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By I. Mc Dougall

Finite element models were generated of two submerged arc furnaces of different geometries. A 48MW circular furnace and a 68MW 6-in-line rectangular furnace were studied. The electrodes, raw material, slag and molten metal were included in the model. ANSYS/Multiphysics was used to predict the current density distribution in the electrodes, raw material, slag and molten metal as a result of the three phase AC current. The effect of the electrode immersion on the current path was studied. The ?proximity effect? caused a pronounced asymmetry in the electrode currents in the circular furnace, whilst the electrode currents in the rectangular furnace exhibited radial symmetry. The current distribution in the melt in both furnaces indicated that the bulk of the current flows between phases. The current density is greatest between electrodes. Results were compared to qualitatively similar published work, operating experience and results of furnace dig-outs.

Jan 1, 2007

In this study, the effects of slag compositions, slag amount, temperature, and carbon content of steel on the manganese and phosphorus distribution ratios during converter steelmaking were analysed using the classical regular solution theory, and industrial tests were performed using two 80 t top-and-bottom combined blown converters (duplex melting process). The results indicate that the slag amount, temperature, and carbon content in steel are the main factors affecting the manganese yield when converter slag compositions remain constant. The FeO content of the slag has a strong impact on the manganese distribution ratio, while the slag basicity and MgO content have no obvious effect. The calculations and experimental results show that the phosphorus distribution ratio increases sharply with increasing slag basicity R, but then decreases with the increase of MgO and MnO contents in the slag. The final slag in converter steelmaking should have the following characteristics: 3.5 < R < 4.5, 15% < (FeO) < 20%, and 6% < (MgO) < 8%. The slag amount should be controlled appropriately at the same time. The results of this investigation would be useful in deciding on the application of manganese ore in alloying and identifying the slagging regime in converter steelmaking.

Jan 1, 2014

By C. E. Hales

In an effort to improve efficiencies and reduce costs, AngloGold has embarked on a process to develop and deliver consistent, high quality, tailings based support or construction products to stopes and tunnels on request. A three-phase approach of product conceptualisation, design and delivery has been adopted. To date a substantial amount of laboratory development has taken place with promising results, indicating that the project aims are achievable. Dans un effort pour améliorer le rendement et réduire les coûts, AngloGold s’est embarqué dans une opération qui vise à développer et fournir aux chantiers d’extraction et tunnels, sur demande, des produits de construction ou de support basés sur rejets qui sont réguliers et de haute qualité. Une méthode à trois volets a été adoptée : conception, création et livraison. A ce jour, un développement important en laboratoire s’est produit, avec des résultats pleins de promesses, qui semblent indiquer que les buts du projet peuvent être atteints. In der Bemühung, die Effizienz zu steigern und Kosten zu verringern, hat AngloGold begonnen ein Verfahren zu entwickeln welches auf Anfrage konsistent hochqualitative auf Haufwerk basierender Unterstützung oder Bauprodukte für Abbaustellen und Tunnels entwickelt und liefert Eine Dreiphasenplan zur Produktkonzeptualisierung, Design und Lieferung wurde adoptiert. Bis jetzt hat eine substantielle Anzahl an Laborentwicklung mit vielversprechenden Resultaten stattgefunden und aufgezeigt, daß die Projektziele erreichbar sind.

