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By H. G. Mosenthal

In any mining enterprise, the extraction of the ore from the orebody is of vital importance. This activity is stoping. The gold mines of the Witwatersrand and its extensions in the Klerksdorp, Welkom, and Evander areas form the most extensive goldfield in the world. This address reviews stoping technology and improvements in this technology since the end of the Second World War. Although the reefs that make up the Witwatersrand orebody are uniquely extensive, they are not suited to mechanized mining. This is due to a number of factors such as the depth of the orebody, its narrowness, and the hardness and abrasiveness of the quartzite forming the orebody. The most notable improvements in stoping technology have been brought about because of our beter understanding of rock-engineering problems. This has resulted in beter layouts, stoping geometry, systems of aleviating rock stresses, and support systems. It has enabled the industry, at ever-greater mining depths, to maintain and even increase productivity. These improvements, based on rock engineering, have significantly reduced the accidents due to rockbursts. There are many diferences between today's stoping and that practised forty years ago. Panels are shorter, concentrated mining has superseded bench mining, and the support systems are certainly better. Yet the face scraper is still used extensively, as are pneumatic rock drills. Some innovative stoping systems that have given rise to improved productivity are discussed. Explosives technology has shown spectacular advances during the period under review. Sadly, our local industry has had little to do with this research and development, but has been most adaptive in using the new products on offer.

Jan 1, 1990

A. H. Mokken: I am pleased to have been given this opportunity to make a contribution to Dr Muller's paper tonight. The reason for this is that, at one stage in our careers, we were associates in the same undertaking. Dr Muller, then fresh from University, with a degree in pure science, had just stepped onto the first rung of the ladder, which, it was then thought, would lead him to a career in gold extractive metallurgy. However, endowed with an enquiring mind and conscious of a lack of fundamental training in general metallurgy and engineering, he felt a need for further academic study. To meet this need and, more importantly, to meet the necessary finances, he found his opportunity in steel. Armed with a bursary, he bade farewell to gold and proceeded overseas, to the University of Sheffield, to train as a steel metallurgist. The outcome of these academic efforts, which were followed by assignments in the steel industry and a further period at Sheffield, is the man we have listened to tonight-a highly qualified metallurgist who has displayed a sound knowledge of his subject. In choosing Sheffield, Dr Muller became associated with a steelmaking centre of world renown, a centre usually credited with the first systematic production of alloy steels, as far back as the 18th century. Since that time, great advances have been made in the production of alloy steels and this is especially so in the last decade or two, when major developments in civil, mechanical, electrical, aeronautical and nuclear engineering have been made possible by the development of steels with improved properties. In spite of spectacular advances in the technology of non-ferrous alloys, plastics and other materials of construction, steel has maintained its role as a pre-eminent material for engineering use. With the gradual accumulation of data on the properties of steels, and the use of thin film electron microscopy, to study the behaviour and characteristics of such phenomena as dislocations in metals and other microstructural features, the physical metallurgist appears to be approaching the stage of an exact understanding of such phenomena as strength, ductility and brittleness-a knowledge which could lead to close control of such properties and, therefore, to the attainment of the highest goals. An interesting example, illustrating the use of fundamental principles, based on physico-metallurgical research, is the development of the maraging steels developed by Bieber at the International Nickel Company. These steels have met the extreme technological requirements of the space age by providing the material for the cases of large rockets in which qualities, such as high tensile strength, toughness, workability and weldability are most important. Attractive as they might appear to be in considerations of savings of weight, cost of erection, transport of materials and foundations, the use of high strength steels has been accompanied by special problems such as brittle fracture, hydrogen embrittlement, notch-toughness and fatigue. It has been found that high strength steels, which performed acceptably in conventional tension tests, were found to undergo failure, in a brittle manner, in service. Hydrogen embrittlement has caused spectacular failures at a fraction of the normal ultimate tensile strength, and a lack of correlation between fatigue and tensile strengths has diminished the advantages to be obtained from the use of high strength steel in some applications. A new approach to the selection of materials for engineering design has resulted from a consideration of these phenomena in which strength, as such, is no longer as significant as it was previously. Parallel with the development of high strength steel has been the need for suitable techniques for joining component parts and here welding has played an

By T. Ito, N. Tokashiki, H. A. Bilgin, Ö. Aydan, T. Akagi

This study is concerned with the electric potential induced by deformation, fracturing and sliding of non-piezoelectric geomaterials. In experiments, the acoustic emissions together with electric potential measurements were also measured in order to see how the so-called seismic electric signals are associated with new fracture occurrence and propagation and sliding in case of existing discontinuities. The outcomes of this experimental study may explain why such electric potential variations may occur during the fracturing and sliding of non-piezoelectric geomaterials. On the basis of these outcomes, their possible implications in geo-engineering and geo-science are discussed. Ce travail concerne 1e potentiel électrique produit par la déformation, 1a fracture ou le glissement du matériel géologique non-piézoélectrique. Aux expérimentations, on a mesuré 1es émissions acoustiques avec le potentiel électrique afin de constater la relation entre les phénomènes de glissement ou de formation et de propagation de nouvelles fractures le long des discontinuités existantes. Les résultats de ce travail expérimental expliquent pourquoi de telles variations de potentiel electrique se produisent durant le glissement ou la fracture du matériel non-piézoélectrique. Sur la base de ces résultats, on a discuté de leurs éventuelles implications dans les domaines de 1a géologie et de 1a géo-ingénierie. Diese Studie befasst sich mit dem elektrischen Potential das durch die Deformation, Bruchbildung und Gleiten von nicht-piezoelektrischen Geomaterialien induziert wird. In Experimenten wurden die akustischen Emissionen zusammen mit elektrischen Potentialmessungen gemessen, um zu sehen, wie die so genannten seismischen elektrischen Signale mit neuer Bruchbildung und Ausbreitung sowie Gleiten im Falle von vorhandenen Diskontinuitäten verbunden sind. Die Ergebnisse dieser experimentellen Untersuchungen könnten erklären warum elektrische Potential Schwankungen während der Bruchbildung und dem Gleiten von nicht-piezoelektrischen Geomaterialien entstehen. Auf der Basis dieser Ergebnisse, wurden ihre möglichen Implikationen in Geoingenieurwissenschaften behandelt.

