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By P. Marinos, G. Tsiambaos, H. Saroglou

The anisotropic behaviour of “Athens Schist” has been brought out through the testing of specimens with varying orientation of schistosity with respect to the major principal stress under uniaxial, triaxial and dynamic conditions. A large number of results from tests on intact rock specimens of the “Athens Schist” were statistically analysed and evaluated. Le comportement anisotropique des roches du système “Schistes d’ Athènes” a été déterminé sur des épreuves avec une orientation différente de la schistosité par rapport à l’axe de chargement sous des conditions axiales, triaxiales et dynamiques. Un grand nombre des résultats a été statistiquement analysé et discuté. Zur Bestimmung der anisotropen Eigenschaften der Athen Schiefer wurden einaxialen, dreiaxialen und dynamischen Kompressionsversuchen an Gesteinskernen durchgeführt, bei denen die Belastungsachse verschiedenen Neigungen gegen die Schieferung hat. Die Messreihen an anisotropen unzerreissbaren Fels Samplen von Athen Schiefer wurden statistisch analysiert.

Jan 1, 2003

By Y. R. Murthy, P. K. Satija, A. Srinivasulu, S. K. Tripathy, A. Ranjan

"In this investigation, we optimize the grinding circuit of a typical chromite beneficiation plant in India. The run-of-mine ore is reduced to a particle size of less than 1 mm in the comminution circuit and concentrated using gravity separation. The comminution circuit comprises two-stage crushing and single-stage grinding in a ball mill in closed-circuit with a highfrequency screen. A detailed circuit audit was undertaken at the plant to understand and evaluate the performance of the grinding circuit. The audit revealed abnormalities in the process and design parameters which caused high energy consumption, lower throughput, and loss of ultrafine chromite. Laboratory studies indicated the differences in the grinding properties (work index, breakage rate, etc.) and liberation sizes of these ores. Studies also revealed that grinding media size, particle retention time, and pulp density are crucial in coarse grinding. Based on the laboratory grinding and characterization studies; simulation studies were performed to optimize the operating parameters of the grinding circuit.IntroductionComminution is a critical process in mineral processing which strongly influences the economics of production. In mineral processing, particles containing valuable minerals must be disintegrated at a sufficiently fine size to liberate valuable minerals from waste constituents, so that they can be easily separated by an appropriate beneficiation method. The Sukinda chrome ore beneficiation plant utilizes different types of run-of-mine (ROM) ore with different physical properties (viz. grindability characteristics, work index, mineral composition, liberation, chemical composition, etc. for the production of chrome concentrate. In the feed preparation circuit, the ROM ore is crushed and ground to below 1 mm. Grinding in the chromite beneficiation plant is a critical unit operation to achieve the desired product size of below 1 mm and to control the generation of the ultrafine particles. Furthermore, about 40% of total power consumption in the beneficiation plant is accounted for by the grinding of the ore. This implies that any improvement of the circuit performance will lead to an overall increase in productivity."

Jan 1, 2017

By R. P. King

The ideas leading to the formulation and utilization of a flotation model are developed. The main theoretical and experimental work that has been carried out by the National Institute for Metallurgy Research Group at the University of Natal is presented. The two experimental flotation plants available to this Group are described.

By M. J. Nicol

The results are reported of experiments on the influence of a number of variables on the rate of loading of gold cyanide onto activated carbon and the equilibrium capacity of the carbon. These variables include the concentrations of gold and free cyanide in solution, the pH value and ionic strength of the solution, the concentration of organic compounds in the solution, the temperature, the particle size of the carbon, and the mixing efficiency. The experiments were carried out under approximately steady-state conditions to simulate the conditions in a countercurrent carbon-in-pulp absorption plant. In addition, the results are reported of experiments to establish whether the absorption of gold cyanide onto activated carbon is a reversible process.

