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By I. V. Lunkin, E. B. Rakishev, B. R. Rakishev

In mining the method of statistical tests is used by solving of problems, exposing to influence of random factors. Such problems are: rational selection of equipment set; co-ordination in time of different processes; interaction between some processes and kinds of works. Usually it is considered that Monte Carlo method proves its value in the first place in that problems, which allow theoretical-probabilistic description. Analysis of numerical solution of mining-economic problems shows that the method of statistical tests may be used successfully by solving of determinate problems, which are solved usually analytically or by the methods of mathematical programming. We are talking about the problems of optimal use of resources, expedient placing of equipment, effective use of investments, rational planning of stripping and extracting works, groups of mining enterprises and about different variants of transport problem. In the report possibility of the method use is studied at an example of typical technical-economic problems solving. By solving of these problems the variant of the method with uniform distribution of random quantity had been applied and built-in random number generator of visual modelling system VisSim had been used. By algorithms elaboration it seems very perspective to use combination of the Monte Carlo method with traditional methods of numerical solving of the problems (methods of linear, nonlinear and dynamic programming and so on). Keywords: method of statistical tests, mining-technical problems, diapason of random number sample, efficiency function and its extremum.

Jan 1, 2003

By C. F. Vos, J. D. Miller, J. C. Davidtz

Small replacements of C12-trithiocarbonate (C12-TTC) for dithiocarbonate (DTC)/dithiophosphate(DTP) in a reagent suite for the flotation of platinum group metals (PGM) have significantly improved the rejection of gangue. Coupled to this is an improvement in kinetics, grade and recovery of PGMs. In a pilot-plant trial, after a 5 mole per cent replacement of the current DTC/DTP collector combination by C12-TTC, large opaque bubbles were replaced by small clear ones. In addition, a similar flotation response was realized with one-third of the current depressant dosage. During a preliminary plant trial on underground UG2 ore, the initial rougher concentrates were characterized by higher PGM concentrate grades and this was in part due to improved chromite rejection. The concentrate produced from the TTC trial also exhibited a much finer particle size distribution. The overall circuit performance, which included secondary regrind and flotation, showed an increase in concentrate grade of approximately 44% while the tailings grade remained unchanged

Jan 1, 2006

By H. L. Monro

Contribution by B. K. Martust I congratulate the author on his interesting paper. In my view, the establishment of the level at which South African gold output is at some kind of optimum is an interesting though somewhat academic exercise. Contribution by D. M. Hawkins* The thesis of the paper is a very interesting one, but, before it is used as the basis of any firm proposals to restructure the mining industry, which changes may be irreversible, one should be very sure that the basis of the calculations is sound. Contribution by P. J. Niewenhuizen* The hypothesis advanced by Mr Monro that the demonetization of gold in August 1971 introduced a major new policy variable, namely the supply-pricejdemand-price relationships, into the decision making process touches on a matter that has never really been given serious thought by the industry. Contribution by B. G. Kingsman* As a co-worker on the development of an econometric model for supply and demand in the world gold market with Mr H. L. Monro, it would perhaps be useful for me to make some comments on the various points raised in the discussions on his paper.

Jan 1, 1984

By D. J. de Beer

South Africa had a late start with rapid prototyping (RP), with the first system being available in 1991. Up to 1994 only three systems were available in SA. Through active research participation from the CSIR and a number of universities, supported by technology transfer programmes and industry awareness workshops, adoption of RP technologies started to grow. Internationally, RP grew to the extent that several country-based member organizations were formed, and an initiation meeting of the Global Alliance of RP Associations (GARPA) took place during the SME Rapid Conference in Dearborn, USA in 1998. South Africa (SA) was invited under the auspices of the Time Compression Technologies Centre (TCTC) launched by the CSIR, and received an invitation to become a member of GARPA through the launch of a national, inclusive organization. The latter gave rise to a RAPDASA planning/launch meeting held at the University of Stellenbosch, which culminated in the first RAPDASA international conference held in November 2000 at the CSIR, and the election of a first RAPDASA management committee, also at the 1st AGM held during the conference. RAPDASA has been a pillar of strength since then, with an annual international conference being presented. As South Africa?s RP awareness grew through the RAPDASA and independent activities, so did the availability of RP platforms in SA.SA also became a benchmark for other countries/late adopters to follow, as slowly a position of following became a position of leading through innovative applications. The paper highlights SA?s development approach and history, together with the discussion of case studies in various fields. Contribution to the light metals industry will also be discussed. Keywords Rapid prototyping, additive manufacturing, product design, rapid tooling, rapid manufacturing, medical product development.

