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By M. Vandewalle

What separates the support of mining openings from the support of similar civil engineering structures is the fact that mine openings have to survive large deformations as a result of changing stress conditions induced by progressive mining. Steel fibres impart to concrete and shotcrete a high degree of ductility which not only allows the shotcrete and concrete linings to absorb important rock movements but also to increase its bearing capacity by a redistribution of the loads. A range of applications will be discussed technically and economically.

Jan 1, 1998

Paper written on project work carried out in partial fulfilment of BSc Engineering (Mining) The aim of this project is to determine whether certain pillars occurring within the no. 1 shaft and no. 2 sub-shaft ground are feasible for extraction. The extraction of these pillars is essential in prolonging the life of Kloof Main Shaft as its VCR resource becomes depleted. Extraction of these pillars will require a combination of designs and factors, with rock mechanics and ventilation being the main considerations. Primarily for the pillar extraction, an initial production target of150 kg gold, mine able in one year from commencement of ?opening up? was set. The planned target has been exceeded and the feasible pillars identified are expected to yield an additional 1 390 kg of gold to the shaft?s production profile. However, not all the required ventilation designs have been completed to date, the reason being that at the time of the project, many of the pillar areas were inaccessible and thus ventilation conditions are unknown. This project is therefore an ongoing process and will require further design once all targeted pillar areas have been opened up. A preliminary costing analysis of the pillar mining was performed and it was found that all targeted pillars with the exception of 38?61 pillar are profitable.

Jan 1, 2005

By G. Smith

This paper describes the allure of diamonds over time and highlights the magic and mystery of famous diamonds. Consideration is given to the effectiveness of marketing in the diamond industry. It is concluded that diamonds are held as cherished possessions, valued far above their real market price, retained as valued heirlooms, and widely used as a form of highly liquid currency. In order to sustain value, both from an investment and jewellery perspective, demand has been stimulated to keep pace with growing global supply while the illusion that ?diamonds are forever? has been fostered to ensure that most diamonds, once sold, do not re-enter the market.

Jan 1, 2003

By I. Hague

Support liners for underground applications include steel and timber sets, meshing and lacing, screen/mesh, shotcrete and thin support liners (superskins). Over the past few years, major advances have been made in the design and application of liners; especially shotcrete and thin support liners. For shotcrete in mines these advances include the common use of slick-lines to solve logistics problems, the design of alkali free accelerators, the use of synthetic fibres and the new generation application equipment. The field of thin support liners is a new one but advances have been dramatic. This paper discusses the progress made and the need for standardization in definitions and testing for thin support liners. It concludes that the newer technologies have a huge potential positive impact on the industries, from both safety and cost points of view. Le chemisage de soutènement pour extraction souterraine comprend des cadres d’acier ou de boisage, mailles et chapeau, cribles/mailles, béton projeté et des chemisages minces de soutènement (super-peaux). Dans les dernières années, des progrès considérables ont été fait dans la conception et application des chemisages, en particulier les chemisages de soutènement en béton projeté et les chemisages minces. Pour le béton projeté dans les mines, ces progrès comprennent l’utilisation courante de lignes de minerais broyés fin pour résoudre des problèmes de logistique, la création d’accélérateurs sans alcali, l’usage de fibres synthétiques et d’une nouvelle génération d’outillage. Le domaine des chemisages minces de soutènement est très récent mais les progrès ont été rapides. Cette étude présente les progrès accomplis et discute du besoin de standardisation dans les définitions et les tests pour chemisages minces de soutènement. La conclusion est que les technologies nouvelles présentent un énorme impact potentiel positif sur les industries, du point de vue à la fois de la sécurité et de la rentabilité. Unterstützungsverkleidungen für Untertaganwendungen inkludieren Flecht und Seilwerk, Gitter/Geflecht, Spritzbeton und dünne Unterstützungsverkleidungen (superskins). Während der letzten Jahre wurden grosse Fortschritte im Design und in der Anwendung der Verkleidungen gemacht; besonders bei Spritzbeton und dünnen Unterstützungsverkleidungen. In Bezug auf Spritzbeton in den Gruben schließen diese Fortschritte den allgemeinen Gebrauch von Rutschbahnen ein um Logistikprobleme zu lösen, das Design von alkalifreien Akzeleratoren, den Gebrauch von synthetischen Fasern und die neue Generation von Anwendungsausrüstung. Der Bereich der dünnen Unterstützungsverkleidungen ist neu, aber die Fortschritte sind drastisch gewesen. Diese Arbeit behandelt den erzielten Fortschritt, die Notwendigkeit der Normierung in den Definitionen und in der Prüfung dünner Unterstützungsverkleidungen. Sie kommt zum Schluß, daß die neueren Technologien, sowohl vom Gesichtspunkt der Sicherheit als auch der Kosten, eine sehr große potentielle positive Auswirkung auf die Industrien haben.

