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The 89th Annual General Meeting of The South African Institute of Mining and Metallurgy was held at Kelvin House, Johannesburg, on 20th August, 1986. Mr. H. E. James (President) was in the chair and declared the meeting open at 16hoo. Obituaries President: It is my sad duty to announce the deaths of the following members of this Institute: Life Fellow D.L. Carson; Retired Fellows T.K. Adams, G.E. Carlyon, N.M. Holford, D.E. Maclver, C.J. Morgan; Fellows S.K. de Kock, R.R. Porter, Dr G.J. Rees; and Associate Sir Lindesay Clark. As a mark of respect to the memory of the deceased and in sympathy with the bereaved, please rise and observe a moment of silence. Minutes President: The 88th Annual General Meeting of the Institute was held on Wednesday, 14th August, 1985, and the minutes were published in the September 1985 issue of the Journal. The minutes were confirmed.

Jan 1, 1986

The optimization of sample spacing In South African gold mines by J. M. RENDU*, Eng. Se.D., M.S. (Min.) U.S.A. (Graduate Member) A first attempt is made at optimization of sample spacing in South African gold mines. The De Wijs model, which is shown to give a good representation of the geostatistical properties of gold values, is used to analyse the influence of the distance between samples along a stope face on the error of estimation of the stope value. The influence of other factors such as the face advance before resampling, the sample density, and the stope size, is also considered. Practical conclusions are drawn concerning the optimum sampling policy to be followed in various situations, and it is shown that sampling on a regular grid does not necessarily give the best results.

Jan 4, 1976

By B. M. Wainstein

An extension of lognormal theory and its application to risk analysis models for new mining ventures by B. M. WAINSTEIN*, B.Sc., M.B.A. (Witwatersrand) (Visitor) The lognormal distribution, which remains the most popular distribution model for ore values, is investigated. The T-distribution, an integral part of this theory, is dependent on the sample size, n, and the unknown population parameter, o2, which cannot be integrated out. Hence, o2constitutes a nuisance parameter. In this study, the robustness of the T-distribution to changes in o2 is examined. It is found that the T-distribution is robust for 0,1 <= o2 >= 2,5, a domain covering most practical applications of the lognormal theory. By the use of o2 = 0,7, multiplier factors, which facilitate the computation of the confidence limits, are derived for a comprehensive set of confidence levels.

Jan 4, 1975

1. Book review Respiratory protection - principles and applications by B. Ballantyne and P. H. Schwa be (Editors). London, Chapman Hall, 1981. (Reviewer: M. J. Martinson) 2. New manual Swedish steel manual, 1981. Available from Jernkontoret, P.O. Box 1721, S-I11 87 Stockholm, Sweden. SEK 85. 3. Publications of the Mineral Policy and Energy Sectors, Canada General review by L. Tibbo. 10 pp. Columbium (niobium) and tantalum by D. G. Fong. 6 pp. Sulphur by B. W. Boyd. 13 pp. Statistical summary of the mineral industry in Canada. 66 tables. Uranium by R. M. Williams. 16 pp. 4. Mintek reports Report 2126 The determination, by microwave techniques, of the interface between pulp and froth. Report 2129 An electrode controller for submerged-arc furnaces. Report 2131 The separation of trace elements in manganese dioxide. Report 2132 The assessment of pellicular anion-exchange resins for the determination of anions by ion chromatography. Report M2 The preparation of two reference materials of South African fluorspar. Report M3 The platinum-group minerals in the UG-2 Layer of the Bushveld Complex at Maandagshoek 254KT.

Jan 1, 1982

In a gold CIP/CIL circuit, adding new circuit water to a final tails thickener and then directing the thickener overflow to the head of the circuit significantly reduces the cyanide concentration at the TSF discharge spigot. The new water is used to dilute the final tails. The dilution and recycle of the tails in this manner may have the added benefit of reducing reagent consumption, in some cases to the point where the reagent savings justify the expenditure and Cyanide Code compliance is achieved at no extra cost. Potential circuit configurations and water recycles can be modelled by splicing a flowsheeting and thermodynamics package, such that changes to the composition of the water can be reduced to chemical speciation with a Gibbs free energy minimisation enabling a complete understanding of the circuit water chemistry.

