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By M. Gericke

Over the past few decades the commercial application of heap bioleaching technology for the extraction of base metals has become increasingly important, due mainly to the depletion of high-grade ore reserves. Heap bioleaching is widely used for the extraction of copper from secondary copper sulphide ores. The design and engineering aspects of the process have received considerable attention, but issues related to the microbiology of the process have been subjected to less rigorous scrutiny. The major role of micro-organisms in bioleaching processes is to catalyse the regeneration of ferric iron and protons, from ferrous iron and by sulphur oxidation respectively. It is accepted that even the most carefully engineered heaps are heterogeneous in terms of temperature, pH, the presence of anaerobic pockets, irrigation efficiency, and dissolved solutes. Since interactions between solution chemistry, mineralogy, and microbial populations exist in heaps, a better understanding of the correlation between microbial numbers and types with changes in these chemical and physical profiles with time would be beneficial during process design and operation of heaps, and could result in faster start-up times and higher metal recoveries. This paper reviews the role of microbiology in heap bioleaching processes. Aspects such as microbial diversity, identification and monitoring of cultures, inoculation strategies, colonization behaviour, and tolerance to metals and salts are discussed, and the potential contribution of the knowledge to the improvement of the operation and design of heap bioleach processes assessed. Conclusions are drawn with respect to the role of genetic engineering, heap inoculation practises, and remaining areas for future heap bioleaching research and development.

Jan 1, 2012

By C. P. Smyth

Large volumes of quantitative geochemical data, presenting a formidable interpretation task to geologists, are generated in the course of exploration drilling for new ore deposits. The incorporation of geological expertise into computer programs developed for the interpretation of this data would improve the speed and accuracy with which it is interpreted. A detailed analysis of the geochemical log interpretation problem, together with a survey of relevant research in Artificial Intelligence and petroleum well- logging techniques, confirms, that artificial intelligence, particularly as developed in the fields of expert systems and pattern recognition, provides techniques for implementing such data interpretation programs. In addition, it provides data analysis techniques significantly more powerful than those currently applied to geochemical data, and very appropriate to the hypothesise and test' character of mineral exploration problem-solving. The conversion of raw borehole log data to meaningful higher level geochemical entities, in terms of which geological reasoning may take place, is a critical step in applying these techniques to log data analysis. A method of achieving this conversion as an exercise in signal-to-symbol transformation is presented.1

Jan 1, 1987

By R. G. B. Pickering

The South African narrow reef hard rock mining industry has been stuck in a time warp with relatively little change in the mining process in the last century. This paper presents a methodology on how to implement change in narrow reef hard rock mining. It then explores a number of technologies that have been introduced into this mining industry and the impact that they have had on the mining process. The author then presents his view on whether the defined change process has been followed and sets out to identify the most critical aspect of ensuring that change is successfully implemented. Future demand will also be speculated on.

Jan 1, 2007

By M. M. Hajdasinski

The internal rate of return (IRR) is one of the most popular project evaluation criteria in the mineral industry, as well as in other industrial sectors. Analysis of its assumptions reveals, however, that this criterion does not function in the way it is supposed to. The search for a new criterion that would reflect the true rate of return (TRR) of an investment project or the true borrowing rate (TBR) of a borrowing project has led to the development of several approaches, yielding, for the same project, generally different values of the interest rate in question. Two of those approaches have been selected as the most representative and practical. Each has been presented in two variants, and subsequently analysed. As a result, it is shown that the various approaches to the TRR/TBR are all consistent with the net present value (NPV) criterion, and that each can serve as an independent project evaluation instrument, provided its assumptions can be regarded in a given situation as realistic enough.

Jan 1, 1987

By L. A. Abichequer

ROM grade variability is one of the most important factors influencing plant product recovery. Due to the influence of grade variability on mine profits, it is deemed important to guarantee a proper homogenization of the ore through a well-planned blending and homogenization pile system from which the ore is reclaimed at an acceptable grade fluctuation. This study tests geostatistical simulation efficiency in predicting in situ grade variability. The methodology is illustrated using a data-set from a large phosphate mine in central Brazil. Additionally, real data obtained at the mine site during January and February 2007 were used to derive the actual grades of each pile formed during this period. Each pile was formed by a selection of blocks within a dig line and these lines mined along the year 2007 were also made available. Given the real grades, it was possible to reconciliate and validate the results predicted by the proposed methodology. The main outcome of this study is the opportunity to check the geostatistical simulation as a tool to quantify the variability of the homogenization system.

