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By M. Nowak

Extreme high grades often exert too much influence on surrounding block estimates, leading to a smearing of high grades that can cause overestimation of mineral resources. This concern underlies the decision to cap high grades, i.e., to lower the highest grades in a drill hole data set to some level deemed to be reasonable for producing reliable resource estimates. The choice of a capping level can, by itself, have a large influence on the analysis of the economic viability of a project. Despite this, it is often a choice that is made arbitrarily, guided more by art and tradition than by sound technical analysis. This paper makes suggestions for good capping practices, using methods and procedures that have been presented elsewhere, in the technical literature and in conference papers. The authors propose to use capping only if absolutely necessary, and review examples of cases where capping may not be necessary, or where capping does not make the estimates more reliable. It addresses two particular instances where capping is recommended: (1) where there is good reason to believe that estimation with uncapped grades will overstate the true underlying average grade, and (2) where there is potential for overly optimistic assessments of local block grades in the vicinity of some very high grade assays. The proposed capping practice is based on adjustments to only a very few high grade assays. The level of this capping can be assessed by bootstrapping and through analysis of the effect of extreme values on summary statistics like the average and the coefficient of variation. The paper recommends that good practice include an examination of the potential for local overestimation in higher grade areas.

Aug 1, 2013

By Roy EI. Durr, Glen R. Davidge

"This paper presents the results of structural analyses and full-scale destructive tests conducted on liner plate culverts. The purpose of this work was to establish a design method and evaluate the suitability of using these structures in potential roof-fall areas for a rehabilitation application in lower stress and relaxed mining environments. Field evaluation of the design is currently in progress.Theoretical ultimate resistance functions were established for two different culvert shapes and were found to be representative of their experimental behaviour. The ultimate resistance function was used to determine their plastic behaviour to a rapidly increasing deflection condition, to determine the energy absorption capacity of these structures, and to predict their response to impact loading.IntroductionThe Kidd Creek mine of Falconbridge Limited is located justnorth of Timmins, Ontario. The area under rehabilitation for which this program was developed is the 2600 level of the No. I mine. The problem of effectively securing selected drifts at the 2600 level in NO.1 mine, for access to a high-grade ore block, is key to the economics of the operation. Diamond drill test holes had indicated a loosened rock mass above the 2600 level of about 7.5 m thick in response to the extensive mining operation below this level. This level forms the arbitrary boundary between the No. I and No. 2 mines, and has extensive volumes of cemented rock fill below it and largely untouched ore above it to the 2000 level in the North orebody. The walls at that level were showing relaxed ground conditions typical of de-stress: sub-horizontal joints opening up, and peeling.Due to the ground conditions, the consequent safety risks, the high grade of the ore, the potential production delays, and the likelihood of several phases of rehabilitation, regularly used drift rehabilitation employing rock bolts, cable bolting, or shotcrete was not practical. Two options were deemed possible alternatives to suit these conditions, steel sets with blocking and lagging, and liner plate culverts with backfill. Culverts were chosen."

Jan 1, 1995

By S. Gößling-Reisemann

Most copper ores contain valuable co-products such as molybdenum, gold, silver, nickel, etc. Sulphuric acid and steam are valuable by-products, which are generated dur¬ing copper production. The environmental impacts from mining and refining therefore need to be shared between these by-products and co-products, an issue in Life Cycle As¬sessment (LCA) referred to as allocation. There are different, recognised methodologies for doing so: burdens can be allocated based on the market values of these commodities, they can be allocated by mass, volume, molar amount, functionality, or other physical, technical or economic factors. All of these methodologies have their respective merits and restrictions, and the choice is usually case specific. Nevertheless, the choice between alternative methodologies can have dramatic effects on the LCA results. Recycling in LCA has to be handled in a similar way, as it essentially constitutes a special case of co¬production. The existing standards (ISO 14040 ff.) allow different methods for imple¬menting recycling and allocation into metal LCAs (open loop, closed loop, value cor-rected substitution, etc.), which are still a subject of discussion in the scientific community. However, the methodology used can significantly influence the ecological profile of copper and copper products. We will present an overview of the different methodologies available for including recycling and allocation and give an analysis of how the meth¬odological choice affects the final LCA results. This work will be followed up by quantitative case studies.

