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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 P. Kind

Design criteria and recent developments in large-capacity Wemco flotation cells by P. KIND, Ph.D. (Clausthal), B.Sc. (Visitor) The scaling-up of the large flotation cells that have been developed during the past few years has been based on hydrodynamic considerations and has resulted in a 500 ft3 cell unit. Plant results on a porphyry copper ore show that the 500 ft3 unit is equivalent to the previously used 300 ft3 model.. . Plant tests on the use of 300 ft3 flotation cells for the recovery of phosphate, particularly from the coarse size fractions, are also described.

Jan 3, 1976

By J. H. Bulloch

This paper describes detailed fractographic analyses of several specimens that had undergone corrosion-fatigue tests at high stress ratios in simulated pressurized water-reactor environments. The distribution and morphology of non-metallic manganese sulphide inclusions are shown to strongly affect the growth of environmentally assisted cracks (EAC), and certain features suggest that a hydrogen-assisted mechanism is responsible for the observed EAC growth. The incidence of transient EAC growth in isolated regions suggests that the critical conditions that trigger this type of growth are the 'right' local chemistry at the crack tips and imposed mechanical conditions.

Jan 1, 1987

With the increased variability of today's large-scale mining operations, consistent flotation performance is important to improving and sustaining overall recovery through the circuit. The Newcrest Telfer Mine has implemented advanced process control technology to obtain stable level operation and consistent mass pull in the copper rougher and scavenger flotation circuits. The final result has been an overall reduction in variability, which impacts on both copper and gold recovery. This paper describes the methodology and implementation of the improvements in control at the Newcrest Telfer Mine as being an essential part of the business for minerals processing.

Jan 1, 2007

By M. Keevy, K. Hackney

Centrifugal slurry pump station and deposition sites are a common feature of many mines and mineral processing plants. Yanacocha Mine has completed the design of a pump station consisting of two trains of four pumps each. A number of trade-off studies was conducted to optimize the pump station design. The most significant of these was determining the drive types for the slurry pumps. The pump station duty can vary considerably due to the number of deposition points round the disposal site. The standard solution to this problem on a multi-stage pump train is to install one pump with a variable speed drive to control the pump station output by varying the speed of this pump and stopping and starting other stages. However, there are a number of negative impacts associated with this approach. These include head losses through pumps that are stationary or ?wind-milling?, different wear life on pumps that are running and pumps that are stationary, and slower response to the control system with the possibility of hunting. The use of variable speed drives on all the pumps was considered as an alternative to the standard solution. The factors considered in comparing these options were the control and operational differences, the pump efficiencies and absorbed power, the expected pump wear life, the impact on pump maintenance and the cost of the drive options. For this project the option of using all variable speed drives was selected. The paper presents the following aspects of the study: ?Description of the various options investigated. This includes a discussion on the required duty and the drive options. ?Technical comparison between the options. ?Description of the factors influencing pump performance and life.

Jan 1, 2007

By M. D. G. Salamon

In view of an urgent need for a simple means of simulating the behaviour of stratified rock masses, a long-dormant linear model is revived, generalized, and discussed in some depth. The model is piecewise homogeneous, consisting of a pile of homogeneous isotropic laminae in which the interfaces between beds are parallel and free of shear stresses and cohesion. The continuity of stresses and normal displacements is assured across the bedding planes and, to maintain simplicity, the theory of thin plates is used as the kernel of the model. The paper covers the case where the rock mass consists of discrete beds in which the layers are arranged either heterogeneously or systematically. The stratification is regarded as uniform when all the layers are of the same thickness and their Young's modulus changes exponentially with depth; and as homogeneous when all the laminae have identical thickness and properties. The case of uniform stratification is also treated on the basis of an equivalent quasi-continuum derived from the basic model. Attention is focused on the derivation of influence functions. It is demonstrated that the quasi-continuous models, when they are available, can replace their distinct-layer counterparts. The homogeneous quasi-continuum, which permits the derivation of its influence functions in closed form, facilitates the determination of the roof and floor convergence. In the case of a significant class of problems, the convergence distribution is defined by a second-order differential equation in the xy plane, which simplifies to a Poisson's equation if the mining excavations are unsupported. With this result, the paper prepares for the solution of a host of practical problems. These solutions are presented in a series of papers that are in the course of publication.

