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By J. L. Schroder, William J. Halvorsen, Wiliam W. Lyons, Kent C. Ware, Sheridan A. Glen, Donald C. Simpsom

The prospects for near-term growth in coal demand are exceptional: the federal government recently targeted 141 oil- and gas-fired generating units for mandatory conversion to coal; coal-to-synfuel developments are proceeding at a steady clip, with construction of a $1.2 billion gasification plant to begin this year in Beulah, ND; uncertainty over nuclear power and stratospheric oil prices enhance the steam coal market; the export market is ripening; and an influential new political force (the Senate Coal Caucus and Congressional Coal Group) is flexing its muscles on Capitol Hill. But the rosy picture is muddled by signals, often conflicting, sent out by federal agencies. Although EPA can be credited with relaxing its grip on the Clean Air Act, its sulfur dioxide control strategy is still often at odds with the Administration's call for domestic energy (coal) development. B. R. Brown, president of Consolidation Coal Co., sums up the situation: "Every mule is pulling in a different direction." Often in the midst of the fray is the small operator who has been hardest hit by the stagnation of coal markets. Layoffs, shortened work weeks, and mine closures were rampant in the eastern and midwestern coal fields, even among large producers. The longstanding boom in western coal was tempered during 1979 by a noticeable slowdown in announcements of new mine construction. The prognosis: Eastern coal will remain in the doldrums for quite a while to come as it works off some 90 Mt of overcapacity. Midwestern coal will fare no better due to the regulatory-influenced appetite of midwestern utilities for low-sulfur western coal. This displacement should ease, though, as new power plants equipped to burn high-sulfur coal come on line in the years ahead. In the West, the National Coal Association projects production to increase a healthy- 10% this year, although mine-to-market transportation looms as the single largest stumbling block to marketing efforts. Fatalities Up 40% in 1979 The National Coal Association estimated total coal production in 1979 at 671 Mt, an increase of 13% over 1978. Of this total, the East and Mid-west accounted for 476 Mt (71%) and the West produced 195 Mt (29%). With the consistent rise in western production playing against flat outputs in the East and Midwest, underground mining's share of total production continues to slip and is expected to account for only 38-39% in 1980. Incidence of deaths and injuries at US coal mines soared in 1979 over 1978 rates. MSHA figures (still subject to final adjustments) reveal a death rate of 0.07 per 200 000 man-hours, up 40% over 1978's 0.05 figure. MSHA chief Bob Lagather attributed the death incidence to the large number of new coal mines put on line in 1978, which he estimated at between 350 and 400. Nonfatal injuries rose to 8.48 per 200 000 man-hours, up about 15% from a 1978 rate of 7.35. In absolute numbers, MSHA counted 144 fatalities and 18 111 lost-day injuries during the 1979 calendar year. The 144 coal mining deaths in 1979 is the highest number of coal fatalities at US mines since 1975.

Jan 5, 1980

By S. C. Gambrell

The practice of roof bolting in world-wide mining activities is very well known, having been used extensively for over 50 years. The theory of roof bolting, however, is extremely complicated, and only recently have investigators attempted to explain the theory. Discussions of the mechanics involved usually originate with actual experience gained in the use of roof bolts. The use of roof bolting in mines has grown dramatically during the period after World War II. Other scientific techniques have emerged in mining research in the same period. Included in these techniques is the study of rock mechanics, which has now developed into an impressive research effort. Various means of analysis have been utilized in rock mechanics, most of which reduce rock to an isotropic, homogeneous medium that could be easily analyzed. Because of the inherent nature of rock, direct research methods frequently are not certain to provide satisfactory results, whereas indirect methods must idealize a given set of conditions in order to be useful. One of the indirect research methods is the photoelastic technique, the theory of which is widely known and needs no elaboration. This technique has been used extensively to examine the state of stress around underground openings of various shapes in certain types of strata, and under various configurations (1,2,3,4,5). Much of the theory used now in the design of underground openings is based on photoelastic evaluation. Unless rigorously applied, how- ever, the photoelastic technique is at best a qualitative means of evaluation. It is useful, however, for unusual examples which can be more or less easily analyzed to obtain the overall state of stress which could not be determined by other means. Little work has been done in the photoelastic analysis of rock bolting, mainly because direct research techniques have proven useful.

