Millennium Line - Broadway Extension: Planning & Pre-Construction

[Migrant_Coconut]

Broadway-Alma to Chancellor might work. No disruption to Point Grey Village, and there aren't enough residents to affect an election.

[jsbertram]

Originally Posted by scryer

Seeing as how we are now veering off-topic to other potential transit projects...

I was wondering what the realities are if we were to cut-and-cover for phase 2 after Arbutus? Would the Cut-and-Cover technique stall bus service too much? Does the Millennium line extension all have to be done only using one technique? Would the NIMBYs burn down our forests over this? Thoughts?

engineers know that making a transition from TBM tunnelling to something cheaper, like cut n cover or elevated ends up not being cheaper because of the extra expense of making the transition from one construction method to the other

there are exceptions when the existing conditions require the transition (canada line can be subway in vancouver but needs to be elevated in richmond because of the water table there and earthquake survivability)

[jsbertram]

Originally Posted by Migrant_Coconut

Broadway-Alma to Chancellor might work. No disruption to Point Grey Village, and there aren't enough residents to affect an election.

and then where to?

[officedweller]

Also, if there are different soil types along the route, they may need different TBMs (i.e. different cutter heads).
Apparently, if Canada Line was bored the whole way, they would have needed different TBMs to bore through Little Mountain.

[M00dy]

Originally Posted by jsbertram

engineers know that making a transition from TBM tunnelling to something cheaper, like cut n cover or elevated ends up not being cheaper because of the extra expense of making the transition from one construction method to the other

there are exceptions when the existing conditions require the transition (canada line can be subway in vancouver but needs to be elevated in richmond because of the water table there and earthquake survivability)

I don't think that's necessarily true on a transit project, where the stations are cut & cover or caverns already. The transition has to happen at every station regardless, so it would be simple to stop the TBM at one end & continue with a cut & cover.

I think one argument for continuing with the TBM here though could be the advantage of scale --> the machine is already there, already tunneling. A huge part of the costs are machine fabrication/purchase, mobilization & demob. If you can carry the bore the whole way there might not be a reason to transition.

[scryer]

Originally Posted by M00dy

A huge part of the costs are machine fabrication/purchase, mobilization & demob. If you can carry the bore the whole way there might not be a reason to transition.

That is pretty much my biggest concern. I feel that once we get this TBM in the ground, we are going to have to really fight to keep it going until it either surfaces or reaches UBC.

[jsbertram]

Originally Posted by M00dy

I don't think that's necessarily true on a transit project, where the stations are cut & cover or caverns already. The transition has to happen at every station regardless, so it would be simple to stop the TBM at one end & continue with a cut & cover.

I think one argument for continuing with the TBM here though could be the advantage of scale --> the machine is already there, already tunneling. A huge part of the costs are machine fabrication/purchase, mobilization & demob. If you can carry the bore the whole way there might not be a reason to transition.

the canada line TBM had its launch and extraction pits at locations that were conveniently going to become stations (olympic and waterfront respectively)

the TBM pits used to build broadway phase I will likewise become the Great Northern Way and Arbutus stations, with trains full of passengers using them every few minutes by the time phase II is OK'd.

so it's likely another new launch pit in the middle of Broadway will have to be created west of Arbutus to start the phase II TBM going to UBC, with up to 10,000 truckloads of extracted muck and spoil coming out of the launch pit and traveling across Vancouver for disposal, and a nearly equal number of truckloads of concrete, pre-built TBM rings, rails, and other components needed to build phase II

[jsbertram]

Originally Posted by scryer

That is pretty much my biggest concern. I feel that once we get this TBM in the ground, we are going to have to really fight to keep it going until it either surfaces or reaches UBC.

ideally, the TBM would bore directly to UBC, since it's impossible to have the tunnels being used for moving construction materials through them at the same they have passenger trains running in them.

this unfortunately means a full bore to UBC will take a longer construction schedule and be more expensive

[cganuelas1995]

Originally Posted by jsbertram

ideally, the TBM would bore directly to UBC, since it's impossible to have the tunnels being used for moving construction materials through them at the same they have passenger trains running in them.

this unfortunately means a full bore to UBC will take a longer construction schedule and be more expensive

Yeah, rough in the entire tunnel to UBC and just finish it to Arbutus for stage I.

[Bdawe]

Originally Posted by cganuelas1995

Yeah, rough in the entire tunnel to UBC and just finish it to Arbutus for stage I.

That seems like a good idea. And station excavation would still leave a substantial project for phase 2

[M00dy]

Originally Posted by jsbertram

the canada line TBM had its launch and extraction pits at locations that were conveniently going to become stations (olympic and waterfront respectively)

the TBM pits used to build broadway phase I will likewise become the Great Northern Way and Arbutus stations, with trains full of passengers using them every few minutes by the time phase II is OK'd.

so it's likely another new launch pit in the middle of Broadway will have to be created west of Arbutus to start the phase II TBM going to UBC, with up to 10,000 truckloads of extracted muck and spoil coming out of the launch pit and traveling across Vancouver for disposal, and a nearly equal number of truckloads of concrete, pre-built TBM rings, rails, and other components needed to build phase II

I bet that can be dealt with somehow. If they start from Great Northern Way moving west towards an intermediate receiving pit at Arbutus, they could then install a second launching structure at Arbutus to continue towards UBC.

