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تاريخ التسجيل : 07/04/2010
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مُساهمةموضوع: mining engineering   الإثنين أبريل 19, 2010 5:51 pm

Surface coal mine with haul truck in foregroundMining engineering is an engineering discipline that involves the practice, the theory, the science, the technology, and application of extracting and processing minerals from a naturally occurring environment. Mining engineering also includes processing minerals for additional value.

The need for mineral extraction and production is an essential activity of modern society. Mining activities by their nature cause a disturbance of the environment in and around which the minerals are located. Modern mining engineers must therefore be concerned not only with the production and processing of mineral commodities, but also with the mitigation of damage or to the environment as a result of that production and processing.

Contents
1 History of Mining Engineering
2 US Salary and Statistics
3 Mineral Exploration
3.1 Mineral Discovery
3.2 Mineral Determination
3.3 Feasibility Study
4 Mining Operation
4.1 Surface Mining
4.2 Mining Process
4.2.1 Blasting

History of Mining Engineering
Since the beginning of civilization people have used stone, ceramics and, later, metals found on or close to the Earth's surface. These were used to manufacture early tools and weapons. For example, high quality flint found in northern France and southern England were used to set fire and break rock.[1] Flint mines have been found in chalk areas where seams of the stone were followed underground by shafts and galleries. The oldest known mine on archaeological record is the "Lion Cave" in Swaziland. At this site, which by radiocarbon dating proves the mine to be about 43,000 years old, paleolithic humans mined mineral hematite, which contained iron and was ground to produce the red pigment ochre.[2][3]

The ancient Romans were innovators of mining engineering. They developed large scale mining methods, especially the use of large volumes of water brought to the minehead by numerous aqueducts for hydraulic mining. The exposed rock was then attacked by fire-setting where fires were used to heat the rock, which would be quenched with a stream of water. The thermal shock cracked the rock, enabling it to be removed. In some mines the Romans utilized water-powered machinery such as reverse overshot water-wheels. These were used extensively in the copper mines at Rio Tinto in Spain, where one sequence comprised 16 such wheels arranged in pairs, and lifting water about 80 feet (24 m).[4]

Black powder was first used in mining in Banská Štiavnica, Kingdom of Hungary present-day Slovakia in 1627.[5] This allowed blasting of rock and earth to loosen and reveal ore veins, which was much faster than fire setting. The Industrial Revolution saw further advances in mining technologies, including improved explosives and steam-powered pumps, lifts and drills.

US Salary and Statistics
There are an estimated 6,900 employed mining engineers. The median salary for a mining engineer is $75,960.[6] The mining engineer is typically employed in oil and gas extraction, metal ore mining, and coal mining. The occupation is expected to grow about faster than average. The faster growth is due to older mining engineers retiring and few schools that offer an education specific to this discipline.[7]

Mineral Exploration
Main article: Mineral exploration
Mining engineers are consulted for virtually every stage of a mining operation. The first role of engineering in mines is the discovery of a mineral deposit and the determination of the profitability of a mine.

Mineral Discovery
Mining engineers are involved in the mineral discovery stage by working with geologists to identify a mineral reserve. The first step in discovering an ore body is to determine what minerals to test for. The geologists and engineers drill core samples and conduct surface surveys searching for specific compounds and ores. For example a mining engineer and geologist may target metallic ores such as galena for lead or chalcolite for copper. A mining engineer may also search for a non-metal such as phosphate, quartz, or coal.

The discovery can be made from research of mineral maps, academic geological reports or local, state, and national geological reports. Other sources of information include property assays, well drilling logs, and local word of mouth. Mineral research may also include satellite and airborne photographs. Unless the mineral exploration is done on public property, the owners of the property may play a significant role in the exploration process, and may be the original discoverer of the mineral deposit.[8]

Mineral Determination
After a prospective mineral is located, the mining engineer then determines the ore properties. This may involve chemical analysis of the ore to determine the composition of the sample. Once the mineral properties are identified, the next step is determining the quantity of the ore. This involves determining the extent of the deposit as well as the purity of the ore.[9] The engineer drills additional core samples to find the limits of the deposit or seam and calculates the quantity of valuable material present in the deposit.

Feasibility Study
Main article: Mining feasibility study
Once the mineral identification and reserve amount is reasonably determined, the next step is to determine the feasibility of recovering the mineral deposit. A preliminary study shortly after the discovery of the deposit examines the market conditions such as the supply and demand of the mineral, the amount of ore needed to be moved to recover a certain quantity of that mineral as well as analysis of the cost associated with the operation. This pre-feasibility study determines whether the mining project is likely to be profitible; if it is then a more in-depth analysis of the deposit is undertaken. After the full extent of the ore body is known and has been examined by engineers, the feasibility study examines the cost of initial capital investment, methods of extraction, the cost of operation, an estimated length of time to payback, the gross revenue and net profit margin, any possible resale price of the land, the total life of the reserve, the total value of the reserve, investment in future projects, and the property owner or owners' contract. In addition, environmental impact, reclamation, possible legal ramifications and all government permitting are considered.[10],[11] These steps of analysis determine whether the mine company should proceed with the extraction of the minerals or whether the project should be abandoned. The mining company may decide to sell the rights to the reserve to a third party rather than develop it themselves, or the decision to proceed with extraction may be postponed indefinitely until market conditions become favorable.

Mining Operation
Mining engineers working in an established mine may work as an engineer for operations improvement, further mineral exploration, and operation capitalization by determining where in the mine to add equipment and personnel. The engineer may also work in supervision and management, or as an equipment and mineral salesperson. In addition to engineering and operations, the mining engineer may work as an environmental, health and safety manager or design engineer.

The act of mining required different methods of extraction depending on the mineralogy, geology, and location of the resources. Characteristics such as mineral hardness, the mineral stratification, and access to that mineral will determine the method of extraction.

Generally, mining is either done from the surface or underground. Mining can also occur with both surface and underground operations taking place on the same reserve. Mining activity varies as to what method is employed to remove the mineral.

Surface Mining
Surface comprises 90% of the world's mineral tonnage output. Also called open pit mining, surface mining is removing minerals in formations that are at or near the surface. Ore retrieval is done by material removal from the land in its natural state. Surface mining often alters the land characteristics, shape, topography, and geological make-up.

Surface mining involves quarrying which is excavating minerals by means of machinery such as cutting, cleaving, and breaking. Explosives are usually used to facilitate breakage. Hard minerals such as limestone, sand, gravel, and slate are generally quarried into a series of benches.

Strip mining is done on softer minerals such as clays and phosphate are removed through use of mechanical shovels, track dozers, and front end loaders. Softer Coal seams can also be extracted this way.

With placer mining, minerals can also be removed from the bottoms of lakes, rivers, streams, and even the ocean by dredge mining. In addition, in-situ mining can be done from the surface using dissolving agents on the ore body and retrieving the ore via pumping. The pumped material is then set to leach for further processing. Hydraulic mining or "hydralicking is utilized" in forms of water jets to wash away either overburden or the ore itself.[12]

Mining Process
Blasting

Explosives are used to break up a rock formation and aid in the collection of ore in a process called blasting. There are two types of explosives that can be used in mining: high velocity and low velocity. High velocity blasting uses high explosives while low velocity blasting is done with low explosives. Engineers determine the placement of the explosive charges and the blast sequence to efficiently and safely loosen the maximum amount of ore. They also are responsible for the safety of the miners by determining how best to support the rock ceiling in the newly-formed cave.
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