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By P. Arell, D. Folkes

This paper presents the basics of EPA’s Hazard Ranking System (HRS), which is used to evaluate sites for possible inclusion on the Superfund National Priorities List (NPL). The paper describes the surface water, ground water, air, and soil exposure pathways and how they are applied to mining sites. Key factors contributing to the site score include the likelihood of a release, waste characteristics, and the targets for each pathway. Waste volumes, definitions of landfills versus surface impoundments, and background concentrations are of particular importance to mining and smelting sites. Because of the presence of metals, large waste volumes, and observable releases, mining and smelting sites often receive high enough scores to be proposed for the NPL based on a single path-way. Neverthess, owners and operators can take steps to reduce the risk of being scored, and to reduce the potential for high scores.

Jan 1, 2004

By Scott K. Palm

The initial intent of the Hazard Communication Standard (HCS) was to improve worker health by providing more information about the hazards of chemicals used in the workplace. However, the impact of the HCS goes well beyond worker right-to-know. There are direct costs associated with compliance. In addition, labelling and hazard communications can provide a competitive advantage to producers of minerals that have not been identified as hazardous. Often, the lack of hazardous information about a substance is due to the lack of scientific study, rather than an indication of product safety. Currently, industry and regulators sometimes give known hazards greater weight than unknown risks.

Jan 1, 1991

By H. G. Naidu, Raj K. Singhai, S. P. Singh

Introduction The economics of open-pit mining de¬pend heavily on the cost of overburden removal. It is necessary to maintain a pit slope as steep as possible. Steeper slopes lower the volume of overburden to be handled, thus lower the cost of material handling. There is, however, a limit to which the pit slopes in any given situation can be steepened. Steepening beyond this point could jeopardize the pitwall stability, ren¬dering it unsafe. It might even result in curtailment of pit production. Several factors affect the stability of pitwalls. Some are natural, such as topogra¬phy and regional and local geology. Others are man made, such as pit geometry, ground water management, equipment, drilling and blasting, and the type of excavation. Greater control can be exercised in the latter with proper planning and by following a set of procedures based on field experiences. This article deals with one such control¬lable factor - drilling and blasting. The eco¬nomics of steeper pit slopes is discussed, followed by a record of drilling and blasting practices in western Canadian surface mines. Microprocessor-based instrumentation and its application to blasthole drilling is also described. Economics of steeper pit slopes The economics of steeper pit slopes is not a new issue. It should be reinforced, though, that pit slopes must be as steep as possible to ensure maximum recovery of minerals at a minimum stripping ratio. For operating, economic, and safety reasons, different pit slopes are maintained during different phases of pit development. Figure 1 shows a hypothetical ore body, cylindrical shape, with a radius of 225 m (740 ft) and located 30 m (100 ft) beneath the surface. The mining operations are planned at two different slope angles of 25° and 40°. The ultimate pit depth was established on the basis of the criterion of "break even pit." The variation of the stripping ratio at differ¬ent mine levels is shown in Fig. 2. Table I summarizes the eco¬nomics involved for two pit slopes, 25° and 40°. Figure 3 presents the profits during the life of the mine for these two pit slopes. This study shows that steeper slopes for an open pit operation are far more advanta¬geous than flatter slopes. But, what is the optimum slope at any one point in the life of a moving pit? And how can the stable slopes be maintained over the short- and long-term? Canadian blasting practices A survey of blasting practices in western Canadian surface coal mines revealed that, at most mines, hard consolidated overburden is drilled and blasted. Blastholes are drilled with rotary crawler-¬mounted rigs using bits in the 220 to 310 mm-diam (8.5 to 12 in.-diam) range. Typi¬cal hole depths are 12 to 18 m (40 to 60 ft) to accommodate the pit bench heights of 12 to 15 m (40 to 50 ft). For a 12-m (40-ft) high bench, a typical hole will be 14.6 m (48 ft) deep including the subgrade drilling of 2.6 m (8.5 ft). Half of this hole will typically be a powder column and half will be stemmed. For a 15-m (50-ft) bench, a typical hole will be up to 18 m (66 ft) deep including the subgrade drilling. Drilling patterns are usually 9 m (29.5 ft) spacing and 9 m (29.5 ft) burden. De¬pending on local geology and hole diameter selected, drilling patterns of 8 x 8 m, 8.5 x 7.3 m, and staggered patterns of 11 x 5.5 m

