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By B. Steyn

AngloGold Ashanti?s Obuasi Mine, in Ashanti Province, Ghana, operates a plant utilizing bacterial oxidation technology. The mineralization consists predominately of arsenopyrite with gold associated in the sulphides. The plant was commissioned in 1994, at that time was the largest BIOX® plant in the world, and has been operated by AngloGold Ashanti since 2004. The constraints identified in the plantwere the flotation capacity, BIOX® feed size and disruptions to the BIOX® process. This paper focuses on the practical steps that were followed in order to increase the recovery of the plant. The original plant design was based on a head grade of 10 g/t and an overall recovery of 86.5%. In 2007 the plant was operating at an overall recovery of 79.2% at a head grade of 5.6 g/t and this has improved to 80.6% at a head grade of 5.8 g/t during the last quarter of 2008. Additional improvement to 81.5% are expected by the end of April 2009. Improvements that have been implemented include: ?Replacement of the regrind mill ?Installation of additional float capacity ?Installation of a scavenging circuit ?Installation of a complete water treatment plant. In addition we have focused on the effect of the water circuit on the BIOX® process and the steps involved in correcting this problem. The water circuit was originally designed as an open circuit and through environmental considerations the circuit was closed towards the end of 2007. The bacteria in the BIOX® are particularly sensitive to cyanide and cannot tolerate levels above 0.05ppm (free cyanide), this required extensive modifications to the water circuit. The plant improvement project is ongoing and the current scope of work should be complete by the end of April 2009. Further research and development work is being planned, which includes a ?white rot bacteria? that can consume the preg-robbing carbon and oxidize the sulphide in a single pass.

Jan 1, 2009

By L. Kühnel, H. Lieberwirth

Confined bed comminution in High Pressure Grinding Rollers (HPGR) and Vertical Roller Mills (VRM) is gaining substantial attention in many applications. Previously used mainly for milling coal or construction materials, HPGR and VRM have started to complement or even replace tumbling mills in ore beneficiation. Materials like coal or clinker are relatively homogenous, however, in comparison to metal ores and wall rocks. This characteristic poses a new challenge to the confined bed comminution but also an opportunity. Fuerstenau and Abouzeid have investigated the selectivity in comminution of a mixture of particles of different strength in a particle bed. The median particle size and particle size distribution (PSD) of the two constituents used were kept constant. Only the proportion of the two constituents was modified. The competence of a material is, however, also a function of particle size. Smaller particles tend to be more competent than larger ones of the same material. If selective comminution is applied on ores, this size influence has to be understood. The paper presents research results on this topic based on experimental investigations with model materials as well as with natural particles, which were stressed in a piston-die press. It appeared that the comminution result depends substantially on the material characteristics and the composition of the mixture. Conclusions will be drawn for the application in future applications of selective comminution in mineral processing. Keywords: Confined bed comminution, HPGR, VRM, piston die press, particle size

Jan 1, 2020

By A. Esterhuizen

Since 2005 Two Rivers Platinum Mine has set out on an initiative to actively monitor and control ground conditions on a daily basis, by making use of borehole cameras and pro-actively amending the support and mining strategies based on day-to-day observations of the hangingwall conditions. Today the borehole camera observations form part of the Rock Engineering Department?s daily function, and the size and frequency of falls of ground and ensuing accident rates have been drastically reduced since implementation of the system. The Two Rivers Platinum fall-of-ground management system aims to support 100% of the possible fallout thickness, based on ongoing data gathering and interpretation, thereby ensuring safety and limiting support cost.

Jan 1, 2014

By Y. Lizotte

This paper describes the design and implementation of the dispatching system at LAB Chrysotile Inc.'s Black Lake Mine Operation, Quebec, Canada. The initial system uses a computer in a passive role, to record and display information in ongoing operations. Simulation studies were undertaken at McGill University to assess various heuristic dispatching rules which can be program- med and inserted into the dispatching system. The computer can then suggest to the operator where a truck should be sent to maximize productivity or improve fleet efficiency. The study stresses the importance of considering the effects of implementing computerized systems on those individuals who must use these systems in their daily work. The roles of individuals from the industry and the university in this joint project are also highlighted.

