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By S. Pathak, B. Nilsen

Abstract: In recent years, probabilistic approach with the calculation of probability of failure instead of a factor of safety against failure is emerging in practice. The main objective of the paper is to discuss a probabilistic approach in rock slope stability analysis for Himalayan conditions. Due to the fragile geology brought about by the tectonic movements along the hill slopes, dramatic variations of the topography and intensive surface runoff during every monsoon season, serious slope failures occur frequently in Himalayan region. Slope failures have also been triggered by seismic activities. The probabilistic approach is applied to stability analysis for a road cut along the Desander back slope of the Kali Gandaki hydropower project in Nepal. It is concluded that the probability approach offers a more accurate grasp of the actual condition than any factor of safety. Zusammenfassung: In den letzten Jahren ist es mehr gewöhnlich geworden, ein stochastisches Verfahren und eine Berechnung von der Wahrscheinlichkeit eines Zusammenbruchs statt einer Berechnung von Sicherheitsfaktoren zu verwenden. Das Hauptziel dieses Artikels ist das stochastische Verfahren in Stabilitätsanalyse von Gebirghängen, welches an Himalayische Verhältnisse angewandt worden ist, zu diskutieren. Wegen der spröden Geologie die durch tektonische Bewegungen entstanden ist und den dramatischen topographischen Variationen sowie viel Oberflächenwasser während des Monsuns, kommen in der Region des Himalayas oft mehrere erhebliche Abhangszusammenbrüche vor. Abhangszusammenbruche ist auch von seismische Aktivität ausgelöst worden. Das stochastisches Verfahren ist auch benutzt worden, um die Stabilität von einem Wegschnitt in dem Desander Gebiet von dem Kali Gandaki Wasserwerk-Projekt zu analysieren. Die schlussfolgerung ist, dass die Ergebnisse eines stochastisches Verfahren die wirkliche Verhältnisse eines Abhangs besser beschreibt als der Sicherheitsfaktor. Résumé:- Ces dernières années, une approche probabiliste basée sur le calcul d’une probabilité de cassure au lieu d’un facteur de sécurité préventif d’une cassure est de plus en plus utilisée. L’objectif principal de ce papier est de discuter une approche probabiliste de la stabilité de versants rocheux en himalaya. Due à la fragile géologie causée par les mouvements tectoniques sur les versants de collines, aux dramatiques variations de topographie, ainsi qu’au lessivage intense du relief à chaque mousson, de sérieux glissements de terrains se produisent fréquemment en Himalaya. Les glissements de terrain sont aussi déclenchés par l’activité sismique. Cette approche probabiliste est appliquée aux analyses de stabilité d’une section de route le long du versant arrière Desander du projet « hydropower » du Kali Gandaki au Népal. On en conclut que l’approche probabiliste offre une estimation plus précise des conditions actuelles que n’importe quel facteur de sécurité.