Jan 1, 1989

By Thomas D. Kaufmann, Robert C. Drury

Few factors are as important as fluctuations in aggregate economic activity and exchange rates in determining the profitability of mineral investments. Macroeconamic theory explains how the two factors are interconnected in today's world and in tomorrow's. We can use macro¬economic theory to lessen some of the risks in mineral investments. And in the current state of the world the risks are high. The above paragraph summarizes our argument. Our goal in this paper is to examine the nature of contemporary business cycles so as to explain their implications for the metal industries, particularly the implications for capacity. Thus, our first section examines the workings, causes, and history of the recent economic fluc¬tuations. In doing so we must understand how current world economy is interconnected, that is, how economic events in one country are trans¬mitted to the rest of the world. Our view is that governments and central banks are key actors in the creating of economic fluctuations. Then, in section two, we work out the implications of section one for the metal industries focussing on comparative advantage, trade, and capacity decisions. Over the last fifteen years the world economic system has had slow overall economic growth and has had strangely unpleasant recessions. While future business cycle will not repeat the de¬tailed pattern we have seen, there will be similarities. The similarities need to be under¬stood before investment occurs. The slow growth in the world economy since the early 1970s has aggravated the problems from business cycles, created its own problems, and has partially hidden the effects of other events. Major realignments of currencies are likely to take place over a business cycle. The nature of the causes of the cycle will determine the direc¬tion of change in the exchange rates. For example, whether a USA recession will be accompanied by a weaker or a stronger dollar will be determined by the cause of the recession. The realignment of currencies over a business cycle leads to a realignment of comparative advantage in the metal industries. Thus, not only will world metal consumption vary over the business cycle but the impact on various countries' metals industries will differ consi¬derably. Competitiveness often depends more on the value of the dollar than it does on inherent efficiency and wage rates. Capacity decisions are inherently riskier due to the country specific nature of exchange rate risk. A realignment of currencies changes the pattern of trade if and only if the country with the cheaper currency also has idle capacity. The importance of our topic is indicated by Table 1 which shows the impact of cyclical and exchange rate shocks on the USA metal industry. In the cyclical downturn, from the peak of 1979 to the trough of 1982, consumption dropped by a fifth to a third. Metal price moved in the same

Jan 1, 1989

By Ralph B. Peck

Exploration The technology of underground construction and particularly of tunneling, both now and in the future, starts with knowledge of the properties of the medium surrounding the tunnel. Although we are trying to develop machines that can excavate tunnels independently of the properties of the medium, and although we may achieve some success in this direction, we seem always to be brought up short by a paradox: With increasing sophistication of machines and with increasing complexity of construction jobs, our methods are likely to become more sensitive rather than less sensitive to changes in the medium. I suspect that the need for more precise knowledge of subsurface conditions in advance of construction will increase rather than decrease as time goes by. In the recent anniversary issue of Engineering News Record, Probing the Future, Senior Editor Bill Jacobus prophesies highly sophisticated devices to probe the unknowns of the earth's soil and rock materials. He envisions that "drill holes to obtain borings will give way to rock-melting coring devices". He may be right; it is hard to argue the accuracy of predictions of the future. It seems to me more likely, however, that the rock-melting probe will be simply one more in

Jan 1, 1974

By M. M. Nash

Since the late 19th Century, scholars have been concerned about finding proper methods of managing business. The search seems to be taking us full-circle to the time and motion studies of Taylor (Horn, 1987). It wasn't until the late 1970's, however, that systematic investigations were made in the mining industry. One of the first was a study by Sanders, Patterson, and Peay (1976). That project explored the relationship of attitudes and safety. Peay, Atkin, and Goodman (1977, then reviewed the whole area of Organizational Development, including the so-called Rushton experiment.