Jan 1, 1987

By A. W. S. Schumann

G. H. HENDERSON INTRODUCTION It is a pleasure to have read Mr Schuman's wide ranging and highly informative paper and also to congratulate him. Before proceeding to give views on the use and preservation of coal in South Africa, it is perhaps apposite to look at the South African scene on the world canvas. Mr Schuman's figures in his Table I are highly revealing. The Table shows expected consumption, export and import demand in the year 1980 by the continents of the world. The Republic of South Africa is shown as one of only four exporting countries at that date, although in the interim, Australia has become an exporter and will continue to grow as an exporter of coal. Huge fields have been proved in recent years. There is reason to think that for some years, coal and its economical uses have been under-estimated. The importation of oil carries a constant question mark and the exciting possibilities expressed in the uses of Dranium a decade ago for power generation, appear to have met with some setback. Present indications are that breederreactors will be delayed until about 1990. The capital cost of such reactors, too, is enormous. By 1980 it has been estimated that 20 per cent of the energy required by the leading ten nations of the world will come from nuclear power, but 80 per cent would then remain for fossil fuels and hydro generation. COAL DEMAND AND USAGE It is of interest to record that coal production in all the countries of Europe has declined markedly in the last 25 years. This is due to competition from oil, gas and nuclear power and also for sociological reasons; but there are signs that efforts will be made to resuscitate, at least in some measure, the mining of coking coals for which there is a strong and growing demand. Possibly all hard coal now mined in Germany has coking properties and that country is self-sufficient in this commodity. Germany might perhaps consider selling coking coal to her neighbours and importing additional coal for power-raising purposes. It has been frequently stated in American publications that the coal reserves of the D.S.A. are sufficient for 1 000 years. What that means, I do not know, but it is at least an indication that America has huge reserves of coal. Domestic and export demand in the U.S.A. in 1968 exceeded production for the first time. In 1969, the United States' output amounted to some 556 million tons, an increase of less than 2 per cent on the previous year. The output achieved fell short of demand, domestic and export, by more than 7 000 000 tons. This has caused and is continuing to cause anxiety in the U.S.A. In many countries young men for a number of reasons, largely environmental and social, are not coming forward in sufficient numbers for mining requirements and the same pattern has revealed itself in the Republic. This is, indeed, alarming because mining men in large numbers will be required to meet the estimated tonnage requirements set out in the following Table: It is difficult to visualise the replacement of these coal requirements either by oil or by nuclear fuels. The coal must be mined and men are required for the purpose. Unless a greater section of the population is allowed to participate in the more responsible aspects of mining, there is a serious likelihood that demand will not be matched by output. In addition to local demand, a lively export trade is possible. Exports are dependent on the future capacity of the South African Railways and Harbours and on Government policy. An export figure of 10000000 tons per year during the decade can be visualised and this figure would raise total estimated sales production to a figure of over 100 000 000 tons in 1980. At this point, it is necessary to examine the desirability or otherwise of exporting coal. How much coal

Jan 11, 1970

Mixed integer programming (MIP) has been used for optimizing production schedules of mines since the 1960s and is recognized a shaving significant potential for optimizing production scheduling problems for both surface and underground mining. The major problem in long-term production scheduling for underground orebodies generally relate to the large number of variables needed to formulate a MIP model, which makes it too complex to solve. As the number of variables in the model increase, solution times are known to increase at an exponential rate. In many instances the more extensive use of MIP models has been limited due to excessive solution times.

