2019 - AÇIK İŞLETME YÖNTEMİ İLE ÜRETİM YAPACAK OLAN BİR MADEN İŞLETMESİNİN OPTİMUM ÜRETİM PLANLAMASI

Access here · Turkish · ¹ K. Hasözdemir 1, ¹ S.G. Erçelebi

¹ İstanbul Teknik Üniversitesi, Maden Mühendisliği Bölümü

Summary

Günümüzde yüksek tenörlü cevher yataklarının tükenmesi ile birlikte madencilik işlerinin ekonomik açıdan güvenli bir şekilde yürütülebilmesi stratejik bir planlama evresi gerektirmektedir. Bu anlamda açık ocak üretim planlaması, üretilmesi sonucu kar edileceği düşünülen cevher bloklarının maksimum net bugünkü değeri elde edeceğimiz şekilde hangi sırayla üretilmesi gerektiğini bulmaktır. Bu çözüme ulaşmak pek çok kısıtı ve karar değişkeni olan bir optimizasyon probleminin çözülmesini gerektirir. Bu kapsamda, yapılan arama çalışmaları ve laboratuvar analizleri sonucu elde edilen sondaj verilerinin bilgisayar ortamına taşınması ile 3 boyutlu olarak modellenmiş bir cevher yatağı kullanılmıştır. Boyutları x:10m, y:10m, z:10m olan cevher bloklarına 3 boyutlu semi-variogram analizlerine dayalı olarak bir ara değer atama metodu olan krigging metodu ile tenör ataması yapılmıştır. Tenörlerine göre ekonomik değeri belirlenmiş olan bloklar, karışık tam sayı programlama ve sezgisel yöntemler ile yazılmış bir algoritma ile çalışan SimSched isimli bir yazılım yardımı ile önce nihai açık ocak sınırlarının optimizasyonu için kullanılmıştır. Daha sonra bu sınırlar içerisindeki blokların hangi sırayla üretilecekleri, mevcut üretim ve tesis kapasitesine göre, şevlerin fiziksel kısıtlamalarına göre, düşey ilerleme hızı ve madencilik faaliyetlerinin yürütüleceği minimum genişliğe göre, üretilecek cevherin cut-off tenörüne göre ve atığa gönderilecek malzemenin maksimum tenörüne göre istenilen sınırlar içerisinde kalacak şekilde simüle edilerek optimum üretim planı yapılmıştır.

Keywords: Açık ocak madenciliği, Uzun-vadeli üretim planlaması, Blok model, Üretim planı optimizasyonu, Blok Üretim Planlaması

2019 - Environmental optimisation of mine scheduling through life cycle assessment integration

Access here · English · ¹ ³ Robert Pell, ¹ Laurens Tijselling, ¹ Luke W. Palmer, ¹ Hylke J. Glass, ² Xiaoyu Yan, ¹ ² Frances Wall, ³ Xianlai Zeng, ³ Jinhui Li

¹ Camborne School of Mines, University of Exeter Penryn Campus, Penryn, Cornwall, TR10 9FE, United Kingdom

² Environment and Sustainability Institute, University of Exeter Penryn Campus, Penryn, Cornwall, TR10 9FE, United Kingdom

³ Key Laboratory for Solid Waste Management and Environment Safety, School of Environment, Tsinghua University, Beijing, 100084, China

Summary

Life cycle assessments (LCA) are useful to quantify the environmental costs of mining projects, however the application of LCA is often a retrospective environmental measurement of operating mines. This paper presents a novel methodology of carrying out a LCA to generate life cycle impact assessment data that can form an environmental block model of a deposit. These spatially explicit data can then be used as a constraint within long-term mine scheduling simulations. The results indicate that significant reductions in global warming impact can be achieved at a small economic cost. For example using an environmental constraint it was possible to achieve 91.9% of the global warming impact whilst achieving 95.9% of the net present value compared to the baseline. Different constraints and economic scenarios are explored and multi-criteria decision analysis is carried out. This approach enables environmental considerations to be included in strategic mine planning. This is important because mining will continue to form an important part of our society for the foreseeable future. Integrating environmental considerations into the earliest stages of mine planning can assist in driving environmentally responsible raw material extraction.

