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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.
Underground soft-rock mining is a group of underground mining techniques used to extract coal, oil shale, potash, and other minerals or geological materials from sedimentary ("soft") rocks. [1] Because deposits in sedimentary rocks are commonly layered and relatively less hard, the mining methods used differ from those used to mine deposits in ...
Historically in the U.S. the prevalent method of coal acquisition was underground mining which is very labor-intensive. In MTR, through the use of explosives and large machinery, more than two and a half times as much coal can be extracted per worker per hour than in traditional underground mines, [ 21 ] thus greatly reducing the need for workers.
Coal mining. Coal mining is the process of extracting coal from the ground or from a mine. Coal is valued for its energy content and since the 1880s has been widely used to generate electricity. Steel and cement industries use coal as a fuel for extraction of iron from iron ore and for cement production.
Drift mining is either the mining of an ore deposit by underground methods, or the working of coal seams accessed by adits driven into the surface outcrop of the coal bed. [1] A drift mine is an underground mine in which the entry or access is above water level and generally on the slope of a hill, driven horizontally into the ore seam. [2]
At the start of the 19th century, coal mining was almost all bituminous coal. In 1810, 176,000 short tons of bituminous coal, and 2,000 tons of anthracite coal, were mined in the United States. American coal mining grew rapidly in the early 1820s, doubling or tripling every decade. Anthracite mining overtook bituminous coal mining in the 1840s ...
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. Pillars are left between tunnels to support the ...
In 1987 Wyoming became the largest coal producing state. It uses strip mining exclusively. Wyoming's coal reserves total about 69.3 billion short tons (62.9 Pg), or 14.2% of the U.S. coal reserve. [69] In 2008, competition was intense in the US coal mining industry with some U.S. mines approaching the end of their useful life (mine closure).