Over the last four years Potgietersrust Platinums (PPRust) has successfully implemented new geotechnical strategy and tactics to reduce risk, improving safety but also maximising profitability. A large database of core logging, face mapping and rock testing has been assembled and used in the slope design process. The data has also been used for optimising blast designs on a daily basis through the use of a geotechnical block model. This greatly improves blast fragmentation and therefore loading and milling efficiencies. Slope management includes a limit blasting programme, daily visual inspections, and state-of-the-art slope monitoring equipment, namely GroundProbe radar, Riegl lasers and GeoMoS automated prism monitoring. Slope optimisation incorporates all the field data, operational controls, cost of failure, full economic analysis of various slope angles and fault tree analysis. Savings on waste stripping of hundreds of millions of Rands were gained from the optimisation as slope angles could be increased due to improved geotechnical knowledge and management. PPRust’s geotechnical work is considered the benchmark for Anglo American open pit operations.

Student Number : 0112584H - MSc research project - School of Mining Engineering - Faculty of Engineering and the Built Environment / With the acquisition by AngloGold Ashanti Ltd of open pit mines in East and West Africa with possible addition of Greenfield and Brownfield operations, the emphasis of this research document was to improve the current open pit mines in this region. By identifying Mineral Resource Management (MRM) as a way to improve and manage operating practices, additional value and the accompanied risks have been identified. It was also realised that the current traditional, predominantly financial indicators are becoming increasingly inadequate, thus looking at alternative operating principles. Subsequent to this, proposals have been made to acquire the necessary production and cost change by integrating structure, strategy, systems, style, skills, staff and the defined goals as proposed in this document. Using a “process-based” approach integrating (best) operating practices, concepts such as: living out the company’s strategic values; a learning organisation; better informed decision-making; people management; self-directed teams; continuous improvement; asset and capital management; integrated information systems; and an improved internal and external customer relationship be obtained.

A fundamental problem in open pit mine planning is that of determining the optimum ultimate pit limits of the mine. These limits are that pit contour which is the result of extracting a volume of material which maximizes the difference between the value of extracted ore and the total extraction cost of ore and waste whilst satisfying certain practical operational requirements, such as. safe wall slopes. The determination of the optimum pit contour provides information which is essential in the evaluation of the economic potential of the mineral deposit.A number of optimization techniques have been proposed for determining the optimum pit contour. Of these techniques, those based on graph theory, linear programming and dynamic programming are mathematically rigorous, but only those based on graph theory are more suited to solving the three-dimensional problem. Unfortunately, direct application of these techniques to large ore- bodies may cause considerable difficulties because of the exceptionally high demand on computer storage and time requirements. Indeed, 25 years of research effort has not satisfactorily resolved these computational problems.A major contribution of the work presented in this thesis is the successful implementation of a system of techniques to solve the graph theoretic model, particularly when applied to large ore- bodies. A measure of this success is the fact that pits, as much as seven times larger may be designed with a given amount of computer storage, at a fraction of the time required by current software packages. The solution strategy presented involves the application of a modified Dinics Maximum Flow algorithm, together with an efficient data reducing technique. Computational results of these techniques applied on data from gold producing mines in Western Australia are used to demonstrate the success of this strategy.The relationships ++ / between the rigorous pit optimization techniques are also considered in this work. In particular, the Lerchs-Grossman graph-theoret ic method is shown to be stepwise equivalent to a modified version of the Dual-Simplex Linear Programming technique and not as efficient as the Network Flow method.

