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By D. G. Krige

By use of models based on the South African gold-mining industry, analyses are made of the effects of changes in the mining tax structure on the .State's tax income from potential new mines; also on the percentage of such mines likely. to be proceeded with. The percentage is affected by the correlation between changes in taxation and in the flotation pay limits !or new mines. It is shown that the State stands to gain both directly and indirectly from raising the level of the capital allowance and from its extension to all mines; and that the reduced taxation resulting from a lowering of the discriminatory high tax formula for the gold mines, would, in respect of potential new mines, be compensated for by a significant increase in the percentage of such mines that would be proceeded with.

Jan 1, 1979

By C. van der Merwe, R. Lumbule, J. Kgomo

"The mining industry in the Democratic Republic of Congo has seen a significant expansion in copper and cobalt production in recent years. The greater proportion of this expansion has arisen through processing of oxide ores. The design of metallurgical processes for these oxide ores is based on the conventional equipment and layout for processing of sulphide ores, and comprises milling followed by leaching, solvent extraction, and electrowinning. The physical characteristics of the oxide ores, however, provide the process design engineer with an opportunity to examine critically the principles on which equipment selection is based and to design processes better suited to these ores. In 2015, ERG Africa began a project to expand the leaching capacity of the Luita hydrometallurgical facility. A number of innovative changes to the conventional process design were included in the modified flow sheet, which were validated when the project reached design throughput in November 2017. Of these changes, the most novel presented an alternative approach to mitigate the impact of colloidal silica on the operation of the solvent extraction plant. Introduction ERG Africa operates the Luita hydrometallurgical facility located at Kakanda in the Democratic Republic of Congo (DRC), treating malachite and heterogenite minerals to recover copper as electrowon cathode and cobalt as a hydroxide precipitate. The process was originally conceived as a heap leach operation followed by direct electrowinning of copper, with solvent extraction (SX) and electrowinning (EW) of cobalt. In preparing the sized ore for the heap leach operations, the undersized ore fraction at a P80 of 625 µm was discharged to a fines storage facility for later processing. This fraction carried with it approximately 30% of the copper contained in the run-of-mine (ROM) ore feed, and an equivalent proportion of cobalt.In a subsequent development, the cobalt SX section was converted to a copper SX facility, the leached cobalt being recovered from a bleed stream from the copper heap leach circuit. The operating cost for the process as then installed placed this facility well in the fourth quartile of the industry cost curve. The initial Luita operation was established in 2010 at a time when metal prices were above long-term averages (copper above US$3.00 per pound; cobalt above US$20.00 per pound), and the drop in prices in 2015/2016 presented a major challenge. The London Metal Exchange (LME) copper price dropped below US$2.00 per pound, with cobalt dropping below US$10.00 per pound in Q1 2016. This set in motion a range of improvement initiatives for the Luita operation. Central to this was the installation of a tank leach circuit to process the discarded fines and a modified SX circuit to manage colloidal silica. The revised Luita circuit reached design capacity in November 2017 and has proven to be well suited to processing of the oxide ore feed. This process design challenges the boundaries of conventional thinking in the areas of leaching, solid/liquid separation, solution management, impurity management, and metal recovery, and is the subject of this paper."

Nov 1, 2018

By Z. Halifa, P. G. Geyer

Tapping a blast furnace is necessary not only to deliver the product, but is also essential for the safety of the furnace and workers in the cast-house. This paper will highlight the practices at ArcelorMittal’s blast furnaces in the Vanderbijlpark Works, with specific focus on tap-hole design and monitoring as well as casting practice. Extension of the tap-hole life and hearth campaign will be illustrated with reference to the methods of maintenance of the tap-holes, troughs, runners, and cast-house equipment. The importance of proper cooling, good thermocouple installation, and temperature monitoring will be explained.