Jan 1, 2007

By M. G. Lipsett

General Challenges for Mining & Mineral Processing Operations ? Capital-intensive industry ? Ongoing cost pressures ? Remote locations ? Workforce demographics ? Dynamic, unstructured, rugged environment

May 1, 2008

By F. Hassani, J. Peck, D. J. Lucifora

The performance of a rotary blasthole drill is heavily dependent on the material being drilled. This material is a microcosm of the in-situ geology that makes up the surface mine in which the rotary blasthole drill is deployed. The performance metrics that are influenced by the in-situ geology are penetration rate (distance drilled per unit time), rotary torque and to a lesser extent rotary speed and vibration. For simulation and testing purposes it is useful to have a validated plant model based upon the application of study. Once validated, a plant model can be used to perform simulation based testing as a supplement and possibly in place of more expensive and logistically complex field testing. Previous studies in the field of rock mechanics have supplied proven models that relate the performance of a rotary blasthole drill to the material being drilled for a given rock type with a given drill bit. In this study, field based experiments were conducted in an active surface mine on a working rotary blasthole drill and the corresponding monitoring while drilling (MWD) data was recorded. Data analysis was then performed on the collected field data. The techniques used successfully fit the collected MWD data to the previously proven rock mechanic models. This paper explores the theory relating rotary blasthole drill performance to the material being drilled, illustrates the required data collection and data analysis techniques, and demonstrates the ability of these techniques and the known rock mechanic models to provide a simulated plant model for the drilling process that can then be validated. This validation is also discussed.

Jan 1, 2015

By R. Alarcón Sch., R. Abel F.

For many years, copper cathode quality has been a priority for end consumers, since it affects the variety of products that can be obtained from them. From the beginning, physical and chemical quality of the wire bars was controlled, as this product was used to obtain wire rod and other forms of copper by wire drawing. At that time, all the electro refined cathodes were melted and casted as wire bars. Subsequently, in the 80’s, with the introduction of continuous casting furnaces, it was possible to directly produce wire rod from cathodes. From then on, cathodes quality standards were consistently increased, by the introduction of uniform criteria, among which we can identify ASTM and British Standards as well. Also, producers began to use more demanding internal standards than the existing specifications, in order to differentiate their cathodes as high quality products among customers. Today the physical aspect of cathodes, including nodules, cracks, sulfates, or others, is the first element used by end customers to assess their quality. This paper aims to show a brief vision of the evolution of quality specifications for products used to manufacture copper wire. INTRODUCTION From the beginning of refined copper production for industrial purposes, mandatory minimum quality conditions were established. These quality conditions were used as the main element to determine prices and discounts of the respective sales contracts. Reviewing the copper development history, we can appreciate that its quality requirements had been constantly evolved, so that currently refined copper has an extremely high quality standard, that allows its direct use in the production of ultra-thin cables and other products applied in the industry. In each stage, refined copper production has fostered the development of technology used in their treatment. Similarly, cathode processing technology has been evolving to minimize treatment costs in order to generate a wire rod for several uses, ranging from power cables to super conductors. In this sense, to the already known type of fusion processes of the Southwire or Asarco type (capacities over 80 kt / year), wire rod production processes of the Upcast or Rautomead type (capacities between 20-50k t / year) have been added. They immediately deliver oxygen-free wire rods. In both cases, we can conclude that the clients' requirement had evolved from a chemical criteria focus, to considering more subjective aspects, such as visual control as the first stage of inspection.

