Good to realize that the public is becoming aware that a TBM isn't the be-all end-all in tunnel construction.
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Originally Posted by Gordon
If the Broadway subway was to be done Cut and Cover , could the trench be done in sections so as to not have all of Broadway closed for the duration of construction?
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It would likely be under 10th Ave. which is not as sensitive to road closures.
They just need to make sure the route is determined based on sound engineering practice, not some politician saying the "Broadway Line" must be under Broadway.
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Originally Posted by queetz@home
I guess ultimately, this could be the reason why cut and cover was chosen (likely behind the scenes with collaboration with Falcon) for the Canada Line...they needed it built ASAP and you have more control over that method. As we now learn with Evergreen Line, tunneling has a lot of uncertainty, and the Canada Line could have been delayed for the Owelympics...  |
That's one of the reasons.
The other was that because of Little Mountain (QE Park) being a big granite volcanic cone, they would have needed a different type of TBM (not just cutter heads) for that segment - adding cost.
The need to build it ASAP after delays from environmental challenges and funding refusals at Metro Vancouver led to the switch from sequential precast segments being used to cast-in-place concrete. The cast-in-place method allowed them to work at multiple fronts. The sequential precast method would have been comparable to a TBM (or elevated gantry crane) - working from one end adding sequentially from one front.
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