Jan 1, 1983

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

By Franz E. Pawlek

Synopsis This is a summary of investigations in the field of pressure leaching carried out at the Institute for Extractive Metallurgy of the Technical University of Berlin-West during the last seven years. The efficient dispersion of gas in a liquid and its dissolutions as well as the events at the phase boundary when leaching ZnS are reported. At the end two examples are given for the use of pressure leaching in the processing of smelter by-products. INTRODUCTION About 20 years ago, experiments were independently started in Canada and in Berlin on the subject of dissolving sulfidic ores without preliminary treatment by means of leaching under increased oxygen pressure. In Canada ammoniacal solutions were mainly employed, and F. A. Forward and his co-workers were successful in applying this process on a large industrial scale1, 2. This process is used in Fort Saskatchewan to produce about 15,000 tons of Ni per year. In Berlin, investigations were started on leaching with acid solutions3, 4. This process had also been used on a large industrial scale in the D.S.A., but the choice of unfavourable working conditions led to great difficulties, and to giving up this process for industrial use. Later on in Berlin work was carried out especially on the kinetics of pressure leaching 5, 6, 7, 8, 9 and its applications to the processing of smelter by-products, in particular of mattes and speisses10, 11, 12, 13, 14. The dissolution of ores and by-products can be subdivided into four steps: 1. the efficient dispersion of the gas, so that its dissolution occurs over as great a surface area as possible, since only the dissolved oxygen reacts with the solid, 2. the suspension of the solid, so that the entire surface can take part in the reaction, 3. the phase boundary reaction, 4. the removal of the reaction products. The first two steps belong to the field of process engineering and will be discussed from this point of view. The aim of these experiments15 was to find out first of all the limits of efficiency of self-sucking stirrers in solutions of low viscosity with regard to the mass transfer. In addition, the effect of ultrasonics in the same reaction system was studied. The experiments were carried out in a lucite container as shown in Fig. 1. Four baffles of 0.1 d width were in the stirring vessel. The height of these baffles was adjustable. For every experiment one litre of liquid was used. An infinitely variable direct current motor, which was fixed with a hollow shaft, served as the driving power for the stirrer.

By K. Richardson

Although the De Beers group has a long history of placer mining on land, the group only became actively involved in deep water marine diamond exploration and mining in1983 with the formation of De Beers Marine. Full-scale commercial mining commenced around 1991. Since then, the group marine mining capability has grown into a formidable fleet of 8 large deep water (>70 m) mining vessels, as well as other special purpose geo-survey platforms. Marine diamond production by the group is expected to be just short of 1 million carats in 2006. DeBeers operates across the entire value-chain spectrum from geology and geo-survey, through sampling to mining, and finally ore processing into high value concentrate. Supporting these operations involves significant service activities such as maintenance, security, logistics and environmental management. Specific challenges exist in terms of developing or acquiring appropriate technology for marine mining. These challenges have resulted in DeBeers operating extensive in-house R&D and projects departments, as well as drawing extensively from technology partners. An array of computational and test facilities are also available to support R&D and projects activities. Hydro transport in various guises is key to the current approaches to marine mining and ore processing. Use is made of airlift and centrifugal pumping for hydraulic hoisting of very coarse gravel, while splitters, launders, dewatering, elutriators, jet-pumps, centrifugal pumps, dense medium circuits, pipeline systems, and instrumentation for coarse abrasive particles are used extensively in the ore processing plant.