Jan 1, 2003

By R. Banda

This paper describes the decision to implement and then the implementation itself, through trials, of electronic ?Smartdets? over previously used shock tubes. It concludes that Mufulira Mine has become the first mine in Zambia to convert 100% of its stoping to ?Smartdets?, because the Mine?s management was prepared to look beyond the unit cost of product and were ready to look at the broader picture of cost effectiveness and increased productivity.

Jan 1, 2005

By M. Ng

As part of a long-term study of titanium minerals processing being undertaken by the Julius Kruttschnitt Mineral Research Centre, techniques have been developed to measure the resistivity of ilmenite, rutile, zircon and other associated minerals. The techniques have proven reproducible and have allowed the measurement of resistivity under conditions of varying temperature, surface condition and surface moisture adsorption. The measured values can be linked to the separability of the minerals in the dry plant, and hence are useful as a diagnostic test for existing plants when performance deteriorates, or for greenfield sites to investigate potential problems. One of the major problems in electrical separation of titanium minerals is surface coating on the mineral grains. Coatings can make normally conductive minerals such as ilmenite and leucoxene behave much more like non-conductors. Electrical separation of surface contaminated ilmenite from non-conductors then becomes extremely difficult unless the surface contaminant is first removed. The resistivity measurement technique was used to evaluate the effect of surface cleaning on the resistivity of ilmenite and zircon from a Western Australian deposit which will shortly be in production. Ten different attritioning methods were evaluated, ranging from simple rinsing inwater to chemical attritioning in sulphuric acid combined with ultrasonic leaching. A roasting and quenching step was also investigated. As would be expected, the gentler treatments, such as rinsing in water or Calgon, had only amoderate effect on the ilmenite surface coatings. Ilmenite resistivity decreased by about 1 order of magnitude from 5.6 x108?m to between 2.5 and 4.4 x107?m. More intense treatments had a much more pronounced effect. The most effective, reduced ilmenite resistivity to 6.5 x105?m or three orders of magnitude. Zircon was relatively unaffected by any of the attritioning methods, with only a small increase in resistivity observed from 8.0 x1012?m to 2 x1013 ?m. The results show that measurement of mineral resistivity allows the effect of surface treatments to be easily quantified in a way that has benefits for greenfield site development where only small samples are available for testing. The effect of surface moisture has also been investigated using resistivity measurements. Measurements were made on zircon in an environmental chamber in which both humidity and temperature could be closely controlled. Zircon resistivity at 60 deg C decreased from 6 x1011?m at 5% relative humidity to 8 x108?m at 95% humidity. Moisture content and moisture re-adsorption from dry of zircon and number of other minerals were measured using a Mettler moisture analyser. Zircon adsorbed the least amount of surface moisture (0.05–0.09%) but re-adsorbed moisture from dry the fastest, reaching 98% of the original level in 10 minutes. Leucoxene adsorbed the most moisture (0.67%), but was much slower re-adsorbing this moisture from the dry state, reaching only 63% of the original level in 10 minutes. The difference was attributed to the surface characteristics of the grains, the leucoxene being much more porous than the zircon examined. The resistivities and differing rates of moisture adsorption can be used to quantify the effects of changes in atmospheric conditions of the performance of electrical separation in dry plants.

Jan 1, 2003

By S. Achilleoudes

This paper describes the various factors that contribute to the maximum design pressures acting on box fronts and how these factors influence the mass and economy of box front steelwork. The influence of material density, rock size and moisture content on the incidence of hang ups and mud rushes in the rock pass is also highlighted. The loads acting on any box front are a function of several different parameters. These include natural, operational and excavational parameters. A case study analysis was carried out using UG2 ore and a typical box front structure to demonstrate the relationship between the mass of the box front and the material pressures resulting from variations in the above parameters. Based on the results of this case study, the required design mass of a side mounted box front for a rock pass containing platinumUG2 increases in (close to) linear proportion to % overbreak and is also linearly proportional to the pressure on the face of the box front beyond saturated conditions. The mass of the box front structure also doubles with a 100%increase in over-break which emphasises that a box hole excavation that is as neat as possible will yield a lighter and more econimical box front structure.