Jan 1, 2003

By J. A. L. Napier

One of the most important characteristics of tabular mine stress analysis is the need to represent the complex evolution of mining face positions and the accompanying induced stress changes in the rock mass. Integration of seismic activity with numerical modelling requires flexible and efficient solution schemes in which both off-reef damage and large-scale fault slip can be effectively represented. A new approach is investigated in which the stope closure and ride variables can be found using a moving least squares estimator. Some advantages of this approach over traditional element-based tessellation schemes are identified. At the same time, shortcomings of this method are noted when the displacement discontinuity variable is approximated by a polynomial shape function. Difficulties and possible solutions to the shape function formulation near excavation edges are discussed. Une des caractéristiques les plus importantes de l’analyse des contraintes minières tabulaires est la nécessité de représenter la complexe évolution des positions du front de taille et des changements concomitants des contraintes occasionnées dans la masse rocheuse. L’intégration de l’activité sismique avec la modélisation numérique requiert des projets souples et efficaces qui permettent la représentation des dommages hors-filon et des glissements de faille à grande échelle. Une approche nouvelle est étudiée qui permet de trouver la fermeture de la taille et les variables de montage en utilisant un estimateur par les moindres carrés mobile. Certains des avantages de cette approche sur les traditionnels projets basés sur une structure en mosaïque sont identifiés. En même temps, les défauts de cette méthode sont notés lorsqu’on calcule la variable de discontinuité du déplacement approximativement par une fonction de forme polynomiale. Les difficultés et solutions possibles à la formulation de la fonction forme près des bords d’excavation sont discutés. Eine der wichtigsten Charaketeristika der taublaren Grubenspannungsanalayse ist die Notwendigkeit, die komplexe Entwicklung der Abbaupositionen und der damit verbundenen induzierten Spannungsänderungen der Gesteinsmasse neu vorzulegen. Die Integration der seismischen Tätigkeit mit einem numerischen Modell erfordert flexible und effiziente Lösungsschemata, in denen sowohl Schäden ausserhalb des Riffs als auch Verwerfungen großen Ausmaßes effektiv dargestellt werden. Ein neuer Vorstoß wird untersucht in welchem die Strossenschliessung und Schneisenvariablen unter Verwendung des Schätzwertes der kleinsten quadratischen Abweichungen (Gaussscher Schätzwert) gefunden werden. Einige Vorteile dieser Annäherung im Vergleich zu der traditionellen Element-basierenden Tessellation sind identifiziert. Gleichzeitig werden Unzulänglichkeiten dieser Methode vermerkt, wenn die Verschiebungsdiskoniuitätsvariable durch eine polynomische Formfunktion angepaßt wird. Schwierigkeiten und mögliche Lösungen zur Formfunktionsformulierung nahe Exkavationsrändern werden besprochen.

Jan 1, 2003

By D. -H. Park, G. -j. Kim, Y. -J. Park, C. -S. Hong, S. -Y. Choo

To evaluate the quantitative tunnel behavior influenced by characteristics of discontinuity, this pa-per executes the parametric study using 2 and 3-dimensional DEM analysis. First of all, this study finds that displacement and the stress of shortcrete are proportioned to frequency of joint and rockbolt axial force is adversely proportioned too. Secondly, it is found that the most sensitive in-put parameter used in Barton-Bandis(BB) model is residual friction angle. Finally, when joint sets are encountered at tunnel excavation face, to identify the most critical joint orientation is very crucial for a stability of tunnel. La thèse a pour but d’étudier les influences sur la stabilité du tunnel, au niveau du réseau de la discontinuité et de la valeur de sa nature aquis par le projet récemment exécuté en vue de mener à l’analyse quantitative de cette stabilité, en appliquant chaque différent paramètre comme la fréquence de diaclase, la constante de résistance des modèles de Barton-Bandis(BB) ainsi que la relation entre le sens d’excavation du tunnel et le réseau de diaclase en 3 dimensions. En fait, cette étude nous a montré que la fréquence de diaclase s’accroît proportionnellement au déplacement et à la contrainte du béton projeté. L’angle de friction résiduel s’est montré le plus sensible à la stabilité du tunnel parmi les modèles de BB. Aussi à travers l’analyse à 3 dimensions, il s’est vérifié que si l’angle de pente du groupe de diaclase est horizontal entre l’axe du tunnel et la direction, il donne une influence importante sur le comportement du tunnel. En particulier, l’influence était la plus importante sur un fond rocheux dont la diaclase horizontale est grande. Um das quantitative Verhalten des Tunnels zu bewerten, eroertert dieses Papier eine parametrische Studie mit Hilfe der DEM Analyse. Auch wird hier eine zweidimensionale Analyse von Ver-bindungen verschiedener Frequenzen in der Gesteinsmasse, eine sensitive Analyse von allen der im Barton-Bandis-Modell (BB) genutzten Parameter und eine Dreidimensional-Analyse mit ver-schiedenen dreidimensionalen geometrischen Veteilungen von Verbindungen ausgefuehrt. Erstens: Die Studie findet heraus, dass Vedraengung und Druck im Shortcrete proportional zur Frequenz von Verbindungen und Axialkraft der Steinbolzen antiproportinal ist. Zweitens: Es wird herausge-funden, dass die am meisten Sensitiven der im BB-Modell angewendeten Eingaben die am Ende uebriggebliebenen Reibungswinkel sind. Und schliesslich wird herausgefunden, dass wenn Ver-bindungsteile an der Tunnelaushoelungsoberflaeche ausgemacht werden, fuer die Tunnelstabiltaet die Identifikation der meist kritischen Verbindungsorientierung sehr bedeutungsvoll.

