That one time I toured an operating underground coal mine
This isn’t my video but when I saw it on Imgur it reminded me of the time I got to tour an underground long wall mining operation. It was fascinating! This was a Peabody coal mine in Eastern KY. My dad was an executive for Peabody (when coal was considered a good thing) and I got the tour in 1995, before he retired.
As you can see in the video, the cutting head moves horizontally chewing the coal seam onto conveyers which take it to the surface. The mine was several hundred feet underground with relatively tall ceilings; you could stand up straight. The floor was covered in a white powder which prevents sparks and the ceiling of the underground ‘streets’ was bolted every few inches. Water was constantly spraying in the cutting area in an effort to reduce airborne dust.
The cutting head and miners operated under a steel clam shell. Think of 10’ tall, 150’ thick letter C with the cutting head running along open part of the C and the roof resting on the top of the C. After the cutting head had made several passes, the entire line would mechanically advance toward the coal seam (ie move toward the open part of the C) leaving the unsupported roof to collapse behind the machine. Solid pillars and posts of coal were left standing in strategic locations to facilitate transport. The sheer power and awesome efficiency of the machine was awe inspiring. Although the roof collapse would fall 10’ or more at the level of the coal seam, this collapse would take many days to progress all the way to the surface at which point the subsidence would 2-3 feet. I’m told you could sit on a lawn chair above the mine and watch the subsidence make its way across the field like a reverse wave.
