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By T. Bezuidenhout, J. D. Visagie

In recent years the requirements for a barrier system between the waste body of tailings storage facilities (TSFs) and the natural ground (NG) has necessitated the use of HDPE-lined TSFs in South Africa and other countries. The addition of an HDPE liner creates an interface between, inter alia, the tailings and surrounding soils on the footprint of the TSF. It is known that low-strength materials beneath slopes can cause slope instability. One method which can theoretically mitigate this instability of a lined TSF is the addition of stability bunds along the footprint of the TSF. Altering the profile of the footprint to include slope changes which oppose the direction of the failure creates passive slices in a limit equilibrium analysis. The passive slices actively oppose the movement of active slices, resisting the mobilization of tailings, thus greater active slice forces are required to develop a failure surface running along the liner interface. Two scenarios are presented and compared. The first scenario retains the ground profile unaltered and the second scenario includes stability bunds along the ground profile. An in-depth assessment is made of the interslice forces and the interface shear stresses for each scenario. The theoretical background is discussed in greater detail to determine the mechanisms of reinforcement provided by the bunds.

Jun 2, 2022

By A. E. Lewis

The emphasis of this paper is on the characterization and testing of the slag produced by a secondary lead refinery. This work forms part of a broader investigation aimed at reducing loss of valuable product from the process as well as minimizing the environmental impact of the process wastes. It was this work that led to a critical examination of the standard waste classification tests. Characterization of the slag was carried out using a number of complementary techniques. In the broader context, the slag characterization aided in identifying process deficiencies and thus was a critical tool in suggesting potential for process optimization. For this study, the slag characterization provided a relatively comprehensive picture of the composition and properties of the slag, which facilitated understanding the behaviour of the slag under batch test conditions. On the basis of quantity of hazardous components alone, the slag is hazardous according to South African Acceptable Risk Limits (ARL). However, when both the quantity and the leach potential of the hazardous components is taken into account, standard waste tests carried out by three independent agencies indicate that the slag should not be classified as hazardous according to local regulations. Also, according to United States Environmental Protection Agency (US EPA) limits, which are independent of the quantity of the waste, the slag would not be classified as hazardous. The standard waste tests used by the independent agencies was the Toxicity Characteristic Leach Procedure (TCLP), a test which was developed by the US EPA to classify hazardous wastes. One of the requirements of this batch test is that it should be quick, simple to carry out and that the results should be reproducible. Previously, the applicability of the TCLP test to mineral processing and metallurgical wastes has been challenged on a number of points. Additional testing of the slag was carried out using both the TCLP and the Synthetic Precipitation Leach Procedure (SPLP) recommended by the American National Mining Association as being more appropriate for mineral processing wastes. The particular physical and chemical characteristics of the secondary lead slag highlighted additional limitations of both the TCLP and SPLP tests as standard laboratory batch procedures. Keywords: environmental protection, secondary lead processing, slag, leach testing, TCLP, SPLP, ARL, hazardous waste, batch tests

Jan 1, 2000

By S. O. Bada

Fine phosphate feed is considered to be slime and normally disposed of as a discard in settling ponds or dumped as landfill. The purpose of this research was to establish whether commercially acceptable qualities and yields could be obtained from this material using dry separation methods. The results obtained from the electrostatic separation of <105 µm phosphate ore are presented. An existing separator was upgraded in order to improve on product and flotation concentrate recovery, to test different mineral, and to reduce particle residence time between the charging chamber and the separating zone of the separator. The operating conditions were varied according to the charges imparted to the particles in the electric field, and according to other device parameters. Parameters such as splitter position, charge reversal, rotation speed, charging voltage and separating voltage. The <105 µm phosphate feed was concentrated under both triboelectrification and inductive charging. The use of inductive charging and charge reversal resulted in a significant increase in grade for <105 µm phosphate feed, with the P205 grade increasing from about 12 per cent to 20.50 per cent, and a recovery of 26.30 per cent under a single stage of separation. It was found that better separation was achieved at rotation speed of 6000 r/min, -8 kV charging voltage, and 25 kV separating voltage.

