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.

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

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.

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.

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.

Faculty of Engineering and Built Enviroment School of Mining Engineering 0315711f musakale@egoli.min.wits.ac.za / Rockfalls are a significant risk in open pit mines. Once movement of a rock perched on the top of a slope (bench) has been initiated, the most important factor controlling its fall trajectory is the geometry of the slope (bench). The best possible knowledge of rockfall trajectories and energies is important in order to determine accurate risk zoning and for the design and construction of adequate defence systems near the threatened areas. This study attempts to determine the influence of bench geometries, and the coefficient of restitution of rock, on rockfall behaviour. A study of literature was carried out to review previous studies and other relevant information on rockfalls and their analysis. The literature may be divided into two categories: experimental methods involving physical modelling, and computer models involving rockfall analyses using computers analysis methods. Rockfall computer simulation is considered to be applicable, quick to carry out and reproducible. The accuracy of the results depends on the knowledge of site conditions and slope geometry. The use of the Modified Ritchie criterion for the design of catch benches in open pit mines was also investigated. The assessment of bounce height, maximum run-out distance and kinetic energy achieved during the fall of rocks on the catch bench were the bases of the evaluation of the results obtained in this project. The computer program, Rocfall Version 4, was used for the purposes of the research. The following parameter variables were considered in the analyses: three types of rock; slopes with three stack configurations; four bench heights; and four bench face angles. The results show that, for all stack configurations and rock types, the maximum runout distance and maximum bounce height increase as functions of bench height at a specific bench face angle. A single bench configuration provides a maximum run-out distance of falling rocks larger than the value determined using the Modified Ritchie criterion for all rock types and bench face angles. Multiple bench stack configurations provide maximum run-out distances less than the value determined using the Modified Ritchie criterion only for the 90o bench face angle in all rock types; those with 60o, 70o and 80o bench face angle provide a larger maximum run-out distance. Therefore, the validity of the Modified Ritchie criterion for the design of catch bench widths in open pit mines with inclined benches must be questioned. According to Ritchie’s study (1963), rocks that fall in trajectory (free fall) seldom give high bounces after impact on a catch bench. This project shows that this finding is valid for rocks with low coefficients of normal restitution. Rocks with lower coefficients of normal restitution provide larger run-out distances with flatter bench face angles compared with rocks with higher coefficients. In contrast, rocks with higher coefficients provide larger run-out distances than those with lower coefficients for steeper angles. The consideration of the influence of geometry (shape) of falling rocks on rockfall behaviour showed that, for a flatter slope, as could logically be expected, the maximum run-out distance is greatest for rounder rocks and smallest for flatter slabby iv rocks. This is due to the fact that on a flatter slope, the mode of falling of rounder rocks is rolling down the slope. This mode provides essentially no resistance to motion, resulting in largest maximum run-out distance. In contrast, for long flat slabs, the mode of movement will be sliding, which results in a smaller maximum run-out distance. The maximum run-out distance as function of rock shape reduces as the normal coefficient of restitution increases. For all rock types, the maximum bounce height reduces as a function of the friction angle for flatter slopes. This is due to the fact that rocks are in contact with the slope during the rockfall. As the coefficient of normal restitution increases, an increase in the maximum bounce height results.

Esta dissertação apresenta uma revisão bibliográfica dos principais aspectos envolvidos nas operações de escavação de rochas com furos de grande diâmetro na mineração a céu aberto. O trabalho expõe o método de perfuração rotativa por ser o mais utilizado na execução desta operação unitária de lavra. Faz-se também um estudo dos principais agentes de desmonte que contribuem no emprego de furos de grande diâmetro na indústria da mineração, especialmente na explotação de minérios metálicos. São analisadas as propriedades do maciço rochoso, na determinação da carga específica e sua influência nos resultados da escavação de rochas por explosivos. É realizada ainda uma análise da metodologia utilizada para o dimensionamento do plano de fogo, baseando-se na inter-relação existente entre seus diversos elementos geométricos. Apresenta-se também a teoria de crateras como uma metodologia alternativa para dimensionamento de plano de fogo. Finalmente mostram-se os principais impactos ambientais decorrentes da detonação de explosivos na escavação de rochas. / This dissertation presents a bibliographical review of the main aspects involved in the open pit blasting operation using large diameter blastholes. The work displays the method of rotary drilling, being the most frequent used in the execution of this mining unitary operation. Here is presented a study of the main blasting agents that contribute to the increasing application of large diameter blastholes in the mining industry, especially in the field of metallic ores. The properties of the rock mass are analysed, in the determination of the powder factor and its influence on the results of rock excavation by explosives. An analysis of the methodology used for the determination a shot plan is carried out based on the existing interrelation between diverse geometric elements involved. The crater theory is also presented as an alternative methodology for the same purpose. Finally, the main environmental impacts caused by blasting in the rock excavation are discussed.

