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By H. V. Alminas

The U.S. Virgin Islands consist of three major islands (St. Thomas, St. John, and St. Croix) and some 50 smaller islands that are located primarily along the coasts of St. Thomas and St. John. St. Croix, the largest of the islands, is located approximately 160 km south-southeast of San Juan, Puerto Rico and is about 218 km in area (Fig. 1). St. Thomas, the second largest island is located 64 km east of Puerto Rico and incorporates approximately 77 km2. St. John is located immediately to the east of St. Thomas and incorporates approximately 49 km2. The climate in the U.S. Virgin Islands is maritime tropical. The average annual rainfall at higher elevations is 127-152 cm and at lower elevations 51-76 cm. There is no well-defined wet or dry season. Temperatures generally average in the 80's (F°) with only a 5°-7° F variation throughout the year.

Jan 1, 1987

By Paul R. Thomas

This paper addresses two issues affecting the international ferrochromium market as they pertain to the changing pattern of U. S. chromium import dependency. These issues are 1) the long-term ferrochromium production cost differential between the United States and the Republic of South Africa and 2) the ability of Zimbabwe to expand ferrochromium production and exportation. This paper draws upon the data and analyses of a recent Bureau of Mines Minerals availability Program appraisal that evaluated the international availability of chromium in the form of chromite and ferrochromium from 10 market economy countries. South African ferrochromium producers are shown to have a long-term production cost advantage over U.S. producers of $0.03 to $0.04 per pound of contained chromium, in 1981 dollars. Zimbabwean ferrochromium production and exportation are expected to increase in the future. Major expansions of production capacity will be dependent upon alleviating potentially serious constraints in electric power, rail, and port facilities. In the long term, ferrochromium production costs in Zimbabwe are expected to increase faster than the rate of inflation, because as chromite mining from the podiform resources in Zimbabwe decreases, production from the Great Dyke resources will increase.

Jan 1, 1984

By Robert M. Stevens

INTRODUCTION Truck haulage of muck in underground mining operations has been in use around the world for many years. From the late 1.950s into the early 1970s, haulage by means of load-haul-dump (LHD) units challenged haulage by means of trucks, and, to a large degree, LHD units dominated the trackless concept of moving mate¬rial underground. However, beginning in 1975, the emphasis began to shift back to the use of trucks, with LHD units assuming the secondary role of loading the trucks. Over the years, several manufacturers have been offering trucks with capacities ranging from 4.5 to 45.4 t (5 to 50 st) and with features that specifically address the constraints of underground operation. TRUCK TYPES Three different types of trucks are available for use underground, namely the tip dumpers, telescoping dumpers, and push-plate dumpers. The following para¬graphs describe each of these three types. Tip Dumpers Tip dumpers are designed to lift the truck box, using gravity to dump the load out the rear of the box. The primary application of these trucks is in the haulage of muck to the surface. However, these trucks also may be utilized underground, if a chamber is provided to accommodate the raised truck box at the dumping point. Fig. 1 illustrates a four-wheel drive truck with a 10.0-t (11-st) capacity; this truck is only 1.9 m (6.25 ft) wide and is designed specifically to follow narrow and winding vein courses. Fig. 2 illustrates a two-wheel drive tip dumper with a 24.5-t (27-st) capacity; this truck operates on 12% grades with firm dry surfaces and in modes both loaded-up and loaded¬down. Telescoping Dumpers Telescoping dumpers specifically address the constraints imposed by low back heights, and they represent an optimization of compressed envelope size with maximum payload capacity. Figs. 3 and 4 illus¬trate a typical telescoping dumper with a capacity of 18.1 t (20 st). Fig. 3 shows the box in position for carrying the load, and Fig. 4 shows the same truck with the box in the full-dumping position. Fig. 5 illustrates the loading and dumping cycles. Fig. 6 illustrates an approximation of how an LHD unit with an eject-o-dump (EOD) bucket would be used to load over the rear of this type of truck. Fig. 6 shows a low-profile telescoping truck in the first stage of loading, with a 6.8-t (7.5-st) LHD unit equipped with an EOD bucket. A loader with a smaller capacity and a narrower bucket would allow the bucket to fit inside the truck box and would achieve an even lower loading height than that illustrated. Gen erally, an LHD unit equipped with an EOD bucket and teamed with a telescoping dump truck can be used with a lower back height than could any other front-end loader and truck team. Push-Plate Dumpers Push-plate dumpers are similar to telescoping Bump¬ers, except that they do not have the two-stage box. Instead, push-plate dumpers utilize a single push plate to discharge the load out the rear of the box. Gen erally, these units are limited to payload capacities of about 9 t (10 st). Fig. 7 illustrates a typical push-plate dumper.

