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The cost of preparing a feasibility study is notoriously difficult to estimate. Studies for mining projects are typically commenced when an exploration programme has identified a mineable resource and pre-feasibility studies have shown that development of the resource would lead to an economically viable project. Pre-feasibility studies will normally include an estimate of the cost of a formal feasibility study and this estimate would then be firmed up before a commitment is made to proceed with the formal study. Data for preparing the feasibility study cost estimate will be sketchy, geological investigations, metallurgical testwork, and marketing studies may be needed before the scope of the project and hence the scope of the formal study can be finally determined. Before an estimate of the work required and hence of the cost of the feasibility study can be prepared the source of project funds must be decided. Studies for internally funded projects are often less rigorous than those which must be "bankable" and subject to the scrutiny of external financial institutions. This paper sets out suggestions for preparing more accurate cost estimates for feasibility studies by ensuring that all activities are included and shows how a staged approach to preparing such studies can minimise costs and guard against cost overruns. It also provides a case study showing how the estimate compared with actual costs for a recent feasibility study completed by Pancontinental Mining Limited.

Jan 1, 1990

By R. Karl Zipf, Z. T. Bieniawski

"SummaryAs part of an effort.to understand the mechanics of fine fragment formation in coal, which is important in studies of respirable dust due to mining, fracture toughness measurements and the strain energy density (SEO) theory were applied to calculate the crush zone size under a cutting tool in coal. This · zone is the major source of fine fragments in the 1 to 10 µm size range. The model used in these calculations is a boundary element program containing a failure criterion based on the SEO theory. The boundary element program calculates linear elastic stresses at numerous points in the coal material ahead of a cutting bit. These stresses arc then input to a subroutine called critical ftaw length and orientation (CFLO) which uses the SED theory to determine the CFLO for a small crack at the boundary element stress computation point. The extent of crushing is based on earlier postulates about . the role of inherent flaws in a fragmentation process. To form 1 to 10 µm fragments requires firstly a local stress strong enough to activate flaws with a characteristic length less than 1 to 10 µm and secondly, a flaw density sufficient to provide an average spacing between flaws also on the order of 1 to 10 µm. The locus of active lO µm ftaws represents the maximum possible extent of fine fragmentation in the 10 µm or less size range assuming that a sufficient inherent flaw density exists. The approach offers a first order approximation to the extent of crushing under a tool tip. The size and shape of the crush zone volume is affected by the attack angle and geometry of the tool.IntroductionFine fragment generation in the 1 to 10 µm size range under the action of a generic coal cutting tool may be explained on the basis of fracture mechanics which suggests two major sources of fine fragments: first in a crush zone near the tool tip and second by shear fracturing. along major macrocrack surfaces (Zipf and Bieniawski, 1988a). In this paper, fracture toughness measurements and the strain energy density theory are used to calculate the crush zone size. This zone represents the major source of fine fragments in the 1 to 10 µm size range and understanding the mechanical factors controlling its size represents a first step toward using fracture mechanics to characterize the ·tendency of various coals to produce undesirable fine fragments."

