Mine development and lifecycle

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STAGES IN THE LIFE OF MINING

The overall sequence of activities in modern mining is often compared with the five stages in the life of mining: 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- geologists more involved with the former, mining engineers more with the latter. 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, to reflect the times. Closure and reclamation of mining site has become a necessary part of mining 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.

1. What stage of mining is combined with exploration?

2. What stages of mining are mostly involved by mining engineers?

3. Why has closure of mining site become a necessary part of mining life cycle?

Prospecting

Prospecting is the search for ores or other valuable minerals (coal or nonmetallic). 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 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 gathers 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. The most valuable scientific tool employed in the indirect search for hidden mineral deposits is geophysics, the science of detecting anomalies using physical measurements of gravitational, seismic, magnetic, electrical, electromagnetic, and radiometric variables of the earth. The methods are applied from the air, using aircraft and satellites; on the surface of the earth; and beneath the earth, using methods that probe below the topography. Geochemistry, the quantitative analysis of soil, rock, and water samples, the analysis of plant growth patterns, can also be employed as prospecting tools.

1. What is the aim of prospecting?

2. What method of prospecting is simple and why?

3. What science detects anomalies of the Earth’ crust?

Exploration

Exploration determines as accurately as possible the size and value of a mineral deposit. 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. Rotary, percussion, or diamond drills can be used for exploration purposes. The core is normally split along its axis; one half is analyzed, and the other half is retained intact for further geologic study. An evaluation of the samples enables the geologist or mining engineer to calculate the tonnage and grade, or richness, of the mineral deposit. He estimates the mining costs, evaluates the recovery of the valuable minerals, determines the environmental costs, and assesses other factors in an effort to reach a conclusion about the profitability of the mineral deposit. The crux of the analysis is the question of whether the property is just another mineral deposit or an ore body. For an ore deposit, the overall process is called reserve estimation, that is, the examination and valuation of the ore body. At the conclusion of this stage, the project is developed, traded to another party, or abandoned.

1. What is the aim of exploration?

2. What kinds of evaluative techniques are used?

3. What does the evaluation of the samples enable for the mining engineering?

Development

Development is performed the work of opening a mineral deposit for exploitation. With it begins the actual mining of the deposit, now called the ore. Access to the deposit must be gained either by stripping the overburden, which is the soil and/or rock covering the deposit, to expose the near-surface ore for mining or 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, and 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— access roads, power sources, mineral transportation systems, mineral processing facilities, waste disposal areas— must precede actual mining in most cases. Stripping of the overburden will then proceed if the minerals are to be mined 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. Many metal mines are located along steeply dipping deposits and thus are opened from shafts. Many coal and nonmetallic mines are found in nearly horizontal deposits.

1. What kind of development is more complex and expensive?

2. What requirements will before any development takes place be necessary?

3. What is the name of stage performing the actual mining of the deposit?

Exploitation

Exploitation, the fourth stage of mining, is associated with the actual recovery of minerals from the earth in quantity. 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 methods such as placer and solution mining. Underground mining is usually classified in three categories of methods: unsupported, supported, and caving. Surface mining is the predominant exploitation procedure worldwide. In open pit mining, a mechanical extraction method, a thick deposit is generally mined in benches or steps, although thin deposits may require only a single bench or face. Open pit or open cast mining is usually employed to exploit a near-surface deposit or one that has a low stripping ratio. It often necessitates a large capital investment but generally results in high productivity, low operating cost, and good safety conditions.

1. What are the names of underground mining’s methods?

2. Call the key roles in selecting method.

3. What is the meaning of exploitation?

Coal formation

All living plants store solar energy through a process known as photosynthesis. When plants die, this energy is usually released as the plants decay. Under conditions favorable to coal formation, the decaying process is interrupted, preventing the release of the stored solar energy. The energy is locked into the coal. Coal formation began during the Carboniferous Period - known as the first coal age - which spanned 360 million to 290 million years ago. The build-up of silt and other sediments, together with movements in the earth's crust - known as tectonic movements - buried swamps and peat bogs, often to great depths. With burial, the plant material was subjected to high temperatures and pressures. This caused physical and chemical changes in the vegetation, transforming it into peat and then into coal.

The degree of change undergone by a coal as it matures from peat to anthracite is known as coalification. Coalification has an important bearing on coal's physical and chemical properties and is referred to as the 'rank' of the coal. Ranking is determined by the degree of transformation of the original plant material to carbon. The ranks of coals, from those with the least carbon to those with the most carbon, are lignite, sub-bituminous, bituminous and anthracite.

The quality of each coal deposit is determined by:

Types of vegetation from which the coal originated

Depths of burial

Temperatures and pressures at those depths

Length of time the coal has been forming in the deposit

1. When did coal formation begin?

2. What do tectonic movements mean?

3. What types of coal do you know?

Types of coal

Initially the peat is converted into lignite or 'brown coal' - these are coal-types with low organic maturity. In comparison to other coals, lignite is quite soft and its colour can range from dark black to various shades of brown.

Over many more millions of years, the continuing effects of temperature and pressure produces further change in the lignite, progressively increasing its organic maturity and transforming it into the range known as 'sub-bituminous' coals. Further chemical and physical changes occur until these coals became harder and blacker, forming the 'bituminous' or 'hard coals'.

Under the right conditions, the progressive increase in the organic maturity can continue, finally forming anthracite.