Jan 1, 2011

By M. Hakala, P. Tolppanen

A method to predict stress-induced failures around excavations based on the mapped geological and rock mechanical information is studied. Totally of 7 km of newly excavated tunnels are mapped in the Inmet’s Pyhäsalmi mine in Finland at depth between 1000 - 1440 m from which the results and conclusions from the firstly mapped 1.7 km of tunnels are reported. The main rock type at the site is very hard volcanite having uniaxial compressive strength of 230 MPa in median and GSI-value 72 - 80. The maximum in situ stress around the tunnels is 65 - 85 MPa. The prediction of observed stress failures was preceded by comparing elastic 3-D simulation results of tunnels with three statistical yield criteria. Read’s or Hoek & Brown’s yielding criteria are found the most relevant, though, the effect of anisotropy was found to be significant. The most important parameters having a correlation with stress failures are the tunnel orientation and the foliation of rock. Also, the rock type and its strength, tunnel shape and the geological anomalies have their effects. Further, a delay time on mapping was found to clearly diminishing of the most violent failures. Une méthode de prédiction des contraintes à la rupture autour d'excavation, établie sur la base de cartographie géologique et d'information sur la mécanique des roches, à été étudiée. Au total, 7 km d'un tunnel nouvellement percé à une profondeur de 1000 à 1400 m ont été cartographiés dans la mine de Inmet’s Pyhäsalmi en Finlande. La roche principale du site est une vulcanite dur ayant une résistance à la compression uniaxiale de 230 MPa (valeur moyenne) et une valeur GSI de 72 - 80. La contrainte in situ maximale autour du tunnel se situe entre 65 et 85 MPa. La prédiction des contraintes à la rupture observées a été évaluée en comparant les résultats d'une simulation 3D d'un tunnel avec trois critères de limite d'élasticité statistiques. Le critère de limite d'élasticité de Read ou de Hoek & Brown’s se trouvent être les plus important, même si les effets de l'anisotropie sont significatifs. Les paramètres les plus importants ayant une corrélation avec la rupture sont l'orientation du tunnel et la foliation de la roche. De plus, le type de roche et sa résistance à la compression, la forme du tunnel et les anomalies géologiques ont aussi leur importance. Finalement, un délai dans la cartographie résulte en une diminution nette des ruptures violentes. Basierend auf kartierten geologischen und felsmechanischen Informationen, wird eine Methode untersucht, um spannngsbedingtes Versagen um Ausbrüche herum vorherzusagen. Insgesamt werden 7 km neu ausgebrochenen Tunnels in einer Tiefe zwischen 1000 und 1400 m in der Inmet Pyhäsalmin Mine in Finnland kartiert. Das hauptsächlich vorkommende Gestein ist sehr hart und vulkanischen Ursprungs mit einer mittleren einachsialen Druckfestigkeit von 230 MPa (Medianwert) und einem GSI-Wert von 72-80. Die maximale In-situ-Spannung im Tunnel beträgt 65-85 MPa. Die Vorhersage von beobachteten Spannungsversagen werden weitergeführt indem man elastische 3-D-Simulationsergebnisse von Tunneln mit drei statistischen Fliesskriterien vergleicht. Read's oder Hoek's Fliesskriteria werden dabei als die relevantesten Kriterien angesehen, obwohl auch der Effekt der Anisotropie als wesentlich erachtet wird. Die wichtigsten Parameter für eine Korrelation von Spannungsversagen sind die Orientierung des Tunnels und die Schieferung der Gesteinsschichten. Desweiteren haben Gesteinsart, Tunnelprofil und geologische Anomalien ihren Einfluss. Ausserdem zeigt sich, dass eine Verzögerung bei der Kartierung die ausgeprägtesten Versagen deutlich verringern.

Jan 1, 2003

By J. Petersen, H. Naderi, M. H. Nikzad, M. Karimi

In this research, the thermodynamic study of sodium persulfate (Na2S2O8) solution in the presence and absence of H2SO4 and Fe3(SO4)3 was done. Eh-pH and equilibrium distribution diagrams were constructed using Outotec HSC Chemistry Software and the main stable ionic species were determined. Also, the mean activity coefficient and Pitzer model coefficients were evaluated. Effects of system composition, sodium persulfate concentration and temperature were investigated. According to the results, HS2O7 -, HS2O8 -, S5O3 2-, S4O3 2-, S3O3 2-, HS- and NaSO4 - are the main stable species in these three systems. Increasing of sodium persulfate concentration resulted in disappearing of SO4 2- and the appearance of NaSO4 -. The main effect of increasing the temperature from 25 to 75oC, is changing the stability regions of HS2O7 -, NaSO4 -, SO4 2- and S2-. From equilibrium studies, it was concluded that at 25 and 50oC, increasing the persulfate concentration results in a 55-60% decrease for HS2O7 - and an 20- 30% increase for HS2O8 -. At 75oC, HS2O8 - becomes the main species and its percentage decreases with increasing the persulfate concentration. Keywords: Thermodynamic, sodium persulfate, activity coefficient