Jan 1, 2014

By G. S. Bartlett

The theme of this Colloquium, survival strategies, not only conveys a sense of urgency but also takes cognizance of the fact that, as in the political arena, tough decisions have to be made and acted upon in the years to come. It is therefore appropriate that the SAIMM, as spokesman for the metallurgical industry, should be dealing with these issues at this time, and I wish to commend the organizers of this Colloquium for focusing on a mater as important as the future of this great industry. In view of this, I regard it as an honour and privilege to officiate on this occasion, where the best of South Africa's brain power in the metallurgical field will be harnessed with a view to moulding strategies for survival.

Jan 1, 1993

By C. J. Tonkin

Compressed air is widely used on South African gold mines. However, due to recent and proposed future electricity tariff increases it is quickly becoming too expensive to produce and use. Boxfront chute systems at ore passes were focused on during this study, and a number of alternative power sources were examined. After comparing primarily costs, and secondarily safety and practicality, of a number of systems based on water and hydraulic oil, a system making use of either air or water was determined to be the most cost effective. A payback time of 8 years was calculated, which will be significantly less taking into account the avoidance of failures due to electricity and water shortages, which would not affect this system due to its ability to swap between either air or water. It was recommended that this system be installed at all boxfront chutes as soon as possible so that the company can begin to benefit from the cost savings.

Jan 1, 2013

The Annual General Meeting of the South African Institute of Mining and Metallurgy was held in Kelvin House on Wednesday, 23rd August, 1978. Mr P. A. von Wielligh (President) was in the chair and declared the meeting open at 16h00. Obituaries The President: It is my sad duty to announce the death of the following members of the Institute : T. K. Prentice and W. E. Gooday, Honorary Life Fellows and Past Presidents; B. S. Allen, J. A. Becking, L. H. Mellor, C. A. Pratt and W. T. Stobart, Life Fellows; J. P. Burls, E. Cameron, M. L. Fitzgerald, C. G. Hinds, A. J. Patrick, H. O. Reisener, N. D. Shuttleworth, N. Soldan and J. Whitehouse, Fellows; T. Gemmell, J. S. A. Oelofse, W. D. Rowe, R. L. J. Shearman and G. M. Thain, Associates. As a mark of respect to the memory of the deceased and in sympathy with the bereaved, I ask you to rise and observe a few moments' silence. Welcome The President: It is now my very pleasant duty to welcome our distinguished guests and visitors. We are pleased to have with us Mr D. A. Etheredge, Vice¬President of the Chamber of Mines of South Africa, and Mrs Etheredge. Mr Etheredge this afternoon represents the mining industry at our meeting. The importance of the close link that over the years has been maintained between the industry and our Institute speaks for itself. We are, therefore, grateful that he and Mrs Etheredge have managed to find the time to be with us this after¬noon.

Jan 1, 1979

By O. O. Ogunmodimu, D. K. Weatherley, M. S. Powell

Discrete element methods (DEM) have provided the ability to resolve the complex phenomena experienced by ore within comminution devices such as tumbling mills. The new developments in DEM techniques and the corresponding increase in computational power have made it more feasible to study the movement of individual ore particles as they traverse a tumbling mill. A range of information can be extracted on individual particle impact histories, such as kinetic energy at the time of collision, velocities of individual particles, per-particle stress tensors, impulse, and collision energy. DEM codes have been modified to provide required information that can be analysed in associated software to investigate the impact of varied operational parameters on the resultant granular dynamics. This paper explores the reaction of individual ore particles to the breakage environment within a tumbling mill using DEM techniques and studies the stressing conditions that would lead to either impact or abrasive breakage. Keywords: DEM, comminution, tumbling mill, breakage

Jan 1, 2020

By G. M. Thain

Ancient Mining - The following three contributions were received for publication in addition to the preceding papers. 1. Ancient gold-mining sites in the Transvaal G. M. THAIN* Pre-European gold mining and working in South Africa is a tantalizing field for conjecture. Well over thousand sites have been identified in Rhodesia, but here we have had to reach double figures, judging by published accounts. Geologically, the Transvaal is less amenable primitive exploitation, but it difficult to reject the idea that the knowledge gained to the north did not have its influence south of the Limpopo.