Jan 1, 1988

By Zhen-xing Diao, Feng Zhao, Ya-dong Xue

"Two important aspects of excavation performance of TBM are advance rate and cutter replacement/ring consumption, which is closed to the cost and construction duration of the project. To achieve this, a database of TBM parameters and the geological-geotechnical conditions during the excavation of Yinhanjiwei was compiled and analyzed. Relationships between different geological and TBM operational parameters were investigated. Results of analyzes show that there are qualitative correlation between Field Penetration Index (FPI) and rock geological parameters. And strong relationships between FPI and operational parameters are suggested. In this study, the cutter replacement and ring consumption were analyzed using statistical method for preliminary estimation in similar conditions. 1. ITRODUCTION Hard rock TBM is widely used in tunneling project nowadays because of its advantages to conventional drilling and blasting, especially in long tunnels. The biggest advantage is its high advance rate. However, rock conditions of tunnels are complicated. So TBM performance becomes a primary topic in tunneling engineering, which includes of rate of penetration, utilization, daily advancement, cutter consumption and so on. Many prediction models have been developed to estimate the TBM performance in the project planning phase. The most widely accepted and used models around the world are semi theoretical CSM model (Rostami and Ozdemir, 1993; Rostami, 1997) and the empirical NTNU model (Blindheim, 1979, Bruland, 1998).With increasing uses of TBMs in different ground conditions, an increasing number of researchers have developed new models in order to predict the performance of TBM more accurately in similar geological conditions.(Gong and Zhao, 2009; Hassanpour et al.,2009, 2010, 2011, 2014; Delisio et al., 2013; Delisio and Zhao, 2014)"