2018 - Implementación del Software SimSched DBS para un yacimiento polimetálico modificando variables geométricas

Access here · Spanish · ¹ David Oliveiros-Sepúlveda, ² Eliana Hijuelos-Franco, ¹ Jenis Margoth Trespalacio-Torres, ² Giovanni Franco-Sepúlveda

¹ Grupo de Planeamento Minero , Giplamin , Faculdad de Minas, Universidad Nacional de Colombia

² Grupo de Planeamento Minero , Giplamin , Departamento de Materiales y Minerales, Faculdad de Minas, Universidad Nacional de Colombia

Summary

Con el siguiente artículo se pretende estudiar el tajo final de un yacimiento hipotético polimetálico utilizando el software SimSched DBS, basado en un conjunto de etapas consecutivas como tajo final con tajos anidados, diseño de fases, secuencia operacional período a período, entre otros; esto mediante la modificación y análisis de variables geométricas como son el ángulo del talud, el avance vertical y el fondo del tajo. Además, se estudia la estrecha relación entre la variación del Valor Presente Neto (VPN) y la modificación de las tres variables geométricas consideradas anteriormente.

2018 - Impact of the grade distribution on the final pit limit definition

Access here · English · ¹ Luiz Alberto Carvalho, ² Felipe Ribeiro Souza, ¹ Leonardo Soares Chaves, ¹ Beck Nader, ¹ Taís Renata Câmara, ² Vidal Félix Navarro Torres, ¹Roberto Galery

¹ Universidade Federal de Minas Gerais , ² Instituto Tecnológico Vale, ³ Universidade Federal Mato Grosso

Summary

Geologic modeling is an important step in determining the benefits and final pit dimensions for mining operations. Geostatistical models and distance-based functions are the main methods used to estimate the grade behavior. However, these two methods, despite their similar mean values, differ in spatial variability. The objective of this article is to prove, by comparing the two methodologies, that models with different spatial variability using the Lerchs-Grossmann algorithm will output subtly different final pit dimensions and scheduling. Furthermore, with the direct block schedule (DBS), these differences can be considerable. The tests compared the methodologies using the following three models: inverse distance (ID), ordinary kriging (OK) and turning bandssimulation (TBS). The results demonstrate that the Lerchs-Grossmann algorithm is only slightly sensitive to the spatial variability of the grade; however, DBS requires the model populations to be better defined because of its greater sensitivity to spatial variability.

2018 - Direct block scheduling technology: Analysis of Avidity

Access here · English · ¹ Felipe Ribeiro Souza, ¹ Hudson Rodrigues Burgarelli, ¹ Alizeibek Saleimen Nader, ¹ Carlos Enrique Arroyo Ortiz, ¹ Leonardo Soares Chaves, ¹ Luiz Alberto Carvalho, ² Vidal Félix Navarro Torres

¹ Universidade Federal de Minas Gerais , ² Instituto Tecnológico Vale

Summary

This study is focused on Direct Block Scheduling testing (Direct Multi-Period Scheduling methodology) which schedules mine production considering the correct discount factor of each mining block, resulting in the final pit. Each block is analyzed individually in order to define the best target period. This methodology presents an improvement of the classical methodology derived from Lerchs-Grossmann’s initial proposition improved by Whittle. This paper presents the differences between these methodologies, specially focused on the algorithms’ avidity. Avidity is classically de-fined by the voracious search algorithms, whereupon some of the most famous greedy algorithms are Branch and Bound, Brutal Force and Randomized. Strategies based on heuristics can accentuate the voracity of the optimizer system. The applied algorithm use simulated annealing combined with Tabu Search. The most avid algorithm can select the most profitable blocks in early periods, leading to higher present value in the first periods of mine operation. The application of discount factors to blocks on the Lerchs-Grossmann’s final pit has an accentuated effect with time, and this effect may make blocks scheduled for the end of the mine life unfeasible, representing a trend to a decrease in reported reserves.