Jan 1, 2020

By J. L. Havenga

South Africa produces about 400 Kt zircon (ZrSiO4) per annum. This represents about 30 percent of the global demand. However, very little is beneficiated locally and more than 95 percent is exported with little or no value addition. Zircon is a very inert material and needs to undergo high-temperature alkaline melting processes to produce valuable zirconium products. The conversion of zircon to plasma-dissociated zircon (PDZ) produces a chemically reactive species (ZrO2.SiO2) which consist of finely divided submicron monoclinic ZrO2 crystals dispersed in a SiO2 matrix. In this paper, an in-flight, non-transferred arc pilot plasma plant with a capacity of 100 kg/h and which consists of three 150 kW DC plasma torches, is described. The optimization of the plant, which includes the use of different zircon concentrates, the influence of particle size, feed rates, plasma gas, and energy utilization, is discussed.

Jan 1, 2012

By J. L. Havenga

South Africa produces about 400 Kt zircon (ZrSiO4) per annum. This represents about 30 percent of the global demand. However, very little is beneficiated locally and more than 95 percent is exported with little or no value addition. Zircon is a very inert material and needs to undergo high-temperature alkaline melting processes to produce valuable zirconium products. The conversion of zircon to plasma-dissociated zircon (PDZ) produces a chemically reactive species (ZrO2.SiO2) which consist of finely divided submicron monoclinic ZrO2 crystals dispersed in a SiO2 matrix. In this paper, an in-flight, non-transferred arc pilot plasma plant with a capacity of 100 kg/h and which consists of three 150 kW DC plasma torches, is described. The optimization of the plant, which includes the use of different zircon concentrates, the influence of particle size, feed rates, plasma gas, and energy utilization, is discussed.

Jan 1, 2012

Statistical summary of the mineral industry world production, exports and imports 1964-1969 Published by Her Majesty's Stationery Office, London, on behalf of the Institute of Geological Sciences (1971) The Statistical Summary contains a wealth of care fully garnered information on the production, exports and imports of the principal minerals and mineral products throughout the world for the period 1964-1969, and it should therefore be of particular interest to economic geologists and others concerned with marketing and selling minerals. In view of the intractable nature of the source data it is quite an achievement to have published figures for 1969 so expeditiously. On picking up the Summary this reviewer instinctively compared it with the Annual Yearbook published by the United States Department of the Interior. The Yearbooks have been issued annually since 1882, and today each consists of a set of three separate books containing five volumes. Apart from abundant statistics on the domestic and international mineral industries, the Yearbooks are known for their perspicacious reviews and articles on a host of different facets of the world's minerals industry. Physically the Summary is a much slimmer publication than the Yearbook, and it contains no commentary whatsoever other than occasional footnotes. The principal contents are a series of tables showing production, exports and imports of fifty-nine of the world's more important minerals and mineral products. Each table shows the weight of the material produced or traded, by countries, with figures for each of the six years in adjoining columns. In some cases (e.g. diamonds) values in British currency are quoted in addition to weights. Most of the data have been abstracted from national reports and returns, although in some instances estimates are quoted where national sources are silent--as for example the production of platinum in South Africa. One wonders in passing if any useful purpose is served by the continued suppression of this particular figure. The four South African producers must surely be able to estimate each other's production fairly accurately by now, and one imagines that the national export figures can likewise be synthesised. This reviewer has two minor criticisms of an otherwise praiseworthy publication. Firstly it seems an unnecessary anachronism to perpetuate the split between 'Commonwealth' and 'Other' countries-the split can have little practical significance today. Secondly, what is one to make of the statement that the 1966-1969 figures for exports from Rhodesia of chrome ore and copper, to take two examples only, are 'not available'? It seems improbable that no estimates of these figures have been made since the imposition of sanctions, and inevitably one suspects that the figures have been excluded on policy grounds. Hopefully this problem will have been solved when the next Summary is published. M.J.M. South Africa, land of Challenge by Maurice Tyack France Interpresse, 323 pages, price R18-00. Is South Africa God's richest acre? In its mineral wealth it certainly is, but what of the many other complex overlays of emotions, traditions and racial problems? South Africa, Land of Challenge, provides the background. This is reported to be the first comprehensive documentary work of its kind on South Africa. It is a handsome volume measuring 12ft by 9f', is illustrated by at least 600 photographs of South Africa, more than half of which are in colour, and contains 21 original maps and charts. The book covers the full spectrum of South Africa's very existence, its geography, pre-history, its customs, countryside, natural resources and its cities. The more controversial categories are thoroughly discussed, the people, their policies and politics. Mr Tyack is eminently qualified to write on South Africa, being the author of over 20 books on other African countries and having spent more than three years of research, in the field, in South African archives and also in various libraries and museums, in preparation for this book. The book claims to be free of any party political bias and appears to be an honest attempt at a factual survey. However, a work of this magnitude will undoubtedly leave an impression on the reader and the tone of this book is decidedly patriotic. This is a useful reference work on South Africa that most South Africans will be proud to own. J.P.H. Ergonomics and physical environmental factors This publication by I.L.O. of a symposium in Rome in September 1968 has much useful information for the mining industry in regard to the health and productivity of its labour force. The first subject dealt with is mechanical vibrations. From this section it is clear that men who drive, for many hours each day, vehicles which vibrate in the 6 Hz range are subject to serious physiological and psychological effects. The former may show as changes to the vertebral column (which has a resonance in the 4-5 Hz range). The circulatory system is adversely effected by values in the 6-10 Hz range and the vision is impaired at between 40-100 Hz. Less definite knowledge exists of the effects of vibration on the hand-arm system from mechanical drills etc, although Raynauds disease of the blood vessels of the hand and degenerative diseases of the elbow and shoulder joints occur in men using drills which vibrate, respectively, in the higher and low frequency ranges. Industrial noise is extremely well dealt with and the latest knowledge is summarized. Clear information is given on the relationship between time of exposure to

