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

Introductory remarks Dr N. G. W. Cook: This paper was published in your Journal in May of this year and you will, therefore, have had the opportunity of reading it over the past six months. I can state that experience has shown that the paper is substantially correct, but a number of questions have to be answered. The first question, Mr President, that I would be happy to answer, is how is it that one is able to cut hard, abrasive quartzite with a strength some six times greater than that of good concrete? The essence of the answer is that there is a tremendous difference between abrasion, or scratching, and cutting, or chipping. For example, it is well known that a diamond will scratch or abrade almost anything. It is also relatively easy to chip, crack or crush a diamond. As a demonstration I have here an ordinary bench grinder, and with the bench grinder I also have a piece of tool steel. The wheel on this bench grinder is a silicon carbide wheel, which is an extremely hard material, and the tool steel is much softer. In rock-cutting we use tungsten carbide for cutting the quartzite. The quartzite and the tool steel have roughly the same hardness. You can sharpen tungsten carbide with a silicon carbide wheel. In fact, this is done. It won't surprise any of you, therefore, when I show you that tool steel can be sharpened with silicon carbide. Now, what I propose to do is to change the configuration of this experiment and use the soft tool steel to cut silicon carbide, and if I can do that, I think you will agree that I have gone some way to being able to cut quartzite, which is about as hard as tool steel, with tungsten carbide, which is harder than quartzite. Let me do this. (Demonstrates.) That, I think, is a very clear demonstration of how it is possible, with a metal, to cut an extremely hard and brittle material. What, essentially, is the difference that we have here? In the first case, I held the tool with a relatively low force against the hard silicon carbide wheel. This generated a relatively low average stress, which was insufficient to fracture the carbide wheel. Nevertheless the protuberances on the silicon carbide wheel indented the tool steel and abraded it at a multiplicity of points, and quickly reduced the section of the tool steel that I held against the wheel. By changing the configuration and clamping my tool steel in a firm post, against the silicon carbide wheel, I changed these conditions very extensively. I now had a high force. I had to exert a considerable moment on that lever. The tool was anchored so that it could sustain these high forces, and they generated high stresses, which were adquate to fracture the silicon carbide. Now, what about wear? It so happens that, in these two experiments I have just done, the power I was using was about the same-a small fraction of a horse power.

May 1, 1968

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 N. C. Gay

During the past two to three years, there have been some significant Improvements to the quality of the support systems being used on South African gold mines, and the Implementation of these new developments, together with more worker awareness has been instrumental in reducing rock-related accidents, particularly in deep mines. This paper provides guidelines to mine and group personnel on how to monitor the ongoing Implementation of new technologies and so ensure the benefits that will accrue in terms of mine safety and profitability. Particular attention is given to the establishment of auditing procedures that will enable management to assess the benefits obtained from new technologies, as well as providing Improved maintenance procedures and procedures for the optimum utilization of seismic data. The areas that receive most attention include support systems for stopes and tunnels, such as hydraulic props, backfill, and rockburst-resistant tunnel support; stope and regional support layouts; mine standards; and staffing of the rock-engineering department. The paper includes a draft audit form and a hypothetical example of an audit report

Jan 1, 1997

By S. M. Spottiswoode, A. J. Jager, N. C. Gay, J. A. Ryder

The South African mining industry is at present planning to extract orebodies at depths of up to 4 km. To do this cost effectively and, at the same time, ensure safe working conditions for mining, the personnel will require both the development of new strategies and the implementation of current rock-engineering technological developments on a wide scale. This paper covers most of the technological developments likely to be required for mining at very high stresses, but it is clear that improved regional support systems will need to be developed to ensure defective stability of the rockmass during mining operations. Similarly, it is clear that improved strategies for mining in large-scale geologically disturbed areas, where slip on faults or dykes can result in wide-spread rockburst damage, will have to be addressed

Jan 1, 1995

By B. G. Fordyce, W. B. Parker

A description is given of the methods used in management planning, pit-equipment selection and maintenance operator training, and formal organization of mining personnel.

Jan 1, 1979

A South African gold mining rock-related fatal accident database has been analysed in order to determine rock-related fatality trends in the gold mining industry over the period 1990 to 1998. This analysis was extended further to include some of the individual reefs mined and focused particularly on the Carbon Leader Reef, the Ventersdorp Contact Reef, the Vaal Reef and the Basal Reef. Rock-related accident locations are also presented. A stope rock-related risk is proposed, where the fatality rate in terms of rock-related fatalities per million square metres mined for the gold mining industry as a whole is compared to individual reefs, allowing a stope rock-related risk to be attributed to the individual reef. This comparison is extended further by removing the contribution by the reef being evaluated from the industry data, thereby allowing this reef to be directly compared to the rest of the industry with respect to a stope rock-related risk.