2017 - NPV analysis as a function of the discount rate and cost of re-handling implementing SIMSCHED DBS to open pit mining

Access here · Spanish · Universidad Nacional de Colombia

Summary

La función de todo software es modelar situaciones que se asemejan a la realidad, con el fin de encontrar las condiciones más viables para desarrollar un proyecto minero, lo cual implica incrementar ingresos y reducir costos mediante la toma de decisiones. En esta industria los inversionistas buscan obtener los ingresos más altos a la hora de explotar los recursos del subsuelo, con el objetivo de lograr el retorno a la inversión. En el presente artículo se evalúa la tasa de descuento y el costo de remanejo de un depósito mineral hipotético de oro y cobre, utilizando el software SIMSCHED DBS. A su vez se hace una revisión bibliográfica la cual permite dar claridad a los conceptos utilizados. Con base a las simulaciones realizadas con las dos variables económicas se pretende seleccionar el valor presente neto (VPN) más óptimo para los flujos futuros.

2017 - SimSched Direct Block Scheduler: A new practical algorithm for the open pit mine production scheduling problem

Access here · English · Rodolfo Ota¹ ², Luis Martinez³, R&O Analytics

¹ MiningMath, Brazil, ² Universidade Federal de Minas Gerais, ³R&O Analytics, Austrália

Summary

Current practices in open pit mine planning normally challenges mine planners and mine managers to make different decisions at different stages before achieving the generation of the best long-term production scheduling for their projects. The objective of this thesis provides an in-depth coverage of a novel open pit mine optimization framework, called SimSched Direct Block Scheduler (SimSched DBS). This software allows for a more global optimization process in mine planning, where it includes the steps of the traditional practices in its own single optimization algorithm and provides the mine production scheduling straight from the block model.

2017 - A Comparision of DBS and Nested Pit Stage Design as a Basis for Strategic Planning

Access here · English · Martin L. Smith², Lucas M. Nogueira¹

¹ Department of Mining Engineering (DEMIN) , ² Minesmith Pty Ltd, Australia

Summary

Direct Block Scheduling ( DBS ) and standard nested pit optimization were used as two alternative starting points to define alternative mine planning scenarios. We contrast and compare the stage reserves produced by DBS and LG nested pits. Both sets of staged pit sequences are converted into detailed mine plans to produce a comprehensive comparision of the two approaches to pit optimization. Both methods produce similar reserves and value. Both reserves require intervention by an experienced engineer to produce a viable basis for staged reserves, but the imposition of additional geometric constraints in DBS yields a superior starting point. We conclude that DBS is a promising alternative to LGNP.

2017 - Mining sequence and mine capacity in open pit mining

Access here · English · Juan Camus , InnovaMine SpA, Chile

Summary

This paper challenges the current way the mine sequence and mine capacity are determined in practice in open pit mining. The former is usually determined by means of the Lerchs-Grossmann algorithm (LG) whereas the latter using a rule of thumb that involves mine equipment productivity and / or a preemptive bench sinking rate. The advent of more capable software and hardware has recently enabled the creation of more efficient mining applications to solve the mining sequence problem. But their theoretical results are risking to be labeled as unpractical if the mine capacity issue is not well understood.

2015 - A surface constrained stochastic mine production scheduling method and its application at a copper deposit

Access here · English · Alexandre Marinho de Almeida and Roussos Dimitrakopoulos

COSMO - Stochastic Mine Planning Laboratory, Dept. of Mining and Materials Engineering

McGill University, 3450 University St., Montreal, Quebec, H3A 2A7, Canada

Summary

This paper proposes a new stochastic integer programming (SIP) formulation based on surfaces, with a sequential implementation to address the optimization of life-of-mine production schedules for open pit mines with uncertain supplies of metal. The proposed formulation maximizes discounted cash flows and controls risk of deviation from production targets. The formulation using surfaces facilitates a sequential implementation, which was presented and compared using a small testing deposit. Results for the sequential approach were obtained more than 100 times faster and were identical to a single run of the SIP formulation. The application of the proposed approach to an existing deposit with 176,138 mining blocks and 25 mining periods demonstrates its computational efficiency.

