Dissertations / Theses on the topic 'Open pit mine design and planning'

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.

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.

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.

A graph theory oriented algorithm for optimal ultimate pit limit design is developed. Mathematical proofs of optimality and convergence are given. The algorithm works on a 3-D block mine model and formulates the model into a directed graph consisting many trees. The vertices in the graph are identified with the blocks in the model and the imposed arcs in the graph represent pit slope constraints. The formation of each directed tree is based more on the ore-waste support concept than geometric constraints alone. The algorithm efficiently handles the joint support and re-allocation problems. The theoretical proof shows that the new algorithm is consistently faster than the well known Lerchs-Grossmann's (LG) algorithm, which is the only algorithm developed in the past one-quarter century capable of producing a true optimum pit limit. The case study results show that the new algorithm is able to generate the optimal ultimate pit limit for a model with 80 columns x 80 rows x 40 levels on an IBM PC AT 80286 microcomputer in 115 minutes. The indirect comparison was made between the results of the new algorithm and the results obtained by P. Huttagosol (1988, 1989) using the LG algorithm. P. Huttagosol optimized a smaller mine model than the one optimized by the new algorithm in 535 minutes of VAX8600 CPU time. The comparison between 535 minutes of VAX8600 CPU time for a smaller model with 115 minutes PC AT processing time for a bigger model clearly indicates that the new algorithm is significantly faster than the LG algorithm. This study also investigates both proposed mathematical optimization approaches and the popular trial and error "pushback" approach to long range mine planning. Both the theoretical analysis and numerical examples demonstrate it is impossible to obtain the optimal solution to mine production scheduling by the approach combining the Lagrangian relaxation with the ultimate pit limit algorithm. The non-convergence due to redundant optimal solutions and the non-convergence due to the requirement of advanced stripping are identified with the proposed approach. The investigation clarifies the long-time misunderstood concept and proves the impossibility of such a research direction itself. Finally, some problem solving techniques which play important roles in the computerized mine planning and grade control are developed and discussed. Specifically, they are: (1) point-in-polygon algorithm, (2) polygon area algorithm, (3) polygon clipping algorithm, (4) blast hole data collection, validation and database maintenance, and (5) the interactive graphics ore-waste delineation.

Magíster en Minería. Ingeniero Civil de Minas
La geomecánica y planificación minera son áreas de la minería a cielo abierto íntimamente relacionadas, ya que las restricciones geomecánicas limitan al diseño minero y, así, los planes mineros factibles. El diseño y los planes mineros han de empujar los límites de lo que la geomecánica permite, para asegurar operaciones mineras competitivas y mantener un nivel de riesgo al personal y operaciones aceptable. Luego, se requiere del monitoreo geotécnico para adquirir datos de calidad que permitan un diseño minero de alto nivel. Sin embargo, la relación entre geomecánica y planificación minera no se extiende al diseño e implementación de programas de monitoreo. En general, los programas de monitoreo de deformaciones superficiales son diseñados con posterioridad al inicio de la operación del rajo y cuando se han identificado signos de inestabilidad en la superficie de los taludes. El monitoreo de deformaciones del subsuelo permite alertar sobre fallas en desarrollo semanas antes de que estas se hagan notar en superficie. Luego, se debería diseñar campañas de monitoreo de deformaciones del subsuelo durante el proceso de planificación minera, considerando el diseño minero en la instalación de instrumentos geotécnicos previo a la construcción de la mina. Lo que permitiría registrar el proceso de relajación del macizo a medida que la construcción progresa y adquirir datos más exhaustivos del comportamiento del macizo rocoso (antes que con monitoreo superficial), con el fin de optimizar el diseño de taludes futuros y adoptar medidas correctivas para evitar fallas. En esta tesis, fueron diseñadas una serie de campañas de monitoreo de deformaciones del subsuelo usando In-Place Inclinometers, ShapeAccelArrays y Networked Smart Markers (NSMs) como equipos de monitoreo. Las opciones fueron aplicadas a una mina teórica desarrollada como parte de la tesis y comparadas en términos de costos, cantidad y calidad de los datos recopilados. Los resultados indican a la opción de NSMs cada 2[m] como la más eficiente en cuanto a costos ya que: (1) presenta el menor costo por unidad de datos adquiridos (US$57.21) y (2) 5 veces mayor vida útil, lo que permitiría obtener el doble de datos que la siguiente mejor opción, (3) se financia con un aumento de 2° en el ángulo de talud y (4) aumenta el VAN del proyecto en 3.2%.
Open pit geomechanics and mine planning are two closely related areas in the development of an open pit mine since geotechnical constrains limit the possible mine designs and, thus, the feasible mine plans. Mine designs and plans have to push the limits of what rock mass geomechanics allow to assure competitive mine operations, while maintaining acceptable levels of risk to operations and personnel. Therefore, geotechnical monitoring programs are required to acquire good quality data to be used as input for mine design. However, the relation between geomechanics and mine planning does not extend to monitoring programs design and implementation. Generally, surface deformation monitoring programs are designed after the project is in operation and signs of slope instability have been identified on the surface. Subsurface deformation monitoring can alert about developing failures weeks before any sign of instability is noted on the surface. Therefore, subsurface deformation monitoring campaigns should be designed along the mine planning process and considering the mine s design to install geotechnical instrumentation prior to the construction of the slopes. This methodology would allow to register the rock mass relaxation process as construction progresses and to acquire more comprehensive data about rock mass behaviour, in advanced of surface monitoring, towards future slope design optimization and adoption of remedial measurements to avoid failure. In this thesis, a series of subsurface deformation monitoring campaign were designed using In-Place Inclinometers, ShapeAccelArrays and Networked Smart Markers as monitoring devices. All options were applied to a theoretical open pit developed as part of this work. The campaigns were compared in terms of cost, quantity and quality of gathered data. The results showed that the campaign using NSMs installed every 2 meters was the most cost-efficient option as it represented: (1) the lowest cost per unit of gathered data (US$57.21), (2) five times longer lifespan, which allowed to gather twofold the amount of data compared with the next best option, (3) be financing of the campaign through steepening of the slopes by 2° and (4) increase in project s original NPV by 3.2%.