Jan 1, 1970

By A. Venkatachalam

Spinel ferrites, like NiFe2-2x Znx Ti4 O4 Fe CO1.5 Ge0.5 Tix O4, Ga1-x Fex Ni CO O4, Nil-x Fex Mn2 O4 have been prepared using the respective metal oxides in Stoichiometric quantities, by the ceramic method. The oxides were homogenized in acetone medium, pelletifed by using poly vinyl acetate as the binder. They were fired at 1000°C for 100 hours for compound formation. Chalcogenide spinels such as Zn1-x Cux Cr2 Se4 where 0=x=l and Cu1-x Fex Cr2 Se4 where 0=x=0.3 have been prepared by using 99.99% pure elements and then fired at 1000°C in quartz ampoules under vacuum conditions. X-ray diffraction studies of these compounds indicated a single cubic spinel phase. DC resistivity studies of the compounds were taken between 300-700K using LCR bridge by two probe technique. Thermo-electric power measurements were taken between 300-500K for all the compounds. Initial susceptibility studies have been carried out using a low field (0.506) and from which the nature of magnetic dimains and Curie temperatures were determined. Magnetic hysteresis measurements were carried out at 300K and at 80K, using alternating current hysteresis loop tracer, at 2K02 field. Mossbauer spectral measurements were carried out using Co57 source embedded in a copper matrix and an absorber containing 0.3 mg/cm2 of the sample. The spectra has been fitted by Mossfit Program. The catalytic effect of the spinel ferrites NiFe2-2x Znx Tix O4 where 0=x=1 has been studied by using the model reaction of decomposition of H2O2 at temperatures from 40°C to 70°C. It was found that the spinel oxides were found to possess poor catalytic activity.

Jan 1, 1990

By G. E. Karantzavelos

Introduction Pure alunite (KAl3 (SO4 )3 (OH)6 ) contains 37% A1203. In the alunite ore found on Milos Island, Greece, opal is the principal gangue while some aluminum, iron, and titanium oxides are also present. Processing of alunite ore leads to the recovery of potassium sulfate, alusil (alumina-silica mixture), and sulfur dioxide. An interesting process has been developed in Greece (Svoronos, 1977) consisting mainly of roasting the alunite ore mixed with KCl to disrupt the mineral lattice in preparation for separating its components. The thermal decomposition of alunite at approximately 600°C occurs by the reaction: KAl3 (SO4)3 (OH)6 + nSiO2 + 6KC1 - 4 K2SO4 + 3 A1203 . nSiO2 + 6 HCl + 3H20 According to the process pure alunite mixed with 543 kg KCl, 840 kg K2SO4, 370 kg alusil, 264 kg HCl, and 65 kg H2O are produced. The roasted calcine is leached in hot water. The potassium sulfate leach slurry is then thickened and washed to obtain a solid residue (alusil) plus a solution rich in potassium sulfate. Assuming the alunite ore feed consists of 50% to 60% alunite, the solid residue might consist of approximately 22% to 27% A1203, silica, iron, and titanium oxides. This leach residue could be digested in a hot sodium hydroxide solution to dissolve alumina. An amount of the alumina (approximately 10%) would not dissolve. In addition, part of the silica would dissolve requiring removal from the solution in a subsequent desilication operation. The same leach residue could be attacked by mineral acids such as a diluted hydrochloric acid to extract aluminum chloride (Sawyer et al., 1983). Alumina and aluminum are presently produced from bauxite of which Greece has important reserves. If this aluminous material (alusil) could be beneficiated by any physical process, then it would be considered as a raw material for the production of fire-clay refractories instead of an alternate source of alumina. Experimental procedure Extensive laboratory work (mineralogical and chemical analyses) indicates that alusil is a mixture of liberated (mostly) alumina and silica particles, not a natural silicate mineral. Table 1 shows the chemical assays of two alusil samples that were obtained from a roasted alunite ore leaching pilot plant. The samples used for the experiments were a very fine alusil powder (K80 = 400 mesh, 38 µm). These were pulped in tap water. Desliming of the pulp before each flotation test was ineffective. Flotation tests were performed in a 2000 ml Denver cell. A standard 500-g sample was first conditioned at a pulp density 50% solids for 5 min with hydrofluoric (HF) acid solution (40%). The temperature of the conditioned pulp was measured and kept nearly constant at 50°C. The pH of the conditioned pulp was also regulated to 2.5-3 with HF solution. Then ARMAC C solution (2%) as well as two drops of fuel oil and one drop of AEROFROTH 65 were added and the pulp was reconditioned for 2 min. After conditioning, the viscous pulp was transfered to the flotation cell. It was then diluted with warm water to about 15% solids and floated to separate silica from alumina particles. A rougher froth product that was cleaned and recleaned was obtained from the flotation tests.

