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By D. van Rensburg

Jointed rock slopes are generally stable, as there is no freedom of movement for blocks of rock. In an open- pit mining environment, blasting opens up space into which blocks of rock can fail, resulting in the common occurrence of slope failure. Prior to the blasting of a trim pattern, the immediate highwall is scaled, where loose rock material is removed by means of a mechanical scaler. As mining of the pit progresses, the height of the scaled highwall from the pit floor progressively increases. These highwalls are never scaled again for the remainder of the pit life, and time-dependant deterioration contributes to these highwalls becoming subject to rockfall and, sometimes, slope failure. This paper documents the development of a South African innovation, a remote-controlled mechanical highwall scaler, a world first for the mining industry. The scaler will enable open-pit highwalls to be scaled from crest to toe whenever the need arises. It will reduce the risk associated with highwalls and deliver on the Anglo American promise of producing safe, profitable platinum.

Jan 1, 2012

For the past 12 years, the Universities of Stellenbosch and Cape Town have hosted an annual symposium to discuss research topics in Minerals Processing. Since 1987, this meeting has been held under the auspices of the Western Cape Branch of the South African Institute of Mining and Metallurgy, and has enjoyed much national and international support. In 1993, in place of the usual Symposium, the Branch and Universities collaborated with CSM Associates Ltd and Minerals Engineering Journal is organizing the international Minerals Engineering '93 Conference in Cape Town.

Jan 1, 1993

By S. Botes, H. van der Merwe

While the refractory lining contains the process on a steady-state basis, the tap-hole must provide a channel for transport of molten materials at discreet intervals, with thermal cycling as routine. The tap-hole introduces a discontinuity in any lining, and this fact can lead to failure in the region around the tap-hole before general lining failure occurs. Hence there is a need for a rapid and reliable tap-hole repair technique that can be readily implemented in conjunction with all types of linings. The UCAR®V Repair supplied by GrafTech is a durable solution capable of repairing all types of lining designs and has been extensively utilized in the ferroalloy industry. More than 20 UCAR®V Repairs have been successfully performed in South Africa alone. This paper describes the system in general and reviews recent repairs and their unique challenges.

