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By S. R. Stadler

Koffiefontein Mine commissioned a distributed antenna system as an underground communication backbone for the DISPATCH® production management system during September1999. STAS Ltd, the supplier of the Distributed Antenna System developed the System for an Integrated and Automated Mine (SIAM). This communication system, in conjunction with DISPATCH®, fulfils Koffiefontein Mine’s present and future requirements for accurate draw control, increasing productivity and improving working conditions. The DAS as SIAMnet communication network was selected by the mine, because of its superior data transmission rate of up to 1.5Mbps at 860MHz, video and Ethernet transmission facilities, and future enhancement abilities. The results of the commissioning tests confirmed the quality and integrity of the data and voice communication. The initial installation enabled 9000 metres of underground production tunnels with voice communication inclusive of 3700 metres having data communication. This article discusses the requirements and selection of the telecommunication system for an underground mine. A description of the installed distributed antenna system follows with a summary of the commissioning tests. A discussion of the reliability of the components is followed by conclusions with suitable recommendations. Keywords: distributed antenna system, underground mining, telecommunication system.

Sep 1, 2001

By G. E. Blight

The mining industry is making increasing use of pumped tailings fills. The properties that affect the performance of tailings fills are described by means of typical examples. They are the particle-size grading for maximum density, the water content for pumpability, settlement after placing, compression and drainage under stress, shear strength, and resistance to shock loading.

Jan 1, 1979

By T. O. Hagan

A system for the monitoring of micrcoseismic events. which is designed for use in feasibility studies of rock-burst prediction, has been operating at Western Deep levels Limited since 1977. Analyses have revealed that the presence and Orientation of geological discontinuities ahead of the mine face can be predicted from the data produced by this system.

Jan 1, 1981

By D. Menne

An empirical dimensionless correlation is presented that relates system variables to the superficial slip velocity between solid mineral products and an interstitial fluid. The correlation is valid within engineering accuracy for all solids and fluids at all concentrations. The particular usefulness of the correlation is that it provides explicit equations for both slip velocity and voidage.

Jan 1, 1983

By Steven L. Crouch

The 'doorstopper' technique for determining the state of stress in rock requires that the stress concentration factors at the flat end of a borehole be known. Published values of these factors are widely variant. An axisymmetric finite element analysis of this problem has been made, yielding elastic stress concentration factors for different values of Poisson's ratio.

By K. R. Noble

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

Jan 1, 1987

"This study examines the problems faced by open pit mine superintendents who make choices about how to direct their materials, either to the waste dump or to the mill. The paper explores the effects of introducing a 10% sampling error and a 0.9-times to 1.1-times sampling bias on positively skewed distributions for precious and base metals, negatively skewed distributions in the case of bulk commodities, and normal distributions as is the case for coal deposits. Parent distributions for each commodity were created on a 25 x 25 m grid using transformations of gold, iron ore, and coal data-sets, spatially based on a nonconditional Gaussian simulation. Ordinary kriging of grades for the three commodities into a 10 x 10 m grid provided the reference case against which the distributions with the sampling error and sampling bias for the commodities were compared. Imposing cut-off grades on the actual-versus-estimated scatterplots of the three commodities allowed the distributions to be classified into components of waste, dilution, ore, and lost ore. Ordinary kriging of values for each deposit type acted as the reference data-set against which the effects and influence of 10% sampling error and 0.9-times to 1.1-times sampling bias are measured in each deposit type. Indications are that the influence of error and bias is not as significant in gold deposits as it is in iron ore and coal deposits, where the introduction of small amounts of error and bias can severely affect the deposit value.IntroductionThe effects of poor sampling and the financial implications for mining companies, traders in mineral assets, and sellers of metal as dore or commodities is documented in a number of studies, the most notable of which is that by Carasco (2004). He examined the financial impact of poor sampling practices in the Chilean copper industry and found that finacial losses due to poor sampling amounted to hundreds of millions of dollars over the life of a mining operation. Holmes (2004) examined the effects of correct sampling and measurement as the foundations of metallurgical balances, and found that revenues from the sales of large iron ore shipments may be profoundly affected by poor sampling practices. In South Africa the way in which sampling of in situ gold-bearing reefs affects the mine call factor has been an ongoing study since the disparity between the estimation of gold in the reef and the actual gold bullion produced was noted by early investigators such as Beringer (1938), Jackson (1946), Sichel (1947), Harrison (1952), and a number of others."