Jan 1, 2001

By W. de Beer

We present aspects of one of several ongoing case studies used in the development of prediction techniques for major seismic instabilities. The current investigation centres on accelerated coseismic deformation described by the kinematics of failure and on softening, as well as the characterization of areas of interest by measures of the seismic response at such sites.

Jan 1, 1998

By V. Velicka, J. Ptacek, R. Snuparek, P. Konecny, G. Takla

Coal mining in Ostrava-Karvina coalfield is being accompanied by rockbursts. 82 rockbursts occurred within the period between 1990 and 2002. Natural and technological factors from these rockbursts were collected and analysed. They confirmed that rockbursts are complex geomechanical events and that the relations between co-acting technological and natural factors are very complicated. Der Abbau in dem Ostrava-Karvina Steinkohlenrevier wurde von Anfang an durch Gebirgsschläge begleitet. 82 Gebirgsschläge in dem Zeitabshnitt von 1990 bis 2002 erfolgten. Die Angaben über natürliche und technische Faktoren der Gebirgsschläge wurden gesammelt und analysiert. Es wurde bestätigt, dass die Gebirgsschläge komplexe geomechanische Phänomene sind und dass die Beziehungen zwischen den zusammenwirkenden Faktoren sehr kompliziert sind. L´abattage d´houille dans le Bassin houiller d´Ostrava-Karvina est accompagnée par les coups de terrains. 82 coups de terrains s´étaient produit dans la période entre 1990-2002. Les données sur les facteurs naturels et techniques ont été ramassées et analysées. Les résultats ont corroboré que les coups de terrains sont des phénomènes géoméchaniques complexes. Les relations entre les facteurs techniques et naturels coopérants sont très compliqués.

Jan 1, 2003

Gravity-driven rock falls account for a large proportion of all fatalities and injuries in underground mines. Potentially unstable blocks of rock are found in the hanging wall of excavations, which may be delineated by natural joints or stress fractures. These blocks, referred to as keyblocks, will fail if their weight exceeds the support capacity or if they are located between support units. This paper describes a computer program which simulates blocks in the hanging wall of an excavation based on measured properties of fractures and joints. Keyblocks are identified and placed at random locations in a predefined excavation. The keyblocks are tested against the support to determine whether they fail the support, drop out between the support or are stable. By repeating the procedure several thousand times, statistics of the probability of failure of the keyblocks are obtained. This approach allows the relative hazard associated with different types of support or excavation orientations to be obtained. It is concluded that a probabilistic approach is suitable for the evaluation of supports effectiveness in situations where large numbers of discontinuities or stress fractures are exposed in excavations.

Jan 1, 1998

Ongoing rockpass problems on mines within the South Africa region, prompted AngloGold Ashanti to embark on a risk assessment of major rockpasses. This commenced with the collection of relevant data to identify gaps in the available knowledge and identify existing problems. This was followed by an assessment of rockpass layouts to determine existing and potential interactions with other excavations. An initial risk assessment has been completed and the rockpasses have been ranked in terms of their risk profile. The lack of geological data and an easy and reliable method of surveying rockpasses have been identified as problem areas. Shortcoming is terms of rockpass management procedures have also been identified. Further work is required to quantify the risk in terms of probability of occurrence and consequences.

Jan 1, 2005

By G. B. Dukes

Scaling of rockpasses was problematic at Tau Lekoa Mine prior to production commencing in 1991. High horizontal stress levels relative to the host rock mass strength have been instrumental in causing the observed scaling. Scaling has been more pronounced in the deeper rockpasses and these are monitored regularly. Rehabilitation of one of the reef passes and one of the waste passes was required in the period 1999 to 2001. This paper describes the extent of the problems experienced to date as well as the rehabilitation completed.

Jan 1, 2006

By U. Sachse

This paper explores a systematic approach for mining decision-makers to use when faced with choosing which method to use for a specific rockpass length. The different excavation methods available in the broad South African mining industry are compared against a number of critical parameters, as applied to rockpasses of varying length. This approach is not meant as a definitive, prescriptive planning tool, but rather as a proposed approach to enable designers and planners to choose the best system to excavate their specific rockpasses