Jan 1, 2003

By D. Borman

The location of underground positions in mines has usually fallen to their survey department's. Their usual tasks include: ? installation of a high-precision peg network like the National Survey grid as beacons ? offset measurements to the sidewalls, and sometimes hangingwall and footwalls, of development tunnels and excavations ? offsetting of stoping panels for the calculation of face ? advance and the square meterage of area removed. Other departments build their observations into the plans produced by the surveyors. If more precision is required, they ask the surveyors to `elevate' their points with a theodolite. Apart from the survey peg network and `elevations' these measurements are usually planer measurements suitable for producing plans, sections and projection sheets. When the only representation medium was a sheet of paper or transparency, this was perfectly suitable. However the development of CAD models of the workings has changed all this. Full 3D representation is not properly catered for in the tool sets in current use, and needless hours are spent converting analogue-type observations into digital form. The basic survey models need to be augmented by the observations of other disciplines that are also required to locate positions underground. These include: ? the need for geologists to plott their mapping and ? borehole logs into 3D space ? the need for samplers to position their sample points accurately because the geostatistical models are biased and inaccurate ? the need for stoping width recorders to position their thickness observations to prevent errant evaluation and bonuses ? the need for rock engineers to place their mappings into 3D to build true geotechnical models to manage geotechnical stresses ? the need for production officials to receive updated face ? positions during the month so that they can manage the ? production and utilize their resources properly. This paper covers a new method of positioning profiling points to a suitable degree of accuracy. I believe the method is sufficiently simple and cheap for all to use. Historical methods Platinum and gold orebodies, especially in South Africa, are generally narrow tabular deposits. This made them suitable for depicting on a 2D medium like paper. The determination of stoping or face widths was not a problem, as the ore is removed in a single stoping process. Such 2D representations could be easily positioned using tape offsetting between survey pegs or points tied in from survey pegs. Problems of dip were handled by using 'Stope Sheets' which chose a best fit projection for the whole area depicted or by using true dip section sheets for inclined tunnels. Rolling reef and potholes were the common areas of difficulty. Most mines now model their orebody and plan the extraction in computer graphics. This means that the representation of the current workings has to change to support this trend. It now becomes a truly 3D problem. Mining officials find it inconvenient to have their actual workings in single-line depictions while their orebody is depicted with top and bottom contacts and the planned tunnels in 3D shapes. Geological models which form the basis for the resource model and planning process are often out of date, as the updating process is slow. The geological mapping has to be plotted onto sections and plans. These are then digitized into graphics by a draughtsman and checked by the geologist. Only then does the interpretation and model update take place. Potential methods to create 3D 'Actuals' Global positioning systems (GPS) Surface mines have been blessed by the advent of GPS technology. These simple-to-operate pieces of equipment and compatible software make it possible for all types of mine employees to locate themselves, and therefore to locate their observations. GPS are often inexpensive and give an acceptable degree of accuracy. Only in deep pits or close to the highwalls are observations hindered. Such technology cannot however, work underground. Ground penetrating radar (GPR) GPR is reported to be very useful for estimating the positions of potholes and faults. However it is still considered as providing an estimate, not a definite measurement. GPR is good for seeing into solid rock, not into open spaces. Inertia reading devices Experiments with inertia reading devices have been conducted on the mines. They were the forerunners of GPS for military guidance systems, and were even used for city navigation in the early 70s. They do however work best with heavy or fast-spinning gyros. Anglogold Ashanti's attempt to use them were discontinued in the mid-90s when the developers asked for an additional few million rand for a device that would weigh more than 12 kg and have a limited operational life.

Jan 1, 2006

By J. F. Morrison, C. H. Wyndham, N. B. Strydom

INTRODUCTION The shovelling of rock in stopes is still a basic and important operation in many gold mines in the removal of gold-bearing rock from the stopes. There is, however, little factual knowledge of the factors which influence the the rates of energy expenditure and work output, and of the way in which variations in these factors, individually or in combination, affect the mechanical efficiency of the mine workers. What for example is the influence of different rates of shovelling, shovel loads and distances of throw? How does stope width and dip of the stope affect the mechanical efficiency of men shovelling rock? Recently a simple physiological test was introduced into the gold mining industry for classifying Bantu recruits into those capable of hard, moderate and light work. If this test is used to select only those Bantu mine workers who are capable of hard work for the task of shovelling rock in stopes then the rate of energy expenditure which could be expected from these men is 1.5 litres/min for the entire period of the shift. With an adequate knowledge of the influence of the various factors which affect the rate of energy expenditure of men shovelling rock in stopes it would be possible to set work standards for Bantu mine workers in stopes. This should be done in terms of the rate of shovelling, the shovel load and the distance of throw for any combination of width of stope, dip of stope, condition of foot wall and grade of rock in such a way that the resultant energy expenditure would be the 'optimum' that could be expected from the men but would be within their capacities for physical work of an endurance nature (that is, 1. 5 litres/min from the 'average' Bantu mine worker). Work standards could thereby be determined for the different stopes of a mine on a sound and systematic basis. In order to supply the information required a study was carried out by the Human Sciences Laboratory in which the work output and energy expenditures (in terms of oxygen consumption in litres/min) were measured on six highly trained Bantu mine workers under the following conditions: (a) rates of shovelling of 3, 4, 5, 6, and 10 shovels per minute. (b) loads of from 9 to 18 lb on the shovel. (c) distances of throw from 8 to 20 ft. (d) stope width of 28 in., 42 in. and 72 in. (e) dip of stopes of 0°, 15° and 30°. (f) rough and smooth footwalls and various grades of rock size. This paper gives the main results of practical importance of this study. Method The experiments were designed and conducted in conjunction with the Work Study Department of one certain underground conditions such as variable stope widths, stope angle, etc., were made available in a mine Surface Training School and suitable subjects were selected from the large number of labourers being put through the training school. Subjects Bantu recruits who had returned to the mine for a new contract and who had previous underground experience on shovelling were considered to be suitable as subjects for the experiments. The particulars of the subjects are given in Table I. TABLE I PHYSICAL CHARACTERISTICS OF SUBJECTS Weight Height Surface area Max O2 capacity Subject (Kg) (cm) (sq meters) (Litre/minute) A 71.5 167.3 1.80 3.5 B 61.5 162.3 1.65 2.8 C 63.0 164.1 1.69 2.4 D 66.5 167.4 1.75 2.8 E 70.2 164.6 1.77 3.0 F 77.8 173.1 1.92 3.8 Training The method of shovelling, accepted by the Work Study Department, was demonstrated to the subjects who then practised the movements with empty shovels, under the supervision of an instructor. After the technique was mastered, the men started shovelling rock and were trained for at least four hours per day to work at the higher shovelling rates. Training was continued for three weeks to enable the subjects to achieve a reasonable degree of physical training and conditioning. Shovelling method In both the kneeling and standing positions the subjects faced the pile of rock, grasped the shovel in the accepted manner and pushed the blade of the shovel into the base of the pile of rock, sliding the blade between the rock and the concrete floor. In the standing position (72 in. wide stope) the back leg assisted in the movement by pushing the knee against the back of the hand holding the shovel handle. In the kneeling position the elbow was tucked into the side of the body so that the muscles of

