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By L. A. Vermeulen

A simple argument shows that it is impossible for the flight of a rod in contact with a litter bar in a rotary mill to be initiated at that point on the upside of mill rotation when all the forces acting on the rod are in equilibrium. The argument was confirmed experimentally in a study showing that the lift of litter bars is a function of their height, that the rod velocity at the point of departure has a significant radial component, and that the subsequent flight of a rod is along a parabolic trajectory as predicted by elementary mechanics. A quantitative account of the observed effects, which is based on a dynamic theory of the sliding interaction between rods and litter bars, revealed interesting properties of the motions of rods down the surfaces of litter bars when the latter are in uniform circular motion during the rotation of a mill.

Jan 1, 1985

As a token of their gratitude, former pupils of Professor Lucien Denoel, a lecturer on coal-mining in the University of Liege, over a period of forty years, have founded the LUCIEN DENOEL prize. It is awarded, regardless of nationality and diplomas, to the author of a thesis dealing with coal-mining, ventilation, mine-draining methods, the use of explosives in the mine or coal-preparation. The thesis must show a truly scientific approach and considerable originality, and must not have been dealt with in a previous publication. The prize is 60.000 Belgian francs. The articles must be written in French, Dutch, German or English, and contain not more than 10,000 words, figures included. They must be forwarded, in triplicate, to the 'Jury du Prix Lucien DENOEL, c/o A.I.Lg., 22, rue Forgeur, Liege, Belgium,' before 1st July, 1970. The examining board reserves the right to publish the winning thesis in a Belgian magazine.

By B. A. Dukas

The diamond-drilling machine has for many years been the most important exploration tool In the search for and subsequent evaluation of Witwatersrand-type ore deposits. With a view to increasing the range of services that can be provided and, at the same time, counteracting rising drilling costs, new techniques are continuously being developed. Many of these techniques have equal application in surface and in underground exploration. This paper reviews drilling techniques such as non-coring pilot holes and deep wire-line drilling, as well as the design of core-barrels and drilling bits to cater for the specific nature of the job on hand. Special drilling fluids and aluminium rods to assist in normal drilling operations are also discussed. Special mention is made of a bore hole's natural tendency to deviate in a certain direction. The factors that cause deviation are used to the advantage of controlled drilling techniques.

Jan 1, 1983

Dr Andrew Cosgarea, Jr, Associate Director of Opera¬tions of the U.S. Mint, and Chairman of the Awards Committee of the International Precious Metals Institute, announced the IPMI award recipients for 1985. The awards were presented at the Institute's Annual Banquet in New York City on 11th June, 1985. The Distinguished Achievement Award was presented posthumously to Dr E.M. Savitsky, of the A.A. Baikow Institute of Metallurgy of the U.S.S.R., for a life-time career devoted to investigations on the properties of the platinum-group metals. Dr Savitsky investigated over 300 phase diagrams, which became the basis for the selection of alloys and the prediction of properties. He published over 300 technical papers during his career. Dr Savitsky died during the summer of 1984 while being considered for the IPMI Award. The Engelhard Henry J. Albert Award was presented to Dr Stephen J. Lippard, Professor of Chemistry, MIT, in recognition of his research contributions in platinum chemistry and its application to nucleic acids. This prize

Jan 1, 1985

By J. J. C. Heynike

The relationship between population growth and steel consumption since the beginning of the twentieth century is indicated, reference being made to the increasing capacity of production units and the resultant increased pollution in the same area. The need for the control of fugitive emissions with its associated high cost is pointed out. There is a direct relationship between energy and pollution, and examples are given of several improvements that have been made to achieve better energy usage and reduced pollution. Several practical examples of air-pollution control systems are described as applicable to the main metallurgical steel processes of today. In conclusion, reference is made to the fact that, with the improvements attained in reducing pollution, the public will not tolerate a decline in the standards already attained. Environmental control and better energy utilization will continue to be important aspects of steel-plant design and operation.