Jan 1, 2016

By William H. Mount

INTRODUCTION Effective mine ventilation is required to maintain a healthy underground environment for humans. Without effective ventilation, the environment can become unhealthy or hazardous as a result of the depletion of oxygen, contamination with toxic gases, or the buildup of an excessive amount of particulate matter (dust). Each contaminant has an upper limit of concentration that should not be exceeded within an 8-hr period. This is known as the threshold limit value (TLV). The TLV represents an acceptable level of exposure that should produce no ill effects. Unfortunately, more than one contaminant may be present at any one time and the effects of the individual contaminants may be additive, i.e., the effects of each contaminant must be considered simultaneously to determine the potential danger to miners. Possibly the greatest threat to mine-air quality is the uncontrolled underground use of the diesel engine. The diesel engine was invented in 1892 by Rudolf Diesel. His intention was to develop a power source that could burn coal dust as a fuel, but he was unsuccessful in that attempt and had to resort to liquid petroleum fuels (Johnson, 1975). In 1898, the diesel engine was intro¬duced into the United States by Adolphus Busch, who anticipated using it as a prime mover in factories and generating plants. At that time, the diesel engine was a very large and very heavy engine, designed for fixed installations. By 1919, lighter engines were being developed, and by 1931, Caterpillar was marketing a diesel-powered, track-type tractor (Henderson, 1975). Since 1931, the diesel engine has evolved into an extremely popular prime mover in medium and heavy-duty applications. Efficiencies now are on the order of 40% and improvements such as turbocharging and aftercooling have produced engines capable of generating power at a ratio of 0.3 kW/kg (1.0 hp per 5.0 lb) of engine weight. Although the diesel engine is relatively efficient as a mobile power plant, it is far from efficient in terms of the energy produced from the energy potential of the fuel. About 60% of the heat value of the fuel leaves the engine as wasted heat, with about 50% of that heat being emitted through the exhaust pipe and the other 50% being emitted through the radiator or cooling fins. Perfect combustion in an engine would produce only water vapor (H_0), carbon dioxide (CO_), and nitro¬gen (N2) as the byproducts. Since the diesel is not a perfect engine, each pound of fuel burned generates 5.6 m° (200 cu ft) of exhaust gas, containing about 0.009 m3 (0.33 cu ft) of carbon monoxide (CO), 0.009 m' (0.33 cu ft) of nitrogen oxides (NO, NO2, and NOD), and 0.57 m3 (20 cu ft) of carbon dioxide. The balance of the exhaust emission consists of free nitrogen and water vapor (Hurn, 1975). Contrary to popular belief, the diesel is not inherently dirty. Under normal operating conditions, a well-maintained engine neither smokes nor smells. However, the same well-maintained engine can and does produce toxic emissions. A diesel engine is not inherently safe and constitutes a distinct hazard to personnel. This chapter is devoted to a description of the various toxic substances that may be generated by a diesel engine. Although some of these substances may also be produced by blasting or natural causes, the focus of this chapter is on the relationship between the internal- combustion compression-ignition engine (the diesel) and the quality of the mine air. CARBON MONOXIDE Combustion Process During the combustion process (burning) of organic fuels, each atom of carbon combines with two atoms of oxygen, provided that a surplus of oxygen atoms is available. Thus, the carbon is oxidized to carbon dioxide. Most open flames, such as trash fires, camp fires, gas ranges, etc., produce carbon dioxide. However, with insufficient oxygen, incomplete combustion results as the carbon atoms each combine with one atom of oxygen to produce toxic carbon monoxide. Burning charcoal briquettes produce carbon monoxide because the combustion takes place inside the briquettes where sufficient oxygen is not available to the combustion process. Internal-combustion engines, whether burning gasoline or diesel fuel, also produce carbon monoxide. The only oxygen available to the combustion process is that trapped within the cylinder. If the amount of fuel delivered to the cylinder is excessive, there is insufficient oxygen for complete combustion and carbon monoxide production results. In a normally aspirated (nonturbocharged) diesel engine, the amount of air "sucked" into a cylinder is the same on every intake stroke, resulting in complete combustion only at low levels of engine loading, when small amounts of fuel are injected. Higher levels of engine loading cause larger amounts of fuel to be injected into the same volume of air in the cylinder. Unless the volume of air is increased, the combustion process becomes progressively less complete as the amount of fuel increases. Turbocharged engines are able to compensate some¬what for increased loading and increased fuel consumption. The turbocharger acts as a compressor for the intake air, forcing a larger volume of air into the cylinders as the engine speed increases. Hence the turbocharged engine burns cleaner than a naturally aspirated engine and produces slightly less carbon monoxide (Marshall and Fleming, 1971). Much of the underground equipment used today is powered by turbocharged indirect-injection diesel engines. Although these engines emit fewer toxic contaminants than naturally aspirated engines, they do not eliminate the problem. Since the turbocharger is driven by the exhaust gases, rapid accelerations can cause temporary overfueling of the engine until the turbocharger attains a speed sufficient to restore the correct air-to-fuel ratio. During this "turbocharger lag," the combustion cylinders contain insufficient oxygen, causing severe smoking and an increased output of carbon monoxide.