Jan 1, 1987

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

5.1 INTRODUCTION There are several types of surface ground disturbances, each of which is immediately transmitted to surface structures and causes damage of various forms, depending on the location of the structures in the subsidence basin. Many criteria have also been proposed for defining the potential structural damage. All of these topics will be discussed in this chapter. 5.2 TYPES OF GROUND DAMAGES There are two types of ground damage, continuous and dis¬continuous, that could inflict damages to surface structures. Dis¬continuous ground damage is open fractures of various degrees. Four types of fractures are commonly seen (Brauner, 1973b): 1. Fissures or cracks. Cracks are the most common form of ground damage and range from completely closed to several feet wide. Surface cracks are most prominent when the ratio of mining depth to mining height is smaller than 30 to 50 times mining height. Cracks initiate parallel to, but ahead of the moving long¬wall face at some intervals when the depth-to-mining height ratio is less than 25 to 30. As the face continues to move, they open up and then close gradually, and in most cases eventually close up completely when the face moves farther away. Sometimes when the depth-to-mining height ratio is larger, cracks may initiate be¬hind the face and go through the same cycle. Cracks are also more likely to occur in the hill when the face is moving in the uphill direction. Cracks also occur at or near both sides of the panel edges. Those cracks tend to remain open permanently. When the surface is covered with grass or other vegetation, cracks of less than 1 to 2 in. wide usually do not penetrate it and become invisible on the surface. 2. Steps. A step may occur when the longwall face stops abruptly if the mining depth-to-mining height ratio is less than 20. Steps may also occur along the panel edges. Steps also range from a few inches to a few feet in width and depth. If planes of weakness are oriented favorably, ground will slide along these planes and form steps on the surface. 3. Cave-in pits. These result from local collapse of the ground from the mine level to the surface when the mining depth is less than 150 ft and occur mostly above abandoned mined lands. They may be as large as 40 ft wide and deep. 4. Bumps (compression ridges). Bumps result from ground compression and occur mostly near panel center some time after mining. Bumps of up to 4 ft, but mostly 1 to 2 ft, have been identified. Continuous ground damage refers to the formation of the sub¬sidence basin where continuous nondestructive ground deforma¬tions occur. As mentioned earlier, continuous ground deforma¬tions associated with a subsidence basin include subsidence, slope, curvature, displacement, horizontal strain, twisting, and shearing. 5.3 TYPES OF SURFACE STRUCTURAL DAMAGES Both continuous and discontinuous ground disturbance cause damage to surface structures. A. Structural Damages Due to Discontinuous Ground Disturbance 1. Fissures or cracks. Open cracks can cause dislocation of surface structure if the gaps are sufficiently large so that the struc¬tural elements cannot resist but fail. On the other hand, minor cracks affect only the appearance, and not the structural integrity. 2. Steps. When a surface structure is located on a step, some portions of the structure lose support and become overhung. In the case of a residential house, there will likely be many open frac¬tures in the overhung portions, followed in severe cases by sepa¬ration of the superstructure at the edge of the step. 3. Cave-in pits. If the caved-in pit is larger than the surface structure, the structure will drop into the pit and become unstable. If the caved-in pit is smaller than the surface structure, the struc¬ture may either become overhung or lose support in some portions. In either case, it is unsafe for use. 4. Bumps (compression ridges). Bumps will disrupt roadways or house floor. If located under supporting members of the struc¬tures, it may cause damages. B. Structural Damage Due to Continuous Ground Disturbances 1. Subsidence. Pure subsidence or uniform subsidence over an area does not cause any structural damage. However, if it becomes a topographical low area, it may be flooded with water and make the surface structures unusable. It must be noted that the flat bottom area at the center of the final supercritical subsidence basin does not reach that position suddenly. Rather, as shown in Fig. 3.1, it is subjected to the dynamic surface deformation asso¬ciated with the traveling subsidence basin before it is left behind to be part of the flat-bottom area. Therefore any structure located at the center of the final supercritical subsidence basin must be able to resist the dynamic surface deformation in order not to be dam¬aged. 2. Slope. Ground slope will induce tilting of the structure. Tall structures with small base areas, such as water towers, chimneys, and power transmission towers are most sensitive to ground slope. If the ground slope is such that if after tilting the center of the gravity of the tilted structure falls outside the base area, it will topple, but this seldom occurs. Ground slope will change the designed slope of a buried trans¬portation pipeline, either increasing or decreasing the original slope depending on whether the ground slope coincides with or opposes the original slope. There are maximum allowable final slopes for various types of transporting materials. Ground slope also affects highways and railways. There is a maximum allowable final slope for a railway because tractive effort increases 1/1000 of its weight for every increase of 1/1000 in grade. 3. Curvature. There are positive (convex) and negative (con¬cave) curvatures. When a surface structure is located on a positive curvature, both ends become unsupported, followed by bending upward at the midportion. The top portion is subjected to more severe stretching than the lower one. As a result, vertical cracks with a wider gap at the top occur at the window, door frames, on the walls, and at -the wall joints. V-shaped cracks appear at the