Jan 1, 1982

BP Minerals America (BPMA) has completed its $400 million modernization of Kennecott Utah Copper's Bingham Canyon mine. Modernized facilities include the in-pit crusher, conveyor, ore storage area, concentrator, ore pipe-line, and tailings pipeline. With modernization, Kennecott will achieve substantial cost reductions. Bingham Canyon is now one of the lowest cost copper producers in the world. And the mine will continue to provide jobs and income in Utah for another 30 years or more. The Modernization Project began in February 1986. The work took 33 months. In late 1987, the construction force peaked at 1100 workers. Kennecott Utah Copper now employs a permanent work force of 2100 employees. Less equipment and more efficiency The modernization work has increased the scale of the facilities that transport and process copper ore. A large, continuous transport system has replaced multiple haulage units. Fewer but larger pieces of equipment have replaced many crushing, grinding, and flotation units. The result is less maintenance, fewer employees, and improved metal recoveries. About one-third of the $400 million modernization project is directed at improving ore movement by eliminating rail transport. The new concentrator accounts for the remaining two-thirds of the modernization investment. The modernized plant was started up in stages. In February, ore was fed to the crusher. By the end of March, the three grinding lines were operating and the flotation circuit was producing copper concentrate. In July, the design through-put rate of 70 kt/d (77,000 stpd) was reached. October saw the achievement of targeted metal recoveries that corresponded to the fully modernized operation. It is estimated that Bingham Canyon will annually produce 181 kt (200,000 st) of refined copper, 9.3 t (300,000 oz) of gold, 71 t (2.3 million oz) of silver, and 5.4 kt (12 million lb) of molybdenite. Current Bingham Canyon production is about 97 kt/d (107,000 stpd) and a similar amount of overburden. Some 70 kt/d (77,000 stpd) of ore are processed through the in-pit crusher and 27 kt/d (30,000 stpd) of ore are transported by rail. The Bingham Canyon mine has yielded more than 11 Mt (12 million st) of refined copper. In 1863, precious metals - silver-bearing lead - were first discovered in Bingham Canyon. What was once a mountain is now a huge open pit. In fact, the mine is the world's largest man made excavation. The pit is some 4 km (2.5 miles) wide and 0.8 km (0.5 miles) deep. Since the pit began operating in 1906, more than 4.5 Gt (5 billion st) of material have been removed. Modernized facilities Electric 21 m3 (27 cu yd) or 23 m3 (30 cu yd) shovels are used to load the haulage trucks. Both 154 t (170 st) and 181 t (200 st) trucks are used to haul the ore to a mobile, in-pit crusher. The crusher replaces three crushers located at the old concentrators. There are two dumping locations at the new crusher, which can handle two trucks a minute. The 1.5 x 2.7 m (60 x 109 in.), 745 kW (1000 hp) Allis-Chalmers gyratory crusher reduces the ore to 254 mm (10 in.) size or less and delivers it to the conveyor. The crusher and conveyor systems are capable of handling 9 kt/h (10,000 stph) of ore.

Jan 11, 1988

By Charles T. Staniek

Following a dragline relocation at Agrico's Fort Green phosphate mine in 1986, the recovery plant experienced a significant decrease in flotation performance. Through weeks of trial and error testing, we discovered we could restore recoveries by conditioning feed at pH's higher than we had used historically. The higher pH's essentially increased flotation cell kinetics, although we still do not understand the exact mechanism at work. Armed with new-found appreciation of pH modification, we initiated a program to determine the optimum modifier for us, from both a performance and environmental perspective. Environmental considerations were important because ammonia, the standard industry modifier, is a plant nutrient and higher usage rates could affect the quality, of our recycle process water. This paper describes the research and development work spanning a 3 year period that culminated in making a major change in our reagent suite when we replaced ammonia with soda ash on a permanent full-time basis.

