I wonder how much quicker it would be to just bore the outer parts. Like creating a dowel in wood. The big stone dowel would have to be removed but atleast it would bore faster presumably. Downside would obviously be that you can't lay the tunnel surrounding at the same time.
Dear free spirit 1, It’s all about a smart knowledge combination regarding the different key parameters of a project: ground geology, machine capacities, piloting experience, professional project management and… teamwork. According to our experience, good performances are linked to a good teamwork. Best regards, Herrenknecht AG
