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COUNCIL The following served on Council during the year under review: Office bearers: Prof D. D. Howat (President), Dr J. P. Hugo and P. W. J. van Rensburg (Vice-Presidents), V. C. Robinson (Immediate Past President) and D. G. Maxwell (Honorary Treasurer). Ordinary Members of Council: H. P. Carlisle, R. C. Espley-Jones, G. H. Grange, Dr D. I. Legge, W. W. Malan, Prof R. P. Plewman, Dr R. E. Robinson, Dr M. D. G. Salamon, L. W. P. van den Bosch and P. A. von Wielligh. Branch Chairmen: A. Bain (Witbank-Middelburg Branch), J. M. Meyer (O.F.S. Branch). Past Presidents serving on Council: R. J. Adamson, M. Barcza, H. Britten, H. E. Cross, J. K. E. Douglas, R. C. J. Goode, P. Lambooy, Prof J. de V. Lambrechts, Dr J. T. McIntyre, J. F. Reid and H. Simon (until March 1972). Ten Council meetings were held during the year with an average attendance of nineteen, and the standing committees held 27 meetings. FINANCE The annual accounts which are attached to this report show an excess of income over expenditure of R21 519. It is very gratifying to be able to report that Council's efforts to stop the depletion of our accumulated funds are meeting with success. The most important contributors to our surplus this year are symposia and colloquia, sales of publications, Company Affiliate subscriptions and the profit on the journal. While we do not expect continued profits from all these sources in the future we do feel that we are now in the process of accumulating a substantial financial foundation. This will give the Council the necessary confidence to initiate the new developments in the activities of the Institute which are now under consideration. The decision to create a new grade of membership, Company Affiliate, is dealt with elsewhere in this report. There has been a generous initial response from companies and this is the cornerstone of our improved financial expectations. The MacArthur Forrest Memorial Fund shows an excess of income over expenditure of R91 and the total fund was, therefore, increased by this amount to R4 502. The balance sheet shows that the market value of quoted shares and debentures increased during the year from R9 160 to RH 331, which is R2 134 in excess of the book value. Accumulated funds now amount to RH 529 compared with R23 010 a year ago. MEMBERSHIP Sixteen Fellows, twenty Members, six Graduates, nine Associates, twelve Students and twenty-four Company Affiliates were elected during the year. One Member and two Associates were reinstated. Twelve members were admitted to retired membership. Transfers: Member to Fellow, three. Graduate to Member, seven Associate to Fellow, one. Student to Member, one. Student to Graduate, four. Student to Fellow, one. Your Council records with deep regret the death during the year of the following: Dr A. J. Orenstein (Honorary Life Fellow), R. A. Cooper, R. J. Spargo, H. Simon and F. Meyer (Life Fellows), S. D. Loxton, W. P. Arnold, G. C. Needham, W. G. Pyne-Mercier, J. Innes and O. T. Wright (Fellows), E. P. Mennell and O. B. Prentis (Members), J. Brits (Associate). After careful consideration of all the implications it was decided during the year to create a new grade of membership to be known as Company Affiliate, in order that there might be a formal and permanent channel for companies to contribute to the important work of the Institute. As recorded above, 24 companies had joined by the end of the year and many further applications have been received since. We extend a hearty welcome to all our new members. A comparative statement of membership as at 30th June, 1972, and the end of the previous year is shown in the following tabulation:-