Jan 1, 2010

By H. Laitala, M. Lampi

Metso Outotec has developed a wide range of solvent-extraction technologies over decades and has introduced Metso Outotec VSF®X solvent-extraction plant. Standardized and modularized, Metso Outotec VSFX Plant provides a novel way to design, manufacture, transport, install, operate, and maintain solvent-extraction plants far better than in the past with highly sustainable and safe methods. For the customer, this means fast-track projects with savings in means of time, costs, quality, and operation. Sicomines and Metso Outotec have together implemented and commissioned a modern and efficient copper solvent-extraction plant. Plant commissioning and ramp up of the plant were fast and the plant is now operating efficiently. This paper presents Sicomines’ VSFX copper solvent-extraction project and gives a sight into operating figures for the plant.

Jan 1, 2023

By A. M. Thyer

Throughout the history of mining, underground fires or explosions have killed many hundreds or thousands of people. Fortunately, the safety record has gradually improved as a result of many people’s work on improving safety standards and work practices. However, fire and explosion still remains a threat in many situations. As a result the UK Mines Inspectorate commissioned a project to study materials used underground and to develop a fire/explosion risk assessment system. Such a system has been developed, following the study of incidents, specified fire resistance criteria, and fire safety practices. The final methodology uses a series of check sheets to identify potential fuels and ignition sources, preventative measures, fire/explosion mitigation systems, and items for inclusion in emergency plans.

Jan 1, 2003

By E. Spicer

X-Ray diffraction (XRD) provides useful information about the composition of an ore sample in terms of quantification of crystalline phases and amorphous content. The use of new, fast detection systems in XRD creates the opportunity to use this technique in modern process control. In the analysis of heavy mineral sands, XRD can identify the main mineral phases, such as ilmenite FeTiO3, rutile TiO2, Zircon ZrSiO4and quartz SiO2, and any other minor components present, such as anatase TiO2, magnetite Fe3O4, haematite Fe2O3or monazite (Ce, REE)PO4. Quantitative analysis is possible by various classical methods such as straight line or polynomial calibration with standards, but modern quantification analysis techniques such as Rietveld analysis (Bish and Howard, 1988) are attractive alternatives, as they do not require any standards or monitors. These methods offer impressive accuracy and speed of analysis. The Rietveld method compares calculated versus experimentally derived X-ray powder diffraction patterns for the sum of all crystalline phases. Another analysis technique offering great benefit to mining industries is cluster analysis. Enormous amounts of XRD measurement data are generated during the process control and material evaluation. New ways of handling such vast amounts of data are required to produce meaningful information for the end users. Cluster analysis greatly simplifies the analysis of a large amount of data from different processes or different raw materials, and automatically sorts closely related scans of an experiment into clusters and marks the most representative scan of each cluster as well as outlying patterns. The use of cluster analysis to evaluate the XRD data allows fast and reliable tracking of the process. It is the most economical procedure to have automatic data evaluation without involving any dedicated personnel in the process. Details of the techniques used, sample optimization methodologies, results, data precision and limitations will be discussed. The approach has potential as a relatively inexpensive, reliable tool, useful in the characterization of heavy minerals sand materials.

Jan 1, 2007

By I. Serepa, N. C. Steenkamp

Investigations were conducted to determine the condition and stability of the existing decline at amine in the Kalahari Manganese Field, Northern Cape Province, South Africa. During the inspection of the decline, voids were identified behind the concrete lining on the hangingwall and sidewalls over a total linear distance of 230 m. The voids did not provide confinement and, as a result, self-mining was occurring behind the lining. Water was flowing into the decline, over a total linear distance of 100 m, at areas where the decline intersected incompetent rock units, causing softening of the concrete lining and deterioration of the surrounding rock mass. Further damage to the concrete lining was caused by expansion and contraction of the wet red clay unit. Remedial work comprised void filling and water sealing to prevent further deterioration of the decline and ensure that it remained operable for the remainder of the life of mine. Void filling was accomplished by drilling rows of holes along the decline to access the voids and filling the voids with foam. This was followed by the sealing with polymer fluids. Telescopic pipes were also installed to allow water to drain off. A visual inspection was conducted and check-holes were drilled to assess the quality of the remedial work. The void filling material had penetrated cracks in the concrete lining, and areas where voids were intersected by check-holes were re-filled. Additional holes were drilled to re-seal areas that were still wet. The remedial work was completed successfully, as all voids were filled and stability achieved without compromising the concrete lining. The ingress of groundwater was also reduced to some residual dampness.