The theory of geostatistics covers a branch of .applied statistics aimed at a mathematical description and analysis of geological observations. Geostatistics can be used in pure geology (for example, for the analysis of trace elements in a metamorphic rock), in mineral exploration (for example, for the analysis of geochemical exploration data), as well as in mine valuation. This book is intended to provide a practical introduction to the theory of geostatistical methods of mineral evaluation. Over the years, various mathematical models have been developed to represent the distribution of values in mineral deposits. The simpler models are based on the assumption that the values are randomly distributed. Classical statistical methods, based on this assumption of the random distribution of values, are used to analyse mineral deposits to which these models apply or are assumed to apply. In all mineral deposits, however, one recognizes the presence of areas where the values are higher or lower than elsewhere. Also, the values of two samples in a mineral deposit are more likely to be similar if the samples are taken close together than if they are taken far apart. This indicates that there exists a degree of correlation between sample values, and that this correlation is a function of the distance between the samples. Models have been developed which take this correlation into consideration, with the degree of correlation between sample values being usually measured by the semivariogram function. In these models the fact that two samples taken next to each other will most probably not have the same value, must also be considered; even for very short distances the correlations are usually not perfect and a purely random component is present in the value distribution. The mathematical models will therefore assume the presence of two sources of variability in the values: a correlated component and a random component. Finally, one must consider the particular and very common case of mineral deposits in which the values present a systematic variation in space. This variation is usually referred to as a drift, or a trend. For example, the grade of an ore body may increase with depth of the ore, or it may decrease when one moves away from a central volcanic pipe. The earlier models did not give a satisfactory representation of drifts, and more complex models have been developed, in which three sources of variation are represented. These models are made up of: a deterministic component, a correlated component, and a random component. The deterministic component is used as a model of the drift. The correlated component explains regular changes in values which are not represented by the drift. The random component represents variations which cannot be explained by any of the above factors. The simpler models, based on the assumption of a single random component, will be described first (Chapter 2). The models based on the hypothesis of the superimposition of a correlated component on a random component, will then be analysed in detail. These models are most commonly used in the analysis of mineral deposits (Chapters 3-1 I). Finally, how to deal with the presence of a drift will be briefly described (Chapter 12). This book has been written essentially for students in mining engineering and for mining engineers who are interested in the background to the theory of geostatistics as well as its practical applications. The assumption is made that the reader has an elementary knowledge of statistics. Some knowledge of linear algebra is useful in part of Chapter 9, and is necessary to read Chapter 12. A proof is given of all the equations related to geostatistics, and which are not usually found in elementary textbooks on statistics. Understanding of these proofs is not necessary for practical application of the theory, and the reader may wish to skip them on a first reading, concentrating attention on the numerous simple practical examples given. Although the theoretical geostatistician will not find much new material in this publication, it is anticipated that he will develop some interest in the practical approach chosen to prove the various geostatistical equations. Many people and institutions contributed to the preparation and completion of this work. I am much indebted to Dr D. G. Krige and the Anglo Transvaal Consolidated In- vestment Company Limited, who gave me the opportunity to spend a considerable amount of time working on geostatistical problems, both theoretical and practical, during the time that I was in their employment. Dr Krige contributed greatly in developing my interest in studying both the theory and practice of geostatistics, always insisting that a correct balance be kept between theory and practice. I am grateful to Professor H. M. Wells and the Mining Department of the University of the Witwatersrand for inviting me to give lectures in a post- graduate course on geostatistics. The notes 1 prepared for that course became the foundation of the present work. I am also indebted to the Centre de Geostatistique of the École des Mines de Paris, where I received my first formal education in geostatistics during a summer course given by Charles Huijbregts, after many years of my lonely plodding through the published literature. Many graphs in the present volume are reproduced with the permission of the Centre de Geostatistique. The Department of Metallurgical and Mineral Engineering of the University of Wisconsin-Madison has also contributed in making this work possible, by allowing me to spend a considerable amount of time and resources in the writing, typing, and correcting of successive drafts. I am thankful to Lynn D. Kendall, who typed the entire manuscript under constant pressure.

