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By J. A. L. Napier

SYNOPSIS Many tabular mining problems can be modelled effectively by displacement-discontinuity techniques, which can be extended directly to represent fracturing on discrete planes and movements on planes of weakness. This paper presents a unified method for computing the energy changes that occur when multiple discontinuities intersect and are extended incrementally. It shows how this method can be used to deduce energy-release information for standard layout problems and, in addition, how the technique can be incorporated in numerical procedures based on the displacement-discontinuity method. Examples are given to demonstrate the effects of off-reef fracturing and the importance of stope-fault intersections during seismic events.

Jan 1, 1991

By T. Dimillo, R. G. B. Pickeirng

The South African gold and platinum deposits were formed in very different ways and yet both have many similarities. They are flat dipping tabular ore bodies, extremely narrow and located in hard abrasive country rock. The mining methods employed are also similar. Primary access is via shafts or declines; secondary access is via haulages and cross cuts; and tertiary access is from raises. The proposed solution for rapid access described in this paper is focussed on the haulages, cross cuts and raises. The non-explosive rock breaking method has many other applications, however, it is the integration with the Tunnel Digging Machine that results in the first, cost effective, Continuous Tunnelling Machine for hard rock mining.

Sep 1, 2001

By C. J. Fauconnier

The various methods of detecting fires and heatings in collieries are reviewed. The methods described range from those relying principally on human senses to sophisticated methods employing infrared technology to detect traces of the products of oxidation and combustion. The advantages and disadvantages of various gases employed as indicator gases for the early detection of heatings and fires are discussed, and recommendations are made in this regard. The operation of a modern infrared carbon monoxide detection system is described, and the differences in operation and application of telemetric systems, tube-bundle systems, and up cast-shaft monitors are discussed In conclusion, some indication is given of the capital outlay required for typical early-detection systems.

Jan 1, 1981

By I. Wayland

Value added blasting is a process methodology that links tasks and processes, with the aim to improve/enhance the technical application of explosives technology and initiating systems, resulting in improved output. The phases and steps of a typical value added blasting intervention are discussed in this paper. Each step having distinct purposes, principles and methodology. The underlying philosophies and process steps of the programme are described for each step. This paper gives an account of projects that have been completed in two Anglo American Gold Mines. This will include a description of the projects that were conducted at Vaal Reefs 8 Shaft and Western Deep Levels South Mine covering: ? The need for blasting improvements ? The approach that was followed ? The result of the programme.

Jan 1, 1999

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 B. Kenealy

A typical deep shaft is President Steyn No. 2 in the Free State, where 9 tonnes of ore are hoisted at about 15 metres per second from 2378 metres below surface. The skips and attachments each weigh 7 tonnes and they are connected by 43 tonnes of rope, so that to hoist the 9 tonnes of payload, a total of 66 tonnes is accelerated from stand still to 55 km/h for each cycle, using an average of 3185 kilowatts of power in the process. The cycle time for the hoisting is 3.22 minutes. The peak power consumption is 6954 kilowatts, which determines the size of the motor used. Is this the right approach? Are larger skips moving at higher speeds the answer? Is there another way?

Jan 1, 1996

By O. Y. Ntrama

Lebowa Platinum Mines has been in operation since the late 1960s and is a relatively small producer compared to Anglo Platinum?s other operations. The mine has never had substantial capital investment to expand its production scale even though its resource base is estimated in excess of 100 years at current mining rates. It is forecast that the mine will become unprofitable after 2008 due to the workings of the ageing infrastructure, the Merensky Reef operations being further from the shafts, decrease in productivity and increase in operating costs. In order to reverse the forecast decline in operational inefficiencies and profitability the replacement of the Merensky Reef operations at Vertical and UM2 shafts with the development of a 120 Ktpm Brakfontein Merensky Reef Mines is in progress. This paper covers the operational readiness framework developed from the control budget estimate and outlines an integrated business process adopted to ensure that the requirements of the investment proposal are met. The operational readiness framework, which addresses the transition process, will ensure that at operational start-up, all appropriate operating systems, procedures, information and legal requirements are in place, whereas the business integration process will aim to develop and sustain an organization with the appropriate infrastructure and workforce equipped with the necessary skills to meet Brakfontein?s requirement, and where possible embark on an optimized accelerated production initiative to ensure that the objectives of the investment proposal are sustained. Keywords: operational readiness, business integration, optimized accelerated production initiative, organizational development.