In addition to carbon, coals contain hydrogen, oxygen, nitrogen and varying amounts of sulphur. High-rank coals are high in carbon and therefore heat value, but low in hydrogen and oxygen. Low-rank coals are low in carbon but high in hydrogen and oxygen content. Different types of coal also have different uses.

1. What coal-types are with low organic maturity?

2. What does coal contain?

3. What type of coal is the hardest and darkest?

Mine development and lifecycle

The process of mining from discovery of an ore body through extraction of minerals and finally to returning the land to its natural state consists of several distinct steps. The first is discovery of the ore body, which is carried out through prospecting or exploration to find and then define the extent, location and value of the ore body.

The next step is to conduct a feasibility study to evaluate the financial viability, the technical and financial risks, and the robustness of the project. This is when the mining company makes the decision whether to develop the mine or to walk away from the project.

To gain access to the mineral deposit within an area it is often necessary to mine through or remove waste material which is not of immediate interest to the miner. The total movement of ore and waste constitutes the mining process. Waste removal and placement is a major cost to the mining operator, so a detailed characterization of the waste material forms an essential part of the geological exploration program for a mining operation.

Once the analysis determines a given ore body is worth recovering, development begins to create access to the ore body. The mine buildings and processing plants are built, and any necessary equipment is obtained. The operation of the mine to recover the ore begins and continues as long as the company operating the mine finds it economical to do so. Once all the ore that the mine can produce profitably is recovered, reclamation begins to make the land used by the mine suitable for future use.

1. How is discovery of the ore body carried out?

2. What does feasibility study mean?

3. How long does the operation of the mine to recover the ore continue?

Underground mining

Sub-surface mining consists of digging tunnels or shafts into the earth to reach buried ore deposits. Ore, for processing, and waste rock, for disposal, are brought to the surface through the tunnels and shafts. Sub-surface mining can be classified by the type of access shafts used, the extraction method or the technique used to reach the mineral deposit. Drift mining utilizes horizontal access tunnels, slope mining uses diagonally sloping access shafts, and shaft mining utilizes vertical access shafts. Mining in hard and soft rock formations require different techniques.

Other methods include shrinkage stope mining, which is mining upward, creating a sloping underground room, long wall mining, which is grinding a long ore surface underground, and room and pillar mining, which is removing ore from rooms while leaving pillars in place to support the roof of the room. Room and pillar mining often leads to retreat mining, in which supporting pillars are removed as miners retreat, allowing the room to cave in, thereby loosening more ore. Additional sub-surface mining methods include hard rock mining, which is mining of hard rock (igneous, metamorphic or sedimentary) materials, bore hole mining, drift and fill mining, long hole slope mining, sub level caving, and block caving.

1. What does sub-surface mining consists of?

2. How can we classify sub-surface mining?

3. What is shrinkage stope mining?

Safety

Mining ventilation is a significant safety concern for many miners. Poor ventilation inside sub-surface mines causes exposure to harmful gases, heat, and dust, which can cause illness, injury, and death. The concentration of methane and other airborne contaminants underground can generally be controlled by dilution (ventilation), capture before entering the host air stream (methane drainage), or isolation (seals and stoppings). A ventilation system is set up to force a stream of air through the working areas of the mine. The air circulation necessary for effective ventilation of a mine is generated by one or larger mine fans, usually located above ground.

Ignited methane gas is a common source of explosions in coal mines, which in turn can initiate more extensive coal dust explosions. For this reason, rock dusts such as limestone dust are spread throughout coal mines to diminish the chances of coal dust explosions as well as to limit the extent of potential explosions, in a process known as rock dusting.

1. What does poor ventilation inside sub-surface mines cause?
2. Why is a ventilation system set up?
3. What is a common source of explosions in coal mines?

K. I. Satpayev

Kanysh Imantayevich Satpayev was born in April 12, 1899 in Pavlodar. In 1926 K.I.Satpayev successfully graduated from Tomsk technological institute and was sent to the Central Council of national economy.

K.I. Satpayev headed Geological Department of the trust «Atbastsvetmet». Serious problem fell on its share – carrying out of the first stationary prospecting works on a systematic identification of mineral reserves in Zhezkazgan-Ulytau area.

In autumn of 1943, for merits in development of science and great scientific achievements K.I.Satpayev was elected a corresponding member of the USSR Academy of Sciences. Those years he devoted special attention to design and construction of Kazakhstan Magnitka, Balkhash and Atasu mining complex.

In June 1946 K.I. Satpayev was elected as the first President of the Academy of Sciences of Kazakhstan. He personally led a comprehensive study of natural resources of the Mangyshlak Peninsula, the research of new deposits of coal, oil, gas, ores of ferrous metallurgy, actively supported construction of the channel Irtysh-Karaganda.

In 1958 for development of methodological basis and drawing up of forecast metallogenic maps of Central Kazakhstan, which had no analogue in worldwide geological practice, group of Kazakhstan’s scientists-geologists headed by K.I.Satpayev was awarded with Lenin prize. This work showed role of Kazakhstan’s scientists and school of K.I.Satpayev all over the world.

1. What problem did K.I. Satpayev solve, when he headed Geological Department of the trust «Atbastsvetmet»?
2. Why was K.I.Satpayev elected a corresponding member of the USSR Academy of Sciences?
3. What work showed role of Kazakhstan’s scientists and school of K.I.Satpayev all over the world?

Date: 2016-01-03; view: 1355