Jan 1, 2009

By P. M. Vercruijsse

Dredging is an industry in constant transformation. It has changed tremendously in the last decades. The traditional dredging activity, like construction and maintaining ports and harbours, desilting of drainage and irrigation channels, keeping reservoirs at depths and removing sediments from waterways, is still of importance. However, it is surpassed by other applications of dredging technology. Reclamation is an important example, where large amounts of sand are dredged, transported over large distances and used to make new land for industrial, housing, airport and other infrastructural purposes. Beach nourishment and other protective measurements should be mentioned here as well. Other applications like offshore winning of oil and gas, environmental clean-up, mining of interesting minerals like gold, diamonds, titanium and tin as well as aggregates from inland and offshore deposits are of importance. For all of these dredging applications equipment is required, and with changing circumstances and constraints, the design and use altered significantly. Larger dredging depths and increasing capacities require an impressive scale-up of equipment and tools. A demand for higher accuracy and selectivity set the requirement for a higher level of automation and control in combination with a well trained crew. Operations under more difficult circumstances and with other soil characteristics necessitated the development of new dredging components and systems. A sound basis for all developments was and still is a better understanding of the various dredging processes. This paper will highlight some eye-catching developments in the dredging industry. It will focus on issues in the field of hydraulic transport such as ever increasing capacity and dredging depth, as well as the pumping of large size materials.

Jan 1, 2007

By E. Cetin

Orebodies that contain more than one economically important mineral are generally evaluated by parametric cut-off grades. This approach often leads to mis-valuation of mineral deposits because cut-off grades are not based on the grades of each individual mineral and, because of the parametric formulation, are only indirectly related to the individual grade distributions. The only realistic approach is a formulation that accounts separately for each component mineral. The grid search method can be used as a means of multi-mineral cut-off grade optimization in this context. This paper describes the use of the grid search method in cut-off grade optimization for multi-mineral deposits. The authors introduce the general concepts of the method and formulate its application to cut-off grade optimization; they describe a software implementation of the method that can accommodate cut-off grade optimization for mineral deposits that contain up to three economic minerals. Keywords cut-off grade, optimization, grid search, multi-mineral deposits.

Aug 1, 2013

By W. C. Joughin

A risk evaluation model has been developed, that enables the quantification of expected injuries and economic losses resulting from rockfalls associated with a support system in a given geotechnical environment. This enables the comparison of different support systems based on the expected frequency of injuries and the total cost of the support system, including the expected economic losses. The model takes into consideration the variability in joint orientations and joint strength within the geotechnical environment and the variability and quality of support systems. The quantification of the benefits of other rockfall risk-mitigating strategies, such as the effectiveness of barring or monitoring, are also incorporated in the model. The risk model is described in this paper and the validation of the model and case studies are described in Part II.

Jan 1, 2012

By H. Sasao, Y. Obara, A. Hirata

In the upper part of the planned location of the portal of a highway tunnel, there was a steep rock cliff with several unstable rock blocks. It seemed that the risk of those rock blocks to fall was very high. The cut-out to stabilize the rock cliff was monitored with various measuring instruments to prevent the sudden fall of the rock blocks. This paper discusses the measurement of acoustic emission and interpretation of its result during excavation of the rock cliff. We calculated displacements by integrating the accelerogram twice in terms of time, and demonstrated that slight displacements can be calculated from the measured AEs. Dans la partie supérieure de l’emplacement prévu pour le portail d’un tunnel autoroutier, il y avait un escarpement rocheux raide avec plusieurs blocs rocheux instables. Le risque de chute de ces blocs semblait très élevé. Lors de la coupe pour stabiliser l’escarpement rocheux, le suivi a été effectué avec différents instruments de mesure pour éviter la chute brutale des blocs rocheux. Cette thèse présente les mesures d’émission acoustique (EA) et l’interprétation de leurs résultats pendant l’excavation de l’escarpement rocheux. Nous avons calculé des déplacements en intégrant l’accélérogramme deux fois par rapport au temps, et montré que de petits déplacements sont calculables à partir des EA mesurées. Im oberen Teil des geplanten Ortes des Stollenmundes eines Autobahntunnels gab es einen steilen Felsen mit mehreren instabilen Felsenblöcken. Die Gefahr schien sehr groß zu sein, dass diese Felsenblöcke einstürzen können. Beim Abbau um die Stabilisierung des Felsens wurde das Monitoring mit verschiedenen Messinstrumenten zusammengestellt, um den plötzlichen Verfall der Felsenblöcke zu verhindern. Das vorliegende Papier diskutiert die Akustische Emission und die Auslegung deren Ergebnisse während des Abbaus des Felsens. Wir berechneten die Verschiebungen durch zweimalige Integrierung der Accelerogrammen in Bezug auf die Zeit. Die dargestellten kleinen Verschiebungen können aus den gemessten akustischen Emissionen berechnet werden.

