Longwall mining is a type of underground coal mining where a extended wall (normally about 250-400 m long) of coal is mined in a sole slice (classically 1-2 m thick). The longwall "panel" (the slab of coal that is being mined) is normally 3-4 km long and 250-400 m broad.
The gate road all along one side of the block is known the maingate or headgate; the road on the other side is known as the tailgate. These gate roads have been before urbanized by incessant miner units, as the longwall itself is not competent of the first development. The end of the block that comprises the longwall equipment is known as the face. The other end of the block is normally one of the major travel roads of the mine. The cavity at the back the longwall is known as the goaf, goff or gob.
Fresh air goes up the main gate, athwart the face, and then down the tail gate. Once precedent the face the air is no more fresh air, except return air taking away coal dust and mine gases like methane, carbon dioxide, relying on the geology of the coal. Return air is taken out by ventilation fans mounted on the surface. A series of seals are uprighted as mining progresses to uphold goaf gas levels.
Characteristically to shun coal in the goaf spontaneously combusting, goaf gases are allowable to build up so as to eliminate oxygen from the goafed area. This means that there is an explosive goaf fringe among the face and the goaf at all times wanting steady monitoring.
Merits of Long Mining Comprises the Following:
enhanced resource recovery (about 80% contrasted with about 60
percent for Room and pillar method)