Jan 1, 2005

By K. Goshtasbi

The mechanical behaviour of schistose sedimentary rocks such as slate show a great amount of anisotropy. Hence, the schistocity plane is essential when investigating the mechanical behaviour of such rocks. The presence of such rocks in civil projects causes non-symmetric deformation and their behaviour is unpredictable. In this research, the anisotropic strength behaviour of slates is studied. Uniaxial and triaxial tests were conducted on specimens having orientation angles (ß) of 0, 30, 45, 60, 75 and 90 degrees. The triaxial tests were done at confining pressures of 3, 5 and 10 MPa. The effect of anisotropy on uniaxial and triaxial strength, cohesion, angle of internal friction and Hoek and Brown's m and s constants were investigated. The results indicate that the strength of slates in uniaxial and triaxial compression exhibit a U-shaped anisotropic behaviour. In-order to evaluate the most suitable criterion for predicting the anisotropic strength of rocks in uniaxial and triaxial compression, an investigation was carried out on various criteria. In uniaxial compression, the Liao and Huong and Ramamurthy criteria had good agreements with the test results. In triaxial compression the Hoek and Brown and Mc Lamore criteria had better agreements with the test results. It should be noted that in-order to utilize these criteria, a large number of tests must be carried out. However, as the Ramamurthy criterion needs fewer test results, it can be the most suitable for investigating the behaviour of anisotropic rocks in triaxial compression. Keywords: Slate, anisotropy, schistose, failure criteria

Jan 1, 2006

By J. G. Wiese

Reagents are added to the flotation process of Merensky Reef ores to achieve specific functions that enable the separation of valuable minerals from gangue minerals on the basis of the difference in their surface properties. However, due to the complexity of the process, the various interactions that occur as well as the incomplete liberation of the ore and range of minerals present, it is difficult to quantify the behaviour of each of the reagents. More specifically, changes made to achieve a particular outcome may have secondary effects that can override the desired effect. If all the effects and interactions can be accounted for, it is possible to manipulate reagent suites and obtain better overall metallurgical performance. This paper discusses the effect of the addition of copper sulphate at different operating points of the recovery of the sulphide minerals. Batch flotation tests indicated that the recovery of chalcopyrite was not affected when operating conditions were varied, whereas pentlandite recovery was strongly affected by the point of reagent addition, and pyrrhotite recovery was enhanced by copper sulphate addition, irrespective of the point of addition, with the extent being dependent on the ore source. Floatable gangue was activated by copper sulphate in the presence of the dithiophosphate collector. Froth stability was also affected by copper sulphate addition.

Jan 1, 2007

By M. Nyoka

Consideration of the economic, environmental, and social impacts associated with the life-cycle of a technology is of increasing importance for decision-making in industry. It has been suggested that economic assessment of technology deployment projects requires the translation of associated environmental effects into monetary values. This paper introduces an approach for identifying and evaluating environmental damage in monetary terms. The approach groups the environmental impacts associated with a technology life-cycle system into four main criteria: air, water, land, and mined abiotic resources. The valuation of the impacts on the resources consists of an economic cost benefit analysis (CBA) procedure that comprises four steps: the compiling of an impact inventory, a monetary valuation of the inventory, discounting, and a risk/uncertainty analysis. The monetary valuation step for impacts on air resources is primarily based on published externality costs for Europe and the United States, which are adopted and converted to reflect the South African context. Local opportunity costs are utilized for the other resource criteria. The damage costs are transformed into South African Rand at 2005 prices. The paper demonstrates how the approach may be applied in the assessment of projects in the metallurgical industry. Shortcomings in the approach are identified. For example, not all of the aspects that are considered necessary to assess environmental performances comprehensively can be valued in monetary terms. Also, certain values, specifically those pertaining to opportunity costs, need to be determined on a case-by-case basis. Furthermore, the uncertainties associated with the indicators obtained may strongly influence the usability of the results of an environmental performance assessment, e.g. future damage costs will change with fluctuations in the markets. It is concluded that although such an approach has merit in increasing the understanding of the potential financial implications of a technology?s environmental performance, further research is required to improve the approach described if it is to be used further in the South African metallurgical industry. Damage cost estimates that are specific to South Africa need to be developed to reduce uncertainty, and the combination of both quantitative and qualitative approaches is recommended for comprehensive sustain-ability decision-making.