Jan 1, 2003

By B. P. Watson

In South Africa, the Bushveld platinum group metal deposits are unique in that they are the largest platinum group metal deposits in the world. These deposits occur as two distinct stratiform tabular orebodies and strike for many hundreds of kilometres. Mining is extensive, with depths ranging from close-to-surface to 2 000 m. The mining method is a variation of planar open stoping. Pillars are widely used to support the open stopes. Crush pillars are commonly used in this role, where the residual pillar strength provides the required support resistance to stabilize the stoping excavations. This paper describes the direct measurement of stress within these crush pillars, and describes the stress?strain behaviour of these pillars. These findings indicate that the measured pillar failure stress is too high. The implications of these findings are that roof damage and pillar bursting could occur, and some examples of this type of damage are shown. The paper concludes that this problem could be mitigated if the three dimensional pillar geometry were modified and the pillars were cut smaller.

Jan 1, 2007

By P. Ramphisa

In South Africa reprocessing used oil into industrial fuel is commercially attractive. The reprocessed product is sold as a substitute for heavy fuel oil that is derived from crude oil (Rose Foundation, 2008). The objective of this investigation is to evaluate the use of petroleum products such as oil, petrol and diesel in Driefontein Gold Mine. The recovery of oil through recycling has costs implications to the mine while the release of petroleum hydrocarbons due to the poor management of the use of petroleum products has potential to cause pollution and negatively affect soil and water. Environmental legislation such as the Minerals and Petroleum Resources Development Act (Act 28, 2002) requires that such negative impacts to the environment be rehabilitated. The rehabilitation cost of pollution caused by petroleum products to the environment increases operational costs in business. Field assessment is conducted to identify the main sources of petroleum product contamination such as leaks in piping, overfills and petroleum spills. The areas that require mitigation would be mapped in the study. Recommendations for mitigation measures will focus on using the best practicable environmental option (BPEO) as well as the best available technology not exceeding excessive cost (BATNEEC). The recovery of oil from the mining industry is generally low and very poor. In this study, the effect of proper management of petroleum products to the mine?s operational costs is investigated and compared to there mediation costs of the impacts caused due to poor management of these products. The study investigates the financial benefit that could be obtained from proper environmental practices and efficient usage of petroleum products in the mining.

Jan 1, 2009

By I. Ashmole

The dimension stone industry is not widely known or appreciated within the mainstream mining industry. This is in spite of the fact that the industry has grown at an average of over 7% per annum since 1980, and is estimated to now have a global turnover in excess of US$ 60 Billion per annum. Production technologies, particularly in the developed world where labour costs are high, have developed rapidly over the past two decades. Aligned with this, there has been a significant trend in adoption of a more professional mining approach in the exploration for and operation of dimension stone quarries. In fact, in the experience of the authors, mining a dimension stone deposit successfully if often more challenging from a mining engineering point of view than many conventional surface mines. This paper gives an overview of the industry and then proceeds to discuss best practice in exploration for dimension stone and to outline the latest technologies applied in mining of dimension stone. These technologies are varied and the specific combination of technologies applied in any given quarry is determined by both the physical properties of the material as well as the influence of geology which significantly impacts on the recovery of saleable material and hence the economics of the quarry.