Jan 1, 1992

By Michael E. Salovich

The U. S. Department of Interior, Bureau of Mines (Bureau) has developed a prototype version of a computer application that combines hydrologic analysis with object-oriented graphics. This software is unique in that it presents analytic element analysis within an object-oriented CAD environment. Its user interface employs mouse handling, scrolling windows, dialog boxes, palettes, and pulldown menus. It can import scanned images of maps and overlay these images within the same window. This application was developed using object-oriented programming techniques. Several programming issues concerning graphics had to be resolved during development of this system. These include (1) how to represent hydrologic elements as graphical objects, (2) how to translate screen coordinates to map coordinates, (3) how to implement ?zooming? (changing the magnification level of a window), (4) how to overlay layers of images, and (5) how to import scanned images of maps. An object library was used to implement graphical user interface features such as scrolling windows and pull-down menus. Algorithms for CAD features such as map coordinate translation, zooming, and the layering of images were developed by Bureau researchers. The application has a modular source code structure and can be modified for use in other research applications.

Jan 1, 1992

By B. J. Arnold

Coal froth flotation cells typically receive little attention in coal preparation plants. They process only a small portion of the total coal feed (perhaps 5-1 0% of the total plant feed in the United States), they are viewed as a way to take the load off the refuse thickener, and their operation is not well-understood by cleaning plant operators. Operating parameters are set based on the equipment supplier information, and reagent dosages are set at the recommendation of the latest chemical vendor. The cells then operate day in and day out, recovering coal and producing a product that may not meet ash or sulfur specifications or that may be the wrong percent solids for downstream dewatering operations. If improvements can be made to this circuit, then the whole plant will benefit. Paying attention to rate and residence time and the wealth of data from the literature or from a series of targeted laboratory tests can give operators the key to improving the performance of froth flotation cells AND overall plant performance. This paper provides an overview of froth flotation rate and residence time data and gives practical suggestions for specifying and using laboratory tests to improve froth flotation performance. Suggestions for improving froth cell performance are also given based on available literature data.

Jan 1, 1999

By V. C. Kelessidis

Demand for multifunctional drilling fluids continuously increases. In the quest for more hydrocarbons, drilling has extended to deep water areas (now in excess of 2.000 m) and to very deep wells (now in excess of 6.000 m). In these extreme conditions, low temperatures, as low as 1-5°C on the sea bed, high temperatures, in excess of 200°C, and high pressures, more than 1.000 bars, in the bottom of the well, are frequently encountered. In these harsh environments, synthetic oil and oil based drilling fluids are used, but the former are expensive while strict environmental requirements have limited the use of the latter. Thus, drilling industry has turned back to water based drilling fluids which use bentonite as primary viscosifier and as a fluid loss control additive. However, in conditions of high temperatures, bentonite suspensions gel and loose their exceptional low temperatures properties, thus, additives are needed to overcome such problems. In this article we review these challenging drilling environments and establish the requirements for the multifunctional drilling fluids. Our research indicates that demand for continuing use of bentonite by drilling fluid industry is strong. Furthermore, we bring forward the opportunities for new additive development which can expand the operational ranges of bentonite suspensions.

