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By T. Feroze, B. Genc

"The ventilation of underground coal mines plays an important role in minimizing the risk of methane and coal dust explosions. The ability of ventilation, with the use of line brattices (LBs), to remove methane and coal dust in empty headings is dependent on the amount of air leaving the LB and entering the heading. The quantity of this air depends on the associated system variables, namely heading dimensions, settings of the LB, and velocity of air in the last through road (LTR). However, the exact effect of these system variables on the flow rate at the exit of the LB in an empty heading is not known. The installation of LBs in South African coal mines is generally carried out based on experience. This can result in overor under-ventilation and may increase the cost of providing ventilation or cause accidents, respectively. In this paper, using computational fluid dynamics (CFD), the air flow rate at the exit of the LB in an empty heading was estimated using full-scale three-dimensional models. The CFD model used was validated using experimental results Firstly, the settings of these three system variables were varied, the flow rates at the exit of the LB were measured, and finally the results were used to calculate the effect of each system variable. The outcome is a mathematical formula that can be used to estimate air flow rate at the exit of the LB in empty headings for any practical scenario.This paper will help the coal mining sector in South Africa by providing estimation models based on scientific reasoning for the installation of LBs, and will also serve academia as part of the curriculum towards educating future mining engineers."

Jan 1, 2016

By A. K. Biswas

Reviewer: R. H. Eric This edition is organized in twenty-three chapters, and contains exactly 500 pages including three appendices and an index. The first and second editions were published in 1976 and 1980 respectively, and both contained nineteen chapters. The second edition brought the operating data and process descriptions up to date. The third edition covers comprehensively the changes that have taken place in the primary copper industry over the past two decades. For example, reverberatory furnaces now make up only a third of the major primary smelting furnaces, compared with about three-quarters in the 1970s. Control of air and water pollution and recycling are given much more emphasis, along with novel and emerging technologies.

Jan 1, 1995

By J. Trcková

This paper describes the method of modelling rock mechanical problems on experimental models. Based on an actual experiment used as an example, assessment of the surface deformation due to undermining, the extensive possibilities of using a 3-D physical model and application results in practice are demonstrated. A special method of modelling the underground mine progress by using paraffin melting is presented. Keywords: undermining, subsidence of surface, 3-D experimental model

Jan 1, 2009

By R. R. M. Cousens, W. S. Garrett

SYNOPSIS The paper gives a background to the water hazards of the so-called West Wits Line and refers to some geological aspects of the Wonderfontein Valley in which the West Driefontein mine property lies. It describes the precautions taken against flooding during shaft sinking, development and stoping; these include cover hole drilling with cementation, provision for water storage in worked-out areas, installation of water tight bulkhead doors and pumping capacity well in excess of the mine's normal requirements. The plan of campaign adopted after the inrush took place is explained and the reorganization and expansion of pumping arrangements are discussed. When it became clear that the only means of saving the mine was to construct plugs to isolate the inrush while still maintaining all emergency pumping measures, the work was put in hand with the utmost dispatch. In considering the design of the plugs a number of major factors had to be taken into account. The most vital was the need for speed which was complicated by difficulty of access to the plug sites because of the huge volumes of water flowing in the drives. How this and other factors affecting plug design and construction, leakage problems, sequence of operations and final closure of the valves, were overcome is detailed in the paper. INTRODUCTION The inrush of water into the West Driefontein mine, the biggest gold producer in the world, which began on 26th October, 1968 and continued unabated for 23 days before the flood was stemmed, was unprecedented in the history of mining. Also unprecedented were the tremendous efforts and organization which made it possible to bring the situation under control and so save the mine from being lost for a matter of years. BACKGROUND Before going into details of how the situation was brought under control it is appropriate to consider the background to the event. The water problem on the so-called West Wits Line has been recognized for many years. As far back as 1912 the Pullinger Shaft, situated in the centre of what is now the Venterspost mine property, had to be abandoned because there were no means then available of coping with the large quantity of water encountered. To appreciate what vast quantities of water were involved, it helps to refer to some geological aspects of the Wonderfontein valley in which the West Driefontein property lies. The narrow tabular Witwatersrand gold-bearing beds, which dip at about 25 degrees towards the south, are overlain by a surface layer of dolomite which reaches a maximum thickness of some 4,000 ft at West Driefontein. A number of vertical syenitic dykes intersect the valley more or less at right angles to its course (Fig. 1). These dykes are about 150 ft thick on average and are spaced at about eight-mile intervals in the West Driefontein area. They penetrate both the dolomite and the Witwatersrand beds and as they are impervious to water they divide the valley into a series of large underground water compartments.