Jan 1, 2008

By N. Sinclair

"In open pit dozer bulk push operations, the material left resting against the highwall after blasting poses an issue. This is because dozers cannot physically get in behind the waste to begin the bulk pushing process. Instead, an excavator can be used to side-cast this waste for the dozers to access. An alternative technique is to have the dozers ‘side-cut’ the material, which involves the dozers running parallel to the wall, digging out the material, and eventually rotating their blades to begin bulk pushing. Industry practices suggest the latter technique is less productive and economical than using an excavator. However, such excavator sidecasting ‘economic viability’ assumes that smaller/ancillary type excavators are used (i.e. less than 23 m3 bucket capacity). So, what happens if some mine sites are restricted to using relatively larger excavators (> 23 m3 bucket) that are preferred for higher priority digging tasks? When can they avoid using their excavator? This paper explores multiple scenarios that have been designed and developed to simulate data results, which identify conditions in which the dozer side-cutting technique becomes more economically viable than excavator side-casting in terms of decreased unit cost per loose cubic metre. IntroductionOptimizing the cost of waste removal operations is important for the profitability of opencast coal mines. In the past decade, dozer bulk pushing has emerged and taken over from traditional waste removal operations such as dragline and truck-and-shovel methods at various sites around the world (Beatty, 1994). In a typical bulk push operation, once the bench has been blasted, waste is left resting against the highwall, which can either be cleared using a loading unit or by having the dozers ‘side-cut’ the highwall.Dozers perform most effectively when slot dozing side-by-side, perpendicular to the highwall. However, when dozers are required to remove material off the highwall, they must push parallel to the highwall, rather than perpendicular, hence ‘side-cutting’ the material to ensure a clean face. While dozer sidecutting is possible, it has been found that the majority of mine sites use a loading unit in this situation to avoid dozer inefficiency. Other perceived issues with dozer side-cutting include higher maintenance requirements and safety risks to dozer operators working in close proximity to the highwall."

Jan 1, 2019

By P. Otto, G. Borm, Th. Dickmann, F. Amberg, R. Giese

Based on many years experience, the well proven Swiss Tunnel Seismic Prediction System TSP has been substantially augmented for online geological prognosis in underground construction. In its latest version, the Integrated Seismic Imaging System ISIS provides high resolution seismic images of the rock mass around a tunnel face via an array of standard anchor rods. These rods contain 3D-geophones at their tips and can be readily installed during excavation work. A further innovative component of the system is the newly developed high-power repetitive source for application in hard rock: a pneumatic hammer with laser triggering to be mounted on construction machinery. A user-friendly software package permits online data acquisition and processing, 3D-visualization, and a first geological interpretation. Tomographic images of compressional and shear wave velocity fields at fault zones in metamorphic rock of the Gotthard Base Tunnel in the Central Alps are presented. Das langjährig bewährte Schweizer Tunnelseismische Vorauserkundungssystem TSP wurde inzwischen wesentlich weiterentwickelt. In seiner neuen Version, dem Integrierten Seismischen Imaging System ISIS, ermöglicht es hochauflösende seismische Abbildungen des Gebirges im Vorfeld und Umfeld einer Tunnelauffahrung mit Hilfe einer Anordnung von Felsankern, die an ihren Spitzen 3-Komponenten-Geophone enthalten. Eine weitere Neuerung von ISIS ist die pneumatische Hochleistungs-Impulsquelle mit Laser-Triggering. Eine benutzerfreundliche, interaktive Software ermöglicht die online Datenerfassung und -auswertung, 3D-Visualisierung und eine erste geologische Interpretation. Tomografische Abbildungen von Kompressions- und Scherwellengeschwindigkeitsfeldern an Störungszonen in metamorphem Gestein des Gotthard-Basistunnels werden gezeigt. Basé sur de nombreuses années d’expérience, le système suisse, bien établit, de reconnaissance sismique à l’avancement des tunnels (système TSP), a été sensiblement amélioré pour obtenir une prévision géologique en temps réel durant l’avancement de travaux souterrains. Sa dernière version, le Système Intégré d’Imagerie Sismique (ISIS), fournit des images sismiques haute-résolution du massif rocheux à l’avant d’un tunnel grâce à un réseau de tiges d’ancrage standard. Ces tiges, équipées à leur extrémité de géophones 3 composantes, s’installent très aisément durant les travaux d’excavation habituels. Le élément d’innovation récente concern le nouvelle source très répétitive et de forte puissance pour les applications aux roches dures: un marteau pneumatique déclenché par un système à laser. Un ensemble de programmes informatiques convivial permet l’acquisition et le traitement en temps réel des signaux et produit une vue 3D ainsi qu’une première interprétation géologique. Nous présenterons des images de réflexion d’ondes de compression et de cisaillement ainsi que des inversions tomographiques de zones de faille dans des terrains métamorphiques obtenues à l’occasion du creusement du tunnel de base du Gothard, dans les alpes centrales.

