煤矿科技英语——5. BRIEF INTRODUCTION TO COAL MINING
2006 年 8 月 1 日 11:50:0
Coal mining [1] is the removal of coal from the ground. The mining method employed to extract the coal depends on the following criteria: a. seam thickness [2], b. the overburden thickness, c. the ease of removal of the overburden, d. the ease with which a shaft [3] can be sunk to reach the coal seam, e. the amount of coal extracted relative to the amount that cannot be removed, and f. the market demand for the coal. The two types of mining methods are surface mining [4] and underground mining [5]. In surface mining, the layers of rock or soil overlying a coal seam are first removed after which the coal is extracted from the exposed seam. In underground mining, a shaft is dug to reach the coal seam. Currently, underground mining accounts for approximately 60 percent of the world recovery of coal. 5-1 Surface Mining
Surface mining is used to reach coal reserves that are too shallow to be reached by other mining methods. Types of surface mining include open-pit mining [6], drift mining [7], slope mining [8], contour mining [9], and auger mining [10]. A. Open-pit Mining In open-pit mining, or strip mining, earth-moving equipment is used to remove the rocky overburden and then huge mechanical shovels [11] scoop [12] coal up from the underlying deposit. The modern coal industry has developed some of the largest industrial equipment ever made, including shovels capable of holding 290 metric tons of coal. To reach the coal, bulldozers [13] clear the vegetation and soil. Depending on the hardness and depth of the exposed sedimentary rocks, these rocky layers may be shattered with explosives. To do this, workers drill blast holes [14] into the overlying sedimentary rock, fill these holes with explosives [15], and then blast the overburden to fracture the rock. Once the broken rock is removed, coal is shoveled from the underlying deposit into giant earth-moving trucks [16] for transport [17]. B. Drift Mining Drift mining is used when a horizontal seam [18] of coal emerges at the surface on the side of a hill or mountain, and the opening [19] into the mine can be made directly into the coal seam. This type of mining is generally the easiest and most
economical type because excavation through rock is not necessary. If coal is available in this manner, it is likely to be mined. C. Slope Mining
Slope mining occurs when an inclined opening is used to tap the coal seam (or seams). A slope mine may follow the coal seam if the seam is inclined and exposed to the surface, or the slope may be driven through rock strata overlying the coal to reach a seam. Coal transportation from a slope mine can be accomplished by conveyor [20] or by track haulage [21] (using a trolley locomotive [22] if the grade is not severe) or by pulling mine cars [23] up the slope using an electric hoist [24] and steel rope [25] if the grade is steep. The most common practice is to use a belt conveyor. D. Contour Mining
Contour mining occurs on hilly or mountainous terrain, where workers use excavation equipment to cut into the hillside along its contour to remove the overlying rock and then mine the coal. The depth to which workers must cut into the hillside depends on factors such as hill slope and coal bed thickness.
E. Auger Mining
Auger mining is frequently employed in open-pit mines where the thickness of the overburden is too great for open-pit mining to be cost-effective [26]. Open-pit mining would require the lengthy and costly removal of the overburden, whereas auger mining is more efficient because it cuts through the overburden and removes the coal as it drills. In this technique, the miners drill a series of horizontal holes into the coal bed with a large auger (drill) powered by a diesel or gasoline engine [27]. These augers are typically about 60 m (200 ft) long and 0.6 to 2.1 m (2 to 7 ft) in diameter. As these enormous drills bore into the coal seam, they discharge coal like a wood drill producing wood shavings. Additional auger lengths are added as the cutting head of the auger penetrates farther into the coal. Penetration continues until the cutting head drifts into the top or bottom of the coal seam, into a previous hole, or until the maximum torque [28] (energy required to twist an object) of the auger is reached. F. Satellite Aids [29] to Surface Mining
In the late 1990s some coal mining enterprises used technologies such as the global positioning system (GPS) [30] to help guide the positioning of mining equipment. Satellites operated by the United States Air Force Space Command and leased to companies for commercial use track the position of mining equipment against a map of a mine’s topography [31]. This map uses colors to distinguish soil that should be excavated, soil that should remain in place, and areas that should be filled in. The equipment driver observes this visual information [32] on a monitor [33]
while operating the equipment. Some coal mining enterprises have used GPS to increase mining efficiency up to 30 percent.