Jan 1, 2003

By C. R. Royal, B. E. Friedland

Energy & Densification Systems (EDS) has developed patented new technology crushing/milling equipment. The EDS Multishaft Mill is a compact vertical mill – utilising high-speed impacts to break down particles with large reduction ratios, low energy consumption and improved liberation. The milling action combines several processes to provide a multitude of output products to satisfy various specifications. Comminution often accounts for more than 60% of the total power consumption on a mine. Two of the key problems to be solved in comminution is to bring down the specific energy required to reduce particle sizes; and to improve liberation or improve the efficiency of the beneficiation and recovery of the required elements. The EDS Mill has shown extensive improvements in both these areas with energy efficiencies up to 75% better than conventional milling equipment and improving liberation beyond the standard beneficiation processes. Conventional comminution equipment requires massive, heavy parts to be moved or rotated, consuming a lot of energy in doing so and not inputting that energy into the breakage of particles. In the EDS Mill, ramping up the relatively small shafts to speed is all that is required. Once at speed, the momentum, together with the minimal amount of constant drive required, means that the energy can be transmitted directly and efficiently into breaking down the particles. The high-speed impacts allow for a shattering effect of the particles and this quickly generates a high ratio of fines. Furthermore, the single impact force breaks particles in a very different manner to conventional compressive force breakage. With compressive force breakage, the particle breaks from point to point. With high-speed impact force breakage, the force tends to migrate through the weakest areas of the particle, which tend to be the mineral boundaries. This, therefore, means that when the particles break, the various minerals are exposed and hence liberated. Keywords: Comminution, high-speed impact, liberation, energy efficiency, novel comminution

Jan 1, 2020

By M. Tangstad, J. D. Steenkamp

In April 2013 a 48 MVA submerged arc furnace producing silicomanganese was excavated in South Africa. Since the high shell temperatures recorded in the tap-hole area resulted in the furnace being switched out for relining, the tap-hole area was excavated systematically. A refractory wear profile of the tap-hole area with affected hearth and sidewall refractory was obtained in elevation. The carbon ramming paste in front of, above, andbelow the tap-hole was worn, as was the SiC with which the tap-hole was built. A clay mushroom formed but was detached from the refractories. Thermodynamic and mass-transfer calculations were conducted to quantify the potential for wear by chemical reaction between refractory and slag and refractory and metal in the tap-hole area. It was found that chemical reaction between refractory and slag or metal could offer only a partial explanation for the wear observed; erosion is expected to contribute significantly to wear.

Jan 1, 2015

By G. Iabichino, M. Cravero, F. Nacci, L. Rinaldi, L. Vigliero

ABSTRACT: The proposed paper is aimed at analysing the failure of a steep cliff slope that, in the past, was exploited for open pit mining operations. A volume of over 400,000m3 of gneissic aplitic rock was involved in the slope failure. An evaluation of possible failure mechanisms is given, based on a structural description of the rock mass, a mechanical characterisation and on computation methods. The block theory and limit equilibrium techniques for sliding and block toppling were applied and a comparison is given with the result obtained by using DEM models. RESUME: Le document proposé vise l’analyse des mécanismes de rupture d’une falaise qui a été intéressée dans le passé par une mine à ciel ouvert. Un volume supérieur à 400.000 m3 de aplite-gneiss a été concerné par la rupture de la falaise. Le document fournit une évaluation des possibles mécanismes de rupture, basée sur une description structurale de l’amas rocheu, une caractérisation mécanique et des méthodes de calcul numérique. L’analyse a été développée à l’aide de la théorie des blocs et de la technique de l’équilibre limite, soit pour le glissement que pour le basculement des blocs, et une comparaison avec le résultat obtenu par application des modèles DEM a été effectuée. ZUSAMMENFASSUNG: Die vorgeschlagene Arbeit zielt darauf ab, den Einsturz einer steilen Felswand zu analysieren, an der in der Vergangenheit eine Mine im Übertageabbau betrieben wurde. Der Einsturz betraf ein Volumen von über 400000 m3 an Gneis und Aplit. In der Arbeit ist eine Einschätzung des möglichen Mechanismus angegeben, der zum Bruch geführt hat, und sie basiert auf einer strukturellen Beschreibung der Felsmasse, einer mechanischen Charakterisierung sowie auf der Anwendung von Berechnungsmethoden. Angewandt wurden die Blocktheorie und die Methode der Gleichgewichtsgrenze für das Abrutschen und Kippen von Blöcken. Darüber hinaus wird ein Vergleich mit den Ergebnissen angestellt, die unter Verwendung von DEM-Modellen erzielt wurden.