Jan 1, 2003

By F. A. G. M. Camisani-Calzolari

Approximately 850 groundwater samples were collected over a 29 300 km2 region of the semi-arid Northwestern Cape during the site selection phase of the South African radioactive waste disposal project. The purpose of the geostatistical investigation was primarily to delineate metallogenic occurrences and provinces which might exist below the thin veneer of surficial material and could thus interfere with the suitability of the site, and to quantify the distribution patterns of groundwater parameters in order to establish a relationship to local and regional geology. Up to 34 variables were analysed for each sample. Structural analysis revealed that the study area is statistically uniform. The variables have low correlation coefficients, with the exception of major ions, indicating a general poor degree of interrelationship between the spatial distribution patterns of the different variables. On the other hand, the long semivariogram range of the majority of variables, which reaches 70 km in cases, demonstrates their continuity on a regional scale. Kriging, which was repeated for each parameter, reveals that most variables, particularly trace metals, have distribution trends which are not influenced by local geomorphology or surface lithology. A 50 km wide, 220 km long metallogenic province, defined by kriging, could possibly reflect a broad metallogenic imprint on the basement and could represent a target area for prospecting. Kriging also reveals the possible existence of a wrench faulting system which may well have influenced the Namaqualand coastal graben and the western boundary of the Karoo.

Jan 1, 1987

By Kym L. Morton

Ground water and associated pore pressure represent elements which can have a negative impact on surface mining and slope stability. Ground water flow and deformation within a slope influence each other. An increase in pore pressure will result in a decrease of effective stress; and conversely if the pore pressure decreases, the effective stress increases. Slope analysis and slope design calculations require good information on pore pressure distribution around an open pit excavation. Until recently very little pore pressure data was available and assumptions had to be used. Location and design of measuring points depend on geological and structural setting, geotechnical domains and practicality. Good planning and the use of sensitive point piezometers to measure in situ pore pressures means that real-time data can be collected and used for the construction of flow nets, the determination of pore pressure distribution around an open pit mine, the validation of the dewatering/depressurization requirements, the calculation of the efficiency of the dewatering system and finally the use of pore pressure data in slope stability analysis. The recommended layout for a monitoring system, types and design of piezometers, data collection and use of the pore pressure data are presented.

Jan 1, 2008

By J. W. Neale

Mintek was a leading participant in the BioMinE project between 2004 and 2008. This project, which was funded in part by the European Commission, was aimed at the development of biotechnology for the minerals industry in Europe. Mintek?s research programme focused mainly on the development of integrated bioleach-based processes for the recovery of base metals from complex, low-grade sulphide concentrates. Specific European mineral resources were targeted and used in integrated piloting campaigns involving bioleaching, solution purification, and metals recovery. This paper describes the use of thermophilic bioleaching for the recovery of nickel and copper from a low-grade nickel-copper concentrate produced at the Aguablanca Mine in southern Spain. Currently, the Aguablanca Mine produces a bulk nickel-copper concentrate for sale to a smelter, and the proposition is to increase the profitability of the operation by the on-site production of metal or metal intermediate. Initially, bench-scale bioleach tests were conducted to determine the bioleach operating conditions. These tests included an evaluation of mesophilic, moderately thermophilic and thermophilic microorganisms. In order to achieve sufficiently high levels of both copper and nickel extraction, a thermophilic process was selected?this was necessary for leaching of the refractory chalcopyrite that occurs in this concentrate. Additional bench-scale test work was carried out to derive a conceptual process flowsheet for the solution purification and metals recovery circuit. The results of the bench-scale tests were used to design, construct and commission an integrated pilot plant, which was subsequently operated at Mintek for over seven months. During this time, the solution purification and metals recovery processes were optimized, and all recycle loops were closed. The final process flowsheet included the following unit operations: concentrate regrinding, thermophilic bioleaching at 70°C, primary iron removal using limestone, copper solvent extraction and electrowinning, secondary iron removal, nickel hydroxide precipitation using magnesia, and final solution purification using lime. Where applicable, process solutions were recycled to preserve water. The process design data derived from this pilot-plant campaign formed the basis for a conceptual engineering study for the developed process. In the study, mass and energy balances were derived, and a process flowsheet was developed and used as the basis for estimating the capital and operating costs of the process. This enabled a preliminary economic analysis of the process to be undertaken. The findings of this study are discussed.