Jan 1, 1982

By Duk-Wom Park

INTRODUCTION he most important information required for the engineering design of structures in rock is its inherent rock properties. Without providing adequate parameters on the rock property, high quality of the engineering design cannot be expected. Many laboratory rock testing methods have been developed, but they are mostly for testing intact homogeneous rock without appreciable discontinuities. In reality, the intact rock properties do not represent the behavior of rock masses because rock masses include irregularities such as joints, cracks, interlayers, variations in mineral compositjon, etc. In general the type and intensity of the rock defects may be much more important than the type of rock which will be encountered (Terzaghi, 1977; Bieniawski, 1984). In-situ rock testing can provide better information on rock parameters, but it takes a tremendous amount of effort, time and cost. In recent years, numerical modeling techniques are gaining popularity as a design tool for structures in rock bodies due to the enormous progress in computer technology (Wang, 1985; Kripakov and Melvin, 1983; Park and Ash, 1985), but it is quite dangerous to use numerical techniques without having proper input data. Bieniawski (1984) states as follows: Some design methods such as numerical techniques have outpaced our ability to provide the input data necessary for the application of these methods. In order to provide an adequate amount of input data, an extensive testing program may be required, thus major efforts in time and expenses are commonly spent, In this paper, a new rock testing method, which utilizes the principles of laser holographic interferometry, is introduced. This method requires only a few minutes to measure the modulus of elasticity and quality of a rock core sample, which does not have to be cut or ground. The Poisson's ratio can also be measured in a few minutes from a sliced rock specimen. HOLOGRAPHIC INTERFEROMETRY Principles of Holographic Interferometry In 1948, Gabor invented holography, which is the technique of reviving three dimensional images using a monochromatic light source. A full demonstration was not made then because a clean monochromatic light source was not available. Later, in the early 19601s, the laser was adopted as a monochromatic and coherent light source (Leith and Upatnieks, 1963). Since then, applications have been made in many different fields ranging from crime prevention to three dimensional television. In this technique, an image is usually recorded by means of constructing a hologram which is a record of the interference pattern formed on a high resolution photographic system as shown in Figure I. A beam splitter divides the laser beam into two beams: (1) an object beam which is expanded while passing through a beam expander and illuminates the object, and (2) a reference beam which is expanded and illuminates the holographic plate. Subsequent to an exposure, the holographic plate is developed and illuminated by the expanded reference beam. The original scene of the object is revived in a three-dimensional image. The entire instrument should be placed on a vibration free environment. The wave fields reflected by the object in two slightly different configurations can be superimposed to form an interference fringe pattern. Thus, it is possible to measure the displacement that took place between the two configurations. This method is called holographic interferometrv. There are two methods of achieving this phenomena. The first is the double exposure method, wherein two exposures of the object are made prior to developing the film. The first exposure represents the original condition and the second, the disturbed condition. The second method is the real time holographic method. In

Jan 1, 1986

By James A. Finch

The Gaudin lecture is devoted to fundamentals. Given my involvement with column flotation over the last 20 years, this is my topic. I have tried to identify spinoff basic research and provide a personal list of favorites. Two are selected for discussion here. They are single bubble rise and bubble surface area flux. The rationale for such work, as well as some of the findings, are reviewed. Support for fundamental work seems as volatile as the economy (and the link is probably not coincidental). I hope some utility to the minerals industry is evident in the text. Column flotation in its current form originated in the early 1960s. The method was invented by Boutin, patented by Boutin and Tremblay and pursued doggedly by Wheeler. Their aim was to overcome the problem of mechanical entrainment of fine particles in the water carried by the bubbles, which they were convinced contributed to lowering flotation concentrate grades (Wheeler, 1988; Finch and Dobby, 1990). The solution was a combination of columnar geometry, the addition of wash water into a deep froth and the maintenance of an excess of water to the tailings, as compared to the feed (a so-called positive bias). Success at Les Mines Gaspe, Quebec, on cleaning Mo in the early 1980s signaled the start of industrial acceptance, making the column one of the flotation machines of choice today. Over the next 20 years, column applications mushroomed to cover virtually all mineral commodities, as well as nonmineral applications such as soil decontamination, deoiling of water and deinking of recycled paper. In the wake, research groups are continuing to probe the fundamentals, conferences and workshops have been transferring the technology and specialist companies have emerged to service the demand. Innovations were triggered as problems arose (for instance, in gas injection systems) and novel flotation cells, much in vogue in the 1990s, had the door opened. Mechanical cell manufacturers have not been idle - there is nothing like competition to provoke a fresh look at an established business. Flotation-cell technology has probably not seen so much activity since the patent rush in the early days of flotation, which occurred around the turn of the century. For an industry often considered reluctant to risk innovation, this is not a bad record. A good idea will find a place, but patience (not always an innovators strong suit) and careful preparation are required. Two books (Finch and Dobby, 1990; Rubenstein, 1996), three symposia (Sastry, 1988; Agar and Huls, 1991; Gomez and Finch, 1996), and a series of reviews (Dobby and Finch, 1991; Finch and Dobby, 1991; Finch, 1995; Finch et al., 1995) document the period. Like many good ideas, column flotation has been overexposed, and there have been disappointments. In a recent example, columns performing scavenging duty were replaced by mechanical cells (Chong et al., 1998). The further applications stray from the original - to