Jan 1, 2012

By R. M. Goktan

Point-attack picks are one of the most widely used tools for the mechanical excavation of rock and coal. In the literature, some practical formulas have been developed to estimate their performances under varying cutting conditions such as the pick geometry, cutting depth and cutting geometry. In this study, it is shown that Evans?s theoretical model, the most cited in the literature, has serious limitations concerning the changes in the cutting geometry. Analysis of the two independent full-scale linear rock cutting experimental data reveals that both his theory and its recent modification can not fully explain the mechanism of rock breakage under asymmetrical attack. The cutting force predictions made by employing such models are shown to be too significantly weak to be of any service in practice. In this study, a semi-empirical approach was followed by means of which cutting forces under varying cutting geometries could be made. By analysing the full-scale rock cutting test data, prediction equations of the peak cutting force and mean cutting force have been developed. Comparisons of laboratory determined and predicted force values indicate that the suggested prediction equations are applicable to quite different rock materialsm which have uniaxial compressive strength in the range of about 30?170MPa, and valid for different cutting geometries. It is also shown by regression analysis that the established prediction equations are statistically significant.

Jan 1, 2005

By A. Andrews

Paper written on project work carried out in partial fulfilment of MSc (Eng) degree Solid state sintered silicon carbide ceramics are used in aggressive environments as sealings. There exist data concerning corrosion, but there are only few data concerning their electrocorrosion behaviour. Therefore the electrochemical corrosion of solid state sintered silicon carbide (SSiC) ceramics has been studied at room temperature in acidic and alkaline environments by using potentiodynamic polarization measurements. The investigation showed a pronounced electrochemical corrosion in bases and acids. In HCl andHNO3pseudo-passivity features due to the formation of a thin layer of SiO2on the surface were observed, whereas in NaOH soluble silicate ions were observed, resulting in more pronounced corrosion. The microstructural observations of initial and corroded samples reveal that the residual carbon found in the microstructure do not dissolve preferentially. Keywords: Corrosion; SEM; SSiC; polarization test.

Jan 1, 2006

By J. A. de Carvalho Junior

This paper analyses the impact of the uncertainty associated with the input parameters in a mine planning optimization model. A real example was considered to aid in the building of a mathematical model that represents the coal production process with reference to the mining, processing, and marketing of coal. This model was optimized using the linear programming concept whereby the best solution was perturbed by the stochastic behaviuor of one of the main parameters involved in the production process. The analysis of the results obtained permitted an evaluation of the risk associated with the best solution due to the uncertainty in the input parameters.

Jan 1, 2012

By V. B. Teffo

The aim of the project was to experimentally determine the coefficient of restitution, and static and rolling friction of Eskom-grade coal for discrete element modelling (DEM). These parameters will be used in further DEM studies to simulate the flow and behaviour of coal during conveyance. For the simulation to yield realistic results, the parameters for the different coal shapes identified in the samples were determined. DEM uses spherical particles, and it was found that the difference between the DEM default parameters and those measured is significantly different, by as much as 97%, which illustrates the importance of experimentally determining these parameters. The spherical particles in DEM can be used to construct the various coal shapes identified, and the parameters measured can be used to simulate realistic results. The conveyance system can then be optimized accordingly.

Jan 1, 2013

By F. Pinto, J. V. Lemos, A. Sousa, L. Ribeiro e Sousa

The Rossio railway tunnel was built in 1890 crossing several formations involving limestones, basalts and also sandy and clayey formations. Due to the fact that it is an old underground structure rehabilitation and repair works were performed, namely at Km 0,900 and in a zone crossed by a new tunnel from the Lisbon Metro. Reinforcement support systems were designed in the Rossio tunnel in order to prevent its stability. In this paper, repair works and anchor tests performed at km 0,900 are presented, as well as the monitoring system implemented in order to observe the structural effects induced by the construction of the works. For the interpretation of the obtained information complex 3D models was built, permitting the simulation of the sequential excavation scheme used, non-linear behaviour of the different formations, and the support systems used. Der 1890 erbaute Rossio Eisenbahntunnel durchoertert mehrere Formationen, einschliesslich einer Kalkstein-, Basalt- sowie einer sandigen und tonigen Formation. Auf Grund des Alters des unterirdischen Bauwerks wurden Instandsetzungs- und Reparaturarbeiten im Bereich km 0,900 sowie im Kreuzungsbereich mit einem neuen Tunnel der Lissabonner U-Bahn durchgeführt. Aussteifungssysteme wurden entworfen, um die Stabilität des Rossio Tunnels zu gewährleisten. Im Folgenden werden die Instandsetzungsarbeiten und Anker Tests im Bereich km 0,900 sowie das Messystem zur Ueberwachung der strukturellen Auswirkungen der Bauarbeiten dargestellt. Zur Interpretation der gewonnenen Informationen wurden komplexe 3D Modelle entwickelt, die eine Simulation des Bauablaufs und die Anwendung nichtlinearer Stoffgesetze fuer die verschiedenen Formationen und Aussteifungssysteme ermöglichten. Le Tunnel ferroviaire du Rossio a été construit en 1890, traversant des différents terrains comme des calcaires, des basaltes et aussi des formations limoneuses et sableuses. Dû à l’ancienneté de l’ouvrage, des travaux de réhabilitation et réparation ont été faits, nomment au km 0,900 et dans la zone traversée par le nouveau tunnel du Metro de Lisbonne. Des systèmes de support renforcé ont été conçus pour le Tunnel du Rossio de façon à rassurer sa stabilité. Dans ce papier, on présente les travaux de réparation et les essais d’ancrage réalisés au km 0,900, et aussi, le système d’auscultation mise au point pour l’observation des effets structuraux induits par les travaux. De façon à interpréter l’information résultant de l’observation, des modèles 3D complexes ont été utilisés, permettant la simulation de la méthode séquentielle de l’excavation, du comportement non - linéaire du terrain et, aussi les systèmes de support utilisés.