Jan 1, 2003

By I. Satola, J. Aromaa

In this work we have reviewed methods to classify corrosivity of ground waters. Weight loss and stress corrosion cracking (SCC) corrosion tests have been done for rebar and steel strand. No clear indication of SCC was found. The application of tensile stress to 85 % of yield strength increased general corrosion rate significantly in very corrosive waters. The effect of corrosion protection on the axial behavior of steel strands was determined by double pipe axial tests with different embedment lengths. The results showed a significant difference on behavior between epoxy-coated steel strands, galvanized steel strands and plain steel strand. Dans la présente étude, nous avons passé en revue des méthodes permettant de classifier la corrosivité des eaux souterraines. Des tests portant sur les pertes de poids et sur la corrosion FCC (la fissuration par corrosion sous contrainte) ont été effectués pour les barres d’armature et les torons. Aucune indication nette de FCC n’a été constatée. L’application d’une contrainte de traction allant jusqu’à 85 % de la limite d’élasticité a accru de manière significative la vitesse générale de corrosion dans les eaux très corrosives. L’effet de la protection contre la corrosion sur le comportement axial des torons en acier a été déterminé au moyen de tests axiaux à double tube avec des longueurs d’enrobage différentes. Les résultats ont mis en évidence une différence significative quant au comportement entre les torons en acier à revêtement époxy, les torons en acier galvanisés et les torons en acier standard. In dieser Arbeit haben wir Methoden geprüft, die korrosive Wirkung des Grundwassers einstufen. Gewichtsverlust- und SCC-Korrosionstests wurden für Stahlstäbe und Drahtlitzen durchgeführt. Es wurden keine sicheren Hinweise auf Spannungsrisskorrosionsbrüche gefunden. Bei Anwendung einer Dehnbelastung von 85 % der Streckspannung bzw.Ergebnisstärke stieg die allgemeine Korrosionsrate in stark korrosivem Wasser deutlich an. Die Wirkung des Korrosionschutzes bei axialem Verhalten von Stahldrahtlitzen wurde durch axiale Tests an Doppelleitungen unterschiedlicher Versenkungslänge determiniert. Die Ergebnisse zeigten im direkten Vergleich von epoxidbeschichteten, galvanisierten und normalen Stahldrahtlitzen beachtliche Unterschiede im Verhalten auf.

Jan 1, 2003

By J. R. Bredell, J. Branehog, C. Coetzee, J. J. van Tonder

A nutating grinding mill, exemplified by the commercial HICOM mill, achieves efficient particle size reduction through the accelerated motion of the material charge within the nutating chamber. This design, characterised by high particle velocities and rapid charge circulation, offers a compact solution compared to tumbling mills. There have been concerns regarding the mechanical reliability of kinetic joints for certain specialised mining applications. Recognising the need to model internal forces in such systems, this study focuses on the uncoupled simulation using multibody dynamics and the discrete element method. The investigation employed a small-scale experimental test mill, referred to as the NuMILL, featuring a cylindrical chamber (140 mm internal diameter, 245 mm height, 6° nutation angle). Instrumented with an array of sensors, the NuMILL provided internal load data for validating the simulations. Experiments were conducted with an empty chamber or filled with charge material. Charge materials included coarse sand or steel pellets with a charge-to-chamber mass ratio of 0.25. The mill speed ranged between 100 to 700 RPM. Multibody dynamics modelled resultant inertial and frictional loads within 5%, while the discrete element method simulated the internal material contact loads with accuracies ranging from 1% to 19%. The combined simulation approach predicted the resultant forces in the critical kinetic joint within a 20% margin. Representing the charge using rigid lumped mass elements was also studied. The presented simulation techniques, validated against experimental data, offer a robust foundation for analysing larger systems, including the industrial-scale HICOM.