Open pit mine operations are complex businesses that demand a constant assessment of risk. This is because the value of a mine project is typically influenced by many underlying economic and physical uncertainties, such as metal prices, metal grades, costs, schedules, quantities, and environmental issues, among others, which are not known with much certainty at the beginning of the project. Hence, mining projects present a considerable challenge to those involved in associated investment decisions, such as the owners of the mine and other stakeholders. In general terms, when an option exists to acquire a new or operating mining project, , the owners and stock holders of the mine project need to know the value of the mining project, which is the fundamental criterion for making final decisions about going ahead with the venture capital. However, obtaining the mine project’s value is not an easy task. The reason for this is that sophisticated valuation and mine optimisation techniques, which combine advanced theories in geostatistics, statistics, engineering, economics and finance, among others, need to be used by the mine analyst or mine planner in order to assess and quantify the existing uncertainty and, consequently, the risk involved in the project investment. Furthermore, current valuation and mine optimisation techniques do not complement each other. That is valuation techniques based on real options (RO) analysis assume an expected (constant) metal grade and ore tonnage during a specified period, while mine optimisation (MO) techniques assume expected (constant) metal prices and mining costs. These assumptions are not totally correct since both sources of uncertainty—that of the orebody (metal grade and reserves of mineral), and that about the future behaviour of metal prices and mining costs—are the ones that have great impact on the value of any mining project. Consequently, the key objective of this thesis is twofold. The first objective consists of analysing and understanding the main sources of uncertainty in an open pit mining project, such as the orebody (in situ metal grade), mining costs and metal price uncertainties, and their effect on the final project value. The second objective consists of breaking down the wall of isolation between economic valuation and mine optimisation techniques in order to generate a novel open pit mine evaluation framework called the ―Integrated Valuation / Optimisation Framework (IVOF)‖. One important characteristic of this new framework is that it incorporates the RO and MO valuation techniques into a single integrated process that quantifies and describes uncertainty and risk in a mine project evaluation process, giving a more realistic estimate of the project’s value. To achieve this, novel and advanced engineering and econometric methods are used to integrate financial and geological uncertainty into dynamic risk forecasting measures. The proposed mine valuation/optimisation technique is then applied to a real gold disseminated open pit mine deposit to estimate its value in the face of orebody, mining costs and metal price uncertainties.

Over recent years, new methods have been developed to integrate uncertainty into the optimization of life-of-mine (LOM) production planning. This thesis makes use of two stochastic optimization methods: simulated annealing (SA) and stochastic integer programming (SIP); which are implemented in the context of the requirements of mining applications through the use of stochastic simulation to model uncertainty. For the case of SA, the second chapter of the thesis documents the case of a copper deposit where ten simulated realizations are sufficient to provide stable LOM optimization results. In addition, the study shows that the selected true optimal pit limits are larger than the ones derived through conventional optimization. Stochastically optimized pit limits are found to be about 17% larger, in terms of total tonnage, than the conventional (deterministic) optimal pit limits. The difference adds one year of mining and approximately 10% of additional net present value (NPV) when compared to the NPV of conventional optimal pit limits and a production schedule generated stochastically with the same SA algorithm. In the third chapter of the thesis, the SIP based optimizer is used with the purpose of integrating uncertainty into the process of pushback design. Results show the sensitivity of the NPV to the design of starting and intermediate pushbacks, as well as the pushback design at the bottom of the pit. The new approach yielded an increment of ~30% in the NPV when compared to the conventional approach. The differences reported are due to the different scheduling patterns, the waste mining rate and an extension of the pit limits which yielded an extra ~5.5 thousand tonnes of metal.
Depuis quelques années, de nouvelles méthodes ont été développées pour intégrer l'incertitude dans l'optimisation de la planification de la production de la vie-de-mine i.e. life-of-mine (LOM). Cette thèse se sert de deux méthodes d'optimisation stochastique : recuit simulé (RS) et programmation en nombres entiers stochastique (SIP); les deux méthodes sont programmées dans le cadre des besoins des applications d'exploitation de la simulation stochastique et modélisation d'incertitude. Pour le cas de RS, le deuxième chapitre de la thèse décris le cas d'un dépôt de cuivre où dix réalisations simulées sont suffisantes pour fournir des résultats stables d'optimisation de LOM. En outre, l'étude prouve que les véritables limites optimales choisies de mine sont plus grandes que celles dérivées par l'optimisation conventionnelle. Des limites stochastiquement optimisées de mine s'avèrent environ 17% plus grandes, en termes de tonnage total, que les limites optimales (déterministes) conventionnelles de mine. La différence ajoute un an d'exploitation et approximativement 10% de valeur nette additionnel (NPV) une fois comparée au NPV des limites optimales conventionnelles de mine et une cédule de production produit stochastiquement avec le même algorithme de RS. Dans le troisième chapitre de la thèse, l'optimiseur basé sur SIP est utilisé en vue d'intégration de l'inceritude dans le processus de la conception de fosses emboîtées. Les résultats montrent la sensibilité du NPV à la conception de fosses emboîtées de commencement et intermédiaires aussi bien que la conception de la fosse emboîtée du fond de la mine. La nouvelle approche a produit une augmentation de ~30% dans le NPV une fois comparée à l'approche conventionnelle. Les différences rapportées sont dues aux différents cédules de production, du taux de décapage du stérile et d'une extension des limites de la mine qui ont produit ~5.5 mille tonnes supplémentaires