Commodity markets are fundamentally cyclical, exposing mining companies to large swings in profitability during periods of economic boom and bust. Although this is well documented, companies continue to produce mine plans based on present market conditions that fail to acknowledge long-term metal price variability. The purpose of this thesis is to adapt McIsaac’s (2008) mathematical model for determining the most robust underground mining plan under conditions of metal price uncertainty for application in an open pit environment. An overview of conventional open pit algorithms is given to demonstrate that a circular analysis precludes the determination of an optimal solution when metal prices are uncertain. Under the proposed methodology, the optimal solution is achieved by selecting the cutoff grade and production rate under stochastic metal prices such that the net present value and probability of a positive net present value are maximized. The mathematical model was formulated with costs represented as a function of the level of production, rate of production or both. Revenues are achieved from either a mill, heap leach or stockpile process dependent on the level of production and metal price in the year of consideration. Metal prices are generated annually according to a stochastic model that balances short-term volatility with long-term trends. The compiled cash flow model determines the optimal net present value for a given production profile under input metal prices. The feasible area of production is established based on mine life, resource and financing constraints. Net present values are generated for a broad search grid, which converges towards a unimodal solution according to a golden search algorithm. The process is then repeated many times in order to identify the production profile at which the optimal solution is repeatedly reached. As a visual representation, the solutions are plotted on a bubble graph where the size of the bubble corresponds to the frequency of the solution; the largest bubble is associated with the optimal solution. The methodology is tested on two massive copper porphyry deposits, contained within a single claim, for which a Preliminary Economic Assessment has been completed. / Thesis (Master, Mining Engineering) -- Queen's University, 2010-02-08 22:07:52.331

Magíster en Minería. Ingeniero Civil de Minas / Hoy en día, las minas a cielo abierto están siendo cada vez más profundas, lo que hace cada vez más atractivo el recuperar las reservas restantes mediante métodos subterráneos, tanto en las partes más profundas del pit como en sus zonas circundantes. Por lo tanto, estas operaciones han empezado a desarrollar nuevas estrategias para extraer el mineral mediante operaciones subterráneas. Para cuerpos masivos, los métodos más rentables son los que consideran el hundimiento de la roca, en particular, los métodos de block/panel caving, debido a sus bajos costos operacionales y alta productividad con respecto a otros métodos subterráneos de extracción. Las metodologías aplicadas para definir el periodo óptimo de transición desde la mina a cielo abierto a la subterránea son casi siempre limitados o sesgados, debido a que tienden a darle prioridad a la primera, que no necesariamente resulta en el VAN óptimo. En este trabajo, se propone una nueva metodología para maximizar el VAN basado en la secuencia de agendamiento para el caso conjunto cielo abierto a panel caving. Primero, se calculan las envolventes económicas para la mina a cielo abierto y la mina de panel caving, considerando potenciales pilares coronas entre ellos a modo de estabilidad. Después, se realiza el secuenciamiento de bloques y la maximización del VAN, considerando restricciones operacionales y geomecánicas para estudiar su influencia en el agendamiento. Este modelo de optimización ha sido aplicada tanto a modelos de bloques sintéticos y aquellos de escala minera. Los planes de producción, cambios en el periodo óptimo de transición, el secuenciamiento de los bloques, la alimentación a planta y las variaciones del VAN se analizan basados en los diferentes grupos de parámetros y variantes de extracción para suplir el ramp-up de la mina subterránea. Dichas variaciones en el caso de estudio tienen un impacto importante en el periodo óptimo de transición (pasando desde el año 31 hasta el año 50), enfrentando bajas importantes en la alimentación a planta en los planes de carácter secuencial durante la transición. El VAN, por su parte, no difiere de manera importante al analizar el proyecto desde su inicio (variación cercana al 1.2\% entre el peor y el mejor caso). Sin embargo, si se toma el año inicial para el análisis del VAN en un periodo posterior, como lo es el año 30 de la extracción, las diferencias son de mayor importancia (cercano al 93\% entre el peor y el mejor caso). Esta metodología es una herramienta que puede ayudar al planificador a observar diferentes casos durante la transición. Sin embargo, se recomienda incluir más componentes al modelo, como es la incorporación de un modelo geomecánico extenso tanto para la mina a cielo abierto como la subterránea, además de la integración de fases e interacción entre ellas en este primer método, y la integración de sectores o paneles en el segundo. / Este trabajo ha sido parcialmente financiado por CSIRO y AMTC