Jan 1, 2017

By Dick Stacey

Many open pit mines are now being mined at very significant depths, often at depths far greater than was originally planned. Even deeper open pits are also being planned, to depths that would be considered deep by underground standards. The heights of the resulting rock slopes are usually beyond the current experience and knowledge base. The exceptions are, perhaps, some very high and steep natural rock slopes. These natural rock slopes are also assuming greater significance owing to pressures of infrastructure development and consequent exposure of such infrastructure to the hazards of slope failure and landslides. Developments in road and rail infrastructure are also resulting in higher rock cuttings. Present understanding of the mechanisms of slope behaviour and failure for high slopes, and for slopes subjected to high in situ stress conditions, appears to be lacking. If the mechanisms of slope behaviour are not well understood, the validity of commonly applied methods of analysis of the stability of such slopes may be questionable. The papers in this specialist International Symposium, including papers on mechanisms and monitoring techniques, and case studies will contribute to the understanding of these issues. The Symposium has attracted good international participation, from both the attendance and authorship points of view. We are very grateful to all presenters and delegates for taking timeout of their very busy schedules to come and share their knowledge and we hope that all will benefit from this event. Thanks are due to the Organising Committee and to the members of our International Advisory Panel for the ideas, the contacts and the badgering, and to the Secretariat of the South African Institute of Mining and Metallurgy for the organisation.

Jan 1, 2006

By J. E. Friant, R. P. H. Willis, J. Maaren

Considerable effort is currently directed towards the development of non-explosive mining methods with the potential to allow continuous mining in narrow reef conditions. Besides improving productivity, continuous mining results in concentrated mining which has a significant impact on reducing infrastructure costs. CSIR: Miningtek recognized the potential of mini-disc cutters in a long or short wall application for selective hard rock mining in 1999. EEA was chartered to build a 780 mm diameter by 800 mm deep drum cutter head. While EEA designed and built the head, CSIR designed and built the drive mechanism and chassis for the trial machine. After assembly and shop testing at CSIR’s facility, the machine was shipped to a platinum mine for trials. This paper traces the development of mini-disc cutters and their application in South Africa.

Sep 1, 2001

By B. K. Loveday

There are certain ores that can be treated without upgrading (e.g., gold and uranium ores), and upgrading needs to be considered only for fairly low-grade ores of this type. If the grade is very low, treatment will not be economic even with upgrading, and there is therefore a limited range of ore grades for which upgrading is suitable.

Jan 1, 1980

By D. I. Nicol

An assessment is made of the possible scope for the use of activated charcoal as the solid adsorbent in an upflow fluidized-bed contactor, and a pilot-plant programme for the recovery of low concentrations of dissolved gold in this contactor is described. It was found possible to produce an effluent that contains less than 0,01 p.p.m. of dissolved gold.

Jan 1, 1997

By A. Whillier

Recovery of energy from the water going down mine shafts by A. WHILLIER, Pr. Eng., Se. D. (M.I.T.) (Fellow) The influence of energy-recovery systems on the rise in temperature of water going down mines is examined. It is concluded that the, cost benefit of such systems, deriving partially from the reduced temperature rise in situations where cold water IS sent underground from surface, would more than justify the installation cost.