Jan 1, 2003

By A. Golshani, M. Oda, K. Suzuki, T. Takemura

Anisotropic behaviours of OhshimaOshima granite were investigated by carrying out uniaxial compression tests, together with observations of microcracks under an optical microscope. The elastic modulus tensor of Oshima granite at 10 per cent strength,E10, were calculated using theoretically formulation of elastic modulus tensor in terms of the second-rank crack tensor for pre-existing open microcracks. Furthermore, with the assumption of orthorhombic elasticity, the nine moduli of Oshima granite E10were determined by uniaxial compression test. Twenty-onemoduli of samples, calculated without assuming any symmetry, also showed orthorhombic features. Direction of the symmetry axes agreed well with the orientation of preexisting cracks. Comparison of crack tensor-based formulation results with the experimentally determined one show that the anisotropy of elasticity of Oshima granite is caused by pre-existing open microcracks, not by pre-existing healed microcracks and also crack tensor formulation can be used, as a first-order approximation at least, to describe the anisotropy of Oshima granite induced by pre-existing open microcracks. ZUSAMMENFASSUNG: Das anisotrope Verhalten des Oshima-Granits wurde mit Hilfe voneinachsigen Kompressionstests und durch die Betrachtung von Mikrorissen unter einem optischenLichtmikroskop untersucht. Das Elastizitätsmodul von Oshima-Granit bei 10 Prozent Kraft E10wurde berechnet, indem man die Formulierung des Elastizitätsmodultensors, ausgedrückt alsRisstensor zweiter Ordnung theoretisch auf bereits existierende Mikrorisse angewandt hat.Außerdem wurden die neun Module des Oshima-Granits unter der Annahme orthorhombischerElastizität E10mit einem einachsigen Kompressionstest bestimmt. Einundzwanzig Stichproben,die ohne die Annahme irgendeiner Symmetrie genommen wurden, zeigten ebenfallsorthorhombische Merkmale. Die Richtung der Symmetrieachsen stimmte mit der Orientierungbereits vorhandener Risse überein. Der Vergleich der Ergebnisse der auf dem Risstensorbasierenden Formulierung mit der experimentell bestimmten Formulierung zeigt, dass dieAnisotropie der Elastizität von Oshima-Granit von bereits vorhandenen offenen Mikrorissenverursacht wird, und nicht von vorhandenen vernarbten Mikrorissen, und dass dieRisstensorformulierung auch zumindest für eine Annäherung erster Ordnung benutzt werdenkann, um die durch vorhandene offene Mikrorisse induzierte Anisotropie des Oshima-Granits zubeschreiben. RESUME: Les comportements anisotropes du granit d’Oshima ont été étudiés en réalisant destests de compression simple, et en observant les microfissures au microscope optique. Le tenseurdu module d’élasticité du granit d’Oshima sous une résistance de 10 pourcents, E10, a été calculéen se servant de la formule théorique du tenseur de module d’élasticité basé sur le tenseur defissures de second ordre des microfissures ouvertes préexistantes. En outre, sur base del’hypothèse de l’élasticité orthorhombique, les neuf modules du granit d’Oshima ont étédéterminés par des tests de compression simple. Vingt et un modules d’échantillons, calculés endehors de toute hypothèse de symétrie, ont aussi montré des caractéristiques orthorhombiques. Ladirection des axes de symétrie correspondait bien à l’orientation des fissures préexistantes. Lacomparaison des résultats de la formule basée sur le tenseur de fissures avec les résultatsdéterminés expérimentalement montrent que l’anisotropie de l’élasticité du granit d’Oshimaprovient des microfissures ouvertes préexistantes, et non de microfissures préexistantes referméeset que la formule du tenseur de fissures peut servir, au moins comme première approximation, àdécrire l’anisotropie du granit d’Oshima marqué par des microfissures ouvertes préexistantes.

Jan 1, 2003

By L. Munsamy, B. J. Madden

OpenRisk, an open cast risk rating system, takes into account relative differences in the importance of hazards, as experienced on each mine as a result of different combinations of geotechnical factors and mining conditions. The system is based on critical geotechnical and operational parameters that have been identified by mining personnel and rock engineers. The primary advantage of this risk rating system is that all the strip mines would use an identical system, which enables the user to compare their risk to the risk at neighbouring mines and/or other open cast mines. The system can be adjusted to meet local, mine specific requirements. This system has been made practical and easy to use. Therefore, this tool can be used by personnel from other disciplines not directly related to rock engineering. OpenRisk system has been in operation at nine Anglo Coal and other open cast mines. It adequately detects areas of high risk and generates adequate remedial solutions to reduce the risks. Awareness of the personnel has been higher at the sites that use OpenRisk. The proactive approach of OpenRisk ensures that all personnel are aware of risks in the pits and how to deal with potential risky areas.