Mar 2, 2022

By K. J. Kruger

Aluminium alloys have gained popularity in many industries due to their high strength and low weight. One shortcoming of aluminium alloys is their poor resistance to abrasion and erosion wear compared to materials such as stainless steels. In this project, aluminium alloy 2014 (AA2014) was coated with a 1.5 mm thick laser-deposited layer composed of silicon, copper, and aluminium with the aim of increasing the wear resistance. The amount of silicon, copper, and aluminium added to each sample was determined by a mixtures model. It was discovered that the Al-Cu system is very sensitive to silicon additions and that wear resistance depends on the primary phase to solidify as well as on the final phase distribution. Two primary phases were identified; alpha aluminium and theta intermetallic. It was observed that the clad layer increases both the hardness and wear resistance of AA2014, and that the material solidifying as primary alpha aluminium displayed a lower hardness but higher wear resistance than the samples containing primary theta phase. All clad layers performed better in terms of wear resistance than the unclad samples. The knowledge gained and principles used in this project could be applied to many other aluminium alloys.

Jan 1, 2014

By C. C. Pretorius, S. Ramjee, R. J. Mostert

The study investigates the effect of prior corrosive exposure on crack growth resistance behaviour of thin sheet (3 mm thick) aluminium alloy 2024-T3 at slow strain rates. Compact tension specimens were exposed to standard corrosive environments that simulate accelerated atmospheric corrosion attack. Two corrosive environments were considered – an exfoliation corrosion (EXCO) solution and a 3.5 wt% sodium chloride solution. The unloading compliance R-curves of the two-hour EXCO-exposed specimens revealed a significant degradation of approximately 11% in the crack growth resistance behaviour (Kc_e values) compared to the baseline (air-exposed) values. Furthermore, secondary intergranular crack formation was also revealed in the plastic zone ahead of, and adjacent to, the crack tip of these specimens; which formed during the crack growth resistance loading. It is postulated that the observed degradation of the Kc_e values of the EXCO-exposed material is due to hydrogen embrittlement since the exposure times for the EXCO evaluation were limited to ensure that uniform corrosion dominated; that is, significant penetration of corrosion damage and pitting due to localized corrosive attack did not occur. The sodium chloride-exposed specimens revealed a similar degradation (13%) after 24 hours exposure. However, slight intergranular corrosive attack and isolated pitting were observed on the exposed surfaces prior to crack growth resistance loading, resulting in notch effects that could assist in crack growth. Pitting and intergranular corrosion were, however, not observed at the pre-crack tip. The relative contributions of the notch effects and the hydrogen embrittlement during the degradation of the KR performance are, therefore, unclear.

Apr 1, 2021

By F. H. Guise-Brown

Raise-boring experiences in the gold mines of the Anglo American Corporation Group by J. W. WILSON and P. C. GRAHAM Published in the Journal, October, 1972. Discussion by F. H. Guise-Brown., B.Sc. (Min. Eng.) (Member) INTRODUCTION Messrs J. W. Wilson and P. C. Graham are to be congratulated on an excellent paper containing several thought-provoking remarks. The concept of allocating a machine and equipment valued initially at some R300 000 on an experimental basis is courageous, and the results obtained could be of interest to the mining industry as a whole. The Gold Fields of S.A. Group approached this problem differently. In pioneering the start of this work in South African gold mines, they considered that expenditure of this magnitude would be warranted only if the proposition was viable right from the start. To this end, a Robbins R41 was purchased expressly to assist in the duplication of part of the No. 1 shaft system of the Doomfontein Gold Mine. Mr M. J. Koortsl has summed up the initial results of this work and given some preliminary costing, but inflation since that period has made these figures somewhat out of date.