Jan 1, 2006

By G. J. Wright, M. J. Neale

As machines become more complex and vital to our way of life, any disturbance or failure of their proper functioning tends to have serious consequences. To prevent such failures, increasing attention is being paid to techniques for the monitoring of machinery condition or 'health'. Of the many methods available, examination of the lubricant and any particles it contains forms a basis for interpretation of the conditions of operation, and the rate and severity of degradation of the moving parts, in a machine. Many techniques of wear-debris analysis, such as spectrographic oil analysis and ferography, are available indicate the composition, shape, size, and concentration of contaminants in a lubricant. This paper reviews the important aspects of wear-debris analysis as an integral component of machinery condition monitoring, and gives an insight into the selection of appropriate techniques and the information that can be obtained from each.

Jan 1, 1987

By M. Pötsch, M. Blümel, E. A. Button

ABSTRACT: Stiffness controlled test procedures performed with servo-controlled shear systems are the most versatile for simulating the wide range of boundary conditions expected in nature. Examples of a function controlled procedure in addition to dilatation controlled procedures are discussed for different characteristic behaviours. ZUSAMMENFASSUNG: Steifigkeitskontrollierte Scherversuche mit servohydraulischer Steuerung eignen sich gut unterschiedliche Bettungen, wie auch in der Natur vorkommen, zu simulieren. Beispiele für spezielle Steuerungsfunktionen und dilatationsgesteuerte Prozeduren mit verschiedenen charakteristischen Eigenschaften werden diskutiert. RESUMÉ: La rigidité a commandé des méthodes d'essai exécutées avec les systèmes asservis de cisaillement sont la plus souple pour simuler l'éventail d'états de frontière prévus en nature. Des exemples d'un procédé commandé par fonction en plus des procédures commandées par dilatation sont discutés pour différents comportements caractéristiques.

Jan 1, 2003

By R. T. White

The usual figures quoted for water usage in South African gold mines are 1 ton of water used per ton of rock broken, which represents a consumption of 4000 litres of water every second. Owing to the limited sources under ground water, the high cost of surface-water supplies, and the environmental problems of effluent disposal, water IS recycled continuously for underground use. This paper reviews the various types of water treatment and why water needs to be treated. The uses of lime and some flocculants are considered, since much of the mine service water requires only simple neutralization and clarification. Where mining depths necessitate the installation of underground refrigeration plant, more stringent water requirements must be met, and where plant performance is to be maintained, the prevention of system scaling and corrosion is necessary. The families of chemicals added to provide such protection are outlined, together with a description of the mechanisms of control.

Jan 1, 1985

By R. B. MacGillivray

The No. 2 Seam at Van Dyks Drift Colliery was found to be made up of six easily recognizable bands or plies of differing qualities. Not only did the plies differ from one another in quality, but their thickness and quality varied laterally across the mine. The economic production of a Iow-ash blendcoking coal for supply to the Japanese Steel Mills called for the mining of different portions of the seam. The portions that could be extracted economically varied in thickness and position within the No. 2 Seam across the mine. A unique system of selective mining had to be developed involving the dispatch of two separate streams of coal out of the mine. Conventional American mechanized pillarand-stall mining was used, and the productivity was improved by the installation of twin conveyor belts into a double-header section. The method of grade control that was instituted to ensure efficient extraction of the available coal reserves is described.

