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By P. G. Henderson, G. C. Thompson

The organization and mechanized colliery management of a large by G. C. THOMPSON, B.Sc. (Min. Eng.) (Witwatersrand), M.B.L. (Member), and P. G. HENDERSON, B.Sc. (Min. Eng.) (Pretoria), M.B.A. (Member). Usutu Collieries Limited, at present the largest single producer of coal in South Africa, supplies Cam den power station. and produces 435 000 tonnes per month by conventional mechanized methods from bord-and-pillar workings in three mines. The thickness of the seams averages 2 metres, and the depth below surface varies from 15 to 150 metres. Each mine depends to a different extent on certain common facilities and services. Two of the mines are located on the same coalfield, and their rationalization would possibly be advantageous. Production policy is one of productivity with flexibility. The double-loader system is widely used, and one section at each mine is worked on single shift. Pillar extraction is practised where possible. In addition to lubrication and inspections, planned maintenance of mining equipment consists of sub-assembly replacements and overhauls. Conveyor and tractor/trailer transport is used underground. but trolley-wire locomotive haulage is being considered. The organization is such that co-ordination is relatively difficult, and certain changes could possibly improve the functioning of the engineering and mining departments. Technical and management training is carried out. Long-term planning will make use of a computer programme and will involve the investigation of other mining methods. Five-year and twelve-month plans are prepared, the planning of coal quality being based on the view that the mine and the power station together constitute a system. Control information systems make use of a remote computer terminal located at the mine. An improved integrated system is being investigated.

Jan 3, 1975

By J. A. L. Napier

The evaluation of stress distributions and deformations in the vicinity of tabular mine layouts has been carried out routinely for many years using the displacement discontinuity boundary element method (DDM). In this approach, mine layouts are approximated as irregular shaped planar cracks (or slits) where the ?width? of the crack, corresponding to the excavation height, is assumed to be negligible compared to the in-plane, lateral dimensions. Early implementations of this approach have employed square element tessellations with constant displacement discontinuity component values. This is generally restrictive when considering the analysis of irregular pillar layouts or the intersection of fault planes with excavations. This paper describes a general revision of this approach in which triangular or quadrilateral element shapes are introduced in conjunction with higher order variations of the displacement discontinuity shape functions. This facilitates an accurate evaluation of detailed stress and displacement components close to excavation surfaces and allows the investigation of local damage and failure behaviour associated with particular geological structures such as weak parting bands or weak layers. A method to embed these features in an efficient and accurate multi-level solution scheme is described. This formulation can be extended to allow the analysis of shallow-depth pillar layout problems, facilitating the assessment of the interactive response and stability of shallow depth pillar layouts. A simple deformation model is introduced to facilitate the assessment of pillar failure and bursting potential in shallow mine layouts. The computational techniques described here have been implemented in a computer code called TEXAN (Tabular EXcavation ANalyser) and are illustrated by the simulation of a particular multiple reef pillar mining problem in a shallow depth platinum mine.

Jan 1, 2007

By J. Danoczi

South Africa is running out of fresh water and is looking at ways to improve water usage. This report addresses how a diamond mine in Gauteng has improved the utilization of its water resources. In the past, water from the local river was deemed the most suitable to use in the grease recovery plant but subsequent tests on the water from the slimes dam have shows that this water source is in fact more suitable for diamond recovery. Utilizing the slimes dam water provides a more stable water source than the local river while also reducing the impact of the mine on the water resources in the area.

Jan 1, 2008

Keywords: Pyrometallurgy, zinc, electrowinning Zincor has been producing zinc since 1969 via the roast-leach-electrowinning process. It is the only primary zinc producer in South Africa, and currently supplies the entire country with zinc. The plant was built by Goldfields of South Africa, on the site of an old gold and uranium mine. Since then, the ownership of the plant has changed a couple of times, and the plant and process have also been improved. Production output has increased from around 80 000 tons per year to more than 110 000 tons per year. This was done mainly through increasing the capacity of the roasters and acid plant. Zincor produces four main grades of zinc: SHG, Zn1, Zn2, and Zn4, in three shapes: a 25 kg ingot and 1 and 2 ton jumbos. In 2005, a pre-alloy furnace was built that enabled the production of jumbos pre-alloyed with aluminium. This has allowed Zincor's customers to improve the efficiency of their continuous galvanizing lines and to lower their production costs.