Jan 1, 1978

By M. I. Brittan

Discussion Dr R. E. Robinson (Fellow): The author must be congratulated on a very meticulous and self-contained piece of work. It is indeed a pleasure to read a paper that is so clearly and systematically laid out, and where the conclusions and the testwork conducted have been so clearly described. The paper is complete in itself, which makes it very difficult for someone who is not intimately involved in the whole Torco project to make any comments on its content. However, two points that, strictly speaking, fall outside the scope of the paper are of considerable interest. The first relates to the particle size of the material treated. In the paper, the testwork is confined to one standard particle size (minus 60 plus 100 mesh). The essential feature of the paper is to indicate that the rate-controlling reaction in the whole segregation process is the rate of reaction of the ore particles with the reducing agent and the hydrogen chloride. One wonders, therefore, to what extent this relatively slow rate of reaction is affected by the particle size of the ore itself. One imagines that the reaction must take place by contact of the hydrogen chloride with the surface of the mineral particles, and it is reasonable to suspect that the rate of diffusion of the copper ions to the surface is a relatively slow process and is thus the limiting factor in this particular rate of reaction. It is possible, for example, that the improvement obtained, when the ore is subjected to reducing conditions before the chlorination, is due to a breakdown in the crystal structure of the original particle. This breakdown is brought about by the reduction and by the consequent increase in surface area available for reaction with hydrogen chloride. Can the author indicate whether any work has been done along these lines, and whether it has been established that the reaction depends on the surface area available? The second point relates to the application of this kinetic study to the actual operation of a Torco reactor. It was once planned to feed the sodium chloride, together with the reducing agent, into the top of the segregation chamber. In the paper, the author mentions that it has now been established that the segregation chamber behaves, to all intents and purposes, as a fluidized bed, and that there is, therefore, a rapid evolution of gas in the lower regions of the chamber, which, it is imagined, displaces the gas phase rapidly. Since the reaction between sodium chloride, water vapour, and the aluminium silicates in the ore is extremely rapid, one wonders how much of the hydrogen chloride produced is removed from the reaction zone before it has had time to react with the copper minerals. The extremely low consumption of sodium chloride (which is a vital feature of the Torco process) must depend on an extremely rapid circulation of the hydrogen chloride gas to all the ore particles in the segregation chamber. One wonders, therefore, if a system for the introduction of the sodium chloride into the bottom regions of the chamber might not result in even greater efficiency in the utilization of sodium chloride. ProC D. D. Howat (Fellow): All of us who have been concerned with the study of chemical reactions at high temperatures are keenly interested in kinetics and are well aware that this is not an easy study experimentally. Dr. Brittan is to be congratulated on the development of neat experimental methods and for his full discussion of the results obtained. Although the segregation process for the extraction of copper from oxide and silicate ores has been known for almost fifty years, the fundamental chemical and physical changes involved have been little understood and the fundamental data are very scanty. The work now in progress at A.A.R.L., together with that sponsored by the Anglo American Corporation in other research institutions throughout the world, is bound to produce new fundamental data and a much more complete understanding of this rather fascinating process. It is already apparent that some of the old and well-worn chemical reactions that were postulated to occur, just cannot take place in the way which was formerly accepted. Dr Brittan's work, carefully conducted and thoroughly analyzed as it has been, still leaves us with one great outstanding problem. The thermodynamic data and the possible reactions set out in Table I (page 281) of his paper leave us asking, in complete despair, how can copper be converted into a volatile chloride in the presence of HCl, CO and carbon at temperatures about 800°C? The thermodynamics all combine to show that copper should be reduced to metal as the first step in the process. This brings us right up against the second problem. If copper were reduced to the metal how would HCI convert it to the volatile chloride? On top of these problems is the unknown reason for the very high speed of reaction between CO, HCI and the ground copper ore. Still further into the region of the unknown is the reaction by which gaseous hydrochloric acid is produced in the actual process. Perhaps Dr Brittan is feeling grateful that he doesn't have to try to explain this reaction-at this stage of the research programme at least. The results very clearly show that both CO and HCl gas are essential for rapid production of the volatile copper chloride. Dr Brittan states that 18 minutes were required to attain 83 per cent extraction with HCl gas alone and this was reduced to 4 minutes when CO was

Jan 2, 1970

"I have been involved in the refractory industry for many years and at some time or another I have designed materials, tested materials, manufactured materials, installed materials, in fact I have done everything except actually chemically analyzed a refractory material.So I would not even begin to tell you how to analyse a refractory material. I'm sure everyone here knows more about chemical analysis than I do.However you could regard me as a customer with and perhaps the insights I have developed may help in putting the role of chemical analysis in the Refractories into perspective.For a start, let's take a step back and ask why we test refractories. The refractories handbook of the American Foundry Association gives four reasons:1. To determine appropriate specification.2. For quality control, to ensure conformance to specifications.3. To provide special property information not available elsewhere.4. For postmortem analysis to determine property changes in service and provideinformation that can point the way to better service.I want to discuss these points with regard to the role of chemical analysis and in particular the abuse of in house chemical analysis facilities. Let me talk first about detelmining appropriate specifications. Most refractory products are made from alumino-silicate raw materials.The phase diagram for alumino and silica is as follows:"

Jan 1, 2014

By S. M. Graham, G. Mellis

"The determination of the oxidation state(s) of an element present in a solid sample may be required for a number of reasons, including the assessment of the degree of reduction which has taken place during a multi-step production of a metal. In addition, possible flaws in a metal may result from small amounts of oxides included in the solid. The analyte of interest may be present as a major component of a sample of interest, or as a minor impurity - beneficial or requiring removal - in another matrix.Numerous methods have been established for the analysis of species in solution samples - for example, Fe2+ and Fe3+ by titration, Cr6+ by colourimetric means, etc. With appropriate knowledge of the solution being analysed, many of these methods are fairly straightforward, extremely reproducible and accurate. In those instances where the analyte in a solution is known to be in only one form, the analysis is even more straightforward, since it can be achieved instrumentally (by AAS, rCP-OES or rCP-MS, for example).However, the situation with respect to the analysis of solids is not as simple. Various techniques - such as X-ray diffraction - are routinely used by our mineralogists to obtain information about the various minerals present in solid samples, and thus about the oxidation states of the analyte elements present. However, these techniques usually give results that are qualitative, or semi-quantitative at best. They are also usually time-consuming and expensive. One of our colleagues at Mintek, Deshenthree Chetty, has done extensive work in developing a method for the quantification of manganese species in solids using mineralogical methods, and this is no small achievement."

