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By M. N. James

The Fracture Research Group has been operating at the University of the Witwatersrand for some ten years and, in that period, has achieved a significant profile, both nationally and internationally, through its research publications, industrially-based technical reports, continuing short courses in engineering education, and co1Jferences. This paper outlines the activities of the Group over the past few years, emphasizing the research thrusts and the results that have been obtained, as well as highlighting areas of current and future research interest The capabilities of the Group in terms of equipment and expertise are also discussed briefly.

Jan 1, 1995

This paper details the preliminary design work carried out before and during the implementation of an extensive backfilling programme on Cooke 3 Shaft, Randfontein Estates Gold Mining Company (Witwatersrand) Limited. The design work is of relevance to any system utilizing a cementitious binder, and the quality control aspects are of particular significance. Problems associated with correlating laboratory results to actual field results are also briefly discussed.

Jan 1, 1988

By D. Mark, S. R. Hunneyball

The ongoing revision of the Respirable Dust Regulations (RDR) by the UK coal mining industry includes the introduction of personal exposure monitoring for underground mines, rather than the fixed point sampling of workplaces. The initial choice CIP10 personal respirable sampler, failed during the underground trials because of the transfer of large non-respirable particles to the respirable dust deposit under vibration from man-riding belts, and of adverse effects of high winds and high dust loading on the flowrate through the sampler. These effects were validated in laboratory simulations of these conditions. A cyclone-based personal sampler is showing promise as an alternative.

Jan 1, 2003

By J. O. Jensen

A method is described for the determination of cyanide in gold slurries, based on amperometry. The measured current is proportional to the concentration of cyanide, and is not effected by pH or by the concentration of oxygen in solution. It is also unaffected by other ions that may be present in gold-leaching solutions, including sulphide, thiocyanate, and thiosulphate. The current depends on the temperature, and an activation energy of 17,9 kJ/mol was determined Since the current is controlled by the mass transfer of cyanide to the anode, it depends on the conditions of agitation. In tests on an operational gold plant, slurry was pumped directly from the top of the leaching tank, through the measuring cell and back into the tank. The results indicate that the instrument is a promising alternative to the instruments currently available. The readings from the instrument remained in calibration for at least two days, showing that the instrument would need to be re-calibrated by the operating staff at regular periods.

Jan 1, 1994

By J. H. Viljoen, N. B. Strydom, J. S. Greyson, C. H. Van Graan

SYNOPSIS Bad eyesight and poor illumination can contribute to the occurrence of accidents in mines. As one part of a study of this problem, surveys of light intensities have been conducted in 19 gold mines. On 17 of the mines the surveys were on one underground level only, whilst in two of the mines more intensive surveys were conducted by measuring light intensities in all areas to determine any inter-mine variations between the levels of illumination. Readings of light intensity were taken underground at stations, tips, winches, stopes, conveyor belts, waiting places, pump stations, fitters' and boilermakers' workshops, ambulance rooms and in haulages. It is concluded that the average levels of illumination in South African gold mines are comparable with those reported in the literature for mines elsewhere. Standardisation of lighting conditions underground could eliminate inter- and intra-mine variation in illumination levels where they occur. A guide to mine illumination practice would assist such standardisation, and help increase the levels and effectiveness of illumination in mines. Some suggestions are made in this latter connection.

By G. P. L. van der Linde

EVERY OREBODY IS UNIQUE [ ] GEOLOGY AND MINERALIZATION DIFFERENT [ ]

Jan 1, 2005

By M. J. Nicol, P. D. Scott

The kinetics of the non-oxidative dissolution in acids ofthe iron sulphides FeS, Fe-FeS, and Fe9S10 were studied by the use of rotating-disc electrodes of the various compounds. It was found that the rates of dissolution vary by orders of magnitude with changes in surface potential. The dissolution rates depend on non-integral orders of hydrogen-ion concentration, which in turn vary with potential. A mechanism based on the following premises is proposed to explain the kinetics of dissolution of the iron sulphides. (I) Only an FeS compound that is exactly stoichiometric dissolves in accordance with the accepted theory of ionic charge transfer. (2) Any non-stoichiometric iron-deficient iron sulphides must be reduced to exactly stoichiometric FeS before spontaneous non-oxidative dissolution can occur. The dissolution of Fe.S1o and slightly iron-deficient FeS compounds under open-circuit conditions occurs only when an oxidation reaction (usually the oxidation of hydrogen sulphide to elemental sulphur) can provide the electrons necessary for the production of exactly stoichiometric FeS. The establishment of such a mixed-potential system is the reason for the induction period that occurs during the dissolution of pyrrhotites in acids.