Keywords: mine production scheduling, geological uncertainty, surface, stochastic optimization, risk analysis

2015 - A Comparison of Conventional and Direct Block Scheduling Methods for Open Pit Mine Production Scheduling

Access here · English · ¹ Nelson Morales, ¹ Enrique Jélvez, ¹ Pierre Nancel, ² Alexandre Marinho, ² Octávio Guimarães

¹ Dpt. of Mining Engineering & AMTC, University of Chile, Santiago

² MiningMath Associates, Belo Horizonte, Brazil

Summary

Open pit mine production scheduling for long-term planning is a relevant and required task for any mining project or operation. Mining blocks must be scheduled for extraction over a set of years, and a destination must be assigned to each one of them. The goal is to maximize the Net Present Value of the project, subject to capacity and operational constraints. Traditionally, this task hasbeen performed either with the guidance of nested pits produced by the Lerchs-Grossmann algorithm (LG), considering pre-defined block destinations, or by the use the Direct Block Scheduling (DBS), in which individual blocks are selected (or not) for extraction and destinations are assigned at given periods of time. On the one hand, from the purely theoretical side, DBS methods should be superior to those based on LG, because they are designed to deal with more realistic considerations of the problem (like capacities, multiple products, etc.) while LG approaches are limited to slope constraints and a unique economic value as parameters. On the other hand, the practical one, LG-based methods have been at the advantage, because DBS methods require intensive computational power to be solved. Fortunately, in later years, the availability of new algorithms and technology has made DBS more competitive. New DBS algorithms based on Integer Programming and heuristics have arisen with reasonable processing times, and MineLib, a set of standard datasets for testing, has been published and made available for researchers and software developers. This paper presents two DBS algorithms and show, by means of MineLib, their competitiveness against the state-of-the-art algorithms commercially available. Furthermore, these algorithms are applied to a case study in order to see how the solutions obtained differ and improve on the traditional approach based on LG.

2015 - Traditional versus stochastic mine planning under material type and grade uncertainties

Access here · English · ¹ Alexandre Marinho, ² Dr. Luis Martinez Tipe

¹ MiningMath Associates, Belo Horizonte, Brazil

² Managing Director of ROMPEV Pty Ltd Indooroopilly, Australia

Summary

Long-term open pit mining production scheduling has been traditionally addressed with the assumption of perfect knowledge of the orebody model, given by a single geologic model filled with estimated mining block values. Material type and grade uncertainties are usually ignored misleading analysts and mine planners to make final operational and investment decisions. This paper shows how the inclusion of both rock type and grade uncertainties provide additional information about the project indicators behaviour, which should be accounted for when making final decisions. To achieve this, this paper considers a copper deposit with oxide and sulphide zones. Each zone has a given slope angle and a given density. The possible processing destinations are: a mill, an oxide leach and a sulphur leach processing plant, with respective non-linear recovery curves depending on grade. If oxide material is sent to the sulphur leach plant, or vice-versa, the recoveries are penalized. This orebody model is represented by 20 scenarios, in which each scenario represents one possible combination of material types and grades over the deposit. A direct block scheduling software is used herein for a comparison between traditional and stochastic mine planning for this deposit, considering optimized decisions on what to mine, when to mine and where to send. The optimizer maximizes the expected discounted cash flow of the project subject to physical and production constraints. The traditional scheduling considers the predominant material type for each block and the average grade over all scenarios. The stochastic scheduling considers the uncertainty in material types and copper grades, returning a schedule robust to all scenarios simultaneously. Comparisons show the importance of taking uncertainties into account in the definition of a long-term schedule with lower risk.