Jan 1, 2007

"Chairman: Dr DeV. HarrisRapporteur: Mr A.H. MunroPapers:Corporate exploration strategies by MacKenzie, B.W.The Engel Simulator and the search for uranium by Griffiths, J.C. and Singer, D.A.The Chairman opened the session by tracing the changes which have taken place in the exploration field since the days of the lone prospector who relied upon his individual skills and to a large extent on luck. The deposits which now remain to be discovered are better covered and are of lower grade. A much greater team effort, involving geoscientists and engineers, is required. The gamble is thus much greater -not only are the probabilities of failure still significant but the consequences are more severe. A recent Canadian survey indicated that expenditures of between two and nine million dollars on regional exploration programs are required to locate one significant deposit.The Chairman went on to say that these facts have led companies to regard exploration as another form of investment and to treat it accordingly. This had placed exploration in the context of corporate strategics and structures, which was the subject of the first paper of the session.In introducing his paper, Dr B. W. MacKenzie said that the paper suggested a decision framework for exploration planning. Initially the environment is analyzed to define observable and relevant economic characteristics. The terms of reference for exploration planning and the appropriate allocation of capital and skills are then established in the light of corporate objectives and growth alternatives. With the aid of this information and in the light of profit and corporate risk criteria, exploration strategies can be selected.Dr MacKenzie went on to say that the usefulness of the concept and criteria outlined in his paper depended critically upon three characteristics of any particular economic environment, namely, the return resulting from an economic discovery, the unit discovery Cost and the probability of making an economic discovery. He then showed by means of a case history relative to the Canadian Shield and Cordilleran areas that these three characteristics could, in fact, be evaluated for regions with reasonable histories of mineral activity.The first contributor to the discussion of the paper, Mr Alfred Weiss, mentioned that his group had been involved in exploration modelling for some ten years and were thus particularly interested in the paper. He went on to say that they had experienced greatest difficulty with reconnaissance programs and that he sensed that these difficulties were also present with the methodology which had been outlined. Mr Weiss asked Dr MacKenzie how he would deal with such situations when no information was available but where there was the potential for both exploration and discovery. Dr Mackenzie agreed that the lack of information was a very severe limitation and said that at the present time his methodology probably did not provide a basis for breaking down the broad geological regions he considered into areas for further assessment."

Jan 1, 2014

By D. Farrow

Future development of kimberlite mines is now focused on mining at deeper levels. The consequences are increased difficulty and costs of the mining operations. The decisions on investments require accurate resource evaluation and quantification of the risk. In the decision process the first step consists in choosing the number of boreholes sampling the pipe relative to the level of uncertainty that can be accepted. The uncertainty in the volumes of rocks of different types can be assessed as soon as we can estimate these volumes from a given borehole layout and calculate the error by means of its variance for instance. In theory this can be achieved by using geostatistical techniques (‘transitive theory’), but in practice the calculation of the error on volumes can be achieved in very particular cases, assuming some regular sampling patterns. A different approach has been chosen based on simulations, giving maximum flexibility to reproduce the reality of the sampling procedure. The idea is to simulate the geometry of several ‘possible’ pipes with their internal geology and estimate them by kriging. Several experimental errors are obtained on which risk analysis can be performed. The aim is to find a feasible method to perform the simulations with reasonable chance to correctly represent the reality, without data on the pipe extension. The methodology applied is based on some hypotheses that can be assessed by the geologist as well as by the geostatistician. The procedure assumes a geological model based on current knowledge including appropriate geostatistical variation. What make these simulations specific and powerful in this case comes from the fact that the boundaries between the different rock-types can be simulated using a transformation of the real 3D space into a 2D space defined by means of polar coordinates. Ultimate transformations to account for smoother variations with morphological transformations allow the generation of realistic pipe geometries on which sampling pattern can be used to evaluate the estimation errors. By estimating the simulated pipe geometries with different boreholes layouts a risk curve expressing the uncertainty in the volumes of the different rock-types versus the number of holes can be developed.