Jan 5, 1969

By R. G. B. Pickering, B. Ebner

The hard rock gold and platinum mines in South Africa have seen little development in the technology of mining. Holes are still drilled in the rock—though the latest water hydraulic rockdrills will complete that task in two minutes compared with the eight hours for hand drilling. Charging up is with far safer explosives and with available initiation systems it is no longer necessary to run up the face lighting each fuse. Movement of rock in the stope is predominantly by means of scraper buckets and scraper winches — these were first introduced in the 1920s.Support is still mainly rock, either in sit pillars or backfill, or alternatively wood. Just as themining process has changed very little it is hardly surprising that the productivity of mining is also relatively unchanged. Major efforts have been made to mechanize the mining process. However, most of the narrow reef mines where ‘trackless mechanized mining’ was introduced in the early 1980s have reverted to conventional mining. In the wider reefs mechanized mining is the option of choice, unfortunately most of the gold and platinum mines have very narrow reefs that are not suitable to’ off the shelf’ equipment. The move to introduce room-and-pillar mining into the narrow UG2reefs is at the expense of mining more waste with the reef, fortunately it appears that appropriate waste and reef separation processes are available. Room-and-pillar mining followed by long holedrilling and blasting of a narrow slot of reef out of the pillars currently appears to offer the best of both worlds—maximum reef recovery with minimum waste dilution. All these mining methods are still dependent on blasting to break the rock. The cyclic nature of mining by blasting places severe constraints on the rate of face advance that can be achieved and consequently the utilization of the invested capital. For narrow reef hard rock mining to break out of these constraints and to really make progress in the 21st century it is necessary to follow the lead of the soft rock mining industry and change the technology of mining. In the underground coal mining industry, coal cutting has been proved to be the most cost-effective solution. In narrow reef hard rock mining the future must be based on the development of non-explosive methods of rock breaking that in turn are integrated into continuous mining systems. Non-explosive so that the mining operation can be conducted on a continuous basis, with nodelays for the removal of blasting fumes. Continuous mining also maximizes the return on the capital invested in developing the mine. Rock cutting will define the stope width and that in turn will be designed to minimize waste dilution; it will also minimize damage to the hanging and create a safer environment. Mechanization makes it possible to automate the mining process and further improve safety by positioning the operators in a safer environment. This paper defines the work to evaluate cutting processes carried out by Sandvik TamrockVoest Alpine. The evaluation was in the UG2 and the pyroxenite and norite typical of the Merensky Platinum Reefs. A novel form of mining machine is proposed that will utilize existing technology. Finally the paper describes the interaction between Sandvik Tamrock Voest Alpineand Lonmin Platinum and the initiation of an agreement to develop and trial a prototype hard rock narrow reef mining machine.

Sep 1, 2001

By N. C. Joughin, H. Wagner

Research is a business activity, and is as different from other business activities as banking is from mining. attempting to use research to solve their problems, managers do not always recognize its unique features, are frequently disillusioned with the outcome. With a view to enabling managers to use research more effectively, an outline is given of the features of research as applied to mining. Types of research are distinguished, and stages in the research-and-development process are identified. The time-scales and resource requirements of the various types and phases of research are explained. Examples of research that have reached implementation in gold mining are given to illustrate the features mentioned. Practical and economic considerations are discussed, and pitfals and recommendations in the use of research are highlighted.

