Retreat Mining, Room and pillar mining, Underground Mining ...
Retreat Mining. Retreat mining is the last phase of a general kind of coal mining technique referred to as room and pillar mining. In room and pillar mining a mining machine called as "continuous miner" bores a network of chambers or "rooms" into a coal seam, leaving at the back an unexcavated pillar of coal in every room to support the roof of the mine.