5－2 Underground Mining Underground, or deep, mining occurs when coal is extracted from a seam without removal of the overlying strata. Miners build a shaft mine that enters the earth through a vertical opening and descends from the surface to the coal seam. In the mine, the coal is extracted from the seam by various methods, including conventional mining [34], continuous mining [35], longwall mining [36], and room-and-pillar mining [37].
A. Conventional Mining Conventional mining, also called cyclic mining, involves a sequence of operations that proceed in the following order: a. supporting the roof [38], b. ventilation [39], c. cutting [40], d. drilling [41], e. blasting [42], f. coal removal [43], and g. loading [44]. First, miners make the roof above the seam safe and stable by timbering [45] or by roof bolting [46], processes intended to prevent the roof from collapsing [47]. At the same time, they create ventilation openings so that dangerous gases [48] can escape and fresh air can reach the miners. Then one or more slots [49]—a few centimeters wide and extending for several meters into the coal—are cut along the face of the coal seam, also known as the wall face, by a large, mobile cutting machine [50]. The cut, or slot, provides easy access to the face and facilitates the breaking up of the coal, which is usually blasted from the seam by explosives known as permissible explosives. This type of explosive produces an almost flame-free explosion [51] and markedly reduces the amount of noxious fumes [52] in comparison with conventional explosives. The coal may then be transported by rubber-tired electric vehicles (shuttle cars) [53] or by chain (or belt) conveyor systems [54]. B. Continuous Mining Continuous mining involves the use of a single machine known as a continuous miner that breaks the coal mechanically and loads it for transport. This mobile machine [55] has a series of metal-studded rotating drums [56] that gouge coal from the face of the coal seam. One continuous miner can mechanically break apart about 1.8 metric tons of coal per hour. Roof support is then installed, ventilation is advanced, and the coalface [57] is ready for the next cycle. The method used to transport the coal requires the installation of mobile belt conveyors. C. Longwall Mining
The longwall mining system uses a remote-controlled [58] self-advancing support [59] in which large blocks of coal are completely extracted in a continuous operation. Hydraulic or self-advancing jacks [60], known as chocks [61], support the roof at the
immediate face as the coal is removed. As the face advances [62], the roof is allowed to collapse behind the remote-controlled, roof-building machinery [63]. Miners then remove the fallen coal. Coal recovery [64] is comparable to that attainable with the conventional or continuous mining systems.
D. Room-and-Pillar Mining Room-and-pillar mining is a means of developing a coalface and, at the same time, retaining supports for the roof. With this technique, rooms are developed from large, parallel tunnels driven into the solid coal [65], and the intervening pillars [66] of coal are used to support the roof. The percentage of coal recovered from a seam depends on the number and size of protective pillars of coal thought necessary to support the roof safely. Workers may remove some coal pillars just before closing the mine. NOTES TO THE TEXT [1] coal mining：采煤
[2] seam thickness：煤层厚度 [3] shaft：立井 [4] surface mining：地面开采
[5] underground mining：地下开采 [6] open-pit mining：露天矿开采
[7] drift mining：平峒开采
[8] slope mining：斜井开采
[9] contour mining：台阶开采
[10] auger mining：螺旋钻开采
[11] mechanical shovels：机械铲
[12] scoop：铲斗
[13] bulldozer：推土机
[14] blast holes：炮眼
[15] explosives：炸药
[16] earth-moving trucks：地面移动卡车
[17] transport：运输，输送
[18] horizontal seam：水平煤层
[19] opening：坑道
