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The major proportion of South African coal is extracted by the bord-and-pillar mining method which requires that the overlying strata be supported by pillars of coal. The stability of the pillars is a major safety concern. One of the factors which affects the strength of coal pillars is the intensity and nature of discontinuities in the coal seams. Current design methods for pillars assume that al the coal seams have equal strength and are equally disturbed by natural discontinuities, resulting in over-designed pillars in some cases and potentially unstable pillars in others. Research was carried out to determine the nature of discontinuities in coal seams and to assess their potential effect on pillar strength. It was found that large variations exist in the intensity of discontinuities in the different coal seams being mined. In addition, numerical model studies showed that the discontinuities could significantly reduce pillar strength if the width-to-height ratio of the pillars is small, but the effect decreases as the width-to-height ratio increases.

Jan 1, 1997

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 P. N. Vernon

Ausmelt top entry submerged lance technology offers a cost-effective means of carrying out a range of base metal smelting operations with minimum impact on the environment. The system is capable of using a range of fuels depending upon local costs. Due to the intense, localised reaction zone, high energy efficiency is obtained and the physical size of the plant is relatively small compared to that of most competing technologies. Capital cost can thereby be minimised. The furnace is well enclosed, such that fugitive emissions and ingress of diluting air to the gas stream are both minimised. The oxygen potential in the slag can be varied over a wide range such that the system can be applied in both oxidising and reducing duties. Following a general description of the technology, the paper discusses Ausmelt plants already in operation. The application of the technology for the provision of additional smelting capacity, for the improvement of converting operations and for slag cleaning is then described. A brief explanation of how these processes could be applied at southern African smelters is given and the paper closes with an assessment of novel Ausmelt applications for this geographical region, such as zinc recovery from sulphides.

Jan 1, 1997

By H Zimba, S Sondashi, M Chitambo

By the time a reagent is finally accepted by a mine for use on its plant it could have gone through several screening and evaluation stages. These stages may include laboratory and plant evaluation testwork. This paper outlines the steps that were followed to select, design and implement a frother for KONKOLA COPPER MINES PLC Nchanga Copper Concentrator in Zambia. It discusses initial frother screening work conducted at the Betachem metallurgical laboratory and the subsequent laboratory screening testwork conducted at Nchanga Concentrator. A modified Bikerman test method is discussed which was used to design a frother for the Nchanga flotation plant. The paper also gives an account of several plant scale trials conducted on Nchanga flotation plant and discusses the plant results, frother consumption patterns and some commercial concerns, before the product was finally accepted by the mine.

Jan 1, 2007

By Peter Voulgaris, Allan Haines, Diane Walker, Ian de Bruyn

The Oyu Tolgoi porphyry gold and copper project is located in the south Gobi region of Mongolia. The Ivanhoe Mines project has the potential to become a long-life copper and gold producer that could rank among the largest in the world. There are five deposits which cover a strike length in excess of 6.5 km, from south to north they are named South Oyu, Southwest Oyu, Central Oyu, Hugo South and Hugo North. The first three, collectively known as the Southern Oyu deposits, are planned to be mined by open pits, whilst extraction of the deeper Hugo deposits is planned using block caving techniques. The pits will have diameters of approximately 1000m and a maximum depth of 550m. The geological environment consists of a sequence of porphyritic augite basalt, dacitic tuffs and sedimentary rocks that have been intruded by several generations of porphyritic quartz monzodiorite and numerous post mineralization dykes. Several major faults cut through the southern deposits juxtaposing the relative position of the stratigraphy. The geotechnical investigation for the Oyu Tolgoi Open Pits was conducted in three distinct phases of increasing complexity: scoping study; advanced scoping study and feasibility study. Each phase consisted of data collection, interpretation and analysis designed to progressively develop 3D geotechnical domaining for the empirical, structural and numerical evaluations. The development of the geotechnical design parameters for these green fields open pits posed many technical challenges, brought about by the conditions associated with a lithologically and structurally complex environment. The design work focused on the optimization of the pit geometry to conform to equipment selection and blasting characteristics. Limiting bench stack heights were derived from the influence of major structures. The overall slope angles in each pit sector were developed around the requirement for haulage ramps and geotechnical berms. This paper describes each of these aspects and the methodology used to address the integration of the geotechnical characteristics with the mining environment.

