Partial tunnel collapse at Snowy 2.0 construction site raises fresh safety concerns, page-7

TBM's are not designed to tunnel in soft ground.
The old fashioned bench and heading tunnelling technique should be used.
Unfortunately our tunnellers these days like to push buttons instead of manually operating air drills etc.
And whoever committed to the expense of a TBM without thorough and extensive pre investigation drilling to determine the rock (or lack of it), should be held accountable.
Or maybe Turnbull knew best.
I suspect that's the case.