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By S. Curry

The Objana Cement Plant is located in central Nigeria, approximately 200km south of capital city Abuja (figure 1). It is the second largest cement plant in Africa, and the fifth largest in the world [1]. The selected mining location is unique as it has all the major raw materials (except gypsum) in close proximity. This includes limestone, clay, marl, laterite soil, and laterite iron. [ ] The plant has a capacity of 5 million metric tones per year (~15,000 tones per day). A 135 megawatt gas-fired power plant, with 90 km of natural gas pipeline, was constructed to power the plant. The total project cost is approximately 1.2 billion US dollars. The lifeline of the plant is two overland conveys totalling 7.7km in length. The first 800m conveyor is relatively mundane. The second conveyor however, is unlike any other troughed belt conveyor in the world. It 6.9km length transports 2,400 T/H and operates at 5.0 m/s. Its ?snake? profile consists of 11 vertical cuvees, and four horizontal curves. The last of which is 2,000m in radius, has a length of 2.2km, and is located at the high tension head end of the conveyor. Although these specifications are noteworthy, the unique feature of this system is that it is entirely elevated from head to tail using a triangulated truss gantry structure (figure 2).

Jan 1, 2008

By S. M. Spottiswoode, Linzer. L. M.

We report on further progress in improving seismic locations by using the so-called double-difference method (Spottiswoode and Milev, 1998 and Waldhauser et al., 1999). Double-differences are obtained either using picked arrival times or various measures of time differences obtained from waveform pairs. The double-difference method provides for much improved relative locations by reducing the effect of the errors in the wave velocity of ray paths between each event and each geophone. Further improvements are obtained by using known locations, such as blasts. One of the difficult problems that we have overcome is that of finding the best “weights” for the time corrections. Experience obtained in relative moment tensor inversions by Andersen (2001) suggests that use of median corrections is both more stable and more accurate, even while the locations of the individual events is based on weighted least-squares minimization. A hybrid location program with known reference events has been developed. Tests on a synthetic data set gave relative locations that were much less widely spread than the absolute locations. The use of known event coordinates (blasts) moved the relative locations back towards the real locations. These results are confirmed in preliminary analysis of data from a mine. The absolute locations are adjusted using blast events restricted to the line of tunnel development. Inter-event distances are distributed in a power-law fashion that suggests that the relative location accuracies are improved by a factor of three or more. Nous rendons compte des progrès faits dans l’amélioration des locations de séismes en utilisant la méthode appelée de double- différence (Spottiswoode and Milev, 1998 et Waldhauser et al., 1999). On obtient les double-différences soit en utilisant des temps d’arrivée choisis soit des mesures variées de différences de temps obtenues de doublets de forme d’onde. La méthode de double-différence fournit des locations relatives très améliorées en réduisant l’effet des erreurs dans la vitesse d’onde des trajectoires de rayon entre chaque évènement et chaque géophone. D’autres améliorations sont obtenues en utilisant des locations connues, telles que les coups de mine. Un des problèmes difficiles que nous avons surmontés est celui de trouver les meilleurs coefficients de pondération pour les corrections de temps. L’expérience obtenue dans des inversions de phases tensorielles relatives par Andersen (2001) suggère que l’utilisation de corrections médianes est à la fois plus stable et plus exacte, même lorsque la location des évènements individuels est basée sur minimisation pondérée de moindres carrés. Nous avons développé un programme hybride de location avec des évènements connus pour référence. Des tests sur des données artificielles ont donné des locations relatives qui étaient beaucoup moins étendues que les locations absolues. L’utilisation de coordonnées d’évènements connus (coups de mine) a ramené les locations relatives vers les locations réelles. L’analyse préliminaire des données d’une mine a confirmé ces résultats. Les locations absolues sont ajustées en utilisant des évènements de coup de mine restreints à la ligne du développement du tunnel. Les distances entre chaque évènement sont distribuées comme par loi exponentielle ce qui suggère que les degrés d’exactitude des locations relatives sont améliorés par un facteur de trois ou plus. Wir berichten über einen weiteren Fortschritt, die seismische Positionen unter Verwendung der zu sogenannten Doppel-Unterschied-Methode (Spottiswoode und Milev, 1998 und Waldhauser et al.,1999) zu verbessern. Doppel-Unterschiede werden entweder mit ausgewählten Ankunftszeiten oder verschiedenen Messungen von Zeitunterschieden erreicht, die von den Wellenformpaaren erhalten werden. Die Doppel-Unterschied-Methode liefert viel verbesserte relative Positionen unter Verringerung der Auswirkung von Fehlern in der Wellengeschwindigkeit von Strahlengängen zwischen jedem Fall und jedem Geophon. Weitere Verbesserungen werden erreicht, indem man bekannte Positionen, wie Sprengungen verwendet. Eines der schwierigen Probleme, die wir überwunden haben, ist jenes des Findens der besten "Gewichte" für die Zeitkorrekturen. Die Erfahrung, die in den relativen Momentspannerumkehrungen von Andersen (2001) gewonnen werden bietet den Schluß an, daß der Gebrauch von mittleren Korrekturen beständiger und genauer ist, sogar wenn die Positionen der einzelnen Fälle auf der bewerteten Reduzierung der Methode der kleinsten Quadrate basiert. Ein hybrides Positionsprogramm mit bekannten Bezugsfällen ist entwickelt worden. Tests auf einem synthetischen Dataset gaben relative Positionen, die viel weniger weit gestreut waren als die absoluten Positionen. Der Gebrauch von bekannten Fallkoordinaten (Sprengungen) schob die