Jan 1, 2006

By T. R. Roy

A prediction model, developed by Central Mining Research Institute (India) for evaluation of fire risk rating of underground coal mine panels in bord and pillar working in respect of their proneness to spontaneous heating, is presented in this paper. The concept used in this model is innovative and user friendly. This model may be applied to a panel where extraction is carried out using any of the techniques: i) depillaring with formation of small pillars as final operation, ii) extraction by broadening of galleries, iii) depillaring with hydraulic sand stowing, and iv) depillaring with caving. Here, major fire risk parameters are short-listed and divided into three broad groups in accordance with the nature of their contribution to the spontaneous heating of a mine panel. The paper describes the procedure for estimating the fire risk rating of individual groups using separate objective type models developed for this purpose. Then it evaluates the overall fire risk rating of the panel by combining the fire risk ratings of all the three broad groups. The model is tested with the field data collected from different collieries spreading across the country and with the laboratory data for critical assessment of fitness. Keywords : prediction model, fire risk rating of panel, spontaneous heating of coal, underground panel, bord and pillar working.

Jan 1, 2003

By P. A. Olubambi

The leaching of zinc and copper from Nigerian bulk sulphide ore with sulphuric acid in the presence of hydrogen peroxide was studied. The aim of the study was to investigate the effectiveness of hydrogen peroxide as an oxidant for the sulphuric acid leaching of zinc and copper from a complex sulphide ore. Distribution of elementals within the various particle sizes was initially determined by ICP-OES and XRF to provide a basis for explaining the dissolution process. The effects of concentration of hydrogen peroxide, particle size, stirring speed, and leaching time at a constant temperature of 298K were studied. There were variations in elemental and mineralogical composition within the different sizes. The concentrations of zinc and copper reduced as particle size decreased while silica, sulphur, iron and lead contents increased. Dissolution results showed that the leaching rate of copper was lower than that of zinc. The highest recoveries of zinc and copper were obtained at a leaching time of 180 minutes, stirring speed of160 rpm, particle size of 75 µm and a concentration of 1M H2SO4/1MH2O2. It was observed that the leaching rate of zinc and copper increased with increasing hydrogen peroxide concentration. Increased stirring speed had a negative leaching effect as it promotes hydrogen peroxide decomposition. Keywords: Nigerian sulphide ore, zinc, copper, hydrometallurgy, sulphuric acid, hydrogen peroxide.

Jan 1, 2006

"Investment in diamond exploration has been declining over the past decade, in spite of positive long-term industry fundamentals and a growing interest in diamonds as an investment category. The lack of new significant discoveries in recent years has eroded investor confidence, yet no new discoveries are possible without investment in exploration. Junior ‘mine finders’ have been the hardest hit. Their agility, tenacity, and appetite for risk are not sufficient to attract the funding required, even at the greenfield stage. Developing new discoveries into mineral resources can be crippling without solid financial support. Junior incubators could play a crucial role, especially at the project evaluation stage – but where are they? Alternatives to traditional funding mechanisms have become available, many still untested in the junior diamond exploration space. Valuable lessons can be drawn from the past and used to inform emerging new strategies. IntroductionDiamonds are the ultimate expression of love. Their ancient and timeless allure continues to influence consumer emotions and behaviours across continents, cultures and age groups. Analysts are predicting a sustained supplydemand shortfall in the years ahead which will trend diamond prices generally upwards. With positive long-term industry fundamentals, one cannot help but wonder why funding for diamond exploration and development projects is so scarce.Investment in exploration across commodities – including diamonds – has been declining for a number of years, reaching a historic eleven-year low early in 2017. The lack of major diamond discoveries in recent years has done little to strengthen the case for investing in diamond projects, yet no new discoveries can be made without investment in exploration.Global estimates of known carats in the ground stand currently at 2.5 billion carats, which equates to around 18 years of production at current levels of 140 million carats (mct) per annum. Sustainable replenishment of depleting diamond resources is possible only through the development of new discoveries. This is what junior explorers are best at – but they need investors to fund their evaluation activities from early in the project development continuum."

Feb 1, 2019

By C. Musingwini

The South African mining industry continues to be a major source of employment at a time when at least 25 per cent of the working age population is unemployed. At the same time the industry faces a skills shortage in many of the disciplines necessary for its future health. The University of the Witwatersrand, University of Pretoria, University of Johannesburg, and University of South Africa have historically produced mining graduates for the South African mining industry with any shortfall being met by the recruitment of overseas graduates. More recently, the global shortage of engineers and other mining industry professionals has seen a reversal of this trend and a very significant emigration of well-educated and highly skilled personnel. The traditional career path for mining graduates is in production and mine management. However, there is the parallel (and possibly more pressing) need for specialized skills in such fields as ventilation, rock engineering, mine planning, mineral resource evaluation, and mineral asset valuation. Chronic shortages in these essential areas continue to hamper the development of the industry and may well frustrate its ambitions to be safe, healthy, and profitable into the future. The permeability of skills across sectorial boundaries within the mining industry requires that skills shortages in the platinum sector are not looked at in isolation, but within the context of the entire industry. This paper reviews the efforts being made by the universities, at both undergraduate and postgraduate levels, to meet the needs of the South African mining industry in terms of the required numbers and the range of specialized skills.

