Some years ago I was part of a group of postgraduate students being shown around a working coal mine in the north of England. We were several hundred feet underground and several miles from the pit shaft. Our guides decided to take us on a short cut between two tunnels. This involved us crawling about 30-40 feet through a very low and narrow tunnel. Some parts of the tunnel were high enough for us to proceed on all fours, other parts involved us crawling on our bellies. There were wooden pit props on both sides of us.
I was about half way through the tunnel, with several people behind me, when the chap immediately in front of me, a stout fellow called Farquhar, got stuck. As soon as he got stuck he seemed to expand so that he got even more stuck. I'm not particularly claustrophobic, but after a while I became quite conscious of all the rock above me and began to contemplate taking out my pocket knife and whittling Farquhar down to a size where he would fit.
There were another couple of interesting incidents during this mine tour. Every few hundred feet along the mine tunnels there were hollow beams filled with very fine white dust. I think the idea was that in the event of an underground explosion these beams would be tipped over and the fine dust would create a cloud in the tunnel that would prevent fire spreading. being middle class we were quite a bit taller than the dwarfish miners who were guiding us and, of course, somebody [ok, it was me] hit their head against one of the beams. The fine white dust rapidly expanded to fill the tunnel and coat us all. The miners found this very amusing. We must've made quite an unusual sight as we trudged along the tunnels. Several tall Snow Whites accompanied by laughing dwarves.
The final interesting feature of the visit was a conveyor belt ride. The mine had been working for many years and the coal faces were several miles away from the main pit shaft. There were conveyor belts running from the shaft to the coal faces and we used one of these to ride out and back. Each of us had to lie on a narrow table next to the conveyor belt, and on a signal from one of the miners, roll onto the conveyor belt, which then whisked us rapidly off into the darkness. It was one of the most thrilling rides that I have had; though getting off at the other end was a bit painful. The conveyor belt never stopped whatever happened and to get off we had to pick the ideal moment to roll off to one side. Easy enough if you were a miner and did it every day. We didn't find it all that easy, and our screams and curses provide the miners with even more entertainment.