Jan 1, 2014

By W. Lin, H. Endo, M. Kwasniewski, A. Kamei, M. Takahashi

Uniaxial tension tests were conducted on specimens of eleven granitic rocks which came from eastern Japan, and included a granite, four granodiorites, four tonalites and two gabbros. The axial and transversal deformability of these rocks was determined based on strain measurements using wire strain gauges. The experimental test results revealed that deformational properties of the rocks investigated varied depending on their petrographic features. However, the axial strain and the lateral strain characteristics showed a similar trend for all the rocks, i.e. the stress-strain curves were non-linear throughout the whole stress range from the initial point of loading to the point of ultimate failure. Moreover, the tangent Young's modulus and the ratio of the lateral strain to the axial strain decreased monotonously with the increasing of the axial stress. Still, the deformational properties were different for individual rocks in a quantitative sense. In particular, the difference in the lateral strains among different rocks was more distinct than that in the axial strains. For example, the Poisson's ratio at a stress level equal to 50% of the ultimate strength of a granodiorite was very low, close to zero. Furthermore, the Poisson's ratio of a tonalite was lower than that of a granodiorite, and assumed a negative value. This effect occurred because the lateral strain became positive as it changed from contraction at the initial stage of loading to extension at higher stress levels. There is no ready explanation for this phenomenon; it is believed, however, that it occurs due to microcracks pre-existing in rock materials and/or weak bonds between the adjacent mineral grains. Les essais de traction directe ont été conduits sur les échantillons de onze roches granitiques provenant de la région Est du Japon: un granit, quatre granodiorites, quatre tonalites et deux gabbros. Déformabilité axiale et transversale de ces roches s’était déterminée en utilisant des jauges extensométriques à fil. Les résultats obtenus à partir des essais montrent que la déformabilité des roches examinées varie selon leurs propriétés pétrographiques. Cependant, à partir des essais, une tendance semblable était observée dans les paramètres de la déformation axiale et la déformation latérale de toutes les roches; c'est-à-dire chaque courbe de contrainte-déformation était non-linéaire dans tout l'intervalle de contraintes à partir de l’état initial jusqu’à l’état d’une rupture finale au cours du chargement. De plus, le module tangent de Young et le rapport de la déformation latérale sur la déformation axiale a diminué de manière monotone avec l'augmentation de la contrainte axiale. Cependant, les différences quantitatives de propriétés de déformation sous traction étaient observées entre des roches individuelles. Particulièrement, la différence de déformations latérales était plus notable que celle-là de déformations axiales entre des roches différentes. Par exemple, le coéfficient de Poisson à un niveau de contrainte égal à 50 % de la résistance d'un granodiorite était très bas, près du zéro. En outre, le coéfficient de Poisson de la tonalite était inférieur que celui du granodiorite et a assumé une valeur négative. Cet effet est apporté parce que la déformation latérale est devenue positive en passant de la contraction dans l'étape de chargement initiale à l'extension sous les contraines plus hautes. Il n'y a aucune explication prête de ce phénomène; on prétend, cependant, qu'il est induit par des microfissures préexistantes dans des matériaux rocheux et/ou des joints faibles entre les grains minéraux adjacents. Einaxiale Zugversuche wurden auf Probestuecke von elf frischen, in Ostjapan vorkommenden, granitartigen Gesteinen durchgefuehrt, welche einen Granit, vier Granodiorite, vier Tonalite und zwei Gabbros umfassten. Die axiale und transversale Verformbarkeit von diesen Gesteinen wurde durch Verformungsmessungen mit Drahtdehnungsmessstreifen geklaert. Die experimentellen Versuchsergebnisse offenbarten, dass Verformbarkeitseigenschaften des untersuchten Gesteins in Abhaengigkeit von ihren petrographischen Eigenschaften variierten. Jedoch zeigten die axialen und die lateralen Spannungsdehnungslinien eine aehnliche Tendenz bei allen Gesteinen, d.h. die Verformungskurven waren nicht linear im ganzen Bereich vom Ausgangspunkt des Belastens bis zum Punkt des entgueltigen Bruchs. Ausserdem verringerten sich das tangentiale Elastizitaetsmodul und das Verhaeltnis der lateralen Verformung zur axialen Verformung monoton mit der Erhoehung der axialen Spannung. Dennoch waren die Verformbarkeitseigenschaften der einzelnen Gesteine in der quantitativen Wahrnehmung unterschiedlich. Insbesondere war der Unterschied bezueglich der lateralen Verformungen zwischen verschiedenen Gesteinen eindeutiger, als der in den axialen Verformungen. Z.B. war die Querkontraktionszahl auf einem Spannungsniveau, das 50% der Zugfestigkeit eines Granodiorits entspricht, sehr niedrig und nah an Null. Ausserdem war die Querkontraktionszahl eines Tonalits negativ und deshalb niedriger als die eines Granodiorits. Dieser Effekt trat auf, weil die laterale Verformung, als sie sich von der Kontraktion am Ausgangsstadium des Belastens bis hin zur Ausdehnung auf den hoeheren Spannungsniveaus aenderte, positiv wurde. Es gibt keine fertige Erklaerung fuer dieses Phaenomen; es wird jedoch angenommen, dass es wegen der Mikrorisse auftritt, die vorher im Gesteinsmaterial und/oder in den schwachen Bindungen zwischen den angrenzenden Mineralkoernern existieren.

Jan 1, 2003

By M. Dworzanowski

The difference in the magnetic properties of minerals is the basis for magnetic separation. All minerals can be generally classified as ferromagnetic (strongly magnetic), paramagnetic (weakly magnetic) or diamagnetic (non-magnetic). Magnetic separation can be conducted dry or wet. The majority of the applications of wet magnetic separation in the mining industry are based on the wet drum magnetic separator. The wet drum magnetic separator has been in use for over 50 years and its design is based on a rotating drum installed inside a tank. Inside the drum are stationary, permanent magnets arranged in an arc to provide the magnetic field. These magnets can be of the ceramic ferrite type providing a low intensity magnetic field or of the rare earth type providing a high intensity magnetic field.

Jan 1, 2010

By M. H. Kirchner

Trackless mining at Thabazimbi Mine by M. H. KIRCHNER. Pr. Eng.. B.Sc.. B.Sc. (Elec. Eng.)(Stellenbosch). Dip. Mining (Pta.) Certain aspects of the' methods used in the exploitation, by sub-level caving, of a wide, tabular, steeply dipping orebody are described, reference being made to the use of modern mechanized equipment. Statistics relating to production and labour, as well as some geological details, are given.

