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By R. T. Richins

Coeur d'Alene Mines Corporation (CDE) is a precious metals mining company. The company's three mining operations are located In Nevada and Idaho. Collectively, these mines (Rochester in Nevada, and the Galena and Coeur In Idaho) produced about 61,000 ounces of gold and more than 7.5 million ounces of silver in 1991. The company is currently planning the development of two major properties; the Fachinal gold-silver project in Chile and the Kensington gold project near Juneau, Alaska. Fachinal and Kensington hold encouraging potential to significantly expand CDE's gold production during this decade. The permitting process for these two distinctly contrasting environmental settings, project design requirements and regulatory/political circumstances provide the basis for a comparative analysis of licensing and permitting requirements, timeliness of the permitting process and costs in the U.S. and Chile.

Jan 1, 1993

By Fred Horne

1N THIS PAPER, the writer proposes to limit his comments to few generalized phases of the subject, based on his personal experience in the midwestern United 'States and in one section .of the Coal Branch in Western Alberta. The following statistics are submitted to show the importance that strip mining has assumed in the coal mining industry of the United States. In 1914, 1,281,000 tons of strip coal were produced, amounting to 0.3 per cent of the total production. In 1948, the total was 13~,505,000 tons, representing 23.3 per cent. In 1949, the percentage figure dropped slightly and this can be partially accounted for by the labour disturbances prevalent throughout the year. In 1914, there were 48 power shovels and draglines being used in the stripping of coal; in 1949 there were 3,712, not to mention other types of coal stripping equipment such as bulldozers, tractors and scrapers, rotary excavators, and stackers. At the bituminous coal mines in Western Canada, strip mining was introduced only a few years ago, two of the major reasons for its development being the need for increased production during the war and post-war years and the need to hold the line on increasing production costs, but even in these few years the percentage of strip production has in-creased to such an extent that some mines that, five or six years ago, were producing all their tonnage from underground operations are today obtaining up to 80 per cent of their total output from strip mines.

Jan 1, 1951

By Sean Gallagher, William S. Marras, Alan S. Litsky, Velimir Matkovic, Deborah Burr, John Landoll

Study Design. Survival analysis techniques were used to compare the fatigue failure responses of elderly motion segments to a middle-aged sample. Objectives. To compare fatigue life of a middle-aged sample of lumbosacral motion segments to a previously tested elderly cohort. An additional objective was to evaluate the influence of bone mineral content on cycles to failure. Summary of Background Data. A previous investiga¬tion evaluated fatigue failure responses of 36 elderly lumbosacral motion segments (average age, 81 ± 8 years) subjected to spinal loads estimated when lifting a 9-kg load in 3 torso flexion angles (0°, 22.5°, and 45°). Results demonstrated rapid fatigue failure with increased torso flexion; however, a key limitation of this study was the old age of the specimens. Methods. Each lumbosacral spine was dissected into 3 motion segments (L1-L2, L3-L4, and L5-S1). Motion segments within each spine were randomly assigned to a spinal loading condition corresponding to lifting 9 kg in 3 torso flexion angles (0°, 22.5°, or 45°). Motion segments were statically loaded and allowed to creep for 15 minutes, then cyclically loaded at 0.33 Hz. Fatigue life was taken as the number of cycles to failure (10 mm displacement after creep loading). Results. Compared with the older sample of spines, the middle-aged sample exhibited increased fatigue life (cycles to failure) in all the torso flexion conditions. Increased fatigue life of the middle-aged specimens was associated with the increased bone mineral content (BMC) in younger motion segments (mean ± SD, 30.7 11.1 g per motion segment vs. 27.8 ± 9.4 g). Increasing bone mineral content had a protective influence with each additional gram increasing survival times by approximately 12%. Conclusion. Younger motion segments survive considerably longer when exposed to similar spine loading conditions that simulate repetitive lifting in neutral and flexed torso postures, primarily associated with the increased bone mineral content possessed by younger motion segments. Cycles to failure of young specimens at 22.5° flexion were similar to that of older specimens at 0° flexion, and survivorship of young specimens at 45° flexion was similar to the older cohort at 22.5°. Key words: biomechanics, low back disorders, fatigue failure, age, motion segments, vertebral endplate fractures, torso flexion, lifting, bone mass. Low back disorders (LBDs) are a major cause of both short- and long-term occupational disability in the United States, and it is clear that workers in certain occupations are more susceptible to LBD.2-5 Specifically, epidemiologic studies have shown that jobs involving heavy physical demands such as construction,2,3 mining,2,4 and farming,5 engender increased risk of back pain. These occupations are thought to experience high LBD rates as a result of their extreme postural and manual lifting demands. Studies have shown that jobs involving significant lifting 6-9 and jobs that involve frequent bending10-12 are associated with increased LBD risk. Workers in the mining industry, in particular, often have to lift heavy materials in restricted workspaces that compel torso flexion. An understanding of the impact of repeated loading of the spine in flexion on fatigue failure of spinal tissues is thus a critical issue for our research agency, which is concerned with reducing the pain and disability associated with LBD in the mining industry. It is well accepted that loads experienced by the spine during manual lifting tasks are sufficient to cause fractures in the endplates of lumbar vertebrae, particularly on repeated loading. 13-15 Endplate fractures may not be painful in and of themselves 16; however, evidence suggests that the process of internal disc disruption and disc degeneration may be initiated via endplate fractures. 16,17 It has been shown that endplate damage will alter the distribution of stress in the disc, resulting in buckling of the lamellas of the internal anulus.17 Once this process has been initiated, repeated spine loading will cause additional disruption of the anular fibers, resulting in formation of significant fissures or tears. 11-21 If these tears occur near or extend close to the outer portions of the anulus, a wound healing process is initiated, which involves infiltration of mast cells, macrophages, and re¬lease of cytokines and growth factors. 21 The presence of these infiltrates has been strongly linked to discogenic low back pain. 21,22 Indeed, for patients experiencing chronic low back pain, the prevalence of internal disc disruption is at least 39%,19 which represents the most