Jan 1, 2006

By Mike McWha

Drivers to increasing RM use ?Compliance issues ?Section 12 JSE Listing Rules ?Canadian NI 43-101 ?Sarbanes Oxley ?Shortage of African ore reference materials ?Poor perceptions about quality of some local RM?s

Jan 1, 2005

By M. Sanchez, C. Morales, J. Palacios

The slag produced in the Peirce Smith converters at the Ilo smelter of Southern Peru Copper Corporation has shown a wide range of magnetite content, which introduces an additional problem in the smelting units due to materials? recirculation. However, the operation data analysis and the application of thermodynamic concepts have made it possible to produce slag with magnetite content between 18 and 20%. The results have suggested that matte grade enhances magnetite formation while silica controls its precipitation, and they are also influenced by the increasing temperature of the slag. Thus, in order to obtain the required magnetite content in the slag, matte grade is gradually enriched in equilibrium with slag containing from 25 to 32% silica.

Jan 1, 2004

By A. J. Van Der Merwe, J. F. Erasmus

One of the valuation approaches applied to Advanced Exploration Areas and Pre-Development Projects is the so-called ?in situ Mineralization Method? or the ?Yardstick Method?. This method is based on the concept of a known undeveloped Mineral Resource being worth a certain fraction (the ?Yardstick?) of the contained commodity value (?metal in ground?), using commodity prices ruling at the date of valuation. The Yardstick value is derived usually from an average market-based figure obtained from an analysis of recent transactions and is expressed as a monetary value per ounce or per tonne. It maybe modified to accommodate the quality (e.g. grade) and category (e.g. confidence level) of the Mineral Resource/Reserve involved and the time, effort and expenditure expected to be involved in bringing the project to fruition. Some eighteen recent and relevant transactions were analysed, allowing the following general conclusions to be reached: ? a Yardstick with which to value undeveloped PGE mineral resources is likely to range between 0.5% and 2.5% of the in-ground contained metal value ? the expected method of mining (especially with regard to mining costs) and the grade of the mineralization both have a strong influence on the Yardstick ? the status (classification) of the Mineral Resource has some influence on the Yardstick and ? the ruling price of platinum and the regional location of the deposit appear to have insignificant influences on the Yardstick.

Jan 1, 2006

By L. Holappa

Ferroalloy production is an energy-intensive industrial sector with significant CO2 emissions. In this paper the current situation in ferroalloy processes is discussed from the standpoint of global environmental issues, trends and development. Progress and data of ferroalloys production are frequently compared with the steel industry, which is a closely related sector and the main user of ferroalloys. Emission factors of processes and electricity production are examined as well as possibilities and future scenarios of how to diminish CO2 emissions. As a part of this study a questionnaire was submitted to experts in the field of ferroalloys worldwide to survey opinions on the ferroalloy industry today and in the near future (2020). Eighteen questions concerning raw materials, energy, environmental aspects, by-products and economic aspects were responded to by seventeen experts, the answers were analysed and conclusions were drawn. Keywords Ferroalloys, energy, CO2 emissions, electricity, sustainability, questionnaire.