Keywords: mine production scheduling, geological uncertainty, stochastic optimization, risk analysis

2015 - The impacts of slope angle approximations on open pit mining production scheduling

Access here · English · ¹ Filipe S. Beretta, ² Alexandre Marinho,

¹ Mining Engineer Consultant, SRK Consulting, Cardiff, UK

² MiningMath Associates, Belo Horizonte, Brazil

Summary

Open pit mining production scheduling requires slope angles to be defined as input to the engineering/optimization processing steps. The slope angles are approximated through appropriate parameters and methods, in an attempt to reproduce the safety requirements of an open pit mining operation. Different methods can result in considerably dissimilar results for the pit configuration. This paper presents the volatility of reported mineral reserves and cashflows to different slope angle approximation methods, when applied to open pit mining production scheduling. Two methods were revisited and parameters were changed to create a set of scenarios. The method based on blocks precedence, adopted in GEOVIA Whittle software, is examined, comparing the results for the variation of the ‘maximum number of levels’ parameter. The method based on mining surfaces, implemented in MiningMath SimSched software, is explored and compared with the previous results. The comparison between both methods shows the importance of the selection of the appropriate parameters and methods for each deposit. The ultimate pits produced by the blocks precedence method have shown a variation of up to 10.4% in reserves, with errors up to 7.8 degrees in slope angle approximations; against no variation and 0% error for the surface based method. For the mining schedule, using similar parameters for both methods, the discounted cashflow and production indicators differences are also analysed and reported herein.

2014 - The impacts of slope angle approximations on pit optimization

Access here · English · ¹ Filipe S. Beretta, ² Alexandre Marinho,

¹ Mining Engineer Consultant, SRK Consulting, Cardiff, UK

² MiningMath Associates, Belo Horizonte, Brazil

Summary

During the pit optimisation process, methods and parameters for slope angle approximations must be defined. This paper presents the sensitivity of the optimisation results to the method and parameters considered. The method based on blocks precedence, adopted in GEOVIA Whittle software, is examined, comparing the results for the variation of the ‘maximum number of levels’ parameter. The method based on mining surfaces, implemented in MiningMath SimSched software, is explored and compared with the previous results. The ultimate pits produced by the blocks precedence method have shown a variation of up to 10.4% in reserves and 2.8% in cashflow, with errors up to 7.8 degrees in slope angle approximations; against no variation and 0% error for the surface based method.

Keywords: pit optimization; Whittle; SimSched.

2013 - Sequenciamento Direto de Blocos

Access here · Portuguese · ¹ Octávio Guimarães, ¹ Alexandre Marinho,

¹ MiningMath Associates, Belo Horizonte, Brazil

Summary

Este artigo visa comparar resultados de três tecnologias utilizadas para sequenciamento de lavra aplicado a minas a céu aberto. No primeiro método, a sequência de lavra é otimizada diretamente a partir do modelo de blocos através de Programação Inteira Mista (MIP). No segundo método, o sequenciamento direto de blocos ocorre através de um método híbrido composto de MIP e heurísticas. Resultados são comparados com o amplamente aceito algoritmo de Lerchs-Grossman com cavas aninhadas. As vantagens e limitações de cada método são comparadas através de exemplos utilizando um depósito de cobre e ouro bem conhecido. O sequenciamento direto de blocos se mostra como alternativa de valor econômico superior, dispensando as etapas de otimização de cava, geração de cavas aninhadas e otimização de teor de corte.

Keywords: Sequenciamento direto de blocos; planejamento de lavra; otimização de cava; mina a céu aberto.