Jan 1, 1989

By G. Poropat, A. R. Guest, H. P. Grobler

At the De Beers Consolidates Mines operations it is common practices to perform Geotechnical mapping of the newly exposed faces in the waste and ore rock. The purpose of Geotechnical mapping is to quantify the in-situ fracturing of a rockmass that in turn is required during the planning and application of a mining method. Whether it is to determine slope angles, caveability, impact of blasting or support requirements. This mapping involved a cumbersome and time consuming procedure that requires individual examination and description of the natural inherent fractures exposed by mining. During highwall mapping in an open pit this can be a safety concern due to the duration of time spent below a highwall. The advantages gained through the recent introduction and application of SiroVision® allows safer mapping, an increase in statistical fracture population, archiving of rock faces and the more accurate reflection of the true mapping. This paper aims to describe in detail the application of the recently developed SiroVision®, photogrammetry software, to replace conventional face mapping. A De Beers Consolidated Mines, il est pratique courante de faire une cartographie géotechnique des tailles récemment exposées dans le rocher stérile ou minerai. Le but de la cartographie géotechnique est de quantifier la fracturation in-situ d’une masse rocheuse, qui sera nécessaire lors de la planification et application d’une méthode minière, que ce soit pour déterminer les angles des galeries inclinées, les possibilités de foudroyage, l’impact du dynamitage, ou les besoins en supports. Cette cartographie nécessitait une procédure longue et compliquée qui demande l’examen individuel et la description des fractures naturelles propres exposées par l’opération de mine. Pendant la cartographie de parois dans une exploitation à ciel ouvert, cette opération peut être dangereuse à cause du temps passé sous la paroi. Récemment, le lancement et application de Siro Vision apportent l’avantage d’une cartographie plus sûre, une augmentation des statistiques de population de fracture, l’archivage des tailles de roches, et le reflet plus précis de la cartographie. Le but de l’étude présente est de décrire en détail l’application du développement récent de Siro Vision, logiciel de photogrammétrie, pour remplacer la cartographie de taille conventionnelle. Bei den De Beers Consolidates Mines Operationen ist es gängige Praxis geotechnische Aufzeichungen des Taub- und Erzgesteins neu geöffneter Abbaustellen zu erstellen. Zweck dieser geotechnischen Aufzeichnungen ist die vor-Ort-Quantifizierung des Bruches der Gesteinsmasse, welche im Gegenzug während der Planung und der Anwendung einer Abbaumethode erforderlich ist, sei es um einen Neigungswinkel festzustellen, Abbaubarkeit, Auswirkung von Sprengungen oder Anforderungen an Unterstützungen. Die Aufzeichnungen waren mit umständlichen und zeitaufwendigen Prozeduren verbunden, die eine individuelle Prüfung und Beschreibung der durch den Abbau freigelegten natürlichen inhärenten Brüche, verlangten. Dies kann auf Grund des Zeitraumes der unterhalb einer Flözoberschicht verbringt wird zu einer Frage der Sicherheit werden wenn die Aufzeichnung einer Flözoberschicht im Tagbau erfolgt. Die Vorteile auf Grund der jüngst erfolgten Einführung und Anwendung der SiroVision® gestatten sichereres Aufzeichen, eine Zunahme in der statistischen Menge an Gesteinsbrüchen und eine akkuratere Reflektion der tatsächlichen Aufzeichnungen. Diese Arbeit hat zum Ziel im Detail die Anwendung der kürzlich entwickelten SiroVision®, eine photogrammetrische Software, die die konventionelle Abbauortaufzeichnung ersetzen soll zu beschreiben.

Jan 1, 2003

By S. A. Abdel Sabour

Strategic decisions in the mining industry are made under multiple technical and market uncertainties. Therefore, to reach the best possible decision, based on information available, it is necessary to integrate uncertainty about the input variables and model financial risk of the project?s merit measures. However, this provides few useful insights to decision-makers unless accompanied by modelling management responses to uncertainty resolutions. It is widely acknowledged that conventional decision-support methods based on static, no-change, discounted cash flow (DCF) techniques such as net present value (NPV) and internal rate of return (IRR) tend to provide inaccurate value estimates. This could mislead the strategic decision-making process and result in significant value losses. This paper aims to model financial risk related to uncertainty about market variables such as metal prices and foreign exchange rates. Other sources of risk that are related, for example, to geology and production costs are not considered in this work. The article outlines a flexible financial model that integrates uncertainty about market variables and management flexibility to react to uncertainty resolutions into mine project valuation using a real-options valuation technique based on Monte Carlo simulation. Significance of information generated from this simulation-based flexible valuation model to the strategic decision-making process is tested using an illustrative case study of a Canadian mining project. The project is a typical multi-metal, open pit mine that produces copper and gold. In this case, there are three uncertain market variables, which are: copper and gold prices and US$/CAN$ exchange rate. Financial valuations are carried out using both the conventional static DCF method and a flexible real-options model. In the flexible model, management flexibility to decide whether to go ahead with the next expansion or terminate production operations is integrated. Results show how the flexible financial model can enhance the decision-making process.

Jan 1, 2009

Professor N. S. Budavari holds a Dip!. Min. Eng. from the Technical University of Sopr on, Hungary, and a Ph.D. degree from the University of Newcastle-upon-Tyne, U.K. Mr J. J. Geldenhuys, Pr. Eng., is Divisional Manager Mining of Anglovaal Limited, being in charge of Prieska Copper Mines (Pty) Limited, Loraine Gold Mines, Limited, and Village Main Reef Gold Mining Company Limited.