An algorithm which adopts a moving cone approach but is guided by maximal network flow principles is developed. This study argues that from a network flow point of view, the re-allocation problem is a major obstacle to prevent a simulation oriented pit design algorithm from reaching the optimum solution. A simulation oriented pit design algorithm can not resolve the re-allocation problem entirely without explicit definition of predecessors and successors. In order to preserve the advantages of moving cone algorithm and to improve the moving cone algorithm, the new algorithm trys to avoid the re-allocation situations. Theoretical proof indicates that the new algorithm can consistently generate higher profit than the popular moving cone algorithm. A case study indicates that the new algorithm improved over the moving cone algorithm (1% more profit). Also, the difference between the new algorithm and the rigorous Lerchs-Grossmann algorithm in terms of generated profit is very insignificant (0.015% less). The new algorithm is only 2.08 times slower than the extremely fast moving cone algorithm. This study also presents a multi-period 0-1 programming mine sequencing model. Once pushbacks are generated and the materials between a series of cutoffs are available for each bench of every pushback, the model can quickly answer, period by period, what is the best (maximum or minimum) that can be expected on any one of these four items: mineral contents, ore tonnages, waste tonnages and stripping ratios. This answer is based on a selected cutoff and considers the production capacity defined by the ore tonnage, the desired stripping ratio and the precedence constraints among benches and pushbacks. The maximization of mineral contents is suggested to be the direct mine sequencing objective when it is permissible. Suggestions also are provided on how to reduce the number of decision variables and how to reduce the number of precedence constraints. A case study reveals that the model is fast and operational. The maximization of mineral contents increases the average grades in early planning periods.

The mine production schedule defines the sequence of extraction of selected mine units over the life of the mine, and consequentially establishes the ore supply and total material movement. This sequence should be optimized so as to maximize the overall discounted value of the project. Conventional schedule approaches are unable to incorporate grade uncertainty into the scheduling problem formulation and may lead to serious deviations from forecasted production targets. Stochastic mine production schedulers are considered to obtain more robust mine production schedule solutions.
The application of stochastic approaches to the mine production schedule problem is recent and additional testing is required to better understand these tools and to define the value of a stochastic solution as compared to the conventional result. Two stochastic schedulers are tested in a low-grade variability copper deposit, optimization parameters are discussed and their results compared with a conventional schedule.
The first method uses a stochastic combinatorial optimization approach based on simulated annealing to address the mine production schedule problem. The method aims for maximization of the net present value (NPV) of the project and minimization of deviations from the production targets. These objectives are attained by incorporating grade uncertainty into the mine production schedule problem formulation. The second method formulates the problem as a stochastic integer programming problem, in which the objective is the maximization of the projects' NPV and the minimization of production targets deviations. The model can also manage how the risk of deviating from the targets is distributed between production periods.
Both stochastic approaches were tested in a low-grade variability copper deposit. In both case studies, the value of a stochastic solution is demonstrated to be higher than the conventional one. This fact demonstrated the misleading results that a conventional schedule may produce and shows the importance of not ignoring the presence of uncertainty when defining the mine production schedule for a project.

