Stages In The Life Of A Mine 1j524y

STAGES IN THE LIFE OF A MINE

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STAGES IN THE LIFE OF A MINE The overall sequence of activities in modern mining is often compared with the five stages in the life of a mine: prospecting, exploration, development, exploitation, and reclamation. Prospecting and exploration, precursors to actual mining, are linked and sometimes combined. Geologists and mining engineers often share responsibility for these two stages. Likewise, development and exploitation are closely related stages; they are usually considered to constitute mining proper and are the main province of the mining engineer. Reclamation has been added to these stages since the first edition, Closure and reclamation of the mine site has become a necessary part of the mine life cycle because of the demands of society for a cleaner environment and stricter laws regulating the abandonment of a mine. The overall process of developing a mine with the future uses of the land in mind is termed sustainable development.

PROSPECTING Prospecting, the first stage in the utilization of a mineral deposit. It is the search for ores or other valuable minerals (coal or non-metallic). Because mineral deposits may be located either at or below the surface of the earth, both direct and indirect prospecting techniques are employed. The direct method of discovery, normally limited to surface deposits, consists of visual examination of either the exposure (outcrop) of the deposit or the loose fragments that have weathered away from the outcrop. Geologic studies of the entire area augment this simple, direct technique. By means of aerial photography, geologic maps, and structural assessment of an area, the geologist gat hers evidence by direct methods to locate mineral deposits. Precise mapping and structural analysis plus microscopic studies of samples also enable the geologist to locate the hidden as well as surface mineralization. 1

BY: IZHAR MITHAL JISKANI

STAGES IN THE LIFE OF A MINE

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EXPLORATION The second stage in the life of a mine, exploration, determines as accurately as possible the size and value of a mineral deposit, utilizing techniques similar to but more deeply than those used in prospecting. The line of demarcation between prospecting and exploration is not sharp; in fact, a distinction may not be possible in some cases. Exploration generally shifts to surface and subsurface locations, using a variety of measurements to obtain a more positive picture of the extent and grade of the ore body. Representative samples may be subjected to chemical, metallurgical, X ray, spectrographic or radiometric evaluation techniques that are meant to enhance the investigator’s knowledge of the mineral deposit. Samples are obtained by chipping outcrops, trenching, tunneling and drilling; in addition, borehole logs may be provided to study the geologic and structural makeup of the deposit.

DEVELOPMENT In the third stage, development, the work of opening a mineral deposit for exploitation is performed. With it begins the actual mining of the deposit, now called the ore. Access to the deposit must be gained either 1. By stripping the overburden, which is the soil and/or rock covering the deposit, to expose the near-surface ore for mining or 2. By excavating openings from the surface to access more deeply buried deposits to prepare for underground mining. In either case, certain preliminary development work, such as acquiring water and mineral rights, buying surface lands, preparing permit applications and an environmental impact statement (EIS), will generally be required before any development takes place. When these steps have been achieved, the provision of a number of requirements such as access of roads, power sources, mineral transportation systems, mineral processing facilities, waste disposal areas, offices, and other facilities must precede actual mining in most cases.

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BY: IZHAR MITHAL JISKANI

STAGES IN THE LIFE OF A MINE

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Some nonmetallic mines have no overburden to remove; the mineral is simply excavated at the surface. Development for underground mining is generally more complex and expensive. It requires careful planning and layout of access openings for efficient mining, safety, and permanence. The principal openings may be shafts, slopes, or adits; each must be planned to allow age of workers, machines, ore, waste, air, water and utilities. Many metal mines are located along steeply dipping deposits and thus are opened from shafts, while drifts, winzes and raises serve the production areas. Many coal and nonmetallic mines are found in nearly horizontal deposits. Their primary openings may be drifts or entries, which may be distinctly different from those of metal mines.

EXPLOITATION Exploitation, the fourth stage of mining, is associated with the actual recovery of minerals from the earth in quantity. Although development may continue, the emphasis in the production stage is on production. Usually only enough development is done prior to exploitation to ensure that production, once started, can continue uninterrupted throughout the life of the mine. The mining method selected for exploitation is determined mainly by the characteristics of the mineral deposit and the limits imposed by safety, technology, environmental concerns, and economics. Geologic conditions, such as the dip, shape, and strength of the ore and the surrounding rock, play a key role in selecting the method. Traditional exploitation methods fall into two broad categories based on locale: surface or underground. Surface mining includes mechanical excavation methods such as open pit and open cast (strip mining) and aqueous methods such as placer and solution mining. Underground mining is usually classified in three categories of methods: uned, ed, and caving.

EXPLOSIVES The maximum breakage and displacement of rock depends upon drilling practices and correct selection or explosive and its use. Explosive are the mixture 3

BY: IZHAR MITHAL JISKANI

STAGES IN THE LIFE OF A MINE

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of solids or of solids and liquids. Upon the explosion the sudden and break ingredients of mixture are transferred in to other products which are mostly gaseous and which occupy much greater volume than the original mixture. Also this product liberates heat which expands the gases and causes tem to exert enormous pressure. These gases produce shattering effects on the surrounding material. Thus it can be said that the explosives are the powerful sources of energy in highly concentrated form. The explosions used for blasting are checked for the following characteristics: •

Chemical contents.

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Density

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Velocity or Detonation.

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Weight strength.

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Water resistance.

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Commercial use in rock, soil and ore.

CLASSIFICATION OF EXPLOSIVES Explosives are classified as High explosives & Low explosive.

HIGH EXPLOSIVES The distinguish characteristics of high explosives are the fact that it detonates when it is properly primed and an explosion is initiated in it. Detonation is the description of the process or propagation of shock wave through an explosive, which is accompanied by a chemical reaction that furnishes energy to maintain the shock waves propagation, is a stable manner. There are some blasting agents which are used as alternates to explosives, such as carbox, air dox, Hydrox. The high explosives agents are more preferable for blasting purposes rather than explosives or airdox, car box etc 4

BY: IZHAR MITHAL JISKANI

STAGES IN THE LIFE OF A MINE

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A wide range of explosives is suitable for blasting the quarry face and final choice is governed by the site and method of drilling employed. Thus for blasting a dolomite quarry by making holes drilled with wagon drill, crawl air LM-300, high explosives are suitable.

LOW EXPLOSIVES OR DEFLAGRATING Low explosives are black powders composed of every intimate mixtures of sulfur, charcoal and either potassium nitrate or sodium nitrate. They burn progressively over a relatively sustained period of time, in contrast to detonating explosives which decompose practically instantaneously. Black powders are the slowest acting of all the explosives and they give a shearing and heaving action tending to blast rock in to large, firm fragment. Their action derives from a relatively slow development of gas pressure so that they must be loaded carefully and closely confined. Burden or holes spacing should be well balanced since there is a tendency for the rock to yield at weak points. Black powder is manufactured in granular and pellet forms. The general powders are of different gradation and usually they are packed in 25lbs heavy containers. Palletized powders are available in cartridges of 8-inches length and diameter ranging from 0.5 to 2.5 inches packed in 50lb cases. Black powder ignites at about 572F. Ignition may be by flame, spark, hot wire or hot surface or by such blasting accessories as squibs, electric squibs, igniter and detonating cord. Presently black powder is little used in rock excavation, having given way to high explosives. It is moderately used in the quarrying of heavy solid stones for riprap and in the blasting of coal in pit mines.

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BY: IZHAR MITHAL JISKANI