Aug 31, 1989

By B. Birol, M. N. Saridede

"Slag density is a significant factor in determining the process efficiency of the electroslag remelting (ESR) process, where calcium fluoride (CaF2)-based slag is formed synthetically to refine metal ingots. Although there are some former studies investigating the density of CaF2-containing slags, the prediction models focusing on them are applicable only to some specific systems. The present study aims to build a model to predict density for a wide range of CaF2-containing ESR slags. To investigate density for various slag compositions, CaF2-Al2O3-based and CaF2-Al2O3-CaO-based slag compositions were prepared. Additionally, some minor constituents like FeO, MgO and MnO were added to a 5:3:2 CaF2-Al2O3-CaO slag in order to investigate the effects of these constituents on the slag. The volumes of the prepared slags were measured in a tube furnace at 1450-1550 °C using the sessile drop technique, and their densities were calculated. The results showed that for the slags, density is related to optical basicity, and therefore a prediction model based on an Arrhenius equation was built. The model was tested with data from literature, and its limitations and validity are discussed.IntroductionThe electroslag remelting (ESR) process is a refining method in which a metal ingot is remelted under a synthetic slag. These synthetic ESR slags are mainly composed of calcium fluoride (CaF2), calcium oxide (CaO) and aluminum oxide (Al2O3). Other constituents like iron oxide (FeO), magnesium oxide (MgO), manganese oxide (MnO) and chromium oxide (Cr2O3) are added to this system in relatively low amounts, according to the type of steel ingot to be refined. The prediction of slag properties, such as electrical conductivity, viscosity and density, is crucial for the selection of the synthetic slag in order to obtain the required process parameters, like temperature, the passing time of the molten metal droplet through the slag, and metal-slag separation (Akbari, Reitz and Friedrich, 2009; Hara and Ogino, 1981; Mattar, El-Faramawy and Fathy, 2002; Mehrabi, Rahimipour and Shokuhfar, 2005; Presoly, Korp and Schneider, 2008).As slag density affects metal-slag separation in the ESR process, predicting the density of an ESR slag is important for appropriate refining and improved product quality. Although there are many studies investigating the density of slags (Akbari, Reitz and Friedrich, 2009; Aune, Hayashi and Sridhar, 2005; Hara and Ogino, 1981; Matsushita, 2011; Mills and Keene, 1987, 1981; Seetharaman et al., 2013; Shu, 2007; Shu and Chou, 2013; Sikora and Zielinski, 1974; Xu et al., 2012; Zhang and Chou, 2010), the prediction models built are generally valid for oxide-containing slags (Aune, Hayashi and Sridhar, 2005; Bottinga and Weill, 1970; Mills and Keene, 1987; Seetharaman et al., 2013; Shu, 2007; Xu et al., 2012; Zhang and Chou, 2010). These models were built on either the molar volumes of the constituents (Bottinga and Weill, 1970; Mills and Keene, 1987) or the thermodynamically calculated enthalpy or free energy of mixing, which can be applied to a system containing constituents sharing an ion, such as an O- ion for oxide systems (Aune, Hayashi and Sridhar, 2005; Hillert, 1980; Persson et al., 2007). Some recent studies modeled the density of some oxide slags on their optical basicity (Shu, 2007; Shu and Chou, 2013; Xu et al., 2012; Zhang and Chou, 2010)."

Jan 1, 2016

By T. Feroze, B. Genc

"The ventilation of underground coal mines plays an important role in minimizing the risk of methane and coal dust explosions. The ability of ventilation, with the use of line brattices (LBs), to remove methane and coal dust in empty headings is dependent on the amount of air leaving the LB and entering the heading. The quantity of this air depends on the associated system variables, namely heading dimensions, settings of the LB, and velocity of air in the last through road (LTR). However, the exact effect of these system variables on the flow rate at the exit of the LB in an empty heading is not known. The installation of LBs in South African coal mines is generally carried out based on experience. This can result in overor under-ventilation and may increase the cost of providing ventilation or cause accidents, respectively. In this paper, using computational fluid dynamics (CFD), the air flow rate at the exit of the LB in an empty heading was estimated using full-scale three-dimensional models. The CFD model used was validated using experimental results Firstly, the settings of these three system variables were varied, the flow rates at the exit of the LB were measured, and finally the results were used to calculate the effect of each system variable. The outcome is a mathematical formula that can be used to estimate air flow rate at the exit of the LB in empty headings for any practical scenario.This paper will help the coal mining sector in South Africa by providing estimation models based on scientific reasoning for the installation of LBs, and will also serve academia as part of the curriculum towards educating future mining engineers."

Jan 1, 2016

By L. C. Atkinson

A three-dimensional finite element Ground-water flow code has been developed that incorporates saturated/unsaturated, two-regime flow (i.e., both Darcian and non-Darcian) and solves for the seepage face at a surface of outflow. This code is capable of more realistically predicting ground-water inflows to an open-pit mine under the throttling effects of non-Darcian flow. The height of the seepage face on highwalls and the shape of the phreatic surface in the vicinity of the pit that it calculates can also produce more probable estimates of pore pressures for analysis of slope stability.

