Azimuths are angles measured clockwise from any meridian.īearing plate - A plate used to distribute a given load. The meridian is an established line of reference. The bearing of a line is the acute horizontal angle between the meridian and the line. In coal mining this is the intended basis for roof bolting.īearing – A surveying term used to designate direction. Barrier pillars are solid blocks of coal left between two mines or sections of a mine to prevent accidents due to inrushes of water, gas, or from explosions or a mine fire.īeam - A bar or straight girder used to support a span of roof between two support props or walls.īeam building - The creation of a strong, inflexible beam by bolting or otherwise fastening together several weaker layers. The bearing of a line is the acute horizontal angle between the meridian and the line.īack - The roof or upper part in any underground mining cavity.īackfill – Mine waste or rock used to support the roof after coal removal.īarren - Said of rock or vein material containing no minerals of value, and of strata without coal, or containing coal in seams too thin to be workable.īarricading - Enclosing part of a mine to prevent inflow of noxious gasses from a mine fire or an explosion.īarrier - Something that bars or keeps out. The bearing is used to designate direction. The main break occurs over the seam at an angle from the vertical equal to half the dip.Īngle of repose - The maximum angle from horizontal at which a given material will rest on a given surface without sliding or rolling.Īnticline - An upward fold or arch of rock strata.Īquifer - A water-bearing bed of porous rock, often sandstone.Īrching - Fracture processes around a mine opening, leading to stabilization by an arching effect.Īrea (of an airway) - Average width multiplied by average height of airway, expressed in square feet.Īuger - A rotary drill that uses a screw device to penetrate, break, and then transport the drilled material (coal).Īuxiliary operations - All activities supportive of but not contributing directly to mining.Īuxiliary ventilation - Portion of main ventilating current directed to face of dead end entry by means of an auxiliary fan and tubing.Īzimuth - A surveying term that references the angle measured clockwise from any meridian (the established line of reference). For dipping seams, the angle of break increases, being 35.8° from the vertical for a 40° dip. Also known as an air course.Īnemometer - Instrument for measuring air velocity.Īngle of dip - The angle at which strata or mineral deposits are inclined to the horizontal plane.Īngle of draw - In coal mine subsidence, this angle is assumed to bisect the angle between the vertical and the angle of repose of the material and is 20° for flat seams. A blind horizontal opening into a mountain, with only one entrance.Īdvance - Mining in the same direction, or order of sequence first mining as distinguished from retreat.Īir split - The division of a current of air into two or more parts.Īirway - Any passage through which air is carried. The precursors or chemical forerunners of acid rain formation result from both natural sources, such as volcanoes and decaying vegetation, and man-made sources, primarily emissions of sulfur and nitrogen oxides resulting from fossil fuel combustion.Īcid mine water - Mine water that contains free sulfuric acid, mainly due to the weathering of iron pyrites.Īctive workings - Any place in a mine where miners are normally required to work or travel and which are ventilated and inspected regularly.Īdit - A nearly horizontal passage from the surface by which a mine is entered and dewatered. Abutment - In coal mining, (1) the weight of the rocks above a narrow roadway is transferred to the solid coal along the sides, which act as abutments of the arch of strata spanning the roadway and (2) the weight of the rocks over a longwall face is transferred to the front abutment, that is, the solid coal ahead of the face and the back abutment, that is, the settled packs behind the face.Īcid deposition or acid rain – Refers loosely to a mixture of wet and dry "deposition" (deposited material) from the atmosphere containing higher than "normal" amount of nitric and sulfuric acids.
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