Jan 1, 2014

"Chairman: Professor E. P. PFLEIDER Rapporteur: Mr P. R. JANISCHPapers:Optimum design of an open pit by D. A. PhillipsAn open pit design system for stratiform ore bodies by L. A. J. Pronk van Hoogeveen, J. R. Cutland and M. WeirAn open pit design model by R. H. Robinson and N. B. PrennThe Chairman in opening the session highlighted the current situation in the United States of America where some 85 to 90 per cent of all mining (except for coal) is done by open pit methods, and where some 40 per cent of the coal is mined by open pit. The South African industry is, of course, dominated by the deeper level underground gold mines; however, with the aid of an extensive open-pit technology developed in other countries, South African companies arc continuing to explore possibilities of open-pit exploitation of base mineral, coal and diamond deposits. Several successful ventures are already in operation at Phalabora, Optimum Colliery, Kimberley and elsewhere, and South Africa is undoubtedly benefitting in this regard by drawing on the experience of others.The papers of this session were therefore particularly pertinent, particularly when viewed in conjunction with those presented at an earlier South African conference devoted specifically to open pit mining.Two themes dominated the discussion which followed presentation of the three papers at this session. The first related to the practicability of using the reported techniques as a tool for management, and their acceptability as such to mine management. This was, of course, not peculiar to this particular session, but rather the major point of debate over the entire conference.The second theme concerned the reliability of the initial drill hole data on which any open-pit design must necessarily be based. This gave added emphasis to the problem of practicability, for no management is likely to accept an elaborate pit design unless confidence can be placed in the ore reserve assessment.In noting these two features of the discussion, it should be remembered that all the three papers dealt largely with design and pre-planning; there was an unfortunate lack of papers or discussion on the subject of controlling the day-to-day mining of open pits, and this is an area where the potential impact which can be made by the computer is even greater.In introducing his paper, Mr D. A. Phillips pointed out that it was concerned only with optimization, and that it therefore assumed, firstly, an adequate subdivision of the orebody into ore blocks characterized by grade, rock type, structure, etc., and, secondly, an acceptable forecast of costs and mineral prices in order to generate a suitable profit matrix. However, programs dealing with these problems for both massive, disseminated and stratiform ore bodies are available to Roan Consolidated Mines. The method of optimization which he had described had been used on a region split into 28 000 blocks, for which the program used three hours of C.P.U. time on an IBM 360/40 computer. The computer design had provided a three per cent improve¬ment on a normal design of the same area."

Jan 1, 2014

"Chairman: Mr R. A. PLUMBRIDGE Rapporteur: Dr D. M. HAWKINSPapers:The relevance of computer methods to the economics of the mineral industry by R: A. PerlmanDynamic control of a mining enterprise by R. G. CoyleAn economic model of the mineral sands industry by G. P. A. HoweMr M. Splaine, in opening the discussion on Mr Perlman's paper, asked whether the model, as fitted by data up to 1963, predicted the rise in the price of copper in 1967, and whether the model could be used to capitalize on short-term price fluctuations.Answering the second question first, Mr Perlman said that the horizon used is six months to one year. In the very short term the activities of speculators obscured the effect of the fundamental econometric variables. This effect, however, was removed if one moved to a longer term, say, quarterly. In 1963 the model had predicted a price rise in 1964 and 1965 and a drop in price in 1966. The rise in 1967 had been caused by a strike, and imponderables such as large strikes were difficult to include in the model since they were unpredictable. Model simulation can be used to show the effect of strikes on price and the effect of small strikes is small.Mr B. R. van Rooyen said that because models are both calibrated and tested on historical data a bias was introduced which gave rise to an overoptimistic estimate of the accuracy of the forecasts. To this Mr Perlman replied that there seemed to be no alternative to the use of historical data for calibrating and testing models, and thus little hope of avoiding the bias. A second point made by Mr. van Rooyen was that manage¬ment tended to be suspicious of complex models and that frequently more heuristic models were sufficiently accurate and preferable for investment decisions. He added that if management were not involved in the model building the econometrician might easily go astray, Mr Perlman replied that symbiosis between data analysts and users of the model was essential and that the experience of the practitioner must be reflected in the model.Mr M. R. Fuller-Good remarked that a clear understanding of future price trends was essential for effective capital planning, and asked, first, how one went from the compiled data on supply and demand to the determination of their effect on price, record, whether necessary data, for example, capacities, could be obtained timeously, and, third, when strikes restricted supply, whether stockpiling by consumers induced large price fluctuations."