Jan 1, 2006

By C. J. Van Niekerk, C. C. Begley

SYNOPSIS The paper opens with brief descriptions of the history, occurrence, and regional geology of South Afri¬can zinc deposits, and follows with descriptions of the resources, mining methods, and processes for the concentration of the sulphide minerals and the extraction of zinc as practised in South Africa. The end uses in the form of alloys or as salts are given in some detail. Statistics on the production and consumption of zinc in South Africa are given, and the current market situation and future prospects are discussed briefly.

Jan 1, 1991

By L. A. Vermeulen

Electronic circuits were developed and successfully utilized to record, store, and continuously transmit to a remote station physical information relating to the impacts of pebbles on the shell liners of an industrial pebble mill, and of electrical conduction in the mineral pulp. The information was obtained by the instrumentation of some of the bolts that are used to clamp the liner blocks and litter bars to the mill shell. The features associated with the impact and conduction signals have been interpreted, and it is shown that such signals can lead to continuous measurements of the volume of the load in an industrial mill. Information is given regarding the angular distribution of direct impacts of the pebbles onto the shell liners, the power required to promote impacts, the amount of material in flight, the impact velocity, and the average number of direct impacts with the shell liner that any given pebble undergoes in unit time in the given mill.

Jan 1, 1984

n interesting situation arose last week when two Vaal River residents wrote to me (and a third telephoned) giving me details of how Sasol wanted to develop an open-cast coal mine on the south bank of the Vaal, just upstream of the Barrage. This is agricultural land and is across the river from Millionaire?s Row, where a number of wealthy people have built river-side mansions. The mine would be hidden by a 30 m-high (10 storeys) earth wall set 300 m back from the edge of the river. It could operate 24 hours a day.

Jan 1, 1996

By O. K. H. Sheff

Despite many years of a successful policy for our Journal, the Journal Committee is in the course of adopting a new approach with which to enter the present decade. The objectives are to improve the readability of the Journal, without forfeiting the quality achieved in the past, by adding an extra dimension through the inclusion of applied-engineering papers, i.e. technically oriented papers.

Jan 1, 1990

By B. Litt, D. L. Van Coller

Job evaluation and the changing wage pattern by D. L. VAN COLLER, B.A.(Cape Town), M.A., B.Litt.{Oxon.) (Visitor) This paper sets out to show how changing forces are affecting the techniques that have been used in the evaluation of Black jobs on gold mines in the Anglo American Group since the introduction of job evaluation in 1961. Initially, job evaluation was essentially a management tool designed to differentiate jobs in a limited skill spectrum and thereby permit the establishment of a 'many stepped' job ladder for Black employees to climb. With the changing wage pattern, job evaluation is becoming an industrialrelations tool aimed at recognizing the skill and effort contributed by the worker so that the pay relationships between jobs are seen to be equitable by the employees.

Jan 8, 1974

The compilation of the sampling nomogram is an essential tool in the optimization of a sampling protocol and allows the operator to track the change in relative variance of the sampling error (the Fundamental Sampling Error) during steps of comminution and mass reduction in the process of recovery of the aliquot for analysis. The data required for the compilation of the nomogram are centered on the sampling constant K and the exponent, alpha (a), of the nominal fragment size. Five methods for establishing K have been identified, but two of them, the duplicate sampling analysis (DSA) method and the heterogeneity test (HT) method purport to provide such a constant. The step by step procedure for each of these two methods was examined using broken ores from three mines, Mponeng mine, Kloof mine and Lily mine. Two of these mines (Mponengand Kloof) are typical Witwatersrand-type gold mines, while the third is an Archaean-type, shear related gold deposit situated in the Barberton Greenstone belt. The results suggest that the factor K derived using the heterogeneity test is very accurate, but applies only to a single size fraction in the spectrum of comminuted materials. The calculation of gold grain sizes using this method appears to be too small and does not conform with the results from detailed mineralogical studies. The factors K and alpha derived using the duplicate series analysis, are appropriate for use across a wide spectrum of comminution sizes and also provide realistic gold grain sizes, comparable with the equivalent circular diameter of gold grains identified in mineralogical studies of the ores.

