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By Marco Barla, Mariacristina Bonini, Giovanni Barla

ABSTRACT: The paper describes the characterisation studies of Tectonised Clay Shales at laboratory and in situ scale. The interest relates to tunnelling under squeezing and swelling conditions, in Italy, along the Apennines. The results of monitoring during full face excavation are presented in conjunction with numerical modelling. RESUME: Cet article présente la caractérisation, à l'échelle du laboratoire et in situ, des Argiles Chaotiques. L'attention est portée sur le creusement, dans ces milieux gonflants, des tunnels, dans les zones montagneuses des Appennini, en Italie. Enfin, on présentera les résultats de la modélisation numérique et la comparaison de ces derniers avec les mesures effectuées in situ. KURZFASSUNG: Die Arbeit beschreibt die Charakterisierungsstudien von tektonisierten Schiefertonen, sowohl im Labor als auch vor Ort. Das Interesse gilt dem Tunnelbau unter Quetsch- und Schwellbedingungen in Italien entlang der Apenninen. Die Überwachungsergebnisse des ganzflächigen Ausbruchs werden mit numerischen Modellen präsentiert.

Jan 1, 2003

Although not fully accepted in South Africa, the Theory of Sampling originally proposed by Pierre Gy is fast becoming the cornerstone of sampling practice throughout the world. The growing acceptance of Gy?s Theory of Sampling in South Africa can be attributed to a number of factors, chief amongst them being the development of a tradable mineral asset market, the promulgation of the Mineral and Petroleum Resources Development Act (MPRDA), the growing number of commercial and academic courses that are offered on sampling, and the regulation of the industry through internationally acceptable guidelines and rules for reporting and trading in mineral assets. The size of the South African minerals industry and the dependence of our economy on mineral production have also meant that correct sampling is of key importance to mineral trade. ISO standards have been the principal guides for producers of mineral bulk commodities who produce to customers? specifications, whereas Gy?s insights have been most readily accepted by precious and base metals producers whose product is sold into metal markets. Understanding of small-scale variability is essential in the precious and base-metal industries, but detailed studies of the effects of heterogeneity have not been as productive in the bulk commodities. Sampling practices at different stages of mineral development from exploration, face sampling and grade control, ore processing and handling, metallurgical sub-sampling, point of sale sampling, and sampling in the laboratory are considered in the gold, platinum, ferrous metal, and coal industries. A summary of the impact of poor sampling in these industries is presented. Generally it appears that poor sampling practice is most likely to erode mineral asset value at the early stages of mineral development. The benefits of good sampling are considered, especially with regard to the financial implications of bias and error on large and consistent consignments of bulk commodities. Keywords theory of sampling, sampling errors, ISO standards.

Jan 1, 2014

By S. Kwon

When an underground excavation is created near to an instrumented measuring location, deformation at the location increases. The characteristics of this deformation increase, as well as the duration of the influence caused by the adjacent excavation, is dependent on parameters such as opening geometry and measuring location. In this study, neural networks were applied to investigate the deformation increase and the influence of each parameter on the deformation change derived from extensometer measurements at the Waste Isolation Pilot Plant (WIPP) site in New Mexico, USA.

Jan 1, 1998

By R. L. Castro

Block caving methods, when operated under favourable rock mass conditions, can achieve higher production rates and lower operating costs than other various existing underground mining applications. For this reason, it has been considered the preferred method for the mining of deep and large orebodies in current and future operations around the world. One of the key aspects in the design of block caves is the selection of the production level layout, which, among other parameters, is based on the gravity flow characteristics of the caved rock. This is because gravity flow has a large impact on total ore recovery and the amount of dilution in a caving operation. Today, there are a number of computer based methods which aim to emulate the gravity flow pattern of the caved rock. In this paper, the authors present the development of FlowSiman improved model of gravity flow based on the cellular automaton approach, to estimate dilution entry, mixing and ore recovery. As part of the model development, flow simulations were conducted and subsequently compared to full-scale data collected at two mine sectors operated by Codelco Chile. The results indicate that by using proper calibrated parameters, good correlations between simulated and measured grades as well as dilution entry are obtained. The potential use of the numerical tool to evaluate drawpoint spacing in terms of recovery and dilution for block/panel caving operations is also presented.