Jan 1, 2014

By G. A. Wiebols, N. G. W. Cook, N. C. Joughin

Discussion R. E. Rarnes (Member): The original concepts and the pioneering work now brought to the practical test stage by the Mining Research Laboratory team deserve our highest praise. The authors of this comprehensive paper rightly stress the urgency of establishing the extent to which the apparent potential can profitably be realised in practice. It is to be hoped that adequate funds will be made available by individual mining companies, the Chamber of Mines and manufacturers to attract the necessary staff and maintain the high rate of achievement of the last two years. From the Seventy-Eighth Annual Report of the Chamber of Mines and its members we see that, in 1967, with a Working Revenue of R759.8 million from gold and R54.6 million pit mouth coal sales and with profits from gold and uranium and pyrite of R307.9 million, only R1.9 million was spent by the Chamber on all forms of Research. It is considered unlikely that the associated mining companies and manufacturers exceeded this investment expenditure. Assuming a total of R4 million spent by the industry on Research and Development, this is less than half of 1 per cent of sales of gold and coal. This percentage, so low in comparison to North America and Europe, is no worse than that of Exploration expenditure which, in 1967, with South Africa's total mineral production of R1,287 million, was estimated to have been R6 million (Pretorius 1968). In a primary industry with ever present depletion of ore deposits and with cost escalation, expenditure on Exploration and on Research and Development is not a risky luxury but a tactical obligation. The potential rate of return on research expenditure into rock breaking is high. Stores consumed by gold and coal mines, members of the Chamber of Mines, totalled R316.2 million in 1967. Except for purchased power costing R42.2 million the highest cost group was explosives, drills and drill steel totalling R33.8 million or 10.7 per cent of the total stores consumed. In the paper under discussion it is claimed that the low 'effective stoping width' should greatly reduce the likelihood of rock falls or rock bursts to the extent that permanent support can be dispensed with. Insofar as this narrow cut is only 12 in. in advance of the working area which, with a 10 in. channel, is unlikely to be much reduced in width from that achieved by current methods, this claim is not readily understandable. Were it to have been based upon the regional support gained from packed waste it would have been more acceptable. Pre-developed stope drives may give serious trouble at depth and for this reason it is questioned whether a stoping area can avoid periodic sub-development blasting-the spoil and fumes from which will interfere with the rock flow and continuous mining of the rock-cutter. If, in the mining method proposed by the authors, stope drives are cut as small as possible (6 ft by 6 ft) then 25 per cent of the total tons handled (excluding resued waste) and 5 per cent of the gold will be blasted conventionally in the stope. At this stage one cannot envisage tunnelling machines economically or practically capable of such work. The various methods described by the authors and subsequent contributors for breaking waste are most interesting. It was noted that the 'bull wedge' and 'explosives' in Fig. 1 of the paper were no further from the ideal point 'A' than was 'cutting'. The writer considers that the bold and imaginative steps taken by the Mining Research Laboratory Team, the mining companies and the manufacturers concerned will eventually lead to a successful rock cutting machine with universal application largely independent of rock type. This may take many years. In the meantime other methods of improving productivity of saleable metal by rock breaking teams should be investigated even if such methods have local applications only. In 1955 the writer conducted tests with a wire saw similar to those used in quarries in the Northern Transvaal and elsewhere. Jeppestown shale, the immediate footwall of much of the East Rand gold field, was cut at the rate of 6 in. per hour using sand, water and a special endless rope driven by a low h.p. motor. A hypothesis on its application was submitted to the Office of the Government Mining Engineer in 1955 and to other mining institutions in 1966 after the writer returned to South Africa. By inference, rope sawing was classed as less promising than other methods tested in the Orange Free State Goldfields (Parker 1969). With highly resilicified hanging and footwall quartzites this was not surprising and confirmed the writers findings when testing hanging wall quartzite from the East Rand in 1955. The relatively uniform conditions, the low strength, hardness, and silica content of the Merensky Reef platinum deposits (Gray and von Bardeleben 1969) and in particular, the existence of overlying Merensky pyroxenite (Cousins 1964) make this and the East Rand attractive areas for larger scale testing of wire saws. It is envisaged that in suitable rock types the 5/8 in. slot would be advanced down dip or down a minor dip. In undisturbed areas 'faces' of up to 200 ft in length could be cut several feet in advance of breaking which could then consist of light blasting to the second free face or some of the methods now being tested for breaking waste in rock-cutting operations. A wire saw is an inexpensive and simple machine which, in some areas, could make significant and early gains in rock breaking efficiency as well as in ground and stoping width control.

Jan 5, 1968

By A. L. Hinde, P. J. D. Lloyd, D. Hebden

The philosophy behind the design of a rougher cell for the handling of coarse feed and for the maximization of recovery within a given time is presented. The application of this philosophy in cells of 22-litre, 320-litre, and 3 m3 capacity is outlined, and the results of the process testing of these cells are given. In this testing, particular accent was placed on the recovery of water as a guide to the recovery of the finest size of particles, and the rate of recovery of various mineral species. It is concluded that a promising concept has been identified, but that further testing is needed for the firmer establishment of optimal operational parameters in a production environment.

Jan 1, 1983

By A. M. Starfield

Discussion J. de V. Lambrechts (Fellow): The author's paper is a brilliant follow-up of an earlier paper by Starfield and Dickson.1 I have no quarrel with Dr Starfield's computerization of a complex problem, but I do not believe that he is getting quite the right answers from his programme. My impression is that his predictions about wet bulb temperature increases in very deep mines are over optimistic; in other words, that it will be hotter than Dr Starfield predicts. This is putting my views in a nutshell. This is not the occasion on which to indulge in lengthy argument about the original paper by Starfield and Dickson, but the present paper is, after all, based directly on that earlier paper and if the one fails, the other cannot succeed. I did level certain criticisms at the first paper and cannot say that the authors' replies were very convincing. I do not think it is a sin to admit that I belong to the old school which believes in thorough field experimentation and practical trials and no amount of mathematical manipulation or physical theorizing, no matter how excellent, can make up for inadequate practical confirmation. This, as I see it, is still the crux of the matter. The original paper by Starfield and Dickson still rests on somewhat scanty practical evidence and I would be much happier if Dr Starfield's computer programme, based on the Starfield-Dickson model, had been checked against a large mass of observations in the practical mining situation. This is what both Wiles2 and myself3 had tried to do previously. What we lacked in mathematics and/or computer aids, I think the present paper by Dr Starfield lacks in practical substantiation. This is no condemnation of the author's paper which, taken by itself, is excellent but I think the final stage is still lacking, namely the bringing together of theory and empiricism in a manner acceptable to all. This may be wishful thinking on my part but I hope, within the next year or so, to come up with a modified Starfield-Dickson model in such a way that the computer answers will agree in the majority of cases with the few hundred field observations which are already on record. It might be a case of applying the proverbial 'Cook's Law' to the Starfield-Dickson model! REFERENCES 1. STARFIELD, A. M., and DICKSON,A. J. 'A study of heat transfer and moisture pick-up in mine airways.' J. S. Air. Inst. Min. Metall., 68, (5), 1967. 2. WILES, G. G. 'Wet bulb temperature gradients in horizontal airways.' J. S. Air. Inst. Min. Metall., 59, (7), 1959, p. 339. 3. LAMBRECHTS, J. DE V. 'Prediction of wet bulb temperature gradients in mine airways.' J. S. Air. Inst. Min. Metall., 67, (11), 1967, p. 595. R. Hemp (Visitor): Dr Starfield's paper has very effectively rounded off one particular aspect of the general problem of heat flow in mines. The ease with which this computer programme can be used to calculate temperature increases in horizontal airways must lead to its wider use in ventilation planning and, in developing this rapid method, Dr Starfield has indeed rendered a valuable service to the mining industry. One could consider further instances of heat flow in airways in which the availability of a rapid computer method would be desirable, e.g. the flow of air down a shaft, where there is an increase in temperature due to adiabatic compression, as well as an increase in virgin rock temperature as the depth increases. However, this particular case would not present any new problems and would merely require an extension of the exisitng work. I should like in this contribution to talk about an aspect of environmental control in mines which, I think, will become more important in the future. It is well known that wet bulb temperatures are subject to fluctuations underground. In some instances, particularly in stopes, the fluctuations, both with time and position, can be considerable. The theoretical work which has been carried out on temperature increases has been aimed at the prediction of mean temperatures, and no account has been taken of fluctuations around this mean. It is questionable whether this approach will, on its own, be sufficient, particularly when temperature increases in stopes are considered. The fluctuations in air temperatures underground arise from two causes. The first of these would be the fluctuations in surface conditions, and here one could list random, diurnal and seasonal fluctuations. The second cause is the multitude of things which vary in a mine and here one could list variations in air flow quantity, sources of evaporation, heat transfer from pump and compressed air columns and, particularly in the stope, variations in air flow patterns. Fluctuations arising from surface temperature variations should be amenable to calculation, and here one envisages figures relating the decay of temperature variation with distance to factors such as air flow quantity. Fluctuations resulting from changes in the mine are perhaps more difficult to tackle theoretically and the best approach could well be to analyse underground observations. In this connection, there is a good case to be made for the increased use of statistical methods in the analysis of underground temperature measurements, and it might be of value to look at current air-conditioning practice. When carrying out cooling load calculations for a particular location it is customary to use design wet bulb