Jan 1, 2007

The imbalance between the coal resources contained in thin seams (1,5 m or less) and the production from them is outlined. It is suggested that an Increase In the exploitation of thin coal seams is necessary, and that drum-type continuous miners can produce a substantial amount of any increase. Continuous miners are employed in a number of mining methods including bord-and-pillar, pillar extraction (stooping), rib-pillar extraction, and shortwalling. These techniques of mining are evaluated with respect to production rates and the cost of extraction for South African conditions included in these evaluations are the types of equipment used to transport coal from the mining machine to the section conveyor belt. Computer simulation techniques are used to generate the required production levels, and interpretations are made of other results from the computer modelling. For thin, coal seams, bord-and-pillar mining utilizing continuous haulage is apparently the most productive and cost-effective of all the methods using the continuous miner. The relative efficiencies of the other techniques of mining and of coal-transportation vehicles are also outlined.

Jan 1, 1984

By I. D. Wood

Deposition of gold-bearing deposits in the Witwatersrand Basin was controlled by hydraulic processes. These resulted in the formation of independent sedimentological facies areas having different statistics and semivariograms. Consequently, when there are indications that data are a mixture of statistical populations, it is important to decompose them into statistical subpopulations and analyse these independently. However, in the case of actual mining, physical position and extent of sub- populations are important and, as a consequence, any decomposition of data must take space into account if it is to be of use. An algorithm for the spatial decomposition of data into its sub-populations is described and is applied to real data taken from the Witwatersrand. Two distinct areas with completely different geostatistical parameters were revealed.

Jan 1, 1987

By P. N. Harris

On 23rd November, 1982, a party of 80 members of The South African Institute of Mining and Metallurgy left the Wanderers Club grounds at 07hOO, and were driven in two luxury coaches to the stainless-steel mill of Southern Cross at Middelburg. Southern Cross is a trade name adopted by MS & A (Middelburg Steel and Alloys), who operate two Alloy Divisions (at Middelburg and Krugersdorp) and one Steel Division (at Middelburg). METAL &apos;83 The International Precious Metals Institute has scheduled a seminar on the platinum -group metals for Williamsburg, DB.A., on 10th to 13th April, 1983, and has announced its keynote speakers for each of the seminar&apos;s five sessions. Metee &apos;83 METEC - the International Exhibition for Metallurgical Technology and Equipment with Congress - which was to have been held in Dusseldorf from 14th to 20th May, 1983, has been cancelled, and will probably take place in June 1984. Sampling Sampling and sample preparation are crucial activities in many areas of chemical engineering, in the energy and food industries, in metallurgical processes, and in mining and mineral engineering.

Jan 1, 1983

By K. R. Johnson

Changes in the pattern of computer systems for mine planning and geologic evaluation are occurring as a consequence of the introduction of 3-D high performance graphics terminals. The VULCAN system is described and an outline of its functionality is discussed. Increasingly, the integration of both database systems and graphics and databases will occur, allowing a greater degree of information access to mine operators. The system covers areas of database, drillhole graphics, mine design and layout, surface and solid modelling as well as reserve inventory generation. The design of the software is such that it is fairly commodity-independent and entirely menu-driven, to enable non computer-trained personnel easily to access the system.

Jan 1, 1987

By I. H. Clark

In some mining situations, backfills are not only required to be free-standing but are also expected to provide hangingwall support. It may therefore be specified that the backfill withstand a certain calculated stress within a given time. Given the materials available, the choice of backfill composition is not always straightforward, and an approach to the evaluation of cemented tailings backfill is therefore proposed. The general use of such a method will greatly assist in both the scientific analysis of the material properties for industry-wide purposes of comparison and decision-making as regards the choice of fill.