Jan 1, 2009

By M. A. Ford

This paper reviews the history, sources, mineralogy, extraction metallurgy, conversion, and enrichment of uranium in South Africa. Over the past 40 years extraction plants were built at 27 sites, an9.over 140 kt of uranium have been produced. Older plants have had to adapt to changing market conditions, no single technology has had the opportunity to become entrenched, and costs have been reduced to a third of those of the original flowsheet. The research efforts aimed at developing the country s nuclear raw materials have been particularly rewarding, as they have enabled South Africa to become a world leader in the extraction of uranium from low-grade ores and to develop methods for uranium enrichment and the production of nuclear fuels.

Jan 1, 1993

By A. Nicotra, E. H. Roux, J. H. du Plooy, D. H. de Jagger, P. De Waal, G. J. van der Linde

This paper reviews the geology, history, current beneficiation practices, uses, marketing, and future outlook of phosphate in South Africa. The vastness of the reserves, and the industry's efficiency and competitiveness in world terms, are highlighted.

Jan 1, 1989

By L. A. Abichequer

ROM grade variability is one of the most important factors influencing plant product recovery. Due to the influence of grade variability on mine profits, it is deemed important to guarantee a proper homogenization of the ore through a well-planned blending and homogenization pile system from which the ore is reclaimed at an acceptable grade fluctuation. This study tests geostatistical simulation efficiency in predicting in situ grade variability. The methodology is illustrated using a data-set from a large phosphate mine in central Brazil. Additionally, real data obtained at the mine site during January and February 2007 were used to derive the actual grades of each pile formed during this period. Each pile was formed by a selection of blocks within a dig line and these lines mined along the year 2007 were also made available. Given the real grades, it was possible to reconciliate and validate the results predicted by the proposed methodology. The main outcome of this study is the opportunity to check the geostatistical simulation as a tool to quantify the variability of the homogenization system.

Jan 1, 2009

Grains are subject to contamination by mycotoxins which are metabolic by-products of various fungi. The fungal infestations produce local concentrations of the mycotoxins thousands of times higher than the average. These facts make the sampling of the grain for assessment of the mean mycotoxin levels potentially very difficult. In the context of sampling theory, this morphology of the infestations creates a very high distributional and intrinsic heterogeneity of the grain shipment. The distributions of mycotoxin concentrations in seaborne shipments that exist at loading and the number and intensity of infestations that develop under shipping conditions are unknown. All grain shipments carry spores that may give rise to mycotoxin-producing colonies; moisture and temperature determine the final extent of the problem. This paper develops the value of the sampling constant with respect to intrinsic heterogeneity based on data on observed Ochratoxin A (OTA) concentrations in individual wheat kernels. A useful relationship between the distribution of mycotoxin concentrations on a kernel to kernel basis and the distribution of concentration over subsamples is developed.

Jan 1, 2009

By J. Loubser

The concept of caring is in most cases confused with material needs and not psychological needs. By giving employees a job, most managers think that employees should be grateful and return the favour by being loyal, productive and working safely. Other managers hold the view that employees can be lucky to have a job. To show and demonstrate that management are caring for the safety of the workforce requires involvement, dedication and commitment. Obtaining the trust and respect of the workforce should be the main thrust of any organization because within trust and respect lie the secret of optimal safety performance. In the last 70 years, all the fatalities and serious injuries that occurred in the mining industry can be traced back to one thing, non-caring. The same safety non-compliances are still observed, reported and planned against as 70 years ago, and strange as it may sound, the same injuries occur the same way. The question could be asked: Does the mining industry need more risk assessments? More codes of conduct? More engineering. Or does the mining industry need more caring?