Jan 1, 2007

By P. D. Roa, O. Noirot, H. Owens, D. E. Walsh, J. R. Mokka

Over a period of eight years (1989 through 1997) the Mineral Industry Research Laboratory (MIRL) at the University of Alaska, Fairbanks, AK, has investigated the effects of temperature, residence time and particle size on the degree of low-rank coal (LRC) upgrading for a nonevaporative, hydrothermal drying process, also known as hot water drying (HWD). The following three Alaskan LRCs were used in this study: Usibelli coal (Seam No. 4) from the Nenana Coal Field, Little Tonzona coal from near McGrath, and Beluga coal from the Beluga-Yentna field on the west side of Cook Inlet. Replicated factorial tests were conducted. Experimental results indicate that most of the low-rank coal upgrading via HWD occurs rapidly within the first 10 to 20 min of residence time. Thereafter, the upgrading process slows down, and more than 100 min of additional residence time is required to produce percentage increases equivalent to what was achieved in the first 10 to 20 min. The properties of the hot water dried products were very sensitive to process temperature. Calorific value, carbon and oxygen contents, equilibrium moisture levels and Hardgrove gindabilities all appear to change linearly with temperature within the 275°C to 325°C (525°F to 61 5 OF) range.

Jan 1, 2000

By Z. T. Bieniawsk, C. A. F. F. Santos

The effects of artificial weathering on the mechanical properties of the Loyalhanna sandstone have been investigated. Weathering was simulated in the laboratory by subjecting cylin- drical specimens of rock to alternate cycles of wetting and drying (in distilled water at 2O0C 2 5OC and in an electric oven at 105OC t 1°C, respectively). The total number of cycles was 100 and the geomechanical characteristics of the altered material were determined through uniaxial compressive and indirect tensile ("Brazilian") tests, with the determination of axial and trans- verse strains and monitoring of acoustic emission activity (rate and total event count). Moisture content and weight loss data were collected after each cycle and the mechanical parameters (unconfined strength, indirect tensile strength, young's modulus, Poisson's ratio, permanent set and AE/MS activity) were determined for unweathered specimens and after 10, 20, 50 and 100 cycles of wetting and drying. Hypotheses for the effect of weathering on the geomechanical properties of the Loyalhanna sandstone are proposed as reinforced by petrographic analyses carried out for the different stages of artificial weathering. A methodology for assessing the degree of physical weathering of rocks is proposed based on the number of wetting and drying cycles.

Jan 1, 1986

By A. T. Yu

Technology and economies of scale have, in the past decade, brought about the emergence of giant vessels. Meanwhile, to answer the need for rapid dispatch, as a means of combating the proportionately far greater demurrage charges, shiploading and unloading speeds have soared (Ref. 1, 2, 3). As the loading and unloading rates have dramatically increased, so has the cloud of dust grown in unbearable proportions. It not only has threatened to be a real menace to machinery and men, but in certain instances has also seriously jeopardized fish and marine life (Ref. 4). In an era when ecology is king, dust in shiploading and unloading can no longer be shrugged off as a mere public nuisance, and its control is now duly recognized as of grave concern to all. Even if public outcry were not a problem, from the operator's own parochial point of view, dust can adversely affect productivity and the well-being of the operating personnel. Without adequate control, it can also result in costly equipment maintenance, particularly when the dust is micronic in size, and abrasive. The Hierarchy of Control Techniques Given the great fortune of not yet having to deal with gas and odors, in the jargon of pollution control, our problem is confined to having to control "particulates" only. To deal with "particulates", the myriad of dust control techniques can be utterly confusing to those who are not entirely well versed in the methodology. Our analysis of what is available to date results in the following hierarchy of logical preferences: 1. Prevention 2. Removal 3. Suppression 4. Containment 5. Dilution Since it deals with the root cause, prevention always outranks the cure. Once the dust is generated, removal nips it in the bud. Only when dust removal is

