Toronto Ontario Line 3 | ?m | ?s | Metrolinx

My apolgies for misunderstanding.

No worries.

There are nearly 50 metres between facades along Overlea, and that wide space along the north side seems just begging for a right of way.

Had they stuck to keep the line along the northside of Overlea and running it straight to Don Mills (elevated), aesthetic issues aside, it would have reduced the tree cutting by at least 1/2, and it would have allowed for a very sensible station at Don Mills/Overlea which would have served one of the largest middle schools in the province and a high school, along with the southern 1/2 of Flemingdon Park.

Of course, that choice likely would have required demolishing the middle school to make it work which have added back at least 50M to the project cost.

It's not going to be pretty, but it's saving money and vegetation ultimately grows back.

Some vegetation will grow back, though it will take 30+ years to replicate what was there; but there is a structural net loss under the guideway and within about 10M adjacent, which does represent a material, sustained loss.
 
No worries.



Had they stuck to keep the line along the northside of Overlea and running it straight to Don Mills (elevated), aesthetic issues aside, it would have reduced the tree cutting by at least 1/2, and it would have allowed for a very sensible station at Don Mills/Overlea which would have served one of the largest middle schools in the province and a high school, along with the southern 1/2 of Flemingdon Park.

Of course, that choice likely would have required demolishing the middle school to make it work which have added back at least 50M to the project cost.



Some vegetation will grow back, though it will take 30+ years to replicate what was there; but there is a structural net loss under the guideway and within about 10M adjacent, which does represent a material, sustained loss.
wasnt the big reason they moved it to the power corridor is that they wanted to avoid a church on overlea or something?
 
wasnt the big reason they moved it to the power corridor is that they wanted to avoid a church on overlea or something?
The line also reaches MSF above grade via the current alignment (there were other options).

Yes, the church was a discussed reason, not that it would have been demo'ed; but if the line were elevated it would have cut across their front lawn.

1698420538635.png
 
Last edited:
From the Broadway Subway project:

Tunnel Liners. Each ring has 6 segments and a rail bed of concrete is poured.

Fngsq2GWQAI_sns

F1VufZEWAAoVByu


F9O8PbDbYAAbsxD


Elevated section (using girders and crossheads, not prefab post-tensioned segments), th
From the Broadway Subway project:

Tunnel Liners. Each ring has 6 segments and a rail bed of concrete is poured.

Fngsq2GWQAI_sns

F1VufZEWAAoVByu


F9O8PbDbYAAbsxD


Elevated section (using girders and crossheads, not prefab post-tensioned segments), then concrete is poured on top:

F0s0_csWcA4safZ

F1lLt8gWYAMRoyK

F6kJIG-WsAADybg

What's the Broadway subway project?
 
Vancouver?
Yes. It's the new subway tunnel (mostly) along West Broadway from the west end of the Millennium Line at VCC-Clark station, towards Arbutus. (the subsequent stage should get it about 4 more stations to UBC). This phase has new stations and is about 6-km long.
 
I decided to do a rough calculation to put this concrete consumption argument to rest. I took what information was readily available online for comparison. This compares typical elevated guideway sections of Skytrain Expo line and twin-bored tunnel sections of Skytrain Canada line. Each line uses standard track gauge and similar cab dimensions. Here's what I found:

Data Sources​

Elevated Guideway:
1698719088824.png

Source: Skytrain Noise Study: Noise Report and Maps

Google Screengrab of this style of guideway: Kingsway Expo Line Crossing
1698722465683.png


Precast Tunnel:
Canada Line Precast Concrete Radius ‘r’ = 2.65 m (measured as inner radius)
Concrete Thickness ‘t’ = 0.25 m

Source: Canada Line Transit Tunnels (Vancouver, BC): ground stability when excavating in Earth Pressure Balance mode

Calculations​

Precast Tunnel Cross Sectional Area of Concrete = ((r + 2)^2 - r^2) * pi * 2 (twin tunnels)
Total Cross Sectional Area = 8.718 m2
Precast Concrete Volume Per One Metre Twin Tunnel: 8.718 m3

As for the guideway cross section, I traced the approximate shape at scale using simpler geometries in Sketchup. The areas are effectively the same, however much easier to calculate.
cross section.png

Elevated Guideway Sectionalized Area Measurements: (A= 0.1725, B= 0.45, C= 0.255, D= 0.33, E= 0.02, F= 0.0225) m2 * 2 twin guideways
Total Cross Sectional Area: 2.50 m2
Concrete Volume Per One Metre Twin Guideway: 2.50 m3

For an observable comparison, here are the two geometries overlaid:
1698719706240.png


Evaluation​

As can be seen, the tunnel consumes significantly more concrete than the elevated guideway. This obviously ignores the concrete consumed by piers and other structures, which are complicated by variance in height and spacing. If we assume average spacing of 20 metres between piers, the leftover difference in concrete consumption ((8.718 - 2.50) * 20 = 124.36 m3) could build 1.5x1.5m square piers over 50 metres high. Realistically these piers wouldn't be higher than 10 metres on average from their anchored depth up to the guideway, so the volumetric savings should still be clear.

Of course, this is all grossly approximated. There are many other factors to consider. Tunneled sections and guideway geometry varies considerably in special trackwork sections (at switches), at stations, and around curves. Tunnel structures are designed differently depending on geomechanical properties of soil.

Most imporantly, transit should be built no matter the concrete cost; the sustained positive impact on carbon footprint trumps the one time construction impact. The criteria of concrete consumption should never outweigh any other design factor such as capital cost, ease of construction, and user accessibility. Concrete consumption in train alignments is a moot point.
 

Back
Top