Jan 1, 2010

By Y. Mitani, F. Vallier, T. Esaki

Shear-flow coupling tests are conducted using an original apparatus, and a shear-flow coupling model using Geographic Information System (GIS) is developed in order to evaluate shear-flow coupling properties of a rock joint. Shear-flow coupling tests indicate that the hydraulic conductivity of joint once decreases, and then rapidly increases at the shear displacement near the peak shear stress. The proposed model simulates the test results relatively well. However it indicates that it is difficult to apply the local ‘cubic law’ model in the initial shear stage, in which the change of selective flow path is remarkable. Scher-Fliess-Kopplungsversuche werden mit einem neuartigen Versuchsgerät durchgeführt und mithilfe von Geo-Informationssystemen (GIS) gedeutet, um so ein Modell für die Scher-Fliess-Kopplung in Gebirgstrennflächen zu entwickeln. Die Versuche zeigen, dass die hydraulische Leitfähigkeit zuerst abnimmt, dann aber schnell wieder zunimmt sobald die maximale Scherfestigkeit erreicht ist. Das vorgestellte Modell bildet die Testergebnisse relativ gut nach. Es zeigt auch, dass es schwierig ist, das lokale Cubic Law im Initialstadium der Scherbeanspruchung anzuwenden, in dem die Variationen selektiver Fliesswege gross ist. Les essaies hydro-mécaniques couplés en cisaillement sont réalisés grâce à un appareil éxperimental prototype et un modèle de couplage hydro-mécanique utilisant le S.I.G (systeme d&apos;information géographique) développé dans le but d&apos;évaluer les propriétés hydro-mécaniques des joint rocheux. Les résultats indiquent que la conductivité hydraulique des joints décroit puis augmente rapidement en se rapprochant du pic de cisaillement. Le modèle proposé simule relativement bien les résultats expérimentaux ; mais indique également qu’il est difficile d’appliquer localement la loi cubique au début du cisaillement où, les changements d’orientation dans le réseau d&apos;écoulement sont considerables.

Jan 1, 2003

By M. J. Papo, A. Muwila

Hercules? is a low nickel austenitic stainless steel developed at Mintek that has a typical composition of 9 wt% Mn, 0.05 wt% C, 2 wt% Ni, 0.25 wt% N and 16.5 wt% Cr. A more corrosion resistant version of Hercules? (Hercules? B) with 0.5 wt% Mo has also been developed. Potentiodynamic tests performed on Hercules? B in a 5 wt% sulphuric acid solution showed it to have improved corrosion resistance comparable to that of AISI 304. The effect of a varying Mn content on the corrosion resistance of Hercules? B has also been investigated and the results discussed in this paper. From the corrosion test results, it is clear that decreasing the Mn content of Hercules? B increased the corrosion rate while increasing it decreased the corrosion rate. KEYWORDS Austenitic stainless steel, %ferrite, molybdenum, manganese, nitrogen, electrochemical corrosion tests, potentiodynamic scans, microstructure, chemical analysis.

Jan 1, 2006

By M. Castelli, C. Scavia, S. Marello, A. Allodi

ABSTRACT – This paper investigates the possibility of interpreting the shear band evolution in hard soils and soft rocks as the result of shear propagation from pre-existing natural defects. Thesis done through the application of the principles of Fracture Mechanics, a Slip-Weakening Model(SWM) being used to simulate the non-linear zone at the tips of the discontinuity. Experimental observations have been carried out on prismatic samples of Beaucaire marl through biaxial compression tests in plane strain conditions. A numerical simulation confirms the validity of the proposed approach. RÉSUMÉ – Cet article présente la possibilité d’interpréter l’évolution des bandes de cisaillement dans les roches tendres et les sols raides comme le résultat de la propagation pour cisaillement à partir d’un défaut préexistant. Le Slip-Weakening Model (SWM) a été employé pour modéliser la zone non linéaire a l’extrémité d’une discontinuité. Nous présentons des observations expérimentaux obtenues à travers des essais de compression en déformation plane sur des échantillons prismatiques de marne. La simulation numérique d’un essai confirme la validité de la méthode proposée. KURZFASSUNG – Die vorliegende Arbeit versucht die Ausbreitung von Scherzonen in(bindigen) Böden und im Lockergestein anhand der Entwicklung von Scherrissen ausgehend vonexistierenden Schwachstellen zu erklären. Die Umsetzung erfolgte mit Hilfe der Bruchmechanik,für die Modellierung der nichtlinearen Zone an den Rissenden wurde ein Slip-Weakening-Modell(SWM) eingesetzt. Es wurden zweiaxiale Druckversuche an prismatischen Probekörpern vonBeaucaire Mergel unter der Bedingung eines ebenen Verzerrungszustandes durchgeführt. Dienumerische Untersuchungen bestätigten die Annahmen der untersuchten Theorie.