Jan 1, 1988

In Chapter 1 we mentioned that up to three components are considered to represent the variability of regionalized variables : a deterministic component, a correlated component, and a random component. In Chapter 2 we considered some of the models based on the assumption of randomly distributed values: the random component was assumed to be the only one present. In Chapters 3 to 11, more general but also more complex models were described, based on the assumption that the values were correlated with the possible presence of random noise. In this chapter we introduce a model used to analyse non- stationary data, for which a deterministic component (or drift) must be assumed. This model will be used for estimation purposes, and the corresponding optimal linear estimation procedure is known as universal kriging. The theory of universal kriging is much more complex than the theory of kriging. Fortunately, in the majority of mine valuation problems the drift can be ignored and the simpler form of kriging can be used.

Jan 1, 1978

By G. A. Bezuidenhout

Lonmin Platinum installed a concentrated mode dual-alkali scrubber at the smelter in Marikana in 2002. The dual-alkali scrubber was the technology of choice at that time as a sulphur fixation plant, due to the perceived benefits of handling both the high SO2 concentrations of converter off-gas and the swings in SO2 concentration that are linked to Peirce-Smith operation. Owing to current and impending legislative requirements for air quality and waste, Lonmin is currently considering additions to the dual-alkali plant, but is also evaluating alternative technologies for sulphur fixation. This paper reviews the decision of Lonmin to install a concentrated mode dual-alkali scrubber and presents plant performance achieved. It also describes the important control variables and sensitivities of the plant, and the final product that is produced by the operation of the plant. The legislative requirement that drives the Lonmin technology evaluation is also discussed.

Jan 1, 2012

By M. U. Ozbay

The stability of pillars is analysed on the assumption that pillars shed load in a stable manner if the slope the strata load-deformation relation is steeper than that of pillars in the post-peak regime. Concepts of local stiffness, mine structural stiffness, and critical stiffness are discussed. Procedures are described for the determination of strata stiffness for various pillar layouts by use of the available boundary-element computer programs. The postpeak stiffness of pillars is assessed from the available data relating to the post-peak load-deformation relationship and width-to-height ratio. Stability analyses are carried out by the contrasting of strata stiffness with post-peak pillar stiffness. It is shown that the strata stiffness becomes unacceptably small for a stable yield-pillar layout when the span exceeds about 5 times the depth. The strata stiffness is found to increase, thereby increasing the stability, as the span-to-depth ratio, number of pillars, and percentage extraction are decreased. It is also found that the stability in a yield pillar becomes difficult to achieve when al the pillars in a layout are in the descending part their post-peak load-deformation curve

Jan 1, 1989

By M. Pötsch, M. Blümel, E. A. Button

ABSTRACT: Stiffness controlled test procedures performed with servo-controlled shear systems are the most versatile for simulating the wide range of boundary conditions expected in nature. Examples of a function controlled procedure in addition to dilatation controlled procedures are discussed for different characteristic behaviours. ZUSAMMENFASSUNG: Steifigkeitskontrollierte Scherversuche mit servohydraulischer Steuerung eignen sich gut unterschiedliche Bettungen, wie auch in der Natur vorkommen, zu simulieren. Beispiele für spezielle Steuerungsfunktionen und dilatationsgesteuerte Prozeduren mit verschiedenen charakteristischen Eigenschaften werden diskutiert. RESUMÉ: La rigidité a commandé des méthodes d&apos;essai exécutées avec les systèmes asservis de cisaillement sont la plus souple pour simuler l&apos;éventail d&apos;états de frontière prévus en nature. Des exemples d&apos;un procédé commandé par fonction en plus des procédures commandées par dilatation sont discutés pour différents comportements caractéristiques.

Jan 1, 2003

By SHM Harkema, MKG Vermaak, D R. Groot

Surface Plasmon Resonance spectroscopy (SPR), combined with cyclovoltammetry, has been successfully used to study the interactions between ethyl xanthate, heptyl xanthate, dithiophosphate and propyl trithiocarbonate flotation collectors and a gold surface. Large, easily measurable responses have been obtained in the potential areas where the thiol collectors are known to interact with gold. The four collector types lead to differing SPR maximum values, with longer alkyl chains resulting in higher SPR responses, and the trithiocarbonate leading to the highest response values. The SPR responses differ considerably from the current density response at very anodic and cathodic potentials. There are indications that thiols might still be adsorbed at potentials as low as -300 mV (vs SHE). Keywords Flotation collectors; thiol collectors; cyclovoltammetry; surface plasmon resonance spectroscopy.