Jan 1, 1993

By A. T. Visser

The expansion of surface mining has led to the development of very large off-highway trucks currently capable of hauling payloads in excess of 290t. Mine haul roads have historically been designed empirically, relying heavily on local experience; the trend in increasing truck size will thus render the current pavement systems inadequate. Since truck haulage costs can account for 10%-50% of the total costs incurred by a surface mine, not only would the maintenance costs of existing roads of inadequate design increase, vehicle operating and maintenance costs would also increase prohibitively. There is thus a need for improved design technologies encompassing the construction and management techniques of mine haul roads, appropriate for the wheel loads of vehicles now in use. The aim of the paper is to present the different components of a mine haul road design and management system and to demonstrate the value of its application through case studies. The system has been applied at several South-African surface mines and distinct benefits have been derived. The improved structural design of a new road resulted in a 29% saving in construction costs and also provided better service, whilst the optimal selection and management of wearing-course materials provided better functionality at lower total transportation operating costs.

Jan 1, 1999

By A. S. Ibrado

The adsorption of silver on activated carbon from cyanide solutions was studied as a function of concentration, ionic strength and pH. In cyanide solutions, silver exists mainly as the linear Ag(CN)2 complex and adsorbs on activated carbon following the Freundlich isotherm. The uptake and rate of adsorption increase with the addition of KC1 and KNO3 but changes only slightly with pH. In contrast, the adsorption of Cu(I), Zn(II), Cd(II), and Hg(II) shows marked changes with pH, closely following the predominance profiles of their neutral and singly-charged cyano complexes. Clearly, multicharged negative complexes are repelled by the negatively-charged carbon surface. This sensitivity of activated carbon to the charge of the adsorbing species indicates that silver adsorbs as an anion, not chemically bound to the co-adsorbing counterions. For the same reason, activated carbon is selective to metals that form neutral and Singly-charged cyano complexes, namely gold and silver.

Jan 1, 1988

By R. A. Pimentel

Complying with reduced dust standards (i.e., less than 2.0 mg/m3) due to quartz levels that exceed 5 percent is presently a critical problem for many continuous mining sections. Results are presented of research which was performed to determine the factors causing high levels of respirable quartz dust and to identify the major contributors to operator exposure. It was found that the significant sources of quartz dust are the drilling of the roof and the mining of the roof, floor and rock bands. Both the miner and the bolter may be on a reduced standard, but compliance is easiest to achieve on the bolter for which improvements in maintenance and operator practices are usually sufficient. At the miner, the problem is more elusive. Research continues to identify operating and mining practices that contribute to the exposure..

Jan 1, 1985

By Robert M. Cox

Surface mining of coal in the South developed into a major industry during the 1960's. The economic significance of the industry is much greater than is readily apparent when one considers only the value of the coal mined. The abun-dant supply of relatively inexpensive steam coal for electric power generation that has been derived from the surface mines has provided the foundation for the industrial expansion that has occurred throughout the South. The region, in gen-eral, has enjoyed the benefits of plentiful low cost electric power. However, re-cent political decisions, at all levels of government, threaten to destroy or severely curtail the surface mining of coal and eliminate the economic advantages once enjoyed by the region. These political decisions are rapidly changing the basic rules of operation and fundamental economics of surface coal mining. Recent changes, resulting from the enactment of environmental and health and safety laws and various bureaucratic rules and regulations, have had a three-fold effect: 1) Greatly increased operating cost, 2) increased lead times for mine development, 3) limited potential reserve base for future mining. Also current legislative proposals are casting a shadow of uncertainty over the future of all coal mining operations that has created serious delays and in-creased cost for the expansion of the coal industry necessary to meet our project independence goals. Technology Surface mining is the safest and most economical way to produce raw materials from the earth's crust. It also affords a more healthier working environment for the individual miner. Surface coal mining now accounts for more than 60 percent of the annual coal production in the South. Surface mining of coal requires the removal of the overburden to expose the