Jan 1, 1978

By D. G. Krige

The scope and salient features of a general risk-analysis model for the main types of new mining ventures are covered in brief outline. The following special features and their effects on the investment criteria are discussed: - various criteria for viability, - the maximum shortfall of funds, - correlations between the grades of up to five ore constituents and between the corresponding product prices. differential inflation and escalation rates for costs and prices, - the estimation, if relevant, of a pay limit based either on the major product only, or on the two major products jointly, - the likely recovery grades of all the products to be obtained when the ore-body is mined to any such pay limit. - an option to take account of the effect on the pay limit of any negative taxation on marginal ore, - investment analyses in current and real terms for individual groups of investors subscribing for equity and any loan capital on differential terms.

Jan 1, 1979

By Alan Bauer

SYNOPSIS A discussion is presented of the advances that have been made in rotary drilling in recent years and it is indicated how and why these drills have replaced percussive equipment even in the hardest formations at larger than 7 in. diameter. A method is presented showing how it is possible to estimate drill requirements and how to optimize drilling and blasting costs for a particular situation. To do this it is necessary to have, in addition to drill performance data, a knowledge of comparative explosive performance. Current methods of doing this are therefore critically appraised. As hole diameters have increased for overall drilling and blasting economies the question of fragmentation arises. In North America this has been approached on a try-it-and-see basis giving results that, in general, have been very satisfactory. The current drilling and blasting practices in North America are reviewed and reference made to the factors of importance in slope control.

With a number of new mines at the feasibility stage and beyond and with several pellet capacity expansions well underway to reduce sintering activity, Alex Broad looks at the impact of worldwide environmental legislation on the iron ore industry. 'Environmental impact assessment' has become something of a buzz term in the metals and mining industry over the last few years and is sure to be an integral part of any green or brown-field project worldwide by the turn of the century, if it is not already. Given the number of iron ore projects springing up, most notably in deposit-blessed Australia, it is not surprising that the subject of environmental approval has been raising its green head. At the very least the process can slow down a new mine project, or at worst have it deemed unfeasible but in general a government is unlikely to put up unnecessary barriers to a project with the beneficial financial implications of an iron ore deposit.

Jan 1, 1996

The role of research and development In the South African gold-mining industry Presidential Address given by M. D. G. SALAMON, Fellow, Dipl. Eng. (Mining) (Hungary), Ph.D. (Durham) The decision of the gold-mining industry in 1974 to embark on a major ten-year research and development programme was widely publicized at the time. In choosing a subject for this address, I felt almost obliged to use this opportunity to give an account of the progress of this undertaking. On reflection, however, I felt that a simple progress report would not suffice. It seemed important that the programme should be shown in persepective, and that its aims should be outlined to the mining and metallurgical engineering community, many of whom are vitally concerned with the well-being of the gold-mining industry.

Jan 10, 1976

By C. R. Speers

The induced elastic stresses in the sidewalls of gold-mining tunnels at a depth of 4000 m in the Witwatersrand exceed the peak compressive strength of even the best-quality quartzite rocks. Laboratory tests measuring post-yield stress versus strain response show that brittle fracture occurs, followed by a loss in strength associated with strain-softening behaviour. Numerical modeling based on an assumed Mohr-Coulomb criterion fitted to the test results shows that large ongoing deformations of the sidewall occur, leading to total tunnel failure without adequate support. A methodology is presented to enable a quick assessment to be made of support requirements in terms of ground characteristic curves for numerically derived pressure versus displacement. From these curves, estimates can be made of the force levels for cable bolting and of the thickness and strength requirements for shotcrete linings. As an example of its application, the methodology is used in a comparison of the relative stability efficiencies of a square-shaped tunnel and a horizontal ellipse-shaped tunnel.

Jan 1, 1996

By M. H. Moys

Accurate models of mill power are becoming more necessary as the design, operational, and control requirements for grinding mills become more stringent. Models of mill power are reviewed briefly, and a new semi-phenomenological model is derived. The conventional torque-arm model for mill power is combined with a model of the tendency of the load in a mill to centrifuge at high speeds, to describe mill power that can be related to several design variables (such as mil geometry, mill speed, and liner design) and control variables (such as load volume, slurry rheology, and mill speed in the case of variable-speed milling). The semiphenomenological nature of the model allows rational conclusions to be reached concerning the effect of various aspects of mill-load behaviour on mill power. The model is shown to be capable of describing reality with much greater accuracy than is achieved by empirical models such as the Bond model.