Jan 1, 1979

By A. P. W. Briggs

Difficulties with the screening of large volumes of pulp to remove plus 600 /km material before the adsorption circuit and to retain plus 20-mesh carbon in the adsorption contactors have largely been solved, with the result that the plant can now handle its design throughput. The elution and electrowinning processes have been modified to simplify the circuit, but the regeneration of carbon remains unsatisfactory. The production of fine carbon in the plant can lead to increased gold losses, and this carbon must be collected and treated. Collection methods for fine carbon and some indications of the quantity of the carbon and its gold values are given.

Jan 1, 1983

By J. W. Latilla, J. J. van Wijk

In late 1997 a request was received to assist with determining the powered support unit (shield) load capacities for the planned 2 seam short wall. This project had a number of aspects which made it attractive to utilize numerical modelling in conjunction with other more conventional design tools in the design of the shields. Amongst these were: The 2 seam panels were to be laid out about 25 m below the previously short walled 4 seam, the 4 seam had in turn been over-mined by the 5 seam long wall, the proposed face height of the 2 seam short wall was 5.5 m while the 4 seam had been mined at 4 m. The top seam in the area (5 seam) had been mined at between 1.5 and 2.2 m high, the face conditions with about 95 m of broken material applying dead weight loading to the 2 to 4 seam inter-burden septum were hard to predict and cyclical loading due to the presence of strong sandstone bands in the 2 to 4 seam inter-burden. The basic thrust of the study was to take the known, and successful, situation (4 seam short wall) and carry out comparative modelling to enable prediction of likely 2 seam conditions. Some two dimensional aspects studied were: 5 m goaf hanging up behind shields, stresses in beams to determine likely first goaf roof span, stresses in cantilever beams to asses cyclical loading due to sandstone bands in the interburden being loaded by the overlying goaf and stresses on chain and crush pillars adjacent to the goaf edge. Three dimensional aspects that were investigated included: Load distribution along face for close goafing and 5 m goaf hang-up and load in a 1 m wide rib modelled in the position of the powered support units. From the modelling it was possible to determine the optimal shield leg capacity of the new 2 seam equipment. These outputs were used when drawing up the technical specifications for manufacture of the new equipment. The face was successfully commissioned in August 2002. Fin 1997, requête fut faite pour aider à la détermination des capacités de charge pour l’unité de soutènement mécanisée (bouclier) pour la couche 2 courte taille en projet. Certains aspects de ce projet le rendaient intéressant pour utiliser la modélisation numérique en même temps que d’autres méthodes conventionnelles pour la conception des boucliers. Parmi ces aspects se trouvaient : Les panneaux de la couche 2 devaient être placés environ 25 m au dessous de la couche 4 courte taille ; la couche 4 avait été remplacée par la couche 5 longue taille ; la hauteur de taille proposée pour la couche 2 courte taille était 5.5 m, tandis que la couche 4 avait été exploitée à 4 m. La couche supérieure de la région (couche 5) avait été exploitée entre 1.5 et 2.2 m de hauteur ; il était difficile de prédire les conditions de taille, avec environ 95m de matériaux cassés ajoutant une charge morte à la plaque de séparation entre les couches 2 et 4 et un chargement cyclique causé par des bandes de grès dans l’entre-fardeau 2-4. L’idée principale de l’étude fut de prendre la situation connue et réussie (couche 4 courte taille) et de faire une modélisation comparative pour prédire les conditions probables de la couche 2. Certains des aspects à double dimension qui furent étudiés étaient : Un accrochage de remblai de 5m derrière les boucliers ; contraintes dans les poutres pour déterminer le premier intervalle probable entre remblai et toit ; contraintes dans les poutres en porte-à-faux pour évaluer le chargement cyclique causé par les bandes de grès dans l’entre-fardeau qui est accablé par le remblai et les contraintes sur les piliers par chaîne et d’écrasement adjacents au bord du remblai. Aspects à trois dimensions qui furent étudiés : Distribution de la charge le long de la taille pour les remblais proches et l’accrochage de remblai de 5 m et la charge dans une nervure de 1 m de large modelée dans la position des unités de soutènement mécanisées. La modélisation a permis de déterminer la capacité de portée optimale du bouclier du dispositif nouveau pour la couche 2. Ces résultats furent utilisés pour dresser les spécifications techniques pour la fabrication de l’équipement nouveau. La taille fut commissionnée avec succès en août

Jan 1, 2003

By C. S. Erasmus, L. C. Woollacott

The distribution of gold loaded onto carbon particles from a carbon-in-pulp operation was measured by neutron activation analysis. The nature of the distribution is examined, and the implications for operating plants and CIP simulators are discussed.

