DEMIN - Departamento de Engenharia de Minas

URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/510

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2018 - 201952020 - 20223

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Autor: search.filters.author.Torres, Vidal Félix NavarroTem arquivos: Sim

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Agora exibindo 1 - 8 de 8
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    Application of the HF, DRA and DCDA technologies for in situ stress determination in Iron Quadrangle rock masses.
    (2021) Penido, Henrique de Andrade; Funato, Akio; Metsugi, Hideya; Torres, Vidal Félix Navarro; Girao Sotomayor, Juan Manuel; Dight, Phil; Figueiredo, Rodrigo Peluci de; Assis, André Pacheco de; Guimarães, Alessandro Jésus
    This study presents an unprecedented campaign of measurements (magnitudes and orientations) of the in situ stresses in itabirite rocks of the Brazilian Iron Quadrangle region using the hydraulic fracturing (HF), deformation rate analysis (DRA) and diametrical core deformation analysis (DCDA) methods. The previous studies of this rock mass consider estimated values of k, and the practice of using in situ stress tests to support geotechnical analyses of the rock mass of this region has not been adopted. The study site is located at a depth of up to 400 m around a pit. The rock mass under study shows the presence of different geological structures, which made performing the tests difficult. The DRA results show a marked difference compared to the HF and DCDA results; the horizontal stresses were greater than the vertical stresses, which is a finding that may occur due to local geodynamic influences. The results contribute to the understanding of the strains and stresses induced by mining activities in the Brazilian Iron Quadrangle. For a better determination of the regional in situ stresses in the rock mass of the Brazilian Iron Quadrangle, new HF tests, as well as hydraulic testing of pre-existing fractures are recommended.
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    Hydrofracturing in situ stress measurements of itabirite in the Brazilian Ferriferous Quadrangle and their limitations.
    (2022) Penido, Henrique de Andrade; Figueiredo, Rodrigo Peluci de; Assis, André Pacheco de; Torres, Vidal Félix Navarro; Girao Sotomayor, Juan Manuel; Guimarães, Alessandro Jésus
    This article presents a first attempt to carry out in situ stress measurements (magnitudes and orientations) of the itabirite in the Brazilian Ferrifer- ous Quadrangle by hydraulic fracture testing at a depth of 399 m. Previous studies on this rock have consid- ered estimated values of the k index (ratio between the horizontal effective stress Sh, generally controlled by tectonism, and the vertical effective stress Sv, gener- ally controlled by gravity), and it is not a common practice to carry out in situ stress tests in this region and rock type to support geotechnical analysis. The area of study was located at a depth of 500 m in a pit because the determination of the in situ stress distri- bution is very important to assess the stability of the open-pit mine. The planning, execution and results of the tests are presented. The studied rock mass exhibits different geological structures, such as banding and foliation, which resulted in difficulties with perform- ing the tests, and only 12.5% of the tests were successful. The results can help interpret the strains and stresses induced by mining activities in slopes in the Brazilian Ferriferous Quadrangle and their impacts on the surrounding structures. For a better determina- tion of the regional in situ stresses in the rock of the Brazilian Ferriferous Quadrangle, hydraulic tests on pre-existing fractures are recommended.
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    Mine fleet cost evaluation : Dijkstra’s optimized path.
    (2019) Souza, Felipe Ribeiro; Câmara, Taís Renata; Torres, Vidal Félix Navarro; Nader, Beck; Galery, Roberto
    The transport distance in a mining operation strongly influences a mine op- eration revenue and its operational cycle because it is a fundamental part of the total mining costs. Generally, the transport route is determined based on an engi- neer’s practical knowledge, which does not consider any mechanism to optimize the possible routes to be taken. In an attempt to establish a methodology for cal- culating the path that results in minimum costs to transport the mined block to its destination, the Dijkstra methodology is applied to a tree graph analysis, where the mining blocks are analysed as nodes of the tree. The transport cost is reflected as the arc of the graphs, which can use the Euclidean distance or the transport time for the calculation of the minimum path. The result obtained from the Di- jkstra algorithm provided a non-operational route; to overcome this problem, an adjustment was performed through non-parametric equations. In this manner, it was possible to determine the transport costs for each block of the model. The paths based on Euclidean distance and transport time showed a tendency to in- crease for deeper mining regions. Identifying areas of largest growth and correctly quantifying their values increase the efficiency of mining planning.
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    Optimum mine production rate based on price uncertainty.
    (2019) Souza, Felipe Ribeiro; Câmara, Taís Renata; Torres, Vidal Félix Navarro; Nader, Beck; Galery, Roberto
    The production rate of a mining operation has an important effect on the opera- tional cycle and gross profit, which are often evaluated based on engineering practices. Assessment of the economic performance of mine operations in mining engineering is of great importance because an incorrect production rate can result in significant financial losses. The production rate is composed of two bases: the cost estimation and the price scenario. Bureau of Mines studies performed on American mines indicated that processing costs can be estimated through the production rate. This article pro- poses to connect the model presented by the Bureau of Mines and queuing theory to describe the operational costs, which are used to develop a production optimization methodology. The proposed cost composition describes a production system to verify the law of diminishing returns and the economy of scale. Between these regions of the production curve, the optimum point was determined with mathematical precision.
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    Analysis of the impacts of slope angle variation on slope stability and NPV via two different final pit definition techniques.
    (2020) Chaves, Leonardo Soares; Carvalho, Luiz Alberto de; Souza, Felipe Ribeiro; Nader, Alizeibek Saleimen; Arroyo Ortiz, Carlos Enrique; Torres, Vidal Félix Navarro; Câmara, Taís Renata; Napa Garcia, Gian Franco; Valadão, George Eduardo Sales