Magíster en Minería. Ingeniero Civil de Minas
El diseño de taludes es una tarea crítica en proyectos de minería a cielo abierto. Generalmente, planificadores y diseñadores buscan operar en paredes tan empinadas como sea posible para optimizar la cantidad de mineral extraído y reducir el lastre. Sin embargo, esto conlleva una disminución en la estabilidad del talud. De este modo, se requiere una gestión adecuada del talud para permitir a los planificadores y operadores realizar su trabajo con seguridad. Una de las principales variables que debe ser manejada adecuadamente en minas a cielo abierto es la presión de poros que se genera detrás de los taludes ya que esta presión disminuye la resistencia al corte del suelo. Para controlar la influencia de la presión de poros se han desarrollado distintos tipos de instrumentos para monitorear presión de agua en minas y usar los datos obtenidos como input en la toma de decisiones. Entre los instrumentos desarrollados para monitorear presión de agua subterránea están los piezómetros, que se han convertido en tecnologías establecidas en proyectos civiles y mineros. Existen distintos tipos de piezómetros y entre ellos la tecnología más aceptada para realizar monitoreo de agua en minas es la de Vibrating Wire Piezometer (VWP). En esta tesis se desarrollaron lineamientos para seleccionar instrumentación basada en las características de una mina. Utilizando estos lineamientos se seleccionaros dos tecnologías para ser comparadas, los VWP y los Networked Smart Markers (NSM). Esta comparación involucra el desarrollo de un proyecto minero teórico que incluye empinar una pared potencialmente inestable de la mina como contexto para el uso de los instrumentos. Posteriormente, se desarrollaron lineamientos para integrar un programa de monitoreo al plan minero. Para comparar dichas tecnologías, se proponen dos programas de monitoreo equivalentes y se consideran los costos de los equipos para ser instalados en los años 3 y 13 del plan minero. Un análisis de pits anidados reveló que el VAN del proyecto aumenta a medida que la pared se empina, de este modo, el parámetro de control en la comparación es cuál programa es más barato al tomar en cuenta el ingreso extra y una tasa de descuento del 8% para calcular el VAN. Los resultados de esta comparación mostraron que el uso de VWP es más barato que el uso de NSM (600,015.5[US$] versus 766,142.5[US$]). Sin embargo, esta diferencia en costo es pequeña considerando la escala del proyecto (0.39% de la inversión), además empinar la pared generó 42,420,000[US$] extra al VAN original del proyecto, lo que hace que ambas alternativas sean factibles para llevar a cabo el monitoreo propuesto. Los NSM sin embargo poseen una ventaja para realizar mediciones multipunto ya que permiten un mayor número de puntos de muestreo en un mismo pozo.
Slope design is one of the most critical tasks in open pit mine projects. Generally, mine planners and slope designers aim to operate on walls as steep as possible to optimize the amount of ore retrieved from the mine while reducing the extracted waste. However, this approach also involves a reduction in overall slope stability. Consequently, a proper management of slope stability is required to assist mine planners and operators to perform their work safely. One of the main variables that need to be properly managed in open pit mines is the pore water pressure generated behind the slopes, as this pressure decreases the ground s shear strength. To manage the influence of pore water pressure, several geotechnical instruments have been developed over the years to monitor pore water pressure and to use the data to make proper decisions. Piezometers are devices developed to monitor groundwater pressure that have become established technologies to measure pore water pressure in civil and mining projects. There are different types of piezometers with varying characteristics. The most accepted sensing technology for pore pressure monitoring in mines is the Vibrating Wire Piezometers (VWP). This thesis developed guidelines for the selection of instrumentation given the characteristics of a mine site. Using those guidelines, Vibrating Wire Piezometers and the emergent technology of Networked Smart Markers (NSM) were selected to be compared. For this comparison, a theoretical mine project, that included the steepening of a potentially unstable wall, was developed as context for instrumentation use. Subsequently, guidelines for the integration of a pore water pressure monitoring program into the mine plan were developed. To compare the selected technologies, two equivalent monitoring programs were proposed considering the current installation costs of the devices and installations in years 3 and 13 of the mine life. A nested pit analysis revealed that the NPV of the project increases when the wall gets steeper, therefore, the parameter of interest is which program is less expensive compared to the extra income, considering a discount rate of 8% to calculate the NPV of the project. The results of this comparison showed that the use of Vibrating Wire Piezometers was less expensive than the NSMs (600,015.5[US$] against 766,142.5[US$]). However, this difference in cost is small in terms of the scale of this project (0.39% of the investment) and the steepening of the wall generated 42,420,000[US$] extra to the NPV of the original project, thus, making both alternatives feasible to perform the proposed monitoring. NSMs are, however, more suitable to perform multi-point readings as they allow a higher number of measurement points in a single borehole.