Jan 1, 1992

By R. H. O?Connor, B. N. Soutar

The paper reviews the introduction 01mechanical shaft drilling into the sinking 01shafts in the Gold Fields Group. A comparison is made between the operating costs 01the drilling rig and those of conventional hand-held machines, and it is concluded that, despite certain disadvantages, mechanical drilling is preferable.

Jan 1, 1988

By J. H. Dalton

The paper reviews the effects of fast-neutron irradiation on the tensile properties of austenitic stainless steels at irradiation temperatures of less than 400°C, using, as an example, work carried out at Pelindaba on an AISI 316 type steel produced in South Africa. Damage produced in these steels at higher irradiation temperatures and fluences is also briefly discussed. The paper concludes with a discussion of some methods of overcoming or decreasing the effects of irradiation damage.

Jan 1, 1979

By P. R. Jamisch

The limitations of gold-mine evaluation by P. R. JANISCH, B.Sc. (Sur.) (Natal) (Visitor) Inherent uncertainty in the choice of parameter values places theoretical and practical limitations on the interpretation of a gold-mine valuation that are not necessarily removed by comparison of two valuations on the same assumptions. These limitations arise mainly in the estimates made of cost inflation and gold-price escalation, and lead to inconsistencies in the 'league table' method of investment analysis. The choice of discount rate is also critical in many cases. An approach to the overall problem that takes these limitations into account is suggested.

Jan 6, 1976

Two column flotation cells have been installed as single-stage rougher cleaners at Batu Hijau. The objective was to provide additional residence time in the cleaner circuit to maintain maximum recovery during high mill throughput and high feed grade periods. Installation of the columns has allowed the relatively coarse, well-liberated rougher concentrate and the relatively fine, low-grade scavenger concentrate to be treated separately, improving metallurgical performance in the cleaner circuit. Plant results show that the columns produce a high-grade concentrate at an average stage copper recovery of approximately 80 per cent. There is also indication of increases in both overall plant copper recovery and final concentrate copper grade. In addition, the operability and stability of the cleaner circuit has greatly improved.

Jan 1, 2007

By P. G. Henderson

Coalbrook Collieries has produced approximately 2 million tons of coal by retreat longwalling since April 1976. Strata control. support. stone intrusions. coal conveyance, and the inflow of goaf and water between the face supports have been the major operational problems experienced to date. The progressive percentage availability of the total system (moves between panels excluded) for the first three panels mined was 40 per cent. Satisfactory solutions have been evolved for these problems. and the availability in the present panel (fourth panel) has increased to approximately 60 per cent. It is envisaged that longwalling will become the most economical method of ensuring optimum heat values, greater recovery. and reduced geographic expansion. as well as safer roof conditions. at Coal brook.

Jan 1, 1980

"Chairman: Mr W. S. GALLAGHERRapporteur: Professor A. M. STARFIELDPapers:Long-term mine production scheduling by G. C. S. BurneAn application of linear programming to investment analysis by A. ErlandssonOptimizing medium-term operational plans for a group of copper mines by M. Splaine, D. C. Atkinson, W. Davison and L. SmithThe simulation of underground stoping and transport operations in gold mining by F. H. Touwen and N. C. JoughinProduction planning is a subject that lies at the interface between the computing centre and mine management. Discus¬sion during this session was thus largely concerned, directly or indirectly, with communication between computing and mining personnel, and as such was relevant to the symposium as a whole.Mr A. Weiss set the tone of this discussion by referring to `user-orientated systems'. He congratulated Mr Burne in this regard, pointing out that his long-term production scheduling program, as a computer system, was similar in approach to the manual system it replaced, and was therefore easily understood by planning engineers. He asked whether the schedule engineer had his 'hands on' the system, to which Mr Burne replied that the engineer did in fact spend several days running alternative schemes through the computer. Mr Weiss commented on the advantage of having terminals on site for this sort of engineer-computer interaction. He also commented on the flexibility of Mr Burne's approach to scheduling and how preferable this was to a one-step optimization package. This was brought home by a question from Mr H. D. Small: Mr Burne's program sometimes found it necessary to temporarily halt an advancing face, and he asked whether the logic of the program could be altered to avoid this (e.g. by suitably slowing down the rate of face advance). Mr Burne replied that it was in fact easier for the planning engineer to sort this problem out manually. The way in which the computer results were presented made it particularly simple for the production engineer to see how to avoid or remedy a stopped face.On the technical side, both Mr Weiss and Mr H. M. Wells questioned Mr Burne on the handling of grade control by his program. From answers by Mr Burne and his colleague Mr K. H. Thomson it emerged that a spot-check on grade every now and then was all that was necessary at Mufulira, and that the idea of actual grade control was more a question of short-term than of long-term planning."