Jan 1, 2003

By G. van Aswegen

The geometry and morphology of a set of low-angle fractures around a stope in a deep Witwatersrand gold mine are explained in terms of extension fractures forming under variable conditions of stress. Primary extension fractures (E1) form some distance ahead of an advancing stope along the s1, s2 plane. With stope advance, a couple of these fractures end up in a stress regime conducive to transpressional shear and a secondary set of extension fractures(E2) is formed at a high angle to the primary fractures. i.e. at a low angle to the stope. As the E2 fractures are undermined, they migrate into a stress regime of transtensional shear and a third set of extension fractures (E3) may develop between E2 fractures. These have sigmoidal shapes, being parallel to the E2 fractures at the E2 discontinuity where s3 is negative, and curved through the un-fractured rock between E2 fractures where s3 is positive at the instant of fracturing. The fractures all display fractographic features characteristic of dynamic extension failure with striae indicative of the direction of rupture propagation and the local, instantaneous orientation of s1.

Jan 1, 2012

By A. Varadarajan, M. Hashemi, K. G. Sharma

Quartz mica schist collected from Nathpa-Jhakri Hydropower Project, Himachal Pradesh, North India is tested under triaxial loading using a servo-controlled loading system. Complete stress-strain-volume change behaviour including post peak softening behaviour of the samples, are presented. Strength and deformation parameters are given. Quarz mica schist, der von Nathpa Jhakri Hydropower Projekt, Himachal Pradesh gesammelt wird, wird Nördlich Indien unter triaxial geprüft, der von Gebrauch eines servo kontrollierten Ladesystems beladung. Vollständiges Spannung-Spannung-Band Änderung Verhalten Postens Spitze Erweichung Verhaltens der Proben, wird überreicht. Kraft und Verformung Parameter werden gegeben. Mica à quartz schist recueilli du Projet de Hydropower de Nathpa Jhakri, Himachal Pradesh, l&apos;Inde du nord est essayé sous l&apos;utilisation de chargement de triaxial un système chargeant servo réglé. La tension complète-la tension-comportement de changement de volume y compris la poste sommet amollir le comportement des échantillons, sont présenté. Les paramètres de force et déformation sont donnés.

Jan 1, 2003

By J. M. Font, R. G. Reddy

Jan 1, 2004

By W. J. Theron

The purpose of the paper is to give an introduction to the concept of fatigue and its causes in the mining industry. By knowing the fundamental role it plays, together with its dynamics, can positively contribute to a mine?s safety management system. The difference between physical and psychological fatigue will be addressed with a possible range of causes that could trigger fatigue. There are two main sources of fatigue: firstly, work-related fatigue which is associated with activities at the workplace; and secondly non-work-related fatigue. The shared responsibility between the employer and employee is also discussed as it involves factors that occur both in and outside the workplace. Employers have the responsibility to manage fatigue through using a risk management approach. Employees have the responsibility to ensure they get enough sleep, take sufficient and regular nutrition, are healthy and physically fit and come to work fresh and alert. The impact of the implementation of a fatigue management plan and procedures has the potential to eliminate employee fatigue or its causes, reduce the likelihood of fatigue occurring in the workplace, and counteract the effects of fatigue when it occurs. Factors considered when implementing a fatigue management system include: extended hours of work, shift work, time of day and work design. Fatigue is one of the major role players (either causal or contributory) when it comes to causes of fatalities in the mining industry. Our main challenge in identifying whether fatigue played a role is the fact that it cannot be tested in post-mortems like drug or alcohol abuse. It is an aspect worth understanding and getting an organization sensitive to managing it properly to benefit both organizational as well as employee needs. Keywords Signs of fatigue: Causes of fatigue, circadian rhythms, the fatigue equation, fatigue management, fatigue affecting safety, fatigue fighting tips, lifestyle suggestions.

Jan 1, 2011

By S. L. George

The semi-solid metal casting process results in a unique solidification path. The microstructural features that were identified during the characterization of the as-cast microstructure, were used as evidence of the process history in order to determine the solidification path followed during the evolution of the microstructure. The morphology of the grains was characterized using SEM and the extent and distribution of the elemental segregation within the grain structure was analysed using EDS. Keywords Semi-solid casting, solidification path, segregation.