Jan 1, 2005

By Donald Leroux, Simon Gariépy, Luc Lachance

"Quantitative information about the quality of metal balance results is often overlooked when making important plant production planning decisions. Not only is this common omission made in a context where many measurements taken in and around mineral processing plants carry significant errors, but it also conflicts with the AMIRA P754 Code of Practice for Metal Accounting. The fact that metal balances are typically published without any indication of data quality may give the wrong impression that the measurements are unquestionably accurate. While it is true that statistical data reconciliation can improve the confidence intervals of redundant variables, there is no data processing technique that brings them down to zero at a finite cost. In this paper, we review the entire data flow, starting from field instruments to metal accounting-based decision-making to show how measurement errors are transmuted into business risks associated with production planning. Necessary conditions for first exposing then quantifying such business risks are stated. Pitfalls to be avoided are also discussed. Finally, a simplified risk assessment and management procedure which considers the quality of metal balance results are applied to a polymetallic mineral processing plant. INTRODUCTION Each and every mineral processing plant has production reporting obligations. In this paper, we are concerned with metal accounting reports (Morrison, 2008) where saleable metal flows and inventories are estimated and published. These metal accounting reports are delivered to a variety of stakeholders who use them for internal management purposes (day-to-day plant production planning, plant operation optimisation, capital spending, etc.) as well as for external management (royalty settlements, tolling agreements, etc.). Hence, there should be no doubt that spotless metal accounting is instrumental to high-quality corporate governance (Gaylard et al., 2014) of mining and metallurgical companies. To this extent, one would have expected industry-endorsed standards to have emerged a long time ago. However, the lack of an accepted set of standard procedures for metallurgical accounting was explicitly recognized as an industry-wide problem only in August 2001 during an SAIMM workshop held in Cape Town, South Africa. Discussions that followed this workshop led to the initiation of the AMIRA Project P754, “Metal Accounting and Reconciliation”, in 2003."

Jan 1, 2015

By E. J. M. Jahnsen, I. Jauhari, T. Badrujaman, F. A. Stober, B. O. Wasmund, L. R. Nelson, T. Miraza, J. M. A. Geldenhuis, A. Taofik Hidyat

The role of dedicated operational support in the ramp-up and stabilisation of the FeNi-II furnace for ferro-nickel production at PT Antam?s smelter located in Pomalaa, Indonesia is described. The furnace was uprated to 32MW capability in a rebuild performed in 2005. This primarily involved installing a larger transformer, coupled with adoption of HATCH water-cooled copper plate, waffle and flanker coolers with integrated metal and slag tapblocks, HATCH air-cooled copper fin lower sidewall cooling and HATCH vertical sidewall binding system ? ?holddowns?. Following a smooth commissioning period, the progress in attaining the preliminary ramp-up target load of 24MW is described. This initial target was set by Antam, subject to some prevailing smelter equipment constraints, particularly kiln capacity. Stabilisation of the furnace operation is discussed, together with some of the specific commissioning and operational challenges surmounted by the joint Antam-HATCH team. These included: ?Mastering furnace integrity monitoring and operation with copper coolers, especially metal tapblock planned maintenance and repair strategies; ?Transition from traditional ?immersed electrode? to ?brush-arc? mode of operation approaching as closely as possible to the productive ?shielded-arc? mode of operation within existing equipment constraints; ?Reductant selection and control issues; ?Utilising the sophisticated furnace monitoring to provide detailed indication and warning of potentially destructive furnace upset conditions such as Si reversion and CO boils.

Jan 1, 2007

By O. Barron, C. Felix

In 2023, polymer electrolyte membrane fuel cell membrane electrode assemblies accounted for about 62% of the global fuel cell market share and this demand is expected to grow. Commercialisation requires technologies capable of cost-effective, high-volume manufacturing. The membrane electrode assembly is crucial and represents a significant cost to polymer electrolyte membrane fuel cell manufacturing. Manufacturing the electrode components for membrane electrode assemblies at high volumes can reduce production costs while delivering on the forecasted industry demands. Roll-to-roll is a mature coating technology applied in various manufacturing industries such as batteries, printed electronics, microelectronics, photovoltaics, printing, paper consumables, etc., with significant potential for polymer electrolyte membrane fuel cell manufacturing. While the high-volume production process for membrane electrode assembly manufacturing differs from laboratory-scale, the membrane electrode assembly structure remains unchanged. Roll-to-roll is a continuous coating process with speeds of 10 m/min being achieved. In this work, MicrogravureTM and slot-die coating methods have been adopted and have shown promising outcomes for producing gas diffusion electrodes for membrane electrode assemblies. An overview of the MicrogravureTM and slotdie coating methodologies is provided, and a discussion on preliminary results and challenges are presented. Work on MicrogravureTM gas diffusion electrode manufacturing has already achieved comparable performance with spray-coated gas diffusion electrodes. The influence of coating parameters and drying on the coated catalyst layer quality is discussed.

