Room and Pillar - Retreat Mining

Retreat Mining

Retreat mining is often the final stage of room and pillar mining. Once a deposit has been exhausted using this method, the pillars that were left behind initially are removed, or "pulled", retreating back towards the mine's entrance. After the pillars are removed, the roof (or back) is allowed to collapse behind the mining area. Pillar removal must occur in a very precise order in order to reduce the risks to workers, due to the high stresses placed on the remaining pillars by the abutment stresses of the caving ground.

Retreat mining is a particularly dangerous form of mining: according to the Mine Safety and Health Administration (MSHA), pillar recovery mining has been historically responsible for 25% of American coal mining deaths, even though it represents only 10% of the coal mining industry. Apparently retreat mining was in use at the Crandall Canyon Mine and may have caused the August 2007 collapse which trapped six miners. On November 21, 2007, the mine was sealed, entombing the deceased miners. The bureau of land management says retreat mining was being used. Robert E. Murray, CEO of Murray Energy (owner of the mine), says the technique was not being used at Crandall Canyon.