If you read the CDG newsletter, you'll often find reports from projects in mines, so I would suggest that there is no taboo.
When I lived closer to a mining area, I spent more time in mines. Now I live closer to a caving area I spend more time in caves.
So long as it's underground I'm happy.
I have a few unfinished projects in Weardale/ Nenthead, one involving diving, but it's too far to travel, so all my active projects are in caves (except one that isn't, neither is it in a mine...).
What have you got in mind? Are you looking for support? Looking to sound out ideas? Or anything else?