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By Van Sint JanM., M. Prudencio

ABSTRACT We report the results of a model-testing program to evaluate the strength characteristics of non-persistent joints. We describe the conditions under which new tensile cracks generate and propagate to connect existing joints so that the rock mass becomes fractured into several blocks, leading to a low strength. The strength of some models was equal to that along a single joint through the full sample length. In models with two joint sets, failure took place along a composite plane, partly sliding along a discontinuous joint and shearing through the intervening intact block of rock, or else by rotation and sliding of the blocks. This last failure mode could also lead to very low model strength. ZUSAMMENFASSUNG Dieser Bericht beschreibt die Ergebnisse von Versuchen mit Modellfelsmassen um den Einfluâ von unterbrochenen Rissen in ihrer Widerstandsfähigkeit zu untersuchen. Es werden die Umstände beschrieben unter denen neue Zugrisse entstehen, sich verbreiten, sich mit bestehenden Rissen verbinden und die Felsmasse in mehrere Felsblöcke zerlegen und zu einer kleinen Widerstandsfestigkeit führen. Der Widerstand einiger Versuchskörper entsprach der Festigkeit eines Risses der die ganze Länge des Versuchskörpers überquert.Versuchkörper mit zwei Rißfamilien versagten unter einer zusammegesetzten Ebene, zum Teil mit Verschiebungen nach unterbrochenen Rißebenen die sich durch Schnittversagen intakter Felsblöcke verbinden, und zum Teil durch Drehungen und Verschiebungen einzelner Felsblöcke. Die letzte Versagunsart kann zu einer stark verminderten Widerstansfähigkeit führen. RÉSUMÉ Nous présentons les résultats de quelques essais fait sur des modèles évaluant les caractéristiques de résistance des fractures discontinues. Nous décrivons les conditions sous lesquelles des nouvelles fissures de traction peuvent s’engendrer et se propager pour faire la connection avec des fractures existantes, de façon que le rocher se fracture en plusieurs blocs, menant à une résistance réduite. La résistance de quelques modèles fut égale a celle d’une fracture traversant toute la longueur du modèle. Pour les modèles ayant deux ensembles de fractures, la rupture a eu lieu sur une surface mixte, causée d’une part, par le glissement sur une fracture discontinue et d’autre part, par la rupture à travers le pont de matériel intact; ou bien par rotation et glissement des blocs. Cette dernière façon de rupture peut aussi aboutir à une très faible résistance des modèles.

Jan 1, 2003

By Pierre Marcotte

Jackleg rock drills expose their operators to high hand-arm vibration levels. To address this problem, an antivibration handle has been developed. The antivibration properties of the handle were achieved through a suspension based on a hinge design, achieved with a torsion spring and o-rings. To provide some bench marking for this new handle and to follow the evolution of its performance over time, a test bench was developed to characterize the vibration emission values of jackleg drills under controlled operating conditions. Testing of four antivibration handles on the test bench have shown reductions of the overall weighted acceleration level in the order of 54 % to 60 %, with most of the attenuation occurring in the zh-axis at the rock drill percussion frequency.