Jan 1, 1991

By N. A. Barcza

An investigation was conducted into the reactions between the slag system MnO-CaO-MgO-SiO2(AI2O3) and the alloy system Mn-Fe-Si-(C). Synthetic slags representative of plant melts and a plant alloy were reacted in alumina crucibles at temperatures of 1400°C, 1450°C, 1550°C, and 1600°C. In similar experiments, slags were used that comprised a South African manganese ore with various amounts of lime and several synthetic alloys with various silicon contents and manganese-to-iron ratios. These experiments were conducted in a vertical molybdenum-wound resistance furnace with full temperature control. Slag-to-alloy ratios were also varied during the tests. The rate of reduction of Mn.O3 and the MnO from the slag by the silicon in the alloy was extremely rapid, most of the reaction being completed within five minutes. The strongly exothermic nature of the reaction resulted in considerable generation of heat at the slag-alloy interface, causing convectional stirring of the contents of the crucible and promoting the rate of reaction. Equilibrium was usually attained after fifteen minutes. The major limitation governing the recovery of manganese is the need for the silicon content of the alloy to meet a maximum specification of 2 per cent. Higher concentrations of silicon in the final alloy of between 8 and 12 per cent favour good recoveries of manganese from the slag, but, since such an alloy is not salable, lower recoveries must apparently be tolerated. In alloys of 2 per cent silicon, low activities of the silicon are responsible for poor recoveries of manganese. The activity of MnO in the slag can be increased by moderate additions of CaO and small amounts of MgO, i.e., by an increase in the basicity of the slag.

Jan 1, 1979

By More-O&apos, R. C. Ferrall, J. W. Wilson

SYNOPSIS The theory of elasticity has been shown to provide a means of determining the stresses and displacements induced by mining in deep level hard rock mines. This theory has been incorporated into an electrical resistance analogue on which the plane of a reef or ore-body can be modelled to enable the rapid determination of stresses and displacements at points in the plane of the reef. This electrical analogue has been used to determine energy release rates caused by scattered mining, which, to some extent, is a measure of the degree of hangingwall fracture. A correlation between predicted energy release rates and actual underground conditions in stopes in the O.F.S. goldfields has been encouraging enough to define parameters on which future stoping layouts can be based. The use of the elastic theory through the analogue has been extended to the assessment of the influence of stoping operations on off-reef excavations. Underground conditions at damaged and undamaged areas have been compared with predicted elastic stresses at the positions under review, resulting in the derivation of design parameters for use in siting off-reef excavations in the prevailing geological conditions in the O.F.S. and Klerksdorp goldfields. The analogue has also been used to assess the vulnerability of certain un mined dykes to bursting. Correlations between stresses induced on dykes by stoping and dyke behaviour underground has enabled critical stress levels to be determined for several persistent dykes occurring in the O.F.S. and Klerksdorp goldfields. A number of long and short term planning projects at mines operating in the Anglo American Corporation and General Mining and Finance Groups are described, where the data derived from the electrical resistance analogue is processed by computer programmes and assessed on the strength of the design factors derived from the correlation of field work and the elastic theory.

Jan 1, 1970

By M. U. Ozbay

This paper presents an overview of the research that has been carried out to improve the understanding of the fracture processes occurring in rock under high levels of stress. The onset and growth of fractures are studied by means of laboratory model testing, and the results obtained are used in the calibration and validation of the numerical model DIGS, which is based on displacement discontinuity. The results obtained so far have shown that, while there are overall similarities between the experimental results and the numerical simulations, improvements to the experimental procedures and the DIGS are required for a detailed mechanistic understanding of shear-band orientations and extension fractures.

Jan 1, 1996

By A. R. Barnes, C. W. P. Finn

The prereduction and smelting characteristics of UG-2 ore were studied and compared with those of Winterveld chromite ore. The UG-2 ore proved more reducible, and substantial prereduction (over 70 per cent reduction after 30 minutes at 1250oC) was obtained. No difficulty was experienced in the production oh high-carbon ferrochromium alloy containing 48 to 50 per cent chromium. Calculations of the energy balance show that UG-2 chromite has lower total energy requirements (both on the basis of unit of ferrochromium produced and of total chromium content). More than 50 per cent of the energy required for reduction can be supplied outside the smelting furnace.