[20] conveyor：输送机
[21] track haulage：轨道运输
[22] trolley locomotive：架线式电机车
[23] mine cars：矿车
[24] electric hoist：电动提升机
[25] steel rope：钢丝绳 [26] cost-effective：成本效果
[27] gasoline engine：汽油发动机
[28] maximum torque：最大扭矩
[29] satellite aids：卫星辅助
[30] global positioning system (GPS)：地球定位系统 [31] topography：地形
[32] visual information：可视信息
[33] monitor：监控器，监视器 [34] conventional mining：传统式开采法
[35] continuous mining：连续（采煤机）式开采法
[36] longwall mining：长壁式开采法 [37] room-and-pillar mining：房柱式开采法 [38] supporting the roof：支护顶板 [39] ventilation：通风
[40] cutting：截割，掏槽
[41] drilling：钻眼
[42] blasting：爆破，放炮 [43] coal removal：出媒
[44] loading：装载 [45] timbering：木支架 [46] roof bolting：顶板锚杆支护 [47] collapsing：垮落，崩落 [48] dangerous gases：危险气体
[49] slot：槽，沟
[50] mobile cutting machine：移动式截媒机
[51] flame-free explosion：无焰爆破
[52] noxious fumes：有毒烟雾
[53] rubber-tired electric vehicles (shuttle cars)：电动胶轮车（梭车）
[54] chain (or belt) conveyor system：刮板（胶带）输送机系统 [55] mobile machine：移动式机器
[56] metal-studded rotating drums：金属双头螺栓式旋转滚筒
[57] coalface：采煤工作面
[58] remote-controlled：遥控的
[59] self-advancing support：自移式支架
[60] hydraulic or self-advancing jacks：液压或自移式千斤顶
[61] chocks：垛式（液压）支架 [62] face advances：工作面推进 [63] roof-building machinery：筑顶机械 [64] coal recovery：媒炭回收率
[65] solid coal：实体煤
[66] intervening pillars：煤房间的煤柱
GLOSSARY OF MINING TERMS——1
2006 年 8 月 2 日 17:14:0
A
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.
Acid 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. 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.
Acid mine water - Mine water that contains free sulfuric acid, mainly due to the weathering of iron pyrites.
Active workings - Any place in a mine where miners are normally required to work or travel and which are ventilated and inspected regularly.
Adit - A nearly horizontal passage from the surface by which a mine is entered and dewatered. A blind horizontal opening into a mountain, with only one entrance.
Advance - Mining in the same direction, or order of sequence; first mining as distinguished from retreat.
Air split - The division of a current of air into two or more parts.
Airway - Any passage through which air is carried. Also known as an air course.
Anemometer - Instrument for measuring air velocity.
Angle of dip - The angle at which strata or mineral deposits are inclined to the horizontal plane.
Angle 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. For dipping seams, the angle of break increases, being 35.8 from the vertical for a 40 dip. The main break occurs over the seam at an angle from the vertical equal to half the dip.
Angle of repose - The maximum angle from horizontal at which a given material will rest on a given surface without sliding or rolling.
Anticline - An upward fold or arch of rock strata.
Aquifer - A water-bearing bed of porous rock, often sandstone.
Arching - Fracture processes around a mine opening, leading to stabilization by an arching effect.
Area (of an airway) - Average width multiplied by average height of airway,
expressed in square feet.
Auger - A rotary drill that uses a screw device to penetrate, break, and then transport the drilled material (coal).
Auxiliary operations - All activities supportive of but not contributing directly to mining.
Auxiliary ventilation - Portion of main ventilating current directed to face of dead end entry by means of an auxiliary fan and tubing.
Azimuth - A surveying term that references the angle measured clockwise from any meridian (the established line of reference). The bearing is used to designate direction. The bearing of a line is the acute horizontal angle between the meridian and the line.
B
Back - The roof or upper part in any underground mining cavity.
Backfill – Mine waste or rock used to support the roof after coal removal.
Barren - 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.