Jan 10, 1972

By Q. Fu, Q. Wang, L. G. Wen, M. X. Jia, J. J. Zhao, J. W. Zhou

The BGRIMM process mineralogy analyser (BPMA) is a new automated mineralogy software platform developed in China. This system consists of the BPMA software platform, controlling a combination of commercially available scanning electron microscopy (SEM) and energy dispersive Xray spectrometry (EDS). The BPMA software controls SEM and EDS through their application programming interfaces, to form an auto-SEM and EDS system that automatically acquires BSE images and X-ray spectra, respectively, and classifies minerals by spectrum-matching. After automated measurement and mineral identification, various quantitative process mineralogical data (e.g., mineral composition, mineral abundance, mineral liberation and intergrowth relationships, mineral associations, particle and grain sizes, particle density distributions, calculated assay, elemental deportments, mineral grade recovery and elemental grade recovery, etc.) would be calculated quickly, accurately and automatically. The BPMA could be used for ore characterisation as a new advanced automated mineralogy technology. Keywords: BSE image; X-ray spectrum; automated mineral identification; quantitative mineralogical investigation; automated mineralogy

Jan 1, 2020

By A. Rahmanab, A. Torpy, M. I. Pownceby, M. N. Zaman, N. Haque, W. Bruckard, J. Tardio

Ilmenite is the principal feedstock for producing TiO2 - used in paints, plastics and paper and the production of Ti metal. The Brahmaputra River system in Bangladesh represents a potentially new source of ilmenite concentrated within sandbar placer deposits and the current study presents results from beneficiation and characterisation studies conducted on Brahmaputra River Fe-Ti oxides. Characteristic of fluvial systems, the ilmenite concentration is low (~0.5 wt-%), however extensive annual dredging for waterway navigation provides the economic impetus to recover saleable ilmenite. The Fe-Ti oxide suite derived from magnetic fractionation comprises homogeneous ilmenite, titanohematite and hematite, although many grains exhibit complex exsolution within the (Ilm-Hem)ss series. The textural variability results in difficulty generating a pure ilmenite feedstock with the bulk concentrate typically being low in TiO2, containing 31.0 wt-%TiO2 and 62.7 wt-% (Fe2O3). Results are interpreted via an analysis of the implications for producing a commercial-grade ilmenite concentrate suitable for TiO2 production. Keywords: Ilmenite, titanohematite, Fe-Ti oxide exsolution, TiO2 production