Com o passar dos anos a sociedade tem se tornado gradativamente mais dependente de recursos minerais para o seu funcionamento e para o desenvolvimento de produtos. A maior parte das coisas que cercam o homem necessita de alguma espécie de bem mineral como matéria prima para sua fabricação. Por isso, cada vez mais, a mineração tem sido objeto de estudos, buscando aprimoramento e desenvolvimento nos métodos de extração de minérios. Existem duas formas utilizadas para a extração de bens minerais, uma por uso de métodos de lavra a céu aberto (OP) e outra através da aplicação de métodos para lavra subterrânea (UG). A definição de qual método deve ser aplicado em cada caso depende de diversos fatores, como profundidade e geometria do corpo mineral, competência da rocha portadora do minério e da rocha encaixante, entre outros, mas ao final, aspectos econômicos predominam para a definição da viabilidade de cada um dos possíveis métodos. Porém, existem casos em que a melhor escolha para minerar o depósito não se dá por umas dessas duas opções, e sim, pela combinação de ambas, ou seja, a aplicação da lavra a céu aberto seguida da extração dos recursos remanescentes por lavra subterrânea. A grande dificuldade, nestes casos, é definir qual o momento ideal para a transição de método, de maneira que os resultados do projeto integrado sejam otimizados e que um método não inviabilize o outro. Para isso é necessário analisar as duas opções de lavra individualmente, lavrando somente a céu aberto e lavrando somente por métodos subterrâneos, além de analisar-se a viabilidade do projeto através da combinação dos dois métodos, comparando as opções técnica e economicamente e selecionando a que apresente a melhor resposta ao final, para então tomar-se a decisão de qual alternativa de projeto é o mais indicado para cada caso.
Over the years, the society has become progressively dependent on mineral resources for its operation and for development of products. The majority of the things that surround the men needs some kind of mineral material as raw material for its manufacture. Therefore, increasingly, mining has been studied aiming to improve and develop methods of mineral extraction. There are two ways that are utilized to mineral extraction, one by open pit methods (OP) e another by application of underground methods (UG). The definition of which one should be applied in each case depends on many factors, such as depth and geometry of the mineral body, strength of the mineralized and bounding rock, among others, but at the end, economic aspects are predominant for the definition of viability of the methods. However, there are some cases where the best choice to mine the deposit is not one of these options, but the combination of both methods, it means, the application of open pit mining followed by extraction of remaining resources by underground mining. The great challenge, in these cases, is to define what is the right moment for the transition of the methods, making sure that the results are optimized and one method do not impede the development of the other one. In this sense, it is necessary to analyze both options individually, mining the deposit only by open pit and mining only by underground, and also analyze the combination of the two methods, comparing these options technically and economically at the end, and then decide which project alternative is the best for each case.

La nécessité de maximiser la récupération d'une ou plusieurs espèces utiles d'un gisement du cuivre, l'optimisation des consommations d'additifs dans le processus de traitement métallurgique, savoir où laisser les matériaux qui dans le futur pourraient être valorisés par une série de nouvelles opérations etc., conduit à adapter la planification minière aux caractéristiques géologiques et métallurgiques du gisement.Les unités géo-métallurgiques sont déterminées par une combinaison des principaux paramètres géologiques, type de roche, altération, minéralisation, etc. Chaque unité présente un comportement différent au processus de traitement métallurgiques avec des caractéristiques de récupération et de consommation d'acide bien spécifiques.D'une façon générale, on peut définir la planification de la mine comme un outil permettant de faire la liaison entre la géologie et la métallurgie, non seulement selon des paramètres économiques et de teneurs, mais aussi selon des paramètres géologiques et métallurgiques.Pour pouvoir construire le modèle géo-métallurgique ou géo-minier métallurgique (G.M.M) ainsi que mettre en oeuvre la catégorisation des ressources, nous avons utilisé des outils géostatistiquesLe fait de disposer d'un modèle G.M.M est d'une grande aide pour la définition de la fosse finale et la planification à long terme, soit simplement comme une première approche de la réponse du gisement au processus de traitement métallurgique, mais surtout pour optimiser les coûts et définir différentes alternatives pour maximiser la récupération du métal.Cette étude a été appliquée au cas du gisement stratiforme de Cu et Ag de Mantos de la Luna situé dans le Nord du Chili. Il comporte en particulier une comparaison entre l'approche traditionnelle et l'approche qui intègre le concept du modèle G.M.M. qui porte principalement sur les teneurs de coupure. Le concept G.M.M. peut donc influencer les décisions stratégiques comme les décisions opérationnelles.

M.Ing. (Engineering Management)
The design of the optimum open pit slope angle is one of the major challenges during open pit mine planning, as it implies attaining the ideal balance between utilizing the maximum slope angle whilst achieving acceptable stability and safety standards as indicated by the mine. The aim of open pit mines should thus be to seek the steepest possible slope angle without compromising the safety of the personnel, equipment or ore reserves, utilizing both stability analyses as well as risk assessments. The typical open pit mine plan aims to achieve an acceptable balance between operational risks and geotechnical design considerations by analysing factors such as the slope stability design, the rock mass properties and existing structural geological conditions. These factors are used as inputs towards an optimum slope angle design which will be used in the final pit design and aims to provide maximum economic viability to the mine. The risk analysis methodology aims to improve traditional slope design methods and is used to evaluate risks and failure consequences in terms of economic impacts. The economic impact analysis is a useful method in comparing the performance of various mine plans and slope designs. The risk analysis methodology thus provides a valuable indication of optimum slope design configurations and as such can be a great asset to the mine design process. This research paper aims to identify the key risks used as input to an open-pit mine plan in a feasibility stage and to define an approach to minimize these risks in order to achieve maximum economic benefit. The effectiveness of this approach will be evaluated by means of a case study which will attempt to achieve an optimum balance between value and risk, and to compare the magnitude of the economic impact of an individual risk with the probability of occurrence of said risk. The case study will utilise a risk map in order to define years with higher economic impacts as well as defining critical pit areas causing these risks, so as to identify areas requiring further investigation which will assist the mine in evaluating mitigation strategies in order to reduce overall risk.