Jan 1, 1974

By A. Navarra, A. Quelopana

The mine production scheduling problem (MPSP) has been studied since the 1960s, and remains an active area of computational research. In extending the concepts of the MPSP, the automated mine may now be regarded as a hierarchical intelligent agent in which the bottom layer consists of distributed robotic equipment, while strategic functionality occupies the higher layers. Here we present a disambiguation of artificial intelligence, machine learning, computational optimization, and automation within the mining context. Specifically, the Q-learning algorithm has been adapted to generate the initial solutions for a high-performing strategic mine planning algorithm, originally developed by Lamghari, Dimitrakopoulos and Ferland, based on the variable neighbourhood descent (VND) metaheuristic. The hierarchical intelligent agent is presented as an integrative conceptual platform, defining the interaction between our new Q-learning adaptation and Lamghari’s VND, and potentially other hierarchically controlled components of an artificially intelligent mine, having various degrees of automation. Sample computations involving Q-learning and VND are presented.

Dec 1, 2021

By M. Mrost

Slimes disposal at South African gold mines by M. MROST*. M.Sc. (Rand) (Fellow) The soil mechanics, civil engineering, and environmental considerations applicable to the construction of slimes dams on the Witwatersrand gold mines are discussed. It is concluded that, though the procedures used in the construction of dam embankments do not accord with the best possible practice, they are entirely adequate in current local circumstances, provided that proper precautions are taken to ensure that the wall foundations are sufficiently permeable and strong, and that the dams are protected against erosion. If current trends towards larger mining and metallurgical complexes continue, it may become necessary to build larger, higher dams, and to adopt slimes embankmentbuilding practices that are inherently more reliable.

Jan 2, 1974

By F. F. Roxborough, P. King, E. J. Pedroncelli

This paper describes tests on the performance of a continuous miner in cutting South African coal. Although coal cutting has been investigated extensively overseas, the results have not led to significant changes in machine design because these machines find little difficulty in cutting the softer overseas coals at a fast rate. In general, the results of the tests show that cutting efficiency improves markedly as the depth of cut per revolution of the drum increases, and that the best spacing of picks on the drum is twice the depth of cut. Pick shape is of secon¬dary importance in terms of cutting efficiency, only small differences having been found between the performances of conical- and chisel-shaped tools.

Jan 1, 1981

By A. C. Lawrence, K. F. Mauer

Human factors in stope productivity -a field experiment by K. F. MAUER, M.A. (Visitor), and A. C. LAWRENCE, B.Econ., D.Com. (Member) An experiment in which three human variables were manipulated in eight stopes was conducted in a gold mine over a period of roughly six months. The three variables, which each had two levels, concerned the degree of movement from gangs, the quality of the Bantu production supervisors, and the extent to which gangs were composed of a single ethnic group (Malawians). Time was included as a variable with three levels in the analysis of the findings. On the average, stable gangs produced 12 per cent more than gangs with a high percentage of transfers, gangs with better production supervisors were more successful by nearly 9 per cent than those with poorer production supervisors, and homogeneous gangs were more productive than heterogeneous ones by as much as 15 per cent. In addition, it was found that a number of the variables exercised a joint influence on stope productivity and that the effects of the variables were accentuated by the len gth of time they had been in operation. V

