Strip mining

To reach the coal, bulldozers 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 into the overlying sedimentary rock, fill these holes with explosives, 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 for transport. 

Strip mining is a method of coal recovery in which the coal seam is exposed by removing the overburden (the earth above the coal seam) in long cuts or strips. The soil from the first strip is deposited in an area outside the planned mining area. Spoil from subsequent cuts is deposited as fill in the previous cut after coal has been removed. 

FIGURE 5.12 A dragline engaged in overburden removal. Weight 7,000,000 lb, boom length 425 ft, boom vertical height 210 ft, and bucket capacity 60 yd.  

The overburden is then removed to a previously mined (and now empty) strip. When all the overburden is removed, the underlying coal seam will be exposed (a block of coal). This block of coal may be drilled and blasted (if hard) or otherwise loaded onto trucks or conveyors for transport to the coal preparation (or wash) plant. Once this strip is empty of coal, the process is repeated with a new strip being created next to it. This method is most suitable for areas with flat terrain. 

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Includes crop and pasture land and farmsteads, strip mines, permanent snow and ice, and land that does not fit iato any other land cover. 

Elemental phosphoms is produced from a phosphoms-rich ore mostiy recovered by strip mining. This ore usually contains fluorapatite, plus some sihca and siUcates. When a carbon source, usually coke, is added to the ore at temperatures greater than 1100°C, the following overall reaction occurs ... 

The western phosphates are sedimentary deposits in adjoining areas of Wyoming, Idaho, and Utah derived from a former inland sea. They consist of layers of limestone, phosphate, and chert, now budded and faulted so they are rarely horizontal. The phosphate ore is strip-mined using large earth-moving equipment such as shovels, scrappers, dump tmcks, and bulldozers to mine the overburden and phosphate ore. Mining ratios of overburden to metric ton of recovered ore are from 1—3 m /1 (2—4 yd /short ton). The typical mining practice is to remove ore and overburden from a pit in discrete layers (Lifts) of 10—20 m in depth. Overburden from the pit is back-hauled to a previously mined pit. Extensive land reclamation practices are later carried out to return the mine areas to natural states. 

Tar Sands Canadian tar sands are strip-mined and extracted with hot water to recover heavy oil (bitumen). The oil is processed into naphtha, kerosene, and gasoline fractions (which are hydrotreated), in addition to gas (which is recovered). Tar sands are being developed in Utah also. 

A dragline at Atlantic Richfield s Black Thunder strip mine in Gillette, Wyoming, loads coal into a dump truck. The coal is transported to cities around the country where it is burned to generate electricity. (Corbis-Bettmannj... 

Recovering the bitumen is not easy, and the deposits are either strip-mined if they are near the surface, or recovered in situ if they are in deeper beds. The bitumen could be extracted by using hot water and steam and adding some alkali to disperse it. The produced bitumen is a very thick material having a density of approximately 1.05 g/cm. It is then subjected to a cracking process to produce distillate fuels and coke. The distillates are hydrotreated to saturate olefinic components. Table 1-8 is a typical analysis of Athabasca bitumen. ... 

Uranium is the fuel of nuclear reactors. The most important of its minerals is pitchblende, U02 (Fig. 17.28), much of which is obtained from strip mines in New Mexico and Wyoming. Uranium is refined to reduce the ore to the metal and to enrich it that is, to increase the abundance of a specific isotope—in this case, uranium-235. The natural abundance of uranium-235 is about 0.7% for use in a nuclear reactor, this fraction must be increased to about 3%. 

A major consequence of the activities associated with the exploitation of mineral deposits (i.e., exploration, the development of mines and processing facilities, the extraction and concentration, which is also called beneficiation, of ores containing the desired minerals, and the decommissioning or abandonment of mine facilities) is the production of extremely large volumes of unwanted materials. Waste volumes vary from ca. 30% of the mass of the ore in the case of gypsum and other non-metals, to about 50% for base metals to more than 80% for strip-mined... 

Opencast mining or strip mining. Obtaining coal or ore which is near the surface by removing the overlying soil and rock to expose the coal or ore for direct recovery. 

Furthermore, the extraction of non-conventional oil has other detrimental environmental impacts, such as water pollution and loss of biodiversity. Depending on the depth of the deposits, oil sands are either strip mined in open pits or heated so that the bitumen from which the non-conventional oil is extracted can flow to the surface (in-situ extraction). Both forms of oil-sands extraction require considerable amounts of energy (i.e., natural gas) and water, and lead to significant detrimental environmental impacts (Woynillowicz et al., 2005 see also Chapter 3). 

In the USA, LOX have been used primarily in the strip mining of coal. For example, in 1950, 99.5% of all the LOX used was in coal mining (Ref 18). Most of this must have been for moving overburden, since LOX are non-permissible (not allowed by law in gassy mines),... 

Uses. In section 1, we showed that most of the LOX in the USA are used in the strip mining of coal. In Europe LOX were also extensively used in open pit mining, tunneling and construction. Indeed, in the first half of this century, LOX were used in most expls applications, although not extensively, where fumes were not a problem. O Neil Van Fleet (Ref 5a) consider LOX economical and safe (See Sect 4 on LOX safety). La Magna (Ref 9) prefers LOX to Dynamites. In the last decade... 

In Chap 20 of Ref 63. pp299-312, is described the development of "Strip Mining of Coal with recommended expls "ANFO-P , "Nilite and "Hi-Cap (p305) for bituminous coal, while for anthracite coal "Nitramon , "Nitramite or "Tovex is used. If a Dynamite is preferred, "Hi-Cap is usually most economical, although a stronger expl such as 50% "Red Cross Extra may be needed (p310)... 

AND s have been used for blasting soft rocks, clays and for earth excavations. They are not suitable, however, for use in coal mining except "strip-mining", called "opencast mining by the British... 

Routine quantitative petrographic procedures were employed throughout the current study with only minor necessary modifications. Channel samples were collected in the field from each megascopically recognizable coal layer in the bed exposed in strip mines, road cuts, and underground mines. In the laboratory, the samples were crushed to —30 mesh (—590 microns), pelletized... 

Figure 2. Sample locations—Upper Freeport coal 1—Harmar Mine, 2— Springdale Mine, 3—Armstrong Mine, 4—Coral strip mine, 5—Houtzdale...

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