Jan 1, 2009

Power Point Presentation

Jan 1, 2007

By Hao Li, Allan Moss, Richard K. Brummer

At the Palabora Mine, the transition to caving 400 m below the bottom of the 800 m deep pit resulted in a slope failure of the North wall that began in 2003, and is still mobile. This failure can be explained by the daylighting into the cave zone of a prominent joint set. The failure was modelled by the 3-dimensional code 3DEC, which is capable of modelling the nonlinear behaviour of discontinuum materials with large displacement.

Jan 1, 2006

In order to deliver a quality shotcrete and concrete product underground for the extensions to the Cullinan Diamond Mine operations it was decided to develop a new, simpler concrete product to meet underground support requirements. The aim was to develop a concrete product that not only reduced costs but also met the performance criteria of the current range of concrete products used on Cullinan Diamond Mine, a 25, 45 and 60 MPa concrete and a fibre reinforced wet shotcrete. The concrete product batching and delivery system was to be from surface as opposed to the current underground batching systems. The operational principle was to include an automated surface batching plant with delivery of the concrete product to a borehole containing suspended pipelines delivering to an underground storage facility from where the product is delivered to the working area by further pumping or agicars. Keywords: concrete, shotcrete, full flow, frictional loss, pipeline transport, positive displacment pump

Jan 1, 2006

By H A. Myburgh

The beneficiation of heavy metal oxides, such as iron ore, is usually performed with heavy medium separation in cyclones, static baths and lately with Larcodems. Atomized ferrosilicon is most suitable as a heavy medium at densities above 3600 kg/m3 whereas a mixture of milled and atomized ferrosilicon is suitable at densities below 3600 kg/m3. When operating a beneficiation plant at densities higher than 3600 kg/m3 the quality of the ferrosilicon particles is an important factor that influences the control of the beneficiation process. Therefore, it is important to know how the rheology would be affected by the ferrosilicon quality as it also influences the control of the process at these elevated densities. Background The Kumba Resources Sishen Iron Ore Mine in South Africa produces 26.5 Mt iron ore per annum from its beneficiation plant. The ore body consists mainly of laminated and massive type hematite ore that is crushed down to ?90mm before being beneficiated by means of a combination of Wemco drums, Larcodem and dense medium cyclone separators. The need for higher densities When the percentage of high-density gangue2 is higher than normal in the run-of-mine (ROM), a higher separation density is necessary to produce a product to specification. Certain ore types of this quality in the Sishen reserves require a separating density higher than 4000 kg/m3, whereas densities would normally average 3600 kg/m3 when beneficiating ores of normal high-density gangue content. Sink and float tests conducted on the ROM material at Sishen revealed some interesting characteristics. In the waste fraction, (density < 3600 kg/m3) it was found that the %Fe was <21% (Fig. 1). Similarly, for the product fraction (density >3000 kg/m3), the percentage Fe varied between 35% and 67.2%. The bulk of the material (88%) actually had a density greater than 4000 kg/m3 and a Fe content that varied between 63% and 67.2%. At a density interval of 3600 to 4000 kg/m3, the Fe content varied from 37% to 60% with an average of 45%.

Jan 1, 2006

By J. Kortnik

Mining has always been, and still is, an activity which is vital for the development of mankind. This is because a predominant proportion of industrial products and energy is produced from raw materials that are excavated using mining methods. The need for environmental protection and the close proximity of urban settlements and mines in Slovenia have necessitated ever stricter requirements for the excavation of raw materials and the introduction of more environmentally-friendly mining methods. This is achieved by implementing a closed eco-technological cycle of raw material excavation within the scope of mining methods. In surface mines, this means prompt reclamation of the degraded surfaces, and in underground mines the use of methods with minimized impact on the surface and on underground water. In underground mines, mining methods with backfilling installed according to the multi-barrier disposal system are the only ones that allow the possibility of implementing a closed eco-techno-logical cycle of excavating raw materials. Various industrial waste materials are also included in the backfilling material in order to improve its strength properties. Backfilling consisting of several different waste materials is produced in the form of a composite. Before backfilling consisting of waste material composites can even begin to be used in mines, an environmental impact assessment of its suitability for mines needs to be made. In order to make such an assessment, a pressure leaching cell and an open diffusion cell were made, i.e. a pressure leachate test and a sorption test were developed. The two cells and the developed tests will enable the study of the influence of backfilling on the environment if installed in an underground mine. The pressure leachate test performed with the use of the pressure leaching cell simulates leaching from a consolidated backfill during the seeping of underground water into the backfilling material under pressure. The sorption test performed in an open diffusion cell simulates the flow of eluate leached from the backfilling material through the rock/geotechnical barrier. The two tests were developed in such a manner that they are performed either in succession immediately after one another, but they can also be performed separately at a certain time interval. The paper presents an assessment of the suitability of backfilling made of different waste material composites. Keywords: environmental impact assessment, multi-barrier disposal system, waste material composites, pressure leachate test, sorption test, pressure leaching cell, open diffusion cell, eco-technological cycle, mining methods with backfilling.