Jan 1, 2003

1. Book reviews Mining and metallurgical practices in Australasia. Melbourne, Australian Institute of Mining and Metallurgy, 1981. $40 (incl. surface postage). Reviewer: M. G. Atmore Coal mine ground control, by Syd. S. Peng. 1978. Reviewer: C. F. Engelbrecht Sixth Annual International Conference on Coal Gasification, Liquefaction and Conversion to Electricity, July 31 -August 2, 1979. Pittsburgh, School of Engineering of the University of Pittsburgh, 1980. Reviewer: S. T. J. van Rensburg This book is a useful general reference volume on the topics covered provided a great deal of technical detail is not required from it. It consists of 29 papers, which are arranged under 6 headings. Flotation agents and processes. Technology and applications, edited by M. W. Ranney. Park Ridge, D.S.A., 1980. $48. Reviewer: R. P. King 2. New books Project control manual, by Sven R. Red. 250 pp. in loose-leaf binder. U.S. Al47. (Obtainable from the author at Bray Studios, Windsor Road, Windsor SL45 UG, England.) Manganese deposits, by Supriya Roy. London, Academic Press, 1981. 400 pp. Joint preparation for welding (set of overhead-projector transparencies). Abington (England), The Welding Institute, 1980. £34 per set. Electron micrographs of clay minerals, by T. Sudo,S. Shimoda, R. Yotsumoto, and S. Aita. Amsterdam, Elsevier, 1980. 228 pp. Dfl.150. Weld pool chemistry and metallurgy. Abington (England), The Welding Institute, 1980. 357 pp. $27. 3. New journal ...being known as Gliickauf + Translation, at an annual subscription of 396 DM for 24 issues per year. It is available from Verlag Gliickauf GmbR, D-4300 Essen I, P.O. Box 103945, Federal Republic of Germany. 4. Canadian MRI publications During 1980 the Mineral Policy Sector introduced a new series of reports identified by the prefix MRI. These cover internal studies and analytical works on a wide variety of subjects, that for one reason or another, do not reach the publication stream of the regular series yet may be of interest to readers in this 'unpublished form'. Twenty-four such titles are listed below. Exploration planning A series of professional advancement seminars for the mineral industry is to be held at Rhodes University from 12th to 20th August, 1981. The series, entitled 'Economic Guidelines for Exploration Planning', will be conducted by Professor B. W. Mackenzie, and the attendance will be limited to 30 participants. The seminars are intended Seminar on Geostatistics A seminar for mining executives on Geostatistics and Decision Making in the Mining Industry is to be held in Toronto from 23rd to 25th September, 1981. v

Jan 1, 1981

By A. W. S. Schumann

G. H. HENDERSON INTRODUCTION It is a pleasure to have read Mr Schuman's wide ranging and highly informative paper and also to congratulate him. Before proceeding to give views on the use and preservation of coal in South Africa, it is perhaps apposite to look at the South African scene on the world canvas. Mr Schuman's figures in his Table I are highly revealing. The Table shows expected consumption, export and import demand in the year 1980 by the continents of the world. The Republic of South Africa is shown as one of only four exporting countries at that date, although in the interim, Australia has become an exporter and will continue to grow as an exporter of coal. Huge fields have been proved in recent years. There is reason to think that for some years, coal and its economical uses have been under-estimated. The importation of oil carries a constant question mark and the exciting possibilities expressed in the uses of Dranium a decade ago for power generation, appear to have met with some setback. Present indications are that breederreactors will be delayed until about 1990. The capital cost of such reactors, too, is enormous. By 1980 it has been estimated that 20 per cent of the energy required by the leading ten nations of the world will come from nuclear power, but 80 per cent would then remain for fossil fuels and hydro generation. COAL DEMAND AND USAGE It is of interest to record that coal production in all the countries of Europe has declined markedly in the last 25 years. This is due to competition from oil, gas and nuclear power and also for sociological reasons; but there are signs that efforts will be made to resuscitate, at least in some measure, the mining of coking coals for which there is a strong and growing demand. Possibly all hard coal now mined in Germany has coking properties and that country is self-sufficient in this commodity. Germany might perhaps consider selling coking coal to her neighbours and importing additional coal for power-raising purposes. It has been frequently stated in American publications that the coal reserves of the D.S.A. are sufficient for 1 000 years. What that means, I do not know, but it is at least an indication that America has huge reserves of coal. Domestic and export demand in the U.S.A. in 1968 exceeded production for the first time. In 1969, the United States' output amounted to some 556 million tons, an increase of less than 2 per cent on the previous year. The output achieved fell short of demand, domestic and export, by more than 7 000 000 tons. This has caused and is continuing to cause anxiety in the U.S.A. In many countries young men for a number of reasons, largely environmental and social, are not coming forward in sufficient numbers for mining requirements and the same pattern has revealed itself in the Republic. This is, indeed, alarming because mining men in large numbers will be required to meet the estimated tonnage requirements set out in the following Table: It is difficult to visualise the replacement of these coal requirements either by oil or by nuclear fuels. The coal must be mined and men are required for the purpose. Unless a greater section of the population is allowed to participate in the more responsible aspects of mining, there is a serious likelihood that demand will not be matched by output. In addition to local demand, a lively export trade is possible. Exports are dependent on the future capacity of the South African Railways and Harbours and on Government policy. An export figure of 10000000 tons per year during the decade can be visualised and this figure would raise total estimated sales production to a figure of over 100 000 000 tons in 1980. At this point, it is necessary to examine the desirability or otherwise of exporting coal. How much coal