Mar 5, 2025

By R. K. W. Merkle, F. A. S. Reyneke, Z. Harris, P. W. J. Delport

The technological advancements in computing power in the last 30 years have enabled the practical visualization of complex geological environments in three-dimensional (3D) space. 3D models and their application in the mining industry are becoming increasingly important, for example, to identify future exploration areas and targets, for mineral assessment and evaluation, and prediction and planning of future drill-holes. However, acquiring borehole data is an expensive practice, with drilling programmes costing mining companies up to billions of dollars each year. Tighter financial constraints on exploration budgets result in more pressure being put on three-dimensional models to accurately identify future target areas. This article aims to evaluate the potential drilling success of simulated greenfield and brownfield exploration using a 3D geological model created of Leeuwpoort tin mine. These simulations investigate the probability of intersecting a mineralized zone of economic interest and evaluate how the probability is affected when the number of drill-holes and distance from a known intersection changes. Furthermore, these simulations attempt to obtain an indication for the minimum number of drill-holes required for a successful exploration campaign at the mine. The investigation also aims to establish a first-pass attempt towards developing a ‘favoured procedure’ for identifying potential exploration targets for tin deposits with geological and geochemical characteristics similar to Leeuwpoort. The results for the ‘favoured procedure’ established are statistically tested using the ‘bootstrapping’ method. By simulating various exploration scenarios, the study also emphasises the importance of predicting successful drilling, which aids in budgeting for drilling programmes as the minimum number of drillholes needed for a specific exploration project can be determined.

Feb 2, 2022

By I. J. Kotzé, R. T. Jones

Conventional PGM matte smelting requires the presence of a certain quantity of base metal sulphides in order to collect the platinum group metals in a molten sulphidic matte phase in the furnace. Furthermore, the quantity of chromium oxide in the feed materials is controlled in order to avoid the build-up of high-melting chromite spinels in the furnace. Mintek has developed a process for smelting difficult PGM-containing feed materials that contain low amounts of sulphur and/or high amounts of chromium oxide. A DC arc furnace is used to provide the appropriate conditions to generate an iron alloy that collects PGMs very effectively, leaving extremely low residual quantities of PGMs in the slag. Various feed materials have been treated successfully in furnace campaigns running at power levels up to 1.5 MW. The longest of these campaigns was run continuously for more than four months, treating more than two thousand tons of materials such as low-grade concentrates, revert tailings, and converter slag. The campaigns demonstrated the robustness and versatility of the process, and proved that it is possible to sustainably produce a PGM-containing alloy and discardable slags containing an average of less than 1.4 g/t of PGMs over the entire campaign. Keywords: DC arc, smelting, furnace, platinum, PGM, revert tailings, converter slag, ConRoast

Jan 1, 2004

By S. Tshikhudo

This paper outlines an investigation into the recovery of saleable fractions of coal from ?as-arising? South Export Plant effluent streams, using Baleen microscreening technology. South Export Plant, a subdivision of BHP Billiton Energy Coal SA (BECSA) Coal Processing, is a two-module plant treating 2000 t/h. The nominally -150 µm coal is untreated and is therefore passed from classifying cyclones to the thickeners for process water recovery. The thickened underflow is pumped into a series of slurry cells for further settling and recovery of supernatant water. The marginal quality, moisture content, and handlebility of this settled material renders it unsuitable for inclusion into saleable products and it is thus stockpiled and trucked to designated pits for disposal. Over the years, stockpiling and trucking has become an overly expensive exercise. In an effort to recover some of this cost, a task team was assigned to investigate less costly options to process slurry across BECSA plants. Various technologies such as froth flotation, sieve bends, and Reflux Classifier were considered, although the results were generally not beneficial ? this could be attributed to weathered/oxidized coal. A decision was made to pursue an alternative approach by testing the suitability of the new ?Baleen Filter?. The concept is to screen out the higher-grade fraction (+50 µm) as saleable product and reject the finer fractions to the slurry ponds. The Baleen Filter was found to effectively screen at an acceptable efficiency between 94% and 99.99%, with a very sharp cut-point (d50 and Ep). The actual yields from the screening results were better than the predicted yields in terms of both mass and energy as predicted from feedstock analysis.