Jan 10, 1973

By J. F. Lupo

One of the earliest records of metal recovery by solution leaching is described by Agricola as 'juice of rock' in the 1550s. In these early years of hydrometallurgy and civil engineering, few controls and systems were employed to enhance recovery and protect the environment. Since that time, leaching (dump or heap) operations have made significant strides in increasing metal and solution recovery while protecting the environment, all goals of a sustainable operation. It is now recognized that the design and operation of modern heap leach facilities requires contributions from many fields of study, including hydrometallurgy, civil engineering, geotechnical engineering, unsaturated-flow hydrology, mine planning, geosynthetics engineering, geochemistry, process engineering, mechanical engineering, and electrical engineering. While advancements in these fields have resulted in more sustainable heap leach operations, challenges in the industry still exist. A number of heap leach operations exhibit poor or lower-than-predicted metal recovery, loss of solution flow and control within the ore heap, loss of ore heap stability under leach, failure of liner and/or solution recovery systems, and overtopping of process water ponds. A number of these issues may be the result of several compounding conditions. For example, poor metal recovery may be due to an inadequate scale-up assumption (scaling laboratory tests to field-size heaps), lack of control of the in-heap geochemical environment, changes in ore mineralogy from the original design, changes in mechanical and hydraulic properties of the ore from the original design, ore handling and pre-treatment, inadequate solution management system, and inadequate solution application. The purpose of this paper is to present and discuss issues that may affect the sustainability of a heap leach operation. Since sustainability encompasses a broad range of topics and issues, the focus of this paper will be on issues affecting metal and solution recovery, solution flow and containment, and stability of the ore heap.

Jan 1, 2012

A method is proposed for the evaluation of the influence of grout prestressing systems on the support resistance offered by timber packs. It is shown that, in order not to reduce the load-carrying capacity of timber packs, grout prestressing systems need to be at least as stiff as a single timber rise. The method was used to establish strength specifications for the grout prestressing systems to be used under non-seismic and seismic conditions. For non-seismic requirements, the 24-hour grout strength needs to be at least 1,7 MPa, and the 7-day grout strength 4,9 MPa. The investigation showed that the proposed strength specification is realistic in the light of current grout-strength capabilities. For seismic requirements, the grout strength needs to be at least 4 MPa and 8 MPa to prevent extensive damage to the grout during seismic events with a peak velocity of 1m/s 3 m/s respectively.

Jan 1, 1996

"Chairman: Professor H. S. SICHEL Rapporteur: Miss M. I. WATSONPapers:Unrolling of Copperbelt orebodies by J. H. E. Perry and V. H. WiikAn exploration model for tabular orebodies by G. S. Koch and R. F. LinkHarmonic analysis of copper and gold occurrences in the Arbitibi area of the Canadian Shield by F. P. Agterberg and A. G. FabbriMathematical models of orebodies by M. J. Newton and A. G. Royle Estimation of lateritic-type orebodies by A. JournelIn his presentation Mr Wiik said that unrolling could be regarded as a reversal of the natural process of folding, so that the aim of an unrolling procedure would be the reconstruction of original pre-tectonic conditions. While simply formulated, this aim might not always be achieved. The geometrical relationship between points on the deformed surface and corresponding points on the original surface is process-dependent, and a true reconstruction could be achieved only if the deformation history were known in detail.In this computer unrolling procedure all these complexities were ignored. Referring to one particular marker horizon, Mr Wiik said that it was assumed in the procedure that this marker was deposited as a horizontal stratum and that it had subsequently been deformed by simple flexure-type folding.The procedure allowed the geologist to incorporate his knowledge and conception of the deposit through repeated re-contouring with dummy points. This 'manumatic' aspect of the procedure had proved invaluable, not only in resolving specific unrolling problems but also in making the system more acceptable to the geologists in general.Unrolling served towards removing what might be termed `tectonic noise' superimposed on the primary distribution patterns for regionalized variables such as metal content and orebody thickness. From this point of view, variograms derived on the basis of unrolled-plan co-ordinates should be more meaningful in terms of depositional environment than are variograms calculated from a normal map projection.Mr M. M. Oosterveld remarked that it appeared from the paper that there were problems in applying the unrolling technique to ore reserve calculation, and asked whether there were not other methods that might be used for that purpose.Mr Wiik replied that at present unrolling played only a minor role in practical ore reserve estimation within Roan Consolidated Mines, Limited. The techniques currently in use differed from one orebody to another, but in general they involved projection onto a vertical longitudinal section or a horizontal plan, with subsequent grid interpolation by means of a standard computer contouring package."

