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By B. C. Alberts

An international conference on 'The Planning and Operation of Open-pit and Strip Mines' was held at University of Pretoria from 9th to 13th April, 1984. The Conference was organized by the Mining Alumni Society the University of Pretoria and The South African Institute Mining and Metallurgy. Delegates of the mining fraternity from all over the world and Southern Africa attended the Conference. These included more than 400 delegates from Australia, Austria, Botswana, Brazil, Canada, Germany, Holland, SWA-Namibia, the United Kingdom, the United States of America, Zimbabwe, and South Africa.

Jan 1, 1984

By E. J. Boome, A. C. Schmidt

Pert, and how Pert techniques can be used in modern mine management By E. J. Boome, A. C. Schmidt C.A. (S.A.) This paper covers the stages of planning required to be performed and the implementation of the plan from grass roots to the partial completion of the sinking of a mine shaft system. The various steps involved in the planning are also examined in some detail. The experience gained in this project and the conclusions reached convince the authors that Pert Planning is a valuable aid to top management.

By A. L. Hinde, P. J. D. Lloyd, A. R. Atkins, J. G. MacKay

The control of milling circuits by A. R. ATKINS, M.Se. (Elee. Eng.) (Visitor), A. L. HINDE, S.Se., Ph.D. (London) (Visitor), P. J. D. LLOYD, S.Se. (Chem. Eng.), Ph.D. (Cape) (Fellow) and J. G. MACKA Y, S.Se. (Chem. Eng.) (Visitor). The general behaviour of mills is described in an attempt to find a control philosophy that will permit milling circuits to produce a constant particle size. Although the experimental work has been confined to a single section of the milling circuit of one mine, it is felt that the findings are applicable to other milling circuits.

Jan 6, 1974

By J. E. Forbes

Oxygen enrichment of the converter air at Rustenburg Platinum Mines by J. E. FORBES (Associate Member)* An account is given of the adoption of oxygen enrichment to accelerate converting operations and so permit the handling of larger quantities of feed materials. In addition to achieving its object, the use of oxygen-enriched air (6 per cent oxygen by volume) results in an increase in the concentration of sulphur dioxide in the converter off-gas. The slags have the same composition as those produced without oxygen enrichment, and the operation of the converters is easily controlled.

Jan 1, 1977

By H. A. D. Kirsten

The paper reports on loading tests conducted on shotcrete reinforced with mesh and various types of steel fibre, and compares the results with the energy absorbing capabilities of 16 mm rebar shepherd's crooks. It is concluded that mesh-reit1forced shotcrete has sufficient energy-absorbing capabilities to contain rockbursts of significant magnitude, having greater energy absorbing capabilities, even at a thickness of 50 mm, than 16 mm rebar shepherd's crooks. Fibre-reinforced shotcrete has energy absorbing capabilities of the same order as, or better than, those of 16 mm rebar shepherd's crooks, but its performance is erratic.

Jan 1, 1995

By H. M. Friede

Mining was a widespread economic activity in the African Iron Age. This paper reviews the available evidence on, the archaeological, historical, ethnological, and technological aspects of early mining in the Transvaal. A number of analyses of ores found at archaeological sites (especially at Broederstroom) are reported, and an interpretation of the analytical results is suggested. Descriptions of Iron Age copper- and tin-mining complexes, and of iron-ore workings, are given, and techniques of Iron Age mining are discussed. The evidence of gold mining in Iron Age Transvaal is examined.

Jan 1, 1980

By C. Hey

The cycloned gravitated tailings backfill system, also referred to as a soft or low density fill, has been implemented at Vaal Reefs. Inhibiting the success of the system was the problem of shrinkage after placement. The problem was overcome by a pressure fill technique which eliminated settlement, contained costs and allowed remote placement. The technique involves the preinstallation of disposable pipes which are filled cyclically until a residual pressure of 0,5 bar of active support is generated in the filled paddock.

Jan 1, 1988

The support of stopes by means of yielding timber props, with or without hydraulic props, is common in the mining industry. This paper discusses the ability of these support systems to absorb energy during a rockburst, and further investigates their capability to withstand a range of ground velocities. It is found that the rate of stope closure prior to a rockburst strongly influences the behaviour of these support systems during the rockburst. It is recommended that hydraulic props be used in conjunction with yielding timber props in these conditions, and that yielding timber props with an increased yield range are desirable.