Jan 1, 2014

By A. N. Brown

The Eighteenth International Symposium on the Appli¬cation of Computers and Mathematics in the Mineral Industries was held in London from 26th to 30th March, 1984. The Symposium was organized by the Institution of Mining and Metallurgy under the leadership of Mr M.J. Cahalan, Chairman of the Organizing Committee. The venue chosen was the Royal School of Mines, Imperial College of Science and Technology, in South Kensington. Some 300 delegates from all parts of the world attended, which included a delegation from South Africa that numbered about 20 persons. This extremely successful series of international meet¬ings was begun in 1961 in Tucson, Arizona, and has grown in strength and importance over the years. The arrange¬ment of the symposia is regulated by the International Council for APCOM under the Chairmanship of Professor R.V. Ramani (U.S.A.), the other current members being Professor J. Elbrond (Canada), Dr Thys B. Johnson (U.S.A.), Professor Young C. Kim (U.S.A.), Professor D.G. Krige (R.S.A.), Professor A.J. Lynch (Australia), Professor C.T. Shaw (U.K.), Dr A. Weiss (U.S.A.), and Professor F.L. Wilke (F.R.G.). There is no doubt that the enthusiasm and dedication of this small group of people and the excellent working relationship that exists between them are responsible for the continued success of APCOM meetings.

Jan 1, 1984

By FT Cawood

The latest Draft MPRRB was released for public comment in October 2006. The main purpose of the Bill is to collect royalties at mines developed in terms of new-order mineral rights granted through the MPRDA process. The transition phase stipulated in the MPRDA will be completed by 1 May 2009, on which date mineral royalties will become payable to the state. The royalty rates stated in the MPRRB differ from mineral to mineral and also depend on the degree of refinement. Gold is the subject of this paper, where the royalty rate ranges from 1.5% (for refined gold) to 3% (for unrefined gold) of sales revenue. This royalty is payable regardless of profit, with a maximum 75% relief for loss-making mines. The purpose of this paper is to establish whether or not it would be necessary for gold mines to adjust their mineral reserve statements as a result of this Bill. The methodology is to add the royalty costs stipulated in the MPRRB to the actual quarterly information for the past ten years as reported by the gold-mine members of the COM. The rationale is to investigate the impact this Bill (in its current form) would have had on gold reserves that must be left unmined in the ground because of a higher pay limit. The results of the study point to a significant impact on reserves available for mining with the subsequent shortening of mine lives and retrenchment of workers. Had the MPRRB been effective for the 10 years prior to 1996, it would have resulted in 46 tonnes of gold being sterilised. Stated alternatively, 30 700 workers at COM gold mines alone would have lost their livelihoods.

Jan 1, 2007

By M. B. C. Brandt

Richter magnitudes for seismic events were calibrated for use as a Local magnitude scale in the West Rand (WR), Far West Rand (FWR), and Klerksdorp–Orkney–Stilfontein–Hartebeesfontein (KOSH) gold mining areas. Richter magnitudes are currently calculated from seismograms recorded by local surface cluster networks using tabulated calibration values for Southern California, published in 1958. The Richter (1958) model is incorrect for distances of less than 30 km and should be applied only to crustal earthquakes in regions with similar attenuation properties to those of Southern California. When compared to the South African National Seismograph Network (SANSN), the cluster networks, on average, overestimate seismic event magnitudes by approximately 0.1 of a magnitude unit. A calibrated Local magnitude scale was derived by means of a multiple regression analysis between the Local magnitudes reported by the SANSN and the largest zero-to-peak trace amplitudes measured on the cluster network horizontal seismograms, after modelling the attenuation of the seismic waves as these progress from the epicentre to the station position. Magnitudes reported by individual stations for the same event show a significant scatter around the average magnitude owing to the near-surface amplifications of the seismic waves at the recordings sites. Average magnitude should be estimated using as many magnitudes of individual stations as possible to ensure an accurate estimate. Larger event magnitudes should be compared with those recorded by the SANSN.