By E. R. Leeman

INTRODUCTION The first references in the literature to the so-called C.S.I.R. 'doorstopper' strain cell were made in 1964 1,2,3,4. These were the climax of nearly two years of experimental and developmental work with the instruments and the operating techniques involved. Since that time numerous field measurements have been made with 'doorstoppers' and they have been developed to a stage where they are in commercial production and are being supplied to users throughout the world. No detailed description of the latest 'doorstopper' equipment has, however, appeared in print and this paper is written to bring the literature up to date in this respect. The triaxial strain cell was developed three years ago 5, 6, 7 and was first described at the First Congress of the International Society for Rock Mechanics in Lisbon in 1966 8. Since that date laboratory tests and-particularly important-field tests 7' 9 have demonstrated the validity and practicality of the instruments and techniques. These instruments have also been developed to a stage where they have been released for commercial production. In this form they are very different from those described two years ago and a full description of them at this stage seems to be justified. THE INFORMATION SUPPLIED BY 'DOORSTOPPER' AND TRIAXIAL STRAIN CELLS Both the 'doorstopper' and triaxial strain cells were designed specifically to determine the absolute stress in rock using an overcoring stress relieving technique. They were not designed to measure changes in stress. They may, however, be used for the latter purpose provided the glue which is used to stick the strain gauges to the rock is known to possess sufficiently stable strain-time characteristics as not to affect the accuracy of the results during the time the measurements are made. The 'doorstopper' was designed primarily to measure the major principal stress in situations where its direction and those of the two other principal stresses were either known or could be assumed. For example, at great depth in undisturbed virgin ground, it is reasonable to assume that the maximum principal stress is vertical and that the other two lie in a horizontal plane. The borehole in which the 'doorstopper' is installed would thus be drilled in the horizontal plane parallel to one of the minor principal stresses, the direction of which would either have to be assumed or determined as described later. The stresses measured would be the vertical major principal stress and the principal stress acting in a horizontal plane normal to the borehole axis. It is possible, as will be shown later, to obtained the complete state of stress using 'doorstoppers'. In this event, it is necessary to make measurements in three boreholes drilled in any three known directions to each other and relative to a system of three orthogonal axes. The triaxial strain cell was designed to determine the complete state of stress in a single borehole drilled in any direction in any stress field. At first glance it would appear to supersede the 'doorstopper'. This is not necessarily true since there are