Jan 1, 2003

By Nicholas Adrian Barcza

"What affects and influences one’s perspective of the mining and metallurgical industries?One’s perspective of the industry we work in changes over time as a function of our experience as well as from the interaction we have with colleagues locally and probably even more so with those internationally. Furthermore, the ever-changing environment continues to impact the context in which one sees things. Living mostly in South Africa through its changes in the past fi fty years but also having the opportunity to travel extensively and work on projects abroad adds an invaluable richness to this more global perspective. One of the greatest challenges is how best to use this experience to endeavour to support the many potential opportunities in southern as well as sub-Saharan Africa. However, one has also to face the realities of how the best interests of the country and its peoples are sadly often not well served for various unfortunate reasons. Investment, education, regional stability, and good governance are some of the most critical considerations for the prosperity and survival of the region.The mining and metallurgical industry in southern and sub-Saharan Africa changed significantly during the post-colonial and apartheid eras as a result of global and regional developments that have impacted the ownership of businesses, the technologies used, and products produced in a manner that was not envisaged even fi fty years ago. Southern Africa’s mining and metallurgical industry has progressed from one based mostly on diamonds and gold in the late 19th century to a much more diverse one that involves the production of a variety of other precious, base, and ferrous metals and minerals as well as coal and industrial minerals. The infrastructure and manufacturing capacity was largely developed to meet the needs of this industry during its growth phases, but even though the dynamics have changed there is still a need for more efficient and effective support systems in the region."

Jul 1, 2019

By F. T. Cawood

This article is a continuation of a series of publications by the authors on the international debate on resource nationalism, with specific reference to South Africa. Previous outcomes have shown that mine nationalization is not a solution for South Africa, and that maintaining stability of the current mineral and tax regimes is fundamental. It will not be wise to replace existing law and policy instruments until there is a better understanding of the distinction between fact and public perception about the impact of the current system. The new scheme of state custodianship linked to a mining royalty that effectively targets economic rents provides for effective resource use. The methodology in this article is to consider how South Africa&apos;s mineral tax regime can be tweaked to achieve optimal management and benefit from mineral extraction and associated rents by avoiding changes feared by investors. The major finding is that the current suite of instruments can be considered a suitable platform for optimal management of resource rents. However, it will be necessary to first investigate ways of improving the mineral beneficiation intent of the royalty structure, and secondly investigate whether the mineral rent portion of the royalty formula can be ring-fenced for the purpose of establishing a sovereign wealth fund.