Jan 1, 1992

By Aidan Giblett, Michael McGlynn, Peter Radziszewski

"On the basis that 99% of the energy input into a mill is converted into heat, it is possible to estimate the amount of energy captured in the slurry, the amount that is lost to the environment as well as the possible means to reduce such losses. As a result it becomes possible to estimate the potential amount of energy that can be captured by technologies such as thermoelectric generators or even Sterling engines. Furthermore, it has been suggested that the energy recovery potential dry grinding circuit could be as high as twice that of wet grinding circuits.In this paper, the energy recovery potential of dry grinding will be explored by examining the case of the Newmont Carlin mine dry grinding circuit. The paper will open with a review of the energy recovery potential of a few wet grinding applications followed by a description of the dry grinding circuit and a definition of the control volume around that circuit. A thermodynamic model will be used to estimate the circuit discharge temperature and an estimate of any losses as well as provide an estimate of the potential impact of different means to reduce energy losses. The paper will close with a discussion of the assumptions used in model development."

Jan 1, 2016

By F. F. Aplan

INTRODUCTION Coal is a solid combustible mineral substance resulting from the alteration of vegetable matter largely in the absence of air. It occurs in nature with varying percentages of mineral matter associated with and incorporated into the coalified material. If the amount of this inorganic mineral matter is sufficiently small, and if selective mining can be practiced so as to avoid the incorporation of ash- bearing material from adjacent strata and/or parting seams, the coal can be used as-mined. Otherwise, it must be given a preparation treatment. In 1980 the bulk of the approximately 525 coal preparation plants were located in the eastern half of the U.S., largely in the Appalachian and to a lesser extent in the midwest coal fields (1). Only 17 of these preparation plants were located in the west; these were in Colorado, New Mexico, Utah, Washington and Wyoming. In the past, however, a great many more preparation plants were operated in these and other western states. The upsurge in both the domestic and world- wide demand for quality coking and steam coal will certainly lead to an increase in the number of preparation plants in the west. In fact, there has been a massive development of coal mines and their associated preparation plants across our northern border in Alberta and British Columbia, largely to serve the export coking and steam coal market. Most of the tremendous increase in newly-mined coal in the western U.S. has come from thick seams of inherently low-sulfur, low- ash coal, easy to mine selectively without significant contamination with ash-forming minerals and requiring no preparation. Because of

Jan 1, 1983

By Margaret Armstrong, Chris Roth

Abstract -Estimating ore reserves for vein type deposits is a two-stage procedure: first, calculate the geometry of the vein system, and second, estimate the grades within this system. The grade estimation can only be consistently performed if the vein geometry - its size, shape and orientation - has been correctly characterized. Getting the size and shape of the different veins right means that the ore tonnages will not be artificially inflated, e.g., by falsely classifying host rock as veins. Similarly, correctly estimating their orientation and location helps mine management decide on the appropriate mining technique, selective or not. When applying geostatistics to estimate the vein geometry all available information needs to be used and not just the standard lithologic indicator of being or not being in a vein.

Jan 1, 1998

By D. E. Larson

The U.S. Bureau of Mines has developed a image analysis methodology to correlate the energy consumed during the grinding of an ore to the mineral liberation achieved. Energy consumption values are obtained using a laboratory-scale ball mill equipped with a torque sensor, and an automated image analyzer is used to determine the liberation present in ground products. By combining liberation information with energy consumption data an appraisal can be made of the energy required to liberate the mineral(s) of interest. Results of tests performed on a complex sulfide material determined the effects of grind duration on the liberation achieved and the energy efficiency.

Jan 1, 1995

By D. E. Larson

The U. S. Bureau of Mines has developed a image analysis methodology to correlate the energy consumed during the grinding of an ore to the mineral liberation achieved. Energy consumption values are obtained using a laboratory-scale ball mill equipped with a torque sensor, and an automated image analyzer is used to determine the liberation present in ground products. By combining liberation information with energy consumption data an appraisal can be made of the energy required to liberate the mineral(s) of interest. Results of tests performed on a complex sulfide material determined the effects of grind duration on the liberation achieved and the energy efficiency.

