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By R. G. Eggert, M. R. Walls

A mining CEO's willingness to participate in risky investment opportunities significantly affects a company's strategic-investment decisions. Decision-analysis techniques provide a mechanism for measuring a CEO's risk tolerance and ability to make formal comparisons of risk propensity among mining firms. The authors developed a methodology for measuring CEO risk tolerance. The findings from a confidential survey of mining CEOs are presented. The results from the survey suggest that: •mining CEOs are overwhelmingly risk averse when considering investment decisions; •CEOs of small mining firms are significantly more risk averse than CEOs of large mining firms; and •there appears to be some differences between Australian and non-Australian CEOs regarding their willingness to participate in risky investments. The results of this survey suggest that CEOs are pursuing objectives other than, or in addition to, maximizing shareholder wealth and that they act to reduce the financial exposure associated with strategic investments.

Jan 1, 1997

By T. N. Moore, E. M. De Souza

Because jackleg rock drills are a potential source of hand vibration exposure, they can effectively produce Hand Arm Vibration (HAV) Syndrome in their operators. This will affect operator efficiency and mine productivity. As a result, a significant amount of work has focused on redesigning rock drill handles using new materials to minimize hand-transmitted vibration. In previous work developed by the authors (1991), a detailed study was undertaken to determine the effectiveness of using elastomer covered handles in place of the standard steel design. The results indicated that, for an elastomer-based handle design, the overall acceleration level experienced by the hand can be reduced by as much as a factor of three, relative to the steel handle. It was also shown that this reduction takes place predominantly in the frequency range above 500 Hz. This paper presents an investigation of the long-term effectiveness of an elastomer-cushioned handle under different conditions underground. In this study, sponsored by the Mining Industry Research Organization of Canada (MIROC), a number of cushioned handles were quantitatively and qualitatively tested in five operating mines. The vibration testing program has indicated that the cushioned handle can reduce overall vibration levels by as much as a factor of three. The qualitative assessment program of the cushioned handles by the drill operators has indicated some degree of preference for the cushioned handles over the steel handles, if certain design modifications are performed. This research program indicated that cushioned handles have the potential to become the dominant method with regard to vibration reduction and operator performance.

Jan 1, 1994

By Kal V. S. Sastry

Mineral processing simulation has come a long way since its beginning about thirty years ago. With our increased understanding of mineral process systems and the advent of new software and hardware technologies, we can visualize an ideal mineral processing simulator. This paper attempts to identify a number of desirable features of an ideal mineral process simulator and to describe the exciting trends in making such an ideal simulator a reality.

Jan 1, 1992

By F. Vincent, A. Boulet, M. Noaparast, F. Woodcock, A. R. Laplante

A novel methodology to estimate gold recovery by gravity is presented. It makes use of a population balance model which represents gold liberation, breakage and classification behaviour and applies pre-concentration and recovery data to gravity recoverable gold (GRG) to predict overall recovery. The methodology is designed for gravity circuits located in the circulating load of secondary grinding mills. Gold liberation is estimated by processing a sample of representative ore with a laboratory Knelson Concentrator (LKC) in three successive steps, each at a finer grind than the previous one. Breakage behaviour is represented by a matrix H, which redistributes GRG in the feed of the secondary mill in the various size classes of its discharge. Provision is also made to account for gold overgrinding, which decreases the overall amount of GRG. Classification, pre-concentration and recovery data are estimated from plant performance, and are represented by the diagonal matrices C, P and R. The methodology is demonstrated with case studies of greenfield, retrofit and optimization applications.

Jan 1, 1995

By L. M. Turner

Perlite is a unique mineral that upon heating expands to about twenty times its original volume. Mining is by open pit method. The processing cycle involves crushing, screening and sizing the ore. An on-site quality control facility at the Manville Products No Agua mine exerts a high degree of control over every phase of the operation from blasting to finished product.