Barricading - Enclosing part of a mine to prevent inflow of noxious gasses from a mine fire or an explosion.
Barrier - Something that bars or keeps out. 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.
Beam - A bar or straight girder used to support a span of roof between two support props or walls.
Beam building - The creation of a strong, inflexible beam by bolting or otherwise fastening together several weaker layers. In coal mining this is the intended basis for roof bolting.
Bearing – A surveying term used to designate direction. The bearing of a line is the acute horizontal angle between the meridian and the line. The meridian is an established line of reference. Azimuths are angles measured clockwise from any meridian.
Bearing plate - A plate used to distribute a given load. In roof bolting, the plate used between the bolt head and the roof.
Bed - A stratum of coal or other sedimentary deposit.
Belt conveyor - A looped belt on which coal or other materials can be carried
and which is generally constructed of flame-resistant material or of reinforced rubber or rubber-like substance.
Belt idler - A roller, usually of cylindrical shape, which is supported on a frame and which, in turn, supports or guides a conveyor belt. Idlers are not powered but turn by contact with the moving belt.
Belt take-up - A belt pulley, generally under a conveyor belt and inby the drive pulley, kept under strong tension parallel to the belt line. Its purpose is to automatically compensate for any slack in the belting created by start-up, etc.
Bench - One of to or more divisions of a coal seam separated by slate or formed by the process of cutting the coal.
Beneficiation - The treatment of mined material, making it more concentrated or richer.
Berm - A pile or mound of material capable of restraining a vehicle.
Binder - A streak of impurity in a coal seam.
Bit - The hardened and strengthened device at the end of a drill rod that transmits the energy of breakage to the rock. The size of the bit determines the size of the hole. A bit may be either detachable from or integral with its supporting drill rod.
Bituminous coal – A middle rank coal (between subbituminous and anthracite) formed by additional pressure and heat on lignite. Usually has a high Btu value and may be referred to as "soft coal."
Black damp - A term generally applied to carbon dioxide. Strictly speaking, it is a mixture of carbon dioxide and nitrogen. It is also applied to an atmosphere depleted of oxygen, rather than having an excess of carbon dioxide.
Blasting agent - Any material consisting of a mixture of a fuel and an oxidizer.
Blasting cap - A detonator containing a charge of detonating compound, which is ignited by electric current or the spark of a fuse. Used for detonating explosives.
Blasting circuit - Electric circuits used to fire electric detonators or to ignite an igniter cord by means of an electric starter.
Bleeder or bleeder entries - Special air courses developed and maintained as part of the mine ventilation system and designed to continuously move air-methane mixtures emitted by the gob or at the active face away from the active
workings and into mine-return air courses. Alt: Exhaust ventilation lateral.
Bolt torque - The turning force in foot-pounds applied to a roof bolt to achieve an installed tension.
Borehole - Any deep or long drill-hole, usually associated with a diamond drill.
Bottom - Floor or underlying surface of an underground excavation.
Boss - Any member of the managerial ranks who is directly in charge of miners (e.g., "shift-boss," "face-boss," "fire-boss," etc.).
Box-type magazine - A small, portable magazine used to store limited quantities of explosives or detonators for short periods of time at locations in the mine which are convenient to the blasting sites at which they will be used.
Brattice or brattice cloth - Fire-resistant fabric or plastic partition used in a mine passage to confine the air and force it into the working place. Also termed "line brattice," "line canvas," or "line curtain."
Break line - The line that roughly follows the rear edges of coal pillars that are being mined. The line along which the roof of a coal mine is expected to break.
Breakthrough - A passage for ventilation that is cut through the pillars between rooms.
Bridge carrier - A rubber-tire-mounted mobile conveyor, about 10 meters long, used as an intermediate unit to create a system of articulated conveyors between a mining machine and a room or entry conveyor.
Bridge conveyor - A short conveyor hung from the boom of mining or lading machine or haulage system with the other end attached to a receiving bin that dollies along a frame supported by the room or entry conveyor, tailpiece. Thus, as the machine boom moves, the bridge conveyor keeps it in constant connection with the tailpiece.