Jan 1, 1995

By J. A. Gutierrez-Rodriguez, R. J. Purcell, F. F. ApIan

"Based on contact-angle measurements and the work of adhesion equation, the hydrophobicity of a wide variety of coals was found to decrease with decreasing rank, fixed carbon and total carbon content and with increasing oxygen and hydroxyl content. The estimated hydrophobicity, based on the water-sessile-drop contact angle, is '\.. 20% for lignite, increases with increasing rank up to a maximum of 'V70% for low (LV) and medium (MV) volatile bituminous coals and then decreases somewhat for anthracite. Using the captive-bubble technique, the calculated hydrophobicity ranges from '\.. 0% (below HV A bituminous rank) to a maximum of 55% for L V-MV coal. The former estimation is believed to be the more accurate. While the water-sessile-drop contact angle as measured on a polished-coal surface is usually larger than that shown by the captive-bubble method, the two values were found to converge at""' 95% relative humidity. It is proposed that the surface of coal consists of three kinds of sites: strongly hydrophobic, weakly hydrophobic and hydrophilic. The sessile-drop technique measures the total hydrophobic sites whereas the captive-bubble method measures only the more strongly hydrophobic sites. A water film covers the weakly hydrophobic sites preventing their detection by the captive-bubble technique.INTRODUCTIONCoal is a mixture of the degradation products of plants and of mineral matter. The appearance and properties of a specific coal is determined by the nature of the original vegetation and the extent of the physical and chemical changes which have occurred after deposition. The coalification process may be considered to have started with peat formation followed by a transition to lignite due to burial under sediments and metamorphic processes. Further metamorphic transformation to bituminous coals and, finally, under intense metamorphic action, to anthracite causes the carbon content and rank of the coal to increase. With such a wide variation in their genesis and composition, equally wide variations in the degree of hydrophobicity of different coals may be expected. It is the purpose of this paper to provide a means of estimating the hydrophobicity of a given coal sample based on rank parameters."

Jan 1, 1989

By Seanley C. Suboleski

This paper examines the likely productivity improvements that have resulted from the introduction of technological advances in underground coal mining during the decade from 1977 to 1987. Included in these advances are the changes in longwall mining; the introduction of larger, more reliable, more repairable continuous miners and shuttle cars; the introduction of remote control and flooded-bed scrubbers; supersections; and other improvements. Procedural improvements are also examined and quantified, the unexplained gains in productivity are attributed to??other factors", among them an increasing maturity of the work force, stabilization of the mining laws, increased labor-management co-operation, and economic urgency.

Jan 1, 1990

By J. A. Taylor, R. J. Fowell

Abstract: The amount of published literature pertaining to the field of rock mechanics has increased markedly in recent years. Whilst computer applications aid our understanding of the mechanisms of pillar instability, the applications do not take into account the effect of time; thus the determined pillar factor of safety has limited meaning. A more realistic approach would be to consider pillar stability in terms of time to failure. However such an approach would require a reasonable estimate of the in-situ pillar mass strength and a validated methodology linking the time to failure with in-situ pillar mass strength and the geometric layout of the working. Résumé: Le volume de bibliographie au sujet de la mécanique des roches a augmenté considérablement ces derniêres années. Alors que des modeles informatiques aident a la compréhension des mécanismes d'instabilité de pilliers, ces modèles ne prennent pas en compte les effets du temps; ainsi, la determination du coefficient de surete du pillier a un sens limité. Une approche plus réaliste devrait considérer la stabilité du pillier en fonction du temps de défaillance. Cependant une telle approche exigerait une estimation raisonnable de la resistance du massif rocheux du pillier ainsi qu'une méthodologie qui lie le temps de défaillance avec la résistance in-situ du massif rocheux du pillier et la géometrie de l'excavation souterraine. Zusammenfassung: Die Anzahl der Veröffentlichungen auf dem Gebiet der Felsmechanik ist in jüngster Zeit sehr gestiegen. Computerprogramme sind wertvoll um den Mechanismus der Pfeilerunbeständigkeit zu verstehen, aber sie vernachlässigen den Zeiteffekt. Daher haben die errechneten Sicherheitsfaktoren der Pfeiler nur begrenzte Bedeutung. Eine realistischere Bewertung wäre, die Stabilität der Pfeiler auf Grund der Zeit bis zum Verfall zu beurteilen. So ein Verfahren würde eine Schätzung der in-situ Gebirgsfestigkeit und eine validierte Methologie, die die Zeit zum Verfall in Abhängigkeit der in-situ Pfeilerfestigkeit und der geometrischen Auslage der Grube zusammenbringt, brauchen.