Jan 1, 2010

By J. Björkvall, S. Ångström, L. Kallin

In this paper results from industrial trials of CaC2 injection during stainless steel production in an electric arc furnace at Sandvik Steel is presented. The main purpose of the investigation was to analyse the effect of the injection on slag foaming and final chromium oxide concentration in slag. The results show that both an increase in slag foaming and a decrease of the final chromium oxide could be obtained during the charges with CaC2injection. On the basis of the results, the economical requirements are also discussed. Both the technical and economical requirements could be achieved for steels alloyed with Mo. In order to secure the economical requirements for all steel grades of interest, the injection technology must be further developed. It would also be important to utilize the positive effect of the slag foaming on the electric energy consumption. The work has been performed as a part of MEFOS frame research programme with participants from Sandvik Steel, AKZO Nobel and Avesta Polarit. Keywords: stainless steel, EAF, slag foaming, injection, CaC2

Jan 1, 2004

In mid-1984, SAIMM reached an agreement with the South African Region of what is now the Institute of Metals to combine the physical-metallurgical activities of the two organizations. This was the outcome of several years of informal collaboration, and followed the recognition in 1982 by the SAIMM Council that applied physical metallurgy had grown in importance to South African industry and should have a place alongside the two areas already well-established for SAIMM commitment and support-mining and extractive metallurgy.

Jan 1, 1986

By A. C. Lawrence, K. F. Mauer

Human factors in stope productivity -a field experiment by K. F. MAUER, M.A. (Visitor), and A. C. LAWRENCE, B.Econ., D.Com. (Member) An experiment in which three human variables were manipulated in eight stopes was conducted in a gold mine over a period of roughly six months. The three variables, which each had two levels, concerned the degree of movement from gangs, the quality of the Bantu production supervisors, and the extent to which gangs were composed of a single ethnic group (Malawians). Time was included as a variable with three levels in the analysis of the findings. On the average, stable gangs produced 12 per cent more than gangs with a high percentage of transfers, gangs with better production supervisors were more successful by nearly 9 per cent than those with poorer production supervisors, and homogeneous gangs were more productive than heterogeneous ones by as much as 15 per cent. In addition, it was found that a number of the variables exercised a joint influence on stope productivity and that the effects of the variables were accentuated by the len gth of time they had been in operation. V

Jan 10, 1973

By A. J. Jager, G. R. Adams

The pattern of mining-induced fractures ahead of stope faces in deep-level gold mines, as revealed by petroscopic observations, is described. It is shown that there are zones of fractured and unfractured rock ahead of the face, which are about I m wide and continue as discrete entities for at least 12 m parallel to the face and at least 5 m vertically. These zones do not form continuously as mining progresses, but develop from time to time, leaving a solid zone between the fractured zones. The maximum depth of fracturing ahead of the face depends on the rate of energy release.

Jan 1, 1980

By D. A. J. Ross-Watt

Right now the South African mining industry is a high-profile, vital contributor to the nation just as it has been for the past one hundred and twenty-six years since the discovery of diamonds-perhaps even further back if the mining of copper, iron ore, tin, and other minerals in earlier centuries is included. The media in 1995, as has been the case over the years, bear testimony to the complex interactions between the industry and its stakeholders: shareholders, government, employees and their unions, training and educational institutions, researchers, markets, the public, and suppliers of goods, services, and infrastructure. The pressures and challenges that the industry continues to face can be summarized as safety and health, competitiveness, and social and environmental responsibility. There are no surprises here. The motivation for the industry to perform well in these areas is clear; the focus I intend to bring is on the most important tool required for success-that of good mining engineering. This Address sets out - to review the mining aspects that have been discussed in South Africa during the first five years of the decade, a discussion that shows the return of the country as an important mining forum, confirms the role of professional institutes and associations in the development of mining engineering, and brings current relevant issues into focus - to highlight the vital role of mining engineering in the industry, and to identify priorities for the remainder of the decade - to provide the prospective mining engineer, the mining-engineering student and trainee, and the practising mining engineer and mine manager with a better appreciation of the mining-engineering discipline. institutes and ssociations

Jan 1, 1995