What is Retreat Mining?
After the “easy” material has been mined, they start at the rear of the mine and remove most or all of the pillars of minable material that had to be left to hold the mine roof up in the original mining operation. Since there is nothing left to mine once that is removed and no reason to go back in, they can remove it and leave the roof unstable or let it collapse behind them as they “back out” of the mine.
Retreat mining is the last phase of a common type of coal mining technique referred to as room and pillar mining. In room and pillar mining a mining machine known as a “continuous miner” bores a network of chambers or “rooms” into a coal seam, leaving behind an unexcavated pillar of coal in each room to support the roof of the mine. Room and pillar mining advances inward, away from the entrance of the mine. When the coal seam runs out or the mine’s property line is reached, retreat mining is a process that recovers the supporting coal pillars, working from the back of the mine towards the entrance, hence the word “retreat.