Jan 11, 1970

By J. Grobler, J. Zietsman

"Understanding the influence of feed material mineral assemblage on spiral separation is paramount for the successful and consistent operation of a spiral plant. Plant stability is required to maintain high recovery of valuable heavy minerals (VHM). Standard material analysis methods used in the heavy mineral industry to evaluate spiral separation behaviour are unable to quantify performance differences in the case of large variations in feed assemblage. This study illustrates a systematic approach to evaluate spiral separation performance. This technique was applied on a four-stage spiral plant. The performance information was used in a circuit simulation to clearly illustrate the importance of correct setting of the spiral splitter position and resulting spiral mass loading to ensure optimal circuit stability and maximum VHM recovery.IntroductionHeavy mineral sands deposits generally consist of naturally fine-grained, free-flowing sand due to the way in which the deposit was formed. The size of the heavy minerals market is roughly 8 Mt/a of zircon and titanium combined (Iluka, 2013). If an average combined feed grade of 5% zircon and titanium and an average combined overall product recovery of 80% are assumed, the resulting run-of-mine feed tons that would require primary spiral beneficiation is 200 Mt/a. The number of spirals required for the processing of this material, assuming 6500 operating hours per annum, an average of 2 t/h per start, and the same number of rougher spirals as other duty spirals, is over 30 000 spirals for the heavy mineral sands business alone. These numbers clearly illustrate the importance of the spiral in the heavy mineral industry.The aim of a spiral plant in the primary processing value chain of a heavy mineral process is to reject non-valuable quartz (a light mineral) from various valuable heavy minerals (VHM). The product from the spiral plant is a heavy mineral concentrate that has a reasonable grade (more than 90% heavy minerals) at a reasonable heavy mineral recovery (greater than 90%). This benchmark is fairly easy to achieve if all the mineral particles are well liberated (as in the case free-flowing sand), the feed is properly deslimed (-45 µm fraction removed to less than 5% of the solids mass), and the spirals are fed within design solids concentration (water to solids ratio) and design spiral load (dry tons per hour per start)."

Jan 1, 2017

By P. C. Seligmann

The theory of firing of electric detonators is developed insofar as it affects the design of blasting circuits. Practical values for the firing conditions suited to detonators of local manufacture are tabulated. The design principles of blasting circuits are outlined. This information can be used by mine management to ensure that electric blasting will be done efficiently and economically.