By J. W. Hohn

The precipitation of Fe(III) to form ferrihydrite in the presence of arsenic is the United States EPA's Best Demonstrated Available Technology for treating arsenic-containing hydrometallurgical solutions and waste streams. This technology has been widely adopted throughout the world and developments have been well reviewed. The adsorption and long-term stability of ferrihydrite can be improved by co-precipitating Fe(III) and Al(III) together to form an aluminum-modified ferrihydrite. Arsenate adsorption into ferrihydrite and modified ferrihydrite as a function of pH, Fe/As or (Al+Fe)/As mole ratio, and the initial As(V) concentration is presented and compared. The results of long-term aging of both adsorbents at 70°C for over a year are also summarized.

Jan 1, 2006

By B Rusk, L Corriveau, P Emsbo, R P. Xavier

"An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation. Porphyry-Cu (Mo-Au) deposits and iron oxide-copper-gold (IOCG) deposits are both characterised by the presence of abundant halite-saturated fluid inclusions that reflect the circulation of hyper-saline hydrothermal brines. While it is widely accepted that brines involved in the formation of porphyry copper deposits derive from unmixing of moderate-salinity, intermediate-density fluids that exsolve from crystallising magmas, the source of brines that form IOCG deposits remains enigmatic and intensely debated. In this extended abstract, we summarise the fluid inclusion characteristics of both deposit types and present trace element compositional data for halite-saturated fluid inclusions from both porphyry copper deposits and IOCG deposits from around the world.While both deposit types typically contain halite-saturated fluid inclusions, vapour-rich fluid inclusions in IOCG deposits are less common than in porphyry deposits and evidence for fluid immiscibility is rare. IOCG deposits also typically lack intermediate-density fluid inclusions that characterise the deeper quartz-rich veins in many porphyry deposits. Many IOCG deposits contain CO2-only fluid inclusions, a type of fluid not observed in porphyry Cu deposits.Our fluid inclusion compositional data show that most porphyry Cu (Mo-Au)-related brines are dominated by Na, K and Fe and contain elevated concentrations of Ca, Cu, Pb, Zn and Mn up to around the one per cent level. On the other hand, IOCG brines are Na-Ca-Fe-dominated and typically contain far less Cu, Mn and Zn than porphyry brines. In addition to Ca, these fluids are also strongly enriched in Ba and Sr relative to porphyry-related brines. Such compositions are consistent with extensive fluid-rock interaction and/or an evolved sea water contribution to IOCG brines.A sea water or basinal brine source for IOCG brines is further supported by bromine concentrations that are much higher than is characteristic for porphyry-related brines. Porphyry brines have Cl/Br molar ratios of between 800 and 3000, which is characteristic of primary magmatic brines, whereas the Cl/Br composition of IOCG brines is more variable. For example, Na/Cl/Br ratios of most IOCG deposits in the world-class Carajás district fall on or near the sea water evaporation curve (most Cl/Br molar ratios are between 200 and 1000) and are diagnostic of sedimentary bittern brines. A few of the deposits in this district also show evidence of the input of subordinate amounts of magmatic brine. At Ernest Henry, in the Cloncurry district of Australia, most Cl/Br ratios plot close to the sea water evaporation curve, but Cl/Br ratios of up to ~5000 in several samples suggest the input of lesser amounts of magmatic fluids, and possibly evaporite-dissolution-derived fluids. Taken together with geologic constraints, these data strongly suggest that porphyry-type deposits form from the circulation of dominantly magmatic fluids, while IOCG deposits form from large-scale circulation of high-salinity fluids sourced dominantly from sedimentary basins with variable input of magmatic volatiles.CITATION:Rusk, B, Emsbo, P, Xavier, R P, Corriveau, L, Oliver, N and Zhang, D, 2015. A comparison of fluid origins and compositions in iron oxide-copper-gold and porphyry-Cu (Mo-Au) deposits , in Proceedings PACRIM 2015 Congress, pp 271–280 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 18, 2015