By P. Amponsah-Mensah

Dilution of ore has a major impact on economics of a mine. The magnitude of dilution depends on mining method, stope dimensions, reef and host rock quality, wall support and drilling accuracy. The main contributing factor is the presence of very weak graphitic shear band of varying thickness in and around the reef. The reef, at Obuasi, is generally steeply dipping and open stoping is the predominant mining method. The stability of the stope walls limits the stope dimensions. Various options for allowing larger stopes for higher productivity and limiting dilution are analysed. The most economic way is to reinforce the walls with systematic cablebolt supports. This option does not only add the support cost but also requires additional cost of access development. These conflicting requirements are continually being optimised at the mine for the economics of dilution control. La dilution du minerai à un impact majeure sur l’économie d’une mine. La quantité de matériel diluant le minerai dépend de la méthode d’extraction, de la dimension des chantiers d’abattage, de la qualité du filon et de la roche mère, du support des épontes et de la précision du forage de production. Le facteur principal qui contribue à la dilution est la présence d’étroites zones cisaillées qui contiennent du graphite ayant différentes épaisseurs à l’intérieur et autour du filon. Le filon, à Obuasi, est généralement à fort pendage et la méthode d’abattage principale est par chantier long-trous. La stabilité des épontes est le facteur qui détermine la dimension des chantiers d’abattage. Differentes options ont été analysées de façon à permettre de plus larges chantiers de manière à augmenter la productivité tout en limitant la dilution. Le moyen le plus économique est de renforcer les épontes avec des cables d’acier cimentés forés de façon systématiques. Cette option n’augmente pas seulement les coûts de support mais aussi les coûts de développement. Ces besoins contradictoires sont continuellement revisés à l’opération afin d’optimiser l’économique par le contrôle de la dilution. Verdünnung des Erzes hat eine spürbare Auswirkung auf die Ekonomie einer Grube. Die Größe der Verdünnung hängt von gewinnenmethode, von den Stopemaßen, von der Reef- und Wirtsfelsenqualität, von der Wandunterstützung und von der bohrengenauigkeit ab. Der beitragende Hauptfaktor ist das Vorhandensein einer sehr schwachen graphitic Scherbandes unterschiedlichen Stärke in und um der Reef. Der Reef, bei Obuasi, taucht im allgemeinen steil ab und geöffnete Aufstemmung ist die überwiegende gewinnenmethode. Die Stabilität der Wand begrenz die Stope grösse. Verschiedene Wahlen für das Erlauben der größeren Stopes für höhere Produktivität und das Begrenzen von Erzesverdünnung werden analysiert. Die ökonomischste Weise soll die Wände mit systematischen Kableankerbolzenunterstützungen verstärken. Diese Wahl addiert nicht nur die Kosten der Unterstützung aber erfordert auch zusätzliche Kosten fuer Zugangsentwicklung. Diese kontroversen Anforderungen werden fortwährend an der Grube analysiert um die Verdünnungkontrolle zu optimieren.

Jan 1, 2003

By M. Arnesen

Mining professionals recognize the need to continuously evaluate and refine mine planning standards and scheduling. We must examine our current reality, and evaluate the following: •How well do our planning standards represent the actual mining process? •To what extent do they support the requirements of the downstream mining activities? •How we apply them to operational management and control? In most operations, mine-planning standards are global averages. Little differentiation is madein quantifying key planning variables. Often standards used in the long-term, are applied to the short-term, and the standards and scheduling precedents are only reviewed occasionally. Mine-planning standards applied to production schedules are often only focused on the management of functional mining performance, and play no role in managing the requirements of down stream processing. Many mining operations are characterized by high levels of fluctuation, and typically incorporate a wide range of factors and adjustments to compensate for deviations from performance targets, in mining operations as well as for the other business areas. The reason for using global averages is because of a lack of understanding of the causes of deviations that occur through the process, and the impact that they may have on the performance of the business as a whole. Average standards and factors are often used to quantify the variability in a system. From these average values, measurement standards and performance targets are derived for the planning and execution environments. During the execution of a plan/schedule there will be deviation in actual performance and the planned ‘average’ standards. In reality the ‘average’ conditions seldom occur and the impact of variability and interdependency are seldom constant or predictable. The predictability of variability and interdependency is further complicated by the fact that mining conditions have a role to play in the actual production performance, and they too are variable. By developing the throughput knowledge of our production systems, we can better understand the nature of variability and the interdependency within the systems as well as the impact of interdependency between the links in our production chains. With this knowledge, planning standards and scheduling precedents can be better defined and sensibly differentiated. This will improve planning and management of ore utilization, mining production and the effectiveness of processing. As a result the business will be more stable and predictable and business performance will be improved. The purpose of this paper is to describe: •At a high level, the scope for refining and differentiation in mine planning standards, and incorporating geological and plant parameters into mine scheduling. This will improve planning and scheduling and the overall performance of the mine. Given our current level of scientific knowledge and the technological tools at our disposal we should be able to plan and schedule production so that we can manage pro-actively and improve business performance. In doing so we can also improve reconciliation and value tracking through mining and processing •The flexibility and functionality of the XPAC planning and scheduling tool that will enable a throughput management approach.