Jan 1, 2013

By J. Pelders, G. Nelson

"Fatigue is a significant concern in the mining industry as it is a causal or contributing factor in many incidents and accidents. Fatigue can be caused by work- and non-work-related factors. There is a lack of information about associations between demographic and other non-work factors, and fatigue. This study aimed to assess associations between demographic, work, living, and socioeconomic conditions, and lifestyle characteristics, and fatigue at a platinum smelter in South Africa. Eight interviews with management and two focus groups with production workers were conducted, and 75 questionnaires were completed by production and other workers. Both work- and non-work-related factors were considered to be causes of fatigue. These factors included overtime, shift work, high workloads, activities performed outside of work, age, race, housing tenure, diet, sleep disorders, stress, and job satisfaction. In general, higher levels of fatigue were reported by younger participants, those who rented accommodation, ate less healthily, had a sleep disorder, and those with high levels of stress and low job satisfaction. As various demographic, lifestyle, and wellness-related factors were associated with fatigue, both work and non-work contributors should be addressed in fatigue management plans. BackgroundFatigue may be defined as ‘a state of impaired mental and/or physical performance and lowered alertness arising as a result of, or a combination of, hard physical and mental work, health and psychosocial factors or inadequate restorative sleep’ (BHP Billiton, 2005). Williamson et al. (2011) define fatigue as a biological drive for recuperative rest. Sleepiness and fatigue are related, and the terms are often used interchangeably. However, sleepiness, more specifically, can be defined as sleep propensity, or a person’s tendency to fall asleep (Hossain et al., 2003; Shen, Barbera, and Shapiro, 2006).Increasing levels of fatigue and sleepiness are associated with lapses in attention, errors, response slowing, fluctuations in alertness and effort, and impaired attention, working memory, long-term memory, decision-making, and creativity (Alhola and Polo-Kantola, 2007; van Dongen and Dinges, 2000). Fatigue is also associated with adverse effects on mood and impulsive behaviours (Alhola and Polo- Kantola, 2007; Minkel et al., 2011; Schwarz et al., 2013). It is a significant concern in the mining industry as it is commonly identified as a causal or contributing factor in many accidents and injuries (Schutte, 2009). Fatigue can also lead to long-term health problems, including digestive problems, heart disease, stress, and mental illness (Shaw, 2003)."

Mar 1, 2019

By S. W. Jacobsz, Y. Narainsamy

Several high-impact tailings dam failures around the world in recent years have placed a renewed focus on the stability of tailings dams and pointed to potential shortcomings in traditional drained design and safety evaluation procedures. A need to consider undrained shear strength in the design of tailings facilities has become apparent. However, there are specific requirements that need to be met before undrained shearing occurs. In South Africa, the last major failure was likely the Merriespruit disaster in 1994, which leads to the question of whether the conditions required for undrained shearing are readily applicable to South African tailings dams. This paper describes research at the University of Pretoria that has recently commenced to further investigate the conditions required for undrained failure to occur. The research includes laboratory and field testing to replicate these conditions in the laboratory and relate them to those found in an active tailings dam.

Jun 2, 2022

By D. S. F. Silva

A survey of 120 recent NI 43-101 technical reports was conducted to evaluate the current state of practice regarding resource classification techniques. The most common classification techniques are based on search neighbourhoods (50% of recent reports), drill-hole spacing (30% of recent reports), and/or kriging variance (6% of recent reports). Two new techniques are proposed. The first is based on kriging variance and involves removing one or more drill-holes with the highest weights while performing kriging and using the resultant kriging variance for classification. This technique has the advantages of variance-based techniques and reduces artifacts. The second technique is based on conditional simulation and uses a moving window approach for classification at the desired selective mining unit resolution based on larger production volume criteria. This technique has the advantage of accounting for heteroscedasticity, which is a common characteristic in mineral deposits, and also reduces artifacts since a production volume scale is considered for the actual classification. The drill-hole spacing, search neighborhood, kriging variance, and simulation-based techniques are described and compared for 2D and 3D examples with regular and irregular drilling patterns to highlight the advantages and disadvantages of each method.

Jan 1, 2014

By M. Moseki

Paper written on project work carried out in partial fulfilment of B.Sc. (Eng.) (Metallurgy of Materials) degree This paper presents the research into melting of scrap for job creation purposes in rural areas. The research was done on behalf of Mine Recycling Services (MRS), the company that will implement the project. The project involves the research into available cost effective and easy to operate technology. The paper covers the experimental and theoretical work that was conducted. The results were used to determine the best equipment and method for melting and casting brass scrap.