Jan 1, 2014

By R Linares

For centuries, diamond's superlative properties have earned it a reputation as the 'dream' material for mankind in its search to create advanced applications. Until recently, this dream has been realized only in the use of diamond for gemstones and abrasive applications where several tons of diamonds are now used on an annual basis. The vision of having large, high quality diamond as part of a broad engineering tool-kit for many diverse high tech industries is now becoming a reality however, with the advent of early stage commercial availability of single crystal and poly crystalline CVD diamond.

Jan 1, 2010

By F. Botha

South Africa is amongst the 40 driest counties in the world, with extreme weather conditions and beset by both droughts and floods. Coupled with economic growth is an increased demand on water resources and, as with all other industrial developments, mining requires large volumes of water, which is likely to have an impact on the environment. Further to this, the mining industry also realizes that minerals are a non-renewable resource and the contribution to wealth creation from mineral extraction is not everlasting. It serves as an economic boost and careful planning is required to ensure that the legacy of mining is sustainable, and that some of the returns from mining provide continual economic and social prosperity.

Jan 1, 2012

By T. Flitton, R. Peattie

"The extreme depths and consequent expense of drilling and sampling the gold-bearing reefs of the Witwatersrand Basin have resulted in limited data being available for estimation of grade ahead of the mining face. There is, however, a wealth of information from mined-out areas of these deposits. This estimation challenge resulted in the development of a unique method of Mineral Resource estimation.AngloGold Ashanti (AGA) utilizes a technique termed macro cokriging (MCK), which allows for the integration of the limited advanced borehole data with the large chip sample data-sets from the previously mined-out areas by adopting a Bayesian geostatistical approach. The MCK process, in short, is the estimation of mixed support size data together with the application of four-parameter distribution models.The gold value estimation for the Carbon Leader Reef (CLR) on the AGA TauTona Mine is used in this paper as a case study of the process and to demonstrate the effectiveness of this technique through production reconciliation. The current method has been proven over the last 20 years and is now an established part of the Mineral Resource evaluation process within AGA.IntroductionOwing to the extreme depths of the goldbearing reefs at the AngloGold Ashanti (AGA) Witwatersrand operations and the prohibitive expense and time involved in drilling boreholes to the required depth, only limited drilling and sampling data is available ahead of the mining face. Whereas traditional estimation techniques are interpolative, within the Witwatersrand the estimation is primarily extrapolative, with the majority of the data being sourced from the mined-out areas. This significant challenge to estimation resulted in the development of a unique method of Mineral Resource estimation and evaluation."

Jan 1, 2016

By D. F. Malan, J. C. Esterhuyse

"Mining in the Carletonville area of the Witwatersrand Basin predates 1934. Owing to the depletion of higher grade ore, the current activities focus increasingly on the extraction of lower grade secondary reefs as well as remnant extraction. Of particular interest is multi-reef remnant extraction. Numerical modelling was conducted to investigate some rock engineering aspects of remnants being understoped on a secondary reef horizon. An analysis of the stress evolution in the middling between two reef horizons indicated that a zone of high major and low minor principal stress develops between the two reefs. This indicates a high risk of violent shear failure. Some pillars were nevertheless successfully understoped in the past and a study was conducted to better understand this phenomenon. An ’extended’ energy release rate concept introduced by Napier and Malan (2014) proved to be useful for investigating this problem. It was found that bedding planes and lithology appears to play a role in the stable dissipation of energy in multi-reef remnant geometries. The study indicated that the stope convergence and the various energy components are affected by the presence, position, and properties of a bedding plane. The energy solutions are complex and sometimes counterintuitive. Care should be exercised when modelling specific cases. The modelling was nevertheless valuable as it indicated that energy dissipated on weak layers may reduce the risk of violent failure in a multi-reef mining scenario. Additional work is required to investigate if crushing on the reef plane plays a prominent role when mining these remnants. IntroductionTo extend the lives of the Witwatersrand gold mines, work is being conducted to include a larger number of remnants and pillars in the reserve base of the mines. According to Jager and Ryder (1999), a remnant is an unmined block of ground surrounded by extensive mining. Remnants are typically left because of adverse or difficult mining conditions caused by geological structures, poor ground conditions, low grade, or rockburst damage (Durrheim, 1997). In contrast, pillars are typically the result of rock engineering designs to control energy release rates (ERR) and seismicity. During the early 1900s, remnants formed by the practice of scattered mining layouts had a significant effect on seismicity. Numerous task teams were appointed during this period. As the industry expanded, the severity of rockbursting increased and the research was formalized after the 1960s. Various recommendations were made and many of these are still used as best practice today (e.g. Jager and Ryder, 1999)."

Dec 1, 2018