Jan 1, 2003

By I. Ocak

The modulus of elasticity of rock material (Ei) is an important rock property that is used as an input parameter in the design stage of engineering projects such as dam and tunnel constructions, mining excavations, and so forth. However, determination of the modulus of elasticity is sometimes difficult to obtain by laboratory tests because high-quality cores are required. For this reason, empirical methods for predicting the modulus of elasticity of rock material have been popular research topics in recently published literature. In this study, the relationships between the uniaxial compressive strength (UCS), unit weight (?) and modulus of elasticity for different types of rocks were analysed by using 177 data obtained from laboratory tests carried out on cores obtained from drill holes within the area of the Kadiköy-Kartal Metro line (Istanbul, Turkey). Keywords: Kadikoy?Kartal Metro, uniaxial compressive strength, unit weight, estimating the modulus of elasticity.

Jan 1, 2008

By K. C. Mills

The objective of this work was to provide process engineers with values of the physical properties of various slag systems involved in high-temperature processes. Software that calculates the thermo-physical properties of slags from chemical composition is available on the www.pyrometallurgy.co.za website. This paper outlines the principles underlying the various models available in the program. The software calculates the following properties of crystalline, glassy, and liquid slags (where appropriate) as a function of temperature: heat capacity, enthalpy, density, viscosity, thermal conductivity, electrical conductivity, and surface tension. We hope, in the future, to update the program to (i) add new models as they become available, (ii) remove any ?bugs? discovered in existing programs, and (iii) provide guidance on the limitations of individual programs.

Jan 1, 2011

By R. L. Grayson, W. E. Wallace, T. Simonyi, J. C. Harrison

"Application of an SEM-based methodology suggests a reason for past contradictory results on the relationship between quartz and coal workers' pneumoconiosis (CWP). Results indicate that coal seams with the same bulk analysis of quartz may have different amounts of surface-availablequartz. Our research shows that the amounts of pure and surface-available quartz in a respirable dust vary directly with the rank of a coal seam, except in the case where rock materials are mined. The estimated amount of surface-available quartz therefore provides a measure of the quartz-related fibrogenic potential of a respirable dust.INTRODUCTIONFrom our previous work (Grayson, 1991), we have shown that the amount of pure quartz in a respirable coal mine dust sample appears to vary directly with the rank of the seam (using fixed carbon as the basis for comparison), except when a substantial rock parting, roof or floor are mined. Our other work (Wallace et al., 1989) showed that high-silica particles in a clay mine may generally be coated with clay, rendering the quartz core non-available for surface reaction in the lung. The combination of these findings led us to hypothesize that the coating phenomenon may indeed be present in coal mines as well, and that a rank relationship may be present regarding this phenomenon. Thus higher rank coal seams may have more surface-available quartz as well as more pure quartz particles in their respirable dusts. The scientific protocol for testing this hypothesis and the results obtained to date are discussed in this paper. Thus far, there is no reason to doubt that the relationship holds."

Mar 1, 1992

By William E. Wallace, Larry Grayson, Thomas Simonyi, Joel C. Harrison

Application of an SEM-based methodology suggests a reason for past contradictory results on the relationship between quartz and coal workers' pneumoconiosis (CWP). Results indicate that coal seams with the same bulk analysis of quartz have different amounts of surface-available quartz. Our research shows that the amounts of pure and surface-available quartz in a respirable dust vary directly with the rank of a coal seam, except in the case where rock materials are mined. The estimated amount of surface- available quartz therefore provides a measure of the quartz-related fibrogenic potential of a respirable dust.

Jan 1, 1992

By G. D. Naugle

Deep open-pit mines invariably affect the local and regional hydrologic systems. Pit dewatering, occurring during mining operations, puts an obvious hydrologic stress on these hydrologic systems. However, post-mining hydro-logic impacts resulting from the pit refilling with ground water following the cessation of mining activity can also be significant. Prediction of the rate at which the post-mining pit will fill with ground water is a critical aspect of assessing such long-term hydrologic impacts. Numerical ground-water flow modeling prov1des a method that can be used to predict the rate at which pits will fill with ground water.

