smallspy
Senior Member
You are incorrect in your assumption.I believe their only option is to tunnel first because it's likely too late to switch to excavating first and because I don't think you can excavate while you tunnel the same station.
I know that the plan for the Ontario line stations where they are excavating first is to push the TBM through using some other system. Therefore I'm making an assumption that it isn't possible for a TBM to transit through an excavation by using it's normal movement process, but that's a question for a tunneling engineer.
Dan