Nov 1, 2021

By S. Lohmeier, D. Gallhofer, B. G. Lottermoser

In Southern Africa, historic mining and mineral processing of base metal deposits have almost exclusively focussed on the extraction of major metals, leading to the loss of remaining valuable raw materials into tailings dumps and waste rock piles. At the Namib Pb–Zn mine (Erongo Region, Namibia), historic base metal tailings deposits are present as unreclaimed exposed waste piles. The tailings comprise silt- (fraction A: d50 = 25 to 48 μm) to sand-sized (fraction B: d50 = 86 to 185 μm; fraction C: d50 = 210 to 230 μm) material and contain major concentrations of base metals (Pb av. 1.15 mass%, Zn av. 3.20 mass%), S (av. 9.95 mass%), as well as lower values of other metals (Cu av. 490 μg/g, Cd av. 133 μg/g, Ag av. 22 μg/g), and critical elements like Sb (av. 14.7 μg/g) and In (14.3 μg/g). Former mineral processing only targeted the extraction of galena and sphalerite. As a consequence, qualitative mineralogical composition of the tailings is similar to that of the primary ore. Ca–Fe–Mg(–Mn) carbonates, quartz, micas, chlorite, minor graphite, magnetite, and rare parisite relate to the former host rock and gangue matrix, whereas Fe-rich sphalerite, galena, magnetite, pyrite with minor pyrrhotite, rare arsenopyrite, marcasite, cassiterite, and accessory scheelite are original constituents of the primary ore. Reprocessing of such a material would be challenging, but a mixed Pb–Zn concentrate enriched in Cd and Ag might be obtained. In future, possible reprocessing of Namib tailings and associated disposal of wastes into an appropriately designed repository would not only generate valuable metal commodities, but such activities would also eliminate a major metal pollution source from the local environment.

Sep 9, 2024

By W. Jilowa, C. Nguni, M. Simukoko, C. Nampungwe

The upsurge in cobalt price and demand is propelled by high demand from the electronics and electric vehicle industry. Konkola Copper Mines has cobalt occurring with copper in the ratio 1:10 in ore. The ore is treated in the concentrator and recovered at the smelter as an alloy (Cu 70%, Co 4%–7%, 15% Fe). Subsequent processing of the cobalt alloy is challenging, with very few plants able to treat it, leading to marketing challenges. Konkola Copper Mines sought to improve the cobalt alloy by producing a slag that is easier to handle and process in subsequent processes. Cobalt alloy (3.60% Co, 85.4% Cu) was re-melted in a copper bath four times the mass of the alloy. Silica and lime were added for phase separation and fire refining commenced. Following completion of fire refining and after holding the temperature at 1200°C, cobalt-rich slag was skimmed and blister copper was cast into anodes for electrorefining

Jan 1, 2023

By H. C. Van Der Merwe

In the 21st century, dynamic, accurate digital 3-D geological models are essential to the pursuit of safe, efficient and profitable mining. This is particularly true for the deep-level underground mines in South Africa. The Sirovision® solution is a collaboration project between the Australian CSIRO (Commonwealth Scientific and Industrial Research Organisation), Datamine Software Ltd. and AngloGold Ashanti Ltd (AGA). The purpose of the project is to provide a fully integrated digital rock face imaging, geological mapping and modelling system for the AGA gold mining operations. The CSIRO-developed Sirovision® Stereo Camera Rig (SCR) consists of two digital cameras, alighting system, a laser guidance system and image processing software. The imaging system works on the principles of photogrammetry, i.e. overlaying of two 2-D images with a central focus point, with mathematical algorithms extracting 3-D information from the 2-D image pair. The output from matching several image pairs is a computer-generated, full 3-D, virtual copy of the mining excavation. The image resolution and relief ares of sufficient quality to distinguish different rock types and structural contacts. Functionality within Datamine Studio3 is used to add geological intelligence to the 3-D images provided by Sirovision®. The geologist identifies and ?draws? lines representing geological features directly onto the image. By utilizing the inherent ?topography? of the 3-D image, the software is able to convert the lines into 3-D surfaces, ready for use in the 3-D geological model. Subsequent to promising underground test results from AGA?s Sunrise Dam Gold Mine (SDGM) in Australia and other mining operations worldwide, it was decided to test the Sirovision® system in the South African deep-level gold mines. The first underground tests at Moab Khotsong Mine began in January 2009. The objectives of these tests entailed the capturing of 3-D images of selected development ends, mapping of geological features onto the 3-D images and integration of the mapping data with the 3-D geological model. Some downsides have cropped up during the feasibility testing, related to practicality of the SCR for acquisition of 3-Dimagery in the deep-level underground operating environment. These constraints will have to be addressed prior to operational implementation. Facing such difficulties is not unusual when attempting to implement new technology in such a challenging working environment and testwork is still in progress at the mine in order to prove the concept of using this technology in a Witwatersrand underground gold mine. The great advantage of the Sirovision® solution is that it offers the geologist the opportunity to work remotely on a 3-D virtual copy of a mining excavation, without the heat, humidity, hazards and time constraints associated with physical mapping in an underground workplace.