Jan 1, 1993

By R. M. Falcon

The paper opens with a summary of the major factors responsible for spontaneous combustion in coal discards. These include heat arising from the oxidation of coal and pyrite, and from the weting of dry or oxidized coal and pyrite; and certain petrographic conditions leading to self-ignition of the coal such as low rank, the presence of a high proportion of reactive constituents, and the occurence of highly porous and botanicaly structured inertinite macerals, The analyses of 6 samples from 2 discard dumps in the Witbank coalfield are included, which show that, according to a three-grade classification of liability to spontaneous combustion, one dump is 'reasonably liable' and the other is 'most liable', It is pointed out that factors other than liability to self-ignition determine the possible utilization of such discards, and that the prevention of oxidation is of great importance if they are to be utilized and spontaneous combustion to be prevented,

Jan 1, 1986

By G. Gafner

The paper gives the reasons for the development of a gold alloy of 990 fineness with good colour, durability, and mechanical properties, and explains why titanium was chosen as the alloying metal. Methods are described for the alloy?s production, solutionizing, and age-hardening. Mechanical properties are given as a function of deformation, age-hardening time, and temperature for three different starting states, and these properties are compared with those of some standard 14 and 18 ct jewelery alloys and pure gold. The effects of various salts and fluxes on the composition of the alloy after heat treatment at 1150, 800, and 500°C are discussed. These indicate how alloy scrap can be refined to pure gold, and how solutionizing and agehardening can be conducted without the use of vacuum equipment. The results of wear tests indicate that the alloy is more durable than normal coinage and jewelery alloys. Tips are given on the grain refining, soldering, and casting of the alloy.

Jan 1, 1989

The comments by Mr Chaston were constructive and much appreciated. Considering firstly the recovery of cassiterite from fine deslimed material. A size distribution analysis shows that 58 per cent of cassiterite in Union Tin flotation concentrate reports in the minus 15 micron (quartz) size range. This is achieved at a recovery of 67 per cent and concentrate grade of 42,6 per cent. It is of interest to note that at Altenberg in East Germany 85 per cent of the tin in deslimed minus 43 micron material is recovered into a 14 to 16 per cent Sn concentrate using para-tolyl arsonic acid as collector. Reconcentration of this material is then carried out using two shaking table stages which recover 53 per cent of the tin in a 50 per cent Sn concentrate. Flotation was resorted to after recovery rates of 35 per cent and concentrate grade of 30 per cent had been achieved in a 275 ton per day plant comprising 130 tables. Tests on tabling of deslimed minus 43 micron material have not been carried out at Union Tin. The cost of equipment actually associated with cassiterite flotation amounts to about R60 000. The

By M. C. van Blerck

Since its introduction in 1956, the capital allowance has been increased and its scope widened. At present the allowance is 10% in respect of two categories of gold mine (post-1973 and other deep level mines) and 6% in respect of natural oil mines. The allowance is a significant incentive encouraging the development of new mines, to the benefit of both the fiscus and the South African economy as a whole. A strong case can be made for increasing the amount and the scope of the allowance. The Margo Report recommendation that the allowance should possibly be replaced with a system of direct grants is, in theory, neutral. However, practical difficulties exist with cash grants and there is concern with the implications elsewhere in the Margo Report that the capital allowance is excessive and that, as a consequence, such direct grants will represent an effective reduction in this incentive. I believe that the best course of action would be the retention (and enhancement) of the capital allowance and the expansion of its scope.

Jan 1, 1988

By H. Scott-Russell

Ladies and Gentlemen. It is my great pleasure on behalf of The South African Institute of Mining and Metallurgy and The Geological Society of South Africa to welcome you to the 15th CMMI Congress and to Southern Africa. It is a great honour to be hosting this event and we have been looking forward to it for a long time. I am sure the technical discussions and visits will be of great value, and I am confident you will return with pleasant memories of places and people in South Africa and neighbouring countries. The theme of this Congress, Resources and Technology', is appropriate for discussions on the ways and means of going forward in the minerals industry to create the employment and wealth so sorely needed in this region. The technical programme will give mineral industry professionals from different parts of the world the opportunity to share experience and expertise for the purpose of making operations more productive, safer and environmentally acceptable to the world at large. Delegates will be exposed to current technical developments by means of 133 papers prepared for the congress: 30 on geological subjects, 45 on mining, 29 on extractive metallurgy, and 29 in the field of metals technology.