Jan 1, 2019

By S. D. A. Hannot, H. Knapp

"High pressure grinding rolls (HPGR’s) are an energy efficient solution for comminution of industrial minerals and metal ores. The technology is successfully applied in an expanding field of applications throughout the minerals industry. HPGR’s compress and grind the particle bed in the operating gap between two counter-rotating rolls. The equipment provides a high capacity, low energy alternative for applications with conventional tertiary and quaternary crushing and grinding, with size reduction reaching from 100mm down to 25 microns product. In this process, maintaining a controlled and evenly distributed operating pressure between the rolls is very important. Due to feed segregation, the pressure distribution along the roll’s length can become uneven, resulting in a coarser product. This paper will show that the best approach to compensate and adapt for the uneven pressure is to allow the rolls to skew relative to each other. Coarser products are also caused by an inadequate pressure distribution: the much-discussed edge effect. To minimise the consequence of the edge effect, an optimised ratio for the roll length to diameter will be calculated. Furthermore, the design philosophy behind a cheek plate will be detailed. This cheek plate is used to retain the material between the rolls, reducing the edge effect while still allowing roll skew. Together these design considerations help optimise HPGR’s performance.INTRODUCTION Initially developed for the cement industry during the energy crisis in the 1980’s , high pressure grinding has been an accepted technology for many years. It has been successfully implemented throughout the minerals industry, with applications in base and precious metals, as well as industrial minerals processing. The comminution process relies mainly on size reduction through to compression and inter-particle crushing in a particle bed in the operating gap between two counter-rotating rolls. The equipment typically has a high unit capacity and low energy consumption, and is increasingly used as an alternative to conventional tertiary and quaternary crushing and grinding, in particle size ranges reaching from 100mm down to 25 microns. It can be applied to moist ores and dry material, in open circuit arrangement or in a closed circuit with dry or wet classification (screening, air classification)."

Jan 1, 2019

By John G. Henning

Low quality rock is encountered in many manifestations in underground hard rock mines, ranging from weak and poorly consolidated rock to highly altered or foliated rock. Lateral mine developments driven in low quality rock pose on-going challenges to a mine operator, as ground stability issues, such as caving of under-supported ground, drift closure due to surface deformation or buckling processes, and degradation of exposed rock surfaces are a persistent concern. For many operators, ground support design is an iterative process, as support practices are refined with time. Using case studies from a variety of underground hard rock mines, this paper reviews techniques for the classification of low range rockmasses and examines the rationale and effectiveness of adopted ground support systems.

Oct 1, 2010

By A. Suzue, T. H. Okabe, Y. Taninouchi

Methods for the physical separation and enrichment of platinum group metals (PGMs) from autocatalyst scrap were studied in order to develop an environmentally friendly and efficient recycling process. In general, an autocatalyst has a honeycomb-structured ceramic substrate that is coated with a catalyst layer containing platinum (Pt), palladium (Pd), and rhodium (Rh). Therefore, physical separation of the PGM-containing catalyst layer directly from the ceramic substrate is favorable for upgrading the autocatalyst scrap. In this paper, the authors present a scrap-upgrade process consisting of electroless iron plating and magnetic separation techniques. Iron was plated on the surface of a catalyst sample used to represent an autocatalyst, which was then crushed and magnetically separated. The Pd in the catalyst sample was successfully extracted and concentrated in the magnetic powder. Under certain conditions, the process increased the Pd concentration by a factor of 4 and recovered 89% of the Pd in the autocatalyst sample.