Jan 1, 2008

By L. I. Gonzalez de Vallejo

SRC rockmass classification have been applied to 25 tunnels in Spain and Italy, for which it was found that much heavier supports than those estimated by the RMR index were required. SRC and RMR indices and other relevant geomechanical data were obtained during the site investigation and construction stages. Data corresponding to in situ stress measurements, analysis of tectonic structures, and instability problems arising during construction were used to asses the state of stress. The relationship between tunnel section convergence and the SRC and RMR indices was also analysed. Support measurements based on SRC and RMR classification were compared with those actually used during construction. These analyses indicate that for most of the tunnels examined, supports estimated using the SRC were much closer to those actually installed than those predicted by the RMR index. Bei der Verwendung des SRC-Systems zur Klassifizierung des Gesteins als Baugrund für 25 Tunnel in Spanien und Italien wurde festgestellt, dass viel schwerere Abstützungen benötigt wurden, als wenn die Beurteilung anhand des RMR-Systems angefertigt würde. Die Klassifizierung anhand des SRC- und des RMR-Systems, sowohl als auch andere wichtige geomechanische Daten wurden während des Ablaufs der Erkundungen und der Bauausführung gewonnen. Die Resultate der Messungen der Spannungen vor Ort, die Analyse der tektonischen Struktur und die Stabilitätsprobleme während der Bauausführung wurden dazu verwendet, um den im Felsgrund vorherrschenden Spannungszustand zu definieren. Das Verhältnis der Messungen der Tunnelkonvergenz zu dem SRC- und RMR-Index wurde auch analysiert. Die durch das SRC- und RMR-System vorhergesagte Grösse der Abstützung wurde mit der Grösse der Abstützungen verglichen, die am Bau letztlich verwandt wurden. Diese Vergleiche zeigen, dass für die meisten der studierten Tunnel die Vorhersage der Abstützungen, die anhand des SRC-Systems angefertigt wurden, viel näher der wirklich verwendeten waren als die Vorhersage anhand des RMR-Systems. SRC rockmass la classification ont été appliqué à 25 tunnels en Espagne et l'Italie, pour laquelle il a été trouvé que des appuis beaucoup plus lourds que ceux évalués par l'index RMR ont été exigés. SRC et des index RMR et d'autres données geomechanical appropriées ont été obtenu pendant l'enquête de site et les étapes(scènes) de construction. Les données correspondant aux mesures de stress(d'accent) in situ, l'analyse de structures tectoniques et des problèmes d'instabilité surgissant pendant la construction ont été utilisées aux ânes(culs) l'état de stress(d'accent). Le rapport entre la convergence de section de tunnel et le SRC et les index RMR a été aussi analysé. Les mesures d'appui basées sur SRC et la classification RMR ont été comparées avec ceux en réalité utilisés pendant la construction. Ces analyses indiquent que pour la plupart des tunnels examinés, les appuis évalués utilisant le SRC étaient beaucoup plus proches de ceux en réalité installés que ceux prévus par l'index RMR.

Jan 1, 2003

On 23rd October, 1969, 54 members of the Institute set out at an early hour from Rand Airport in two chartered Dakota aircraft for a visit to the Hendrik Verwoerd Dam site. The weather was at the start rather unpromising but after passing Bloemfontein the overcast cleared and it turned into a glorious day for a most memorable visit. The Institute is indebted to U.C-Dumez-Borie Dams Limited, the main civil engineering contractors, and Mr J. D. McNamara their executive manager, for the very excellent arrangements made for this excursion. From the time the aircraft landed till a slightly belated departure the organisation of the extensive tours arranged for the parties was quite outstanding and a matter for congratulation to all concerned. At each of the many places visited there was a senior official to give an authoritative and comprehensive description of the work under his control. In addition the guides on the buses, loaned by the Department of Water Affairs, kept up an interesting running commentary throughout the day. A further much appreciated facet was the introduction of many of the experts on the site and a brief talk by each after an excellent lunch served at the recreation club. Each visitor also received a brochure with a progress report and a detailed site plan, with various sections highlighted in colour, and obviously prepared at the cost of much time and effort. The visit included tours of the large dolerite quarry, where some 150 000 tons of rock are removed each month, the 42 in. gyratory primary crusher, the secondary crushing and screening plant, the rod mill plant for sand production, and the automated blending and concrete batching plant. The transport of mixed concrete by 'silobuses' to the 6 cu. yd buckets of four Blondin cableways, two of which are radially movable and two with buffing towers, and the placing of the concrete in the huge blocks of the wall was watched from a vantage point. The most interesting part of the visit was without a doubt the inspection of the wall itself and the explanations of the many intricasies of its design and care in construction, covering aspects such as positioning of galleys, interlocking of blocks, reinforcement, refrigeration, actual concrete placing, subsequent grouting, etc. Other points of interest were the very complicated design of the wall itself, the river diversion plans, with three stages of coffer dams, the spillways, and the very well cut penstock tunnels.

By Jack Levin

Dr Laurence AlIison Bushel, a former President of the Chemical, Metallurgical and Mining Society of South Africa, now The South African Institute of Mining and Metallurgy, was born in Queenstown on 20th June, 1910, and died in Johannesburg on 4th November, 1991. There were three distinct periods in the career of Laurie Bushel, each enlivened by some special interests or achievements.

