how the dirt doesn't collapse unto itself while being bored, no idea.

 

 

maybe some kind of shell is further inserted into it, and left off,

in order to create stability.

 

of which then, those same tracks that takes the drill, can be used to

 

send off these shells, in turn, as the drill ascends.

 

 

sequence going, drill >>> shell >>> drill >>> shell, repeating.

 

 

the shell may need to be welded to each other so, another track for

a small welding machine could also work........

 

 

 

it's just my imagination mr Musk. Technically it is plausible,

 

but is it worth the development is the question.