Jan 1, 1985

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 U. C. Galimidi, J. M. Stewart, A. J. Van Rensburg

The effect of body movement on convective heat transfer from a man performing a block-stepping task was investigated experimentally by direct measurements of convective heat transfer. A series of experiments was conducted in which a nude man was required to stand at rest or to block step at 12 and 24 steps per minute. Wind speed, which was kept constant during each experiment, spanned the range 0,5 to 3,5 m/so Air temperature was kept constant at 43 °C in all the experiments. The results showed conclusively that the convective heat-transfer coefficient depends on the stepping rate. The effect of body motion can be regarded as being equivalent to an increase in the velocity of the free stream. The equivalent increase in air speed was found to be 0,36 and 0,77 m/s for 12 and 24 steps per minute respectively. Data from various sources, including the present study, indicate that wind speed should be increased by about 0,30,0,55, and 0,80 m/s to account for low, moderate, and vigorous body movements respectively. These findings are of direct relevance to the practical assessment of heat stress.

Jan 1, 1979

By Austin Whillier, Duncan Mitchell

The problem of heat stress underground in the gold mines is approached on the basis of the heat transfer between the human body and the underground environment. Experimental measurements of radiant and convective heat transfer and a theoretical calculation of maximum evaporative heat transfer enable the maximum cooling power of an environment to be calculated in terms of the dry-bulb and wet-bulb temperature, the mean radiant temperature, the wind speed and the barometric pressure. For most underground applications the cooling power can be expressed as a function of wet-bulb temperature and wind speed only. The relative importance of wind speed and wet-bulb temperature can be assessed: in working places where wind speed is low additional cooling of workmen can be achieved better by increased wind speed than by decreased wet-bulb temperature. The wet kata reading proves to be of limited value as an index of heat stress because environments with equal wet kata do not necessarily have the same cooling power. Finally, thermal equilibrium with the environment is possible when cooling power equals or exceeds the rate of metabolic heat generation. The rates of metabolic heat generation for various underground tasks are indicated.

By P. J. Lloyd

Society is fully justified in its concern about the environment, but that concern may, at present, be too uncritical It is, for instance, essential to establish that there is a valid environmental impact, and that there is truly a causal link between a human activity and an observed shift in environmental conditions. In establishing these, it inessential to recognize that scientific proof offers consistency, but that it can never provide completeness. Thus, no amount of scientific endeavour can ever prove that mitigation of the effects of human activity will be perfect. Society normally expresses its concern through legislation. The existing legislation in South Africa is reviewed, and it is found that [>legislation regarding water is probably too stringent to be effective, >legislation regarding air and land use is probably too lax, >all the environmental legislation is too fragmented to be efficient, and the Department of Environmental Affairs is hamstrung by inter-departmental rivalry. ] It is accordingly concluded that, if means are to be found for ensuring adequate mitigation of environmental impact in the face of ongoing economic development, it is necessary to establish a Judicial Commission on Environmental Affairs advised by, but given greater powers than, the departments currently active in environmental maters. This Commission should be charged with creating, perhaps over a decade, a body of legislation that would guide development while protecting the environment in its widest sense.

Jan 1, 1994

By J. Lamb

Project managers must juggle many aspects to bring their project in on time, on budget, and in accordance with the aims of the project owner. Whether the project is a mining feasibility study, a technology implementation or a construction project, it falls to the project manager and his or her team to deal with risk from two standpoints, which may be at odds with one another. First, a project team must deal with risks to the project itself - that is, risks to on-time, on-spec and on-budget delivery against the value promise made to the customer. Second, there is the management of risks within the subject matter of the project, undertaken on behalf of the customer. The project manager cannot dodge this responsibility; yet there is a tendency (particularly in smaller, in-house studies) to avoid digging too deep, possibly for fear of what may be uncovered! This paper investigates the responsibilities of project teams in regard to risk management and reporting. It examines ownership of project risk; the nature of risk management activities undertaken by the team during the course of a project; and outlines some controls to ensure that the two opposing arms of project risk are reconciled for the benefit of both the project team and the project owner.