Jan 1, 2009

By D. F. Malan, D. Ile

This study explores the use of backfill in hard rock bord-and-pillar mines to increase the pillar strength and extraction ratio at depth. The use of backfill will also minimize the requirement for tailings storage on surface and the risk of environmental damage. A literature survey indicated that backfill is extensively used in coal mines, but rarely in hard rock bord-and-pillar mines. To simulate the effect of backfill confinement on pillar strength, an extension of the limit equilibrium model is proposed. Numerical modelling of an actual platinum mine layout is used to illustrate the beneficial effect of backfill on pillar stability at greater depths. The magnitude of confinement exerted by the backfill on the pillar sidewalls is unknown, however, and this needs to be quantified using experimental backfill mining sections equipped with suitable instrumentation.

May 3, 2023

By M. Lange

The postulation that primary platinum group metal (PGM) matte will chemically react with magnesia-chrome bricks when temperatures exceed 1500°C was tested. Magnesia-chrome brick samples were heated in contact with matte at 1300°C to 1750°C for 30 minutes, after which the refractory samples were analysed using reflected light microscopy and scanning electron microscopy. The samples were all completely penetrated by matte. As the temperature increased the matte also penetrated the fused aggregate grains and disintegrated them. The chromium concentration of the matte inside the refractory samples was found to be slightly higher than that of the bulk matte. At temperatures of 1500°C and higher, MgO, FeO, and magnesium-rich silicate crystals could be identified in the matte directly adjacent to the refractorymatte interface. Phase relations clearly indicated that chemical reactions take place between primary PGM matte and the magnesiachrome refractory material at temperatures above 1500°C, but that these reactions are more complex than expected from FactSAGE® calculations.

Jan 1, 2014

By P. K. Jain

A spiral concentrator is a density separation device used for the beneficiation of coal and various minerals such as iron ore, chromite ore, gold, beach sand minerals etc. The flow pattern developed in the equipment is complex and unique, yet the operation is very simple, with low capital and operating expenditure. Spirals are applied for beneficiation of material in the size range finer than 2 mm and are capable of recovering heavy minerals as fine as .01 mm. The understanding of the unique flow pattern has kept researchers engaged over the last few decades and attempts are being made to explain such flow patterns so that they can be controlled and modified to improve the operating efficiency, Ep (Ecart Probable Error, also known as probable error in separation) and acceptability of spiral concentrators for processing of fines and slimes - currently being discarded and dumped in the tailing ponds. An attempt has been made in this paper to explain the generation of complex flow patterns with application to classical solid mechanics in the fluid and slurry system. The same has been used to explain the selective separation of particles in different zones in a cross-section on the spiral trough. The paper also discusses the application of a force balance model to explain the generation of secondary circulation. Due to the presence of laminar and turbulent flow regimes in the spiral concentrator, varieties of equations have been proposed in the literature, consisting of different equations for different zones. An attempt has been made to present a unified flow equation for calculation of flow velocity at different positions on the spiral trough. Keywords: Secondary circulation, spiral concentrator, density separation, fine particle processing

Jan 1, 2020