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

Mining operations exploit mineral deposits, processing a portion of the extracted material to produce salable products. The concentration of valuable commodities within these deposits, or the grade, is heterogeneous. Not all material has sufficiently high grades to economically justify processing. Cut-off grade is the lowest grade at which material is considered ore and is processed to create a concentrated commodity product. The choice of cut-off grade at a mining project can be varied over time and dramatically impacts both the operation of the mine and the economics of the project. The majority of literature and the accepted industry practices focus on optimizing cut-off grade under known commodity prices. However, most mining operations sell their products into highly competitive global markets, which exhibit volatile commodity prices. Making planning decisions assuming that a given commodity price prediction is accurate can lead to sub-optimal cut-off grade strategies and inaccurate valuations. Some academic investigations have been conducted to optimize cut-off grade under stochastic or uncertain price conditions. These works made large simplifications in order to facilitate the computation of a solution. These simplifications mean that detailed mine planning data cannot be used and the complexities involved in many real world projects cannot be considered. A new method for optimizing cut-off grade under stochastic or uncertain prices is outlined and demonstrated. The model presented makes use of theory from the field of Real Options and is designed to incorporate real mine planning data. The model introduces two key innovations. The first is the method in which it handles the cut-off grade determination. The second innovation is the use of a stochastic price model of the entire futures curve and not simply a stocastic spot price model. The model is applied to two cases. The first uses public data from a National Instrument 43-101 report. The second case uses highly detailed, confidential data, provided by a mining company from one of their operating mines.
Thesis (Master, Mining Engineering) -- Queen's University, 2012-04-30 22:36:51.257

In the last decade mineable oil sands production in Canada has grown rapidly. Constraints on the planning and design processes employed by surface mining oil sands operations vary in distinct ways from other commodities mined by both hard and soft rock open pit methods. The unique waste handling needs, including tailings disposal, of contemporary oil sands mining requires specific planning considerations. It is the purpose of this research to analyze and document a conventional hard rock, metal mine planning system, and contrast this with the unconventional mine planning system used by oil sands mines. Systems activity models of both the conventional and unconventional systems are developed in support of documenting and contrasting the two systems. Constraints unique to oil sands mine planning are identified and their impact on the oil sands mine planning system are documented. The impacts of challenging waste handling and storage requirements and a uniquely prescriptive regulatory environment defining mineable ore are identified as key constraints. The research concludes with a proposal for a new planning system to better support the planning of oil sands mines. The proposed system respects the unique waste management considerations in oil sands planning and revisits the current regulatory approach to ensuring resource recovery. The proposed system is compatible with traditional approaches to economic analysis in open pit planning, and with emerging best practices to manage technical and economic uncertainty, improve project optimization, and develop robust mine plans.
Thesis (Ph.D, Mining Engineering) -- Queen's University, 2012-10-02 17:52:18.223

The implications of comminution practices on the planning of a typical open pit mine was investigated in this study by means of computer simulation. The objective was to assess the effects of mining costs as well as processing costs on the production plan of a typical open pit mine. For the purpose of the research, MineLib, an open library of ore body models was consulted. This led to the selection of a copper-gold ore body named “Newman1” for use in the strategic mine optimisation. Various scenarios were considered in order to highlight the contribution of comminution costs to the mine plan. In all the simulated scenarios, the objective function was to maximise the Net Present Value (NPV). And in terms of simulation setup, the comminution costs and cut-off grades were systematically varied from 70 % to 140 %. It was hence possible to investigate their effects on the NPV of the Newman1 ore body using SimSched, a freeware for mine optimisation and planning. Results showed that there is a great opportunity to increase the NPV of the Newman1 block model by adjusting the contribution of processing costs in general and comminution costs in particular. This can be achieved for instance by controlling the policy of cut-off grades, lowering production costs, and increasing throughput.
Civil and Chemical Engineering
M. Tech. (Chemical Engineering)

A research report submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science in Engineering
This research sought to address the influence posed by the pit wall stability and instability on underground planning and design when transitioning from open pit to underground. Conventionally, empirical methods are used and they sometimes lack consideration of rock mass behaviour, groundwater effects, structures as well as geological considerations. This can potentially result in massive failures of pit slopes and subsequent loss of infrastructure, excavations, loss of machinery and human lives. It was against this background that this research sought to reduce mining exposure to the above mentioned hazards. In line with the aims and objectives of the study, this research investigated stress changes around the pit slopes with progression of mining and also the influence of geological and geotechnical conditions on mine planning. This was done so as to determine the zone of geotechnical influence from which planning of the underground mine would be done. Elastic 3D numerical modelling approach was used to determine the expected underground back break and its influence on the underground structure, pit slopes as well as the primary access. Different Factor of Safety shells were modelled, so that the corresponding zone of influence for each Factor of Safety could be correlated to the mine design. The results suggested that a Factor of Safety of two was ideal for this research for underground infrastructure to be outside the zone of geotechnical influence from start to finish of mining the first slice until the last fourth slice of the sublevel caving. This approach yield better projections of rock mass and slope behaviour since it considers a broad range of parameters that include rock mass strength properties, geology, geo-mechanical parameters, groundwater and rock behaviour.
NG (2020)