Jan 1, 2003

By Z. T. Bieniawski

Estimating the strength of rock materials by Z. T. BIENIAWSKI, Pr.Eng., D.Sc.(Eng.) (Visitor) A practical approach for estimating the strength behaviour of rock materials is presented. The demand for data on rock properties in engineering design is considered, and it is shown that, based on the trends observed in the South African mining industry during the last twenty years, simple and easy-touse methods for the estimation of the uniaxial and triaxial strength of rock materials are needed. It is shown that the uniaxial compressive strength of rock can be conveniently determined from the pointload strength index, which is obtained underground on unprepared rock cores. The triaxial strength of rock can be estimated for most practical purposes from empirical strength criteria. Two such criteria are proposed that allow estimation of the triaxial strength for rock materials to about 10 per cent. The only input required for these criteria is the uniaxial compressive strength. The validity of the practical approach outlined in this paper is confirmed from the experimental tests conducted on some 700 rock specimens representing five rock types. A practical example for the prediction of rock strength is given.

Jan 3, 1974

By M. H. Moys

A method of estimating the percent solids in the discharge from a grinding mill is described and tested on both pilot and industrial scale. It involves the use of energy and mass balances around the mill discharge sump, requiring measurements of the flowrate and density from the sump together with temperatures of all streams flowing to and from the sump. Accurate estimates of the dynamic variation of mill discharge percent solids are made available, provided that occasional manual sampling of the stream is done to cope with drift in instrumentation. The use of a computer in this application was essential; the various advantages associated with its use are discussed. It is anticipated that this estimate of discharge density can be controlled at a set point by manipulation of the water fed to the mill, resulting in significant decreases in specific power consumption and media consumption.