Jan 1, 2003

By A. P. Squelch

The question of what stress condition exists in the hangingwall of tabular stopes remains topical and largely unanswered. Limited field data exist to quantify the situation and provide calibration for investigative computer modelling exercises. Work conducted in1989 and 1990 under a Chamber of Mines Research Organization (now the CSIR: Division of Mining Technology) programme of research into the behaviour and benefits of backfill may assist with this situation. The original work was motivated by the premise that the improved hangingwall stability in backfilled panels (identified by rockfall accident analyses) is due to a change in the hangingwall stress regime. Current, largely theoretical, studies into mechanisms of stope hangingwall behaviour and support interaction could benefit from considering these data. Keywords: Backfill, horizontal stress, stope hangingwall, hangingwall stability, support interaction.

Jan 1, 2002

By P. Mokwena

Paper written on project work carried out in partial fulfilment of BSc (Hons) in Chemical Engineering Diamond synthesis has attracted a great deal of interest because of its exceptional properties and various applications. In this study, the chemical catalytic vapour deposition (CCVD) method was used to synthesize diamond films using acetylene as carbon source and hydrogen as carrier gas at a temperature of 1000°C, and their thermodynamic stability was studied. Photographic analysis revealed that these products are diamond films, Ramman spectroscopy confirmed that they are graphitic while confocal laser scanning microscopic image analyses proved that these diamonds films have structural defects due to iron impurity from the catalyst precursor. The quantity of diamonds films produced is also proportional to the acetylene to hydrogen ratio but these films are larger in size at lower acetylene to hydrogen ratio. Thermogravimetric analyses showed that transformation of these materials begins at 25°C but could not be used to determine if a temperature range below 25°C exists. The stability of these CCVD-synthesized diamonds also increases below 25°C when stored at different temperatures.

Jan 1, 2007

By Hornsey R., P. van der Merwe

The Two Rivers Project is a feasibility study to evaluate the UG2 chromitite layer on Dwarsrivier372KT, Mpumalanga Province, South Africa. The project, which commenced in August 2001, is expected to receive go-ahead early in 2003. The project sponsors (AVMIN 55%, Implats 45%)required project delivery within a short timeframe requiring optimization of the geological and geostatistical programme. Geological modelling was carried out in parallel to the drilling programme, and significant up-front geostatistical preparatory work was done. The time saving was approximately 4 – 6 months on project delivery. The cost saving to the project (excluding NPV considerations) is estimated at R20–30 million. Keywords; Two Rivers Platinum, Dwarsrivier 372KT, UG2 chromitite layer.

Jan 1, 2003

By B. J. Madden

Over 206 million tons of hard coal were mined in South African collieries in 1996. Some 132.5 millions tons came from underground operations and approximately 120 million tons came from bord-and-pillar workings resulting in between 100 000 and 150 000pillars being formed. Coal pillar design remains a significant feature of South African mining. This paper reviews South African coal pillar design procedures in the light of 90 pillar collapses that have occurred since 1904. It shows that, while the current pillar strength formula is still valid within the original empirical range of Salamon1,cognisance must be taken of local conditions. Current South African coal pillar research is attempting to account for the variations in local conditions with the emphasis on the effect of discontinuities and pillar deterioration. It is suggested that a more holistic approach to pillar design be adopted to include a design methodology that examines the stability of the roof, pillar and floor of the underground workings. Using this approach, deviations from the empirical database used by Salamon and Munro will be incorporated into the design methodology resulting in more stable underground workings.

Jan 1, 1998

By P. S. G. Leon

One of the most difficult areas in concession contracts in resource-rich developing countries is achieving an equitable balance between the interests of investors, host states and, increasingly, mine and near mine communities. While some countries in the Andean region have resorted to outright or creeping expropriation of natural resource contracts under the guise of resource nationalism, others such as the Democratic Republic of the Congo (DRC), have claimed international best practice in the review (and setting aside) of important concession contracts.