Jan 1, 1979

By R. P. King

Held on the 22nd March 1972 at Kelvin House. Four papers were presented at this colloquium, which was attended by approximately 120 people. The first paper, 'Flotation Research Work at the N.I.M. research group, University of Natal on the modelling of a Flotation Process' was presented by Dr R. P. King, the leader of the N.I.M. Research Group in the Department of Chemical Engineering at the University of Natal. A discussion panel, under the chairmanship of Dr R. E. Robinson with Mr M. Dawson (PMC), Mr E. Roux (FOSKOR), and Dr B. K. Loveday (NIM), discussed the potential application of the theoretical work on flotation modelling to industrial processes, and alternative approaches to providing a way of control of flotation plants. The second paper, 'Fundamental Studies of the Flotation Process the Work of the National Institute) for Metallurgy', was presented by Dr N. P. Finkelstein. The discussion panel for this paper was under the chairmanship of Professor D. D. Howat,and had as its members Mr H. P. Carlisle (JCI), Professor D. le Roux (University of Pretoria), and Mr E. Rudolph (Anglo American Research Laboratories). A lively discussion on this paper ensued, with several contributions from the floor. After lunch, Mr S. K. de Kok, Assistant Consulting Metallurgist, Anglo Vaal, presented a paper on 'The Flotation of Copper and Zinc Sulphide from Prieska Ore'. The paper was discussed by a panel comprising Dr V. C. Lovell (NIM), Mr A. Gilbert (General Mining), and Dr D. Legge (Anglo Vaal), under the chairmanship of Dr L. Bushell. This discussion, in which many members of the audience participated, revolved around the difficulties associated with the production of copper and zinc concentrates and the lack of fundamental information on the behaviour of copper and zinc sulphides in flotation. The final presentati0n was a paper, 'The Recovery by Flotation of Cassiterite contained in Gravity Concentration Plant Tailings', presented by Mr E. B. Viljoen (Metallurgy Department, Goldfields South Africa Limited). The discussion, led by a panel consisting of Mr O. Tant (Goldfields Laboratories), Mr J. Levin (NIM), and Mr R. I. Shanks (NIM), under the chairmanship of Mr H. Cross (Goldfields South Africa Limited) referred particularly to the use of new reagents for the flotation of tin, with particular emphasis on the fundamental relationship between reagent composition and its ability to float this type of mineral.

Jan 4, 1972

By A. N. Brown

Rock breakage by drilling and blasting is fundamental to every hard-rock mining operation. The subject was an apt choice for a mining school because many technological changes have taken place since the subject was last presented some ten years ago. However, because of the development of surface mining, it was decided that two schools should be held: one for underground mining, and the other for surface mining. The School on Underground Mining was held at the University of the Witwatersrand in February 1986.Copper 87 COPPER 87 is an international conference organized by metallurgical and academic institutions of two of the largest producers of copper in the world, Chile and Canada.

Jan 1, 1986

By C. E. Doran

Since the early 1990s the underground mining industry has embarked on a vigorous program of improving process and eliminating costs. A leading development in this program has been the implementation of leaky feeder radio systems as an enabling infrastructure for future automation. El-Equip Inc. has led this development with more than 175 mines implementing mine-wide radio infrastructures for voice and data. In this paper, we describe the implementation of a digital radio network which supports existing installations through to an automation infrastructure employing full digital cellular communications with mobile video roaming capabilities. We outline the evolutionary path from existing low speed data communications links through to 155 Mbps and beyond.

Sep 1, 2001

The development of 3D multi-parametric models facilitate the provision of resource information well in advance of the mining face. Using the model, one can evaluate mining areas not only for grade and tonnage predictions but also for predictions of rock mass quality. Blast design and milling requirements can be derived from the rock mass quality predictions. This information can be used for overall mine planning and evaluation, costing, production optimization and slope design. This allows the full range of mining activities and costs to be interconnected, there by lowering costs and improving efficiencies through the application of the multi-parametric model. Feasibility studies for new projects require an expected budget expenditure estimate to within5% of actual costs. This level of accuracy is expected by mining companies and investors but cannot be achieved without a sound knowledge of the rock mass variability. By developing a 3Dmulti-parametric model as part of the feasibility study and using the same geological model exploration boreholes, a significantly better understanding of the rock mass conditions can be obtained. This rock mass information can be used for equipment selection, economic pit layouts, processing plant design, underground mining layouts and support requirements, to name but a few design parameters that depend on rock mass conditions. The initiative at Anglo Platinums, Potgietersrust Platinum Ltd.?s (PPRust) operation, has delivered significant results showing improvements across the mine to mill value chain. These include increased loading rates, reduced electricity and crushing consumables, as well as higher plant throughput. The ore reserve model has gained international acceptance as an invaluable tool for a mining operation. Certainly most financial organizations will not invest in a mining project that does not have an ore reserve model. There is the potential for multi-parametric models to be recognized as vital tools in the mining process, as is the case with ore reserve models.