There would be a bit of a process to bore past the Arbutus receiving pit, remove sacrificial rings, install the launch structure against the in-place rings, and then continue on.

Would allow tunnel fit-out & track to progress on phase 1.

[jsbertram]

Originally Posted by M00dy

I bet that can be dealt with somehow. If they start from Great Northern Way moving west towards an intermediate receiving pit at Arbutus, they could then install a second launching structure at Arbutus to continue towards UBC.

There would be a bit of a process to bore past the Arbutus receiving pit, remove sacrificial rings, install the launch structure against the in-place rings, and then continue on.

Would allow tunnel fit-out & track to progress on phase 1.

so how could the Arbutus TBM extraction pit get re-used for phase II as a launch pit if it has been used to hold the active Arbutus station (terminus) for phase I?

[M00dy]

Originally Posted by jsbertram

so how could the Arbutus TBM extraction pit get re-used for phase II as a launch pit if it has been used to hold the active Arbutus station (terminus) for phase I?

Are there lands drawings yet showing where the station is going? If there's more land west of the station footprint for the re-launch pit it could work to put them adjacent to each other.

Otherwise it could be done with a phased schedule, where the arbutus station starts later than the rest. (station structure could be constructed having to leave the opening for the pit until tunnel boring is complete. Finishes to start after the TBM is done.) With the project still in planning phase, the scheduling of this could still be planned for. Cost savings are likely worth it.

[MIPS]

Don't remove the TBM.
Alice was custom order and was scrapped after because it's a tough sell to flog a used TBM built for a fixed spec. No point pulling it out in a hard to service area when you can run it 200 feet past the last station and park it there until Phase 2 is ready to go. You can then reduce the size of the service pit to that of a rail switch west of the station once work is complete.

[cganuelas1995]

Originally Posted by MIPS

Don't remove the TBM.
Alice was custom order and was scrapped after because it's a tough sell to flog a used TBM built for a fixed spec. No point pulling it out in a hard to service area when you can run it 200 feet past the last station and park it there until Phase 2 is ready to go. You can then reduce the size of the service pit to that of a rail switch west of the station once work is complete.

Or, now hear me out on this one, it's kinda bold and daring and controversial.

Tunnel all the way to UBC and rough-in phase II and complete phase I.

[jsbertram]

Originally Posted by cganuelas1995

Or, now hear me out on this one, it's kinda bold and daring and controversial.

Tunnel all the way to UBC and rough-in phase II and complete phase I.

the problem is that none of the stations can be under full construction until the tbm tunnel is complete or the tunneling TBM equipment has passed their location. boring to ubc - even though the stations west of Arbutus aren't going to be built until phase II - means the other stations from GNway to Arbutus can't be opened as early, since the TBM tunnels are being used to move construction materials and debris thru them, and the site of GNWay station has to be the construction pit until the tunnels are completed.

only after the boring (to UBC or Arbutus ) is finished and all the TBM infrastructure is removed from the launch pit and the tunnels can the construction of GNWay station get under way. this is the transition station between the elevated guideways and the tunnel, so until this is (mostly) completed, none of the stations west of VCC can have trains running through them for testing or revenue service.

[officedweller]

If they were to pursue that option, they could transition to a tunnel access point for spoils removal at Arbutus, then only Arbutus station would be delayed.
I suppose if they dug another access pit west of Arbutus some of the cost advantage of combining as one long bore would disappear.

[Bdawe]

Originally Posted by officedweller

If they were to pursue that option, they could transition to a tunnel access point for spoils removal at Arbutus, then only Arbutus station would be delayed.
I suppose if they dug another access pit west of Arbutus some of the cost advantage of combining as one long bore would disappear.

Could they dump spoil into rail cars for disposal from GN Way?

[Alex Mackinnon]

Originally Posted by jsbertram

the problem is that none of the stations can be under full construction until the tbm tunnel is complete or the tunnels have passed their location. boring to ubc - even though the stations west of Arbutus aren't going to be built until phase II - means the other stations from GNway to Arbutus can't be opened as early, since the TBM tunnels are being used to move construction materials and debris thru them, and the site of GNWay station has to be the construction pit until the tunnels are completed.

only after the boring (to UBC or Arbutus ) is finished and all the TBM infrastructure is removed from the launch pit and the tunnels can the construction of GNWay station get under way. this is the transition station between the elevated guideways and the tunnel, so until this is (mostly) completed, none of the stations west of VCC can have trains running through them for testing or revenue service.

Why exactly can't they construct the stations until the tunnel is bored? I'm asking this as a tunnelling engineer.

The station boxes are quite often used for cutterhead maintenance instead of an intervention point or area of improved ground. Off the top of my head, there are a few options for doing this. You can take the TBM out of the hole on a pad and tram it across the excavation; then relaunch it. Alternatively you could excavate, install weak backfill, then -re-excavate down to the segments. I'm sure there are a few other sequences which could be performed.

[Sheba]

Originally Posted by cganuelas1995

Or, now hear me out on this one, it's kinda bold and daring and controversial.

Tunnel all the way to UBC and rough-in phase II and complete phase I.

It's also kinda not possible. A primer on how tunnelling works from our very own Evergreen extension.

• Video Link

Also we rent the machine(s) and then they're taken apart and shipped to their next project, so we can't just leave them in the ground until we're ready to start Phase 2.