Excellent discussion points. I got a post evaporated for mentioning many of the same points a couple of hours ago. Rather than me proffer what is obvious to some of us who follow this closely, I'll just quote some of the more interesting points, since you've made points the mod won't allow me to make:
My two-cents is that the Spadina Subway Line should be built as an underground LRT line from Bloor down to Queens Quay, where the LRT would continue to Union Station on the existing infrastructure. The Relief Line would continue to the west end (as traditionally planned), intersecting the Spadina Subway at Queen & Spadina.
I'm glad you're coming around to thinking that way, we were at odds some months back. The problem continues to be gauge, and I don't think the TTC gauge will be used in any more provincially financed initiatives. Any major LRT projects will be standard gauge. That ship has already left.
That would provide plenty of capacity for the foreseeable future. You can get to 26k people per hour in an LRT subway (based on the final capacity of the confederation line with 120m platforms) though in the much shorter term, would the TTC consider running double streetcars on the surface? The flexities can run coupled, and given the route is already segregated it should be possible to lengthen the existing platforms. The problem of course would be Queens quay and the existing loops at Union and Spadina, but it could be done.
The capacity issue is an excellent one, and you address it well.
Another idea for the relief line... Would the TTC consider using an entirely different rolling stock? With a narrower train than the TRs you can use a single bore tunnel which would bring costs down and maybe funding the whole line more likely.
Well, well. You got away with what got me banned for raising that issue in this forum, and for a post vaporizing a few hours ago. Since that post vaporized, I checked all the official literature I could find on the Relief Line. The most recent, at least, is now minus the 'subw' word. There is no mention of what the vehicle types will be. If someone takes great offence to that, I challenge them to post reference showing otherwise.
More specifically, how small does the single bore need to be to adequately fit between building foundations on Queen leaving sufficient buffer soil between the bore and the foundation to continue adequately supporting the foundation (prevent future foundation failure)? Is that difference in bore size really only a couple feet?
The big advantage to a single bore, IIRC, is severe reduction in the cost of the stations (since they can be built into the tunnel area) at a non-trivial increase in the cost of the bore. Madrid is taking this to an extreme and minimizing vertical digging by using elevators only for station access; no escalators. Covent Garden (London) hasn't exactly been a success with that configuration.
The answer is to look at London's great new success, partially opened now, and the central bored section end of this year. I daren't mention the name, it risks getting redacted, another poster does in a quote shortly.
It's not that it's impossible to have a wider single bore tunnel, otherwise you wouldn't have single bore car tunnels. It's that the savings dissapear the wider it gets. 2.5 to 2.6 m trains seem to be the norm for single bore, such as Madrid, Paris, and here in Canada Montreal and Ottawa
It all depends on geology, number of stations per distance, and ability to intersect with existing deep stations, minimizing the complexities of having to service passengers that deep. All discussed in great engineering and practical detail by the project I dare not name. Huge amounts on-line on this. They copied the Paris XXX (can't mention it) in many ways, albeit with a much more Anglo successful business model to finance and administrate.
Queen Street ROW is 20m. A single bore TBM for Toronto is a little over 10m. So you should be fine. It'll have less of an impact when compared to two 6m tunnels beside each other with a buffer.
I question those bore diameters, but defer to the quality of looking at this dynamically. Crosstown has set the boilerplate for local know-how of doing this. Crosstown's single bores, btw, are the same as London's XXX.
Victoria Line in London actually runs less than a feet under other rapid transit lines. The tolerances are incredible.
Vic is no longer the engineering template. The state of the art is now way ahead of that, see quotes following.
A civil engineer familiar with downtown Toronto excavations could wrap up this discussion pretty quickly. When Kyle brought it up I thought he might have some training/experience in the area.
I think the discussion of depth might change markedly with the next release of the study group. One of the reasons to go deep is not just geological, it's also the *inconsistency* of that geology, and the changing needs of a TBM head to bore through entirely different soil types. This also complicates the tight curves that have been drawn on maps by non-engineers. More on that when it comes time to discuss the changes in the first TPAP release.
Even crazier is Crossrail
https://akshatrathi.com/2014/08/02/...g-a-tunnel-under-london-is-an-epic-endeavour/ (read number 2)
"One of the biggest challenges has been tunnelling under Tottenham Court Road station. It is where the tunnel-boring machine needed to pass through very crowded space. The tunnellers have labelled it “the eye of the needle”. There the 900-tonne tunnel-boring machine has had to pass through a space where 30cm above it was a live escalator and 85 cm underneath was the active Northern Line."
I know Tottenham Court Station quite well personally, as well as following the XXX massive changes to it and the surface development.
There’s a lot of other presentations on YouTube about the engineering challenges for Crossrail as well.
Some excellent ones, as well as reams in text in engineering studies and the new standards set.
Also, speaking of smaller trains, they want to make the subway cars on the relief line 4 cars long. Considering that the line is expected to have more PPHPD than the Bloor-Danforth line and the Yonge line, does this not seem shortsighted? The TTC doesn't have to run 6 or 8 car trains during the off-peak, especially if all the entrances to the station's entrances lead to the middle of the platform, but having the platforms built to that length would prevent a future need to lengthen platforms.
Yeah, that discussion got me into a lot of trouble in this string prior. It's all in the reports, even though some refuse to believe the claim, and changing the length of a train already in service is just far too problematic. If it goes into service with four cars, it stays that way until it goes into the yard. And the yard discussion is another point. It's good to see others are questioning rote mantras.