Jan 1, 2005

By R. S. J. Du Toit

SYNOPSIS This paper is based on a thesis dealing with the problem of basing the current rate at which money is collected from mine owners to pay compensation for pneumoconiosis in the future, on the current dust hazard on mines. The certification of pneumoconiotics and the incidence of pneumoconiosis are discussed against the background of existing legal provision for collecting funds for compensation. The various pneumoconiosis indices are considered. In the data analyzed, the only pneumoconiosis index common to a number of classes of mines is the time it takes to develop pneumoconiosis. Sets of dust indices and pneumoconiosis indices are computed. Expressions are derived for the time it takes to develop pneumoconiosis as a function of the dust hazard, and for the collection of funds as a function of the time available for collection. From these two expressions follows an expression for the rate of collecting funds as a function of the dust hazard.

By H. D. Mtegha

The Southern African Development Community (SADC) aims to harmonize mineral policies and regulatory regimes in the minerals sector. This paper provides a review of the progress made towards harmonization of mineral regimes in the region. It singles out only the mining fiscal environment, as this is normally one of the key issues of interest to potential investors as well as the host state. Indications are that the region is slowly progressing towards a more harmonized approach, and there is evidence that the ?race to the bottom? has been prevented, which is the basis for an integrated mineral sector that the region aspires to.

Jan 1, 2011

By M. J. U. T. Van Wijngaarden, R. J. Dippenaar

An electrochemical technique based on the solid oxide galvanic cel Mo / Mo + MoO2/ ZrO2-MgO / Fe + (FexO)slag + Ag / Fe was used in a determination of FexO activities in liquid slag systems. The emf measurements, scanning electron microscopy, and microprobe analysis of the cross-sections of the electrolyte tubes used in direct contact with the slag melts indicated that slag attack did not affect the open-circuit emf values during normal cell operation, The reliability of the cell was confirmed by the good agreement between the standard free energy of formation of liquid Fep obtained in the present study and those reported in the literature, The FexO activities were determined in FexO -CaO and FexO-SiO2 slags at 1673 K, and are in good agreement with those measured by the conventional gas-equilibrium technique. The experimental technique was successfully extended to the measurement of Fe2O activities in the complex slags that are used for the external desilliconization of the hot metal product of the blast furnace.

Jan 1, 1986

By J. Dvorácek

Mine water poses a significant problem in lignite coal mining. The drainage of mine water is the fundamental prerequisite of mining operations. Under the legislation of the Czech Republic, mine water that discharges into surface watercourse is subject to the permission of the state administration body in the water management sector. The permission also stipulates the limits for mine water pollution. Therefore, mine water has to be purified prior to discharge. Although all mining companies operate mine water treatment plants, there is hardly any utilization of the final effluent. The high expenditure involved in the more sophisticated methods of mine water treatment has fuelled the search for the commercial utilization of the effluent.

Jan 1, 2012

By N. C. Joughin, A. C. Buckmaster

The use of face conveyors in gold mines by N. C. JOUGHIN. B.Sc. (Eng.). Ph.D. (Wits) (Member) and A. C. BUCKMASTER; M.A. (Cantab.) A mechanized stope-cleaning system has been developed around an armoured face conveyor, which was tested on the surface and in two underground trials. In the second underground trial, an average face advance of 8,5 m per month was obtained with a labour productivity of 27 ca/worker/month on a two-shift blast cycle. Two new face cleaning systems have been built, each incorporating an armoured face conveyor, a loading plough, a collapsible self-advancing barricade, and an integral roof-support system. These are about to be tested. A new type of reciprocating flight conveyor is being developed for stope use. This is cheaper, lighter, and more compact, and exhibits better wear characteristics, than an armoured face conveyor. In the early stages of the trials, this conveyor frequently achieved a singleshift blast cycle. It should be possible to achieve face advances of up to 40 ca/worker/month with a consistent one-shift blast cycle. The use of drill rigs and a self-advancing roof-support system would improve the productivity to over 50 ca/worker/month.

Jan 2, 1976