Jan 1, 2014

Colloquium And General Meeting - Trackless Mining in Underground Metal Mines A General Meeting and Mining Colloquium on the above topic was held on Wednesday, May 16th, 1973, at Kelvin House. Dr J. P. Hugo (President) was in the chair. The colloquium wasattended by approximately 200 delegates, and was opened by the President at 9.15 a.m. OBITUARIES The President: It is my sad duty to announce the death of the following: W. A. Schwezoff and L. G. S.

By G. W. Holl, E. G. Fairon

A review of some aspects of shaft design by G. W. HOLL, Pr. Eng., Associate of the Mine Managers Association of South Africa (Fellow)- and E. G. FAIRON, Pr. Eng., F.S.A.I.E.E., M.I. Cert. M.E.E., M.I.Mech. E., (Visitor) The reasons for the choice of vertical shafts in preference to inclined shafts of comparable capacity are set out, and the conclusion that the former are superior in virtually all circumstances is substantiated. The shapes of vertical shafts sunk during the past sixty years are recorded, and the shapes of those sunk during the past decade are analysed. From this analysis it is clear that circular and elliptical (and quasi-elliptical) shafts are the shafts of the future and that the rectangular shape will conceivably become obsolete. The determination of the size of shaft is discussed and it is forecast that shafts of a diameter of 13 metres and over will probably be sunk without difficulty in the years to come. The depth of the shaft is determined intrinsically by the Mines and Works Regulations applicable to factors pf safety of winding ropes and the design of the winding system. The Blair winder is the most suitable winder for hoisting rock, men, and material from a depth of, say, 3000 metres on an economic basis. Tertiary shafts will, therefore, be unnecessary in future deep-level mining projects at the limit of depth now envisaged. A few other factors relating to shaft design are described.

By Z. Levinson, R. Dimitrakopoulos

A mining complex is an engineering system where raw materials are extracted from several mines, processed, transported, and sold to the market. The uncertainty and local variability of material grades and their locations within the related mineral deposits are critical for determining the optimal life-of-mine extraction sequence, destination policy, operating modes, and capital investment decisions, which define the production schedule of a mining complex. Infill drilling is used to further characterise a mineral deposit and reveals information that changes the representation of the resource model and potentially the resulting optimal long-term production schedule. A self-learning reinforcement learning approach is proposed to determine the optimal drilling locations that maximise the net-present value of the long-term production schedule and the associated financial forecasts by adapting the schedule to additional information. A case study at a copper mining complex demonstrates a $70 M increase in project value by collecting drilling information with a $1 M budget.

Sep 1, 2021

By P. C. Seligmann

Primary fracture from an array of shotholes by c. M. LOWNDS. B.Sc. Hons. (Rhodes). Ph.D. (Cape) (Visitor) and P. C. SELIGMANN. B.Sc. (Witwatersrand) (Visitor) The effects of stress on the directions of cracks that are propagating in a brittle medium are described. It is shown that the superimposition of stress fields from the holes of an array always adversely affects fragmentation. Consequently, the best fragmentation will result when holes are fired far enough apart in space or time for each to develop its whole crack pattern without disturbance from the others. This concept leads to a philosophy for the design of more effective blasting patterns, which has been verified on model scale and which explains many published, empirical results.

Jan 1, 1976

By L. Pretorius, S. Uludağ

This paper explores how to apply system dynamics principles to surface mining problems towards understanding the consequences of mining efficiencies. Some simulation examples related to machine and people performance have been used to demonstrate systems engineering concepts to mining engineers. The simulation tool used is Vensim, which is widely used in industrial engineering applicable to systems thinking, and systems dynamics. The science and mathematics behind the system dynamics as well as benefits and typical challenges are discussed to explore the applicability to mining problems. The benefit of having one less drill is easily quantifiable with the developed model which is one of many other measurable benefits, using the developed model. Some of the benefits of the improved quality of drill holes are not fully quantified as this depends on the mine specific inputs. There are examples of quantifying this in the other industries using system dynamics tools.

Sep 1, 2021