Jan 1, 2002

By S. Bradshaw, A. Mabentsela

"Physical and numerical modelling methods were followed to identify mechanism(s) for tundish slag entrainment in a bare tundish and one with a flow control device (FCD).The physical and numerical models made use of water and paraffin to model steel and slag respectively. Observations from the physical model showed that the steel-slag interface remains immobile in both cases. Entrained paraffin formed droplets approximately 1 mm in diameter. Results from both models (numerical and physical) showed that in both cases (bare and FCD case), areas of high entrained slag concentration exist near the inlet region. The entrained slag concentration decreases towards the tundish endwalls.Flow patterns and velocities tangential to the steel-slag interface from the numerical model showed that slag entrainment in both the bare tundish and tundish with a FCD possibly takes place via two mechanisms. First, the slag moves across the steel-slag interface via mass transfer; secondly small velocities tangential to the interface at depths greater than 10 mm below the interface carry the already ‘entrained’ slag into the bulk steel phase. These tangential flow patterns are dominant in the inlet region, hence the high concentration of entrained slag in this region. IntroductionThe tundish serves as the last metallurgical vessel through which steel passes before solidifying in the moulds. It is in the tundish that the last traces of non-metallic inclusions should be removed, otherwise the inclusions carry over to the moulds and cause defects in the steel product. In the tundish, the slag is less dense than the melt and thus resides on the top of the melt. The slag provides a sink into which the non-metallic inclusions float to and dissolve. The slag also protects the melt from air and heat loss. However, when slag is entrained in the melt as a result of increased turbulence or shearing at the steel-slag interface, slag can become a source of nonmetallic inclusions.Numerous studies on flow patterns in the tundish have been carried out since the introduction of the tundish. These studies were aimed at improving the flow characteristics in the tundish (Chattopadhyay, Isac, and Guthri, 2010; Cloete, 2014; Jha, Dash, and Kumar, 2001; Jha, Rao, and Dewan, 2008;"

Jan 1, 2017

By T. P. Williams, M. B. Rydzewski, B. Corner

Konkola Copper Mines (KCM) plc is an integrated copper producer operating on the Copperbelt in Zambia. KCM has numerous mining operations located in the towns of Chililabombwe (Konkola Mine), Chingola (Nchanga Open Pit and Underground operations), Lusaka (Nampundwe Mine), with a smelter located in Kitwe (Nkana Smelter) and an SX-EW plant in Chingola (Nchanga Tailings Leach Plant). [ ]

Jan 1, 2005

By A. M. Hearn, J. R. Henning, A. S. J. Van Rensburg

The lining, together with the electrodes, forms the heart of the operation of a submerged arc furnace. Subsequent to a lining failure on M12 furnace during the early 1980s, Metalloys was active in investigating the concept of thermally efficient ?freeze? linings for its furnaces. The theory revolved around that, not only would, thermally efficient linings result in significant cost savings, but they would also last longer as a result of being subjected to less harsh operational conditions. After having proved the concept on the .smaller. furnaces, Metalloys decided to implement the concept on its largest submerged arc furnace, M12 Subsequent to having recovered from an impending failure of a lining installed in 1981 in M12 in the mid 1980s, Metalloys managed, through rigid lining management, to extend the life of this lining to 1999. At the end of 1999 the decision to replace the lining in the furnace with a ?freeze? lining was made and planning and design proceeded in earnest. This paper discusses the options considered in making the final decision. The features of the design of the lining are also discussed. Consideration is given to the furnace shell cooling system as a result of its importance in maintaining the thermal equilibrium in the lining. Note is made of the fact that the purchase of a .freeze. lining is an expensive exercise but that the time savings in the installation of the lining and the efficiency improvements during operation far outweigh the additional capital cost. The experience on M12 has been that the payback period of the marginal capital expenditure is less than three years. As a result of the opportunity to reline a furnace the size of M12 not presenting itself very often, the learning points from the installation of the lining and the operational advantages and disadvantages are significant. Finally, the point is made that the project had its pros and cons but overall the success of the project has been evident and, as such, the ?freeze? lining is likely to become the norm at Metalloys.