Jan 1, 2006

By L. Lorig

"Two types of extreme event, earthquakes and rainfall, potentially affect open pit slope stability. In the case of earthquakes, there are rather well-developed analysis procedures and acceptability criteria. The analysis procedures relate mainly to selection of the dynamic loading either through design earthquakes and/or pseudo-static seismic coefficients. The acceptance criteria are typically expressed in terms of a minimum safety factor in pseudo-static analyses. The acceptance criteria are often promulgated by governments despite the fact that no open pit slope has ever been adversely affected by an earthquake. This paper explains why open pit slopes are seemingly more resistant to dynamic loads than natural landforms, which can experience catastrophic landslides.Extreme rainfall events are much more likely to cause open pit slope problems than earthquakes. Two types of problem are common – slope erosion and slope instability. Slope erosion is often mitigated by appropriate surface water controls. Slope instability due to elevated transient water pressures is more difficult to mitigate. Analysis procedures and acceptability criteria are rare. This paper will discuss the mechanisms for rainfall-induced slope instability, as well as analysis methods. Examples will be discussed and analysis methods are proposed. IntroductionTwo types of extreme event, earthquakes and rainfall, potentially affect open pit slope stability. In the case of earthquakes, there are rather well-developed analysis procedures and acceptability criteria. The analysis procedures relate mainly to selection of the dynamic loading either through design earthquakes and/or pseudo-static seismic coefficients. The acceptance criteria are typically expressed in terms of a minimum safety factor in pseudostatic analyses. The acceptance criteria are often promulgated by governments (e.g., Peru, Chile) despite the fact that no open pit slope has ever been adversely affected by an earthquake. This paper explains why open pit slopes are seemingly more resistant to dynamic loads than natural landforms, which can experience catastrophic landslides.Extreme rainfall events are much more likely to cause open pit slope problems when compared to earthquakes. Two types of problems are common – slope erosion and slope instability. Slope erosion is often mitigated by appropriate surface water controls. Slope instability due to elevated transient water pressures is more difficult to mitigate. Analysis procedures and acceptability criteria are rare, but do exist. In Peru, for example, slopes are required by law to be designed for a 100-year storm."