By P. Wiesner, H. –M. Stonner

A brief account is given of the influence of sulphuric acid and chloride ions during the recovery of uranium by solvent extraction, followed by a discussion of the settling behaviour of dispersions and models to represent that behaviour. The paper ends with a description of various methods for the recovery of solvent, which is lost in the solvent-extraction process by entrainment and adsorption on solids and by dissolution.

Jan 1, 1982

By J. H. Dalton

The paper reviews the effects of fast-neutron irradiation on the tensile properties of austenitic stainless steels at irradiation temperatures of less than 400°C, using, as an example, work carried out at Pelindaba on an AISI 316 type steel produced in South Africa. Damage produced in these steels at higher irradiation temperatures and fluences is also briefly discussed. The paper concludes with a discussion of some methods of overcoming or decreasing the effects of irradiation damage.

Jan 1, 1979

By D. J. Adams, R. G. Gürtunca

This paper describes the results obtained from a rock-engineering monitoring programme carried out at West Driefontein gold mine, where dewatered and classified tailings have been used as backfils for local and regional support. The in situ behaviour of these backfils and the surounding rockmass were determined, and it was found that the backfil used on this mine has provided significant regional support. The underground observations also showed less rockburst damage in backfiled panels than in unfiled panels, provided the backfil had been placed properly in the stopes.

Jan 1, 1991

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 J. C. Paynter

A review of copper hydrometallurgy by J. C. PAYNTER, B.Sc. (Chem. Eng.) (Visitor) Copper hydrometallurgy is discussed with special reference to the treatment of chalcopyrite concentrates under South African conditions. The following processes are described and illustrated: Sherritt Gordon's ammonia pressure leachilng, the Arbiter Process, sulphuric acid pressure leaching, roasting processes, the Cymet Process, and the ferric chloride process developed at the National Institute for Metallursy. These processes are then compared with respect to the form of sulphur produced (elemental sulphur or sulphate), the character of the iron product and the handling of different types of ore.

Jan 11, 1973

By J. P. M. Hojem, C. Dimitriou, N. C. Joughin

This paper describes the design and construction of the first experimental underground rockcutting machine from measurements of cutting forces determined in tests on small rock specimens in the workshop. The deficiencies of this design, revealed by stoping with almost identical rockcutting machines, are described. An account is given of the design and construction of further experimental machines incorporating substantial improvements which made them technically feasible for use in production.

This paper illustrates the application of numerical modeling methods, in conjunction with limit-equilibrium techniques, to the location of critical slip surfaces in slope-stability problems. Initially, the Spencer slice-based method of analysis is introduced, together with a dynamic-programming algorithm for slip-surface location. This limit-equilibrium method is assessed critically through the use of an illustrative problem. The technique is then extended to locate the critical slip surface for a similar slope, but with more complex constitutive and yield relationships for the material comprising the slope. To this end, the use of the stress field generated from a finite-difference program, together with a dynamic-programming search routine, is presented as an advanced technique of slope-stability analysis for engineers.

Jan 1, 1993

By A. Miller, M. Bétournay

The main objectives of the Mine Mechanisation and Automation program (MMAP) are to enhance health and safety in underground mining operations, facilitate mechanization and automation in narrow- vein and deep mines, provide sound science to regulatory agencies and improve mine profitability. The program, which has a unique underground and surface industrial scale facility, is involved in many multi-partner projects, like hydrogen fuel cell applications, electrification and hydraulification of underground mines, reduction of noise and vibration, miner location device, explosive-free blasting and hoisting. The paper presents an overview of the Mine Mechanisation and Automation Program of Natural Resources Canada and some of the main projects.

Sep 1, 2001

By N. C. Joughin

Potential for the mechanization of stoping in gold mines by N. C. JOUGHIN B.Sc. Eng., Ph.D. (Rand) (Member) The basic requirements for stoping machines are identified first by examination of the mining rates and productivities attained in conventional stoping, and then by examination of a series of problem areas associated with the shape of the reefs, rockbreaking, rockhandling, and the support and design of the machines. Some of the more important machines being developed are described briefly, and their principal features are compared with the basic requirements identified in the first part of the paper. An estimate of the potential demand for the different types of machines is given.