By C. L. Karr

Researchers at the University of Alabama are investigating artificial intelligence based computer models of mineral processing systems. Two approaches have been found to be particularly effective in developing data-driven computer models. The first approach employs neural networks which are computational paradigms based on the mechanics of the human brain. They are able to extract the basic relationships between input and output variables from large data sets. The second approach combines fuzzy mathematics with genetic algorithms to produce an adaptive modeling system. Fuzzy mathematics provide computers with the capability of manipulating abstract concepts like those which humans use so effectively in decision making. Genetic algorithms are search algorithms that mimic evolutionary processes apparent in nature. Together, these two techniques can be used to produce an effective modeling system. In this paper, the two approaches to modeling are compared and contrasted with respect to accuracy and computational time while used to model three mineral processing systems: (1) a grinding circuit, (2) a hydrocyclone separator, and (3) a flotation circuit.

Jan 1, 1997

By P. Geoffrey Feiss

The Piedmont province of the southern Appalachians is becoming the focus of interest for many exploration geologists. In the past, only those deposits with significant surface exposure have been exploited. Thus, few deposits have been found and relatively little exploration has been conducted in recent years. Modern geochemical and geophysical techniques can alleviate this problem of concentrating on exposed ore bodies by allowing us to "look through" the soil and saprolite to detect the presence of significant mineralization at depth. This paper will attempt to evaluate the feasibility and effectiveness of several geo¬chemical exploration techniques in the Piedmont, of Cabarrus and Stanly Counties, North Carolina. The area chosen for the study is shown in Figure 1, lying almost wholly within the Mt. Pleasant quadrangle, North Carolina. The area is on the eastern boundary between the Charlotte belt, a zone of plutonic and intermediate grade metamorphic rocks, and the Carolina Slate belt, a series of complexly interbedded volcanic and sedimentary rocks of predominantly low grade metamorphism. The area is now considered to be a 500 million year old active, continental margin.1 As is typical of most of the piedmont, outcrop is sparse. Figure 2 is a sketch map of the general geology of the area under study, showing the Charlotte belt rocks in the northwestern quadrant and slate belt rocks, to the east. Within the area are a number of old mines and prospects, the most famous of which are the Furniss and the Phoenix mines in Cabarrus County. All are reported to have contained Au and Cu. Ag and Pb were reported from some. A summary of the deposits is given in Table 1. Data used in this study are from three Master's theses conducted at the University of North Carolina at Chapel Hill. 3,3,6 In separate studies, well waters5, B-zone soils3, and vein and float quartz6 from the area described were sampled and analyzed. Each study concluded separately that geochemical anomalies in the vicinity of the ores justify use of that specific sample type in a geo-chemical exploration program. However, no comparative study of the methods has