Este trabalho propõe uma metodologia inovadora de seqüenciamento de lavra em minério de ferro a qual, além de considerar os parâmetros operacionais e econômicos das técnicas tradicionais, permite uma abordagem ambiental proativa para sequenciar a lavra de forma a antecipar a exaustão de parte da cava para disposição do estéril dentro da cava final. A metodologia proposta de seqüenciamento ordenado de lavra permite reduzir a área degradada a ser reabilitada na mina, com significativos benefícios associados à reducão do impacto ambiental, sem comprometer as metas de produtividade e competitividade econômica da lavra. A metodologia de seqüenciamento ordenado de lavra foi aplicada em um estudo de caso de projeto de lavra de minério de ferro, e os resultados alcançados comprovaram os benefícios esperados com a aplicação da metodologia proposta. / This paper presents a innovative approach for an environmentally pro-active mine scheduling process. The proposed methodology has been developed for identifying a mine sequence that meets all operational and economical constraints in iron-ore mining, and takes into account a pro-active approach for scheduling the mine according to environmental criteria. The proposed methodology allows a significant reduction of the environmental impact related to the mining operation without compromising productivity and the economical feasibility of the mine. The methodology has been applied to a case study of iron ore mining in Brazil, where the expected benefits have been proven.

Methods for estimating productivity and costs, and dependent equipment selection process, have needed to be increasingly reliable. Estimated productivity and costs must be as accurate as possible in reflecting actual productivity and costs experienced by mining operations to accommodate the long-term trend for diminishing commodity prices, For loading and hauling equipment operating in open pit mines, some of the interrelated estimating criteria have been investigated for better understanding; and, consequently, more reliable estimates of production and costs, also more effective equipment selection process. Analysis recognizes many of the interrelated criteria as random variables that can most effectively be reviewed, analyzed and compared in terms of statistical mathematical parameters. Emphasized throughout is the need for management of the cyclical loading and hauling system using conventional shovels/excavators/loaders and mining trucks to sustain an acceptable “rhythm” for best practice productivity and most-competitive unit-production costs. Outcomes of the research include an understanding that variability of attributes needs to be contained within acceptable limits. Attributes investigated include truck payloads, bucket loads, loader cycle time, truck loading time and truck cycle time. Selection of “ultra-class” mining trucks (≥ 290 -tonne payload) and suitable loading equipment is for specialist mining applications only. Where local operating environment and cost factors favourably supplement diminishing cost-benefits of truck scale, ultra-class trucks may be justified. Bigger is not always better – only where bigger can be shown to be better by reasons in addition to the modest cost benefits of ultra-class equipment. Truck over-loading may, to a moderate degree, increase productivity, but only at increased unit cost. / From a unit-cost perspective it is better to under-load than overload mining trucks. Where unit production cost is more important than absolute productivity, under-trucking is favoured compared with over-trucking loading equipment. Bunching of mining trucks manifests as a queuing effect – a loss of effective truck hours. To offset the queuing effect, required productivity needs to be adjusted to anticipate “bunching inefficiency”. The “basic number of trucks” delivered by deterministic estimating must provide for bunching inefficiency before application of simulation applications or stochastic analysis is used to determine the necessary number of trucks in the fleet. In difficult digging conditions it is more important to retain truck operating rhythm than to focus on achieving target payload by indiscriminately adding loader passes. Where trucks are waiting to load, operational tempo should be restored by sacrificing one or more passes. Trucks should preferably be loaded by not more than the nominal (modal) number plus one pass. The research has: • Identified and investigated attributes that affect the dispersion of truck payloads, bucket loads, bucket-cycle time, loading time and truck-cycle time. • The outcomes of the research indicate a need to correlate drilling and blasting quality control and truck payload dispersion. Further research can be expected to determine the interrelationship between accuracy of drilling and blasting attributes including accuracy of hole location and direction. • Preliminary investigations indicate a relationship between drill-and-blast attributes through blasting quality control to bucket design, dimensions and shape; also discharge characteristics that affect bucket cycle time that needs further research.

Esta dissertação apresenta uma revisão bibliográfica dos principais aspectos envolvidos nas operações de escavação de rochas com furos de grande diâmetro na mineração a céu aberto. O trabalho expõe o método de perfuração rotativa por ser o mais utilizado na execução desta operação unitária de lavra. Faz-se também um estudo dos principais agentes de desmonte que contribuem no emprego de furos de grande diâmetro na indústria da mineração, especialmente na explotação de minérios metálicos. São analisadas as propriedades do maciço rochoso, na determinação da carga específica e sua influência nos resultados da escavação de rochas por explosivos. É realizada ainda uma análise da metodologia utilizada para o dimensionamento do plano de fogo, baseando-se na inter-relação existente entre seus diversos elementos geométricos. Apresenta-se também a teoria de crateras como uma metodologia alternativa para dimensionamento de plano de fogo. Finalmente mostram-se os principais impactos ambientais decorrentes da detonação de explosivos na escavação de rochas. / This dissertation presents a bibliographical review of the main aspects involved in the open pit blasting operation using large diameter blastholes. The work displays the method of rotary drilling, being the most frequent used in the execution of this mining unitary operation. Here is presented a study of the main blasting agents that contribute to the increasing application of large diameter blastholes in the mining industry, especially in the field of metallic ores. The properties of the rock mass are analysed, in the determination of the powder factor and its influence on the results of rock excavation by explosives. An analysis of the methodology used for the determination a shot plan is carried out based on the existing interrelation between diverse geometric elements involved. The crater theory is also presented as an alternative methodology for the same purpose. Finally, the main environmental impacts caused by blasting in the rock excavation are discussed.