Jan 1, 1976

By A. J. Jager, J. A. Ryder, M. U. Ozbay

This paper deals with procedures used for designing pillar systems in hard-rock tabular mines operating at shallow depths, typically less than 1000 m. A comprehensive review if current practice identifies four types if pillars, namely non-yield, yield, crush and barrier pillars, and the main principles for designing these pillars are outlined. It is shown that the current design methods for pillar systems in South Africa are mainly empirical, each mine developing its pillar-design methods based largely on practical experience. This results in varying pillar layouts, even between neighbouring mines, despite similarities in geology, and depth if mining. It is suggested that some current layouts may fall short if being the best as regards safety, the maximum safe extraction percentages, or flexibility in accommodating future mining scenarios in deeper or otherwise different geological conditions.

Jan 1, 1995

By A. V. L. Narasimham

The practice of refractory lining in Fe Cr furnaces is purely based on the behavior of various refractories used in different parts of the Furnace at elevated temperatures. The choice of the pattern of lining is mostly done on traditionally based concepts. Refractory Lining of a furnace is the most crucial enabler for operational excellence for Ferro Alloys production. During the last few years, no major technological change has taken place in ?Refractory Lining Management?, only freeze lining concept is becoming popular. Many ferro chrome furnaces today, have the refractory lining problems especially at tap holes, resulting in shutdowns and production losses. The author with his experiences for the last 37 years in furnaces of all sizes tried to attempt to investigate into the reasons for premature failure of lining.

Jan 1, 2007

By Siemag Transplan GmbH

At the Hansa Mine in Dortmund, Germany, coarse run-of-mine coal, up to 60 mm in particle size, has been brought to the surface hydraulically from a depth of 850 m since November 1977. Hoisting is done by a three-chamber pipefeeder, by means of which up to 400 t/h can be lifted. The pipefeeder operates without problems, and has so far shown itself to be efficient and reliable. Vertical hoisting can be carried out by water supplied from the surface, from underground, or from a surface water supply in combination with minewater from underground. Water that flows into the mine, which would in any event have to be pumped to the surface, can be utilized for hoisting operations. The energy costs per ton of coal for a lifting height of 850 m vary between 41 and 62 South African cents, and therefore lie within the range of costs that apply to conventional hoisting.

Jan 1, 1980

By A. J. Roets

Despite its growth over the years, necessitating ever¬larger office accommodation, the Gold Fields group changed its head office address in Johannesburg only twice in 94 years. The first move was at the turn of the century, from the then select suburb of Doornfontein to the corner of Fox and Simmonds Streets. The second move was in the thirties, from that address-now the Reserve Bank building-to the well-known address of 75 Fox Street. With the advent of the first mines of the West Wits Line by the end of the thirties, 75 Fox Street proved too small, and the eastern section of the Commissioner Street side of the present head office was added on. In the fifties, when space once more became a serious problem, the old Exploration building was purchased and demolished, and the present west wing on Commissioner Street was built on the site. In the early seventies, cramped conditions again made life difficult and, despite a reorganization of the interior layouts, the need for expansion remained critical. Eventually, the adjacent Hollard Place and parking area became available, and plans for an extended new building complex could he considered. The building project was

Jan 1, 1985

By H. M. Dus, D. J. Smith

Resistivity tests indicated that, at temperatures lower than 1450°C, reducing agents alone, as well as burdens consisting of high-carbon ferrochromium and reducing agents, exhibit wide differences in resistivity. These differences are less pronounced at elevated temperatures. The resistivity of a reducing agent and the volume fraction it occupies are important factors controlling the resistivity of burdens of high-carbon ferrochromium. A mathematical model is formulated to describe the dependence of the resistivity of mixtures of conducting and insulating particles on the particle sizes and the volume fraction occupied by the conducting phase. The resistivity of burdens of high-carbon ferrochromium is high if the particle size of the reducing agent is larger than that of the other components of the burden. A number of reducing agents showed small variations in their reactivity towards chromite ore in the solid state. However, with chromite ore in the liquid state, reduction proceeded more rapidly with reducing agents occupying larger volume fractions. During the smelting of manganese ore, high initial rates of reduction were observed for reducing agents that had a high reactivity towards carbon dioxide and a high content of volatile matter, and that occupied a large volume fraction. High liq'uid-state reactivities were observed for reducing agents occupying a large volume fraction and having a Iow degree of graphitization.

Jan 1, 1980