Jan 1, 1977

By S. Hardcastle

Various controlled and ambient tests were undertaken to evaluate the performance of a variety of digital heat stress monitors, psychrometers and simpler temperature/relative humidity data loggers that measure, or determine, such parameters as: dry-bulb, natural wet-bulb, psychrometric wet-bulb and globe temperatures. In this comparison, funded by the Deep Mining Research Consortium, it has been found that all the instruments can competently measure dry-bulb temperature but the accuracy of other sensors could introduce significant uncertainty. For example the quality of relative humidity sensors and failure to correct for the barometric pressure difference in deep mines, directly impacts upon the calculation of psychrometric wet-bulb. The comparison has shown that the response of dry-bulb and globe temperature sensors can vary widely under different radiant heat conditions; however this would be negligible in most mines. Of more concern is the differing performance of the natural-wet bulb sensors especially at low relative humidity and low air velocity. Furthermore, from these tests and the currently available theory it was not possible to determine if any of the natural-wet bulb instruments measured that value correctly or validate any relationship between psychrometric and natural wet-bulb temperature at low air speeds where their difference is greatest. Consequently the uninformed use of some of the commercially available environmental heat stress monitors or derivations from other instruments could provide erroneous results affecting the work load category that can be accommodated or the rest ratio regime required.

Jan 1, 2009

A comparison of gold, platinum and sulfide ion selective electrodes was made in this investigation for determination of Eh in solutions containing sulfide ions as a model system. The comparison was made in terms of the accuracy of the measured response, response time, pH dependence, and reproducibility of measurement. In addition, the sensitivity of each electrode towards changes in sulfide ion concentration was measured in terms of the change in measured Eh per decade change in concentration of sulfide ions. On the basis of a detailed investigation of the electrode processes occurring at the surface of gold and platinum electrodes, it was postulated that within the pH range investigated these electrodes respond to changes in the hydrosulfide ion, HS-, concentration in solution. In comparison, the sulfide ion selective electrode is known to respond to changes in the sulfide ion, S-, activity in solution. Although the potentials measured with gold and platinum electrodes were mixed potentials, pretreatment procedures can be used to obtain a signal suitable for process control. For control of sulfide ions in flotation pulps, the use of a gold electrode pretreated at 1.0 V with respect to a standard hydrogen electrode is recommended.

Jan 1, 1990

ARTHUR PHILLIPS,* Bridgeport, Conn. (written discussion?).-It is to, be regretted that the very valuable paper by Messrs. Bassett and Davis did not appear in the early war period. The data presented would have been of inestimable service to inspectors, of cartridge brass who, admittedly, had little or no knowledge regarding the relation of grain size to temperature of anneal, and no real appreciation of, the significance of the Brinell hardness test. The paper is of considerable interest to, metallurgists also. WALTER R. HIBBARD, ? Bridgeport. Conn. (written discussion§).-The writer has carefully studied Messrs. Bassett and Davis's paper with considerable interest, inasmuch as our laboratory has tested cartridge brass by means of a Brinell machine. In March, 1917, at the suggestion of the Technical Department of the American Brass Co., we started a comparison of grain-size measurements and Brinell hardness of-cartridge brass with a gage of 0.1 in. or greater. This was continued until March, 1918, when we adopted the Brinell hardness test as standard for brass 0.1 in. gage or greater, and discontinued grain-size measurements upon this metal. The data collected during the test showed that the Brinell hardness indicated more accurately how the metal acted in actual working operations. It was also more reliable because two manipulators check themselves closer by the Brinell test than by the grain-size measurements. It also consumed less time in making the tests. Alfred V. de Forest, formerly assistant research engineer of our laboratories, has described the apparatus and some of the checking results in a paper read June, 1918, before the American Society for Testing Materials.1 The writer hopes that a more satisfactory. method for testing cartridge brass and gilding in gages thinner than 0.1 in. may be devised than the present method of grain-size measurements.

