@TWISM and @Polyphemus: I have moved your posts to a new topic. The previous topic is archived and had not had a reply for close to a year. Best to start a fresh discussion on this to make it easier to find and continue with.
For reference:
Archived topic - Anyone had success with underground bases? - #33 by floyd_26 (Atlas Rises / pre-Next)
Related - Base Building Fiasco