Ok so i got to the abandoned mine killed the merc outside of it and the mine shaft blew now i have no idea what to do.

If I remember it right, if you blow the mine entrace, you have to use the front door, which is... I don't remember where, but it shouldn't be very difficult to find out.

I believe you can either turn off the fan in this sector (likely from another sector, my memories of UB are fuzzy at best) or you can blast the fan. Stops it permanently, but you'll alert the guards beyond.