Brow - A low place in the roof of a mine, giving insufficient headroom.
Brushing - Digging up the bottom or taking down the top to give more headroom in roadways.
Btu – British thermal unit. A measure of the energy required to raise the temperature of one pound of water one degree Fahrenheit.
Bug dust - The fine particles of coal or other material resulting form the boring or cutting of the coal face by drill or machine.
Bump (or burst) - A violent dislocation of the mine workings which is
attributed to severe stresses in the rock surrounding the workings.
Butt cleat - A short, poorly defined vertical cleavage plane in a coal seam, usually at right angles to the long face cleat.
Butt entry - A coal mining term that has different meanings in different locations. It can be synonymous with panel entry, submain entry, or in its older sense it refers to an entry that is "butt" onto the coal cleavage (that is, at right angles to the face).
C
Cage - In a mine shaft, the device, similar to an elevator car, that is used for hoisting personnel and materials.
Calorific value - The quantity of heat that can be liberated from one pound of coal or oil measured in BTU"s.
Cannel coal - A massive, non-caking block coal with a fine, even grain and a conchoidal fracture which has a high percentage of hydrogen, burns with a long, yellow flame, and is extremely easy to ignite.
Canopy - A protective covering of a cab on a mining machine.
Cap - A miner"s safety helmet. Also, a highly sensitive, encapsulated explosive that is used to detonate larger but less sensitive explosives.
Cap block - A flat piece of wood inserted between the top of the prop and the roof to provide bearing support.
Car - A railway wagon, especially any of the wagons adapted to carrying coal, ore, and waste underground.
Car-dump - The mechanism for unloading a loaded car.
Carbide bit - More correctly, cemented tungsten carbide. A cutting or drilling bit for rock or coal, made by fusing an insert of molded tungsten carbide to the cutting edge of a steel bit shank.
Cast - A directed throw; in strip-mining, the overburden is cast from the coal to the previously mined area.
Certified - Describes a person who has passed an examination to do a required job.
Chain conveyor - A conveyor on which the material is moved along solid pans (troughs) by the action of scraper crossbars attached to powered chains.
Chain pillar - The pillar of coal left to protect the gangway or entry and the parallel airways.
Check curtain - Sheet of brattice cloth hung across an airway to control the passage of the air current.
Chock - Large hydraulic jacks used to support roof in longwall and shortwall mining systems.
Clay vein - A body of clay-like material that fills a void in a coal bed.
Cleat - The vertical cleavage of coal seams. The main set of joints along which coal breaks when mined.
Clean Air Act Amendments of 1990 – A comprehensive set of amendments to the federal law governing the nation"s air quality. The Clean Air Act was originally passed in 1970 to address significant air pollution problems in our cities. The 1990 amendments broadened and strengthened the original law to address specific problems such as acid deposition, urban smog, hazardous air pollutants and stratospheric ozone depletion.
Clean Coal Technologies – A number of innovative, new technologies designed to use coal in a more efficient and cost-effective manner while enhancing environmental protection. Several promising technologies include: fluidized-bed combustion, integrated gasification combined cycle, limestone injection multi-stage burner, enhanced flue gas desulfurization (or "scrubbing"), coal liquefaction and coal gasification.
Coal - A solid, brittle, more or less distinctly stratified combustible carbonaceous rock, formed by partial to complete decomposition of vegetation; varies in color from dark brown to black; not fusible without decomposition and very insoluble.
Coal dust - Particles of coal that can pass a No. 20 sieve.
Coal Gasification – The conversion of coal into a gaseous fuel.
Coal mine - An area of land and all structures, facilities, machinery, tools, equipment, shafts, slopes, tunnels, excavations, and other property, real or personal, placed upon, under, or above the surface of such land by any person, used in extracting coal from its natural deposits in the earth by any means or method, and the work of preparing the coal so extracted, including coal preparation facilities. British term is "colliery".