Jan 1, 1987

By G. E. Blight

Many mines engaged in deeplevel gold mining in South Africa are experimenting with the use of tailings fills, or are implementing tailings backfilling programmes on a limited scale. The approach varies from mine to mine, depending on circumstances and available fill materials. Several mines are backfilling with a cyclone underflow product; the cyclone overflow is then combined with the balance of the tailings stream and directed to surface disposal. As the extent of backfilling increases, the proportion of the surface tailings stream composed of overflow material will rise, and the properties of the tailings requiring surface disposal will approach those of the cyclone overflow. As the latter will be finer, less permeable and possibly weaker than the total tailings currently being disposed, the design and operation of surface tailings dams will have to be modified. Dams may have to be designed with flatter outer slopes of a reduced maximum height. Lower rates of rise may be required and, as a consequence, larger disposal areas may be demanded. To offset the negative aspects is the fact that the quantity of tailings requiring surface disposal will be reduced. The paper explores the dam-building properties of two cyclone overflow products. It shows that although these materials are inferior in dam-building characteristics to the corresponding total tailings, their geotechnical proper- ties still fall within, or close to, the range of properties typical of gold tailings. Although the design and operation of tailings dams may have to be modified, existing technology is adequate to handle these changes.

Jan 1, 1988

By H. Sasao, Y. Obara, A. Hirata

In the upper part of the planned location of the portal of a highway tunnel, there was a steep rock cliff with several unstable rock blocks. It seemed that the risk of those rock blocks to fall was very high. The cut-out to stabilize the rock cliff was monitored with various measuring instruments to prevent the sudden fall of the rock blocks. This paper discusses the measurement of acoustic emission and interpretation of its result during excavation of the rock cliff. We calculated displacements by integrating the accelerogram twice in terms of time, and demonstrated that slight displacements can be calculated from the measured AEs. Dans la partie supérieure de l’emplacement prévu pour le portail d’un tunnel autoroutier, il y avait un escarpement rocheux raide avec plusieurs blocs rocheux instables. Le risque de chute de ces blocs semblait très élevé. Lors de la coupe pour stabiliser l’escarpement rocheux, le suivi a été effectué avec différents instruments de mesure pour éviter la chute brutale des blocs rocheux. Cette thèse présente les mesures d’émission acoustique (EA) et l’interprétation de leurs résultats pendant l’excavation de l’escarpement rocheux. Nous avons calculé des déplacements en intégrant l’accélérogramme deux fois par rapport au temps, et montré que de petits déplacements sont calculables à partir des EA mesurées. Im oberen Teil des geplanten Ortes des Stollenmundes eines Autobahntunnels gab es einen steilen Felsen mit mehreren instabilen Felsenblöcken. Die Gefahr schien sehr groß zu sein, dass diese Felsenblöcke einstürzen können. Beim Abbau um die Stabilisierung des Felsens wurde das Monitoring mit verschiedenen Messinstrumenten zusammengestellt, um den plötzlichen Verfall der Felsenblöcke zu verhindern. Das vorliegende Papier diskutiert die Akustische Emission und die Auslegung deren Ergebnisse während des Abbaus des Felsens. Wir berechneten die Verschiebungen durch zweimalige Integrierung der Accelerogrammen in Bezug auf die Zeit. Die dargestellten kleinen Verschiebungen können aus den gemessten akustischen Emissionen berechnet werden.

Jan 1, 2003

The increasing transportation of solids by pipeline, in South Africa and internationally, replacing the conventional transportation methods of rail, road, and conveyors, has resulted in much research into this area of solids transportation. Pipeline wear continues to be an area of specific concern, since it constitutes a major cost during the life of a pipeline installation. Wear data from an accelerated wear test and actual pipeline tests are presented. Trends in the performance of the pipeline materials tested are discussed, and possible solutions to the problem of pipeline wear are presented.

Jan 1, 1992

By A. Whillier

Recommendations are given for the design of vertical cooling towers for use underground in mines and a method is given for predicting the entering and leaving water temperatures when a given amount of heat has to be dissipated.

By W. F. Lorch

Growing use of deionised water in surface coating techniques by w. F. LORCH Production engineers in the metal plating, paint, plastics-coating and printed circuit industries are increasingly aware of the cost of sub-standard or blemished items which have been poorly processed. An area where quality control can quickly produce higher efficiencies is in the choice of suitably purified water for making up solutions, for rinse baths and 'drag-out' baths, for cleansing lines and electrophoresis tasks, for maintaining electrolyte density and hence consistency, and for facilitating the recovery of valuable minerals. The author of this article examines the general problems of using nonpurified water, and shows how purified water has become accepted by the principal surface coating industries to improve processes and effect economies.