Jan 3, 1919

By R. A. Wyman

A comparison of the amount of minus-28-mesh product produced by a standard grinding test procedure is provided for 45 non-metallic materials. The percentage of product, the weight of product per unit of energy used and the weight of product per mill revolution are shown. The results exhibited excellent reproducibility and demonstrated an accurate comparison of grindability for non-metallic materials.

Jan 1, 1977

By James Addis, Zoheir Khademian, Marcia L. Harris, Charlie Matthews, Y Zheng

Shale gas wells can sometimes drill through coal reserves. Hypothetically, the caving of the gob from longwall coal mines may deform the shale gas well casing and potentially result in a breach. NIOSH researchers studied the permeability of the surrounding ground strata that may affect the potential for an inflow of gas into an underground mine environment. An overview and comparison of measured permeability values under differing cover depths (147 m and 353 m to the Pittsburgh coal seam) and mining cycle phase will be presented and discussed in this report. The findings highlight data-driven experimental evidence that affect the interaction between gas wells extraction and mining operations that may lead to potentially hazardous environments.

Feb 1, 2025

By M. Pillay

INTRODUCTION Heat stress continues to be a safety concern in underground mining. This is due to a number of reasons including increasing depths of mining, increased levels of heat generated from machines, ventilation systems being constrained from providing suitable levels of airflow and others. In order to assess if a thermal environment is safe for miners under normal or modified work arrangements, or to specify stop work conditions a heat stress index is used to guide decisions. Historically, a number of heat stress indices have been developed and applied in underground mines. These can be classed under three broad headings; single measurement, empirically based and rational indices. Do any of these indices perform better than the others? Which one allows simple determinations and decisions to be made in the mine? This paper aims to provide answers to these questions by comparing and contrasting three indices; effective temperature (ET), simple air cooling power (ACP) and Thermal work limit (TWL) for a range of typical mining wet and dry bulb combinations? The paper concludes with the identification of areas for future research. BACKGROUND Heat stress causes discomfort, increases physiological strain, decreases productivity and performance, and contributes to increased incidents [1]. Effective management and control of heat stress is particularly important in mining where hot working conditions are very common [2]. Heat stress index is a common indicator that is used by mine safety advisors and managers to guide decisions about safe work practices in mining under normal or modified conditions. According to Howes and Nixon [3] A safe heat stress control strategy for an underground mine has three elements: • Application of an environmental measure which reflects physiological strain with sufficient accuracy for the range of conditions encountered underground. • Acceptance of a functional relationship between the environmental measure and human performance which is used to optimise the environmental conditions achievable with either ventilation or ventilation and refrigeration. • A management control strategy based on the environmental measure which is designed to ensure that work in environments where excessive physiological strain may occur is prevented and corrective action is initiated. The link between these elements is an environmental measure that reflects the physiological strain a worker is subjected to. Since the turn of the twentieth century various indices of thermal stress have been developed (McPherson [4], Howes and Nixon [3], Brake [5]). In selecting a suitable environmental measure or index one problem that must be addressed is the ease with which it can be physically obtained relative to it accurately reflecting the physiological strain. No index can be universally applied and there is no single correct measure or index. However if an index has provided adequate control in a particular circumstance, then it can be regarded as correct for that situation.

