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By R. G. B. Pickering

Over the last few years Lonmin Platinum and Sandvik have embarked on a unique partnership of collaboration through a systematic approach to developing equipment to mechanize and automate narrow reef platinum mining. After the initial design and manufacture of the equipment the key aspect is the integrating equipment, people and method into a mining system. Another key aspect of mechanization is the optimization of equipment utilization, and this philosophy has ensured continual evolvement of mining methods. This paper describes the trials and development that have resulted in the mining method described as Lonmin mechanized breast.

Jan 1, 2007

By R. G. B. Pickering

Resue mining was practiced extensively in the East Rand in the first half of this century. The obvious benefits were that a higher grade of ore was trammed to the surface. The disadvantages were slow rates of face advance and an extremely labour-intensive method of mining. A collaborative effort by personnel from Avgold?s Target Gold Mine and Sandvik Tamrock has resulted in the design of a method of resue mining which can be totally mechanized. The purpose of this paper is to describe the methodology used and the proposed new mechanized resue mining method.

Jan 1, 2000

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. Bircumshaw

Paper written on project work carried out in partial fulfilment of BSc (Eng) (Chemical) degree This paper details the formulation of a mathematical model for the simulation of a primary bioleach reactor, with specific reference to the leaching of pyrite. The model is based on the direct reaction mechanism, where the leaching of pyrite is said to occur via a two-step process. The process involves the formation of ferrous?iron through the chemical leaching of pyrite and subsequent bacterial oxidation of ferrous-iron back into ferric-iron. At steady state the rate of chemical leaching and bacterial oxidation are linked by the ratio of ferrous-iron to ferric-iron in solution. The extent of conversion of pyrite in the reactor system is described using the segregated flow model, with the exit age distribution of the solid phase being described by the Tanks-in-Series model. The final phase in model formulation involves the inclusion of steady state material balances on the bacteria and fluid phase components. The model is compared to pilot plant data and laboratory data for two different types of pyrite concentrates, with simulation results showing that the model is in good agreement with the data. Author key words: Bioleaching; pyrite; primary reactor; modeling; segregated-flow model; tanks-in series model.

Jan 1, 2006

By M. Moys

The use of temperature measurements for unusual applications in the analysis and control of column flotation and milling is discussed. This is followed by a review of some of the authors current research in the application of the discrete element method to the modelling of particulate processes, specifically milling, fluidized beds and chute flow.

Jan 1, 2005

By F. T. Cawood

One of the consequences of globalizing mine finance is a necessity to apply uniform accountancy and valuation standards that are clearly understood and consistently applied by the global investment community. However, each country has unique circumstances, which sometimes make it difficult to align domestic practice with international requirements. South Africa is no exception and issues such as its political history, a taxation regime enforcing different rules on different mineral producers and a unique mineral rights ownership distribution, are barriers to internationalization. The economy is in a transitional phase as a result of the many and diverse policy documents following the change in political dispensation in 1994. Many of these documents have recently been implemented through new legislation and, in the case of mining, negotiations are continuing in order to ensure an acceptable outcome. This paper discusses the challenges that the South African minerals industry faces in the field of mineral property valuation. It draws on international experience and includes a discussion on the unique considerations that the South African mineral property market must take into account in establishing a code for this purpose, as such a code could later be aligned with international practice.

Jan 1, 2004

By N. Ragoonanthun

Paper written on project work carried out in partial fulfilment of B.Sc. (Mining Engineering) degree This report investigates the optimization of a raiseline in order to open up the ore reserve quicker. The project was carried out at Mponeng Mine (an Anglogold shaft formerly known as Western Deep Levels 1 Shaft and South Mine, in Carletonville). The project was divided into two focus areas namely: ?To design an optimum layout of a raiseline, which includes the scheduling of all activities for the establishment of the infrastructure. Consideration was given to the blasting practice, mining cycle, orepass placement and slusher positioning. Two designs were carried out on the above basis. ?The design of a ledging operation/practice to match the optimized layout of the raiseline. The ledging cycle design involved a thorough investigation into the possible use of drill rigs, Electronic Delay Detonators (EDD) blasting technology, longer drilled holes, Threshold Blasting (THROB),and water jet cleaning.