The Annual General Meeting of the Branch was held in the Witbank Golf Club on Thursday, 28th August, 1969 at 5.00 p.m. Mr C. G. Sowry (Chairman) was in the Chair. There were also present: Ten Members: Messrs J. Meintjes (Vice-Chairman), J. E. van Aswegen, A. C. Hofmeyr, I. Botha, B. F. v. d. Merwe, C. H. Coxon, R. Canny, R. C. J. Goode, A. Bain, G. E. Carlyon. Six Associate Members: Messrs B. T. Hosking, R. E. Powell, W. Weber, T. Bulloch, E. J. Jackson, P. J. Muller. Fourteen Visitors. Total Present: 31. The Chairman declared the meeting open and extended a welcome to all visitors including Mr R. C. J. Goode, President of the Institute. MINUTES OF PREVIOUS GENERAL MEETING The Minutes of the General Meeting held on the 26th June, 1969, were read and adopted. CHAIRMAN'S REPORT The Chairman presented a report outlining the activities of the Branch during the past year. Membership of the local Branch had increased from 80 to 99 during the year. DECLARATIONOF OFFICEBEARERS The Chairman announced that owing to his transfer out of the Witbank area, he was unable to accept the nomination as Chairman for a further year of office. The outgoing committee had elected Mr J. Meintjes Chairman and Mr A. Bain Vice-Chairman for the ensuing year. Mr J. Meintjes then took the chair. Mr J. Meintjes thanked Mr C. G. Sowry for his successful steering of the Branch during its period of inauguration. ELECTION OF COMMITTEE MEMBERS The Chairman then read the Scrutineers' Report and declared the following eight members elected as Committee Members for the 1969-1970 year: Messrs I. Botha, A. W. Brereton, G. E. Carlyon, B. T. Hosking, E. J. Jackson, B. D. McNeice, P. J. Muller, B. F. van der Merwe. TALK The Chairman then called upon Mr A. Bain to present his talk and film show on 'Impressions of the mining and metallurgy congress tour to Australasia'. CLOSURE After thanking the speaker for an interesting talk, the Chairman declared the Meeting closed at 8.40 p.m.

By J. E. Quintanilha de Menezes, L. Ribeiro e Sousa, I. Ferreira

The Paradela dam has a spillway that makes it possible to discharge a maximum flow of 400 m3/s, the water discharges being on the river Sela, about 2km upstream the river Cávado. After the first use of the spillway, some landslides have occurred on the right bank of the river Sela as a result of the erosion generated on its base about one hundred meters near some houses of a small village. This paper presents a study performed for the slope stability where finite element results are taken into account. A monitoring program was established that essentially consisted of measuring sub-horizontal displacements in points located in boreholes at different depths and also phreatic levels. Some monitoring results are presented. Le barrage de Paradela a une décharge d’eau avec un débit maximal de 400 m3/s sur le fleuve Sela dans un endroit situé environ 2km sur l'amont du fleuve Cávado. Après la première utilisation de cette décharge, quelques glissements se sont vérifiés sur le versant droit du fleuve Sela résultant de l’érosion générée sur sa base dans une zone à 100 mètres de quelques maisons d’un petit village. Ce travail présente une étude réalisée concernant la stabilité du versant avec la considération des résultats des éléments finis. Un programme d’auscultation a été mis en place pour mesurer les déplacements sub-horizontales sur des points situés en forages à des différentes profondeurs. Quelques résultats de cette monitorization sont présentés. Der Ueberlauf des Padela Dammes ermoeglicht das Ablassen einer max. Wassermenge on 400 m3/s in den Sela Fluss, ca. 2 km flussaufwaerts des Cávado Flusses. Nach Inbetriebnahme des Ueberlaufes traten in ca. hundert Meter Entfernung zur Wohnbebauung eine Dorfes Erdrutschungen am rechten Ufer des Sela Flusses auf, die auf Erosionen am Flussbett zurückzuführen waren. In der vorliegenden Studie wurde die Boeschungsstabilitaet unter Beruecksichtigung von Berechnungsergebnissen der Finiten Element Methode untersucht. Es wurde ein essprogramm ausgearbeiten, das im Wesentlichen auf Messungen der Untergrundverformungen in verschiedenen Bohrlochteufen sowie auf Grundwassermessungen beruht. Im Folgenden sind einige Messergebnisse dargestellt.

