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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.
More modern room and pillar mines use a more "continuous" method, that uses machinery to simultaneously grind off rock and move it to the surface. [12] Other processes, such as backfill, where discarded tailings are unloaded into mined-out areas, [9] can be used, but are not required. Retreat mining (below) is an example of a process like this.
A Lippmann diagram is a graphical plot showing the solidus/solutus equilibrium states for a given binary solid solution (e.g., (Ba 1-x Sr x)SO 4, barite/celestite) in equilibrium with an aqueous solution containing the two substituting ions: Ba 2+ and Sr 2+ (solid solution – aqueous solution system, or SS-AS).
Continuous mining utilizes a continuous miner machine with a large rotating steel drum equipped with tungsten carbide picks that scrape coal from the seam. Operating in a "room and pillar", also known as "bord and pillar" system, where the mine is divided into a series of 20-to-30-foot (5–10 m) "rooms" or work areas cut into the coalbed—it ...
The concept of a continuum underlies the mathematical framework for studying large-scale forces and deformations in materials. Although materials are composed of discrete atoms and molecules, separated by empty space or microscopic cracks and crystallographic defects, physical phenomena can often be modeled by considering a substance distributed throughout some region of space.
A unit of length refers to any arbitrarily chosen and accepted reference standard for measurement of length. The most common units in modern use are the metric units, used in every country globally. In the United States the U.S. customary units are also in use. British Imperial units are still used for some purposes in the United Kingdom and ...
The Siilinjärvi carbonatite complex, [1] an open-pit mine owned by Yara International, in Siilinjärvi, Finland Coal strip mine in Wyoming. Surface mining, including strip mining, open-pit mining and mountaintop removal mining, is a broad category of mining in which soil and rock overlying the mineral deposit (the overburden) are removed, in contrast to underground mining, in which the ...
The general mathematical formalism used to describe and solve the Heisenberg model and certain generalizations is developed in the article on the Potts model.; In the continuum limit the Heisenberg model (2) gives the following equation of motion