May 27, 2025

By J. Wills

The use of drilling rigs to increasingly mechanize stope drilling has been acknowledged as important for the S.A. mining industry in it ís efforts to tackle the challenges of low productivity, AIDS and an ageing driller workforce. The spin-offs of increased safety, cost-effectiveness and better mining performance provide advantages to all?from the driller to the shareholder. However, implementation or product rollout has varied from outright success to dismal failure. A study of various cases by Novatek and Anglogold TDS showed clear reasons for these differences. Whereas the successes were characterized by clear objectives, accountability, user buy-in, a commitment to make the technology work and no-nonsense reporting, these were typically absent in failed implementations. The attitude at unsuccessful mines was to ?trial? the equipment?even subconsciously, a ?trial? is a test where failure becomes an acceptable outcome. During the study it became clear that mining management are not adequately trained to manage the often-tricky rollout process. They are often also not empowered or clearly mandated to deal with the organizational, human and technical issues that must dovetail to create a success. The output of the study was to develop a basic rollout process that could be used to formally manage the implementation of new drilling technology. Creating an alignment between the mine, workforce and supplier promotes a win-win situation that will not otherwise spontaneously arise.

Jan 1, 2002

By O. S. Lubbe, G. Annandale, J. W. van Wyk

This paper deals with the development and evolution of room and pillar mining in the South African chromitite and platinum mining industry over the past sixteen years. The paper describes the need for cheaper, more effective and safer mining methods in hard rock mining. It also describes how a mining method traditionally only applied in coal mining in South Africa evolved into a method ideally suited to conditions in chromitite and platinum mines. The paper also touches on joint efforts from mining houses, mine management and equipment manufacturers to design and build mechanized equipment custom designed and unique to South Africa in order to overcome challenges presented by the harsh operating conditions encountered in the mines in the Bushveld Complex.

Sep 1, 2001

By A. Peake

Background The CSIR Division of Mining Technology assumed responsibility for the operations of the Hoist Rope and Mechanical Test Laboratories at Cottesloe in April 1999. The laboratories were previously the responsibility of the CSIR’s Division of Manufacturing and Materials Technology, before which they fell under the National Mechanical Engineering Research Institute (also of CSIR). As the focus of this conference is on safety in mines research institutes, it was thought appropriate that this paper should review some of the activities at Cottesloe and its role in supporting mine safety strategies.

Jan 1, 2003

By J. H. French, O. E. Lissner

S. J. Venning (Member): The authors should be congratulated on producing such concise data from the plethora of experimental report results. Their observations on the cost of liners calls for some comment however, as the really unique feature about liners in South Africa is that they can be obtained so cheaply. Attention has been focussed on the 1961 cost of white iron at R50 per ton for chill cast block liners while manganese steel liners are reported as costing as much as R250 per ton. The former are however, a relatively heavy, simple casting with a low labour content and reasonably high percentage productivity, made from metal melted in a cupola. The capital investment to produce this type of casting is low compared with that required to produce manganese or other alloy steels. The chill cast liner block is always a production item and is cast in a permanent mould. Almost all manganese mill liners, except perhaps small aperture screens, are sold for considerably less than the R250 per ton quoted by the authors. Where a price of this nature is asked it would be because the design of the casting demanded is complicated or leaves little metal to carry the labour and other costs of production. As reference has also been made in the paper to liner costs in America, prices for similar types of liners obtained during a visit to Canada and the U.S.A. in 1961, could be of interest: Material Price per Location short ton Ni-hard R250 Elliot Lake Body liners block type Ni-Hard R300-310 FAS New York Mn Steel R280-290 FAS New York Screens (grids) slotted Cr.Mo. Steel R600 FAS New York hole Ni-Hard R320 Elliot Lake At this time the price of comparable manganese steel block type liners on the Witwatersrand was between R145/R155 per short ton. White iron in Canada was then quoted at about R150 per ton, but as Ni-Hard gave a life of at least two to twoand-a-half times that of white iron, it was a much more attractive proposition particularly when relining and down time costs were taken into consideration. There is little doubt that most foundries would welcome clear and complete specifications of the customers requirements and systematic checks to ensure that these specifications are being met. B.S.S. or other accepted standards should form the basis of these, and periodic inspections should be undertaken to ensure that only those foundries capable of complying should be included as suppliers. The authors have referred to new designs, but can the industry really call the grid and plate new when the patents were taken out during the second world war and the sawtooth block has been used for at least 35 years. Unfortunately, far too little thought and consideration are normally given to the ultimate mill liner design while the mills themselves are on the drawing boards. The position and size of the door opening, which is the key to the ultimate shell liner configuration, the drilling of the

Jan 9, 1968

By A. D. Thomas, K. C. Wilson

Some years ago, the authors developed an analysis of non-Newtonian pipe flow based on enhanced turbulent microscale and associated sub-layer thickening. This analysis, which can be used for various rheologic modelling equations, has in the past been applied to smooth-walled pipes. The present paper extends the analysis to rough walls, using the popular Bingham plastic equation as a representative rheological behaviour in order to prepare friction-factor plots for comparison with measured results. The conditions for laminar-turbulent transition for both smooth and rough walls are also considered, and comparisons are made with earlier correlations and with experimental data.

Jan 1, 2007