Jan 1, 2003

By R. M. Spang

Abstract Between the German city of Dresden and the Czech capital Prague a 4-lane highway is under con-struction. At the outskirts of Dresden it will cross the narrow and deeply eroded Weißeritz Valley by a bridge. Two twin tube tunnels under oblique angles join the bridge out of the rocky valley flanks. The different geotechnical conditions of these 4 tunnel portals, their design and construction are described within this publication. The two southern portals of the tunnel Dölzschen are situated within a vertical 65 m high former quarry slope, 25 m above the valley floor. The slope proved instable due to toppling failure and exposed serious rockfall risks. Systematic anchoring, scaling, rock bolting, netting and filling under extreme access conditions eliminated these risks. Tunnel excavation started from the slope surface without any pre-cut or conventional portal construction. The opposite northern portals of the tunnel Coschütz are situated in more gentle rock slopes. After removal of debris, excavation of the eastern tunnel started in a 30° slope striking oblique to the driving direction, without any precut, too. Because of the gentle slope inclination the cross section was not earlier completely covered by rock than 30 m behind. The western tunnel started from an optimized short, narrow and steep precut. Its flanks were stabilized by reinforced shotcrete and rock bolts. Because of the small distance between the tubes rock bolts were drilled into the cross section of the neighboring tunnel. Tunnel excavation was made by drill and blast operation, preliminary support consisted of steel arches, reinforced shotcrete and radial rock bolts. Thorough survey of the bolt’s coordinates and direction prevented them from meeting each other. Rock bolts were of the permanent type to prevent the final lining from being obliquely loaded. Systematically arrayed measuring devices checked deformations of slopes and tunnels. Zusammenfassung Der Neubau der Bundesautobahn A 17 wird Dresden und Prag miteinander verbinden. Die vierspurige Autobahn quert westlich von Dresden das enge und tief eingeschnittene Tal der Wilden Weißeritz mit einer Brücke. An beide Brückenwiderlager schließen mit schiefwinkligem Anschnitt doppelröhrige Tunnel an, deren Portale in den felsigen Talflanken liegen. Die unterschiedlichen geotechnischen Verhältnisse, die Überlegungen für einen jeweils optimalen Entwurf und der Bau der portalnahen bergmännischen Tunnelabschnitte sind Gegenstand dieser Veröffentlichung. Die Südportale des Tunnels Dölzschen liegen in einer vertikalen, 65 m hohen Felswand, 25 m über dem Talgrund. Die Felswand erwies sich als global kippgefährdet, außerdem lagen flächig verteilte erhebliche Steinschlag- und Felssturzrisiken für Bau und Betrieb vor. Die Kippgefahr wurde durch ein Systemraster aus vorgespannten Felsankern, die Steinschlag- und Felssturzrisiken durch bergsteigerisches Beräumen mit dem Brecheisen, Felsnägel und Steinschlagschutznetze eliminiert. Der Tunnelausbruch begann von einer Vorschüttung direkt in der Felswand ohne Voreinschnitt im Schutz einer kurzen Luftbogenstrecke. Die gegenüberliegenden Nordportale des Tunnels Coschütz befinden sich in wesentlich flacheren Hängen. Nach dem Aushub einer mehrere Meter dicken Abraumhalde begann der Tunnelausbruch der östlichen Röhre asymmetrisch mit einer Luftbogenstrecke in einer spitzwinklig zur Vortriebsrichtung streichenden, 30° mit dem Vortrieb steigenden Felsfläche, ebenfalls ohne Voreinschnitt. Wegen der flachen Neigung der Böschung war der Tunnelquerschnitt erst nach 30 m vollständig überdeckt. Für den Vortrieb der westlichen Tunnelröhre mussten erst eine zwischen den Röhren vorhandene Felsnase teilweise abgetragen, die westlich anschließende zurückspringende Felswand vertikal gestellt und gesichert und Felsaushub in der rechten Flanke getätigt werden. Der damit entstehende Voreinschnitt wurde so kurz wie möglich und ohne seitliche Arbeitsräume ausgeführt. Die Sicherung der Böschungen erfolgte mit bewehrtem Spritzbeton und Felsnägeln. Wegen des geringen Abstands der beiden Röhren wurden die unteren Lagen der radialen Ausbruchsicherung durchgeankert. Der Tunnelvortrieb begann im Schutz eines geankerten Portalkranzes und ebenfalls von einer Luftbogenstrecke aus.

Jan 1, 2003

By C. Ware, R. Uken, G. Whitmore

The coastal dune cordon of northern KwaZulu-Natal is among the highest in the world reaching heights in excess of 180 m and up to 2 km in width. It comprises a complex system of Quaternary stacked dunes of various geomorphologies, types and ages (Sudan, 1999; Maud and Botha, 2002;Ware et al., 2001; Ware, 2003). The dunes contain economic heavy minerals that have been exploited for the last two and a half decades. Dune units have recently been defined based on sand composition and texture(Sudan, 1999; Ware, 2003). Despite this, little work has been undertaken on the clay-fraction (< 2 um). This work documents the weathering of dunes to form clays. From the documented clay assemblages and relative abundances, a simplified weathering sequence with increasing maturity can be summarized as follows: primary minerals ? illite + vermiculite ?illite +interstratifications ?illite + montmorillonite ?halloysite + interstratifications + kaolinite ?kaolinite. The dominant controlling factors in determining clay assemblages is pH and leaching conditions. The presence of carbonates results in an alkaline pH and high concentrations of Ca2+and Mg2+which favours the formation of montmorillonite and vermiculite. However, vermiculite tends to form under slightly acidic conditions and is indicative of palaeosols where organic acids produce localized acidic pH’s. In contrast to this, kaolinite will only form and concentrate when carbonates have been leached. Kaolinite dominated samples are considered very mature under current climatic conditions(Chamley, 1989). Halloysite represents a transitional phase between montmorillonite and kaolinite (Herbillon et al., 1981). Ion mobility and evacuation is also critical in determining clay assemblages. Past work and field studies indicate that the dune cordon acts as an open system, resulting in carbonates and mobile ions being readily leached and lost from the system. However, when prolonged weathering has caused an accumulation of fine-grained material, the permeability decreases substantially whereby mobile cations and silica cannot be readily evacuated. This results in the formation of montmorillonite rather than kaolinite, even when carbonates have been leached. Illite (sericite) is considered to alter directly from feldspars. However, dune stacking and geometries, vegetation, water fluxes, reworking and erosion complicates this sequence.