Jan 1, 2014

By C. R. Edwards, D. R. G. Watt

"Equity Silver Mines Ltd. a member of the Placer Development group of companies operates Canada's largest silver mine near Houston in north-central British Columbia. Initially, the silver-gold-copper flotation concentrate contained excessive levels of antimony and arsenic, so a leach process was installed to remove undesirable metals and provide improved smelter terms for the leached concentrate. The leach plant which has been fully described elsewhere (1, 2, 3), was forced by deteriorating process economics to shut down in April 1984. Equipment was mothballed and alternate uses sought.The Endako Mines Division of Placer Development Limited, located some 150 kilometres east of the Equity mine site, shut down its molybdenite mining and milling facilities in the spring of 1982. Endako has continued to produce molybdic oxide (molybdenum trioxide or MTO) via intermittent roaster runs, and also a high purity, lubricant grade molybdenum disulfide in the Ultrapure Plant. With the steel industry in the doldrums, molybdenum chemicals present an alternate and growing potential for molybdenum sales. In 1982 Placer Development began testing this market. Molybdenum chemicals were produced in the United States on a toll basis using Endako MTO as process feed. The transfer of this production to Canada was being considered when Equity's leach plant shut down, and it was noted that most of the equipment and skills necessary could be provided by the leach plant. See Figure 1.A careful investigation of process requirements was completed by engineering and production staff at Equity and Endako. A provisional capital and operating cost estimate was made, and it was decided to perform a test run during July 1984. There were strong reasons to proceed with this project. A positive cash flow was expected for both Endako and Equity. Endako would have product to continue to expand in the molybdenum chemicals market with the added selling point that now the complete production process would be under direct control of Placer Development companies. Equity would further benefit since a portion of the leach plant would continue in operation thus maintaining and exercising our hydrometallurgical engineering and operating skills. Finally, Equity would have a base from which to search out other processes adaptable to the idled leach plant equipment."

Jan 1, 1986

By F. Urekar, R. B. Pankhurst

"Air spaces and air gaps in an explosives column are known to allow greater distribution and cushioning of explosive energy from the rock mass. This energy distribution is enhanced if the explosives ' gases can be confined in the borehole for as long as possible by plugging and stemming above the air space.Power Plug is an inflatable plug which can seal a borehole at any point to separate the stemming from an air gap and explosive toe load.IntroductionThis paper will discussion-going work by C-I -L Inc. and operators of two open pit mines to study the results of using Power Plugs:I. Pit wall stability - the authors have found the Power Plug effective for wall control blasting in open pit mines.2. Selective mining of coal seams - the authors work shows the Power Plug allows mining selective coal seams by predrilling underseam waste wedges.Pit Wall StabilityWall stability in an open pit mine is essential for safety. Good wall stability can be achieved with wall control blasting techniques which cushion the effect s of the explosives charge by decoupling the charges from the borehole wall. The usual method of decoupling a charge in a large-diameter rotary borehole is to load the explosives in tubes (Fig .I) . We now believe the air deck system is effective in sea ling a borehole above the explosive charge to create an air deck within the borehole which will cushion the blast.In a linear decoupled charge, an air annulus surrounds the explosives charge and cushions the effects of detonation genera ted gases on the pit wall. In an air deck, i.e. with the hole plugged at the collar, the gases genera ted by an explosive toe load are sealed in the empty borehole column. After a period of time, these trapped gases produce radial cracking between holes along the entire length of the borehole.It is common practice to employ de coupled explosive charge columns in the borehole to limit blast damage to surrounding rock. The exact mechanism of energy transfer in such blasts, however, is not well understood. Interruption of the continuous explosive column in a borehole by means of stemming, or air decks, may also be viewed as another form of decoupled blast. Decoupling of the explosive charge from the borehole wall affects both explosive energy release and explosion pressure developed in the borehole."

Jan 1, 1988

By A. J. Hyett, R. D. Reichert

"A laboratory and field research program was conducted to investigate the major factors influencing bond capacity of grouted cable bolts. The results indicate that cable bolt capacity most critically depends on the grout uniaxial compressive strength (UCS), the radial confinement, and the embedment length.In the laboratory &apos;split-pipe&apos; tests were conducted using P VC, aluminum and steel pipes to provide radial confinement, and field test sites were chosen in granite, limestone and shale rock masses. For both datasets higher capacities were obtained under conditions of higher radial confinement. A correlation between the two was obtained through a comparison of the radial wall stiffness of the laboratory pipes with that of the field boreholes as measured using a high pressure dilatometer. Cable bolt capacity was found to increase with embedment length though not in direct proportionality.The use of low water cement ratio grouts (<0.40) can increase cable bolt capacities by 50% to 75%. This effect is maximized under conditions of high radial confinement. However, the use of super thick grout paste (0.30 and less) may be both impractical and undesirable, first because of their limited pumpability and second because of their inconsistency in strength. Grouts with a water cement ratio of between 0.35 and 0.40 are recommended for practical cable bolt applications."