Jan 11, 1969

By S. G. Mgenge, J. D. Steenkamp

Tronox Namakwa Sands operates two ilmenite smelters for the production of high-titania slag and low-manganese pig iron. Slag or metal is tapped from one of two product-specific, bi-level tap-holes. In this paper the refractory design specific to the tap-hole refractory layout is described, as well as practices for slag and metal tapping and refractory maintenance. Further developments planned are briefly described.

Jan 1, 2014

By D. Hanekom

Over the past couple of years, Anglo Platinum has made extensive use of technology within the core disciplines (geology, evaluation, survey, and planning) that collectively form part of mineral resource management (MRM). While these technologies were primarily developed to enable geology, evaluation, survey, and planning to carry out their daily tasks, with the main objective of supporting the mine?s production effort, they have also enhanced the disciplines? ability to produce the required outputs within the annual business planning cycle. Anglo Platinum has developed a very comprehensive business planning process, and these technologies play a vital role in enabling both the quality and quantity of inputs into the process, and also the value-add of the final product. This prompted a question regarding the practical application of the CADSMine software. If we changed our thinking in how we applied the software, would it be possible to further improve on the time taken to deliver a business plan? In changing the current planning approach, would we be able to further simplify the process? Is there a way to reduce the data generated in order to enhance the time taken to do reporting, as the CADSMine software is totally network dependent? Less data should equal faster reporting. This paper focuses on the practical application of the CADSMine software, and demonstrates the value-add to the business planning process that can be gained if the mine design methodology is changed from individual panels to bigger blocks representing a raise line.

Jan 1, 2012

Dr Hanekom I would like to thank Dr Hanekom for a very valuable -contribution; it summarizes careful statistical test work which was an omission from the original paper. Minor manipulative details, the application of a finer measuring graticule and the reproducibility of the procedure are described and the author accepts with gratitude this ready-made answer to the first and second points of Dr Finkelstein's comments. Mr Williamson The author is indebted to Mr Williamson for historical background to early experiments with captive bubbles and it is conceded that the original paper described another avenue to an old flotation goal. The field of application is restricted and we would not work with all the material illustrated by Klassen and Mokrousov.1 The particles in Figure 74(a) are far too large and irregular; material in Figures (b) through (d) could be employed for semi-quantitative work in spite of obvious disadvantages; Figure 74(f) represents ideal conditions. We have studied this mineral-collector association in the size range given and results were satisfactory. For larger pick-up values than that illustrated an induction period of more than 0.01 second was required (actually 90 seconds for a maximum bubble load at pH 7.2 with 25 g/t oleic acid!). REFERENCE 1. KLASSEN,V. I. ANDMOKROUSOV,V. A., 'An Introduction to the Theory of Flotation,' Butterworths, London, 128, Figure 74, (1963). Mr Slander and Mr Kooij Researchworkers in a practical mineral development laboratory may well ask what contribution yet another micro-technique can make to the problems of large scale ore flotation. The obvious answer is that there can be little or no direct translation of results obtained with a static system comprising air bubble and pure mineral concentrate to a dynamic multicomponent operation. However, for the rapid study of one mineral or variable some small scale apparatus must be employed. In the Anglo American Research Laboratory, the described semi-quantitative pick-up technique has filled a niche and requirement. For ourselves, the system represents a definite advance over the contact angle approach in that samples of minerals conventionally prepared in laboratory or plant may be used, which is a desired step nearer flotation. We bracket this pick-up apparatus with the Hallimond tube1,2 and evidence is now to hand that pick-up curves may often be related to flotation recoveries obtained from this tube with pure mineral samples and from the Fuerstenau glass cell3 with the total ore at low pulp densities. We would not wish to push the comparison of pick-up results past this stage for there is much published development work relating the Hallimond and Fuerstenau equipment to flotation on a larger scale. At the Anglo American Research Laboratory for example, a test in a Fuerstenau cell is often the final integrated step in laboratory investigations into the TORCO process. As these contributors rightly point out, pick-up tests can offer nothing towards the determination of optimum reagent dosage for large scale flotation. This is the function of bench-type flotation cells with up to 2 kg batches of ore. At this level, collector performance and consumption and physical properties of the froth are more comparable with large scale operation. The pick-up cell, Hallimond tube and Fuerstenau cell are essentially equipment from which the effect of control parameters can be derived. For the assessment of collector behaviour, the pick-up approach is rapid and economic and we offer here a pick-up contribution towards the flotation of Witwatersrand uraninite with anionic sulphonate collectors (Fig. 1). A large crystal of the local mineral was not available for contact angle measurements and owing to its low concentration in Witwatersrand gold-bearing reef, a small sample was laboriously obtained by tabling, superpanning and heavy medium separation. The pick-up values of a sized portion were determined by the described procedure in the presence of nine petroleum sulphonate collectors. Responses fell into two categories; "normal" curves (dotted lines) and a group of collectors which were very active at low concentration but showed depression of pick-up at the higher levels. The similarity in form of curves for collectors 1 and 3 was apparent and reagent 3 was found to be simply a diluent of 1. Otherwise, collector performance could not be related to either sulphonate content or molecular weight of the active constituent. However, reagent 2 gave the best performance in a bench flotation cell with regard to overall uranium distribution but, as predicted, reagent 1 yielded the best grades. Later pick-up tests with a similar class of collector have suggested that depression at high reagent concentrations may be due to "bubble armouring" whereby an hydrophilic air-liquid interface is produced which rejects mineral attachment. Prolonged investigations with the same mineral sample have not been required except for the study of uraninite which lasted for more than a year. Variation in pick-up response could not be detected over this period during which the mineral was stored under distilled water. The only visible change was a small efflorescence of lead sulphate, readily removed and decanted off after stirring with a glass rod in the sample tube. In its main role as a "trouble-shooter", the pick-up method is applied to fresh mineral samples taken from a flotation plant and soon discarded or from a current run in the ore-dressing laboratory. After production of a concentrate, a solvent cycle, as described in the original paper, may be required to remove heavy organics or other contaminants as when a sample has been taken from circuits containing detergents, grease or return flotation solutions. This solvent cycle will not remove chemisorbed collectors and we prefer not to work with minerals from flotation tailings or with pick-up cell discards. It has been thought preferable to answer the contributors' other apprehensions with regard to sample preparation, activators, depressants and the physical properties of reagents in another paper on offer to this Journal. It covers pick-up investigations relating to the flotation of nickeliferous pyrrhotite at two Anglo American Corporation Mines, which approach seemed the correct orientation for a reply to another contributor to this paper.