Jan 1, 1999

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 P. F. Ziemkiewicz, A. S. Knox

Large-scale use of CCBs in mine environments involves filling surface and underground coal mines with ash to address hydraulic problems, AMD, backfilling and subsidence. The environmental risk of land filling CCBs is generally evaluated by the Toxic Characteristics Leaching Procedure (TCLP) or the Synthetic Precipitation Leaching Procedure (SPLP). However, there is doubt regarding the applicability of these tests to long-term CCBs leaching behavior in groundwater associated with coal mines. The Mine Water Leaching Procedure (MWLP) was developed to provide a site specific risk assessment tool. The MWL Pprocedure is presented in this paper and compared with TCLP as a study.

Jan 1, 2003

By Charles A. Beasley, Vince Joyce, David E. Beasley, Orlando A. Gallegos, David A. Shuman, Mehmet H. Erten

COAL CHARACARISTICS AND PREPREPARATION REQUIREMENTS Preparation and Market Specifications The national ambient air quality standards (NAAQS) established by the Environmental Protection Agency in 1977 require that when coal is burned, the environmental degradation should be a minimum. For this reason, even coal containing low ash and sulfur must be used in compliance with the NAAQS. The most important pollutants resulting from the combustion of coal are ash, SO2, and NOx gases, and the particulate matter escaping with the combustion gases. The ash is the residue left after complete combustion of coal. It results from the inorganic mineral matter existing in the coal before it is burned. The SO2 results from the combustion of inorganic and organic sulfur associated with the coal. The inorganic sulfur may occur as pyrite, marcasite, or as sulfate sulfur of mostly iron and calcium. The authorities disagree in the definition of organic sulfur in the coal. However, according to ASTM Standard D2492-77,1 the organic sulfur is that sulfur occurring in the coal after subtracting the sum of pyrite and sulfatic sulfurs from the total sulfur in the coal. The NOx gases are produced from high temperature oxidation of nitrogen in the coal that is released into the atmosphere. The particulate matter may consist of fly ash and unburned coal. Selective Mining The cleaning of coal from included ash and sulfur-bearing materials should start at the working faces of surface or underground mines. This can be done by (1) mining only those seams which meet certain quality standards, (2) not mining sections of the seams which may cause deterioration in overall quality of the mined coal, and (3) using a mining method that allows selective mining of coal areas or horizons either underground or on the surface. Since these steps improve the coal quality before the coal reaches the preparation plant, they can be considered to constitute precleaning of coal. During the exploration and development stage of a mine, core and channel samples taken from the coal seam are used to determine (1) petrographic analysis and physical properties,2 (2) character of roof and floor of the seam, 3,4 (3) character and quality of impurities,5 (4) proximate and ultimate analysis, and (5) washability characteristics. However, all of these parameters are subject to considerable variation even within the same seam during the advance of the coal face. This creates a problem in meeting the market demand for coal quality if the coal is to be shipped directly from the mine. If the mining operation is large enough, special blending silos or mechanical blending systems may have to be used to provide uniform quality to the market. However, even if the coal is shipped from a coal preparation plant, prepreparation