Jan 1, 1992

By G. D. Naugle, L. C. Atkinson

Introduction Deep open-pit mines invariably affect the local and regional hydrologic systems. Pit dewatering, occurring during mining operations, puts an obvious hydrologic stress on these hydrologic systems. However, post-mining hydrologic impacts resulting from the pit refilling with groundwater following the cessation of mining activity can also be significant. The prediction of the rate at which the post-mining pit will fill with groundwater is a critical aspect of assessing the long-term hydrologic impacts. Numerical groundwater flow modeling provides a method for predicting the groundwater refilling rate of the pit. The rate at which pit "lakes" fill depends on several factors: •the rate and duration of pit dewatering; •the depth and size of the ultimate pit and •the pre-mining hydrologic regime. These factors can be incorporated into a detailed numerical groundwater flow model that can then be used to assess the effects of dewatering and post-mining recovery on the local and regional hydrologic systems. A sufficiently detailed, numerical groundwater model provides the oportunity to: •account for complex geology near the pit; •assess the impact of active pit dewatering and •predict the long-term impacts of post-mining groundwater flow into the pit. A detailed groundwater model incorporating these items has been developed and applied at an operating open-pit mine. Developed by Durbin and O'Brien (1987), the three-dimensional, finite-element, groundwater flow model was used to represent the hydrologic system of an approximately 253-km2 (98-sq mile) area surrounding the pit. Historical groundwater elevation data, stream flows and meteorologic, geologic and geophysical data were used to establish the dimensions and initial conditions for the model. Steady-state conditions, representing the pre-mining local and regional hydrologic systems, were simulated using the initial conditions incorporated into the groundwater model. The groundwater model was then utilized to simulate various dewatering programs, to predict the filling rate and the groundwater depth in the ultimate pit once mining activities are complete and to assess the long-term impacts on the regional groundwater flow system. Development of pit lake model Groundwater modeling efforts were completed in two phases. The first focused on pit dewatering activities, while the second phase concentrated on the post-mining effects on the hydrologic system. The final estimates of groundwater elevations calculated during the pit dewatering simulations were used in predicting the post-mining recovery of the hydrologic system. The groundwater model was also modified prior to the second phase to account for the volume of rock removed during mining activities. To account for the actual volume of rock mined, the geometry of the post-dewatering model grid was modified to approximate the final pit geometry. The depth and width of the ultimate pit were divided into eight idealized stages that represented significant changes in the bench geometries. These eight stages were then introduced sequentially into the model according to the predicted water elevations within the pit. In this way, changes in the volume and depth of water within the pit were accounted for through time. Once the ultimate pit geometry was accounted for in the model, it was necessary to assign new hydraulic characteristics to those parts of the model grid (elements) that represented excavated rock. The solution of the numerical model requires that finite hydraulic conductivity values be assigned to the portion of the groundwater model that represents excavated rock. Therefore, the calculated groundwater elevations differ, somewhat, between the edges and the center of the open pit. These model-calculated water elevations at the edge and in the middle of the open pit represent the elevation of water that would occur in the pit lake. To minimize the error in the estimated level of water within the pit lake, the hydraulic conductivity was increased to a value that would: •minimize the predicted difference between the groundwater elevations across the open pit and •produce a numerically stable solution. Specific storage is the hydrologic parameter that accounts for the water produced by compaction of the aquifer matrix. To predict the groundwater volume that would flow into the ultimate pit, this parameter was assigned a value equivalent to the compressibility of water. This value of specific storage reflects the post-mining groundwater storage occurring as an open body of water. Additionally, a specific yield of 1.0 was assigned to the pit elements to represent the 100% porosity of the open pit. In

Jan 1, 1994

By S Rice, A Midlin

Many of the stacking and reclaiming machines employed in the mining industry today are operating in ways that were never envisaged in the days before they were commissioned, with greater throughput, increased annualised operating hours and load cycles well in excess of their original specification requirements being the norm. In many cases these machines were supplied prior to the widespread use of finite element modelling or, in the era when such software became commercially available, those supplied designed using simplified and/or coarser meshes than would be employed today. With many of these machines being expected to operate for many years to come, it is important that their ongoing reliability be maintained and their operational limits understood. In this paper, a case study is used to outline the method required for estimating the fatigue life already consumed and the likely real life left in a machine. By reference to the machineÆs prior operating history, the use of strain gauges in the field and the development of finely meshed finite element analysis (FEA), a coherent picture of the machineÆs operational state can be generated and then investment/maintenance decisions made to ensure continuity of machine operation.

Jan 1, 2007