Jan 1, 1991

By S. Jiansheng, H. Nakayama, D. Lu, A. Wang

ABSTRACT: New techniques and methods for 3D geo-mechanical model test are presented in this paper. The new model material NIOS with high density and low cost; the so-called DPSS (Discrete Principal Stress Surface) loading concept, the loading and monitoring system for the generation of the 3D initial stress field of the model test, also the special techniques and apparatuses for modelling the excavation of caverns located deep inside the model material, are developed and introduced. By adopting those new techniques, a very large 3D geo-mechanical model test with high comparability for a newly designed underground powerhouse has been successfully fulfilled. Key Words: 3D model test, underground group caverns, excavation process modeling. ZUSAMMENFASSUNG: Neue Techniken und Methoden für 3D geomechanischen Modellversuch wurden in diesem Artikel vorgestellt. Ein neues Modellmaterial mit hocher Dichte und niedrigem Preis, ein sogenanntes DPSS (Discrete principal stress surface) Ladenkonzept, ein Laden- und Überwachungssystem für die Erzeugung des 3D primären Spannungsfelds und überdies spezielle Techniken und Maschinen für das Ausbruch der tief in dem Versuchsmodell liegenden Kaverne wurden entwickelt. Bei Anwendungen dieser neuen entwickelten Techniken wurde ein sehr großer 3D Modellversuch mit großem Maßstab für ein geplantes unterirdisches Kraftwerk erfolgreich durchgeführt. Stichworte: 3D Modellversuch, unterirdischen Gruppekaverne, Ausbruchsmodellierung Résumé: le test de modèl de Nouvelles techniques et méthodes pour la géo-mécanique 3D est figuré dans ce papier. Le nouveau modèle de matériels NIOS avec la haute densité et le coût bas; la conception proposée de chargement DPSS (Discrete Principal Stress Surface), le système de chargement et de moniteur pour la génération de champs de stress initial du test de modèle, ainsi que les techniques et appareils spéciaux pour modeler les excavations de cavernes profondément localisées dans l’intérieur du matériel de modèle, sont développés et introduits. A travers l’adoptation de ces nouveaux techniques, le test de modèle de la géo-mécanique très large 3D avec la haute comparabilité pour actualiser une nouvelle étude de la centrale électrique sous-terraine a déjà accompli avec succès. Mots de clé: test de modèle 3D, groupes de cavernes sous-terraines, processus de modèle d’excavation

Jan 1, 2003

1. Book reviews Underwater tools, by Donald J. Hackman and Don W. Candy. Columbus (D.S.A.), Battelle Press, 1981. 152 pp. $32,95. Reviewer: B. Schmitz Uranium exploration case histories. Proceedings of Advisory Group Meeting Vienna, IAEA, 1981. Price: Austrian schillings 630. Reviewer: E. C. Kostlin Jet cutting technology, a review and bibliography, edited by Robin Brown. Published by BHRA Fluid Engineering, Cranfield, Bedford MK430AJ, England. Reviewer: D. O'Beirne 2. New Books Proceedings, Twelfth Congress of the Council of Mining and Metallurgical Institutions, by H. W. Glen (editor.) Johannesburg, The South African Institute of Mining and Metallurgy, 1982. 2 vols., 1060 pp. R78,85 (air-mail RI53,85). Amborite. Johannesburg, De Beers Industrial Diamond Division (P.O. Box 916), 1982. 6 pp. Free of charge. 3. New Journal BHRA Fluid Engineering has announced its new journal World Ports and Harbour Abstracts and the associated newsletter World Ports and Harbour News, which are issued from January 1983. The Abstracts is published bi-monthly and costs £60 in the V.K. and E.E.C., and £72 elsewhere. 4. Mintek reports Report 2134D On-line analysis, by X-ray diffraction, of fluorsparcontaining slurries. (First published 30th Sep., 1981.) Report 2135D A preliminary on-line analysis, by X-ray diffraction, of pyrite-containing slurries. (First published 30th Sep., 1981.) Report M28 The measurement of flow velocity distribution in fluids. Report M34 The determination, by atomic-absorption spectrophotometryusing electrothermal atomization, of platinum,palladium, rhodium, ruthenium, and iridium. Report M45 Two computer programmes for the calculation of massand heat balances in the production of high-carbon ferromanganese. Report M50 The development of an on-line gold analyser. Report M54 Major amounts of mercury in native gold from upper Witwatersrand sediments. Report M55 A new robust method for the treatment of analytical data. Report M57 The hydrometallurgical treatment of liquors generated by the leaching of a low-grade matte. Awards for inventions For inventing devices of exceptional value to the mining industry, two mining men were presented with awards in Johannesburg on 25th November, 1982, under the Chamber of Mines' Ideas and Suggestions Scheme. Mr W. W. Malan, President of the Chamber of Mines, made the presentations.

Jan 1, 1983

By R. W. O. Kersten

The main objective of The South African Institute of Mining and Metalurgy is to identify the needs of the mineral and metals sector of the South African economy, and to initiate the means by which the requirements for technology and scientific knowledge can be satisfied. To achieve this, the Institute organizes schools to promote technology transfer and to satisfy the needs of its members for continuing education by the exchange of technical information, the communication of ideas, and the identification of technological problem areas.