Jan 1, 2003

By Z-P. Song, Z-B. Jiang, A-N. Jiang

"In deep excavations under conditions of high ground stress, even hard rock undergoes creep and other time-dependent effects that may result in instability. This study involves an analysis of the typical damage to the surrounding rock in the deep tunnels of the Jinchuan nickel mine in China. In order to understand the creep mechanism, triaxial creep laboratory tests were conducted under high stress. The creep characteristic curves and the Nishihara model parameters of typical rock were obtained from these tests. The numerical simulations, with which the creep model is developed, were performed using Flac3D. The creep model parameters were back-analysed on the basis of field monitoring data. Finally, appropriate support schemes for deep tunnels are suggested. The creep deformation of rock increases with time and axial load. At the same load level, the creep deformation of unloading is greater than that of loading. The simulated deformations of the surrounding rock are coincident with those from in situ monitoring, indicating the applicability of the presented rock creep model in situations of high ground stress. The results constitute a reference for support design in deep mining tunnels.IntroductionThe excavation of underground caverns can alter the natural stress field of the surrounding rock. In deep engineering projects under conditions of high ground stress, even hard rock shows obvious creep properties and time effects (Yao, 2005; Liu, 1994). The time effect of excavation not only causes decompression of the floor and increases sidewall stress, but also leads to stress concentration at the corners of the excavation, which influences the stability of the surrounding rock in a very complex manner.Many researchers have studied the creep properties of rock. ‘Griggs (1939) showed that creep occurs in sandstone, shale, and silty sandstone rock under the load of 12.5%–80% of the failure load.’ Subsequently, much research has been published on rock creep tests, including the uniaxial compressive creep test, the triaxial compressive creep test, the discontinuity rock shearing test, and field tests (Wawersik, 1974; Amadei et al., 1980; Okubo et al., 1991; Jin et al.,1995). A rheological model is used to describe the complex rheological deformation of material. This model is based on various fundamental parameters including rock elasticity, plasticity, and viscous properties, which can be combined into a constitutive model to reflect the rheological properties of various types of rocks. Wang et al. (2014) studied the creep– damage–rupture characteristics of rock salt by applying a creep-damage model. Munson (1997) developed a multi-mechanism constitutive model of creep of polycrystalline rock salt based on steady-state creep and modified it to incorporate transient creep through work hardening and recovery. An elasto-viscoplastic approach was developed to simulate the timedependent nature of the fracture zone (Malan, 1999). Rheological models were proposed to understand the collapse of iron ore mines in Lorraine by Dragan et al. (2003)."

Jan 1, 2016

Students The South African Institute of Mining and Metallurgy (SAlMM) places a high value on its student members, for these people will ultimately become corporate members and will, it is hoped, play an active role in the affairs of the Institute. Why should young persons at University or Technikon want to become members of our Institute? There are several reasons.

Jan 1, 1991

By B. Orgilbayar, B. Unursaikhan, S. Sukhbat, Ts. Zagarzusem, D. Baasanjav, L. Jargalsaikhan, E. Otgonjargal, N. Sugir-Erdene, Ts. Soyolmaa

This study has investigated the efficacy of the gravity beneficiation method based on gravitation and centrifugal forces for manganese ore. Powdered samples of manganese ores from the Unagad deposit in Mongolia were analysed for their element and mineralogical composition using ICP-MS and X-ray powder diffraction (XRD). The analysis presented the mineralogical compositions of the ores as hydro goethite, manganese minerals and magnetite, gangue minerals as quartz, albite, orthoclase and microcline of manganese ore. Manganese minerals are white in colour and have micro-veinlet, fine grained-aggregates associated with gangue minerals. The most important manganese minerals are hausmannite, pyrolusite, rhodochrosite, and manganosite. The composite of feed containing 17.31 % Mn and 36.3 % SiO2 was processed in a shaking table. In the experiment, a concentrate assaying 41.37% Mn was obtained from this composite with 65% recovery. In another experiment, f80=0.074 mm particle size ore was used in the MGS concentration test. A concentrate containing 38.34 % Mn with 75.2% recovery was produced in this experiment. The results showed that it is possible to obtain concentrate through gravity processing of manganese ore, which is an economically beneficial process for producing a product of a standard requirement. Keywords: Manganese ore, gravity separator, centrifuge, shaking table 1. Introduction

Jan 1, 2020

Book review Doyle, William S. Strip Mining of Coal; Environmental solutions. Park Ridge (New Jersey), 1976. 352 pp. $32. Surface mining of coal is still in its infancy in South Africa. The environmental repercussions following large-scale disturbance of the land surface, and the secondary effects of the disposal of waste products and effluents from mining, have not yet become apparent.

Jan 1, 1977

By R. P. Plewman

The Chemical, Metallurgical and Mining Society, from which The South African Institute of Mining and Metallurgy is descended, had as its coat-of-arms a green shield with a very flat gold chevron dividing the field into two. A crossed pick and shovel occupied the lower half, and an alembic (distilling vessel) and a flaming crucible occupied the top half.

Jan 1, 1982

By P. R. Jochens

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

Jan 1, 1981

By B. K. Loveday

A model for the leaching of non-porous particles by B. K. LOVEDAY*, Ph.D. (Fellow) A model has been developed for the prediction of the rate of leaching for an assemblage of non-porous particles in terms of size-distribution parameters. Expressions are developed for batch and continuous operation, and an example of the application of the model is given.

Jan 9, 1975

By F. L. D. Cloete

he above article by E. Barnea, which appeared in the January 1978 issue of the Journal (vol. 78, no. 6, pp. 143-145), calls for comment in view of the author's claims for the novelty of his proof. He states in his article that its main purpose is to give a mathematically acceptable proof by induction of the 'recently proposed' equation

Jan 1, 1978

By J. Meintjes

by I. J. BARKER and A. B. STEWART J. MEINTJES I read the above paper with considerable interest. I would like to point out, however, that it is fallacious to conclude that the adverse effects of a high inductive reactance on furnace operation can be cancelled by connecting capacitors in series - or for that matter, in shunt - with the power supply.