Jan 1, 2003

Control of flotation processes is mostly managed by plant operators, who assess the performance of the plant based on their own experience and other heuristic rules. These rules tend to be subjective or ill-defined, since most of them are concerned with the structure of the flotation froth, such as colour, bubble size and shape distributions, froth mobility and froth stability. These phenomena are very difficult to quantify objectively, and inexperience on the part of the operators, human error, etc., can lead to significant inefficiencies in plant operation. In this paper the development of a fuzzy system to support the control decisions of plant operators is described, which leads to significantly smoother control action and more stable plant operation than could be obtained with crisp sets of rules or manual control strategies. Keywords: flotation, fuzzy logic, image analysis, genetic algorithms, rule induction

Jan 1, 2000

The acoustic signals emitted from a laboratory-scale ball mill were used for the estimation of the comminution of two complex sulphide ores, viz. Merensky and UG2 ores from the Bushveld Igneous Complex in South Africa. The digital acoustic signals were transformed to power spectral densities that could be related to particle size distributions (-75 µm to 4000 µm) in the mill by use of continuum regression. This approach is more general than principal component regression methods or Kalman filtering used previously and resulted in significantly more accurate calibration in the case of the Merensky ore, where approximately 93.4% of the variance in the particle size distributions could be explained. With fewer data available, the variance in the particle size distributions in the UG2ore could be explained less accurately (82.4%), but still satisfactorily. In addition, smaller particle sizes (less than 300 µm) could be modelled more accurately in the case of the UG2 ore.

Jan 1, 2000

By Jeffrey C. Hillman

The need to recruit locally produced engineers by the South African Mining Industry led to the Engineering Faculty at the University of the Witwatersrand developing a number of academic bridging initiatives for educationally disadvantaged students. The graduation rate achieved during the initial five years of operation by the most successful of these programmes has been on a par with that of al other students but the performance of subsequent intakes has declined to such an extent that the continuance of this scheme could now be at risk. One reason for this reduction in throughput is that many of the applicants for the increasing number of mining bursaries have been more interested in the bursary than the profession and have either failed or dropped out due to a lack of application and motivation. This will have serious consequences for both Wits and the Industry if it continues and some method of identifying unsuitable or suspect applicants needs to be introduced as a mater of urgency. It is recommended that an introductory course be set up at a working mine that would be run under the auspices of Wits, as a joint venture with industry, and include a level of academic input that would provide both bridging needs and certain first year credits. The final form of this course will require extensive consultation with al parties but needs to be completed before the end of 1996. It is further recommended that the advertising and promotion of mining careers be expanded and much improved.

Jan 1, 1996

By A. D. Pelton, Y. -B. Kang, S. A. Decterov

Computerized thermodynamic databases for solid and liquid metal, slag and solid oxide phases in the Al2O3-CaO-CoO-CrO-Cr2O3-FeO-Fe2O3-MgO-MnO-NiO-SiO2-S system have been developed by critical evaluation/optimization of all available phase equilibrium and thermodynamic data. The databases contain parameters of models specifically developed for molten slags, liquid steel and solid oxide solutions such as spinels, pyroxenes, olivine, monoxide (wustite, periclase, lime), corundum, etc. By means of the optimization process, model parameters are found which reproduce all thermodynamic and phase equilibrium data within experimental error limits. Furthermore, the models permit extrapolation into regions of temperature and composition where data are not available. The databases are automatically accessed by user-friendly software that calculates complex equilibria involving simultaneously slag, metal, refractories and gases, for systems with many components, over wide ranges of temperature, oxygen potential and pressure. A short review of the available databases is presented. The critical evaluation/optimization procedure is outlined using the Al2O3-CaO-FeO-Fe2O3-SiO2and Al2O3-CaO-MnO-SiO2systemsas examples. Several applications of the databases to deoxidation of iron and to inclusion control in steel are discussed. Keywords: thermodynamics, phase equilibrium, phase diagrams, databases, ferrous metallurgy, steelmaking, inclusion control, slags, oxide systems.