Jan 1, 1986

1. Book reviews Tungsten: 1982. London, Mining Journal Books Ltd, 1982. 179 pp. Reviewer: G.A. Brown The geology of industrial minerals in Canada, edited by G.R. Guillet and Wendy Martin. Canadian Institute of Mining and Metallurgy, special volume 29. Reviewer: R.W.O. Kersten Foam flotation - theory and applications, by Ann N. Clarke and David J. Wilson. New York, Marcel Dekker, 1984. 418 pp. Reviewer: B.K. Loveday Industrial and financial indicators of the steel industry, by Patrick Genevaz. Paris, La Chambre des Cartes, 1982. 2 vols. Vol I: Analysis and conclusions, FF3500. Vol. 11: Tables, FF4000. Reviewer: R.J. Dippenaar An encyclopaedia of metallurgy and materials, by C.R. Tottle. Plymouth, Macdonald and Evans and The Metals Society, 1984. 481 pp. RI44,50. Reviewer: P. T. Wedepohl The role of crack growth in metal fatigue, by LP. Pook. London, The Metals Society. Reviewer: C.A. Boothroyd Hydraulic coalmining - new technology and its geological and industrial significance, by H.C. Siebert. Hamm, Zentraldruckerei BAG, 1984. 33 pp. Hydraulic coalmining - hydromining update: potential impact on coal deposits and coal mining industry, by H.C. Siebert. Hamm, Zentraldruckerei BAG, 1984. 130 pp. Victoria's brown coal. A huge fortune in chancery, edited by J .T. Woodcock. The Australasian Institute of Mining and Metallurgy, 1984. 204 pp. Reviewer: J.J. Versluis 2. Canadian publications The following reviews of the activity and developments during 1982 in respect to the chief minerals produced or consumed in Canada are now available. Zirconium. An important mineral commodity. Mineral Policy Sector, Mineral Bulletin MR 202, $6.60. Canadian minerals yearbook 1982. Mineral Policy Sector, Mineral Report 32, $40.75. Canadian reserves of copper, nickel lead, zinc, molybdenum, silver and gold as of January 1, 1983, by W.H. Laughin. $4.20. Mineral Policy Sector, Mineral Bulletin MR 201. Sulphur market profile, by B.W. Boyd. Mineral Policy Sector, MRI 84/5. 3. Mintek publications Report M123 The use of of activated charcoal in a NIMCIX column for the recovery of gold from cyanide solutions. Report M150 Energy transfer in the hearths of submerged-arc furnaces. Report M151 A preliminary investigation of the initiation of pitting corrosion in austenitic stainless steels and nickel-based alloys. Report M154 The reduction of Winterveld chrome spinel at 1300°C under an argon atmosphere in the presence of carbon. Report M165 The development of an improved on-line gold analyser. Report MI67 three nebulizers for use with an inductively coupled plasma spectrometer. 4. New publications Mineral Industry Consultants Association (as at 31st March, 1984). Parkville (Australia), The Australasian Institute of Mining and Metallurgy, 1984. 112 pp. Philosophical and procedural guidelines for the planning professions. Johannesburg, the Environmental Planning Professions Interdisciplinary Committee (EPPIC, P.O. Box 61019, Marshalltown 2107), R2.50. Directiona//y solidified materials for high temperature service, by M. McLean. London, the Metals Society, 1983. 337 pp. Tin and its uses no. 142. Greenford (England), International Tin Research Institute, 1984. Metals engineering International Symposia & Exhibitions Ltd - a subsidiary of Industrial Newspapers PLC - are pleased to announce that they will be organizing a mammoth engineering event, entitled Metals Engineering 86, comprising five important exhibitions in 1986:. Agglomeration A major symposium on agglomeration is being organized in Toronto for the 2nd to 5th of June, 1985. Speakers from around the world (Canada, U.S.A., Brazil, Australia, Japan, West Germany, Italy, India, China, Switzerland, Poland, Yugoslavia, and France) will address delegates on various aspects of agglomeration relative to iron ore, coal, coke, and fuels. Plenary theme papers will also be presented by speakers from Japan, the U.K., and the Netherlands.