Jan 1, 1980

By By the staff of Gold Fields of South Africa

A diamond-drilling programme conducted from 1971 to 1973 by the Phelps Dodge Corporation revealed three complex sulphide ore-bodies in the highly folded Namaqualand mobile belt on the farm Aggeneys, some 65 km west of the small town of Pofadder on the road to Springbok in the northwestern Cape. Of these, the Broken Hill occurrence is the most promising.

Jan 1, 1980

By P. J. Nel, A. Täuber

SYNOPSIS A method is described whereby finely ground glassy granulated blastfurnace slag mixed with small quantities of clay, whiting and quartz has been used for making ceramic tiles in the laboratory. The tiles were semi-dry pressed and devitrification as well as sintering occurred during firing. The properties of the resulting product compared favourably in many respects with ordinary ceramic flooring materials.

By T. V. Owen

This paper describes the flotation of cassiterite from fine slimes at Rooiberg Tin Limited, and gives an of the Amdel on-line analysis system that was instaled in 1984 to aid in the control of the concentrate The system, which is easy to install and maintain, and which uses X-ray-fluorescence analysis, has improved control, and therefore a better recovery of tin.

Jan 1, 1988

By B. C. Alberts

Rapid and effective handling of run-of-mine, waste, and treated materials is vita.! to every step of resource development and recovery. Modern mine managements have planned and engineered systems for the handling of ever-larger tonnages. Where traditional methods have not proved to be costeffective and adequate, managements have pioneered the development of new materials-handling systems in the mining industry.

Jan 1, 1983

By C. F. Hews

Trackless mining at the International Nickel Company of Canada, Limited by C. F. HEWS* (Visitor) An account is given of the evolution and advantages of trackless equipment in the underground operations of International Nickel's Ontario Division, with special reference to fill-method mining, development practice, sublevel caving, and induced block caving. Details of maintenance, environmental control, and operator training are also given.

By M. J. King, W. K. B. Loftus, H. S. Simpson

SYNOPSIS The history of the early diamond fields and primitive methods of diamond recovery are traced, giving a brief description of the improvements made in final diamond recovery processes and techniques up to the present day. In particular the emphasis is on the effect of improved equipment in reducing final hand sorting time and labour, better security and greater recovery of fine diamonds.

By M. Akyüzlü

The equilibrium between carbon-saturated Fe-Cr-Si-C alloys and SiO2-CaO-MgO-A2O3-CrO2-FeOy slags was studied under atmospheres of argon and carbon monoxide at temperatures of 1500 and 1600°C. The equilibrium distribution of chromium, silicon, and iron between the slag and the metal phases was determined for different compositions of both phases under different atmospheres and temperatures. It is shown that silicon transfer from the slag to the metal increases with increasing temperature, decreasing carbon monoxide partial pressure, decreasing carbon content of the metal, increasing chromium-to-iron ratio of the metal, increasing silica content of the slag, and decreasing lime-to-alumina ratio of the slag. Some activity calculations were made for the experiments conducted at 1600OC in a carbon monoxide atmosphere. It is also shown that a decrease in the iron content and an increase in the slag basicity decrease the chromium content of the slag. A major proportion of the chromium present in the slag was found to be in the divalent state under the highly reducing conditions prevailing in the experiments. The chromous capacities of these slags were calculated and were found to decrease with increasing basicity.

Jan 1, 1992

By J. M. Stewart, C. H. Wyndham

Suggested thermal stress limits for safe physiological strain in underground environments by J. M. STEW ART M.Sc. (Eng) (Witwatersrand) (Visitor) and C. H. WYNDHAM M.B., D.Sc. (Witwatersrand), F.R.C.P. (Land) (Fellow) A comparison of safe temperature limits, based on Mitchell and Whillier's equations for specific cooling power (SCP), with similar limits determined experimentally shows the SCP-based limits to be unnecessarily conservative. It is argued that, while a small part of this conservatism may be attributed to an erroneous extrapolation of the heat transfer dependence on wind speed, the major part is probably due to the use of too Iowa limiting mean skin temperature in the calculation of SCP. A combination of Mitche/l's basic data with results available in the literature permits the derivation of modified heat transfer equations based on data that fully cover the range of wind speeds of interest. These equations, using a mean skin temperature of 36°C as the basis for the calculation of safe temperature limits, are then shown to agree favourably with those determined empirically. Furthermore, values of SCP based on these equations are shown to correlate reasonably well with wet kata readings, giving positive support to the wet kata thermometer as a heat stress meter.

Jan 8, 1975