Jan 1, 1983

By R. R. Mankowski

The work described here is an extension of current theory applied to obtaining the power dissipated at the wavefront of a transverse disturbance traveling along a mine hoisting cable. A previously derived empirical relation is adapted to the present problem, and is solved by use of a Lagrange-type reference frame moving with the wavefront. As a result of tie limitations inherent in the original relation, only a lower-bound for the domain of predicted power losses is defined. A qualitative assessment of conditions leading to the undesirable effects of internal frictional losses at the wavefronts are discussed in terms of the operating environment found on typical mining installations

Jan 1, 1990

By A. P. W. Briggs

Difficulties with the screening of large volumes of pulp to remove plus 600 /km material before the adsorption circuit and to retain plus 20-mesh carbon in the adsorption contactors have largely been solved, with the result that the plant can now handle its design throughput. The elution and electrowinning processes have been modified to simplify the circuit, but the regeneration of carbon remains unsatisfactory. The production of fine carbon in the plant can lead to increased gold losses, and this carbon must be collected and treated. Collection methods for fine carbon and some indications of the quantity of the carbon and its gold values are given.

Jan 1, 1983

By J. P. McDonald, P. L. Mattison, J. M. W. Mackenzie

A variety of processing problems in the hydrometallurgical extraction of uranium in the U.S.A. are contrasted with those in South Africa. In U.S. plants, for example, problems are often encountered in the separation of vanadium, molybdenum, and uranium, and in the contamination of the circuit with organic acids. South African plants often experience problems with dissolved silica in the feed, clarification of feeds, and problems associated with synthetic polyelectrolytes. Individual situations are examined, along with the analytical techniques that assist in solving specific problems. Successful approaches that have been applied to mechanical and chemical problems in' uranium solvent-extraction plants are discussed.

Jan 1, 1981

By I. V. Samarasekera, E. B. Hawbolt

A review of recent work being conducted at the university of British Columbia on the modeling of the microstructural evolution during the hot rolling of steel is presented. A mathematical model of heat transfer was developed to describe the thermal field in a slab during rough and finish rolling. The model for rough rolling, discussed in this review, also simulates the growth of oxide scale on the slab surface. To quantify the heat transferred from the slab to the work rolls, instrumented samples of MSI3O4 L stainless steel, 0,05 per cent carbon steel, and 0,05 per cent carbon steel with 0,025 per cent

Jan 1, 1995

By H. Jeram

The ilmenite, rutile and zircon processes of the mineral separation plant generate tailing streams, which still contain valuable mineral. This is due to a combination of factors, which include separator equipment efficiency, particle size effects and inefficient operating practices (equipment overloading, blockage, etc.). Recent developments by metallurgical equipment suppliers have led to increased mineral separator performance enabling recovery of previously lost valuable mineral. Mineralogical studies were conducted using QEM*SEM and MLA techniques to identify and quantify gangue mineral species and determine mineral association. Laboratory and pilot-scale test work was then conducted to develop suitable process flowsheets for the recovery of ilmenite, rutile and zircon from current and stockpiled tailings.

Jan 1, 2007

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 J. H. Viljoen, A. Heyns, J. F. Morrison, C. H. Wyndham, N. B. Strydom