Jan 1, 1983

By N. G. Cook, N. C. Joughin, A. J. A. White

The rate of face advance in the gold mines is between 3 and 10 m a month, with a median value of about 5 m a month; it follows that faces are blasted less frequently than is planned. There are many advantages in the use of short holes for stoping to give face advances of from 0,7 to 0,8 m per blast. This has the potential for so increasing the frequency of blasting that monthly rates of face advance could be improved significantly. Cleaning with face scrapers is too slow to permit the maximum achievement of a complete clean, drill, and blast cycle for each shift. Short-hole blasting, combined with the use of mechanical conveyors for face cleaning, offers the possibility of completing two such cycles each day, yielding monthly rates of face advance of up to 35 m. Experiments aimed at developing safe, unitized explosive charges well-suited to produce reliable face advances of 0,7 to 0,8 m per blast under a wide range of gold-mining conditions have been notably successful. A novel method of assessing the effectiveness of a blast based on the percentage of holes that leave socket lengths of 5 cm or less was used. Unitized charges of 60 per cent Ammon gelignite, 600 mm long by 25 mm in diameter, appear to be near optimal. The explosive is de-sensitized to obviate detonation by chance mechanical impact, but requires only a 6D detonator for initiation; it has good water-resistance. Means have been developed for producing these cartridges automatically, but the necessary machines will have to be built specially and the cartridges are not yet available in large numbers. A second experiment by way of an extended pilot production trial using these cartridges in holes 0,9 m long is now under way. Preliminary results indicate that drilling and explosive efficiencies and productivity are well above average, even though face scraping is being used. Unitized charges of this type are likely to prove even more advantageous when mechanical face conveyors come into use.

Jan 1, 1975

By J. McPherson

In order to add value to South Africa?s gold reserves AuTEK, a joint venture between Mintek and Anglogold-Ashanti, was started in 2000 with the aim of developing new industrial uses for gold. Accordingly gold catalysts are being made in kilogram quantities by Project AuTEK and sold toend users and other interested parties under the trade name AUROliteTM. Although these materials are optimized for use in CO oxidation applications, demonstration of appropriate activity, selectivity and durability in both liquid- and other gas-phase reactions has been shown1. The review below highlights the recent use of these materials, and other gold catalysts, in reactions of commercial interest.

Jan 1, 2009

By Nareetsile S., J. Kabwe

In the past few years Orapa and Letlhakane Mines have investigated various new technologies to enhance and improve production. The goal has been to improve productivity, reduce operating costs and make the mines more profitable The advent of Global Positioning Systems (GPS) in the early ’80s brought about the realization of this concept. Orapa and Letlhakane Mines started using GPS in 1999 and it is now used atLetlhakane mine for surveying, vehicle tracking and dispatching and for floor control system. Orapa Mine uses GPS in surveying, floor control and drill navigation. It will also be used for vehicle tracking and dispatching in mid-2001 following the installation of a fleet management and control system. The introduction of GPS at both Orapa and Letlhakane mines have improved productivity and reduced operating costs in the areas of drilling, topographic survey and floor control. In vehicle tracking and dispatching GPS has allowed for real-time information management for timeous decision-making which optimized fleet run time hours.

Sep 1, 2001

By A. J. Roets

Despite its growth over the years, necessitating ever¬larger office accommodation, the Gold Fields group changed its head office address in Johannesburg only twice in 94 years. The first move was at the turn of the century, from the then select suburb of Doornfontein to the corner of Fox and Simmonds Streets. The second move was in the thirties, from that address-now the Reserve Bank building-to the well-known address of 75 Fox Street. With the advent of the first mines of the West Wits Line by the end of the thirties, 75 Fox Street proved too small, and the eastern section of the Commissioner Street side of the present head office was added on. In the fifties, when space once more became a serious problem, the old Exploration building was purchased and demolished, and the present west wing on Commissioner Street was built on the site. In the early seventies, cramped conditions again made life difficult and, despite a reorganization of the interior layouts, the need for expansion remained critical. Eventually, the adjacent Hollard Place and parking area became available, and plans for an extended new building complex could he considered. The building project was

Jan 1, 1985

The compilation of the sampling nomogram is an essential tool in the optimization of a sampling protocol and allows the operator to track the change in relative variance of the sampling error (the Fundamental Sampling Error) during steps of comminution and mass reduction in the process of recovery of the aliquot for analysis. The data required for the compilation of the nomogram are centered on the sampling constant K and the exponent, alpha (a), of the nominal fragment size. Five methods for establishing K have been identified, but two of them, the duplicate sampling analysis (DSA) method and the heterogeneity test (HT) method purport to provide such a constant. The step by step procedure for each of these two methods was examined using broken ores from three mines, Mponeng mine, Kloof mine and Lily mine. Two of these mines (Mponengand Kloof) are typical Witwatersrand-type gold mines, while the third is an Archaean-type, shear related gold deposit situated in the Barberton Greenstone belt. The results suggest that the factor K derived using the heterogeneity test is very accurate, but applies only to a single size fraction in the spectrum of comminuted materials. The calculation of gold grain sizes using this method appears to be too small and does not conform with the results from detailed mineralogical studies. The factors K and alpha derived using the duplicate series analysis, are appropriate for use across a wide spectrum of comminution sizes and also provide realistic gold grain sizes, comparable with the equivalent circular diameter of gold grains identified in mineralogical studies of the ores.