Jan 1, 1991

By J. C. Harrison

When Exploraciones Eldorado, S.A. de C.V. finished their first phase of reverse circulation drilling at their La Trinidad property in Sinaloa, Mexico they began immediately with permitting and engineering activities. The first phase of drilling lasted four months and ended in April, 1994. The second phase of drilling ran from May through September of 1994. From May through December, 1994, Exploraciones Eldorado performed the permitting and engineering work for their La Trinidad heap leach mine. The mining permit was submitted to the regulatory agencies in February of 1995 and the first draft of the feasibility study finished one month later. The report outlines the permitting and engineering activities that took place during the second half of 1994.

Jan 1, 1996

By W. H. Andrews

DEFINITION OF BAUXITE The term "bauxite" (1) dates back to 1821, when it was assigned to a deposit of red earthy material outcropping near the village of Les Baux in Southern France. Chemical analysis indicated the presence of aluminium oxide, iron oxide and water. Deposits of bauxite are widespread throughout the world although the major developments occur within 30 degrees of the Equator. Essentially bauxite is the product of weathering and leaching of a variety of sediments or rocks, generally in a high-rainfall tropical or sub-tropical climate, resulting in the enrichment of the aluminium oxide content. It is characterised by the presence of one or more of the minerals, gibbsite, boehmite, and diaspore. The other constituents are usually clay, (typically kaolin), hematite and/or goethite (iron-oxides), anatase (titanium oxide), and possibly silica as quartz. A variety of minor elements may be present, such as calcium, magnesium, phosphorus, vanadium, gallium, manganese, and many others in very small quantities. Organic compounds are normally present from development in association with a soil horizon where vegetation may be encouraged by the high rainfall necessary for bauxitisition. The physical form depends upon the geological history of the deposit and correlation also exists with the mineralogy. Older deposits which have been subject to burial are invariably hard and compact with the alumina predominantly occurring as boehmite or diaspore, while the more recent, surface deposits are frequently less compacted and gibbsite is the dominant alumina mineral. In these later deposits, the physical form can vary from the fine red soil (terra rosa) of Jamaica to the Weipa pisolites to the cemented Arkansas type. The presence of concretionary structures is an important aid in identification in the field.

Jan 1, 1984

By John F. Parmeter

On August 29, 1989, the Department of Labor, Mine Safety and Health Administration (MSHA), published a Federal Register concerning a new proposed rule on air quality, chemical substances and respiratory protection standards. As of this writing, their proposed rule has not become a standard. However, with little revision it could be expected to become a standard, and we in the mining industry will be expected to adhere to and enforce it.

Jan 1, 1991

By Panlop Huttagosol

The use of computer models to design ultimate pit limit of an open pit mine during its feasibility study has become an emphasized procedure in mining. It is a normal practice in open pit mine design to generate the most profitable final pit limit. The limitations of designing this optimal pit limit have been the requirement of significant computing efforts as well as the use of complicated operations research techniques. In an attempt to describe a computer method that has an easy conceptualization and is able to provide a precise and desirable solution, a new technique is developed. The ultimate pit limit problem is formulated as a large scale transportation problem. The formulation is based on the use of a three dimensional block model to represent an ore body and surrounding materials. The solution technique is developed through solving the dual system of the formulated problem by using the adapted simplex algorithm of linear programming. The implementation on given case studies demonstrates that the new method is capable of providing an optimum pit value. The computing effort required by the algorithm is still the main constraint in solving a large scale problem. The technique provides open pit mine planners with an alternative tool in using a commercial linear programming software which is capable of solving a general transportation problem. The selected software must be able to handle a large scale problem, and it needs an additional effort td formulate the problem and transform a result into the ultimate pit limit solution.

