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By D. A. Viljoen

While coal can be used as a chemical feedstock instead of oil for the production of the petrochemical based commodities that are so important to our modern way of life, the impact that coal is going to make on the world-energy scene is without doubt its more important role in the short- to medium-term. After inflation, energy is probably today's most talked-about and controversial economic issue. It is a plentiful supply of energy that has permitted each of us to live a life of convenience that is matched only by the most fortunate of the aristocracy in history.

Jan 1, 1979

By M. U. Ozbay

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

Jan 1, 1996

By A. J. Jager, G. R. Adams

The pattern of mining-induced fractures ahead of stope faces in deep-level gold mines, as revealed by petroscopic observations, is described. It is shown that there are zones of fractured and unfractured rock ahead of the face, which are about I m wide and continue as discrete entities for at least 12 m parallel to the face and at least 5 m vertically. These zones do not form continuously as mining progresses, but develop from time to time, leaving a solid zone between the fractured zones. The maximum depth of fracturing ahead of the face depends on the rate of energy release.

Jan 1, 1980

By F. W. Petersen

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

Jan 1, 1994

Past work on the ignition of methane-air mixtures by coal-cutting picks is reviewed, with special reference to the factors that contribute to ignitions and ways of reducing them. The main conclusions obtained from this review are outlined for the following aspects: mechanisms of ignition, methane concentrations, and the roles of rock types, cutting parameters, cutting tools, and water. However, many of these factors have been investigated on a qualitative, rather than on a quantitative, basis. A considerable amount of effort over a long period has been expended in this area of research. It is shown that a number of the factors influencing ignitions by machine picks have been researched adequately, but that there is still work to be done. Research is continuing in this area, being concentrated primarily upon the ignition potential of the coal-cutting pick.

Jan 1, 1985

By R. H. Steel

Ingot casting and wire drawing In Iron Age Southern Africa by R. H. STEEL (Visitor) This paper describes the experiments that were conducted in 1974/1975 on two related aspects of Iron Age copper technology in Southern Africa: ingot casting and wire drawing. Three types of ingot were successfully cast: the St Andrew's Cross ingot, the marale ingot, and the musuku. It is suggested that the 'studs' on the musuku are not the remains of broken-off rods as previously proposed by other investigators, but that the ridged pattern is an ornamental feature. Copper wire was successfully drawn with similar tools and according to the procedures described in the literature on African Iron Age wire drawing. It is concluded that these accounts are generally accurate and that the pre-European metal workers are worthy of respect for the results they achieved with primitive methods.

Jan 11, 1975

The aspect ratio (mill diameter/mill length) of autogenous and semi autogenous mills varies widely and can be as high as three or as low as 0.5. The literature on the subject of what effect aspect ratio has on grinding mill performance or energy efficiency is almost non-existent. However, at the design stage of many grinding circuits the subject is often vigorously debated amongst metallurgists. In this paper the performance characteristics of mills with different aspect ratios are examined to determine whether process performance characteristics are a function of aspect ratio and whether high aspect ratio mills are any more or less energy efficient than low aspect ratio units. Data from both pilot and full-scale mills are used for this purpose in open and closed circuit configurations.

Jan 1, 2007

Book reviews Fiftieth Annual Report (1971) of the Safety in Mines Research Establishment, published by H. M. Stationery Office, London on behalf of the Department of Trade and Industry. Advances in extractive metallurgy and refining. This excellent volume, published by the Institution of Mining and Metallurgy, contains all the thirty papers presented at the International Symposium held in London in October, 1971. Electric Melting Practice by A. G. E. Robiette, Charles Griffin and Co. 412 pp. In recent years the application of electric furnaces to melting processes has expanded to such an extent that it has become a topic in its own right, quite distinct from the related subject of electric smelting which is still limited, for the most part, to those areas where inexpensive electrical power is available. Optimum use of manpower by A. J. van Zyl. The sixties represented one of the longest periods of sustained economic growth South Africa has experienced. At the same time it caused a certain amount of inflation and an acute manpower shortage.

By J. H. Bulloch

The paper gives an assessment of the available data on the linear elastic fracture mechanics involved in stress corrosion cracking and in the behaviour of reactor pressure-vessel materials exposed to a simulated pressurized water-reactor environment. As a result of the different experimental techniques used in the various studies mentioned, only a few detailed conclusions can be drawn. The data from constant-displacement wedge-opening loading (WOL) tests, with the exception of one study, exhibited very limited or no crack extension during exposure periods of up to 14000 hours. The data from constant-load tests indicated evidence of crack extension, but the nature and extent of the crack extension are still unclear. When crack extension did occur, it was exclusively transgranular in nature. Certain differences in the available test data are tentatively explained in terms of the experimental procedures used, and the need for a consistent code of experimental techniques is highlighted.