Jan 1, 2016

The annual general meeting of the Branch was held at the St. Helena Club on Thursday, August 21, 1969. Mr J. G. Kirchner (Chairman) was in the Chair. Also present were Mr R. C. J. Goode, President of the S.A. Institute of Mining and Metallurgy; Nine Members: Messrs N. A. Honnet, W. R. Lawrie, J. N. Saunders, D. D. Waterman (Committee Members), M. G. Cullen, G. C. P. Labuschagne, H. A. G. Slater, I. G. Thomas, T. Zadkin and Nine Associate Members: Messrs R. Campbell, D. E. Couperthwaite, T. M. Espach, J. M. Ferguson, G. W. Futcher, A. G. C. Merson, E. R. Penny, R. B. Sutherland, J. W. van den Munckhof and One Visitor: Mr D. J. McLaren. The Chairman declared the meeting open and, on behalf of the Branch, thanked the President for coming from Johannesburg to attend. MINUTES OF THE PREVIOUSGENERALMEETING As the Minutes of the General Meeting held on June 18, 1969 had not yet been published in the Journal, the Chairman moved that their adoption and the discussion thereof be deferred to the next General Meeting. This motion was adopted unanimously. CHAIRMAN'S ANNUAL REPORT 1968/69 At Mr Kirchner's request, Mr. R. C. J. Goode took the Chair during the presentation of the Chairman's Annual Report. (This report was published in the August 1969 issue of the Journal.) OFFICE BEARERS AND COMMITTEE MEMBERS FOR THE YEAR 1969/70 The Chairman announced that the outgoing Committee had elected the following office bearers for the coming year: Chairman: N. A. Honnet; Vice-Chairman: J. N. Saunders; Immediate Past Chairman: J. G. Kirchner. The Chairman then read a letter from the scrutineers reporting that the following had been elected to the Committee: M. S. Grobler, W. R. Lawrie, L. O. W. Leimer, A. T. Lewis, R. S. Pearson, T. Zadkin. The Chairman thanked the scrutineers for their services, and congratulated Messrs Lawrie, Leimer and Zadkin on their re-election and Messrs Grobler, Lewis and Pearson on their election to the Committee. The Chairman announced that he had heard, with regret, that Mr. T. Zadkin would be leaving the O.F.S. at the end of August, 1969. Mr Zadkin had served on the Committee continuously since the inception of the O.F.S. Branch and records showed that he had only failed to attend three General Meetings in over nine years. The Chairman expressed the gratitude of the Branch for Mr Zadkin's invaluable services to the Institute, congratulated him on his well earned promotion and wished him well in his new position. INDUCTION OF CHAIRMAN The Chairman introduced Mr N. A. Honnet to the meeting by briefly outlining his past career and, after congratulating him on his election, called upon him to take the Chair. In congratulating the out-going Chairman on a very successful term of office, Mr Honnet said that due to the absence of many Committee Members for a large portion of the year Mr Kirchner had carried a heavy burden, and he moved a vote of thanks and appreciation for Mr Kirchner's efforts. This was carried unanimously. GENERAL BUSINESS There were no points raised under this heading. MINING AND METALLURGICAL CONGRESS The Chairman called on Mr W. R. Lawrie to give his talk on aspects of the Mining and Metallurgical Congress recently held in Britain. This presentation was illustrated with photographic slides and proved of great interest to Members. Mr D. D. Waterman proposed a vote of thanks to Mr Lawrie and the Chairman then asked Mr R. C. J. Goode to contribute to Mr Lawrie's address. Mr Goode thanked Mr Kirchner for his efforts during his very successful term of office and congratulated the in-coming Chairman and Vice-Chairman on their election. He then gave a brief talk on aspects of the Congress not dealt with in Mr Lawrie's address. These included the industry's requirements of graduates, the necessity of their rapid advancement and the desirability of sending such young men to attend future Congresses. Mr Goode announced that two symposiums will be sponsored by the Institute next year, one on Tunnelling and the other on Open Cast Workings.

By R. Ciccu

This paper examine the optimization of a beneficiation plant for recovering marketable barites from crude ores of different characteristics. The plant, part of a mining complex in Sardinia, consists of a jig section integrated with a flotation line. The problem has been studied using a suitable model of the process, based upon experimental and field data pertaining to both the characteristics of the feed material and the performance of machinery. Data have been automatically processed with the aid of a computer to find the optimum setting of each section, in order to maximize profit for each kind of ore separately fed to the plant. Moreover, the advantages of blending the various concentrates - not all of them individually marketable - are also demonstrated. The overall economic result can be improved provided suitable proportions of each kind of ore are fed to the plant. Such information is fundamental for the long-term planning of exploitation of available reserves, and provides guidelines for further prospecting. The paper illustrates the washability characteristics of the ore's and describes in detail the model adopted. The results of data processing are then presented in the form of computer graphs and discussed. Finally, conclusions are drawn regarding the advantages of resorting to Operations Research as an aid to management.

Jan 1, 1987