Jan 1, 2019

By D. Marcotte, R. V. Dutaut

"In mineral resource evaluations, geostatistical methods known as global change of support allow prediction of the theoretical histogram and gradetonnage curves prior to interpolations or simulations of grades. Two methods commonly used by professionals to guide the choice of interpolation parameters and assess results are the discrete Gaussian model (DGM) and the indirect lognormal correction (IndLog). These models rely upon an estimate of the dispersion variance of the blocks, which is derived by numerical integration of the variogram model over a discretized block. Due to difficulties in obtaining well-formed traditional experimental variograms (especially in the presence of outliers and limited clustered data), many professionals prefer to use ‘normalized’ variograms such as correlogram (non-ergodic variogram), pairwise-relative, or variogram of the normal score transform. A series of simulations with different grade distributions and variogram models are used to assess the performances and robustness of the various variogram estimators with respect to the DGM and IndLog global change of support. Our results show that the traditional variogram, the correlogram, and normal score variogram have better performances, compared to pairwise, for both DGM and IndLog. Moreover, DGM provided better results than IndLog for the grade distributions that are not strictly lognormal. These findings provide valuable guides for geostatistics practitioners. IntroductionWhen reporting resource estimates,practitioners are required to follow generalstandards described in the NI43-101 (CIMguidelines), JORC, or SAMREC codes. One cangenerally recognize three main parts directlyrelated to the block model:•,Pre-processing: exploratory data analysis (EDA), domaining, capping, compositing, declustering, variography•,Processing: block size, neighbourhood, interpolation types (linear or nonlinear)•,Post-processing: classification, reporting.Pre-processing aims to simplify and strengthen the processing step. Ideally, domaining, capping. and compositing is aimed at defining a single homogenous population. During the processing phase, a common practice is to use a block size corresponding to the planned selective mining unit (SMU). In most precious metal deposits (gold, notably), the SMU size is frequently smaller than the recommended half data spacing (Journel and Huijbregts 1978), resulting in high estimation variance and either a high degree of smoothing if the regression slope is managed or a high degree of conditional bias if it is not. Most actual resource estimates are made using block sizes between one-quarter to one-sixth of the average data spacing, sometimes even smaller. In addition to the block size, the interpolation choices for the neighbourhood selection and interpolator (e.g. inverse distance (ID) or ordinary kriging) are often based on the Qualified Person’s (the QP) experience and some basic validation plots that often do not consider the conditional bias (e.g. trends or SWATHs plots, which are designed to compare two sets of population using a one-dimensional graph)."

Jan 1, 2018

By C. Haberfield, J. Szymakowski

Recent studies by the authors into the behaviour of jointed rock masses using direct shear testing have confirmed that joint spacing has a significant effect on rock mass strength. The rock mass failure envelopes assessed from these tests have been compared to failure envelopes obtained using the Hoek-Brown GSI criterion. Good agreement between measured and estimated GSI strength envelopes where obtained when joint spacing was considered in the assessment of GSI. Les études récentes conduites par les auteurs sur le comportement des joints rocheux employant l'essai direct de cisaillement ont confirmé que l'espacement a un effet significatif sur la force de la masse rocheuse. Les enveloppes de ruptures obtenues pour ces essais ont été comparées à l'enveloppe de rupture obtenue en utilisant le critère GSI Hoek-Brown. Une bonne corrélation a été constatée entre les enveloppes obtenues expérimentalement et les enveloppes calculées par la méthode GSI quand l'espacement des joints a été pris en considération dans l'évaluation de GSI. Kuerzliche Untersuchungen der Autoren betreffs Reaktionen von gebrochenen Felsmassen zu direkter Scherkraft, bestaetigen, dass die Abstaende von Rissen einen deutlichen Einfluss auf den Widerstand der Felsmassen hat. Die Bruchbereiche der Felsmassen die von diesen Untersuchungen entwickelt wurden, wurden verglichen mit den Bruchbereichen, die man mit der Anwendund der Hoek-Brown GSI Formulierung erhaelt. Eine gute Uebereinstimmung zwischen gemessenen und errechneten GSI Festigkeitsbereichen wurde erzielt, wenn der Abstand der Risse in der Berechnung der GSI in Betracht gezogen wurde.

Jan 1, 2003

By R. Bishop, J. Baggett, J. Monsalve, N. Ripepi, A. Soni

Technology plays an ever-increasing role in improving the safety and efficiency of mining operations. Laser scanning and photogrammetry are two useful methods for capturing 3D digital representations of real world objects. While both technologies have been applied to the mining industry in numerous ways, the practical applications in an operating underground limestone mine has been tested for this paper, including for visualization and site characterization. Each technology is capable of creating highly detailed geospatial point clouds, but are all point clouds created equal? This paper presents a comparison of a laser scan and photogrammetry of a limestone pillar and addresses the strengths and limitations of each method for creating digital models of operating underground limestone mines. INTRODUCTION The United States crushed stone business is a ~$14 billion per year industry representing 1,430 companies which operate 3,782 mining operations across the 50 states. In 2017 alone, 1.33 billion tons of crushed stone was produced with 76% used predominately for road construction and repairs, but also for the production of cement, lime, chemical and agricultural uses. Over 70% of domestic crushed stone producers source their material from limestone and dolomite deposits, with currently only 82 mines (2%) operating underground (USGS, 2018). Underground mining requires a different technical skillset, and poses great challenges for production that must be both safe and economical. Therefore, there are many risks that an operation must mitigate in order to produce underground limestone. Some of the challenges in underground limestone mining involve geological hazards that are unique to the rest of the industry. The geologic features such as faults and weaknesses can be difficult to assess in a production environment (NIOSH, 1998). The consequences of failure due to improperly designed underground mining ground support systems, such as from a roof failure, are not only life threatening for the miners themselves, but can easily shut down an entire mining operation.