Jan 4, 1977

By M. H. Moys

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

Jan 1, 1987

By Peter Stacey

This presentation provides comments on the increasing challenges associated with pit slope designs from the perspective of a design reviewer. Besides the technical issues related to the significant increase in current and proposed slope heights since the primary methodology in current use for pit slope designs was developed, other factors are coming into play. These include changes in mining equipment and associated operating practices, as well as a growing awareness on the part of mining executives and other stakeholders of the significance of stable, or at least well-managed, slopes. In the latter area, the associated clarification of responsibility has led to the increased use of either in-house or independent review consultants working on the behalf of management. From a technical perspective, since the mid-1970?s there have been significant improvements in the tools, particularly analytical methods, that are available to slope designers. There is also an increased understanding of the importance of a detailed geological model, with strong emphasis on alteration and/or structure to form the platform for the slope designs. However, the basic technology for determining the rock strength aspects has changed little, although an expanding body of experience is being accumulated in its use and there is a reasonable degree of comfort in its application for slope heights of up to at least 500 m. In addition, slope management is now viewed as a critical part of the implementation of slope designs and this has been supported by continuing improvements in slope monitoring systems. In recent years safety has become a primary concern, in part as a result of some major slope failures that have attracted the attention of regulators and the public, as well as mining executives, who are being held more responsible for unsafe conditions and associated events. There is therefore a growing demand for risk assessments to replace the deterministic design approaches upon which the current design technology is largely based. The focus of mine executives on safety has undoubtedly in part facilitated the recent long overdue revitalization of research into the design and stability of large pit slopes, the requirement for which has been recognized for many years by practitioners. This research, as well as the CSIRO Large Open Pit Study, will almost certainly provide advances beyond the empirical strength determination methods such as the Hoek-Brown failure criterion, which form the basis for current rockmass strength determination. At the same time, as mentioned above, there is a growing awareness of the requirement for a detailed structural model as a major component of every large slope design. In addition, other areas requiring further research include the impact of groundwater pressures on rock mass strength, particularly in rocks with low permeabilities, and the role of stress in high open pit slopes. From the perspective of design implementation, even with the recent significant advances in metal prices, mine operators remain under pressure to minimize mining costs. To address these constraints, mining equipment of ever increasing size is being introduced. There are, however, some disadvantages to this trend in the area of slope design. For example, the large electric shovels are not well designed for scaling bench faces, nor are they cost effective in this mode. As a result, specialized equipment may be needed in the mining cycle to perform the clean-up duties, which in turn increases operating costs. Further, where the large equipment is used in minimum width pushbacks to reduce the instantaneous stripping ratio, the advance rates can be high, but at the same time the associated changes in operating procedures are often not conducive to the concurrent use of such measures as controlled blasting, careful scaling and drain hole installation that generally improve stability. The resulting conflicts which may arise between the interests of production and those of slope stability are often exacerbated by the fact that these stabilization techniques actually increase the operating costs on which the operations manager is frequently judged, even though there is an overall increase in profit. Meeting the objective of developing slope designs which are practicable , i.e., achievable in terms of every aspect of the operating constraints in the specific pit, requires interaction and compromise between the geotechnical engineer, mine planners and operating staff during the formulation of the design criteria. In the current environment, it is often no longer sufficient to present slope designs in deterministic terms to a mine planner who accepts them almost without question. Increasingly, the requirement is that they be proposed within the framework of risk levels, related both to safety and to economic outcomes, to a decision maker who may not be a technical expert in the mining field. In this context, the mine executives must have sufficient information and understanding to be able to establish acceptable levels of risk for the company and other stakeholders; in this process the slope designers must play a major role. These changing requirements for presentation of slope designs necessitate clear communication of the basis for the design, which may be very complex, so that the implications of the designs may be thoroughly understood by all concerned. To ensure clarity at this stage, the slope designer must not only quantify the uncertainty in the input parameters, including the geological model, but must also be able to communicate and defend the resulting design recommendations. Where particular designs may have high associated risks, simply because of the degree of uncertainty in the data, this must also be recognized and proposed methods of reducing the uncertainty included in the presentation. In summary, from a reviewer?s perspective slope designs must not only be technically sound, but must also address the broader context of the mining operation as a whole, taking into account such factors as safety aspects, the available equipment to implement the designs, and the acceptable risk levels for the company. In addition, the designs must be presented in a way that will allow the mine executives, who are ultimately responsible, and the operators, who implement the designs, to fully understand the basis and short-comings of the designs and the risks associated with deviation from any constraints defined by the designer. It goes without saying that there must also be a well-defined monitoring system to confirm stability and detect and manage any variations in the design model or unexpected instability.

