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Room and pillar or pillar and stall is a variant of breast stoping. It is a mining system in which the mined material is extracted across a horizontal plane, creating horizontal arrays of rooms and pillars. To do this, "rooms" of ore are dug out while "pillars" of untouched material are left to support the roof – overburden.
In deep mining, the room and pillar or bord and pillar method progresses along the seam, while pillars and timber are left standing to support the mine roof. Once room and pillar mines have been developed to a stopping point limited by geology, ventilation, or economics, a supplementary version of room and pillar mining, termed second mining or ...
General layout of a room-and-pillar mine. Retreat mining is the removal of pillars in the underground mining technique known as room and pillar mining.. In the first phase of room and pillar mining, tunnels are advanced into the coal or ore body in a rectangular pattern resembling city streets.
Pillar. A pillar is a section of unworked coal supporting the roof. Unworked pillars of coal are left to prevent subsidence to surface features. The shaft pillar is left to prevent damage to the shafts from the workings. [1] Pit. Strictly refers to a shaft, though also used to refer to a colliery more generally. Pit brow lasses
Room and pillar : Room and pillar mining is commonly done in flat or gently dipping bedded ore bodies. Pillars are left in place in a regular pattern while the rooms are mined out. In many room and pillar mines, the pillars are taken out starting at the farthest point from the stope access, allowing the roof to collapse and fill in the stope.
Longwall mining is a form of underground coal mining where a long wall of coal is mined in a single slice (typically 0.6–6.0 m (2 ft 0 in – 19 ft 8 in) thick). The section of rock that is being mined, known as the longwall panel, is typically 3–4 km (1.9–2.5 mi) long, but can be up to 7.5 km (4.7 mi) long and 250–400 m (820–1,310 ft) wide.
“After all, service members have to follow orders, and if ordered to do something it is by definition legal and moral.” Difficult problems might arise from official recognition of moral injury: how to measure the intensity of the pain, for instance, and whether the government should offer compensation, as it does for PTSD.
Room and pillar methods are well adapted to mechanization, and are used in deposits such as coal, potash, phosphate, salt, oil shale, and bedded uranium ores. Blast mining – An older practice of coal mining that uses explosives such as dynamite to break up the coal seam, after which the coal is gathered and loaded onto shuttle cars or ...