Long term planning is the process used by a mining organization to develop a strategic business plan. The plan describes how the ore is going to be extracted over the mine life. As such, it is routinely updated in order to declare annual reserves, evaluate options and react to changes in the initial assumptions. Inputs into this planning process are the parameters that drive profitability. The purpose of this research is to understand and document the open pit long range planning process in current use by mining operations, isolate the input parameters that feed into this process, and conduct a critical review of these parameters in an effort to develop a more robust plan. The thesis also searches for answers to the following questions: Can the copper metal price be correlated to a factor (or a set of factors)? Can the price be predicted? How useful is the work of O’Hara and Taylor in predicting the mine life and milling rate at the scoping study stage? How can the pit by pit graph be used to better guide the selection of the ultimate pit? Is there a realized benefit from operating at an elevated cutoff grade strategy with low grade copper porphyry deposits? The research concludes with a proposal (not common in the industry) for the selection of the metal price as an input into the mine planning process. This approach, if implemented, can give a corporation a dominant position in the future. The research also presents a modified approach for the selection of the ultimate pit. Furthermore, the use of Taylor’s rule in predicting the mine life was tested and verified on an open pit copper porphyry deposit and the benefits of operating at an elevated cutoff grade strategy was demonstrated for the deposit.
Thesis (Master, Mining Engineering) -- Queen's University, 2013-04-30 12:57:12.084