Jan 1, 2011

By D. S. van Vuuren

Over the last 60 years many different processes were conceived to reduce the cost of titanium produced by the Kroll process. However, success eluded all previous efforts, which were consequently terminated in periods of economic downturn. Recently, the grow thin demand for titanium and the high cost of producing the metal again sparked renewed attempts in various parts of the world to replace the antiquated Kroll process with a more efficient route. The different options to produce titanium are reviewed, classified and evaluated in terms of the fundamentals underlying the technologies, and it is shown that the options considered to be the most likely to replace the Kroll process, are continuous processes to reduce TiCl4 metallo-thermically to titanium powder. Of these, continuous magnesio-thermic reduction of TiCl4 would conceptually result in the lowest-cost and highest-value product. However, when considering by-product salt removal from the titanium product and recycling of the salt as well, sodio-thermic reduction of TiCl4 is better.

Jan 1, 2009

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 N. R. Williams

Black Mountain, a polymetallic base metal mine located in the Northern Cape territory of South Africa has been blessed with high grade economic ore for many years. Now that the Broken Hill orebody is nearing the end of its life, a lower grade orebody (Swartberg) is being exploited to supplement production from Broken Hill. In addition, ore from stopes in the upper levels of the Broken Hill orebody is considerably tarnished (oxidized). As a natural result, the remaining ore contains a higher percentage of magnetite, pyrrhotite and pyrite than in earlier years. Bismuth, cadmium and cobalt also occur in the ore in higher quantities. The life of the mine has been lengthened with the discovery of further deeper-lying ore reserves extending from the Broken Hill orebody suitably called the Deeps section. However, to bridge the gap between development of the new reserve and the exhaustion of the old reserve, these lower grade and tarnished (oxidized) ores have to be treated. The mine has had reasonable success in identifying unfavourable or problematic ore types and stockpiling them separately to blend in small quantities with more favourable ore. Bench and plant scale tests have aided identification of the various ore types and significant improvements in flotation metallurgical results have been seen. Copper, lead and zinc metal occur as sulphides in the ore. The mill consists of a differential and sequential flotation process that extracts copper concentrate, lead concentrate and zinc concentrate respectively with silver metal recovered in the copper and lead concentrates. This paper describes the ore blending strategy employed at the mine to maximize the econo-metallurgical efficiency of the operation.

Jan 1, 2001

The newly implemented mineral law framework exacerbated the need to clarify the roles and responsibilities of mine and land surveyors in the preparation and registration of plans and diagrams. The main concern is that survey tasks may be performed by persons who are not considered competent under the different laws. The methodology used was to analyse historic and present legislation on the issue in order to formulate a narrow interpretation of the current requirements. The major findings are tabulated to present a summary of who is responsible for which areas of survey.

Jan 1, 2010

By Arun Vathavooran, Adrian Singh, Michael Fletcher, Rainer Imhof

The Imhoflot G-Cell, a new development in the pneumatic flotation technology (which incorporates centrifugal forces in the separating vessel) is a recent innovation in the mineral processing world. The G-Cell was invented by Dr Rainer Imhof and commercialised by Maelgwyn Mineral Services Ltd. In a short time span a number of plants and units have been successfully commissioned in the mineral processing industry. In addition, a number of industrial G-Cell flotation plants are in the process of construction for the purpose of coal preparation and environmental remediation. In this paper two industrial installations have been highlighted together with a pilot plant test programme investigating ultra fine flotation recovery for a base metal operation.

Jan 1, 2007

By W. van Antwerpen, J. Guzek, A. Lane

Strategy is about making choices. Mining companies choose to do certain things and not to do other things. Mining is a long-term business, and the choices made typically have large investments attached to them, long payback periods, and significant socio-economic consequences. In today’s uncertain world, it is important to make the right choices. The mining industry in South Africa finds itself in a difficult situation. Operating conditions are tough, the socio-political environment is complex, and financial performance is under pressure. The choices made by all the stakeholders in this industry in the short term will shape the future of the industry. This paper characterizes some of the big, difficult decisions faced by the mining industry in the South African context, and discusses how these decisions could be approached in a fact-based and robust way.

Jan 1, 2015