Jan 1, 2011

Cutting strong rock with a drag bit assisted by high-pressure water jets By M. HOOD. B.Sc. Hons. (Min. Eng.). B.Sc. (Mech. Eng.). A.M.I.M.M. (Visitor) Experiments are described that led to the discovery that coherent high-pressure water jets directed immediately ahead of drag bits while they are cutting strong rock reduce the magnitudes of the forces on the bits significantly. Tests were carried out to assess the effects of the pressure of the water jets on bit-cutting performance. The pressure was varied between 10 MPa and 50 MPa, the water flow rate being a constant 30 I/min. Over this pressure range, the force on the bit was reduced to the extent that the depth of cut of the bit was at least doubled with the point of impingement of the jets optimized. Forces on the bit were found to be particularly sensitive to the point of impingement of the water jets relative to the bit. The optimum configuration was found to be with two jets, one directed towards each corner of the bit and impinging on the rock approximately 2 mm ahead of the leading edge of the bit. Experiments in which a drag bit and high-pressure water jets were used to cut strong abrasive quartzite in the underground mining situation have demonstrated a potential increase of up to five times in the average depth of cut due to reduction of the forces on the bit. The results from the underground tests indicate that the life of the bit is improved significantly - by a factor of approximately two - when highpressure water jets are used.

Jan 11, 1976

By C. L. E. Swartz, I. J. Barker, J. H. Schubert

A dynamic simulator of the leaching and adsorption cascades of a gold plant was developed and used to compare the effect of various disturbances on the overall efficiency of the plant. These comparisons show which disturbances most critically need to be controlled to optimize plant performance. The simulator was based on an existing gold plant. Dynamic and steady-state data were collected on the plant and were used in the modeling of the process. Simple dual-rate models are used to describe the leaching and adsorption processes. Mole-balances of various species take into account the changes of concentrations in the leach, and also the movement of pulp and carbon up and down the adsorption cascade. Fluctuations in the flow rate, density, and cyanide concentration of the feed to the leach have a negative effect on the efficiency of the leach, while carbon attrition was found to be an important factor in decreasing the efficiency of the carbon-in-pulp (GIP) section. Badly regulated transfers contribute towards the decreased efficiency of the GIP section, but overflows and carbon leakage have only a limited long-term effect. Various carbon profiles and transfer schemes were studied, and the results indicated that a slightly heavier loading at the bottom of the cascade is beneficial, while the type of transfer is relatively unimportant.

Jan 1, 1993

By J. B. A. Solar Menéndez, M. A. Martínez Fidalgo, L. A. Alvarez-Santullano

1. ANTECEDENTS This present communication refers to the results of the research project entitled "Training in the correct use of chemical oxygen self rescue apparatus and also an analysis of apparatus autonomy", carried out under the auspices of the Specific Collaboration Agreement signed between the Industry Council of the Principality of Asturias (Spain) and INSALUD (National Silicosis Institute, Spain). The antecedents of this project lie in work undertaken by the National Silicosis Institute aimed at optimising efficiency in the use of chemical oxygen self rescuers through improvements in worker training. To be precise, by means of Agreements drawn up between the above-mentioned parties, a simulator was designed and incorporated as the basis of a training station within the " Fundación Barredo" of the Industry Council of the Principality of Asturias. This has been operative since the year 2001 and, up to the present, 2300 Asturian coal mine workers have been trained there. What prompted this activity was the observation of various errors in the use of the self rescuers, deriving from their innate characteristics, especially with respect to the sensation of discomfort - the high temperature and humidity of the breathed oxygen, resistance and inconvenience - and limited autonomy. It was precisely this insight that, in critical situations, lack of familiarity with the conditions of discomfort likely to be experienced during the evacuation process might lead to rejection of the equipment, with fatal consequences, that has justified the setting up of this training and simulation centre. The centre is able to provide all mine workers with the necessary training, and experience of the characteristic sensations experienced when using such equipment (Fig.. 1).

Jan 1, 2003