Jan 1, 2006

By C. G. Schmidt, N. W. Hanf

Many of the pyrite concentrates produced at South African gold and uranium mines contain economically significant amounts of nickel, copper, and cobalt, apart from gold and uranium. In some cases these concentrates are leached for uranium, followed by roasting and cyanidation of the calcine for the extraction of the gold. Even if their intrinsic value is excluded, the presence of appreciable amounts of base metals can lead to excessive consumption of cyanide and zinc in the conventional process for the recovery of gold from calcines. The extent to which base metals, particularly cyanocides in the calcine, can be made soluble in water or in dilute acid by variation of the pyrite roasting conditions was investigated. An important finding of the investigation was that the conditions producing favourable base-metal sulphation (and hence solubility in water) also produced good sulphation of the uranium values that had not been extracted in a conventional leach of the original pyrite. Thus, if the pyrite is subjected to a sulphating roast followed by quenching in water (or dilute acid), it should be possible for the uranium to be extracted in improved yield. The need for leaching of the pyrite would therefore fall away. It was noted that sulphation roasting also resulted in improved gold extractions when the calcine was subsequently subjected to conventional cyanide-extraction procedures. From well-sulphated calcine, the dissolution of base metals and uranium appeared to be fairly independent of leaching pH, time, and temperature. On an inadequately sulphated calcine, Iow pH values during leaching gave increased extraction of copper and uranium but did not have a significant effect on the dissolution of nickel and cobalt. The extraction of uranium increased with increasing leaching time and temperature, while only longer times at a Iow pH value markedly improved the extraction of copper. The extraction of cobalt was fairly independent of leaching time and temperature, but the results were insufficient for a conclusive evaluation to be made of their effects on the dissolution of nickel. A cursory economic assessment 'indicated that sulphation roasting applied to the pyrites investigated is likely to be very profitable.

Jan 1, 1979

By A. L. Hinde, A. A. Bradley, P. J. Lloyd

The results of slow crushing tests in a stiff testing machine for both small and large step reductions of particle size are given. The energy consumption required to produce a given weight of minus 74 um material was determined when both single-crystal quartz and Witwatersrand reef were crushed. For comparison the two materials tested were also comminuted in a ball mill under optimum conditions. There are indications that slow crushing under stiff conditions is the most efficient method of breakage that can be devised. The comparison with ball milling results thus yields a value for the efficiency of ball milling of approximately 80 per cent. These results confirm that the best current estimates of milling efficiency, which are based on the free boundary surface energy of the material being milled, are probably too low by at least one order of magnitude.

By K. O. R. Gebhard

Direct reduction-are we moving in the right direction? by K. o. R. GEBHARD INTRODUCTION Numerous forecasts predict a rapid growth rate for direct-reduction processes. The figures quoted are so impressive that many a top manager must fear that he will fall behind in technical development if he does not base a substantial part of his future steelmaking for mass production on direct reduction.