An advanced coursework and a project submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements of MSc. Engineering (Mining), November 2015
General For mining operations, both underground and open cast, there are generally accepted criteria used to arrive at the optimum mining method with which to exploit the ore body economically. Having selected the optimum mining method, mining companies should then make the decision to also select the optimum technology to apply given the various options that are now available. In the case of a shallow massive ore body where open-pit mining has been selected as the optimum mining method, the use of conventional trucks and shovels has been the popular choice but over the years, as pit become deeper, and stripping ratios increase, growing interest and adoption of in-pit crushing and conveying for both ore and waste has been gaining ground with several mining sites currently now operating, testing the systems or conducting studies at various stages for In-pit Crushing and Conveying (IPCC) in its different configurations (Chadwick, 2010). Open pit mining general involves the movement of pre-blasted or loose waste ahead of underlying ore out of the pit or to a previously mined part of the pit. This is then followed by the drilling and blasting or loosening of the ore and transportation to the processing plant or stockpiles. The conventional Truck and Shovel open pit operation involves the use of shovels – electric rope shovels, diesel or electric hydraulic shovels or excavators or front-end loaders to load the blasted, or loose waste and ore material in the pit onto mining trucks which haul the material to crushers or stockpiles if it is ore or to waste dumps in the case of waste. In a Fully Mobile IPCC (FMIPCC) system, the broken or loose material in the pit is loaded into a crusher or sizer by a shovel, continuous miner or dozer, crushed to a manageable size and transported by conveyor belts to the waste dump where it is deposited in place using spreaders if it is waste or onto stockpiles if it is ore. A combination of the two systems is where trucks dump material loaded at the face into a semi mobile crusher or sizer located in the pit close to the loading points N BANDA 392438 before conveying to destination thereby reducing truck haulage distance. In the semi-mobile configuration, the crusher is relocated closer to the loading points to minimise the hauling distance. Other various configurations are also employed depending on the various considerations. Although the Truck and Shovel system is considered as the convention in open pit mining, the IPCC system is not a new concept and has been operational on a number of mines worldwide for quite a number of years (Szalanski, 2010). Loading and hauling receive great attention especially in a high volume open pit mines due to the high cost contribution to the overall operation and therefore, if optimised, good cost savings can be realised (Lamb, 2010). Figure 1: Sishen Mining Cost Breakdown In the case of Sishen Loading and Hauling costs constituted 67% of the mining costs including labour mining support services in 2013 (Kumba Iron Ore, 2013). This picture remains unchanged to a large extent. In some cases the hauling cost alone can make up as much as 60% of the mining operating cost (Meredith May, 2012) Selection of a materials handling system between Truck and Shovel (T/S) and In-pit Crushing and Conveying (IPCC) has proven to be difficult due to limited understanding of the IPCC system especially its advantages and disadvantages relative to the Truck and Shovel system. The aim of this research was to unpack these two systems in terms of their applicability using studies conducted at Sishen 6,5% 8,8% 29,1% 22,7% 9,7% 0,6% 1,3% 0,4% 7,0% 4,2% 3,7% 5,9% Sishen Mining Cost 2013 Blasting Drilling Hauling L&H Contractors Loading Maintenance Other Mining Manangement Mining Engineering Mining Other Resource Management SHEQ Mining Support N BANDA 392438 Mine as well as develop some scorecard that could be used to select one over the other one. Sishen Case Study Sishen Mine is an iron ore open pit mine located in the Northern Cape province of South Africa and is part of Kumba Iron Ore Company which is Anglo American PLC. The mine has been in operation since 1953 with the current life of mine going up to 2030. It produces 44Mt tonnes of product from a 56Mt mine ore at a life of mine strip ratio of 4. One of the planned expansion the north part of the mine known as the GR80 and GR50 areas. Mining in these areas will require pre-stripping of 290Mt of clay material over the life of mine to expose the ore in pre volume phases. Figure2: Sishen Pit –Sishen Mine 2014. Sishen mine is constantly evaluating various technologies in its mining operations aimed at improving its bottom line by way of increasing productivity and efficiency, reducing costs and improving safety, however, the last time that the mine considered evaluating a technology that significantly could have resulted in a totally different operational philosophy was i contracted to institute a study to evaluate technology options for mining and moving majority owned by a minimum of 437Mt of calcrete and the underlying pre- g in 2007 when Snowden Mining Consultants run-ofmine areas is in -planned time and were N BANDA 392438 55 Mt of the calcrete/clay material per year from the waste pushback area in the GR80/GR50 area of the mine from 2009 till 2030. Snowden completed the Prefeasibility study in early 2008 in which they evaluated a conventional Truck and Shovel operation as well as IPCC. Economic viability of both systems in various configurations was demonstrated with the use of larger trucks and shovels ranked as the most economic option in terms of Net Present Cost (NPC), unit owning and operating cost per mined tonne and, to a less extent, in terms of risk and other considerations. In this case, the Truck and Shovel option was more economic than both IPCC configurations. However the small difference in the cost figures gave rise to interest in further evaluations. Following the Snowden study, Sishen engaged Sandvik Mining and Construction in 2008, to review the work done by Snowden and provide more detail and practical input to the IPCC system at scoping level. In the review, the IPCC system was shown to be the economic approach for the waste removal from the target area in terms of owning and operating cost. Practicality was also demonstrated and the case for the consideration of the IPCC system was put forward to Sishen. A further consultant, Sinclair Knight Merz (SKM) of Australia, was engaged, in the later part of 2008, to further evaluate and optimise the IPCC option to further demonstrate practically in detail at a feasible study level and strengthen its case by mitigating perceived risk. This included equipment specifications, mine and equipment layout per period per bench and risk assessment on the IPCC options. The mine, however, implemented the conventional truck and shovel option using larger equipment. The final decision was to stick with the current set up of Truck and Shovel system and gradually replace the current fleet of 730E Komatsu (190 tonne payload) trucks with the 930E or equivalent ( 320 tonne payload) and the current XPB 2300 P& H electric rope shovels and CAT 994/Komatsu WA1200 front end loaders with XPC 4100 P&H electric rope shovels, Komatsu PC8000/Liebherr 996 diesel hydraulic shovels and LeTournea L-2350 front end loaders to reduce the number of equipment and manage the operational cost. This decision was based on issues around initial capital investment, flexibility of the system to suit changing mining plans, ability of current personnel to run the system and general low risk appetite for change. The adopted option has its own challenges N BANDA 392438 such as supporting infrastructure requirements, labour intensity and associated low productivity and high cost, fleet management challenges to achieve required productivity constantly, supplies such as fuel and tyres and safety issues due to traffic density. A high level recalculation of the costs using current information was done as part of this research. For simplicity, no escalations or discounting were applied on future expenditure. The estimated unit owning and operating costs in 2014 terms for the study area were as follows:- Fully Mobile IPCC (FMIPCC) option ZAR 10.38/t, Semi Mobile IPCC (SMIPCC) option ZAR 13.12/t, Truck and Shovel option ZAR 15.80/t. The objective of this research is to use lessons from the Sishen case as well as other operations and gather expert views with the aim of establishing criteria that could be applied in a preliminary evaluation that would determine the suitability of either of the materials handling options. General Approach The costs were recalculated using as much current information as possible. Other considerations including advantages and disadvantages of either of the systems were examined in more detail, with real life examples examined where possible. This resulted in the establishment of generalized criteria for the selection of mining and transport technology for a large open pit mine with focus on conventional Truck and Shovel systems on one hand and IPCC systems, in their various formats, on the other. These criteria which identify conditions necessary for the successful adoption and implementation of either of the systems could then be used as input into the decision to carry out any further detailed studies of the options. The previous study reports on the Sishen mine case were examined, input parameters to the calculations checked and the general approached analyzed for practicality. The relative costs were also viewed for comparative purposes. Literature on these two main systems was reviewed including that from conferences. Other large operations running either one or both systems were looked at to gain N BANDA 392438 further insight. Original Equipment suppliers’ views on these systems were also looked at through many articles in the public domain. Sishen mine has previously had the IPCC system running in the same part of the mine in a semi mobile configuration, crushing and conveying waste. It was then changed to become a supplementary system for the ore handling system and the in pit crusher has never been relocated. The Truck and Shovel system took over the movement of all the waste and most of the ore at the mine. Lessons from these experiences were incorporated in this study.