Jan 1, 1972

By M. J. Garcia, Howard Hallman, G. M. T. Marshall, Ken Higby, Louis Cope, Robert S. Hess, John Peters, A. G. Law, William C. Larson

After a good year in 1979-strong mineral demand, adequate prices for most metals, minimal labor problems-1980 was not so good. The US produced $24.8 billion worth of nonfuel minerals last year, up 3.5% from 1979, according to preliminary US Bureau of Mines figures. But the $800 million increase was the smallest annual gain since 1977 and reflected reduced auto and construction industry demand, strikes, and energy shortages. Preliminary figures for 68 minerals show that production of 42 decreased, 25 increased, and one was unchanged. Production of 11 of 21 US-produced minerals was up. Noteworthy mineral events in 1980 included a copper industry strike, increased gold and silver prices, troubles in the iron ore and uranium industries, discussion about a US nonfuels mineral policy, and corporate interest in mining companies as merger targets. Recessionary conditions experienced by the Western world in 1980 resulted in a slowdown in new mine development, evident in the relative scarcity of major new base metal projects. This could lead to short term supply/demand anomalies within the next few years which, in turn, could have a significant effect on metal prices, according to Mining Magazine (Jan. 1981). World Mining (Sept. 1980) noted that US mining strength is in open pit operations. A much lower tonnage is mined underground and is centralized in trona, uranium, lead, zinc, molybdenum, potash and, to a lesser extent, copper. The most notable increase in new underground mines has been in Wyoming's trona district where new mines are being developed and production will increase, the magazine said.

Jan 5, 1981

By P. M. Fozzard

The Chaucha porphyry copper/molybdenum deposit was discovered by a United Nations team of geologists working with a ?counter- part" team of staff of the Ecuadorian government's General Directorate of Geology and Mines (DDGM) in July 1968. The exploration program formed the latter part of phase I work plan of a two-phased exploration project financed by the United Nations Development Programme and initiated in late 1964. The author was a team geologist during the period 1965-1967 and subsequently project manager for the period 1968-1972. The Chaucha property lies some 10 km (6 miles) east of the north- south-running western boundary of what was known as Operation Area No. 5. This area of some 10 500 km2(4050 sq miles) is a square truncated to the southeast and centered on the city of Cuenca, the major provincial capital (Azuay Province) of southern Ecuador. The eastern half of the exploration area is dominated by the Cretaceous- Tertiary sedimentary valley (basin) of Cuenca (Caar-Azuay) and its related drainage area. The western half, in which Chaucha lies, is dominated by the high Cordillera Occidental volcanic plateau and the western erosional valleys of the Andes draining to the Pacific. The valley that dominates the eastern part of the area [I500 m (4920 ft) above sea level] is transected by the Pan-American Highway. Because of increased agricultural activity associated with the Cuenca Valley, the area is reasonably well covered by a road network of varying quality. The high western area up to 4000 m (13,120 ft) in altitude is largely barren and completely inaccessible by vehicle. The geological reconnaissance map of the region is shown in Fig. 1.

