pretty imressive. I heard that it hasn't been a smooth ride all along. I heard they had to change a lot of disc cutters along the way. Like I heard 20 disc cutter every single  day had to be replaced!

When I was visiting Bergen in 2017 for WTC, a Norwegian professor told me the same thing about the disc usage. Anyways they made it!  Let's look at the final result. Quite an accomplishment.

why tubes close each other so much? Normal speaking there must be at least two diameter distance between two tubes. For example if diameter of each tube is 12 meters, they must be 24 meters away from each other. Otherwise TBMs distort the working of each other. No?

@Paolo As far as I know, the disc cutters did a good job in Follo.

Another great job by Acciona. Spanish are the kings of tunnelling!

The machine is Herrenknecht. But anybody know what Disc cutters they used? Also Herrenknecht?

Maybe the disc cutters were not Herrenknecht. You know how it works. First x meters you use disc cutters of the TBM manufacturer. So maybe first x meter they used Herrenknecht disc cutters and then switched to an after-market provider like EBERK or PALMIERI. I think it is Palmieri because Palmieri website lists Follo line as one of their references: https://www.palmierigroup.com/en/references/#slide1/slide6

To be sure maybe someone who worked in the project comments?