Jan 1, 1985

A Special General Meeting, followed by the February General Meeting of the Institute, was held in Kelvin House, Johannesburg, on 18th February, 1970, at 4.30 p.m. Mr J. K. E. Douglas (President) was in the Chair. There were also present 24 Members: Messrs A. R. C. Fowler, R. C. J. Goode, Prof D. D. Howat, Messrs D. G. Maxwell, J. A. Nixon, P. W. J. van Rensburg (Council Members), C. A. Border, J. C. Fritz, E. K. Gibson, P. L. Grimbeek, S. D. Hill, D. A. Immelman, P. J. Uoyd, M. Mrost, C. S. Macphail, D. G. Malan, W. D. Ortlepp, R. S. Pearson, A. J. H. Pole, Dr W. S. Rapson, L. W. P. van den Bosch, R. A. von Maltitz and Dr A. Whillier. Eight Associate Members: Dr M. I. Brittan, Messrs J. Brett, I. E. Clarke, C. L. de Jongh, W. B. Evans, D. Loubser, R. C. More O'Ferrall and G. R. Still. One Graduate: Mr T. J. Kotze. One Student: Mr J. A. Cruise. Nine Visitors: including Dr N. G. W. Cook, Messrs M. D. Labuschagne, A. Nicoll, S. Sadowski, Dr A. M. Starfield and Dr H. Wagner. Secretary: Mr D. C. Visser. Total present: 45. SPECIAL GENERAL MEETING The President: "You will have received notices of the Special General Meeting and I declare it duly constituted. In keeping with the trend of overseas and local institutes, your Council recommends that we should change our membership classification as indicated in the notes of the meeting. The new grades are proposed to replace those presently in the Constitution and By-Laws. In terms of Clause 4.8 of the Constitution a special general meeting must be held for the purpose of considering and, if approved, adopting with or without amendments, the revision of the undermentioned clauses of the Constitution, which Council now recommends should read as follows. Clause 2.2 'Corporate Members shall comprise the grades of Honorary Life Fellow, Fellow and Member', these being the equivalent of Honorary Life Member, Member and Associate Member. Clause 2.6. 'Non-Corporate Member shall comprise the grade of Honorary Fellow, Graduate, Associate and Student.' Are there any questions in regard to this proposal? If not would someone propose that these clauses be amended and adopted?" Proposer: Mr A. J. Nixon. Seconder: Prof D. D. Howat. The motion was then adopted. The President: "It is recommended that Clause 2.15 should read, 'A Corporate of the Member of the Institute shall be entitled to use the following authorised letters designating the grade of Membership in Honorary Life Fellow and Fellow, F.S.A.I.M.M. and Member, M.S.A.I.M.M.' Previously we used the letters M.S.A.Inst.M.M. and your Council considered that we should adopt the simpler lettering. Could I ask someone to propose that this amendment be adopted?" Proposer: Mr R. C. J. Goode.

By Yuandong Qiao, Erdong Li, Chao Lv, Junjian Ye

The gas-based CO reduction of Panzhihua vanadium titanomagnetite concentrate from 1100°C- 1250°C was investigated in this paper. The reduction degree increased with increasing temperature and increasing reduction time. At a temperature of 1250°C and a reduction time of 20 minutes, the metallisation degree reached 92%. The iron-titanium oxide phase transformation during reduction process was Fe2.75Ti0.25O5→Fe2.5Ti0.5O4→FeTiO3→FeTi2O5 according to the X-ray diffraction analysis. The SEM and map scan by energy spectrum of results of reduced samples at different temperatures indicated that the metallic iron particle size increased gradually as the reduction temperature increased. These results can serve as a reference for the reduction of vanadium titanomagnetite by CO. Keywords: Vanadium titanomagnetite concentrate, CO reduction, phase transformation, reaction mechanism