Jan 1, 1985

By D. C. Ridenour

The pressure system of ventilation with large diameter bore holes has been very effective in the ventilation of two gaseous mines, the Olga No. 1 and No. 2 Mines in McDowell County, West Virginia. The No. 4 Pocahontas Coal Seam on the Olga property lies 580 feet below the valleys. The seam is very gaseous as well as dry and dusty, which makes good ventilation all the more essential. Irregular and often extensive areas of the coal seam have been replaced with impervious shales and sandstones in "Fault" or "Want" areas. The replacement materials have sealed the methane in the coal seam and thus increased the quantity of gas that must be handled as mining is done. Often the No. 5 Pocahontas Seam comes down to meet the No. 4 Seam at the Faults and considerable methane is sometimes released from the upper seam. The factors mentioned, together with the irregular and unpredictable lateral shape' of the faults, result in long narrow stringers of coal that are very gaseous and difficult to mine. So far as the Olga Coal Company is concerned, the most effective ventilation under the conditions outlined has been the use of large diameter bore holes with a pressure ventilation system. The ventilation of a mine can be accomplished in two fundamental ways. The mine atmosphere maybe reduced below atmospheric pressure by an exhaust fan; or it may be raised above atmospheric pressure by a pressure fan. In either case, the coursing of the air is so planned as to have the haulage and traveling ways on intake air. While the majority of the coal mines in the United States, no doubt, use the exhaust system of ventilation, there are several advantages of the pressure system which are extremely beneficial.

Jan 1, 1960

By E. Bane Kroeger

Plane failure in rock and soil slopes is usually caused by the intersection of a discontinuity plane with a slope face. Normally, these discontinuities are weaker than the surrounding intact rock and provide a surface along which movement can occur. The discontinuities are typically analyzed to determine the stability of a particular slope. One problem that arises when evaluating the stability of a planar feature is that the method for planar analysis is two-dimensional and has difficulty dealing with planes that are oblique to the slope face. Several researchers have stated in the past that planar failures are a special case of wedge failure. Wedge failures occur when two planar discontinuities intersect in an unfavorable manner. Sliding can occur along the intersection of the planes. Wedge failures are very common in rock slopes and can often be problematic. Wedge stability analysis methods are typically three-dimensional and can analyze planar features that are very oblique to the slope face. Wedge failure analysis can also be used to determine the stability of planar features with good success. One advantage to using wedge analysis over plane analysis is that a tension crack can be both non-vertical and oblique to the slope face in the wedge analysis. This allows the engineer to more closely match field conditions. It also negates the need for the engineer to have two separate software packages to analyze a single slope, saving both time and money.

Jan 1, 2002

By Stanislaw Wasilewski, Zdzislaw Krzystanek

Ventilation process in deep mines features relatively low efficiency. Commonly used passive control by means of regulators and flow throttling leads to remarkable energy losses that could be lower if effective monitoring and remote control of main fan operating point were implemented. In the paper, some results of investigation carried out in Polish coal mines to evaluate real energy losses in ventilation process are described. Different methods for main fans performance monitoring and control are considered and compared especially those using fan drive speed control to minimize power consumption. On the other hand some criteria for power evaluation are analysed and algorithms for optimum location of controllers in ventilation network are considered. The results of investigation are being implemented in the first system for monitoring and control of main fan operating point in Miechowice colliery.

Jan 1, 1995

By F. M. Doyle

Metal removal kinetics and metal ion selectivity in ion flotation were studied from a thermodynamic perspective. Surface tension data could be used with the Gibbs adsorption equation to quantitatively predict the metal-ion removal kinetics in alkylsulfate-Cu systems. However, surface tensions predicted cation selectivity coefficients in the sodium dodecylsulfate (SDS)-Cu-Ca and SDS-Cu-Pb systems rather poorly, although the predicted order of the selectivity (Cu2+ < Ca2+ < Pb2+) was correct. Another thermodynamic selectivity model, which used the Grahame adsorption equation and a geometrical analysis, predicted cation selectivity coefficients that agreed very well with experimentally measured values.