Jan 1, 2003

1. Book review . Fundamentals of fracture mechanics, by J.F. Knot. London, Buterworths, 1981 (reprint). Reviewer: G. Leadbeater The present reviewer approached the above book as a relative novice on the intricate details of fracture mechanics. Thus, the review is based to a great extent on how easily the information presented can be assimilated and understood, and how the book&apos;s format and content facilitate this. Note was taken of the preface comments about jumping ahead, in chapters, to ease understanding, and this was found to be a common occurence. 2. New publications Mechanical testing. London, The Institute of Metals, 1988. 357 pp. £25 Mining potential in northern and southern Canada: Guidelines for regional development policy, by Leo J. Verleun and Brian W. Mackenzie. Centre for Resource Studies (Queen&apos;s University, Kingston, Canada K7L 3N6), 1988. 225 pp, $20 Pricing of metals, by Margaret E. Slade. Centre for Resource Studies (see previous item). 149 pages, $20 CRS Perspectives, no. 29.Nov. 1988. Issued by the Centre for Resource Studies (see previous item) Introduction to the modern theory of metals, by Sir Alan Cotrel. London, The Institute of Metals, 1988. 456pp. £18 Mine winding and transport, by S.C. Walker. Amsterdam, Elsevier, 1988. 546pp. Dfl. 275.

Jan 1, 1989

A Colloquium and General Meeting were held on 17th March 1971, the theme being &apos;Future trends in steel production&apos;. Mr V. C. Robinson (President) was in the Chair. The Colloquium was attended by 121 delegates and was opened by the President at 10 a.m. OBITUARIES THE PRESIDENT: &apos;It is my sad duty to announce the death of the following: F. O. Read, Fellow, who joined the Institute in 1957 and passed away on 13th January, 1971. P. G. M. May, Member, who joined the Institute in 1969 and passed away on 10th August, 1970. R. J. J. Rademeyer, Life Fellow, who joined the Institute in 1942 and passed away on 23rd September, 1970. As a mark of respect to the memory of the deceased and in sympathy with the bereaved I would ask you all to rise and observe a few moments silence. CONFIRMATION OF MINUTES THE PRESIDENT: &apos;May we confirm the minutes of the monthly general meeting held on 21st October and 18th November, 1970, as published in the Journal&apos;. Agreed. MEMBERSHIP THE PRESIDENT: &apos;I have much pleasure in announcing that the names of the undermentioned candidates, having been published in accordance with ByLaw 5.2.2, Council has elected them to membership of the Institute in the following grades: FELLOWS: Romain August Lathioor, Paolo Piga, Renato Ribacchi, Willem Frederick Jacobus Smith, Matthew Churchill, Thomas Anthony James Braithwaite, Hugh Patrick Hart, Eleanor Innocentius Muller, David Alton Smith. MEMBERS: Douglas Adendorff, Petrus Jacob du Plooy, James Valentine Grant Middleton, Karl Anders Ullerstam, Josephus Theodorus Johannes van Wyk, Frank Douglas Abbott. GRADUATES: David Mervyn Gilbart-Smith, John Philip Wilcocks Bennie, Hendrik Theunis Burger, Johann Wilhelm Coetzee, Johannes Stephanus StOols, Leon van Tonder, Brian George Harvey, John Kennedy McLean. ASSOCIATES Richard Cyril Lee Stoyell, Terrence Brian Gouws, Alister Rodney Frederick MacDonald. STUDENTS: Andries Groenewald, Christiaan Johannes Hattingh, William Hendrik Hofmeyr, Stanley Thomas Vincent. I welcome the new members to the Institute and congratulate them on their election. COLLOQUIUM The President welcomed everyone present and mentioned that this was the first of the Colloquia which are to replace the Institute&apos;s monthly meetings. He stressed that discussion at Colloquia would be completely informal and would not be recorded unless the contributor requested publication. In conclusion, he thanked the organising committee, the authors and the contributors, and introduced the author of the first paper. The following papers were presented:- &apos;The future development of the Iron and Steel Industry&apos; by J. P. Coetzee (Published in the Journal March 1971). Among those who contributed to the paper were Dr Bleloch, Dr K. Gebhard, Dr Way and Professor Müller. The main point made by Dr Bleloch related to the reserves of coking coal and of coal for power generation this in country and he deduced that in South Africa we are critically short of coking coal. On the basis that 4 million tons per year of coking coal are consumed for our present steel production, over 16 million tons would be required to meet the anticipated expansion in steel output by A.D. 2000. This must be set against the grim forecast made by the Coal Advisory Board in 1967 that our national reserves of coking coal will be exhausted before A.D. 2000. This gives tremendous significance to the development work presently being carried out by Iscor on alternative methods for coke production. On the other hand the blast furnace may have to be replaced by an alternative process for the reduction of iron ores, e.g., the use of rotary kilns followed by electric arc smelting. Dr Bleloch also expressed grave forebodings about the reserves of bituminous coal, pointing out that with present methods of mining the recoverable coal in any given reserve is in general only 50 per cent of that reserve. He stated that in the past seventy years great quantities of coal have been forever placed beyond the reach of mining by being undermined by extraction of lower seams or lost by being burned. A final point made by Dr Bleloch was the fast rise in the capital investment in a fully integrated steel plant, the figure having risen in the past decade from just over R200 to R350 per ton of finished steel per annum. Dr Gebhard spoke of the direct reduction processes for iron making pointing out the difficulties of securing a high percentage of reduction and the relatively high cost of smelting in electric arc furnaces. As an alternative he suggested briquetting the high carbon sponge iron