Jan 1, 1991

By Andrzej Frycz

The development of the theory of reliability creates more and more possibilities of its application in different domains of technics. The methods evolved to date, both theoretical analysis of the engineering systems and investigations techniques in practice can be put in use a d translated from one science to another one [1,3,7J . It needs to consider the specific of the different sciences. But it is necessary to take account of the specific characteristic of each line of science. The reliability investigations needs, justified in technical and economical viewpoint appear too in mine ventilation technics and systems. The mine ventilation system is a complex of workings and ventilation plants, which serve to supply the networks with a sufficient quantity of fresh air from the atmosphere and then carry off the vitiated air. The condition necessary for a ventilation system to perform definite task is the correctness of all its elements, that is a capability to preserve in a expected range of tolerance, the values of basic parameters. The element of a system which ceases to work correctly is called failed. The basic parameter of all elements of a ventilation system is the characteristic curve, pressure loss - air quantity relation ?p = f(Q) (1) This curve concerning the workings and ventilation stoppings is given by the formula: ?p = R Q2 (2) thus the resistance R (of the workings or stoppings) may be taken as a characteristic parameter. The course of this characteristic f(Q) will be given in a complex form in concern with fans, ejectors, air curtains. The failure of a ventilation plant or working is therefore an event, relying on a change of its characteristic, thus for a definite time the losses of the plant's or working's capability set in for the fulfilment of its function in the ventilation system. The failures are divided in viewpoint of their nature on sudden and progressive. We are in concern with the sudden failures which are characterised by a violent change of the ventilation element parameter for example a fall of roof, or silt up of the working, opening or failure of the ventilation stopping, the stand-off of the fan or ejector etc. We distinguish two kinds of failures on the viewpoint of their action on the air flow: the "opening" failure and "closure" failure. The prevalence of factors, which causes the failures is in connection with the intersection in the mine of roads of haulage, roads of underground transport of materials and lining elements, roads of people motion with airways, as also depends on the rock pressure reaction on the workings lining and plants placed there. Other factors will yet be decisive upon supply decay of fans, ejectors and curtains. The appearance of failure of the ventilation element is therefore of random nature and determines the change of the element, when it is passing from operating state to unoperate. Qualifying the ventilation system element to one of these states is easy, when the characteristic change is clear and occurs suddenly, that was assumed. The investigations conducted by Patrushev and Karnaukh [91 in concern with the ventilation stoppings resistance change in the case of their opening, had shown the possibility of resistance value change in the range of several hundreds higher.

Jan 1, 1980

By C. H. Lee, F. Concha, L. G. Austin, P. T. Luckie

The Concha-Almendra batch-settling treatment for concentrated suspensions of single-diameter spheres has been modified. This modified version is used in the differential equations of simple batch settling of a particle size range of different density materials. The equations have been programmed for a finite difference solution, and a number of test cases have been analyzed. By cutting the settling column at a fixed fractional height, the material below this height can be treated as underflow and the material above as overflow. The predicted partition curves obtained from treating the settling in this way have Sharpness Indices in the range of 0.5 to 0.6, in the absence of dispersion effects. The Sharpness Indices decrease as dispersion increases. When the feed size distributions are of the Rosin-Rammler form, the partition curves (corrected for the bypass fraction) fit the Rosin-Rammler equation with reasonable accuracy. The predicted Sharpness Index of a component of a mixture of two materials of different densities was unchanged from that of the same materials settled alone. However, for the same, feed size distribution and volume fraction of solids in the feed, the heavier material settled faster, and the lighter settled slower, than when settled alone.

Jan 1, 1993

By Lynn I. Kelley

Industrial-mineral production contributes on the order of CDN$1.5 billion per year to the economy of Saskatchewan, Canada. Potash is the primary industrial mineral produced in the province, followed by aggregate, sodium sulphate, salt, potassium sulphate, peat, clays, silica sand, calcium-chloride brine, and "clinker." Potentially economic deposits of kaolin, diamond, and building stone are under evaluation. All of the major deposits of commodities discussed here are located south of lat 56°30'N. Most of the locations are presented on Figure 1 POTASH Saskatchewan supplies approximately 30% of the world's demand for potash. Eight conventional underground mines and two solution mines produced an all-time high of more than 13 million metric tonnes of potash (KC1) (8 million tonnes K2O equivalent) in 1997, valued at over CDN$1.4 billion. All of the mines exploit the middle Devonian Prairie Evaporite. The four potash-bearing members of the Prairie Evaporite underlie much of southern Saskatchewan and extend southward into North Dakota and Montana and east- ward into Manitoba (Fig. 2). Halite and anhydrite separate the potassic members. The evaporite beds locally are interrupted by solution structures (anomalous ground). Some of the structures may be related to deep-seated tectonic features.