Jan 2, 1974

By G. Y. Nisbet

The contribution made to the economy of South Africa by the-minerals industry is discussed according to four of its aspects. Firstly, the industry supports both students and lecturers in technical and academic institutions. This support covers virtually the whole range of courses available at the universities and technikons, although most is obviously devoted to the engineering and science faculties. Secondly, the industry makes a direct financial contribution to the State in that it contributes about40 per cent of the State's receipts from direct tax paid on incomes and 30 per cent of the contributions to the total State revenue. It provides employment for 28 per cent of the total active labour force, and contributes 24 per cent directly to the gross domestic product. Thirdly, the industry is responsible for over 65 per cent of the country's foreign earnings in spite of the significant rise in exports from the manufacturing sector. South African minerals are of crucial importance to the word, since the country has the world's largest reserves of seven minerals and features very prominently in many others. Finally, the industry makes an indirect contribution, referred to as the multiplier effect. This is the ripple effect on the economy made by a large injection of momey by which that money acquires an added effective value. A study made of the total production of the mining industry in 1978, for instance, showed this multiplier to havea value of 1,5. Thus, if this effect is included, the industry's contribution to the gross domestic product is 44,S per cent. Similarly, the industry is responsible for the creation of jobs both within itself and in other industries, which could amount to 100000 for the period 1981 to 1935.

Jan 1, 1981

By T. K. Roy

INFACON XI has no doubt earned the distinction as the first such Congress in India. This prestigious occasion could become a reality of a long cherished dream of the Indian Ferroalloy Producers, consumers and ex-porters. The International Committee of Ferro Alloys (ICFA), South Africa, the august body for organising INFACON, every three years, could be convinced by the Indian Ferro Alloy Producers? Association (IFAPA) to award INFACON (XI) to India. This Congresss, organized by IFAPA, has opened a window for the Ferroalloy Community of India, the up-coming Asian Tiger, to register their strength and weakness to the world forum with the principal objectives of evolving long and short-term optimum road-maps for development. It is to be reckoned that India is poised to be a steel giant by 2020 when it is envisaged that the steel production may reach a level of 120 million tons of which significant proportion has to be in the categories of alloy and special steels, requiring standard and high grade ferroalloys. Keeping the above objective in view, the theme of this Congress has been rightfully designed as ?Innovations in Ferro Alloy Industry.? This Congress has also earned a distinction of more than eighty papers, finally selected for inclusion in the Proceedings. More than 100 internationally and nationally reputed experts in the field of ferroalloys (technology and manufacturing practices as well as world scenario) have been approached for critical review of abstracts and selection for the proceedings. It needs to be mentioned without the cooperation received from ICFA the high standard of INFACON could not have been assured. The papers are suitably grouped under seventeen heads, starting from world situation to production and operation followed by present and future technologies and finally to modelling and simulation. It is a Herculean task to the Technical Committee to fit these papers in proper sequence. The Commit-tee members kept no stone unturned to ensure the cogency with the subject matters and at the same timekeeping the flexibility of interests of the participant, especially in the context of three parallel sessions. The Proceedings containing only refereed papers of high quality, will serve the entire gamut of ferroalloy industry and will also highlight the present status of concerned countries. The areas of attention to make the industries globally competitive and at the same time laying emphasis on the prevailing practices, will help the industry leaders to formulate an appropriate global approach. Following the break-through step, instilled by INFACON XI, the Proceedings will be available both in bound and in searchable electronic CD-ROM format. I, as the Chairman of the Technical Committee would like to express thanks and high appreciation to all the Committee members for their whole hearted efforts in all respects without which it would not have been possible to complete these proceedings in the scheduled time. Technical Committee desires to place on record their gratitude to Organising Committee for their synergic cooperation all through in successfully executing multifarious tasks, associated with such a grand international technical Congress.

Jan 1, 2007

By E. J. Magri

This paper describes a geostatistical study of the relative merits of diamond-saw sampling and conventional chip sampling, using results from experimental work carried out on Randfontein Estates Gold Mine and Western Areas Gold Mine. The diamond-saw sampling procedure is described, and it is concluded that this is a very efficient operation and leads to good-quality sampling that is clearly an improvement over conventional chip sampling. The study principally involved the computation of the errors of estimation of the mea gold value of mining panels for the two sampling methods, revealing that, in the normal production environment, the diamond-saw sampling method is a significant improvement over conventional chip sampling, as evidenced by the reduced estimation errors achieved. The question of optimum sample spacing is discussed, and it is concluded that the required spacing for chip sampling needs to be smaller than for the diamond-saw method.

Jan 1, 1986