Jan 1, 1977

By E. McCullough, S. Gaillard

"Diesel particulate matter (DPM) remains a health concern in many underground metal/nonmetal mines, and has been regulated by the Mine Safety and Health Administration since 2002. While the NIOSH 5040 standard method for DPM monitoring is required to demonstrate regulatory compliance, the FLIR Airtec DPM Monitor can serve as complementary engineering tool. It is a handheld instrument that offers near real-time measurements. As part of an ongoing field study, the Airtec has been used to survey elemental carbon concentrations (a proxy for DPM) in an underground stone mine. Via “spot-checking” and more prolonged area monitoring, this effort was aimed at determining spatial and temporal DPM variation in several key locations. INTRODUCTION Diesel particulate matter (DPM) is the solid fraction of the exhaust emissions from a diesel engine. It is largely made up of elemental and organic carbon (EC and OC, respectively), which can be measured as proxies for estimating mass concentrations of DPM. The National Institute for Occupational Safety and Health (NIOSH) considers DPM to be a health hazard and potential carcinogen [1]. It is believed to cause and/or exacerbate respiratory illness upon inhalation, deposition, and retention in lung tissue [2]. Since DPM exists in both the micro- and nano-particulate ranges, it can surpass typical auto-immuno defense mechanisms that keep larger particles out of the respiratory system [2]. Relative to other occupations, the DPM exposure potential for underground miners is high because these individuals work in enclosed environments where diesel powered equipment is frequently used [3,4]. A variety of engineering and administrative controls have been devised to reduce DPM exposures in underground mines, and increased airflow is often a key component of control strategies. In large-opening mines, which are most common in the metal/nonmetal sector, DPM abatement via increased ventilation can be especially complex due to moving and controlling the large air quantities [5]. The Mine Safety and Health Administration (MSHA) has regulated DPM exposure in metal/nonmetal mines since 2002. The final rule limits personal exposure to total carbon (TC, which is the sum of EC and OC) to an eight-hour time weighted average (TWA) of 160 µg/m3. To demonstrate compliance, operators must use the NIOSH 5040 Method [6]. However, the Airtec DPM Monitor (FLIR Systems, Inc., Nashua, NH) was developed as an engineering tool to provide near real-time measurements of both EC and TC for tracking personal exposures [7]. The portable Airtec works by capturing DPM on a filter and successively measuring laser extinction on the filter as DPM accumulates; the EC fraction of the DPM is dark, and so as it accumulates the filter becomes darker and absorbs more laser light [8]. The laser extinction value is directly correlated to EC, but since EC and TC are generally observed in consistent proportions (i.e., TC = EC*1.3), the Airtec is also programmed to display TC as a TWA [9]. There have been multiple studies conducted to validate the Airtec and the instrument has been adopted by some mine operators as a tool for their health and safety programs [3,8]."

Jan 1, 2016

The Colorado portion of the Rio Grande rift is clearly defined physiographically from the south in the San Luis valley northward to the latitude of Leadville where sediments of the Dry Union Formation (Tweto, 1961) accumulated within the subsiding rift zone. To the north of Leadville is a system of faults active in the late Tertiary, including the Mosquito fault that offset a portion of the Climax mineralization (Wallace et al., 1968). Tweto (197B) describes remnants of Dry Union Formation against the Mosquito fault north of Dillon in the Blue River valley, so it is apparent that the rift and associated sediments extended well to the north of Leadville. Kelley (1952, 1954, 1956) and Chapin (1971) have noted in New Mexico that the Rio Grande rift is a series of en echelon basins, offset to the east, with constrictions connecting them (Fig. 1). In Colorado the structural basins are offset to the west. The net effect of all the rift zone basins in New Mexico and Colorado is an arcuate pattern (Fig. 1) abutting the Colorado Plateau and Sari Juan Volcanic Province on the west. The width of the rift system gradually decreases northward to about Leadville where rift definition is not apparent.