By A. Cambitsis

We show that the prioritization of business improvement and performance management decisions may be significantly improved by taking into account the systemic effects of changes made in a single process area. To do so we build a model of a mining value chain, taking into account consequential downtime that arises from downstream and upstream starvation and choking effects of each activity. Introducing the concept of internal capacity, this approach yields insight into the relative importance of key metrics such as loading and hauling rates. We suggest that a holistic view of this type should be a core component of business improvement and performance management decisions.

Jan 1, 2012

Dr T. F. Muller (Honorary President): "Mr President, gentlemen. May I congratulate the Institute on its 75th birthday, and your President on his comprehensive review of the Institute's 75 years. It is an interesting commentary on the affairs of the Institute that your President should refer to a speech made by a founder member 25 years ago on the occasion of your 50th Anniversary and then say there is no need to repeat what was given there, but that he would confine his remarks to bringing the Institute's history up to date. To me this suggests a remarkable continuity of thought and ideals-a welcome island of stability in an ever-changing world. One can somehow picture another future President, perhaps one of the younger and tougher members here today, doing the same thing in 25 years when you celebrate your centenary-and again someone doing the same in the year 2094 when your Institute is 200 years old! I hope they will recognise their debt to the early pioneers of the Institute gathered here today. In any event, this review of the fine achievements of the past 75 years is certain of an honoured place in the annals of the society. Here is a record of the onward march of technology in South Africa and a tribute to a long line of mining engineers, of chemists, metallurgists and geologists who made a greater contribution to the well-being and the prosperity of South Africans than South Africans generally are aware. Your Institute started off as a 'gold and cyanide club', peopled largely by chemists and metallurgists who made a signal contribution to the industry from the earliest times. Despite the addition to their ranks of ever-growing numbers of mining engineers, the metallurgist members have continued to make notable contributions. One recalls, for example, the manner in which they rose to the occasion to resolve the problems associated with the establishment of the uranium industry in this country. The creation of a major industry based on the existence of low grade uranium ores in the conglomerate reefs of our low grade goldfields is a classic example of the manner in which a new large industry can be rapidly created through the combined endeavours of all concerned. I noted with pleasure your remark, Mr President, that members of the Institute would like to keep up to date with recent progress in nuclear fuel matters and that members should be given the opportunity to study developments in their journal. I am sure that the National Institute of Metallurgy which conducts fuel research on behalf of the Atomic Energy Board and of the Uranium industry, and NUFCOR, which co-ordinates the uranium research programme, would be glad to co-operate if invited by the Institute to make periodical contributions to its journal. You have referred to the building up of our research organization and its dynamic approach to mining problems. I understand that the expenditure of the mineral industries on research exceeds one-third of the entire research expenditure of the private sector. South Africa is in the forefront of mining development and the focus of world attention is on the achievements of our scientists and mining engineers. We can look forward to continued advances in mining technology based on their vision and expertise. I share your disappointment, Mr President, that the Base Metals Division has ceased to exist; and that there is a resultant dearth of papers offered to the Institute on these important sections of mining and metallurgy. We are seeing some remarkable developments in the mining and beneficiation of base minerals, and it is in this area that I see the greatest potential for future expansion. If we can grasp the opportunities

At the Annual General Meeting of the Chamber of Mines of South Africa, held in Johannesburg on 29th June, 1982, the following leading members of the mining industry were elected to office for the 1982-1983 term: Mr W. W. Malan President Mr C. T. Fenton Vice-President Mr G. Y. Nisbet Vice President William Wouter Malan was born in Springs on 7th November, 1928, and was educated at the Springs High School and the University of the Witwatersrand, where he obtained a B.8c degree in mining engineering. Diamond Mines. Mr Nisbet became a consulting engineer of the Anglo American Corporation in 1972, and a deputy managing director of the Gold Division in 1974. George Young Kisbet was born in Benoni in 1923 and was educated at Pretoria Boys High and the University of the Witwatersrand. Mintek reports Report 2010D A process for the recovery of rare-earth oxides from monazite. (First published 16th March, 1979). Report 2073D A preliminary investigation of the concentration process at Ucar Minerals Corporation. (First published 19th September, 1980). Report 2092D The recovery of pyrite from gold ore by gravity separation. (First published 28th November, 1980). Report M13 Factors affecting the production of fines during the screening and handling of highcarbon ferromanganese.

Jan 1, 1982