Room and pillar mining

Room and pillar or pillar and stall 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. Calculating the size, shape, and position of pillars is a complicated procedure, and an area of active research. The technique is usually used for relatively flat-lying deposits, such as those that follow a particular stratum. Compared to other underground mining techniques, room and pillar mining is relatively simple, lends itself to mechanization, and can reduce the risk of surface subsidence. But recovery and profits are lowered by the need to leave portions of ore in the pillars. Room and pillar mining was one of the earliest methods used, although the manpower needed has sharply declined.

Process

Stage 1—exploration and development Planning for the development of room and pillar mines operates in much the same way as other mining methods, and begins with establishing ownership of the mine. Then the geology of the mine must be analysed, as this will determine factors like the lifespan of the mine, the production requirements, and the cost to develop and maintain. To prevent this from happening, the mine is divided into areas or panels. Other processes, such as backfill, where discarded tailings are unloaded into mined-out areas, Sometimes retreat mining is not used and the underground space is repurposed as climate controlled storage or office space instead. Stage 3—maintenance and remediation Many room and pillar mines have been abandoned for as long as 100 years. This drastically increases the risk of subsidence unless properly maintained, however, maintenance does not often occur. == History ==

History

Room and pillar mining is one of the oldest mining methods. Early room and pillar mines were developed more or less at random, with pillar sizes determined empirically and headings driven in whichever direction was convenient. Room and pillar mining was in use throughout Europe as early as the 13th century, and the United States since the late 18th century. It is still in use throughout the US, Many salt mines use room and pillar layouts. The Sifto salt mine in Goderich, Ontario, the largest in the world, was opened in 1959. It taps a salt bed thick below the surface, mostly under Lake Huron. The Cargill salt mine below the surface, mostly under Lake Erie at Cleveland, Ohio is similar. == Modern use ==

Modern use

Modern room and pillar mines can be few and far between. This is due to many factors, including the dangers to miners associated with subsidence, increasing use of other methods with more mechanization, and the decreasing cost of surface mining. Advantages Room and pillar mining is not particularly dependent on the depth of the deposit. At particularly deep depths, room and pillar mining can be more cost effective compared to strip mining due to the fact that significantly less overburden needs to be removed. but subsidence of abandoned mines can be hazardous to infrastructure above and nearby. Significant amount of coal is left on the pillars as roof support. == See also ==

Source: Wikipedia ↗

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