Quarrying

The quarrying process can be divided into five operations - overburden removal, drilling, blasting, loading and hauling to the processing plant. 

Historically, these operations were very labour intensive. However, mechanisation, which started in the late 1940 s in Europe, and is currently being applied in most of the developing countries of the world, has dramatically reduced labour requirements. This section, therefore, concentrates on mechanised quarrying practices. 

The thickness of overburden can vary from less than Im to tens of metres. Indeed, if the thickness is considerable, the costs of overburden removal can make the development of an open-cast quarry uneconomic and may force the developer to consider mining (see section 4.3.7). The overburden generally consists of top-soil and sub-soil, but may also include rock overlying the limestone. 

Disposal of the overburden can be a significant operation. Top-soil should be handled and stored in such a way as to preserve its fertility and permit its later use in landscaping schemes [4.7,4.8]. Sub-soils and over-lying rock may be tipped, in which case the tips must be designed to be stable and have adequate drainage [4.9, 4.10]. In some situations, it may be possible to sell part of the overburden as in-fill. 

Overburden may be removed as an on-going operation, or in campaigns. In many countries, soil is best removed in summer, when it is drier, able to bear the weight of earth-moving equipment and is in a better condition for handling and storage. 

For all these applications, the general procedure is to drill a hole into the solid rock or coal, insert cartridge of explosive with a detonator followed by firing of explosive to fracture and bring down the rock or coal bed. 

Coal mining is usually done by a method which is known as the long wall system , the details of which are already available in the literature [100]. The most important thing to remember during coal mining is that methane gas may be liberated not 

Around 60% of the commercial explosives produced in India are used by the mining industry. Permitted and conventional explosives are extensively used for gassy and open pit mines. In the majority of coal mines, particularly those located in the Indian State of Bihar, there is a continuous evolution of methane gas which forms an explosive mixture with air. By suitably reducing the flame temperature (Tf) and duration of explosion, the ignition of explosive mixture (methane + air) is considerably reduced. 

Building stone (dimension stone) is usually cut from the quarry face by means of a wire saw. Explosives are used only for clearing overburden or to remove obstacles. The process of quarrying is analogous to obtaining coal from opencast sites where the coal is at or near the surface of the ground. Under wet conditions, 

Apart from coal mining, mining is carried out for gold, anhydrite and gypsum, iron ore, non-ferrous ores and rock salt etc. Copper ores are usually compact and mechanically strong and are broken-up by blasting before they can be removed. 

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There is only one method available that allows the study of the vertical and lateral relationship of the different rock types of a reservoir on a scale of 1 1. This is the study of outcrops. These are areas like quarries, readouts, cliffs, mines, etc., which consist of a sequence known to be a reservoir in the vicinity or the lateral equivalent thereof. Detailed investigation of a suitable outcrop can often be used as a predictive tool to model ... 

Ytterby, a village in Sweden near Vauxholm) Yttria, which is an earth containing yttrium, was discovered by Gadolin in 1794. Ytterby is the site of a quarry which yielded many unusual minerals containing rare earths and other elements. This small town, near Stockholm, bears the honor of giving names to erbium, terbium, and ytterbium as well as yttrium. 

Sandstone. Sandstone wheels were once quarried extensively for farm and industrial use, and special grades of stone for precision honing, sharpening, and lapping are a small but important portion of today s abrasive industry. Production of honing and sharpening stones from deposits of dense, fine grain sandstone in Arkansas account for 76% of the value (about 2 million in 1987) and 88% of the total quantity of such stones in the United States (4). 

Synthetic Processes. Traditional Solvay plants produce large volumes of aqueous, chloride-containing waste which must be discharged. This fact, in addition to a noncompetitive cost position, is largely responsible for the demise of U.S. synthetic plants. In countries other than the United States, waste is sent to the ocean, rivers, or deep underground wells. The AC and NA coproduct processes produce less aqueous waste than the traditional Solvay and NA mono processes. Related environmental concerns are added whenever a plant complex includes lime quarries and ammonia-producing equipment. 