Jan 1, 2013

By R. C. W. Webber

Mining up to depths of 5 000 m would be a world first and, accordingly, no previous experience in the determination of acceptable heat stress limits, criteria or indices is wholly applicable. However, some South African gold mines are already operating at depths beyond 3000 m and much of the knowledge gained in reaching and working at such depths will be helpful in making adequate provision for acceptable environmental control at the greater depths being contemplated. Accordingly, it is necessary to take cognisance of the industry?s experience in deep-level mining and of standards and regulations already established in South Africa and elsewhere in order to ensure acceptable working conditions and control standards, that compare favourably and defensibly with those in other mining industries. The local and international use of heat stress limits, criteria and indices were investigated as it was necessary to determine to what extent any other indices, limits or criteria would be applicable to South African deep mine conditions. In addition, it was necessary to establish whether there was a single heat stress index that could be used for South African ultra deep mining conditions. It was found that an appropriate combination of heat stress indices would be required in planning for and ultimately controlling thermal conditions in ultra-deep mining. The depths being contemplated and the concomitant potential heat hazard present too great a risk for reliance on a single environmental component of heat stress, such as wet-bulb temperature at present in common use locally. The study recommends that a heat stress index, preferably Air Cooling Power (ACP), be used to design an ultra deep mine?s ventilation system and that wet-bulb temperature be used to monitor and control the system once it is implemented.

Jan 1, 2003

The Gordonsville Operation of Pasminco US Inc. along with the Center for Advanced Mineral and Metallurgical Processing (CAMP) at Montana Tech studied, developed and implemented a pilot-scale hydrometallurgical facility for the industrial recovery of germanium and gallium. This paper describes the joint testing and engineering programme that culminated in this successful process.

Jan 1, 2008

By H. Kotzé

Ticor SA began with a detailed feasibility study in 1995. The Hillendale mine (situated between Richards Bay and Empangeni) and mineral separation plant were approved in 2000. The smelter, just outside Empangeni, consists of two 36 MW DC arc furnaces that were commissioned in 2003. Experiences gained during the initial commissioning of the furnaces proved valuable in later commissioning work, as shown by the increase in ramp-up rates. The capacity of the plant is 250 kt/a TiO2slag and 145 kt/a of pig iron.

Jan 1, 2006

By M. A. Amarante

Beneficiation studies were conducted on a Portuguese feldspar ore, in order to obtain final products capable of being used in the ceramic industry. A simple scrubbing operation is enough to break the lumps in the feed. The ore deposit contains ca 35 x 106tonnesfrom which, by screening, three main products could be obtained. This paper focuses on the beneficiation of the 500/74 µm fraction, which constitutes about 27% of the ore, assaying 9.42% Al2O3,equivalent to approximately ca 46% feldspar, with a mean iron content of 0.29% iron oxides. Magnetic separation and froth flotation testwork was carried out, in order to decrease the iron contamination and increase the feldspar content. Magnetic separation alone decreased the iron content of the feed to values between 0.04 and 0.08% iron oxides with an average yield greater than 90%. Flotation with HF, provided a feldspar recovery of 45?46% with a concentrate assaying 17.6% Al2O3. The use of H2SO4, gave a recovery of 35?36% of feldspar concentrate, assaying 16.1% Al2O3. However, economic and environmental advantages of using sulphuric acid may compensate for the lower mass recovery. The iron content of0.12% iron oxides in these concentrates, could be reduced to 0.04?0.05%, by further magnetic separation.

Jan 1, 1997

By A. Moss

The Palabora Mining Company has successfully extended the life of its operation by developing a 30 000 tpd block cave underground mine below the now closed open pit. The process of transitioning from surface to underground mining has been technically, operationally and managerially challenging. This has been due to a number of factors, in particular, the development of a block cave in a very competent rock mass. The competence of the rock mass is clearly demonstrated in the open pit that preceded the block cave, one of the steepest deep open pit excavations in the world. With cave breakthrough, however, the pit was ?instantaneously? deepened by 400 m causing a major failure of the north-west wall involving close to 100 Mt of waste material.