Jan 1, 2002

By Fathi Habashi

THE CHOICE of a precipitant for a certain metal ion depends, beside the economic factor. on the following factors: 1) The precipitant should be specific as far as possible so that pure precipitates can be obtained

Jan 1, 1970

By Palmer C. Sweet

By-products from mining and processing plants and coal-fired power plants are being utilized more as valuable resources in Virginia. Mining-related by- products are divided into two categories: those generated from mineral extraction and beneficiation, and those generated from mineral processing or from industrial plants. Materials from both categories are produced in Virginia, where by-products have been exploited for various uses in the past and/or present. These materials include coal- combustion products (fly ash and bottom ash), lime-kiln dust, flue-gas-desulfurization residue, rock fines, magnetite, Cold Spring clay (kaolin), Austinville tailings, soapstone rock, and calcium-carbonate paste. Some of these by-products have never been utilized, although several ideas have been investigated over the years.

Jan 1, 1999

By Nick J. Miles, Gareth J. Brown

The degree of fragmentation of dispersed systems of brittle materials such as pulverised rock has been described by a fractal dimension i.e. the fragmentation fractal. This fractal dimension represents a power law size-frequency distribution, where, in this case, the size is defined as the square root of the projected area. The existence of a fractal dimension for the number-size distribution, of the progeny of failure event, is direct evidence for scale invariance of the fragmentation process. Since a fractal dimension infers that failure mechanisms operate on all scales it has been suggested that the fractal dimension is a measure of the fracture resistance properties of materials during fragmentation. In order to investigate this a range of rocks of varying fracture toughness were broken under similar levels of impact velocity in the dynamic tensile failure of single particles. The fragmentation fractals determined from the resultant particle populations, of the breakage experiments, were monitored and are discussed.

Jan 1, 1995

By James Wm. White

Mine management now recognizes the value of computer-based truck-shovel dispatching in open pit mines. The key tangible benefits are substantial productivity increases with a given fleet of equipment or, alternately, significant reductions in equipment required to meet production quotas. In this work, we review the literature, report on efficient, optimal algorithms for haul truck dispatching in real-time, and briefly discuss methods used by various mines to evaluate productivity improvements over manual methods. We also present actual results obtained at thirteen mining operations around the world.

Jan 1, 1992

By Thomas G. Johnston, Garston H. Blackwell

The development of a block model for a copper molybdenum ore deposit is described. The early use of the inverse distance power estimator, and later transition to geostatistics and kr iging, produced block models suitable for global reserve estimates. Because the global reserve was inadequate for routine mine planning, the production blast hole assays were incorporated into the block model, resulting in excellent local grade prediction. The on site use of small mini, and more powerful personal computers for estimating grades is described. The development of a computer aided, interactive graphic, mine planning system utilizing the grade block model is detailed.

Jan 1, 1987

By P. R. Khangaonkar, G. Bhaskar Raju

Three types of flotation columns were developed with a column dia of 8.0 cm and a length of 160 cm. The first type consists of an ordinary column fitted with a porous plate at the bottom. The second type consists of two electrodes at the bottom to obtain very fine and uniform bubbles generated electrolytically and the third is a combination of first and second types, i.e. to get both electrolytic bubbles and air from the compressor through porous plate. Three different ores were tested-gold tailings for recovery of scheelite, copper tailings (chalcopyrite) and oxide copper ore. In the case of scheelite and copper oxides, good results were obtained with the first type of column itself, whereas the third type column was found fairly effective in the recovery of chalcopyrite. The variables like the effect of reagent concentration, column height above the feed point, feed flow rate, current density, air flow rate, particle size etc. were examined.

