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.
0 kommentar(er)
