[padenot]

This is also a technique that was used more than 100 years ago for the line 4 of the Paris métro: https://www.ratp.fr/en/discover/out-and-about/culture/histor...

[llsf]

Funny that they had to freeze the ground to dig it, as it is one of the hottest line in Paris (at least 20 years ago).

[s1artibartfast]

My understanding is that the freezing is normally about stopping water intrusion long enough to drill and place concrete