Jan 1, 2020

By E. Pothas, P. R. Jochens, L. B. McRae, D. D. Howat

Discussion H. J. S. Kriek*: During 1956 Iscor became interested in the acid smelting in a blast furnace of siliceous ores containing 15 per cent silica. This interest was as a result of the successful acid smelting in Germany at a CaO/SiO2-ratio of between 0.4 and 0.8. Acid smelting can become an economic proposition due to a reduction in slag volume accompanied by a lowering of the coke rate. Paschke and Hannel1 found that a free flowing slag (i.e. viscosities of less than two poise) would not be obtained at C/S-ratios lower than 0.82 and that the addition of 3 to 4 per cent alkalies became necessary. In titanium bearing slags it was established that maximum fluidity is obtained with 10 per cent TiO2. Acid smelting resulted in increased sulphur pickup with decreasing O/S-ratio and desulphurization with soda-ash outside the blast furnace was necessary. At Iscor Mr B. B. Segal established that, for slags with (CaO+MgO)/SiO2-ratios of 0.5, 0.6 and 0.7, the addition of alkalies and TiO2 resulted in a substantial decrease in melting point and also of viscosity. At a (CaO+ MgO)/ ratio of 0.53 the addition of 10 per cent TiO2 is as effective as the addition of 3.75 per cent alkalies. This means that a blast furnace can be run without the addition of alkalies and consequently the detrimental effect of alkalies on the lining can be avoided; also that fluid slags with 5 to 15 per cent MgO and 8 to 10 per cent Al203 can be obtained with 10 per cent TiO present. (CaO+ MgO)/SiO2-ratios smaller than 0.5 the addition of titania resulted in a decrease in melting point and also in an increase in viscosity. In ceramic crucibles the slag did not become more viscous with time but thickened appreciably when held in graphite crucibles. No titanium carbonitride could be detected and only Ti20a was found. Prof Howat also did not obtain the TiC-TiN solid solution and therefore it appears that the thickening of the slag is not solely due to the formation of the titanium carbonitrides. This is in agreement with the work of Michailov and Belyakova2 who found that TiO2 decreased the viscosity of acid slags and increased the viscosity of basic slags; that titanium sesquioxide (Ti203) and titanium monoxide (TiO) increased the viscosity of both acid and basic slags and that titanium carbide, which is found in larger amounts in basic slags than in acid slags, considerably increases the viscosity of both acid and basic slags. Patzak et al3 describes the following oxygen deficient titanias, viz Ti2O, TiO, Ti203, Ti3O5, Ti4O7, Ti5O9, Ti6O11- Ti10O9,Ti7O13,Ti8O15 and Ti9O17. Until about 1959 a fair amount of data was available on the viscosity of normal slags to which titania was added2, 4, 5, 6, 7, 8, 9. At Iscor an electromagnetic viscometer based on the viscometer developed by Bockris10 was built. Progress was very slow as our main attention was centred around problems associated with the operation of the Rotor process. During 1962 and 1963 two papers containing fundamental work on the viscosities of slags in the systems CaO-SiO2-TiO211 and CaO-SiO2-TiO2 at 0 per cent A1203, 10 per cent Al203 and 20 per cent Al20312 appeared. The work of Ross and Ohno obviated the necessity of any further work by Iscor on the viscosity of blast furnace slags containing titania. Ross gave the following optimum compositions for blast furnace slags containing titania. Titania % Lime % Silica % Lime/Silica-ratio 20 30-42 38-50 0.6-1.10 30 27-36 34-43 0.63-1.06 40 24-32 28-36 0.66-1.14 The optimum temperature is 1,500°C because at this temperature the largest workable composition range exists. Higher temperatures result in narrower optimum composition ranges and in increased rates of thickening. The factors affecting the rate of thickening were also investigated by Ross and Ohno, as the main problem with slags containing titania is not finding compositions which are fluid at operating temperatures but the thickening due to a lack of oxygen. With these slags when there is insufficient oxygen to co-ordinate each silicon atom with its own individual shell of four oxygen ions, some sharing of oxygen ions must occur, resulting in the formation of large silicate ions and a rise in viscosity. The formation of oxygen deficient titania can be prevented as long as iron oxide or manganese oxide remain in the liquid slag. Iwase13 and also Viens, Camp bell and Rogers14 obtained in the experimental smelting of ilmenite ores fluid slags with more than 3 to 5 per cent manganese oxide and ferrous oxide in the slags. It appears that titaniferous ores can be smelted in blast furnaces under the following conditions: (1) Acid slag operation, i.e. at C/S-ratios from O.6-1.0. (2) Dolomite can be used as a flux as MgO is a network modifier. (3) The Al2O3-content must be less than 15 per cent as alumina promotes thickening of the slag and decreases the optimum composition range. (4) The hearth temperature must not exceed 1,500°C. According to Ross a definite amount of energy is required for each ton of iron produced and in order to increase production an increase in heat

