I would load all the most irreplaceable bits of machinery into the shaft along with all the spare explosives turn off the pumps for a few days and then set off the charge.
How would I destroy the huge piles of coal sitting in storage? Would it burn better in one big heap, or should I make long lines of coal so as to get better access to air? Perhaps I ought to construct some sort of chamber in the pile to something, something, something?
I know this was done in the WWI epoch, to prevent naval coal stores from being captured, but I have no idea how.
Here’s a Scientific American article from 1869 that discusses the subject:
It’s a rough OCR job so it’s a bit hard to get through but I thought it interesting that there’s an article discussing the subject that’s exactly 150 years old.
It’s geared toward using coal stoves for warmth so it’s not a great answer to your question but it does discuss venting and using other materials to help get the coal fire started and maintained.
There are others that were set fire just to demonstrate that it was " inexhaustible". That still burn. Attempts to smother the fires result in new holes opening up.
A huge pile will act like underground. While it may be slower than lines, it will be exceedingly difficult to put out once it’s going.
Something like dousing an area in kerosene then lighting it would get it going.
When I was in college, my girlfriend was briefly a dispatcher at a coal company.
Pretty much every winter, a fire would start in one of the big piles of coal there, simply from spontaneous combustion. They’d go up onto the pile with bulldozers and front-end loaders to spread the coal out somewhat, which would eventually get it to go out.
The OP mentions action taken to take naval stores out of use–I can imagine two possible scenarios:
Crush it to dust, with resulting product unsuitable for ship boilers. This seems like a disaster from jump as it seems coal will catch fire if you just look at it funny, then burn VERY SLOWLY for eternity. If it doesn’t catch fire the grinding process takes forever, and you run away while 1% done. The enemy shows up to shovel away the unburnt/unground coal.
Dump it into the ocean–it’s a naval coal store, must be near water. Recovery would be difficult for the occupying power; possibly salt contamination affects even dried-out coal?
I would guess there might be something you could spray on coal to make it less useful as a fuel and/or the smoke even more noxious. A retreating military might use something like that. But if you’re on the run, you spray down the outside of a huge pile of coal and get out. The enemy scrapes off the top layer and fires up the boilers with the sweet pure coal underneath.
But the OP wants to destroy a coal MINE. The mineshaft is trivial, though it probably catches fire and burns for the next 6000+ years. As for the mined coal awaiting transport, it’s probably not on the coast so no ocean dumping. Rain and snow aren’t factors, as precipitation falls on open railroad cars without incident–except when the coal catches fire, and then burns very slowly, etc.
Maybe there’s a physical way to render piles of mined coal unusable? Say you dynamite a slope above and cover the coal in dirt, rubble, bits of trees. You would expect dirt, dust, pebbles, etc. to infiltrate the pile. That probably impacts utility, right?
I am thinking thermite. Dig holes a meter or so into the coal, at the base of the piles. Fire goes up so that has to be good. As the coal is consumed more will flow down. That has to be good.
Coal is easily recovered from the sea with no harm. Dumping several thousand tons into the sea is as troublesome as recovering it.
Yeah but I think a pile that’s purposely lit up and then left without immediate reaction is gonna be be pretty thoroughly difficult for an enemy arriving days later to control and get to where they could use it.
Assuming especially that you don’t leave operational dozers and loaders behind for them.
These days couldn’t you just bulldoze the piles into the mine shaft? Don’t bother with explosives: just let the mine fill naturally with water and put a concrete cap on it.
Wow, 50,000 tourists! That’s your clue to how to get rid of the coal - package it up in little units and get people to souvenir their own little inferno.