Jan 1, 1987

By E. P. Gush

Diamonds, an enigma in a mineral resource sense. Chemically, diamonds are no more than carbon crystals in a cubic system-formed one might add under conditions of great pressure and temperature. They have certain physical properties which are fairly unique. They are very hard, they have a high refractive index, they luminesce, some of them fluoresce, they have a high specific gravity, they don't wet and they are a good conductor of heat. In a way, a rather clinical set of qualities. Of course, these qualities are what give diamonds their use and their beauty. It is on the emotional side that they get complex and stir memories of legends, of beauty, of wealth and romance, of war, happiness, bad luck and curses. It is on the emotional side that the value of a diamond is established, if such a thing is possible. Diamonds are extremely varied, there are more than 5000 categories into which they are sorted, so there is room at each point across the spectrum for their individualities to emerge, and accordingly their attractiveness to each buyer is unique.

Jan 1, 1994

To the members of The South African Institute of Mining and Metallurgy We have audited the annual financial statements set out on pages 272 to 277. These financial statements are the responsibility of the Institute's Council. Our responsibility is to report on these financial statements. We have conducted our audit in accordance with generally accepted auditing standards. These standards require that we plan and perform the audit to obtain reasonable assurance that, in all material respects, fair presentation is achieved in the financial statements. The audit included an evaluation of the appropriateness of the accounting policies, an examination, on a test basis, of evidence that supports the amounts and disclosures included in the financial statements, an assessment of the reasonableness of significant estimates, and a consideration of the appropri¬ateness of the overall financial statement presentation. We consider that our auditing procedures were appropriate in the circumstances to enable us to express our opinion presented here. In our opinion these financial statements fairly present the financial position of the Institute at 30th June, 1996, and the results of its operations for the year then ended in conformity with generally accepted accounting practice.

Jan 1, 1996

Contribution by G. Narsimhan It was with much pleasure that I went through D.F. Malan's excellent paper. The following explanatory and critical note has been the result of my deep study of the paper. Although by qualifications and experience I have been a chemical engineer, involved over four decades with problems in the modeling and simulation of transport-limited (heat and mass) chemical reactions in multi-phase systems, I have of and on interested myself in challenging problems in extractive metallurgy. This is the first time I have veered of to continuum mechanics, at the age of 71! Author's reply. I thank Professor Narsimhan for his extensive contribution to the paper. It provided me with the stimulus to derive an extended model. However, there are some inaccuracies in his arguments that need further discussion. Professor Narsimhan's main concern is that there is not a good enough fit between the derived viscoelastic Kelvin model and the experimental data supplied by Güler1 (see Figure l1 on page 218 of my paper). I will therefore explain the choice of a viscoelastic model in more detail and also make specific comments on the arguments given in his contribution.

Jan 1, 1996

O.F.S. Branch Minutes of the Committee Meeting held in the Committee Room at the St. Helena Club at 4.45 p.m. on Wednesday, 3rd September, 1975. Book reviews JONES, M. J. (ed.). Minerals and the environment. London, Institution of Mining and Metallurgy, 1975. Mining Companies of the world.. 1974/75. London, Mining Journal Books Ltd (15 Wilson Street), 1975. £12. 303 pp. NIM reports Report no. 483 Summary of the mineralogical investigation of pegmatites. (11th April, 1969; re-issued October 1975). Report no. 1697 A petrographic and mineralogical investigation of silica samples from the farm Elandskraal 470JQ, Rustenburg district. (24th Jan., 1975; reissued October 1975). Report no. 1761 The determination, by atomicabsorption spectrophotometry, of minor elements in anode sludges and residues. Report no. 1762 The determination, by instrumental neutron-activation analysis, of some elements in the NI M ROC standard reference materials. Report no. 1770 The spectrophotometric determination of vanadium in chromiumbearing materials. Foundry conference An international foundry confcrence, spomored and organized by South African Institute of Foundrymen, will be held in Johannesburg from 23rd to 27th February, 1976. The themes for each day are follows: Coordination chemistry A symposium on coordination chemistry in extractive metallurgy is to be held in Kelvin House, Johannesburg, on 18th and 19th March, 1976. Practical jet cutting The third international symposium on jet-cutting technology to be organized by BHRA Fluid Engineering will be held in Chicago from 11th to 13th May, 1976, in conjunction with the lIT Rese:uch Institute of Chicago. Hydraulic transport The fourth international conference on the hydraulic transport of solids in pipes (Hydrotransport 4) is being organized by BHRA Fluid Engineering.

Jan 12, 1975

By M. T. Scholtz, I. J. Corrans

Akinetic study of the leaching of pentlandite in acidic ferric sulphate solutions by I. J. CORRANS, (Pr. Eng.). B.Sc. (Chem. Eng.) (Wits.). M.Se. (N.S.W.). Ph.D. (Natal) (Member) and M. T. Scholtz. B.Sc. (Chem. Eng.) (C. T.). Ph.D. (Toronto) (Visitor) A study was made of the kinetics in the leaching of nickel from pentlandite in dilute-acidic ferric sulphate solutions as a basis for subsequent studies on bacterial leaching. The chemical leaching rate was found to be highly dependent on the temperature and the concentration of ferric ions. The proposed mechanism for the leaching process is one involving rate control by chemical processes and mass transport. Good agreement was found between the experimental data and the proposed mechanism.