Jan 1, 1992

By Marc Bétournay

This article examines how fuel cell technology and related power distribution system fits within mine operating requirements. Considerations for improvement of power plant architecture and functions to yield production advantages are presented. Improvements to conventional mining approaches are also discussed.

May 1, 2007

By M. R. P. Snow

"This paper outlines geotechnical conditions that commonly exist in underground, hardrock mines and the challenges posed for ground-support steel, specifically rockbolts, used in these environments. A model is proposed whereby the in-situ stress and rock-mass classifications (based on Bieniawski’s rock mass rating) form the basis of determining the desired steel properties of the rockbolts used. Based on the ASTM F432 bolting specification, recommended minimum steel properties are defined for three ranges of in-situ stress levels, each with their own six ranges of RMR values. Heat treatment for the steel can be specified once these minimum steel properties are known.RÉSUMÉ Le présent article décrit les conditions géotechniques qui existent fréquemment dans les mines souterraines de roches dures et les défis que cela pose pour le soutien de terrain en acier, plus spécifiquement les boulons d’ancrage utilisés dans ces environnements. Un modèle est proposé dans lequel les contraintes in situ et les classifications de la masse rocheuse (selon la classification de la masse rocheuse de Bieniawski) servent de base pour la détermination des propriétés désirées pour l’acier des boulons d’ancrage utilisés. En se basant sur les spécifications de boulonnage de l’ASTM F432, les propriétés minimales recommandées pour l’acier sont définies pour trois plages de niveaux de contraintes in situ, chacune avec sa propre plage de six valeurs de classification de la masse rocheuse (RMR). Un traitement thermique pour l’acier peut être spécifié une fois que ces propriétés minimales pour l’acier sont connues."

Jan 1, 2016

By K. Mayhew, A. Lossin, H. Salomon-de-Friedberg

"The proportion of arsenic-bearing copper concentrates that supply the copper industry is on the increase. The current strategy of miners and smelters to blend feeds to reduce average arsenic levels is rapidly becoming unsustainable as more concentrates with even higher arsenic levels enter the marketplace. In addition, the capability of smelters to manage increasing arsenic levels to more stringent and restrictive environmental standards is limited by available process technologies.CESL Cu-As Technology is a viable technical and economic alternative to traditional smelting. It offers the advantage of simultaneous leaching and precipitation of the arsenic in a single processing step while achieving high copper extractions. The process has been piloted in six separate, fully-integrated pilot campaigns for feeds ranging from ~1% to 12% arsenic in concentration. This paper will focus on the behaviour of arsenic in CESL’s leaching/precipitation step and operational factors that influence it, and on the chemical and physical characteristics of the subsequent iron-arsenic residue that represents today’s best available technology from a long-term sustainable (capital/operating costs, metal recovery, safety, environmental) perspective.The examples provided will demonstrate copper extractions approaching 99% and arsenic deportment to residue of 99%. Instantaneous settling rates of the residue were measured at 15+ m/hr. Data from subsequent short and long-term stability testing of the residue confidently support the view that the scorodite-bearing residues from the process will be stable and provide an acceptable arsenic management practice. The technology offers increased revenue and environmental certainty for miners, smelters & refiners to support the development of metallurgically challenged copper-arsenic deposits. Furthermore, results will be presented demonstrating the technology’s ability to successfully incorporate hazardous arsenic containing smelter by-products such as dust into the process feed and simultaneously extract copper value while fixing the arsenic in a stable residue."

Jan 1, 2016

By A. Kraly, M. Complojer, P. Paschen, K. Gamweger, H. Antrekowitsch

Increasing quality of aluminium alloys and continuous optimization of the production process leads to an improvement of the gas purging systems. The application of porous plugs for the treatment of liquid aluminum is nowadays not widely used in the aluminium industry especially in Europe. The Department of Nonferrous Metallurgy and the Christian Doppler Laboratory of Secondary Metallurgy of Nonferrous Metals intensified the research and development of refining and alloying processes by gas treatment during the last years. CFD-modeling supports these experiments, which should lead to lower hydrogen content, lower suspended particles and a better distribution of alloying elements in the melt. Different parameters such as temperature, bubble size, gas amount and which kind of gas is used influence the quality of the products.

