You really want to be a long ways off when one goes off. And definitely not in an enclosed area. Recommend distance in miles not feet.
One interesting thing is the daisy cutters were originally used to make instant LZs in Viet Nam. ...... So using one to clear the foilage from a cave entrance, trees, bushes and all the rest, so you could direct more accurate fire into the entrance makes a lot of sense.
But I still wouldn't want to be in the same canyon when it went off. Remember what happened to the US special OPs guys when a 2,000 pounder landed 100 yards away. Now extrapolate to 15,000 pounds and above ground.
snooker
They weren't quite instant. The debris tended to form a large bank around the perimeter, and other aircraft generally had to blast hole in this barrier so troops could get in and out...