Jan 1, 2009

By M. J. U. T. Van Wijngaarden, R. J. Dippenaar, P. M. Van Den Heever

Some of the important properties of solid electrolytes that influence the performance of electrochemical oxygen probes are discussed in the first part of this paper. It is shown that accurate and reproducible measurements of oxygen in liquid steel are possible with commercial oxygen probes only if great care is exercised in the make-up of the chemical and phase composition, as well as the microstructure of the solid electrolytes used in these probes. To prove this premise, the second part of this study reports on the results of an experimental evaluation of new commercially available oxygen probe. An evaluation of the solid electrolytes used in this probe indicated that the consistency of the chemical composition, degree of stabilization, and microstructure of the electrolytes used are well controlled. The successful application of this particular oxygen probe under industrial conditions was confirmed. It was also found possible to make reliable and reproducible measurements, with acceptable uncertainty, by proper handling of the probe. Some recommendations are made as to the interpretation of the e.m.f. response curve and the use of the electronic processing unit supplied with the probe.

Jan 1, 1987

By L. A. Vermeulen, D. D. Howat

The use of pebbles as the medium in the grinding of quartz gravel in a laboratory mil provided experimental data that were used to quantify the relationships between the feed rate of ore to the mil, the fineness of grind of the product, and the wear rate and consumption of the grinding medium. Fineness of grind is expressed as the inverse of the harmonic mean size, a quantity that is calculated from data obtained by sieve analyses. The commonly used criterion for fineness of grind (the percentage of material smaller than 75 µm in the mil product) is shown to corelate approximately linearly with the inverse of the harmonic mean size. An increase in the feed rate was found to cause the harmonic mean size of the product to increase linearly, Le. the relationship previously found for metalic grinding media is applicable to al grinding media, irespective of shape or composition. Simple expressions for the consumption and wear rate of pebbles are derived from the experimental data, and are shown to be functions of the feed rate. The expression for wear rate is a monotonicaly increasing function, while that for consumption is a hyperbolicaly decreasing function of the feed rate. In contrast, a linear relationship was found between the rate of wear of the grinding medium and the rate production of fines. The expressions that were previously developed in relation to the use of metalic grinding media are shown to be equally applicable to pebble milling.

Jan 1, 1988

By P. R. Jochens

It is interesting to note that, when the Technical Programme Committee-Mining first decided on this particular topic for a colloquium, the proposed title was different in that it used the words 'rising price of gold'. The very fact that the title was reworded to use the words 'fluctuating gold price' highlights the problem that faces the South African gold-mining industry.

Jan 1, 1981

By R. Yi

The determination of the optimum cutoff grade for a surface mine may be very different from that of an underground mine because a selectable mining method may be used in the latter case. A review of research into the theory of cutoff grade is made and then a new method, based on Optimal Control Theory, is presented. This method uses a Hamiltonian function to assist in obtaining the solution. It is shown that the life of a mine can be divided into three parts: a beginning period bf planning before mining; an intermediate period when both an average price and market information are used continually to adjust the cutoff grade; and, a final period when the main consideration is the current market situation.

Jan 1, 1987

By M. H. Kirchner

Trackless mining at Thabazimbi Mine by M. H. KIRCHNER*. Pr. Eng.. B.Sc.. B.Sc. (Elec. Eng.}(Stellenbosch). Dip. Mining (Pta.) Certain aspects ?f the' methods used in the exploitation, by sub-level caving, of a wide, tabular, steeply dipping orebody are described, reference being made to the use of modern mechanized equipment. Statistics relating to production and labour, as well as some geological details, are given.

By M. H. Kirchner

Trackless mining at Thabazimbi Mine by M. H. KIRCHNER. Pr. Eng.. B.Sc.. B.Sc. (Elec. Eng.)(Stellenbosch). Dip. Mining (Pta.) Certain aspects of the' methods used in the exploitation, by sub-level caving, of a wide, tabular, steeply dipping orebody are described, reference being made to the use of modern mechanized equipment. Statistics relating to production and labour, as well as some geological details, are given.