Jan 6, 1969

By M. A. Mahboob, T. Celik, B. Genc, I. Atif, S. Ali

"Mapping of hydrothermally altered areas, which are usually associated with mineralization, is essential in mineral exploration. In this research, open source reflectance spectroscopy data from the multispectral moderate-resolution Landsat 8 satellite was used to map altered rocks in the Gauteng and Mpumalanga provinces of South Africa. The unique spectral reflectance and absorption characteristics of remotely sensed Landsat data in the visible, near-infrared (NIR), shortwave-infrared (SWIR) and thermal infrared (TIR) regions of the electromagnetic spectrum were used in different digital image processing techniques. The band ratios (red/blue, SWIR 2/NIR, SWIR 1/NIR), spectral band combinations (Kaufmann ratio, Sabins ratio) and principal component analysis (Crosta technique) were applied to efficiently and successfully map hydrothermal alteration minerals. The results showed that the combination of spectral bands and the principal component analysis method is effective in delineating mineral alteration through remotely sensed satellite data. The validation of results by using the published mineral maps of the Council for Geoscience South Africa showed a good relationship with the identified zones of mineralization. The methodology developed in this study is cost-effective and time-saving, and can be applied to inaccessible and/or new areas with limited ground-based knowledge to obtain reliable and up-to-date mineral information.IntroductionMany developing nations depend on exploration and exploitation of mineral resources to sustain their economic growth. Usually, the traditional mineral exploration techniques require enormous finances, prolonged time, and tremendous manpower, particularly in areas that are not easily reachable (Maduaka, 2014). Furthermore, mineral exploration required state-of-the-art techniques and expertise along with geological, geochemical, and geophysical datasets, which may not be easily available or may be lacking where access is problematic (Kaiser et al., 2002; Bemis et al., 2014). Modern remote sensing technology has proved to be one of the highly efficient and robust techniques used for mineral exploration. The use of remote sensing satellite images for geological mapping and mineral exploration usually involves studying the physicochemical properties of rocks and weathering soils, such as mineralogy, landforms, geochemical signatures, and the spatiall distribution of lineaments (Bhattacharya et al., 2012)."

Mar 1, 2019

By D. -H. Park, G. -j. Kim, Y. -J. Park, C. -S. Hong, S. -Y. Choo

To evaluate the quantitative tunnel behavior influenced by characteristics of discontinuity, this pa-per executes the parametric study using 2 and 3-dimensional DEM analysis. First of all, this study finds that displacement and the stress of shortcrete are proportioned to frequency of joint and rockbolt axial force is adversely proportioned too. Secondly, it is found that the most sensitive in-put parameter used in Barton-Bandis(BB) model is residual friction angle. Finally, when joint sets are encountered at tunnel excavation face, to identify the most critical joint orientation is very crucial for a stability of tunnel. La thèse a pour but d’étudier les influences sur la stabilité du tunnel, au niveau du réseau de la discontinuité et de la valeur de sa nature aquis par le projet récemment exécuté en vue de mener à l’analyse quantitative de cette stabilité, en appliquant chaque différent paramètre comme la fréquence de diaclase, la constante de résistance des modèles de Barton-Bandis(BB) ainsi que la relation entre le sens d’excavation du tunnel et le réseau de diaclase en 3 dimensions. En fait, cette étude nous a montré que la fréquence de diaclase s’accroît proportionnellement au déplacement et à la contrainte du béton projeté. L’angle de friction résiduel s’est montré le plus sensible à la stabilité du tunnel parmi les modèles de BB. Aussi à travers l’analyse à 3 dimensions, il s’est vérifié que si l’angle de pente du groupe de diaclase est horizontal entre l’axe du tunnel et la direction, il donne une influence importante sur le comportement du tunnel. En particulier, l’influence était la plus importante sur un fond rocheux dont la diaclase horizontale est grande. Um das quantitative Verhalten des Tunnels zu bewerten, eroertert dieses Papier eine parametrische Studie mit Hilfe der DEM Analyse. Auch wird hier eine zweidimensionale Analyse von Ver-bindungen verschiedener Frequenzen in der Gesteinsmasse, eine sensitive Analyse von allen der im Barton-Bandis-Modell (BB) genutzten Parameter und eine Dreidimensional-Analyse mit ver-schiedenen dreidimensionalen geometrischen Veteilungen von Verbindungen ausgefuehrt. Erstens: Die Studie findet heraus, dass Vedraengung und Druck im Shortcrete proportional zur Frequenz von Verbindungen und Axialkraft der Steinbolzen antiproportinal ist. Zweitens: Es wird herausge-funden, dass die am meisten Sensitiven der im BB-Modell angewendeten Eingaben die am Ende uebriggebliebenen Reibungswinkel sind. Und schliesslich wird herausgefunden, dass wenn Ver-bindungsteile an der Tunnelaushoelungsoberflaeche ausgemacht werden, fuer die Tunnelstabiltaet die Identifikation der meist kritischen Verbindungsorientierung sehr bedeutungsvoll.