Jan 1, 1999

By Carl H. Eckert, James P. Berson

INTRODUCTION The demand for specialty metals in industrial applications is in it's healthiest state since the late 1970'8, and several specific markets are recording record sales. Such metals as gold, silver, zirconim., titanium, beryllium, gallium, germanium, the platinum group, and the lanthanides accounted for sales in excess of $2 billion in 1985 among the end uses covered in this report. Although specialty metals as a group have suffered the effects of recessionary pressures in the past, these metals have proved more resiliant than such large volume metals as copper and nickel. This is due to the unique physical properties they possess which makes the threat of substitution or replacement through technological development uneconomic. The outlook for these specialty metals is optimistic in electronics, catalysts, ceramics, and alloys, and their specialty status results .in a combined average annual growth in demand of 7% through 1990. WHAT MAKES THESE METALS SPECIAL? Such characteristics as electrical conductivity, corrosion resistance, catalytic activity, thermal stability, and optical properties allow the term specialty to be applied to these metals. More importantly, all of these metals possess more than one of these qualities, as shown in Table 1. [ ] These five major functions are important in the end uses for these metals, although the specific applications vary somewhat. Conductivity in term of low or high electrical resistance is of obvious importance to electronics manufacturers. Producers of circuit boards or semiconductors require such metals as gold, palladium, platinum, and gallium due to their low electrical resistivity. However, these producers also require such metals as beryllium in the oxide form for insulation components because of the compound's low electrical conductivity. Although the lanthanides' conductive characteristics are not particularly attractive in electronics, they are of great importance to alloy manufacturers producing permanent magnets for automotive and computer applications. Corrosion and wear resistant properties are extremely attractive to a number of end-use industries, particularly in view of the estimate by the United States Bureau of Mines that $10 to $50 billion in losses are experienced by U.S. industry due to equipment corrosion and $100 billion due to equipment wear. The strength of high purity titanium and zirconium make these metals the obvious choice for corrosion and wear resistance particularly in the chemical processing industry, where the ability to maintain integrity in corrosive environments is a must. Heat exchangers, nuclear control rods, and a number of parts in jet engines have benefited greatly from the use of these metals. However, such other specialty metals as beryllium, and the lanthanides also improve the wear or corrosion resistance in various products. For example, a beryllium-copper alloy contact maintains it's spring like character, and does not loose this character after repeated use, which could result in the loss of an electrical contact. Lanthanide, in the form of cerium oxide, is commonly employed in alloys used to produce catalytic converter casings for the purpose of reducing damage by corrosive road salt. In some instances, the catalytic activity of several of the specialty metals assists in the economic production of other materials. However, the importance of specialty metals in catalysts is most apparent in catalytic converters for emission control. Platinum, palladium, and rhodium are

Jan 1, 1986

By Clay Haynes, Tim Pearia, Robert Robinson, Judy Cochran

A 1.89 km-long, 4.5 m-I.D. tunnel was successfully constructed through saturated hard clay, and highly abrasive dense sand and gravel, with groundwater heads ranging from 10 to 20 m. In order to address these conditions, a Lovat earth pressure balance TBM was used, with soil conditioning by foam, water and various polymers. Support was provided by a single-pass segmented concrete lining. Groundwater inflows of 400to 1,600 lpm at times created challenges for changing cutting tools. Surface settlements were generally less than measurement thresholds, except under very low cover at startup. This project provides a pivotal case study of the successful application of EPBM technology in saturated, abrasive glacial soils and the successful application of soil conditioners.

Jan 1, 2003

The classical slope analysis and a statistical technique were used in order to determine the iron complexes formed in the organic phase during the extraction of Fe(III) from Fe-Ni-Co sulfate solutions with Di-(2-ethylhexyl) phosphoric acid (D2EHPA) in kerosene. Equilibrium constants for the extraction based on these complexes were also calculated. The complexes determined were of the general form (Fe(OH)3-nRn?sHR)x' where n varied between 1 and 2.5 and s between 0 and 3, and both were found to be decreasing as the iron loading in the organic phase increased. Values of 1,2 and 3 were generally found for x, indicating that the complexes were monomers, dimers and trimers.

Jan 1, 1988

By F. M. Doyle, Robert G. Robins, E. Peters

Stability diagrams for the Cu-S-H2O system have been widely applied over many years. Stability diagrams for aqueous systems generally, have been generated by computer, but with the programs for Potential-pH diagrams in particular, a common routine leads to error in multi-element systems. In this paper these errors, and some misinterpretation of diagrams are considered. In most of the published diagrams for the Cu-S-H2O system there has been no account of the sulfide complexes of copper. Here, the free energies of formation for the various species in the system have been re-evaluated for consistency, and some diagrams for the Cu-S-H2O system ( generated with the program DIASTAB Vers.5 ) are presented.

Jan 1, 1993