Jan 1, 2007

By R. Scott

This article describes and evaluates the establishment of Kuyasa Mining including the search for a suitable deposit, the ongoing lack of finance, and market constraints. Despite the dramatic initial growth and success of their Ikhwezi Colliery near Delmas, Mpumalanga, Kuyasa?s experiences offer some sobering arguments for significant changes to mineral rights ownership, the attitude of financial institutions and government policy if South Africa is to have a dynamic and successful junior and small-scale mining sector.

Jan 1, 1998

By A. S. Macfarlane

The South African Institute of Mining and Metallurgy was approached by the Australian Institute of Mining and Metallurgy to present a paper on the current practice in terms of the valuation of mineral projects and properties, given the development of a Code for the Valuation of Mineral Properties, developed in Australia (the VALMIN Code), and a similar Code in Canada (the CIMVal Code).This paper is the result of research and investigation into the matter, in terms of the reporting of Mineral Resources and Reserves, financial reporting practice, the Listing Rules of the Johannesburg Securities Exchange, and various practices in valuation. The paper establishes that a strong linkage has already been established between the SAMREC Code for the reporting of Mineral Resources and Reserves and the Listing Rules, and that, for completeness, a Code for Valuation needs to be developed. This Code will be similar to its international counterparts, with the necessary inclusions which are relevant to South Africa, and will provide guidelines and definitions on matters such as transparency, materiality and competency in valuation. It proposes that a multi-stakeholder steering committee be established under the auspices of the SAIMM, to deliberate and design a process for establishing such a Code.

Jan 1, 2002

By R. G. Cawthorn

The earliest authenticated scientific report of the occurrence of platinum in rocks from the Bushveld Complex appears to be by William Bettel on 10 November 1906. Thereafter, prospecting of the chromite-rich rocks for platinum proved frustrating. I suggest that the resurgence of interest shown by Dr Hans Merensky in 1924 resulted from his realization that newly panned platinum had a different grain size from that in the chromite layers and indicated a different source rock, which he located, and it became known as the Merensky Reef.

Jan 1, 2007

By R. T. Jones

The 20 Mt reverberatory furnace slag dump at Nkana in Zambia contains a substantial quantity of cobalt. A 40 MW DC arc furnace has been built at Chambishi for the purpose of recovering cobalt from the slag. The technology was jointly developed by Mintek and Anglovaal Mining Ltd (Avmin), and the furnace was designed by Bateman Titaco. Testwork at the 150?250 kW scale was conducted at AVRL, and larger scale piloting was conducted at Mintek (in partnership with Avmin) in a 3 MW DC arc furnace. Approximately 840 tons of Nkana dump slag (ranging from 0.66% Co) was processed at power levels around 1-2 MW. Good overall cobalt extraction was achieved, and approximately 100 tons of cobalt-bearing alloy was produced (containing 5 to 14% Co). This testwork demonstrated that the Nkana dump slag could be processed in a DC arc furnace of suitable design, to produce a cobalt-bearing alloy suitable for further hydrometallurgical processing. Bateman Titaco were contracted to design and build the furnace, and the design team contained representatives from Avmin and Mintek. The project was conceived as a fast-track exercise, and many activities had to be run in parallel. Notable features of the furnace include an ABB power supply, a Concast conductive hearth, the refractory design, and copper cooling in the sidewalls. Power to the furnace was switched on during January 2001.

Jan 1, 2002

By D. Pillay

Outsourcing? and ?sub-contracting? have become buzzwords in recent years, as SA industry becomes increasingly exposed to the global economy, and global competitiveness. In its effort to ?catch up? after years of relative isolation, there is a concerted effort to learn from global ?best practice?, in order for South African companies, and the SA economy, to become ?winners?. There seems nothing wrong with this approach at face value. Companies need to compete and be profitable if they are to remain in business. Failure will in the end mean bankruptcy, and the loss of jobs. However, if one interrogates the precise practices, and their implications for all concerned?not just shareholders and employers, but workers, communities, the environment, future generations, the national economy?then the picture can change dramatically. ?Best practice? for whom?