Ammonium nitrate-based explosives account for about 97% of total U.S. industrial explosive consumption. Coal mining in the United States formed about 65—68% of the demand for explosives in 1991. The remaining uses were quarrying and nonmetal mining, 15% metal mining, 10% constmction, 7% miscellaneous uses, 3—4%. The properties of ammonium nitrate are given in Table 18 (173,239—242). 

Land, such as farmsteads, stripmines, quarries, and other lands, that do not fit into any other land class category. 

Impact-Isolating Constructions. Adequate impact sound isolation is difficult to achieve when hard materials, such as terrazzo, quarry tile. ... 

Limestone Production. Because more than 99% of U.S. limestone is sold or used as cmshed and broken stone, rather than dimension-stone, most of the description of limestone s extraction and processing herein focuses on the former (Fig. 4). Most stone is obtained by open-pit quarrying methods. Underground mining is pursued by some important operations, but the toimage quarried exceeds that mined by nearly 20-fold. There is, however, a slight trend toward increased mining which should continue. 

Most limestone quarries use either 100% ammonium nitrate [6484-52-2] (fertilizer grade) and fuel oil (ANFO), or a combination of ANFO and ammonium or gelatin dynamite, for blasting (see Explosives and propellants, explosives). After blasting, oversized boulders usually are reduced to manageable sizes by drop ball cranes. 

Quarries that excavate soft stone, notably mad or chalk, do not dtiU or blast, but extract the stone usiag heavy-duty rippers and scrapers. In the Middle West and Florida, lake mads and soft coralline limestone are dredged ia a process much like stripmining. 

Stone Number of quarries Quantity, t X 10" Value, X 10" Unit value, /t... 

Portland Cement Manufacture. The second greatest use of limestone is as raw material in the manufacture of Pordand cement (10). The average limestone factor per ton of Pordand cement is 1.0—1.1 t of pulverized limestone. The limestone, calcined to lime in the cement rotary kiln, combines with siUca and alumina to form tricalcium siUcate and tricalcium aluminate and other lesser cementing compounds (see Cement). Most cement companies operate captive limestone quarries. 

Time Manufacture. Limestone is consumed at the rate of 32-34 x 10 t/yr in the manufacture of lime. About 75% of the tonnage is captively produced in the United States. The balance is shipped from quarries in northern Michigan and British Columbia in large ore boats or barges. The Hmestone lime ratio is ca 2 1. 

P. Rivers-Moore, "Environmental Control of Time Plants and Quarries in S. Africa," 4th International Time Congress Proceedings, Hershey, Pa., 1978. 

Pit and Quarry Handbook, Pit Quarry pubhcations, Chicago, lU., 1982, compendium of quarry and lime plant equipment. 

Pit and Quarry Maga fine, Cleveland, Ohio, numerous articles on production of limestone and lime. 

Flow Sheets. AH minerals processing operations function on the basis of a flow sheet depicting the flow of soHds and Hquids in the entire plant (6,13,14). The complexity of a flow sheet depends on the nature of the ore treated and the specifications for the final product. The basic operations in a flow sheet are size reduction (qv) (comminution) and/or size separation (see Separation, size), minerals separation, soHd—Hquid separation, and materials handling. The overaH flow sheet depends on whether the specification for the final mineral product is size, chemical composition, ie, grade, or both. Products from a quarry, for example, may have a size specification only, whereas metal concentrates have a grade specification. 