Jan 1, 2004

By C. Erichsen

ABSTRACT: The Berg Bock Freeway Tunnel represents the southernmost link of the "Thuringian tunnel chain" of the new freeway A71 located in the eastern part of Germany. It comprises two tubes each 2700 m in length. From north to south, it passes through the Suhl granite, the base sediments and the porphyrite of the New Red as well as the layers of the Middle Bunter. The two tunnel tubes were driven by the shotcrete method within appr. 10 months. With four tunnel faces, maximum performances totalling appr. 30 m/d were attained. Additional, supplementary demands on the safety conception, resulting from the findings from and the analysis of fire accidents in tunnels in recent years, had to be fulfilled in the execution planning at short notice. The inner lining is largely constructed using non-reinforced concrete. Reinforcement is only installed in the portal zones, in tunnel sections in less stable rock and in areas with a special cross-section as for instance cross connections and niches. ZUSAMMENFASSUNG: Der Autobahntunnel Berg Bock stellt das südlichste Glied der "Thüringer Tunnelkette" auf der Autobahn A71 dar, die im Osten von Deutschland liegt. Er besteht aus zwei Röhren von je 2700 m Länge. Vom Norden nach Süden durchörtert er den Suhler Granit, die Basissedimente und den Porphyrit des Rotliegenden, sowie die Schichten des Mittleren Buntsandsteins. Die beiden Tunnelröhren wurden in Spritzbetonbauweise in einer Bauzeit von etwa zehn Monaten aufgefahren. An vier Vortriebsorten wurden Spitzenleistungen von insgesamt etwa 30 m/d erzielt. Ergänzende Anforderungen an das Sicherheitskonzept, die sich auf der Grundlage der Auswertung der in den letzten Jahren aufgetretenen Brandunfälle in Tunneln ergeben haben, wurden im Rahmen der Ausführungsplanung kurzfristig berücksichtigt. Die Tunnelinnenschale wurde weitgehend aus nicht bewehrtem Beton hergestellt. Nur in den Portalzonen, in Tunnelabschnitten mit weniger standsicherem Fels und in Bereichen mit speziellen Querschnitten, wie beispielsweise im Bereich von Querstollen und Nischen, wurde bewehrter Beton ausgeführt. RÉSUMÉ: Le tunnel d&apos;autoroute de Berg Bock représente le plus méridional maillon de la "chaîne thuringienne de tunnels" sur l&apos;autoroute A71 dans l&apos;est de l&apos;Allemagne. Il se compose de deux tubes d&apos;une longueur de 2700 m chacun. Du nord vers le sud, il traverse le granit de Suhl, les sédiments de base et le porphyrite du Rotliegendes, aussi que les strates du grès bigarré intermédiaire. Les deux tubes étaient creusés en méthode de construction de béton projeté dans une période de construction d&apos;environ dix mois. À quatre fronts de taille rendements maximaux collectifs d&apos;environ 30 m par jour étaient obtenus. On a eu égard à court terme dans la conception d&apos;exécution à des demandes supplémentaires vers la conception de sécurité, qui ont résulté sur la base de l&apos;interprétation des accidents d&apos;incendie dans des tunnels dans les années dernières. La paroi intérieure était construite largement de béton non armé.

Jan 1, 2003

By M. D. Budeba

Determining the efficiency of a surface coal mine operation is an essential activity, which can help in deciding on the optimal use of input resources, including effective capital allocation, in generating a desired quantity of coal of a specific quality. Mines operate today in challenging conditions, with diminishing reserves of high-quality coal, remote location of new coal deposits, infrastructure problems, environmental legislation, and the effects of climate. All these have an impact on the performance of a mine. Given such challenges, a company has to be technically efficient compared to other existing coal producers in order to generate profits. It can use the measurement of its efficiency to evaluate its productivity, benchmarking this against the best-performing mines and determining optimal variables in order to minimize slack and achieve the desired outputs. This paper discusses the use of Data Envelopment Analysis (DEA) in evaluating the efficiency of a surface coal mine supply chain for the coal export market. The supply chain is considered to be composed of subprocesses that are modelled as a multistage system. Numeric examples will be used to illustrate the application of DEA.

Jan 1, 2014

Paper written on project work carried out in partial fulfilment of BSc Engineering (Mining) The aim of this project is to determine whether certain pillars occurring within the no. 1 shaft and no. 2 sub-shaft ground are feasible for extraction. The extraction of these pillars is essential in prolonging the life of Kloof Main Shaft as its VCR resource becomes depleted. Extraction of these pillars will require a combination of designs and factors, with rock mechanics and ventilation being the main considerations. Primarily for the pillar extraction, an initial production target of150 kg gold, mine able in one year from commencement of ?opening up? was set. The planned target has been exceeded and the feasible pillars identified are expected to yield an additional 1 390 kg of gold to the shaft?s production profile. However, not all the required ventilation designs have been completed to date, the reason being that at the time of the project, many of the pillar areas were inaccessible and thus ventilation conditions are unknown. This project is therefore an ongoing process and will require further design once all targeted pillar areas have been opened up. A preliminary costing analysis of the pillar mining was performed and it was found that all targeted pillars with the exception of 38?61 pillar are profitable.

Jan 1, 2005