    The traditionally and widely used Lerchs-Grossmann algorithm presents well-known limitations that newer propositions attempt to overcome. The direct block schedule (DBS) methodology, which has gained relevance with computational advances, obtains the final pit as a natural result of production sequencing, different from Lerchs-Grossmann-based algorithms. This process flow applies constraints in the final pit definition stage attempting to provide a more realistic result and to minimize risks. Slope instability is a common and inherent risk to open pit mining and may affect the project's net present value (NPV). A study of the impacts of slope angle variations on safety indexes and final pit NPV provides an auxiliary tool for the overall slope angle definition process. This article presents a case study in which the effects of variations of the overall slope angle on the safety factor (SF) and project NPV were analyzed. A total of 25 pits were generated by each studied final pit definition methodology, and each pit had the sections with the varied slope angles analyzed in the stability assessment, resulting in a total of 150 slopes analyzed. A comparison between the results obtained by the two different methodologies implemented in commercial software is presented. The results show no relationship between the NPV and the overall slope angle using the DBS methodology. An analysis of the results for each geotechnical sector obtained by the traditional methodology was conducted and may contribute to the trade-off analysis between the best slope angle to achieve a reasonable SF and the maximum NPV.
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    Assessing and controlling of bench blasting-induced vibrations to minimize impacts to a neighboring community.
    (2018) Torres, Vidal Félix Navarro; Silveira, Leandro Geraldo Canaan; Lopes, Paulo Filipe Trindade; Lima, Hernani Mota de
    Blasting is an important operation in mining production but is a source of concern due to its associated environmental impact; in particular, blasting-induced vibrations may cause structural damage and human discomfort. For decades, communities near open-pit mines have complained of blasting-induced vibrations. This study presents a methodology to predict, assess, and control ground vibrations in large open-pit mines operating close to a community. To conduct this study, 178 levels of blastinginduced vibrations were recorded in an area encompassing a large open-pit iron ore mine and a neighboring community located in the Quadril atero Ferrífero, state of Minas Gerais, Brazil. Collected data were processed with multiple regression techniques to obtain the blasting vibration attenuation law to predict the levels of blasting-induced vibrations for the locality studied with knowledge of only the maximum explosive charge per delay and the distance to the blasting point. Brazilian and international admissibility standards of blasting-induced vibration, the minimum distance between the mine and community and the constants obtained from the regression were used to establish the maximum explosive charge per delay for an acceptable ground vibration level that would not cause structural damage and human discomfort. Finally, the proposed methodology was validated by comparing the predicted ground vibrations levels to measured values. The results demonstrate that this methodology can be applied to any open-pit mine to control blasting-induced vibration effects.
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    Classical and stochastic mine planning techniques, state of the art and trends.
    (2018) Torres, Vidal Félix Navarro; Nader, Beck; Arroyo Ortiz, Carlos Enrique; Souza, Felipe Ribeiro; Burgarelli, Hudson Rodrigues; Chaves, Leonardo Soares; Carvalho, Luiz Alberto de; Câmara, Taís Renata; Fernandes, Eunírio Zanetti; Galery, Roberto
    Determination of the best possible ultimate pit for an open pit mine is a fundamental subject that has undergone a highly evolutionary process, reviewed in this study, since the correct choice carries substantial economic impact for the industry. The correct choice can be very beneficial for project analysis, whereas an incorrect choice has the potential to mask huge financial and economic future losses that could render a project unfeasible. The advent of computers in the 1960s allowed sophisticated analysis for the selection of the best ultimate pit determination, under specific modifying factors such as economic, social, environmental, and political, but only in deterministic situations, i.e., when the problem and variables for the ultimate pit determinations were considered deterministically and almost always based on average values. Techniques such as the Lerchs– Grossman algorithm and mixed-integer programming are among many standard tools now used by the mineral industry. Geological uncertainty and the associated risks as well as the need to consider the appropriate time to mine a block during a mine operation have a significant impact on the net present value of the resulting ultimate pits. Stochastic aspects embed a probabilistic component that varies in time and are now under intense investigation by researchers, who are creating algorithms that can be experimented with and tested in real mine situations. One can expect that once these algorithms demonstrate their efficiency and superior results, they will readily dominate the industry.
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    Direct block scheduling under marketing uncertainties.
    (2018) Burgarelli, Hudson Rodrigues; Souza, Felipe Ribeiro; Nader, Alizeibek Saleimen; Torres, Vidal Félix Navarro; Câmara, Taís Renata; Arroyo Ortiz, Carlos Enrique; Galery, Roberto
    Mineral projects are composed of geological, operational and market uncertainties, and reducing these uncertainties is one of the objectives of engineering. Most surveys assess the impact of geological and operational uncertainties on the mining planning. The objective of this work is to study the impact of market uncertainty on the mineral activity. The influence of iron ore price simulation on mining sequencing will be evaluated. The price of iron ore has random behavior that is best represented by the Geometric Brownian Movement system. This study analyzed the historical series of iron ore in order to determine the percentage volatility and drift. Traditionally, a constant and deterministic price is used for the ore mined in all periods of a mineral project. The direct block scheduling methodology was adopted because it is able to apply the appropriate financial discount factor to the simulated probabilistic price. The proposed methodology was able to quantify the market uncertainty.