Jan 1, 1994

By S. R. Stadler

Koffiefontein Mine commissioned a distributed antenna system as an underground communication backbone for the DISPATCH® production management system during September1999. STAS Ltd, the supplier of the Distributed Antenna System developed the System for an Integrated and Automated Mine (SIAM). This communication system, in conjunction with DISPATCH®, fulfils Koffiefontein Mine’s present and future requirements for accurate draw control, increasing productivity and improving working conditions. The DAS as SIAMnet communication network was selected by the mine, because of its superior data transmission rate of up to 1.5Mbps at 860MHz, video and Ethernet transmission facilities, and future enhancement abilities. The results of the commissioning tests confirmed the quality and integrity of the data and voice communication. The initial installation enabled 9000 metres of underground production tunnels with voice communication inclusive of 3700 metres having data communication. This article discusses the requirements and selection of the telecommunication system for an underground mine. A description of the installed distributed antenna system follows with a summary of the commissioning tests. A discussion of the reliability of the components is followed by conclusions with suitable recommendations. Keywords: distributed antenna system, underground mining, telecommunication system.

Sep 1, 2001

By N. Kernahan, T. Zaniewski

Threshold blasting involves the use of small amounts of high explosive to break and fragment hard rock without having to evacuate mining personnel. The method is easily assimilated and effective in rockbreaking, but requires rigid control on drilling, charging and timing. Current underground trials are aimed at fine-tuning the amount of explosive energy and blast hole geometry to allow the firing of multiple sets of shot holes in a continuous manner. Through correct procedures, the after-blast fumes, dust and fly rock can be contained so as to provide a safe working environment. Threshold blasting hugely reduces the volumes of explosives used in mining and brings to maturity the potential of the process begun by Alfred Nobel when he introduced nitroglycerine, and later dynamite, to mining. Its key contribution is its enabling of continuous mining operations with well understood and relatively low cost technologies. The use of batch blasting, employing large burdens holds the greatest potential for delivering high flow rates of ore at minimal cost. There is good potential for rapid evolution of the concept.

Sep 1, 2001

By H. S. Eisner, J. -P. Leger

Published South African fatality and injury statistics for mine accidents are investigated. Where possible, the South African statistics are compared with those of other countries. Commonly held attitudes to the South African accident experience are also examined. Analysis reveals that the published accident rates present a more favourable picture than the rates actually experienced by underground workers. In addition, fatality rates in South African underground gold and coal mines do not differ significantly and have remained stable over the past decade, although the injury rates have decreased rapidly. No evidence was found that this is due to improved safety, and a comparison with international fatality and injury data suggests that it is not. The underground fatality rate for South African coal mining is, on average, eight times that of the UK, four times that of all EEC coal mines taken together, and over double that of the USA. Despite the unreliability of the injury rates, much has been made in South Africa of their rapid decline, an emphasis that appears to be misplaced.

Jan 1, 1988

By J. G. Ferguson, R. E. Burnton

The nature of the coal and of the roof in No. 3 seam at Coal brook Collieries is such as to preclude the use, during bord and pillar mining, of conventional mining equipment that employs cutting and blasting in its production cycle. Continuous mining machines of the borer type, operating within a mining height range of 1,9-2,3 m, have been successfully employed in No. 3 seam since 1957.The experience gained with this type of equipment, the operational methods adopted, and the results achieved are described. The ventilation method used to eliminate the dust and methane hazards created by this type of equipment is stressed. The limitation on the minimum mining height that can be obtained with the borers in use has lead to the recent introduction of a Rotary Drum type of continuous mining machine. This equipment is capable of operating in areas where the seam width decreases to 1,5m. The production potential of the machine has been proved. The roof conditions created by the cutting action of the Rotary Drum type of miner are not considered satisfactory and a modified drum head profile is to be tried.