Jan 1, 1999

By G. Konak

In-pit crusher location selection has had an important role recently, since increasing diesel prices. One way of reducing the haulage costs is to shorten the truck haulage distance by bringing the truck dump point into the pit. This study covers the work done on the optimum crusher location definition for a company that produces aggregate near Izmir, a city of Turkey located in the west. This paper will discuss the effects of pit geometry and mine access requirements on optimum crusher location selection that are mainly based on the establishment of minimum haulage distance. The method will be introduced first and then the computer algorithm developed for this study will be discussed later in the paper. Keywords: in-pit crushing, optimum location selection, optimizing haulage, computer aided design.

Jan 1, 2007

By G. S. Littlejohn

Following study of historical South African practice and a review of recent experience gained during the design, construction and testing of the high pressure plugs at the South Deep Water Barrier Project, this paper makes recommendations to improve practice. Initially, site investigation requirements are described with reference to geological, hydrogeological and seismic considerations, including site preparation and pre-grouting of the surrounding rock mass, if permeable. Structural and hydraulic aspects of plug design address topics such as residual permeability, aggressive mine water, plug materials, mortar strength and bleed. In situ thermocouples and piezometers are recommended to optimize the timing of plug tightening and monitor plug performance during service. Plug construction covers aggregate preparation, mortar quality control, plug tightening grouts, injection pressures, records and the overriding need for a method statement specification to control all aspects of plug construction. On completion of the plug, tests to establish surrounding rock stress regime, plug strength, and residual permeability are described to enable a comparison with original design assumptions. Monitoring and maintenance procedures are proposed to ensure satisfactory long-term performance of the plugs.

Jan 1, 2006

By H. F. Fuls

The quality of Pregnant Leach Solution (PLS) at Skorpion Zinc is of utmost importance for efficient operation of the Solvent Extraction (SX) Plant. Suspended solids in the PLS forms CRUD in the settlers, resulting in reduced zinc transfer capacity and increased impurity carry over to Electrowinning. The Ishigaki Fibre-Wakishimizu filter (fibre media rapid filtration equipment) has been identified as polishing filter that potentially could remove solids from the PLS of Skorpion Zinc. A pilot unit with 20m³/h capacity was tested on site over a period of 9 months under plant operating conditions in the refinery. The FW filter produces a clear filtrate, acceptable for the Solvent Extraction. Turbidity is improved by 72%. Gravimetric analysis indicates a 47% removal of solids. However, the gravimetric method is biased by a co-precipitation of saturated salts during the analysis. Filter media is blinded by the Skorpion Zinc PLS solution, as result of suspended solids and process chemistry. The media could not be regenerated to acceptable conditions. Further testwork to investigate the impact of process solution chemistry modification on blinding is undertaken. Based on the outcome of this investigation a final decision on the FW filter can be taken.

Jan 1, 2008

The environmental impact of solid waste materials is closely linked to their potential to produce a hazardous leachate once deposited in a landfill. This potential is conventionally assessed with simple laboratory batch leach tests, which find more and more frequent application also in the minerals and metals industry. Such tests are intended to help distinguish between high and low risk wastes, but are completely unsuitable to allow quantitative prediction or modelling of the long-term leachate generation potential. In the present approach the leachate generation process is perceived as a combination of bulk convective transport, stagnant zone and inner particle diffusion, as well as reaction kinetic effects. Model equations are formulated accordingly. A modelling frame work, WASTESIM, has been developed at UCT, which allows flexible combination of the model components and simulation of leach scenarios. Quantitative model parameters are obtained from a systematic laboratory study on the waste material in question. The combined assessment and modelling approach is demonstrated with a study on Cr (VI) leaching from a ferro-chromium slag material. Although not straightforward, the approach is particularly useful in determining long-term liabilities in the context of waste disposal sites with considerably more reliability than has previously been possible. Keywords: waste deposits, waste leaching, heap leaching, environmental, risk assessment, Cr (VI), ferro-chromium, slag.

Jan 1, 2000

By L. P. Lamprecht

Traditionally, South African shaft sinking operations have used electric detonators for the initiation of blastholes. Globally, the trend in shaft sinking is to use the shock tube and detonating cord (STDC) initiation system, with value adding benefits. In pursuing this global trend, Cementation Mining of South Africa in partnership with SMX have ventured the STDC route. This paper explores the work carried out to date, and identifies a number of benefits to be gained by using the system.

Jan 1, 1999