Jan 1, 2020

By G. van Aswegen, J. D. Bosman

Gold bearing deposits in the Witwatersrand consist predominantly of narrow tabular conglomerates with quartzite host rock. Extensive mining of these deposits at depth results in significant stresses being induced in the periphery of the tabular excavations. Where remnant pillars are created excessive stresses have resulted in the dynamic failure of the abutments. At the Hartebeestfontein Mine four brittle shear zones have recently been exposed and investigated. For most part, they represent abutment failure into the weaker hangingwall strata, striking parallel to the abutment, dipping towards the stope, with a sense of displacement consistent with closure of the stope from above. These shear zones are similar to those described in various publications by Ortlepp2: they are essentially brittle shear zones characterised by the presence of very finely comminuted ‘rock flour’ on an obviously freshly sheared surface. The angle between the shear zone wall and extension fractures indicate the sense of shear and the intersection of the extension fractures with the shear zone walls define a strong lineation normal to the direction of slip. It is suggested that these structures are referred to as ‘mining induced dynamic brittle shears’. Les gisements d’or du Witwatersrand consistent principalement de conglomérats tabulaires peu épais contenus dans une quartzite mère. Une exploitation poussée de ces gisements en profondeur a pour résultat l’apparition d’importantes contraintes induites à la périphérie des excavations tabulaires. Là où des piliers restants sont créés, des contraintes excessives ont eu pour résultat une rupture dynamique des appuis. Dans la Mine d’Hartebeestfontein, quatre zones fragiles de cisaillement ont été récemment exposées et étudiées. Dans la plupart des cas, elles représentent une rupture des appuis dans les strates moins solides de la paroi suspendue, orientée parallèlement à l’appui, inclinée en direction du chantier d’abattage avec une direction de mouvement consistante avec l’affaissement du toit de la galerie d’abattage. Ces zones de cisaillement sont similaires à celles décrites par Ortlepp2 dans diverses publications: Ce sont essentiellement des zones cisaillement fragiles caractérisées par la présence de « farine de roche » très finement réduite sur une surface évidemment fraîchement cisaillée. L’angle entre la paroi de la zone de cisaillement et les fractures de tension indiquent le sens du cisaillement et l’intersection des fractures de tension avec les parois de la zone de cisaillement définit une forte délinéation perpendiculaire à la direction du glissement. Il est suggéré que l’on se réfère à de telles structures comme des « cisaillements dynamiques fragiles induits par l‘exploitation ». Goldablagerungen im Witwatersrand bestehen überwiegend aus schmalen tabularen Konglomeraten mit Quarzitwirtgestein. Der umfangreiche Abbau dieser Ablagerungen in der Tiefe resultiert in signifikanten Drücken, die auf die Peripherie der tabularen Aushöhlungen wirken. Wo Restpfeiler hergestellt wurden, resultierten exzessive Drücke im dynamischen Versagen der Auflager. In der Hartebeestfontein Grube wurden kürzlich vier spröde Scherzonen freigelegt und untersucht. Zum größten Teil representieren sie Auflagerversagen im Stratum der schwächeren Stollenfirste, parallel zum Auflager verlaufend, in Richtung Abbaustelle abfallend, mit einem gewissen Grad an Verschiebung konsistent mit der Schliessung der Strosse von oben. Diese Scherzonen sind jenen ähnlich, die in den verschiedenen Publikationen von Ortlepp2 beschrieben werden: sie sind im Wesentlichen spröde Scherzonen, charakterisiert durch das Vorhandensein des sehr fein pulverisierten „Gesteinsmehls“ auf einer offensichtlich frisch abgescherten Oberfläche. Der Winkel zwischen der Scherzonenwand und den Bruchverlängerungen deutet die Richtung der Scherung an und die Kreuzung der Bruchverlängerungen mit der Abscherzone grenzt sich gegen eine starke Lineation normal zur Richtung der Lehne ab. Es wird vorgeschlagen, daß diese Strukturen als `vom Abbau verursachte dynamisch spröde Scherungen’ bezeichnet werden.

Jan 1, 2003

By Dolly Chakraborty, S. Ranganathan, S. N. Sinha

Experiments were conducted to study the influence of temperature, particle size and ore/coke ratio on the kinetics of reduction. The rate of reduction increased with temperature. The reduction of iron was completed at shorter time intervals at temperature above 1000ºC. Usually the reduction of chromium commenced after the reduction of iron was almost complete. Reduction was controlled by diffusion at low temperatures and by chemical reaction at higher temperatures. The nature of the reducing agent had a very significant influence on the rate of reduction. The study showed that chromium was converted into the carbide during reduction. Increasing the size of the reducing agent increased the rate of reduction initially. After a critical size, the rate of reduction decreased. However, increasing the size of the ore particle decreased the rate of reduction, initially. Beyond a critical size, it increased. An optimum particle size of the chromite ore and that of coke must be chosen, particularly in the production of agglomerates to achieve maximum degree of reduction.