Jan 1, 1988

By A. B. Seal, C. J. Bise

Excessive noise has long been a hazard in the coal-mining industry. Studies conducted during the mid-1970s and mid-1990s consistently show that hearing loss within the mining industry persists, in spite of regulatory requirements and sampling technology advances. When the U.S. Mine Safety and Health Administration&apos;s new health standards to protect miners from hearing loss took effect in September 2000, the potential developed to reevaluate sampling approaches with regard to noise-source hazards, such as task-based methods. This paper describes results from a Pennsylvania State University research project now being conducted at an underground coal mine. Each occupation was reviewed, and a list of tasks or processes performed by each was generated. Traditional personal noise dosimetry, static sound pressure levels and equipment sound mappings have been performed. Job tasks indicating the greatest levels of daily noise exposure and contributions to noise dose have been identified and will be discussed.

Jan 1, 2003

By Maurice C. Fuerstenau, Bruce R. Palmer, R. E. Johnson, B. R. Palmer, G. W. Warren

The environmentally sound processing of metal-bearing chloride solutions plays a key role in the extraction, plating, recycling, finishing and surface preparation of metals. Additionally, many chloride-bearing waste streams must be processed to obtain environmentally acceptable products. This paper reviews the technologies used for processing aqueous metal-chloride solutions and describes the challenges that have been overcome in application of these technologies.

Jan 1, 1993

By Jonathon M. Hanson, John F. Schatz

A combined theoretical and laboratory test program is described with the purpose of providing a useful model of the multiple radial fracturing process. A non-quantitative conceptual model is developed as the basis for detailed mathematical modeling and test planning. The model includes borehole pressurization, flaw rupture, and gas- driven fracture propagation phases. The laboratory tests are carried out in blocks of scaled rock simulant loaded to a true three-dimension stress state and with miniature propellant/explosive charges in a wellbore as the fracturing energy source. The conceptual model, fracture initiation modeling, and laboratory test setup have been completed and are described. The remaining work is ongoing

Jan 1, 1986

By James W. Griffith, Sarah A. Riling

Bituminous coal dust was repeatedly placed into one lung lobe of anesthetized Macaca nemestrina monkeys using a flexible fiberoptic bronchoscope. Radiographs taken at 15 day intervals showed a focal radiographic density after 90 days time when a total of 1 gram of dust had been instilled. The radiographic density progressed slightly in size until 12 months by which time 3 grams of dust had been instilled and the animals were euthanized. At necropsy, the only significant gross lesion detected was the focal black pulmonary lesion located at the dust instillation site. Histologically, the lesion was composed of coal dust laden macrophages located primarily within interstitial tissue and interspersed with a slight amount of reticulum and connective tissue fibers. The distribution of coal dust was limited to the instillation site in the right caudal lung lobe based on radiographic, gross and histologic examination. Bronchoalveolar lavage of both right and left caudal lung lobes was performed 8 times during the 12 month long experiments without significant complications. More macrophages were found in lavage fluid from the right lung than the left, and most macrophages from right lung contained coal dust particles. Based upon a limited physical examination and complete blood count at 15 day intervals the animals remained normal during the experiment. We conclude that the primate lung&apos;s response to focal experimental bituminous coal dust resulted in a marked focal increase in pulmonary alveolar macrophages, which can be recovered regularly in high numbers by bronchoalveolar lavage. The model described has significant potential for investigating the pathogenesis of various respirable dust-induced pneumoconioses, for evaluation of new therapeutic approaches, and for refining experimental and clinical diagnostic applications of bronchoalveolar lavage. Key words: Coal Workers Pneumoconiosis, Disease model; Primate, Lung Lavage Fluids

Jan 1, 1991

By Peri Mehling, Allister Brown

Environmental regulations concerning the processing of gold ores and the treatment and disposal of spent process solutions range from rigid standards in some locations to site specific options in several other jurisdictions. This paper examines the regulations and policies in two North American jurisdictions. Emphasis will be placed on the mill process and waste stream treatment and disposal, and implications for environmental impacts. Case examples of mine licence requirements will be discussed, with brief descriptions of individual treatment and disposal systems. Policies and environ- mental regulations within each jurisdiction will be examined in terms of potential environmental protection.

Jan 1, 1987