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. Room and pillar mining proceed inner, away from the entrance of the mine. When the coal seam goes out or the mine's property line is reached, retreat mining is a method that recovers the supporting coal pillars, working from the back of the mine through the entrance, thus the word "retreat."

Room and pillar mining leaves at the rear approximately 57% of the mine's coal for hold up. This presents a sturdy financial inducement for retreat mining as a way to recoup more amount of material and expand profits. Retreat mining is an unsafe process, nevertheless, guided by severe safety regulations.

When pulling support pillars numerous methods are used to shore up mine ceilings and avert roof falls. Mobile roof supports relieve pressure on adjacent pillars during this precisely conducted mining phase. In few cases wooden cribs or hydraulic jacks are protected in place. Working from the back of the mine through the entrance, roof falls are expected in the wake of retreat mining, although collapsed parts must already be mined and left.

One of the hazards related with retreat mining is coal bursts. As steady pillars are taken out pressure augments on the walls and remaining pillars. In the similar way a stick will snap when sufficient pressure is applied, pressure may deepen to the point that a wall will blow up or a pillar will explode, shooting material into the mine. The result may be lethal to close by miners and may be intricate by localized roof falls. An enormous pillar collapse may also activate a domino effect on adjoining pillars causing catastrophic failure.

In the United States, the U.S. Department of Labor's Mine Safety and Health Administration (MSHA) is in charge for regulating mining operations comprising retreat mining. Research to get better mine safety is ongoing.