By S. J. Oosthuizen

This article explores the Fray Farthing Chen (FFC) Cambridge process, a novel method for the electrochemical deoxidation of metal oxides in molten salt, discovered at the University of Cambridge in 1997. The process was hailed as a highly promising, potentially low cost, novel method for the production of titanium metal direct from its oxides. The article should inform researchers in the field of some of the challenges in the commercialization of a novel, high profile process involving multiple stakeholders. The author, former senior process engineer at British Titanium Plc, the company originally tasked with commercializing titanium production via the FFC Cambridge process, reviews the latest literature and discusses past and present progress in the pursuit of low cost titanium metal via this process. Topics explored include the history of the process, attempts at commercialization, NASA?s alternative application, and present status of the process. Keywords FFC Cambridge, titanium, molten salt.

Jan 1, 2011

By C. D. K. Gauert

High-pressure waterjet technology is proposed as an alternative tool for selective underground mining of high-grade ore sections in stratiform orebodies showing a preferred ?bottom? or ?top? enrichment such as the Witwatersrand reefs and the Bushveld Complex platiniferous reefs. This technique, utilizing known mining technology together with more advanced machinery and additives as used in industrial and cleaning applications, may lead to an increased life-of-mine (LOM) for mining operations. A series of experiments was successfully carried out in a laboratory on Witwatersrand quartzite material, indicating acceptable cutting performance. Mining volumes by selectively cutting of reef portions are considered to be comparable to traditional drilling and blasting. Economic advantages of waterjet mining include energy savings due to the lower quantity of gangue rock to be hoisted to surface, as well as savings by a decrease in the usage of blasting materials. Capital expenditure of waterjet cutting, if applied on a broad scale, could be lower in the long term than that of conventional drilling and blasting methods. Mining by the application of high-pressure waterjet technology could become a competitive ?green technology? improving the economics and safety of labour-intensive mining operations. This paper suggests that waterjet cutting at an industrial scale can become a routine hard-rock mining technique in the future. Keywords waterjet cutting, high pressure, mechanized narrow reef mining, abrasive agents, costs, selective mining.

Jan 1, 2013

By K. O. R. Gebhard

Direct reduction-are we moving in the right direction? by K. o. R. GEBHARD INTRODUCTION Numerous forecasts predict a rapid growth rate for direct-reduction processes. The figures quoted are so impressive that many a top manager must fear that he will fall behind in technical development if he does not base a substantial part of his future steelmaking for mass production on direct reduction.

Jan 2, 1974

By A. J. S. Benade, N. B. Strydom, W. H. Van Der Walt

The performance of the improved microclimate suit by N. B. STRYDOM M.Sc., Ph.D. (Illinois) (Fellow), A. J. S. BENADE, B.Sc. (Potch.) (Visitor), and W. H. VAN DERWALT, M.Sc. (Potch.) (Visitor) An assessment has been made of a new improved microclimate jacket when worn by men working for four hours in a hot environment (wet-bulb temperature of 33,9°C and an air speed of 0,4 m/s) and at work rates of 35 Wand 70W. At the lower rate of work in heat, the use of microclimate suits maintained the rectal temperatures of the men at almost the same level as when they worked without that protection at normal room temperature (20°C). At the greater rate of work without protection, the men&apos;s rectal temperatures rose to 40°C within two to three hours, so that they could not complete four hours of work. When they wore microclimate suits, they easily completed four hours of work, and their rectal temperatures were lower than when they worked at the lower rate without protection.

Jan 8, 1975