Modern large-scale open pit mines move hundreds of thousands of tonnes of material daily, from the loading sources to the destination zones, whether these are massive mine dumps or, to a lesser extent, to the grinding mills. Mine dumps can be classified as leach or waste dumps, depending upon their economic viability to be processed in-place, a condition that has experienced great progress in the last decades and has reconfigured the open pit haulage network with an increase in the number of dumps. Therefore, new methods for dump design optimization are of the highest priority in mine planning management. This paper presents a methodology to model and optimize the design of a dump by minimizing the total haulage costs. The location and design of these dumps will be given mainly by the geological characteristics of the mineral, tonnage delivered, topographical conditions, infrastructure capital and transportation costs. Spatial and physical design possibilities, in addition, provide a set of parameters of mathematical and economic relationship that creates opportunities for modelling and thus facilitates the measurement and optimization of ultimate dump designs. The proposed methodology consists of: (1) Formulation of a dump model based on a system of equations relying on multiple relevant parameters; (2) Solves by minimizing the total cost using linear programming and determines a "preliminary" dump design; (3) Through a series of iterations, changes the "preliminary" footprint by projecting it to the topography and creates the ultimate dump design. Finally, an application for a waste rock dump illustrates this methodology.

Surface mining is the most common mining method worldwide, and open pit mining accounts for more than 60% of all surface output. Haulage costs account for as much as 60% of the total operating cost for these types of mines, so it is desirable to maintain an efficient haulage system. As the size of the haulage fleet being used increases, shovel productivity increases and truck productivity decreases, so an effective fleet size must be chosen that will effectively utilize all pieces of equipment. One method of fleet selection involves the application of queuing theory to the haul cycle. Queuing theory was developed to model systems that provide service for randomly arising demands and predict the behavior of such systems. A queuing system is one in which customers arrive for service, wait for service if it is not immediately available, and move on to the next server or exit the system once they have been serviced. Most mining haul routes consist of four main components: loading, loaded hauling, dumping, and unloaded hauling to return to the loader. These components can be modeled together as servers in one cyclic queuing network, or independently as individual service channels. Data from a large open pit gold mine are analyzed and applied to a multichannel queuing model representative of the loading process of the haul cycle.  The outputs of the model are compared against the actual truck data to evaluate the validity of the queuing model developed. / Master of Science

Spoil pile stability in an open pit coal mine is a common problem and the Red Hills Lignite Mine in Choctaw County is no exception. The mine has had spoil stability problems of their spoil dragline bench since the beginning of their activity in 2002. They have managed to stabilize the conditions by installing prefabricated vertical drains (PVD) to consolidate the layers below the spoil dragline bench, which tended to fail due to an increase in pore water pressure. In this study, the capability of analyzing and predicting future pore water pressure conditions is examined. With the use of the stability model Slope/w and local stress calculations, the predictability of the necessity of PVDs and their spatial distribution are analyzed. The outcomes prove to be circumstantial to local pore water pressure and geology changes, therefore, the spacing between drains could be adapted to the local conditions potentially saving costs.

The Hamersley Province, located approximately 1200 km north of Perth, Western Australia forms part of the southern Pilbara craton, an extensive area of Band Iron Formations (BIF). The area has a high economic significance due to several enrichment stages of the country rock (BIF) resulting in several large high-grade iron ore deposits. Mount Whaleback near Newman and Mount Tom Price are the largest deposits, where reserves have been estimated at 1400 Mt and 900 Mt respectively. These ore bodies have been quantified as being high grade resources at approximately 64 % iron, with a high lump to fines ratio, and low impurities. The Mount Tom Price ore body is a hematite-rich ore, associated with a variety of shale and some dolomitic units (MacLeod et al., 1963, MacLeod, 1966, Taylor et al., 2001, Morris, 1980). The local hydrogeology of the Mount Tom Price area involves two main aquifer systems. The Dales Gorge member of the Brockman Iron Formation with contributions from the upper mineralised section of Footwall zone make up the main semi confined aquifer within the area. The underlying low permeability Mount McRae Shale and Mount Sylvia Shale lithologies separate a secondary aquifer which is located within the Wittenoom Formation. A dewatering program within Mount Tom Price has been ongoing since installation in 1994. Within the open pit mining industry, pits depths are increasingly being deepened as the easily accessible surface ore has been removed. This involves excavating pit walls below the existing groundwater table, which can lead to instabilities within pit walls. Added to this is the timing and economic considerations which need to be accounted for in a working mine. As dewatering and depressurisation are pivotal to the extraction of ore resources below the groundwater table, there can often be considerable time pressures to maintain planned mine developments (Hall, 2003). The South East Prongs pit, located within the Mount Tom Price mine, holds some of the most valued low impurity, high grade hematite ore. Structurally the South East Prongs is unique as the deposit lies in the base of a steeply dipping double plunging syncline, intersected by the Southern Batter Fault which runs parallel in strike to the Turner Syncline. The current pit floor of South East Prongs is located at 600 mRL. The long term development plan for the western end of this pit includes a further 30 m of excavation to a final depth of 570 mRL. This currently poses a number of stability issues that require resolution before any development can be undertaken. A conceptual understanding of flow dynamics within structurally complex wall rock environment has been generated through the utilisation of finite element numerical modelling. The complex structural setting within the northern wall of the South East Prongs has shown to interact with high conductivity lithologies to promote preferential flow of groundwater from the underling Wittenoom Formation aquifer. Recharge to the semi confined DG aquifer occurs as groundwater travels up shear zones within the South East Prongs Fault Zone before migrating along Brunos Band. An investigation into alternative methods of depressurisation has been recommended to ensure the ongoing management of pore water pressures within the northern pit wall during planned pit cut backs. Limiting recharge from the WF to the pit through stated preferential flow paths has been identified as a potential issue when the remaining DG aquifer is removed. Maintaining the proposed dewatering buffer will be difficult to achieve using the current system. The ability to design optimal pit shells for access and ore recovery as well as an effective dewatering and depressurisation system relies heavily on the a sound geological model. Further to this, time allocations to ensure forward planning deadlines are met can be significantly interrupted if adjustments to initial plans are required.