By Paul Fouchè, Danie van der Merwe

Contents ?Purpose ?Introduction ?Development of RF tracers ?Test procedure ?Results ?Conclusion ?Way forward ?Acknowledgements

Jan 1, 2005

By John Taylor

?Introduction to Black Mountain ?Historical metal accounting practice ?Metal accounting audit ?Feed measurement ?Sample precision ?Concentrate measurment ?Current metal accounting practice ?Further refinements to the metal accounting practice

Jan 1, 2005

By D. Francois-Bongarcon

The ?Poisson effect? is defined and characterized. It takes place even when the material to sample is not liberated. Gy, Pitard, Ingamells, and others, including the author, recommend that a minimum average number of particles of mineral of interest characterize the recommended sample size. How many? Recommended numbers range from 6 to 40 particles depending on authors, corresponding to standard deviations of 41% to 16%. Some guidelines are proposed, and the often alleged ?double-Poisson? effect is examined.

Jan 1, 2009

While some of the practical details of ilmenite smelting are not well documented, there is a substantial body of literature on the principles of ilmenite smelting, and the behaviour of solidified titania slag. This information is summarized, focusing on the basic reactions, departure from equilibrium, the behaviour of impurities, and reactions of solidified slag. The emphasis is on the South African operations.

Jan 1, 2007

By B. M. Kunar

It is well known that job-related hazards and individual factors influence occupational injuries. However, research involving coalminers has been limited. This case-control study assessed the relationships of job-related hazards and individual/life style factors with injuries among underground coal miners. It compared 245 cases with at least one injury during the previous two-year period with 245 matched controls with no injury. The data were gathered via personal interview and analysed using the conditional logistic model. The significant risk factors were materials handling (adjusted OR 5.15), poor environmental/working conditions (2.63), geological/strata control-related hazards (2.35), lack of formal education (3.00), sleep disorders (1.86), alcohol consumption (2.32), disease (2.23), having a large family (5.40), and risk-taking behaviour (9.40). Machine-related hazards, sleep disorders and alcohol consumption primarily affected workers aged less than 45 years; whereas, environment/working condition-related hazards, presence of disease, smoking, risk-taking behaviour and large family size were more likely among workers aged 45 or over. Keywords: Occupational injuries, sleep disorders, job hazards, alcohol, coal miners

Jan 1, 2010

By K. R. Noble

The planned extraction of the No. 1 shaft pillar at Blyvooruitzicht Gold Mine highlighted a number of potential problems. In spite of the relative shallowness, careful thought had to be given to stope phasing owing to the detrimental effect of the anticipated geology and the fact that uninterrupted hoisting was necessary. Extensive use was made of computer modellig to design the stope phasing, determine the influence of regional support and to predict the direction and magnitude of displacements in the shaft. The paper describes the success of this design approach, and measured displacements in the stoping horizon and shaft barrel are compared to those obtained from the original computer model

Jan 1, 1987

By N. Graham, C. Walker

The SORD Miner is a patented mining principle being developed to exploit mineral and energy resources that current technology can not access. SORD Miner is designed to operate in underground wet, granular, continuously collapsing geological environments such as alluvial and marine deposits. It is somewhat like a cutter suction dredge and should be capable of mining its way through any fine granular material like sand or gravel, pumping the slurry back to the surface. In areas where the target layer is covered, the SORD Miner is inserted below the water table and will tunnel its way to the mineral deposits at depth. This paper describes the development, concept testing and prototype construction of the SORD Miner.