Jan 1, 2003

By F. H. Deist, H. D. Small, J. D. Austin, L. F. Duvel

The development and application of a computer system to aid in the planning of production in mines by F. H. DEIST, L. F. DUVEL, J. D. AUSTIN, and H. D. SMALL Published in the Journal, December 1972. Discussion by J. W. WILSON and R. W. HAZELL Although the Mine Planning Simulation Programme was originally developed as an aid to coal-mine planning, its extreme flexibility has enabled us to simulate gold-mine planning with equal facility. The initial application of the Mine Planning Simulation Model was in a small area of a large Free State gold mine where the primary aim was to assess the applicability of the programme to the gold-mining situation.

Jan 12, 1972

By D. Savile Davis

D. Savile Davis* (Member): The members of the Chamber of Mines Research Laboratories, headed by Dr Cook, indeed deserve all the plaudits that have been given for the original conception of the rock-cutter, and for the research work that has gone into designing the equipment now being tested. Underground trials with the rock-cutting machines at the Doornfontein Gold Mining Company Limited have been encouraging to the extent that 29 square fathoms of rock have been cut in the past three months with two modified prototype machines. Both the hangingwalI condition of the stope and the control of stoping width have been excellent. So far, however, the rate of production has been too slow and does not compare with conventional stoping methods, due firstly to the time-consuming operation of moving the machine forward and resetting it in its next cutting section and secondly to mechanical defects. Although great strides have been made in improving the tungsten carbide cutting tool, further progress is dependent upon engineering development in the design of a more reliable and versatile machine within economic limits. Commenting briefly on the experiments that have been carried out on the Gold Fields mines, the rock-cutter, when used at the Luipaards Vlei mine, some 600 ft below surface, cut very nearly perfect slots above and below the reef on a stope face but was unable to cut slots in the reef itself. At the Doornfontein mine, however, where the tests are currently being carried out at a depth of 8,000 ft below surface and where there is a much greater pressure acting on the rock face, vertical fracture planes can be clearly seen in the hangingwall running parallel to the face. Owing to the presence of these fracture planes it has been found impossible to cut slots of any depth and the action of the machine is more one of spalling than of cutting, resulting in slabs of combined reef and waste falling from the face as the cutting tool advances. This is accentuated by the existence of a well-defined hangingwall parting plane. Most of the slabbing takes place from the slot cut below the reef to the hangingwalI of the stope. Since waste sorting in narrow conditions and poor lighting is not an efficient operation, the reef together with a proportion of waste rock, has to be removed from the stope. The ripping action of the machine as opposed to slot cutting under these particular conditions may not be a great disadvantage, as the volume of waste which can be packed depends on the ratio of reef width to stope width and with a narrow reef body some waste has to be removed to the surface. In these circumstances mining at depth with this type of machine should not be viewed as selective mining but more correctly mining without explosives. Another type of rock-cutter is being tested by the Gold Fields Group, consisting of a diamond studded rotating disc, which has, to date, cut slots 10 ft in length and averaging 7 1/2 in. in depth. It is, however, too early to comment on the practicability and economics of such a cutter. The great interest that is at present being shown in breaking rock without the use of explosives warrants comment on the Robins raise-borer, recently introduced into South Africa, and used for the first time with great success at the Doornfontein mine.