Jan 1, 1991

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 H. M. Friede, R. H. Steel

Tin mining and smelting in the Transvaal during the Iron Age by H. M. FRIEDE*. Ph.D. and R. H. STEEL* (Visitors) This paper reviews the historical, archaeological, and metallurgical evidence on Iron Age tin mining and tin smelting in Southern Africa. The results of the analysis of twenty samples of tin ore, tin slag, and tin ingots found associated with Iron Age materials in the Transvaal (mostly in the Rooiberg area) are reported and discussed. The types of ingots preserved in local collections are described. A small experimental tin-smelting furnace was constructed and worked according to traditional African Iron Age technology. Qualitative and quantitative results of this experiment are reported.

Jan 7, 1976

By H. J. S. Kriek

Methods are described by which increased production is achieved whilst retaining full availability of equipment and decreased refractory cost. Refractory materials have certain limitations, and when these limitations are known the variables in operating practice having the greatest impact on refractory life can be controlled. The most important factors to be closely controlled are porosity, chemical constitution of refractory materials, slag basicity, slag volume, FeO content of slag and temperature at which the process is operated. Knowledge of the process is invaluable in deciding on the type of refractory to be used. The types of refractories used in and the operating variables of the ironmaking, steel making and steel finishing units are described.

By H. M. Friede

An experimental study of iron-smelting techniques used in the South African Iron Age by H. M. FRIEDE, Ph.D. and R. H. STEEL (Visitors) The main factors involved in the primitive smelting of iron (ore, charcoal, temperature, air supply, process control) were evaluated in an experimental furnace that was constructed to the pattern of an Iron Age furnace found at Melville Koppies Nature Reserve, Johannesburg. In particular, the characteristics, action, and efficiency of skin bellows were investigated to gaina better understanding of the air-supply system used. Sixteen specimens of iron ore, slag, and metallic iron (excavated material and material produced in the experimental furnace) were submitted to analysis. The results of the analyses are reported and discussed.

Jan 6, 1977

The 90th Annual General Meeting of The South African Institute of Mining and Metallurgy was held at Kelvin House, Johannesburg, on 19th August, 1987. Dr H. Wagner (President) was in the Chair and declared the meeting open at 16h00. Obituaries The President read out the names of the departed Members as follows: N.M. Airey, F.J. Kisbey-Green, Dr R.A. Pelletier, C.B. Anderson, A.R. Cator, J. van Heerden, P.J. Burman, C.C. Crosson, M. Livingstone¬Blevins, S.T. Firman, V.E. Kisbey-Green, and A.L. Corna. All stood and observed a moment of silence as a mark of respect. Minutes The minutes of the 89th Meeting of the SAIMM, which was held on 20th of August, 1986, were confirmed.

Jan 1, 1987

By D. D. Marsden

This paper discusses the concentrations of sulphides and total sulphur in widely spread regions around mine residue deposits, from which rain-water run-of can enter the Vaal River system. Analyses of borehole samples from several deposits are used to establish typical sulphur head grades. It is shown that a high percentage of al the oxidizable, and hence leachable and pollution-causing, sulphur has already been removed. When the residues were fresh, water that came from the deposits was highly polluted, but the dissolved solids from these residues are today of very minor significance. The data are supported by analyses of the drainage streams.

Jan 1, 1986

By D. R. Hardman, J. W. Oberholzer

Based on information supplied by South African collieries to the Coal Mining Laboratory of the Chamber of Mines since 1978, the paper outlines the general performance of the continuous miners used and gives the results more-detailed studies of the cutting, loading, and transportation processes. On average, the continuous miners produced coal at a rate of 76 t per operating hour, which, at an average machine availability of 67 per cent, resulted in a production of 51 t per total hour. The cutting rates varied between and 250 t/h but, owing to machine and system inefficiencies, the overall production rate varied between 92 and 48 It is concluded that, if the collieries concentrated on improving their machine utilization procedures and operating practices, they could increase the overall production from their continuous-miner sections.