Este estudo apresenta, de forma sistemática, a importância da infraestrutura de mina a céu aberto, determinando as atividades principais dessa fase e os impactos e benefícios causados por alterações na forma de execução, medidos através de indicadores de produtividade e resultados financeiros. Algumas atividades principais como a reconfiguração das faces dos bancos de lavra pela aplicação comparativa de desempenho de trator de esteira e retroescavadeira; o estabelecimento de padrão para o dimensionamento das camadas estruturais e funcionais das estradas de mina; a mensuração dos benefícios da construção e manutenção das estradas, no desempenho dos caminhões e dos tratores de esteira, através de estudos de caso e demonstrar que a aplicação de técnicas adequadas modificam o resultado operacional. A metodologia utilizada aborda a relevância da infraestrutura e da frota de equipamentos auxiliares dentro do ciclo operacional, propondo uma aplicação correta e sistemática, baseada na demanda e nas atividades auxiliares que proporcionam condições operacionais para as atividades "que geram valor", suportando o cumprimento das metas estabelecidas no plano de produção. Os principais resultados obtidos vão desde a melhoria da segurança operacional, da imagem da empresa, do resultado financeiro, ao melhor aproveitamento dos recursos minerais, impactando diretamente a sustentabilidade do negócio. Através dos casos abordados neste trabalho, conclui-se que o desempenho da mineração a céu aberto é fortemente dependente do foco dado à infraestrutura de mina, ou seja: da qualidade das pistas, adequação das praças de carregamento, condição operacional de pilhas de estéril ou minério, drenagem superficial, dos métodos de trabalho e da disciplina operacional, gerando ganhos e/ou perdas que vão de unidades de porcentagem a várias vezes a capacidade do processo abordado. / This study presents, in a systematic way, the importance of the infrastructure in the open pit mining, determining the main activities of this operation and the impacts and benefits from changes implemented measured by operating productivity indicators and financial results. Some major activities such as the reconfiguration of the slope faces by the comparative performance of bulldozer and backhoe; the establishment of standards for the design of structural and functional layers of the mine haul roads; measure the benefits of the construction and maintenance of roads, the performance of trucks and bulldozers, through case studies show that the application of appropriate techniques can modify the operating result. The methodology addresses the importance of infrastructure and auxiliary equipment fleet in the operating cycle, proposing a correct and systematic application, based on demand and auxiliary activities that provide operating conditions for activities "that create value", supporting the achievement of the goals established in the production plan. The main results ranging from improved operational safety, company image, financial results, the best use of mineral resources, directly impacts on the business sustainability. Through the cases discussed in this work, it is concluded that the performance of the open pit mining is strongly dependent on the focus given to the mine infrastructure wich means, the quality of the tracks, adequacy of the loading spots, operating condition of waste dumps or ore bins, surface drainage, working methods and operational discipline, generating gains and/or losses ranging from small amounts to several times the capacity of the covered process.