Odd Structure At Hamilton's Point

On August 16, 2011, I was waiting at Hamilton's Point for a Cumbres-bound freight, and spent a little time snooping around. I found this little shack -
This is just off the track, down the hill a little bit, at the rock outcropping at the west end of the Hamilton's Point rocks.
At the east end of the Hamilton's Point area was found this small tunnel -
The tunnel goes in about 25 - 30 ft, then "Tees" left and right about 10 ft each way.
If anyone has information about this shack and the tunnel, I would be appreciative. One suggestion I heard was the shack was for dynamite to break up fallen rock - reasonable, given the location.
A closer view -This is just off the track, down the hill a little bit, at the rock outcropping at the west end of the Hamilton's Point rocks.
At the east end of the Hamilton's Point area was found this small tunnel -
The tunnel goes in about 25 - 30 ft, then "Tees" left and right about 10 ft each way.
If anyone has information about this shack and the tunnel, I would be appreciative. One suggestion I heard was the shack was for dynamite to break up fallen rock - reasonable, given the location.