Jan 1, 2007

By L. A. Abichequer

ROM grade variability is one of the most important factors influencing plant product recovery. Due to the influence of grade variability on mine profits, it is deemed important to guarantee a proper homogenization of the ore through a well-planned blending and homogenization pile system from which the ore is reclaimed at an acceptable grade fluctuation. This study tests geostatistical simulation efficiency in predicting in situ grade variability. The methodology is illustrated using a data-set from a large phosphate mine in central Brazil. Additionally, real data obtained at the mine site during January and February 2007 were used to derive the actual grades of each pile formed during this period. Each pile was formed by a selection of blocks within a dig line and these lines mined along the year 2007 were also made available. Given the real grades, it was possible to reconciliate and validate the results predicted by the proposed methodology. The main outcome of this study is the opportunity to check the geostatistical simulation as a tool to quantify the variability of the homogenization system.

Jan 1, 2009

By B. Steyn

AngloGold Ashanti?s Obuasi Mine, in Ashanti Province, Ghana, operates a plant utilizing bacterial oxidation technology. The mineralization consists predominately of arsenopyrite with gold associated in the sulphides. The plant was commissioned in 1994, at that time was the largest BIOX® plant in the world, and has been operated by AngloGold Ashanti since 2004. The constraints identified in the plantwere the flotation capacity, BIOX® feed size and disruptions to the BIOX® process. This paper focuses on the practical steps that were followed in order to increase the recovery of the plant. The original plant design was based on a head grade of 10 g/t and an overall recovery of 86.5%. In 2007 the plant was operating at an overall recovery of 79.2% at a head grade of 5.6 g/t and this has improved to 80.6% at a head grade of 5.8 g/t during the last quarter of 2008. Additional improvement to 81.5% are expected by the end of April 2009. Improvements that have been implemented include: ?Replacement of the regrind mill ?Installation of additional float capacity ?Installation of a scavenging circuit ?Installation of a complete water treatment plant. In addition we have focused on the effect of the water circuit on the BIOX® process and the steps involved in correcting this problem. The water circuit was originally designed as an open circuit and through environmental considerations the circuit was closed towards the end of 2007. The bacteria in the BIOX® are particularly sensitive to cyanide and cannot tolerate levels above 0.05ppm (free cyanide), this required extensive modifications to the water circuit. The plant improvement project is ongoing and the current scope of work should be complete by the end of April 2009. Further research and development work is being planned, which includes a ?white rot bacteria? that can consume the preg-robbing carbon and oxidize the sulphide in a single pass.

Jan 1, 2009

By SHM Harkema, MKG Vermaak, D R. Groot

Surface Plasmon Resonance spectroscopy (SPR), combined with cyclovoltammetry, has been successfully used to study the interactions between ethyl xanthate, heptyl xanthate, dithiophosphate and propyl trithiocarbonate flotation collectors and a gold surface. Large, easily measurable responses have been obtained in the potential areas where the thiol collectors are known to interact with gold. The four collector types lead to differing SPR maximum values, with longer alkyl chains resulting in higher SPR responses, and the trithiocarbonate leading to the highest response values. The SPR responses differ considerably from the current density response at very anodic and cathodic potentials. There are indications that thiols might still be adsorbed at potentials as low as -300 mV (vs SHE). Keywords Flotation collectors; thiol collectors; cyclovoltammetry; surface plasmon resonance spectroscopy.

Jan 1, 2005

By R. J. Cocks

Water auditing and water efficient practices are evolving as the quantitative tools for water balance reporting in the mining and minerals processing sector. This paper was written to describe the process of water auditing in a gold mining environment. It will contribute towards building an appropriate water management framework for The Cooperative Research Centre (CRC) for sustainable resource processing (CSRP). The research assists with the assessment of water balances in mining and hydrometallurgical processes and provides, on the ground, steady-state data for ongoing probabilistic modeling underway at most of Newmont?s gold mine operations. Five Newmont case study mine sites including the Tanami Granites Goldmine are central to this PhD water project study. The function of the Tanami-Granites water audit exercise was to measure a controlled flow of various water quality types and set a framework to establish further research for water efficiencies and water conservation in mining.

Jan 1, 2009