Coal reserves - Measured tonnages of coal that have been calculated to occur in a coal seam within a particular property.
Coal washing – The process of separating undesirable materials from coal based on differences in densities. Pyritic sulfur, or sulfur combined with iron, is
heavier and sinks in water; coal is lighter and floats.
Coke – A hard, dry carbon substance produced by heating coal to a very high temperature in the absence of air.
Collar - The term applied to the timbering or concrete around the mouth or top of a shaft. The beginning point of a shaft or drill hole at the surface.
Colliery - British name for coal mine.
Column flotation – A precombustion coal cleaning technology in which coal particles attach to air bubbles rising in a vertical column. The coal is then removed at the top of the column.
Comminution - The breaking, crushing, or grinding of coal, ore, or rock.
Competent rock - Rock which, because of its physical and geological characteristics, is capable of sustaining openings without any structural support except pillars and walls left during mining (stalls, light props, and roof bolts are not considered structural support).
Contact - The place or surface where two different kinds of rocks meet. Applies to sedimentary rocks, as the contact between a limestone and a sandstone, for example, and to metamorphic rocks; and it is especially applicable between igneous intrusions and their walls.
Continuous miner - A machine that constantly extracts coal while it loads it. This is to be distinguished from a conventional, or cyclic, unit which must stop the extraction process in order for loading to commence.
Contour - An imaginary line that connects all points on a surface having the same elevation.
Conventional mining – The first fully-mechanized underground mining method involving the insertion of explosives in a coal seam, the blasting of the seam, and the removal of the coal onto a conveyor or shuttle car by a loading machine.
Conveyor - An apparatus for moving material from one point to another in a continuous fashion. This is accomplished with an endless (that is, looped) procession of hooks, buckets, wide rubber belt, etc.
Core sample – A cylinder sample generally 1-5" in diameter drilled out of an area to determine the geologic and chemical analysis of the overburden and coal.
Cover - The overburden of any deposit.
Creep - The forcing of pillars into soft bottom by the weight of a strong roof.
In surface mining, a very slow movement of slopes downhill.
Crib - A roof support of prop timbers or ties, laid in alternate cross-layers, log-cabin style. It may or may not be filled with debris. Also may be called a chock or cog.
Cribbing - The construction of cribs or timbers laid at right angles to each other, sometimes filled with earth, as a roof support or as a support for machinery.
Crop coal - Coal at the outcrop of the seam. It is usually considered of inferior quality due to partial oxidation, although this is not always the case.
Crossbar - The horizontal member of a roof timber set supported by props located either on roadways or at the face.
Crosscut - A passageway driven between the entry and its parallel air course or air courses for ventilation purposes. Also, a tunnel driven from one seam to another through or across the intervening measures; sometimes called "crosscut tunnel", or "breakthrough". In vein mining, an entry perpendicular to the vein.
Cross entry - An entry running at an angle with the main entry.
Crusher - A machine for crushing rock or other materials. Among the various types of crushers are the ball mill, gyratory crusher, Handsel mill, hammer mill, jaw crusher, rod mill, rolls, stamp mill, and tube mill.
Cutter; Cutting machine - A machine, usually used in coal, that will cut a 10- to 15-cm slot. The slot allows room for expansion of the broken coal. Also applies to the man who operates the machine and to workers engaged in the cutting of coal by pick or drill.
Cycle mining - A system of mining in more than one working place at a time, that is, a miner takes a lift from the face and moves to another face while permanent roof support is established in the previous working face.
GLOSSARY OF MINING TERMS——2
2006 年 8 月 2 日 16:17:0
D
Demonstrated reserves – A collective term for the sum of coal in both
measured and indicated resources and reserves.
Deposit - Mineral deposit or ore deposit is used to designate a natural occurrence of a useful mineral, or an ore, in sufficient extent and degree of concentration to invite exploitation.