Jan 1, 2004

By S. P. Pearton

"Pumpable emulsion explosives have been available to surface and underground massive mining operations for decades, and their unique properties offer significant advantages in terms of improved safety, reliability, and performance. However, the benefits of pumpable emulsions have been unavailable to narrow-reef mining operations due to the lack of technology necessary for their successful implementation in this challenging environment. Despite efforts to promote and enhance the safety and performance of bulk emulsions for narrow-reef stoping, little research has been undertaken to advance the pump technologies required for their implementation. This has resulted in a gap in knowledge and technology, and as a consequence the successful implementation of a pumpable emulsion system has consistently eluded the narrow-reef environment.The purpose of the following investigation was to evaluate the viability of pumpable emulsion explosives for use in South African narrow-reef mining operations. By approaching the problem from multiple perspectives, this research aimed firstly to propose a theoretical framework and suite of equipment suitable for the implementation of pumpable emulsions within the narrow-reef environment. Through the development of this suite of pumpable emulsion technology, tests could be undertaken on the proposed narrow-reef emulsion formulation and pumpable emulsion technology to obtain the necessary understanding of the performance of the system under controlled operating conditions prior to its implementation in the broader mining industry."

Jan 1, 2015

By A. H. Mokken

Failed attempts at amalgamation of a gold/osmiridium concentrate, recovered behind pebble mill liners during re-lining, led to the discovery that the gold particles were coated and that nitric acid only could remove the coatings. Following this treatment amalgamation was rapid and resulted in a complete recovery of the gold that otherwise would have been lost in plant residues. Investigations into the nature and formation of the coatings led to the realization that the coatings were impregnations of harder elements, associated with the gold during grinding and driven into the softer gold surface by high pressure, impact and attrition. It was further realized that this phenomenon could be part of gold ore milling, world-wide. With these thoughts in mind the question is asked whether concentration down to micron sizes prior to cyanidation, should not play a greater role in gold recovery.

Jan 1, 1999

By S. M. Rupprecht

"SynopsisOver the last decade in South Africa, there has been a significant increase in the number of mining operations, both open pit and underground, which use independent contractors to carry out mining activities. Often mine owners will choose the contractor option without fully understanding the consequences of undertaking this option. Traditionally, contract mining has come at a cost premium of about 15% to 20% compared to an owner mining scenario. However, due to the large number of junior mining companies entering the mining arena in South Africa contract mining rates have increased, with cost premiums as high as 50% being reported. This paper looks at the merits of owner mining versus contract mining and describes under what conditions it may be favourable to select the one option over the other. In addition, the methodology of entering into contract negotiations with the objective of establishing a fair and sustainable relationship is discussed.IntroductionOver the last decade in South Africa, there has been a significant increase in the number of mining operations, both open pit and underground, which use independent contractors to carry out mining activities. Surface mining, for example, may use contractors to conduct drilling and blasting operations or load and haul operations. Underground mining may contract out work such as shaft sinking, mining, support, construction work, cover drilling, sweeping and vampings. Common surface operations such as mineral beneficiation, waste disposal, security, and product transport may also be outsourced to contractors.Many companies have a business model that utilizes contractors for the entire mining cycle, maintaining a small head office to provide direction and control. The difficulty with this option is that often mining companies will choose the contractor option without fully understanding the implications."

Jan 1, 2015

By E. V. Lilford

The South African Minerals Development Act (?the Act?) has been promulgated and will come into full force and effect once it is gazetted. Thereafter, all Old Order mineral rights will have to be converted into New Order mineral rights within a 5-year period, probably by the end of 2008. The conversion of rights will be achieved only with the demonstrated inclusion of empowerment groups in the conversion applications. In addition to the Act, the first draft of the proposed Royalty Bill (?the Bill?) was released during the week beginning 17 March 2003. Comments on the Bill?s contents had to be submitted before 30 April 2003. The contents were to be considered in terms of applicability and acceptability to the South African minerals industry, where after proposed comments and suggested amendments were to be submitted to the relevant State Treasury office. Specifically referring to the Bill, the general response from the industry is one of concern. Since any royalty is tantamount to a tax, the general feeling is that the current mining taxation rates are already internationally competitive and to increase these effective rates, notably at differing rates depending on commodity type, will have an adverse impact on the South African mining industry. A number of these impacts can be mitigated to some degree, depending on the flexibility of the State to address the major concerns.

