[wastoute]

I used to work in Potash mines which are very similar to coal mines. When you mine soft rock in a seam you leave square “pillars” to support the roof or “overhead” as miners call it. As you retreat out of an area it is common to “pull pillars”. You can only pull every third or so. If you get too greedy...

I have seen an area where pillars had been pulled 40 years before and the stresses on the rock that was left did astonishing things. The floor heaves up in arches, the pillars bow out. It is spooky. Could you imagine a whole field of pillars just crushing in an instant? Ouch!

[mmanager]

Finally someone here on FR understands what is going on. Great comment.

I have looked at the mine maps where the ‘event took place’. IMSHA approved Murray’s plan. I just hope he followed the plan. Imagine looking down on a map with two blocks of coal, 1000 feet wide, seperated by a 300 ft. barrier plus development of 150 feet in the main entry. This is one side and the other is the same with the mains in the middle. So you have the mains in the middle (~150 ft) 300 ft. of barrier on each side and 1000 ft. of mined out longwall (gob) caved in material on each side of the mains.

They were permitted as I understand to pull some of the supporting pillars next to the mains along with mining into the 300 ft barrier on each side.

You are correct with your remarks. This is high coal with a lot of cover (mountain on top).

I pray that Murray followed the approved mine plan.

[mmanager]

One other note, the ribs are exploding not the top. There is a very thick seam of limestone strata supporting the roof. That is why the rib is blowing out. A natural bomb without the fire.

[Eric in the Ozarks]

I was in the former Galatia Mine in S. Illinois when it was owned by Kerr McGee. They were simultaneously mining the Number 5 and Number 6 seams, about 180 feet apart and blending the two coals to meet sulfur limits at Union Electric. The mine plan was amazing to me because it called for the pillars to line up, above one another. When pillars were pulled in one section, the pillars were also pulled more or less simultaneously.