Jan 1, 1992

By Benno Ring

"When designing segmental lining at a cross passage, modern solutions try to bear the loads transferred around the opening within the rings by using shear elements in the ring joints. Commonly used shear systems providing coupling are cam & pocket, shear keys, bicones and steel dowels. These solutions have advantages and disadvantages, but most importantly they have limits in their capacity to stabilize the lining at cross passages. With the help of 3D-FE-analyses for an opening of one segmental ring these different solutions are compared taking various ground conditions into account. As a result the capacity of the individual system is determined. Notice is made regarding the applicability of the system as well as the consequences for the design and the verification. INTRODUCTION The design of the lining at a cross passage is among the most difficult tasks when designing TBM-tunnels. At one time the bedding of the lining disappears due to the excavation behind the lining, at another the ring-structure is interrupted when parts of the lining are removed for the opening. The trick is to transfer the loads around the opening into other segments and to areas of the lining which are still supported by the ground. In the rings immediately at the cross passage this creates a distribution of forces within the segments that strongly deviates from that of the regular lining. The design needs to consider the boundary conditions of the respectively chosen solution for stiffening of the opening and its peculiarities in the modeling as well as in the verifications. In the past segments of steel or an internal strutting of steel (DAUB 2013) placed around the later openings were commonly used, see Figure 1. The application of a strutting from the outside to the rings is restricted to such circumstances when for example a connection from a shaft to the tunnel can be made in suitable ground conditions (Ring and Glomp 2012). Though steel segments provide a robust solution, they are expensive due to their laborious manufacture, the high proportion of construction steel required and the time consuming installation in the tunnel (Häfliger 2013). A strutting of steel requires extensive design and verification. The resulting structure usually weighs several tons and must be erected as well as demounted within the confined space of the tunnel, requiring suitable transport and assembly equipment. The cross section remains restricted, thus causing a bottleneck for TBM operations and hindering the works and installations for the cross passage works."

Jan 1, 2016

By A. W. Khair, S. S. Peng

Discussion by J. Parker Gentlemen; Rainy day in Upper Michigan, a good time to catch up on reading. Am doing that, and have a couple of questions concerning the K and P paper on roof problems and supports. I wonder if the authors can enlighten me. The compressive strength of the coal was reported as 4.4 MPa (633 psi) and compressive stresses measured in the coal seam were reported at around 27.6 and 48.2 MPa(4000 and 7000psi ). Can such a soft coal actually contain such a high level of stress? Can it be measured as if the material were elastic, or does the coal behave plastically? Can that stress level be confirmed with hydraulic load cells? And if the coal is so soft, and if it is plastic, why is the stress field not hydrostatic'? The intact roofrock appears to be unusually strong, with compressive strength reported at around 145 MPa (21,000 psi), and some failures were noted as soon as the rock was exposed. Were tests run to find out how that rock responded to the addition of moisture, from sprays or from humid air? Did moisture weaken the rock? Did it cause the rock to expand quickly, thus to induce internal compressive stress? How can the near-vertical cutters, as shown in the photographs, be attributed to primarily horizontal stresses? Did the cutters follow any particular pattern in the development panels, which might be related to a particular stress pattern? For example, did they always appear alongside the stiffest pillar? Or always along the northwest rib? Was there any evidence of the pillars and entries "rotating" under the influence of differential horizontal stresses? How much did the entries and pillars rotate as the longwall face approached and passed? After rooffalls, did the openings assume shapes which would indicate a preferred shape in that stressfield and geology? Did crosscuts always survive without damage, as shown in the sketch?

Jan 1, 1992

By Marian Radetzki

The economic developments and industrial behavior patterns that led to a lasting excess capacity in the world non-ferrous metals industries from the aid-1970s are explored. Detailed attention is devoted to analyzing and defining crucial concepts like "capacity", "excess capacity", "capacity maintenance" and "investments". Empirical evidence of capacity utilization and capacity growth in the industries under study is provided. The coincidence of excess capacity and low prices on the one hand, and investments in capacity maintenance and capacity expansion, on the other, is seen as a consequence of substantial declines in the metal industries' investment and production costs during the period studied.

Jan 1, 1989