Jan 1, 2019

To simplify programming, image analyzers commonly measure either linear intercepts or the areas of particles and grains to determine liberation based on polished section mounts. However, the concentration of minerals by flotation is based on reagents that interact with the exposed surfaces of the minerals. Thus, it is often perceived that image analyzers should measure the perimeter of the mineral of interest in the ore particles. A comparative liberation study of thirteen samples collected from a flotation plant processing a complex base metal sulfide ore showed that the liberation of the ore minerals determined by area measurements is very similar to the liberation determined by the exposed perimeters. The liberation determined by exposed perimeters is more appropriate only for those cases where the mineral texture is so complex that it is retained in the small particles generated in conventional grinding operations.

Jan 1, 2002

By H. T. Chiwaye

Risk analysis is an important step in the design of rock slopes in open pit mining. Risk is defined as the product of the probability of slope failure and the consequences of the failure, and is generally evaluated in terms of safety and economic risk. Most of the risk analysis done at present is based on the use of limit equilibrium (LE) techniques in evaluating the probability of failure (POF) of the slopes. The approach typically makes use of full Monte Carlo simulations of the limit equilibrium models, with all uncertain variables randomly varied. The number of required simulations is generally over a thousand, at times as high as 20 000, in order to produce statistically valid results of the POF. Such an approach is clearly not practical when using numerical modelling programs dueto the high computational effort required. This paper explores the impact of using numerical modelling instead of the traditional LE techniques in evaluating the probability of slope failure. The difference in the overall assessed risk, in terms of economic impact, for the mining operation is then evaluated. With numerical models, approximate methods are used in the calculation of the probability of failure instead of full Monte Carlo simulations. This paper will use a method called the response surface methodology (RSM) for estimating the POF from numerical analyses. Simple slope models were used to verify the accuracy of the RSM method by comparing the results with those obtained from full Monte Carlo simulations. It is shown that there is good agreement between the POF values computed using full Monte Carlo simulation and those obtained using the RSM method. Finally, the use of numerical modelling in the assessment of risk is shown to bring a significant difference in the result compared with that from LE methods. One of the reasons for the difference is that LE models tend to underestimate the failure volumes and hence the consequences of slope failure.

Jan 1, 2010

By R A. Binns, S Murao

The PACMANUS and Jade deposits are two active hydrothermal fields that are forming massive sulphide deposits at the Pacific rim margin. Both are associated with felsic submarine volcanic rocks and both occur in back-arc settings. However, PACMANUS is associated with almost sediment-free dacites and lies on the crest of a volcanic ridge, whereas Jade occurs in a heavily-sedimented tectonic depression associated with a basement of pumiceous rhyolite. The PACMANUS deposit is richer in Cu and Au, and Jade in Pb. Zinc, Ag, As and Sb contents are similar. Sulfide textures at PACMANUS suggest formation of Cu and Zn sulfides by simultaneous double-diffusion involving inwards-moving seawater mixing with outwards-moving hydrothermal fluid. By contrast, at Jade there is a more complex history of formation where initial growth of barite on the sediment surface, probably associated with microbial activity, formed an impervious cap which trapped higher temperature hydrothermal solutions.  

Jan 1, 1995

By Y. C. Kim

Although the first published optimum pit limit design algorithm by Lerchs-Grossmann dates back to 1965, the majority of the open-pit mines in the U.S. has not as yet adopted such a rigorous optimization algorithm. Instead, the floating cone approach initially developed by Kennecott Copper in 1961 is still used today for various reasons. However, shortcomings with the floating cone algorithm, particularly for precious metal deposits with erratic mineral distributions, have provided a renewed interest in optimizing algorithms.

Jan 1, 1988