Jan 1, 2009

By U. W. O. L Vogler

"The behaviour of rocks depends on their material properties, and therefore it is important that these properties are determined by relevant and reliable laboratory testing methods. The ISRM Suggested Methods are very important documents in this regard, and a draft suggested method exists for the determination of the ’complete stress-strain curve for intact rock in uniaxial compression’. The method specifies the required geometry of specimens and the required testing procedures. The research described in this paper involved the determination of complete stress-strain curves for two materials, one exhibiting the Class I characteristic, and the other the Class II characteristic. To obtain a better understanding of the deformation behaviours in the post-peak region, tests were carried out on specimens of both material types with different length-to-diameter ratios. The results showed that the geometries of the test specimens influence the stressstrain curves in the post-peak region. The implication is, therefore, that the numerical values obtained for the slopes of the post-peak graphs are not material constants, but are geometry-dependent. Explanations for this behaviour are given. These findings have important implications regarding the use of post-peak data, for example for blast fragmentation considerations, and for evaluation of rockbursting potential. The research findings are based on a limited amount of laboratory testing, and should be confirmed by further testing. IntroductionThe most common approach for studying the behaviour of rock is by compression testing of cylindrical specimens in the laboratory. Rocks respond to forces by deforming and eventually breaking. The strength and the deformation characteristics are derived from the stressstrain curves produced. Standard shapes and sizes for the test specimens and standard loading rates are recommended in the Suggested Methods of the International Society for Rock Mechanics (ISRM) and the American Society for Testing and Materials (ASTM) standards. In spite of these standards, there remain certain aspects of testing which require further attention. The research described in this paper deals with deformation and failure behaviour of rock materials using stiff, servocontrolled testing equipment. The particular objective was to test the premise that the behaviour of cylindrical rock specimens in the post-peak region of the stress-strain curves does not reflect only a material characteristic, but is influenced by the height-to-diameter ratio (the geometry) of the rock specimen. An additional objective was to investigate the effect of the stiffness of the test equipment on the outcomes of tests."

Jan 1, 2016

By M. Le Roux

The dewatering of coal, and particularly fine coal, continues to challenge coal prepatration engineers to find a cost-effective solution. With known world oil reserves being depleted daily, it is envisaged that the future price of coal may justify the use of thermal drying to achieve lower coal product moisture levels. The effect of exposure of the coal to elevated toemperatures on the mechanical strength of the coal was investigated. It was found that temperature does not play a major role in determining the volume breakage of a particle and that other variables such as orientation during impact has a much greater influence. A double breakage mechanism was reported during the grindability tests. Surface, as well as volume breakage, occurs for the first 4 minutes while only surface breakage takes place thereafter. Due to this double breakage action, it was found that exposure to temperature does play a role in the amount of breakage and breakage rates during grindability tests. It was also concluded that a particle will break to an optimum size due to impact, after which only its surface will grind away as it is subjected to breakage forces.

Jan 1, 2008

By A. S. Macfarlane

Western Deep Levels (North) is a deeplevel, longwall gold mine. Severe strata control problems and high rates of elastic closure, resulting in high rates of energy release, are associated with mining at depths of up to 3 500 metres. To assist in controlling these aspects of mine design and safety, a waste backfilling system has been designed and commissioned. The integration of such a system into an existing, producing longwall brings many problems of logistics, organization, planning and control. It is the purpose of this paper to examine these aspects of fill management, and to describe some of the practical problems involved with the integration of this project into the mining environment. Although many of the rock mechanics and soil mechanics aspects of backfilling systems are common there are specific problems involved which apply to longwall systems. Very strict guidelines are required for planning personnel to design their backfilling systems for a particular situation. These aspects are examined, and basic models developed which can be used without the necessity of comprehensive input from rock mechanics. A summary of the financial implications is included, and these are examined with regard to possible future applications and expansion of waste filling.

Jan 1, 1988