Jan 1, 2006

Water represents 80?85% of the volume of mineral pulp processed in flotation circuits. Imperatives for a more detailed focus on circuit water quality and its control have come from increasing requirements to use relatively impure primary water supplies (e.g. high salinity, treated sewage) and high proportions of recycle from tailings dams, thickener overflows, dewatered and filter products. An integrated methodology for examining process water quality and its effect on minerals separation has been developed coupled with minerals surface chemistry across the complete processing circuit. Unrecognised factors, including varying proportions of water streams (daily or hourly), colloidal precipitation, highly variable pH and Eh, reaction and dissolution of minerals, minerals surface layer coatings, residual reagents and their reaction products, and microbiological activity have been studied in eight mineral processing circuits. The methodology combines: solution survey and modelling; microbiological surveys; minerals surface analysis and modelling; and process response. It has been possible to match the predicted (model) pulp chemistry with that measured from surveys of the solution and mineral surfaces. Treatment methods have included: monitored and balanced stream combinations; organic species removal; flocculation and aggregation; induced precipitation; dissolved air flotation; ageing (oxidation, UV exposure); and chemical surface conditioning of minerals. Some specific achievements from the methodology applied in plant and laboratory testing, with examples from case studies, will be described.

Jan 1, 2001

By P. S. Paul

Mine accidents/injuries are complex and generally characterized by several factors, from technical to social characteristics. In this paper, a sociotechnical model for work injury in mines was developed and tested through structural equation modelling with application to case study mines in India. In total 14 variables were considered in this study. Most of the variables are not directly quantifiable. Instruments were developed to quantify them through a questionnaire survey. Underground mineworkers were randomly selected for the survey. Responses of 300 participants were used for the analysis. The analysis was conducted in three parts. Firstly, high-low plots were constructed to explore the variations in responses to the questionnaires by the accident involved (AG) and non-involved (NAG) workers. Secondly, a t-test was conducted to see whether the responses were significantly different for the two groups or not. The chi-square results showed significant differences of responses among the two groups. Finally, how these difference scan cause accidents/injuries in mines was hypothesized and evaluated using structural equation modelling. The measurement model of the Linear Structural Relations (LISREL) program was used to identify the latent constructs of the sociotechnical model. The structural model of LISREL was used to estimate the interrelationships among the constructs. The case study results showed that there is a sequential interaction among the sociotechnical factors leading to accidents/injuries in mines. Work hazards induce more job stress in the workers while social support mitigates the same. Job stress and safety environment predict the workers? job involvement. A worker who is more job-involved exhibits better safety performance, which in turn reduces work injury. The safety environment is shown to have a direct mitigating effect on work-related injury. The findings of this study clearly revealed that job stress and safety environment are the two key factors influencing work-related injuries in mines that need to be addressed properly through effective safety programmes.

Jan 1, 2005

By S. Badr, R. Mendoza, M. U. Ozbay, M. D. G. Salamon

ABSTRACT: The use of coal pillars at depth is fraught with problems due roof control difficulties and the possible occurrence of coal or pillar bumps. In the USA the largest and most important application of pillars at depth is in longwalling, where chain pillars are the customary supports of the multiple entry developments. At first, the chain pillars were designed using conventional approaches, where the principle is that the strength of the pillar should exceed the load imposed on it. Such approach to design led to larger and larger pillars at great depths, but instead of eliminating, it tended to aggravate the roof control problems. Eventually the idea was born that small sized yielding pillars, which have proved to be successful elsewhere, might provide the answer to this pressing problem as well. The aim of this paper is to study the modes of pillar failure at great depths, using two solution methods. The first of these comprises some elementary solutions obtained with the aid of a simplified conceptualization of the rock mass. This model consists of a strain-softening coal seam sandwiched between two stratified masses. The second approach utilizes FLAC3D, which is a commercially available three-dimensional numerical modeling software package. To gain a better insight, both the strain-softening and ideally plastic Mohr-Coulomb constitutive laws embodied in FLAC3D were exploited. As expected, the width to height ratio of the pillar has proved to be the primary factor that determined the behavior of the pillars. Narrow pillars fail in a stable manner without the occurrence of instabilities. Intermediate w/h ratio pillars under the appropriate loading conditions, may fail suddenly and may even collapse totally. Squat pillars do show the potential for sudden, coal bump like side failure, but because the remaining large width of the inner core, the ruble around the pillar provides sufficient confinement so as to reestablish stability. Finally, the study revealed that the traditional Mohr-Coulomb law does not provide a useful insight into the failure of coal pillars. RESUME: L’utilisation des piliers de charbon dans les mines souterraines de grande profondeur occasionne des problèmes due aux difficultés de control de plafond et possibles fracture ou explosions au niveau des piliers. Aux Etats-Unies d’Amérique, l’utilisation des piliers dans les mines souterraines de charbon comme moyen de support est considèrees comme étant la plus grande et la plus importantes des méthodes utilisée dans le ‘’ longwalling method’’ ou une série des piliers sont disposé de manière à supporter les multiple entrées d’exploitation de charbon. En premier lieu, cette série des piliers étaient construit de manière conventionnelle avec un principe basé sur le fait que le poids exerce sur les piliers doit être inférieur a la force que ces piliers exerce sur le plafond. Ce principe a conduit a ce que le volume des piliers augmente au fur et à mesure que la profondeur au de la mine augmente. Malheureusement, au lieu de résoudre le problème de support, ce principe n’a fait qu’aggraver le problème de contrôle de plafond. Eventuellement une idée s’est dégagé allant du fait que les piliers endommagés de taille moyenne qui se sont avérés être efficaces ailleurs, pourraient fournir un indice à ce particulier problème. Le but de cette recherche est celui d’étudier les différent types de ruptures qu’un pilier peut occasionner lorsqu’il est utilisé a grande profondeur, tout en utilisant deux possible méthodes. La première d’entre elle comprend quelques solutions élémentaires obtenues avec l’aide d’une méthode simplifié et conceptuelle de la masse de la roche. Ce modèle consiste à prendre en sandwich la bande de minerais de charbon entre deux masses stratigraphiques sans pour autant endommager le plafond. La seconde méthode nécessite l’utilisation du ‘’ FLAC3D’’, qui est un logiciel commercialisé disposant d’un modèle numérique en 3 dimensions. Dans le but d’obtenir