Jan 1, 1987

By M. Prasad, G. M. Rao, A. K. Majumder, T. C. Rao

Froth flotation was employed to beneficiate a lean-grade siliceous rock-phosphate ore containing fluorapatite, the phosphate-bearing mineral. The main gangue minerals were quartz, iron oxides and aluminum oxides. After the rougher stage, four cleaning stages were required to upgrade the ore. The liberation size of the phosphate mineral was below 200 mesh, The reagent scheme consisted of commercial-grade sodium silicate and sodium oleate. The effect of reagent dosages, number of cleaning stages and pulp density on the efficiences of separation were studied systematically. A flowsheet was proposed for the processing of low-grade siliceous phosphate ore containing 12.1% P2O5, 55.36% SiO2 and 15.45% CaO. The flowsheet provided a useable phosphate concentrate containing 34.18% P2O5 and 14.20% SiO2 with a P2O5 recovery of 70.4% (the weight yield was 25.0%).

Jan 1, 1999

By Quansheng Li

Large-scale coal mining will cause environmental problems such as aquifer damage, land excavation and occupation, soil erosion, vegetation damage, and regional landscape damage. The existing coal mine environmental restoration technology is relatively simple, and there is a lack of systematic research on environmental total factors. Based on the mechanism of coal mining damage and the laws of environmental natural succession, the concept of “coal environmental protection mining” is proposed, which combines damage reduction mining and environmental element system restoration. In accordance with the environmental protection principle of “source protection, process damage reduction, and systematic restoration,” a technical system of “coal environmental protection mining” is constructed for the two types of mining damage scenarios: underground mining and open-pit mining. In view of the damage characteristics of underground mining, source environmental protection technology based on optimization of mining process parameters, stability maintenance and damage reduction technology for overlying rock bearing arch shell structure, zoning and time-sharing treatment of surface cracks, and direct drainage irrigation technology for mine water have developed. In accordance with the damage characteristics caused by open-pit mining, land-saving and source reduction damage technology, near-natural stratigraphic reconstruction, topsoil improvement, and environmental storage and utilization technologies for seasonal precipitation have developed. By applying the technology in this paper, the maximum surface settlement value of 12401 working face in Shangwan coal mine was relatively reduced by 25%, the surface cracks have been adjusted from step-type cracks to dynamic small cracks, and since the technical implementation of the Shendong mining area in 2010, the vegetation coverage has increased loss and crushing decreased by 0.06 km2 every year, the environmental restoration period of the dump site was advanced by more than one year, and the vegetation coverage rate increased by 41.78% compared with the background value in the semi-arid area of the victory open-pit coal mine demonstration area. A surface reservoir with a water storage capacity of 400,000 cubic meters has been built, and the seasonal and graded utilization of mine water has been realized. An underground reservoir with a water storage capacity of 1.22 million square meters has been built in the Baorixiler open-pit coal mine.

Jun 25, 2024

By Leonard W. III Joseph, William H. Buttermore

Noise control is an important consideration in the design and operation of coal preparation plants. It is essential to understand and control noise sources to provide a safe environment for operating personnel. The average noise exposure levels in a typical coal preparation plant generally range between 95 and 100 db. An operator should not be exposed to noise levels of this magnitude for more than 4 and 2 hr, respectively, according to MSHA (Mine Safety and Health Administration) regulations. The major noise sources in a coal preparation plant include noise from impacting the inside surfaces of steel chutes, vibrating screens, coal crushers, pumps, motors, fans, and blowers. The magnitude of noise varies considerably from one situation to another. NOISE EXPOSURE IN COAL PREPARATION PLANTS Noise regulations established by the Occupational Safety and Health and- ministration (OSHA) are accepted by MSHA relative to coal preparation plants. Fig. 14-43 shows a graph of the time of noise exposure in hours per day to which a worker can be exposed for each A-weighted sound level. According to this graph, a worker is permitted to spend 8 hr in a 90-db noise environment, but that time must be halved when the A-weighted sound level increases 5 db. The noise dosage a worker receives is determined by the ratio of the length of time the worker spends in a particular noise environment divided by the length of time he is permitted to spend in that environment. If the worker is exposed to several different sound levels, his total dosage would be the sum of each of the individual dosages. The equation for determining the dosage is: where C is the actual duration of exposure at a given steady state noise level and T is the noise exposure limit for the level present during the time C According to MSHA regulations, the dosage, D, should not exceed one (1) for any worker for a full day of work. As an example of typical plant noise levels, vibratory screens and crushers emanate noise levels in excess of 90 db at a distance of 3 ft (0.9 m) with no material flow. With material flow, noise level increases 1 to 10 db depending