Jan 1, 2007

H. W. Glen (ed.). Proceedings of Asbestos Symposium, Johannesburg, South, Africa, 3rd-7th, October, 1977. Randburg, National Institute for Metallurgy, 1978. 158 pp. (Copies obtainable from the Department of Mines, P.O. Box 4584, Johannesburg, 2000 South Africa.) This Symposium, which concentrated on the theme of dose-response relationships for asbestos-related diseases, was attended by an internationally representative group of experts in this field. Bulk solids The Powder Advisory Centre announces its third annual International Conference on Bulk Solids Swrage, Handling and Flow, to be held at the Holiday Inn, Liverpool, on 7th to 9th November, 1978. This sequel to the extremely successful November '76 Stratford and November '77 Nottingham Conferences is again to be co-sponsored by a number of internationally acknowledged professional societies, including the Institute of Materials Handling (through its Bulk Solids Panel), the Institution of Production Engineers, and the American Society of Mechanical Engineers (through its Materials Handling Engineering Division). NIM reports Report no. 1943 A review of the literature on the separation and determination of rare-earth elements. (23rd Mar., 1978.) Report no. 1947 The cation- and anion-exchange behaviour of various base-metal chlorides in polar organic solvents. (lOth Mar., 1978.) Report no. 1948 The measurement of trace amounts of gold in solution by atomic-absorption spectrophotometry and carbon-rod atomization. (28th Feb., 1978.) Report no. 1949 The kinetics of the leaching of zinc sulphide concentrates in acidic solutions containing ferric sulphate. (23rd Mar., 1978.) Report no. 1950 Factors affecting the carbon contents of alloys formed during the prereduction of chromite ores. (31st Mar., 1978.) Report no. 1952 The effect of slag composition on copper losses to silicasaturated iron silicate slags. (31st Mar., 1978.) Report no. 1953 A fundamental investigation into the depression of copper-activated sphalerite. (28th Apr., 1978.) Report no. 1956 An improved ion-exchange separation of rare-earth elements for spectrographic analysis. (10th Mar., 1978.) Report no. 1960 The recovery of ferrochromium from furnace slags and related products. (20th Aug., 1976; declassified 31st Mar., 1978.) Process instrumentation The National Institute for Metallurgy and the South African Institute of Measurement and Control are organizing a symposium that will draw the attention of researchers and industrial workers to the importance of metallurgical process instrumentation.

Jan 1, 1978

By P J. Terbrugge, O K. H Steffen

Open pit slope design has conventionally been effected as a bottom up function utilising available geotechnical information. This results in a decision criterion based on Probability of Failure and Factor of Safety with a risk assessment being carried out on the proposed design slopes. The design approach recommended reverses the process using fault event tree decision methodology. The consequences of this approach are that acceptable risk criteria have to be determined by mine owners. Slopes are then designed by the technical staff to achieve these corporate goals. Benefits that arise from the process are that the owners take a proactive decision on the risk benefit relationship allowing the technical staff to optimise the geotechnical exploration programme and design.

Jan 1, 2006

By Y. Poornachandra Rao, P. C. Sudhakar, L. Malakondaiah

NBV commissioned a 27.6 MVA furnace in the year 2005. This paper explains: a)Furnace design features b)Furnace process control, Direct slag granulation c)Continuous casting, Waste heat recovery, Sintering d) Gas cleaning plant, Protection of Environment. Keywords: Furnace Equipment, SiMn Production, Casting, Heat Recovery and Low hood

Jan 1, 2007

By S. J. Lötter

Analysis of the major and minor components of raw zircon as well as plasma-dissociated zircon was undertaken using inductively coupled plasma optical emission spectroscopy (ICP-OES). Microwave-assisted acid extraction as well as flux fusion using lithium tetraborate were investigated as digestion methods. Microwave-assisted acid extraction samples were analysed with matrix-matched standards. The most successful microwave-assisted acid extractions yielded 44.3(1), 49.75(7), 78.3(3) and 90.0(7) per cent recovery for Zr, Hf, Al, and Fe respectively using sulphuric acid. In no instance was acid extraction capable of complete digestion of the sample matrix. A standard addition method was applied to the flux-fusion samples due to the high complexity of the sample matrix. Method validation for the flux fusion procedure was performed using the SARM 62 certified reference material (CRM) with acceptable recovery ranges being based on the 95 per cent confidence intervals of the CRM. Successful analyses were achieved for Zr, Hf, and Ti with apparent content of 66(6), 1.7(1) and 0.15(1) per cent respectively.

Jan 1, 2012

By D. Bessinger, J. Rabe, J. Zietsman, C. Coetzee, P. H. Lamont, J. Muller

The UCAR® CHILL-KOTE? freeze lining concept combines wall cooling with carbon and graphite refractories of higher thermal conductivities to ?chill? the refractory lining by transferring heat from the refractory lining. Effective sidewall water cooling, together with the efficiency of the heat dissipating conductive refractories, lowers the temperature of the lining to below that of the molten process materials. This causes a layer of slag and process metal to solidify or ?freeze? and form a protective ?skull? which completely coats the refractory hot face. Once formed, the slag skull insulates the refractories, reducing heat loss and protect the lining from erosion, chemical attack, thermal shock, and other stresses. The result: extended life and greatly improved refractory performance. The Ilmenite smelting process depends on the presence of a solidified slag skull to protect sidewall refractory material from chemical attach by molten slag. No known refractory material is able to withstand this corrosive material. To date, UCAR has not applied their Chill Kote ? technology in the ilmenite smelting industry. This paper revolves around the results obtained from conducting an ilmenite smelting campaign on a 500kW DC open-arc furnace with a UCAR designed refractory system. The purpose of this test was to establish the effects such a lining has on refractory wear and the reduction-smelting process. Proper thermo-couple management enabled the authors to monitor lining wear for the duration of the campaign. Prior to the pilot-scale campaign, modeling work was completed to evaluate the feasibility of applying UCAR® CHILL-KOTE? technology to ilmenite smelting furnaces. The successful operation of a pilot-scale furnace equipped with the UCAR® CHILL-KOTE? lining as well as concise modeling suggest that it should be a viable option to consider for an industrial-scale furnace.

