo.gl/maps/K1jDh8DFVW72

100+ pedestrians and for the 10 minutes I observed, the pedestrian phase did NOT activate at all.

What a disaster.
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Many of these complex intersections in Boston will only activate the pedestrian cycle after the appropriate button is pushed. Sometimes the buttons are broken (and need to be reported to 311). The City does respond promptly and try to fix /replace them.
 
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