Jan 1, 1991

By Cancelli Paolo, Bragonzi Gianluca, Pelizza Sebastiano

"In May 2015 the New Monte Bianco aerial cableway, operating on the Italian side, have been completed. It connects the lower station in Pontal d’Entreves (1300 metres above sea level (m a.s.l.)) with the intermediate station at Pavillon de Mont Frety (2160 m a.s.l.) and with the top station at Helbronner Peak (3460 m a.s.l.). A new underground link between Helbronner Peak and New Torino Refuge has also been built. The link is divided into two different sections: the first one, a 70 meters deep vertical pit created using the “Raise Boring”, descends underground from Helbronner Peak station; the second section, a 160 meters long sub horizontal tunnel, emerges at Torino Refuge. After a first introduction focused on the general layout of the project, the paper will present the geomechanical survey aimed to evaluate the effect of permafrost on the stability of intensely fractured granitic mass. Finally, it will describe the relevant issues related to the highest construction yard in Europe (3400 m a.s.l.): difficult conditions such as extremely cold and windy weather and restricted spaces. INTRODUCTION The new cable way connects the lower station in Pontal d’Entreves (1300 m a.s.l.), close to Courmayeur, with the top station at Helbronner Peak (3462 m a.s.l.) and its territory, as well as links with France and, through the French territory, with the town of Chamonix (1000 m a.s.l.). The overall layout is divided into two sections (as shown in Figure 1): the first section, “Pontal d’Entreves – Mont Frety”, has a length of 1700m, elevation differential of 886m, a capacity of 800 persons/hour and cable cars for 80 passengers; the second one, “Mont Frety – Punta Helbronner”, has a length of 2630m, elevation differential of 1276m, a capacity of 600 persons/hour, and cable cars for 75 passengers. The new system is designed for fully rotating cable cars moving at a constant rate of 9.0 m/s. The track requires constructing special cables supports, three for the first section and two for the second one."