Jan 1, 2007

By B. Zlender

ABSTRACT: The paper presents investigation of carboniferous slates from the Trojane hilly area performed on series of samples of equal material. The results of static loading tests show that carboniferous slate is heterogeneous and yields on slate layers. Where that kind of heterogeneity is distinctive the strength results are essentially lower of commonly tests results. The results of dynamical loading tests show that the slate surfaces have the essential meaning for the stability of the material. When those surfaces are moistened the material become unstable. RÉSUMÉ: L'article présente une épreuve des ardoises carbonifères de la région montagneuse de Trojane sur une série des échantillons des matériaux identiques. Les résultats des tests de charge statique montrent que l'ardoise carbonifère est hétérogène et qu'elle cède sur les couches d'ardoise. Quand l'hétérogénéité est distinctive, les résultats de stabilité sont essentiellement plus bas que les résultats obtenus par des tests ordinaires. Les résultats des tests de charge cyclique montrent que les surfaces d'ardoise sont très importantes pour la stabilité du matériel. Quand ces surfaces sont mouillés, le matériel devient instabile. ZUSAMMENFASSUNG: Der Artikel präsentiert die Forschung von Karbonschiefersteinen im Bereich des Bergland Trojane, ausgeführt durch Serien von Proben aus den gleichen Erdmaterial. Die Resultate der statischen Belastungsprüfungen zeigen, das die Karbonschiefersteine heterogen sind und die Schieferflächen nachlassen. Wo bei dieser Art der Heterogenität die Festigkeitsergebnisse wesentlich niedriger sind als bei gewöhnlichen Testergebnissen. Die Ergebnisse der zyklischen Belastungsprüfungen zeigen das die Schieferflächen eine wesentliche Bedeutung für die Stabilität des Erdmaterials haben. Wen diese Schieferflächen befeuchtet sind, wird das Erdmaterial unstabil.

Jan 1, 2003

By Harushige Kusumi, Yuzuru Ashida, Toshiki Watanabe, Toshifumi Matsuoka

ABSTRACT: The technique of various kinds of numerical analysis offered remarkable results to explication of many rock mechanical phenomena. These techniques regarded a rock stratum as a continuum body and solved the governing equation of continuum mechanics by using finite differ-ence method, finite element method and/or others. Using numerical analysis based on continuum mechanics, however, the simulations of destruction phenomena caused by elastic waves and on the other hand, the elastic wave propagation which generated by fracturing events are quite difficult. In this paper, we express a rock stratum by a granular body model and develop a simulation tech-nique can simulate both wave phenomena and destruction phenomena at once. The DEM (discrete element method) simulation results are compared with finite difference solutions of elastic wave equation. Furthermore, we simulate Hopkinson effect by this proposed method. Hopkinson effect is famous as a destruction phenomenon caused by elastic wave propagation. ABRISS: In dieser Studie drücken wird eine Felsschicht durch ein Granularkörpermodell aus und entwickeln eine Simulationstechnik, die sowohl Wellenphänomene als auch Zerstörungsphänomene simulieren kann. Die Ergebnisse der Simulation mit DEM (Diskrete-Elemente-Methode) werden mit denen der Finit-Differenz-Lösung von Gleichungen elastischer Wellen verglichen. Desweiteren simulierten wir den Hopkinson-Effekt mit dieser vorgeschlagenen Methode. Der Hopkinson-Effekt ist als Zerstörungsphänomen berühmt, verursacht durch Fortpflanzung elastischer Wellen. RESUME: Dans cette étude, nous exprimons un lit de roches par un modèle à corps granulaire et développons une technique, permettant de simuler d'un coup le phénomène des ondes et le phé-nomène de destruction. Les résultats de la simulation DEM (méthode d'éléments discrets) sont comparés aux solutions à différence finie de l'équation d'ondes élastiques. En outre, nous simulons l'effet d'Hopkinson par la méthode proposée. L'effet d'Hopkinson est connu comme phénomène de destruction, causé par la propagation d'ondes élastiques.

Jan 1, 2003