Depth - The word alone generally denotes vertical depth below the surface. In the case of incline shafts and boreholes it may mean the distance reached from the beginning of the shaft or hole, the borehole depth, or the inclined depth.
Detectors - Specialized chemical or electronic instruments used to detect mine gases.
Detonator - A device containing a small detonating charge that is used for detonating an explosive, including, but not limited to, blasting caps, exploders, electric detonators, and delay electric blasting caps.
Development mining - Work undertaken to open up coal reserves as distinguished from the work of actual coal extraction.
Diffusion - Blending of a gas and air, resulting in a homogeneous mixture. Blending of two or more gases.
Diffuser fan - A fan mounted on a continuous miner to assist and direct air delivery from the machine to the face.
Dilute - To lower the concentration of a mixture; in this case the concentration of any hazardous gas in mine air by addition of fresh intake air.
Dilution - The contamination of ore with barren wall rock in stopping.
Dip - The inclination of a geologic structure (bed, vein, fault, etc.) from the horizontal; dip is always measured downwards at right angles to the strike.
Dragline – A large excavation machine used in surface mining to remove overburden (layers of rock and soil) covering a coal seam. The dragline casts a wire rope-hung bucket a considerable distance, collects the dug material by pulling the bucket toward itself on the ground with a second wire rope (or chain), elevates the bucket, and dumps the material on a spoil bank, in a hopper, or on a pile.
Drainage - The process of removing surplus ground or surface water either by artificial means or by gravity flow.
Draw slate - A soft slate, shale, or rock from approximately 1 cm to 10 cm thick and located immediately above certain coal seams, which falls quite easily when the coal support is withdrawn.
Drift - A horizontal passage underground. A drift follows the vein, as
distinguished from a crosscut that intersects it, or a level or gallery, which may do either.
Drift mine – An underground coal mine in which the entry or access is above water level and generally on the slope of a hill, driven horizontally into a coal seam.
Drill - A machine utilizing rotation, percussion (hammering), or a combination of both to make holes. If the hole is much over 0.4m in diameter, the machine is called a borer.
Drilling - The use of such a machine to create holes for exploration or for loading with explosives.
Dummy - A bag filled with sand, clay, etc., used for stemming a charged hole.
Dump - To unload; specifically, a load of coal or waste; the mechanism for unloading, e.g. a car dump (sometimes called tipple); or, the pile created by such unloading, e.g. a waste dump (also called heap, pile, tip, spoil pike, etc.).
E
Electrical grounding - To connect with the ground to make the earth part of the circuit.
Entry - An underground horizontal or near-horizontal passage used for haulage, ventilation, or as a mainway; a coal heading; a working place where the coal is extracted from the seam in the initial mining; same as "gate" and "roadway," both British terms.
Evaluation - The work involved in gaining a knowledge of the size, shape, position and value of coal.
Exploration - The search for mineral deposits and the work done to prove or establish the extent of a mineral deposit. Alt: Prospecting and subsequent evaluation.
Explosive - Any rapidly combustive or expanding substance. The energy released during this rapid combustion or expansion can be used to break rock.
Extraction - The process of mining and removal of cal or ore from a mine.
F
Face – The exposed area of a coal bed from which coal is being extracted.
Face cleat - The principal cleavage plane or joint at right angles to the stratification of the coal seam.
Face conveyor - Any conveyor used parallel to a working face which delivers coal into another conveyor or into a car.
Factor of safety - The ratio of the ultimate breaking strength of the material to the force exerted against it. If a rope will break under a load of 6000 lbs., and it is carrying a load of 2000 lbs., its factor of safety is 6000 divided by 2000 which equals 3.
Fall - A mass of roof rock or coal which has fallen in any part of a mine.
Fan, auxiliary - A small, portable fan used to supplement the ventilation of an individual working place.
Fan, booster - A large fan installed in the main air current, and thus in tandem with the main fan.
Fan signal - Automation device designed to give alarm if the main fa...