Jan 1, 2007

By D. D. Hawat

The locations of potential reserves of chromite ores throughout the world are discussed. Reference is made to the marked changes in international trade in chromite ores during the past ten to fifteen years, and to the change in locality of the production of ferochromium aloys, which is curently largely carried out in the country of origin of the ores. The influence of these changes has been very profound in South Africa, which has the largest smelting capacity and the largest production of ferochromium aloys in the world. A proportion of South African ore is stil exported to meet the demands for the production of chromium chemicals and refractories, including a large tonnage of foundry sands. Ferochromium smelters in South Africa have a capacity of virtualy 1 Mt of aloy per annum. Nearly al this development has taken place since the introduction of the argon-oxygen decarburization (A.O.D.) process for the smelting of stainless steels. Formerly, expensive Iow-carbon ferochromium aloys were required as raw materials, but the AO.D. process, which is being used world wide, permits the use of high-carbon ferrochromium, the main product of the smelters in this country. The production in South Africa of chromium-containing corrosion- and heat-resistant steels is stil on a relatively smal scale, but serious atention is being paid to the exploitation of low-carbon weldable feritic chromium steel.

Jan 1, 1986

By H. Scott-Russell

Much of the technology and methodology extensively employed in current mining operations is in the mature phase of its lifecycle and, consequently, subject to the principle of diminishing returns. It is probable that future gains in productivity and safety of the magnitude essential for the sustained economic viability of the industry will be derived only from a determined technological development programme. The history of trackless mechanized mining, which represented a radical change in methodology in deep-level gold mines, is reviewed. The benefits and obstacles to the realization of the full potential are highlighted. Similarly, an overview is given of alternative mechanization developments in South Africa. In addition to the development and application of advanced technology, an envelope of operating parameters relevant to each methodology must be engineered to facilitate the site-specific selection of the most appropriate. Furthermore, a mechanism for the evaluation of cost effectiveness is essential to the decision-making process. The narrow, tabular orebodies of relatively low dip that are encountered in the South African hard-rock mining industry make the design and manufacture of a comprehensive range of stoping equipment extremely difficult. The machinery that has been available to date has demonstrated only limited site-specific success. The development of suitable machinery must necessarily be initiated and driven by the South African mining industry in collaboration with the major equipment manufacturers in the world.

Jan 1, 1993

By R. Hummel

In the quest to reduce overall costs and improve operating efficiency, the application of GPS based technology in open pit mining has evolved significantly in recent times. Venetia Mine has been leading the way in the De Beers group in the implementation of these systems and the realization of significant benefits from them. Following on from the successful results and the notable benefits obtained from the Wenco Truck Dispatching system and the Caterpillar CAES system on the loading and dozing equipment, Venetia has implemented the first fully functional and integrated GPS based drill monitoring system in southern Africa to its drilling operations. This paper elaborates on the concept of drill monitoring and how the vision for the application of the system at Venetia has developed and been implemented. The paper further describes the workflow involved, beginning with the initial test work done with SSI Kaltex and the Australian Drill Advisor system through to the final details of the integration of the Aquila system with the CATERPILLAR Computer Aided Earthmoving System (CAES) and the alliance with SandvikRock Tools. Most importantly, the paper details the benefits that are derived from drill monitoring and the use of the information generated by such a system. Venetia has pioneered the move towards smart partnerships and alliances with strategic suppliers within the De Beers group. The area of drilling, as the important start of the entire mining process, has been no exception and the final part of the paper covers how drill monitoring provides vitally important information that enables a supply partnership, to function cost-effectively and profitably for both parties involved. By having the type of accuracy, detail, validity and timeousness in the information being received as a result of the implementation of such a system, better management decisions can betaken, creating a more focused and efficient mining environment. In these times of increasing costs and reduced commodity prices, the mining industry will be required to continue pushing the boundaries on these technology applications in order to remain competitive.

Sep 1, 2001

By W. J. C. Pothas

This paper describes the state of the art in backfilling techniques used on East Driefontein Gold Mine. Areas covered are the preparation plant, the distribution plant, the pipeline network and finally placement techniques. The in-situ performance of placed backfill has been assessed by the Chamber of Mines Research Organization, and results to date will be shared. Details of the backfill expansion programme that will enable this facility to be made available to all working places are included. Benefits obtained by the introduction of backfilling are described, together with certain management aspects to be considered in the control of quality and quantity of support supplied via a pipeline.

Jan 1, 1988