Jan 1, 2003

By J. V. Simmons

Composite rock mass failures involve intact rock material as well as fracture and shear on existing defects. Experiences from open-cut coalmining in the Bowen Basin of central Queensland are that failures of this nature occur suddenly with little warning, and are much more common than classical structurally controlled failures. Geological conditions and mining practices in the Bowen Basin are described. The circumstances of a sample of composite failures are described in detail in the paper. From this experience it appears that several aspects of conventional geotechnical investigation and design practice have not contributed significantly to either predicting or controlling the risks associated with sudden failures. These practices are described as myths for reasons outlined in the paper. On the other hand, the reality seems to be that high initial stresses and stress changes caused by excavation lead by a process of extensional deformation to a critical stress condition within the rock mass, and that sudden collapse follows when that critical stress condition can no longer be sustained. It is concluded that learnings gained from underground excavations in rock may be more applicable to open pit excavations than previously thought, and that the processes of prefailure deformation require more careful study if we are to develop more reliable risk management controls.

Jan 1, 2006

By R. M. Jara

This work evaluates and characterizes the impact of the support size and mining dilution of a block model in the operation and selection of equipment at an open pit mine. An exploratory analysis and geostatistical modelling of the grades assayed on a set of drill hole samples is performed, which allows constructing a grade model on a dense grid by means of a conditional simulation. The grades are then averaged to greater selective mining unit supports in order to proceed with the study and methodology. First, the metal-tonnage curves are used to analyse the loss of selectivity on the in situ resources caused by a change of support. Concerning the ore reserves and their mining sequence, defined in the pit optimization and analysis process, the same curves prove that the loss of selectivity is more accentuated. Second, the importance of the block boundary dilution produced during mining operations is assessed. Its value depends on the amount of ore in contact with waste, on the loading error of the equipment and on the ore loss/waste dilution criterion assumed by the planner. The dilution percentage and the differences between waste and ore grades become higher when the block size decreases. For these reasons, considering the dilution in the production plans makes mining a small support more constraining. An adequate delimitation of the orebody can improve the mining selectivity, leading to greater income. Finally, a study of the increase in mining cost that provides a zero difference in NPV between the different block size options is carried out, in order to determine the maximum increase in mining costs for which it remains profitable to mine at a smaller block size. Keywords: Mining selectivity, support effect, block boundary dilution, selective mining unit size, block model.

Jan 1, 2006

By C. Kasatuka

Globalization creates investment opportunities for enterprises around the world. Attracting foreign investment has been a key challenge for economic growth in developing countries. Corruption, political instability, armed conflict, and other internal problems affect foreign direct investment (FDI) inflows negatively. A framework of criteria provides a basis for comparing non-commercial risk (NCR) among twenty-three mineral economies. Countries competing for foreign direct investment inflows are ranked from least to most risky. This study compares Inward FDI Performance Index (IND) with NCR ratings in developing countries and shows that risk is increasingly mitigated by means of appropriately structured insurance. Given the option for countries with similar mineral potential, investors will generally invest in the country that offers lower non-commercial risk. Keywords: foreign direct investment, non-commercial risk, developing countries.

Jan 1, 2006