Jan 1, 2003

By F. Peer

This Technical Note was presented as a poster at the Western Cape Mineral Processing Symposium held in August 2001 The cleaning of fine coal (-1000 µm) in today?s coal preparation plants is an economically important factor. Coals with high ash contents are, in general, commercially undesirable. Current well-known techniques for treating fine coal include froth flotation and spirals. The primary critical factor with regards to spirals is the efficiency of the process whereas that of flotation, is the cost of there agents used. Research into enhanced gravity separation techniques has resulted in several commercially available enhanced gravity separators. This project was based on a preliminary investigation into the feasibility of one such separator, to effectively treat fine (-500 µm) coal. Experimental variables included particle size and speed of rotation of the said instrument. The performance of the separator was compared to the results obtained from liquid density separations done for the two coal fractions evaluated. From the results obtained in this preliminary study it appears that the piece of equipment investigated does not measure up to expectations. Recommendations for further investigation include the evaluation of the instrument on other South African coals to obtain conclusive results.

Jan 1, 2002

Escalating energy and electricity costs have become one of the largest drivers of expenditure in mining operations. Over the last eight years, energy costs have tripled when expressed as a percentage of total expenses in South African mines. In an effort to manage and reduce electricity costs, energy management strategies can be developed, inefficient operating units replaced, and the operation of energy-consuming components of ventilation systems optimized. Power consumption on mines is controlled mainly by three strategies, namely load clipping, by which energy use is reduced for certain parts of the day; load shifting, by which energy use is shifted to other parts of the day; and energy efficiency, by which energy use is reduced permanently. In this paper several projects that were implemented using the first two strategies of load clipping and load shifting are investigated. The actual and potential savings that can be achieved by implementing such energysaving interventions are presented. To reduce the operating costs of ventilating and cooling underground mines permanently, system optimization studies must be completed. Methods that can be used to reduce energy usage by optimizing cooling and ventilation systems are described, and network simulation models that accurately reflect the current and planned ventilation conditions are discussed. These models are then used to examine various options for improving the overall ventilation and cooling strategy. Different optimization scenarios can be simulated, and this assists the design engineer in obtaining the most energy-efficient system that will satisfy design workplace conditions. The final outcome is a reduction in operating costs, which can result in better operating margins and an extension of the life of mine.

Jan 1, 2014

By Manuel Rapiman, Ricardo Sepulveda

The feasibility study of Escondida Norte (ENorte), recommended a slope angle design for the Final Pit. But, according to the experience obtained with the slope adjacent to the West wall of ENorte, in which Compañia Minera Zaldívar (CMZ) gained in its phase 4, a slope of similar geotechnical characteristics will be exposed in the West Wall of Phase 1 (Premine) and of the Final Pit, with an interramp angle 53º and with very good stability results. In this regard, Minera Escondida Ltd. (MEL) performed a study of the slope angles for the phases mentioned and according to this delivered the results of this evaluation, the recommendations and/or the necessary conclusions in the design to ensure that the slopes are stable enough and may enable safe operational management of them.

Jan 1, 2006

By H. J. Ilgner

The paper reviews the results to date of an integrated research programme currently being conducted by CSIR Mining Technology, aimed at impacting significantly on concentrated mining with face advance rates of up to 20 times faster than presently achieved. Consideration is given to the interplay between innovative technologies for continuous non-explosive mining or rock comminution underground and lateral hydraulic transportation in cross cuts, haulages and eventually hydro hoisting. Novel technologies for underground comminution of reef and development waste and an innovative pumping system suitable for the hydraulic transportation of coarse comminuted rock are reviewed. Emphasis is placed on South African gold mine reef and waste samples comminuted by electric shock wave comminution technology. The innovative TORE® pump system appears to be well suited for the successful hydraulic transportation of rock, produced by electric shock wave comminution, at solids concentrations between 45 % and 67 % by mass.

Jan 1, 1997

By R. Altindag

Engineers and researchers need to estimate the mechanical properties of rocks from P-wave velocity. In previous studies, the researchers have investigated either the limited values or all the data belonging to sedimentary, igneous, and metamorphic rocks together in the same statistical analysis. In this study, the raw data pertaining to only sedimentary rocks was taken from previous studies and evaluated. For this purpose, a total of 97 samples of sedimentary rock types were subjected to statistical analysis. First, the relationships between P-wave velocity and physical-mechanical properties were investigated by simple regression analysis. All the data were then subjected to multi-regression analysis. Some empirical equations with high correlation coefficients were derived for rock engineers. The equations obtained from the analyses are compared with previous equations found in literature.

Jan 1, 2012