Jan 1, 2016

By W. M. Ma, Daniel W. H. Su, K. Centofanti, Yi Luo, W. L. Zhong, Syd S. Peng

10.1 I~RODUC1'ION In order to understand the effects of surface subsidence due to underground mining on the ground water hydrology, a brief introduction to the rate, direction, and general pattern of ground water movement in aquifers is necessary. Ground water movement in an aquifer is controlled by aquifer lithology, structure, permeability, water levels, topographic set¬ting, and pumping patterns (Sgambat et al., 1980). Fig. 10.1 shows an idealized flow pattern of ground water in a hilly terrain (Coe and Stowe, 1984). The hill is made up of a series of interbedded permeable aquifers (mostly sandstone) and confining units (mostly shale). Since sandstone is porous and permeable, ground water moves through it downward and laterally until it reaches the interbeddings of the confining unit immediately below. The ground water then moves laterally along the interbeddings, be¬cause the confining unit is less permeable, and comes out as springs on the surface at the intersection of the aquifer and the confining unit. If there is a ground water table in each aquifer, it is a perched water table (e.g., right side of Fig 10.1). On the other hand, if the ground water recharge is larger than can be drained out, the interbedded permeable aquifers and confining units will be filled with water and a ground water table will exist only at the uppermost permeable aquifer. This is the semi-perched water table (e.g., left side of Fig. 10.1). There are three ground water flow systems: shallow, interme¬diate, and deep. Shallow flow systems occur near the land surface and the surface drainage system. The flow depth ranges from a few to several hundreds of feet with a resident time of a few weeks to a few years after entry, depending on the permeability of the rock strata. In a shallow flow system, the drainage coincides with sur¬face run-off water divides. Intermediate flow systems occur in minor hills some distance away from surface drainage. The travel distance ranges from several hundreds to several thousands of feet, the travel time from several months to tens of years. These systems are less dependent on seasonal recharge or discharge. In deep flow systems, the ground water travels from thousands of feet to miles, and transfers between surface basins. The travel time ranges from several tens to several hundreds of years. The systems generally receive recharge over a large area on major mountains and dis¬charge into major stream systems. 10.2 CASE STUDIES There are two ways of monitoring water wells for studying the effects of dewatering due to underground mining, i.e., water level and piezometric level. The water level is the water elevation in a water well that has penetrated two or more aquifers. Thus it indi¬cates the combined flow of all the aquifers that the water well intersects during the time of measurement. The piezometric level is the level to which water rises in a piezometer cased to a specific aquifer, and coincides with the pressure level of water in that aquifer. Therefore piezometric level reflects the water condition in that particular aquifer to which it is confined, while the water level represents the total yield of a water well without regard to the source of water. For instance, if a water well intersects two aqui¬fers, and if the lower aquifer is affected by undermining and goes dry while the upper aquifer does not, the water level in the well will drop, but may never go dry. Under this condition, the data obtained by monitoring the water level do not indicate the true behavior of the individual aquifers, especially if they are located at widely separated heights. 10.2.1 WATER LEVEL EFFECTS The effects of underground mining on ground water flow have been the subject of many investigations (Booth, 1984; Coe and Stowe, 1984; Owili-Eger, 1983; Rauch et al., 1984). However, the problems are very complicated, as have been exemplified by the conflicting conclusions reached by various investigators in var¬ious case studies. The most dramatic examples were described by Coe and Stowe (1984). In the first case (Fig. 10.2), the coal seam was 5 ft thick with cover from 400 to 800 ft deep. The majority of water supplies came from a sandstone aquifer in most ridge tops. When the face of the Panel No. 3 passed under it, dug well WW-1, which was approximately 670 ft above the coal, went dry, while the water level in Borehole B- 1, which was located at the center of Panel No. 4 with the bottom reaching the coal seam, also dropped about 160 ft. In Panel No. 5, the developed spring DS-2, which originated from the surface of the sandstone/shale contact and was approximately 750 ft above the coal seam, stopped when the face passed under it. The water level in the dug well W-2, which was dug into the shale about 700 ft above the coal seam dropped about 22 ft, but the well did not go dry. Therefore, nearly every spring or well located above or near the active panels was affected by longwall mining. In the second mine (Fig. 10.3), the seam was 5 ft thick with cover from 200 to 400 ft thick. Dug well DW-2, the bottom of which was 35 ft deep and approximately 330 ft above the coal seam in a perched sandstone aquifer, went dry right after the longwall passed under it. Drilled well W-3, in the sandstone aquifer, about 220 ft above the coal seam, experienced a 75-ft drop in water level when the face was under it, but showed some re¬covery after the face had passed under it. Ponds P- I and P-2 were developed in shale bedrock and were spring fed. They were not affected by longwall mining. Pond P-3 was developed in the sand¬stone aquifer, and its water table showed some decline when the face passed under it. Spring ST-1, which originated from Pond P-1 and was fed from several tributary valleys, was affected by longwall mining, probably because it passed across the panel edges where tension cracks drained off the water. Although the overbur¬den in case 2 was about half of that in case 1, the majority of water resources were not affected by longwall mining. Coe and Stowe (1984) attributed this discrepancy to: (1) a higher percentage of clays, shales, and claystones, resulting in a lesser degree of inter¬connected fracturing, and (2) a less rugged topography resulting in a less localized ground water flow system. Therefore, in order to assess the effects of underground mining, the premining ground water flow patterns, topographical, lithological, and meterological conditions must be known. Booth (1984) also monitored the ground water effects of a longwall mine (Fig. 10.4) in a seam 5 ft thick and 300 to 800 ft deep. There were three major aquifers: Morgantown sandstone approximately 30 ft thick and 630 ft above the coal; Saltsburg sandstone of up to 50 ft in thickness and 520 ft above the coal; and

Jan 1, 1992

By S. K. Nicol

The results of column flotation tests conducted on a bulk sample of ultrafines discarded from the fine coal desliming cyclones at the Riverside coal preparation plant of Theiss Dampier Mitsui Coal Limited are presented. A 9% ash concentrate was obtained from a 51% ash ultrafine feed at 75-80% recovery of combustibles in a single stage of column flotation. From this result it is predicted that installation of column flotation at Riverside would lead to the annual recovery of additional coal worth $US5.1M. The operating conditions for coal and copper column flotation are compared and some differences which may result in a variation in column design are noted.