Jan 1, 2006

By T. R. Eger

The Load-Haul-Dump (LHD) vehicle is a trackless, free-steered vehicle used in underground hardrock mining to move large quantities of ore/rock to haulage trucks, ore dump locations, or crushing stations. The purpose of this paper is to show, through case study examples, how principles of human factors can be applied to improve the overall design of the LHD vehicle to enhance line-of-sight (LOS), improve posture and decrease whole-body vibration exposure (WBV). Vehicle modifications (larger cab windows, lower engine profile, smaller buckets, angled radiator profile) can lead to improved line-of-sight. The use of secondary viewing devices, such as cameras, can also improve line-of-sight and allow the operator to adopt a more neutral sitting posture. Seating systems that are suited to the underground mining environment can result in vibration attenuation and less vibration transmitted to the LHD operator. The connection between vehicle design, line-of-sight and driving posture needs to be considered in order to continue to improve the design of the LHD and enable the operator to work in a neutral posture with minimal vibration exposure. Changes leading to improved line-of-sight, vibration reduction, and a neutral sitting posture will lead to fewer LOS related accidents and decreased risk factors for musculoskeletal injury.

Aug 1, 2013

By Lindsay A. Robertson

The long term management of acid generating tailings at mine closure is a common issue, however, management of ARD is significantly impacted by local conditions, including climate. Acid generating tailings, over time, will produce acid rock drainage (ARD) if left exposed to water and air, which both contribute to the sulphide oxidation process. The long term closure of tailings storage areas is a concern from both environmental and engineering perspectives, with long term acid generation and dam stability the main risks. Several approaches can be taken to minimize ARD from tailings facilities using cover systems. Three tailings facility cover case histories, in areas of net positive water balances, were investigated using unsaturated flow modelling software to determine the long term potential for limiting ARD by increasing saturation of the tailings and decreasing oxygen ingress. Each case study demonstrates the importance of integrating the tailings dam engineering into tailings cover closure design. Model predictions are compared to measured saturation levels to assess the accuracy of the calculations.

May 1, 2011

By D. Milne

Laser profilometers exist for obtaining very accurate two and three dimensional profiles of joint surfaces. The application of this technology is not commonly applied to the collection of field data on discontinuity surface roughness. Rugged and portable field devices are not commonly used and the value of the possible field data that can be collected has not been well recognised. This paper reviews commonly used field techniques for assessing discontinuity roughness, discusses the value of this data and presents a new laser profilometer design for field application.

May 1, 2009

By J. Bhattacharya, S. K. Mukhopadhyay, S. K. Pal

"While time and again many authors have categorically stressed the restoration of the environment, very little effort has been made in the mineral industry to develop the economy of environmental control. There are many abatement procedures that search a maze of variants. Among them pricing environmental damage seems to be more logical and easily implementable.IntroductionMining as an operation has a severe impact on the Earth&apos;s natural resources. While economical environment control is much sought after, solutions are often varied and complex, and can differ in the problems of single or multiple mine sites.Determination of Optimum use LevelsIn “mining environmental control"" it is required to strike a balance to find optimum use levels. The solution is to find where the welfare benefits equal the cost involved to curb the degree of environmental damage (Fig . I) . In the mining industries this can be done by modifying the production/extraction process itself. For most pollutants, the marginal costs of control will exceed the benefits from further reduction of damage long before the zero pollution damage point is reached (Fig. I). From an economic perspective the optimal alteration of environment by mining would occur at z; pollution continues to be caused by ""zy"" control units, but it would be inefficient to pursue the redemption efforts further because the marginal cost involved would exceed marginal welfare benefits."

Jan 1, 1992