nnel- A horizontal, or near-horizontal, underground passage, entry, or haulageway, that is open to the surface at both ends. A tunnel (as opposed to an adit) must pass completely through a hill or mountain.U
Ultimate analysis- Precise determination, by chemical means, of the elements and compounds in coal.
Undercut- To cut below or undermine the coal face by chipping away the coal by pick or mining machine. In some localities the terms "undermine" or "underhole" are used.
Underground mine�C Also known as a "deep" mine. Usually located several hundred feet below the earth's surface, an underground mine's coal is removed mechanically and transferred by shuttle car or conveyor to the surface.
Underground station- An enlargement of an entry, drift, or level at a shaft at which cages stop to receive and discharge cars, personnel, and material. An underground station is any location where stationary electrical equipment is installed. This includes pump rooms, compressor rooms, hoist rooms, battery-charging rooms, etc.
Unit train�C A long train of between 60 and 150 or more hopper cars, carrying only coal between a single mine and destination.
Universal coal cutter- A type of coal cutting machine which is designed to make horizontal cuts in a coal face at any point between the bottom and top or to make shearing cuts at any point between the two ribs of the place. The cutter bar can be twisted to make cuts at any angle to the horizontal or vertical.
Upcast shaft- A shaft through which air leaves the mine.
V
Valuation- The act or process of valuing or of estimating the value or worth; appraisal.
Velocity- Rate of airflow in lineal feet per minute.
Ventilation- The provision of a directed flow of fresh and return air along all underground roadways, traveling roads, workings, and service parts.
Violation- The breaking of any state or federal mining law.
Virgin- Unworked; untouched; often said of areas where there has been no coal mining.
Void- A general term for pore space or other reopenings in rock. In addition to pore space, the term includes vesicles, solution cavities, or any openings either primary or secondary.
Volatile matter- The gaseous part, mostly hydrocarbons, of coal.
W
Waste- That rock or mineral which must be removed from a mine to keep the mining scheme practical, but which has no value.
Water Gauge (standard U-tube)- Instrument that measures differential pressures in inches of water.
Wedge- A piece of wood tapering to a thin edge and used for tightening in conventional timbering.
Weight- Fracturing and lowerin
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