Jan 5, 1976

By P. Syrjänen, Lovén. P.

Because geostatistics together with block modeling has not been studied in detail before in the rock mechanics, a two-year research program to investigate the practical use of geotechnical modeling was started in Finland in 1999. According to research work results block modeling gives good estimate of overall rock mass quality but it can not identify individual structures like faults and narrow weakness zones. Weakness zones and faults should be mapped from drill cores, surface mapping, geophysical methods etc. and manually generate 3-D structural model. Rock mechanical 3-D modeling can be used for preliminary stope dimensioning and preliminary reinforcement design. Detailed design needs rock quality mapping from drifts during excavation work. La géostatistique associée à la modélisation par blocs n'ayant pas été étudiée en détail jusqu'à présent dans la mécanique des roches, un programme de recherche sur deux ans visant à examiner l'utilisation pratique de la modélisation géotechnique a été lancé en Finlande en 1999. D'après les résultats des travaux de recherche, la modélisation par blocs donne une bonne estimation de la qualité générale de la masse rocheuse mais elle ne permet pas d'identifier les structures individuelles comme les failles et les zones géologiquement dégradées étroites. Ces zones et failles devraient être cartographiées à partir de carottes de sondages, d'une cartographie de surface, de méthodes géophysiques, etc. et générer manuellement un modèle de structure 3D. La modélisation mécanique des roches en 3D peut être utilisée pour un dimensionnement de la chambre et un plan d'armature préliminaires. Un plan détaillé nécessite l'élaboration d'une cartographie de la qualité des roches des galeries lors des travaux d'excavation. Da man früher Geostatik und Block-Modellieren in der Gebirgsmechanik nicht detailliert untersuchte, wurde 1999 in Finnland ein zweijähriges Untersuchungsprogramm in Angriff genommen. Aufgrund der Untersuchungsergebnisse ergibt das Block-Modellieren eine gute Beurteilung der gesamten Gebirgsmassenqualität, kann jedoch einzelne Strukturen wie Verwerfungen und kleine Schwachzonen nicht identifizieren. Schwachzonen und Verwerfungen müssen demnach aus Bohrkernen, oder mit Hilfe von Oberflächenkartierung, geophysischen Verfahren usw. ermittelt und danach ein 3-D-Strukturmodell manuell erstellt werden. Felsmechanisches 3-D-Modellieren ist für die vorbereitende Abbaudimensionierung und für die vorbereitende Bewehrungsplanung verwendbar. Ein detaillierter Entwurf benötigt die Kartierung der Gesteinsqualität aus den Gesteinsstrecken während der Ausbrucharbeiten.

Jan 1, 2003

An investigation into the stability of large open stopes at Premier diamond mine, Culinan, South Africa, is described. The open stopes are located in a weak kimberlite orebody, directly underneath a 75 m-thick sill of gabbro. Two and three-dimensional stress analyses were carried out in a back-analysis of the stresses and failure around the first open stope created under the sill. The results were used in the prediction of the future stability of the planned open stopes, intervening pillars, and sill.

Jan 1, 1987

By S. M. Rupprecht

The transportation of men, material and rock in mechanization programmes is often neglected, or at least plays only a secondary function, as the primary focus is on proving the technology. This is despite recognition of the fact that mechanization is essential if gold mines are to remain competitive. However, the use of totally mechanized systems will require further research in the short to medium term before they become generally available. Thus, there is a real need to improve mechanized men, material and rock transportation systems as they are currently used. This applies to both reef horizons as well as to horizontal transport systems. Keywords: Transportation, rock handling, material handling, men transportation, face cleaning, gully cleaning, continuous scraper, monorail, mechanized raise climber, mechanization.

Sep 1, 2001

By M. J. Nicol

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

Jan 1, 1983

By W. O. Ortlepp

This note considers the most fundamental concepts of support design for deep underground openings and discusses them briefly in the context of tabular stoping and deep hard-rock tunnelling. It concludes that the conventional re-bar, mesh, and lacing methods that have been widely used in deep gold mines are quite inappropriate for the support of highly stressed tunnels. The following is suggested as the criterion for adequate dynamic support: the energy absorbed by a support unit (yielding through some acceptable limited displacement) should exceed the kinetic energy generated by the mass of rock that is intended to be retained by that unit.

Jan 1, 1995

By A. W. S. Schumann

SYNOPSIS The most economic exploitation of South African coal resources requires sustained study of the balance between known resources and the predicted rate of consumption, against the background of the development of other sources of energy in South Africa and relevant developments elsewhere in the world. A number of the major issues which would arise in such a study are discussed, including the need for a standardized South African definition for coal resources, the merits of sectoral forecasts of consumption compared with global forecasts, the encouragement of a higher recovery from reserves, and the development of an export market for South African coal.