Discussion M. J. Martinson* (Associate Member): This is another interesting paper in the series which the Human Sciences Laboratory is publishing on the physiological cost of the more strenuous manual tasks performed underground. As a mining engineer-albeit presently an academic one -this contributor is more concerned with the practical significance of the study in the field of stope cleaning than with physiological niceties, but before discussing some of the practical issues raised by the paper perhaps the authors would care to reply to lay comment on three physiological matters. Firstly, in two places the authors make statements to the effect that the maximum oxygen intake of 'average' (sic) Bantu mine workers is 3.0 l/min. What do the authors mean by 'average'? Maximum oxygen intake in the individual is probably some function of inter alia age, physical fitness, state of health, ambient partial pressure of oxygen, diurnal and/or seasonal changes in metabolism, and possibly cumulative exposure to dust and other occupational contaminants. Since maximum oxygen intake is apparently such an important quality in manual labourers we ought to have a clear picture of its distribution in the entire labour force, and also know precisely how the individual's quantum is affected by factors such as those mentioned above. Secondly, arising out of the same statements and ignoring the reservation implicit in the previous paragraph, is it correct to say that the 'average' Bantu mine worker has a maximum intake of 3.0 l/min? In the August 1966 issue of the South African Journal of Science four of the present co-authors reported the mean maximum oxygen intake of a random sample of 338 Bantu recruits of different tribes to be 2.63 l/min with a standard deviation of 0.542 l/min, and these figures were repeated in a paper published in the November 1968 issue of this Journal. Admittedly the mean maximum oxygen intake of the six subjects used in the present study was 3.05 l/min, but since they were selected on the grounds of previous shovelling experience they can hardly be regarded as being 'average' recruits. Thirdly, it seems to me that the authors are perhaps a little uncritical in their acceptance of the '50 per cent of maximum oxygen intake' level of activity for endurance work. I am not unmindful of the evidence upon which this level is based, but I suggest that the evidence is at best tenuous and that the whole topic of fatigue and 'optimum' levels of productivity under conditions of high muscular activity and considerable psychological stress is a lot more complicated than would appear from the authors' ready acceptance of the 50 per cent level. Under present working conditions the question is largely rhetorical because it would need an army of supervisors to ensure that all members of a typical gang work at 'optimum' levels throughout the shift, but if individual performance should ever become more readily determinable the issue might become crucial to management and malayisha alike. So much for physiological matters; now a few random thoughts on some wider, practical issues raised by the paper. In the paragraph headed Material the statement is made that 'The mixture (of fine, medium-sized and bigger rocks) was considered to be representative of an average underground rock sample'. Elsewhere in the report the authors specifically draw attention to the effect of particle size on the oxygen consumption of men shovelling graded material, and intuitively one imagines that the size distribution of the material being shovelled would be highly significant in a study such as this. Presumably the authors were forced to assess size distribution subjectively because of the lack of objective data on the subject, and possibly the necessity for this assumption highlights how little we know quantitatively about any of the variables in stope cleaning systems. In this connection it may be remarked that although the present study was largely designed to show how dip and stoping width effect energy expenditure in shovelling, no data are given-nor, probably, are they available-to show how the industry's stoping tonnage is distributed in terms of these two factors. It seems to me that if the mining industry seriously hopes to improve stope productivity it must start by measuring the basic variables in existing systems. Elaborating somewhat on the previous paragraph, there also seems to be a tremendous gap between the present study-and its predecessors-and the prospect of gainfully using the information so carefully garnered by the authors. It would be reassuring to hear from the authors that their work on the physiological aspects is being integrated in some master plan for increasing productivity of manual labour. This I fear is not the case, and if productivity has changed at all in recent years I would hazard a guess that the change has been brought about by random factors rather than by systematic engineering design. The Human Sciences Laboratory has worked extensively in stopes in the past, and possibly the time has come when it should widen the ambit of its operations to include engineering-type analyses of cleaning systems, with particular emphasis on the economics of rapid cleaning by manual labour. Perhaps experiments could be conducted with stakhanovite-type gangs consisting of men selected for their high maximum oxygen intake and superior motivation; these men might be offered special incentives in the shape of extra pay

Jan 10, 1969

By R. J. E. Stewart

Another very successful evening meeting was organized by the Johannesburg Branch of The South African Institute of Mining and Metallurgy on 20th November, 1990, when Mr R.D. MacPherson, General Manager of Richards Bay Minerals, gave a presentation on the Richards Bay operations. The function was held in the Ballroom of the Johannesburg Country Club, and the very high attendance (some 250 people) was indeed a reflection of the high profile of the subject mater. It was also a fitting reward for the efforts of Mr MacPherson and his team, who spent a considerable amount of time and effort traveling the country to present 'the other side of the story'.

Jan 1, 1991

By S. L. Crouch

A. C. Dieringt The procedure described by Professor Crouch for the modelling of mining in faulted ground allows the elastic and inelastic deformation to occur simultaneously, that is, fault slip occurs while an element is being mined. The energy release rates (ERR) shown in Crouch's Fig. 10 are apparently calculated from his equation 9 using the i total deformation Din (see the upper load line of Fig. I) Refractories The institute of 'Gesteinsh iittenkunde' of the technical university at Aachen, the Refractories Research Institute at Bonn, and the Verein Deutscher Eisenshiittenleute (VDEh) at Diisseldorf are to hold the XXII International Refractory Colloquium on 27th and 28th September, 1979, at Aachen.

Jan 1, 1979

By F. W. Petersen

For the past thirteen years, the Universities of Cape Town and Stellenbosch have hosted an annual symposium to discuss topics relevant to mineral processing. Since 1987, this Symposium has been held under the auspices of the Western Cape Branch of the South African Institute of Mining and Metallurgy, and has become one of the main events on the national conference calendar. In 1989 and 1993, the symposia took the shape of international conferences. This year the 13th Annual Mineral Processing Symposium was organized by the two universities, the Cape Technikon, and the local branch of the South African Institute of Mining and Metallurgy, and was held at the Van Riebeeck Hotel in Gordon's Bay.

Jan 1, 1994