Jan 1, 1987

By S. K. Kawatra, S. J. Ripke

Iron ore concentrates pellets are currently in duration heat hardened (sintered) under oxidizing conditions. Pellets produced from magnetite ore concentrate are completely oxidized during induration and finish as hematite pellets. These pellets then require a blast furnace to reduce the hematite to metallic pig iron. Partially reduced pellets would save energy and fuel during transportation and further reduction. It has been stated in the literature “the most important single factor responsible for the development of strength in fired magnetite pellets containing no additive is the oxidation of the magnetite to hematite and the subsequent recrystallization and grain growth of this constituent.” However experiments shown in this paper reveal that oxidation is not necessary to produce high-strength pellets. Magnetite concentrate pellets developed similar strength when indurated at 1350°C under either oxidizing (air) or inert (argon) atmosphere; the pellets sintered under argon remained magnetite. In addition, magnetite concentrate pellets indurated under reducing (CO) atmosphere also remained as magnetite, but required induration temperature of approximately 150°C less than the other pellets.

Jan 1, 2003

By T. Owen

Not since 1917 has a foreign company developed a standalone, grass roots gold mine in Russia. With. Russia's political changes of the late 1980s, development of mineral prospects once again beckons foreign investors. In 1990, Cyprus Amax began aggressively searching for such an opportunity. Early in 1997, production will commence at the Kubaka gold project located in the Russian Far East, near the Arctic Circle. The Kubaka project is a 1,750-tonne per day open-pit operation that will produce more than 300,000 ounces of gold per year. This paper discusses the challenges of locating such a prospect, doing business in Russia, developing supply lines, identifying work force capabilities, gaining government approvals, securing financing, arranging for gold sales and ultimately building a facility in this arctic region.

Jan 1, 1997

By Daniel Saramak, Agnieszka Saramak

A big issue in crushing and grinding operations in raw materials handling is high energy consumption and low breakage effectiveness. According to the Legendre [7], only 10% of energy input is directly consumed on the feed material breakage, while the remaining portion is dissipated in the form of heat and noise [8]. In the industry of limestone powder production, the grinding operations constitute integral part of technological circuits, and the energy consumption in operations of industrial comminution consume as high as 2% of world energy [14]. High-pressure grinding is the technology with proved energy benefits both in ore processing circuits and in limestone grinding. The promising results concerned mostly the achieved energy savings and good results of material breakage were achieved and demonstrated in numerous investigations [1,3,12]. However, it appears that a proper selection of operational parameters of the press devise, determination the feed material characteristics and adjustment of process course san be of a key-significance in improving an effectiveness the HPGR operation. Operational parameters of devices and process course should be verified towards the characteristics of the feed material, which mainly applies to the particle size and shape of the feed material and its moisture, and also mineralization in case of ores [2,4,9]. There are various investigations concerning an impact of the operational pressing force on comminution results which mostly refer to the determination of energy consumption and crushing ratio [5,6,10,13]. Investigations on the moisture content are less common, however their results suggest that, in general, the HPGR feed with higher moisture shows the tendency to higher comminution intensity, while the energy consumption increases together with increasing of feed material moisture. Investigations on olivine sand feed [11] showed that crushing ratio decreases for higher moisture, especially when the material is crushed at higher pressing force. HPGR devices, however, shouldn’t be regarded as a unique and perfect solution for comminution of each type of material. But they indeed may bring technological and economic benefits, comparing to conventional crushing and grinding machines, resulting in more favourable breakage of material particles and lower consumption of energy per unit mass of processed feed material.

Feb 1, 2025