Size reduction (qv) or comminution is the first and very important step in the processing of most minerals (2,6,10,20—24). It also involves large expenditures for heavy equipment, energy, operation, and maintenance. Size reduction is necessary because the value minerals are intimately associated with gangue and need to be Hberated, and/or because most minerals processing/separation methods require the ore mass to be of certain size and/or shape. Size reduction is also required in the case of quarry products to produce material of controlled particle size (see Size measurement of particles). In some instances, hberation of valuables or impurities from the ore matrix is achieved without any apparent size reduction. Scmbbers and attritors used in the industrial minerals plants, eg, phosphate, mtile, glass sands, or clay, ate examples. 

Industrial screening is used essentially for separations over 0.2 mm and in conjunction with cmshers because the efficiency decreases rapidly as particle size decreases. The main objective is to remove undersize material that should not be circulated back to the cmshers, or to remove (scalp) oversize material or trash that should not report to the subsequent processing step. Other appHcations of screening include production of a specification size material (as in quarrys), dewatering, and trash removal from processed material. 

Pulpstones. Improvements have been made in the composition and speed of the grinding wheel, in methods of feeding the wood and pressing it against the stone, in control of power to the stones, and in the size and capacity of the units. The first pulpstones were manufactured from quarried sandstone, but have been replaced by carbide and alumina embedded in a softer ceramic matrix, in which the harder grit particles project from the surface of the wheel (see Abrasives). The abrasive segments ate made up of three basic manufactured abrasive siUcon carbide, aluminum oxide, or a modified aluminum oxide. Synthetic stones have the mechanical strength to operate at peripheral surface speeds of about 1200—1400 m /min (3900 to 4600 ft/min) under conditions that consume 0.37—3.7 MJ/s (500—5000 hp) pet stone. 

Quarried, cmshed, sized from 0.95 cm to dust and fluxed with softer asphalt for use as cold-appHed pavement surfacing. 

Portland cement is classified as a hydrauHc cement, ie, it sets or cures in the presence of water. The term Portland comes from its inventor, Joseph Aspdin, who in 1824 obtained a patent for the combination of materials referred to today as Portland cement. He named it after a grayish colored, natural limestone quarried on the Isle of Portland, which his cured mixture resembled. Other types of hydrauHc cements based on calcium materials were known for many centuries before this, going back to Roman times. Portland cement is not an exact composition but rather a range of compositions, which obtain the desired final properties. The compounds that make up Portland cements are calcium siHcates, calcium aluminates, and calcium aluminoferrites (see ). 

Calcium carbonate [471-34-17, CaCO, mol wt 100.09, occurs naturally as the principal constituent of limestone, marble, and chalk. Powdered calcium carbonate is produced by two methods on the industrial scale. It is quarried and ground from naturally occurring deposits and in some cases beneficiated. 

The natural ore is quarried or mined ia many areas of North America and Europe. Treading North American regions iaclude Canada, Mexico, and ia the United States, California, Texas, Nevada, Iowa, Kansas, Ohio, Indiana, and Michigan. In Europe, Erance, Spain, Italy, the United Kingdom, and Russia have significant deposits of natural gypsum, as does Germany. 

The demand for cement was stimulated by the growth of canal systems ia United States duting the nineteenth century. Process improvements were made ia the calciaation of certain limestones for the manufacture of natural cements, which were gradually displaced by Pordand cement. This latter was named ia a 1824 patent because of its color and resemblance to a natural limestone quarried on the Isle of Pordand ia England. Research conducted siace that time has provided a clear picture of the composition, properties, and fields of stabiUty of the principal systems found ia Pordand cement. These results led to the widely used Bogue calculation of composition based on oxide analysis (1). Details beyond the scope of this article may be found ia the Hterature (2). 

Because calcium oxide comprises about 65% of Pordand cement, these plants are frequendy situated near the source of their calcareous material. The requisite silica and alumina may be derived from a clay, shale, or overburden from a limestone quarry. Such materials usually contain some of the required iron oxide, but many plants need to supplement the iron with mill scale, pyrite cinders, or iron ore. Silica may be supplemented by adding sand to the raw mix, whereas alumina can be furnished by bauxites and Al202-rich flint clays. 

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