Jan 1, 1987

By A. Koursaris, H. M. Friede, A. A. Hejja

The features of smelting slags from South African prehistoric sites and of related cinder material are described. Chemical analyses of twelve slag samples found in the Transvaal, Swaziland, and Botswana are reported and discussed. An attempt is made to establish a relationship between these slags and the ores collected at the Early Iron Age site of Broederstroom, which date between AD 350 and AD 600. The liquidus temperatures of29 slags were determined by the use oh hot-stage microscope. The major mineral phases of 16 slags were identified by X-ray diffraction and microscopic examination. It appears that the slags investigated were formed at temperatures below 1250°C or - in some cases - at temperatures only marginally in excess of 1250°C.

Jan 1, 1982

By J. D. Flint

A description is given of the extraction of pillars in a seam of coal which normally varies in thickness from 10 feet to 14 feet using conventional trackless mechanised units. By using the pocket and fender method of pillar extraction, the high capital cost of hydraulic supports is eliminated, and a volumetric extraction of 85% to 90% of the seam of coal is possible. This method of mining opens up the possibility of extracting vast tonnages of coal which hitherto would have been left in situ as pillars. The major benefits likely to accrue from this technique are seen as follows: 1. Greater volumetric extraction of the seam; 2. Longer panel life with less frequent transferring of sections; 3. Preservation of our natural resources. The authors deal with the history of this development at Springfield Colliery, discuss the present results and outline the future trends in the light of current experience.

By K. R. Vost

Variation in air temperature in a cross-section of an underground airway by K. R. VOST, B.Sc. (Glas.), M.Sc. (N.S.W.) (Visitor) Measurements of air temperatures in underground airways are normally made at only one point in a cross-section, and the air tem peratures at other points in the cross-section are assumed not to differ significantly from this. This paper discusses measurements made at a number of points in fifty crosssections in airways with different air velocities and wetness of floor. These measurements show that significant variations of air temperature can occur in a given cross-section at a given time. The effects of such variations on the accuracy of measurement of rises in air temperature as air passes along an airway are discussed. The importance of considering experimental error in the measured rises in air temperature when attempting to validate theoretical and empirical methods of predicting such rises is also discussed.

Jan 7, 1976

By H. M. Friede, R. H. Steel

Notes on Iron Age copper-smelting technology in the Transvaal by H. M. FRIEDE, Ph.D. and R. H. STEEL (Visitors) Earlier reports on Iron Age copper metallurgy and copper-smelting techniques in the Transvaal are surveyed, and a description and tentative classification of the copper furnaces are given. The analyses of furnace slags and sherds of glazed crucibles from archaeological sites of the Transvaal and the neighbouring Orange Free State pro. vide evidence of copper smelting there in Iron Age times. . An investigation conducted by the Department of Archaeology of the University ofthe Witwatersrand provided information on the details of furnace construction and smelting processes, on the composition of the materials used and produced, and on the making and handling of tools and accessories, such as bellows and tongs, needed by Iron Age smelters. Three models (the KaondejVenda furnace, the Rooiberg crucible furnace, and the Uitkomst furnace) were constructed and operated as a demonstration of Iron Age copper smelting as it was practised in the Transvaal.

Jan 11, 1975

By L. E. Kun, R. O. Oelofsen, E. J. J. van Vuuren

High-rate floc-blanket clarification of gold pregnant rotary filtrate was introduced at the Vaal Reefs South gold plant of the Anglo American Corporation during February 1978. A. daily 12 000 to 15 000 t of filtrate, with an average suspended-solids concentration of 350 mg/I, is continuously clarified to a concentration of less than 2S mg/I of suspended solids in a modified plant pachuca (10 m in diameter) at throughput rates of 7,7 to 8,5 ma/m2.h by the addition of 5 g/t of ferric chloride inorganic coagulant and 0,2 g/t of Superfloc NI00 flocculant. The pachuca overflow is then clarified further in seven Stellar candle pressure filters of 54,S m2 surface area to under 5 mg/I of suspended solids. The combined clarification cost when the hopper clarifier is used in conjunction with the Stellar filters is R0,0032 per ton of liquid treated, which is approximately 60 per cent lower than the cost of Stellar filtration on its own. The savings are mainly due to the reduced use of filter pre-coat, the consumption of which has dropped by 70 per cent since the introduction of hopper clarification.

Jan 1, 1979