2011 - Value creation in the mining business

Access here · English · ¹ Juan Camus,

¹ Former Mining Industry Fellow at The University of Queensland, Australia and currently Managing Partner at InnovaMine, Chile

Summary

This paper challenges the deep-rooted notion that value creation in mining is all about production and costs. Instead, it puts forward that it mainly refers to the capacity of companies to continually increase the prospective mineral resources and transform them into economically mineable mineral reserves in the most effective and efficient way. To support this proposition, this study seeks to demonstrate that mining companies that excel in total shareholder return (TSR) over an entire economic cycle are those that also excel in expanding their reserves and production, here referred to as total reserves increment (TRI). The relationship between both variables is simple and revealing – company share price is to mineral reserves as dividends are to production. This match gives economic sense to the term ‘deposit’, which is used in mining parlance to refer to an ore body. Results obtained from a diverse group of 14 mining companies over the period 2000-2009 evince the previous hypothesis. There are two doubtful cases, but as the paper suggests these are transitional companies in the process of converting promising mineral resources into mineral reserves, which the market anticipates.

2017 - Diseño de planificación minera a cielo aberto de un yacimento aurífero considerando la incertidumbre geológica

Access here · Spanish · ¹ Allan Guillermo Odeñana Rocafuerte

¹ Escuela Superior Politécnica del litoral, Facultad de Ingeniería en Ciencias de la Tierra, Ecuador

Summary

El yacimiento de estudio, es un diseminado aurífero que ha sido explotado de forma subterránea, por lo que, se ha mermado la posibilidad de una mayor extracción de sus reservas minerales. También, esta explotación subterránea ha afectado la estabilidad del macizo rocoso, generando accidentes y una condición de riesgo latente. Se tienen datos de muestras geoquímicas del yacimiento que se han tomado de forma espacialmente irregular, lo que dificulta la interpretación geológica del depósito mineral. La hipótesis es que el yacimiento debe ser explotado a cielo abierto. La metodología utilizada consiste en discretizar el yacimiento en un modelo de bloques y estimar las leyes de los bloques por Kriging. Luego se escoge y diseña el método de explotación. Después se planifica el programa de producción y calcula el VAN del proyecto. Se modela la incertidumbre geológica a través de 20 simulaciones estocásticas de las leyes, sintetizadas en un modelo de bloques, para luego realizar la planificación minera estocástica, es decir calcular el pit final óptimo, su programa de producción y el VAN del proyecto bajo incertidumbre. Los principales resultados son que el VAN determinado por un método determinístico tiene una probabilidad de cumplimiento menor a 0.046%. El VAN esperado considerando la incertidumbre es de 1063 (M$), es decir que es 8.74% mayor al VAN esperado por un método determinístico y tiene un 80% de probabilidad de ser alcanzado. La optimización estocástica es una metodología relativamente reciente que ha demostrado obtener resultados satisfactorios, maximizando el valor de los proyectos y minimizando el riesgo.

Keywords: Planificación minera estocástica ; Minería a cielo abierto ; Programa de producción ; Incertidumbre geológica

2017 - Maximización de valor a través de la optimización del diseño de fases y plan de producción de una mina a tajo abierto

Access here · Spanish · ¹ Clider Niño Céspedes

¹ Pontificia Universidad Católica Del Perú, Facultad De Ciencias e Ingeniería

Summary

El presente trabajo de tesis corresponde a un estudio de rediseño de fases y optimización del plan de producción de una mina de oro a tajo abierto ubicada al norte del Perú. Es importante mencionar que la información publicada en esta tesis respecto al depósito y los resultados obtenidos de este estudio no corresponden necesariamente a la realidad. Previa a la explicación del caso de estudio, se describe información técnica de la mina respecto a temas relacionados a la geología y geotecnia, factores operativos, estructura de costos y una explicación teórica acerca del proceso de planificación minera a seguir a lo largo de la tesis.

Posteriormente, para el propósito principal de la tesis, se realizaron una serie de etapas estructuradas de la siguiente manera:

• Análisis de la información de entrada

• Solución del caso en estudio

• Análisis comparativo de resultados

• Conclusiones y recomendaciones

Estas etapas permitieron realizar la evaluación del caso inicial de los diseños de mina y el plan de producción para identificar posibles mejoras con el fin de maximizar el valor del proyecto en términos económicos y operativos. Luego de este análisis se planteó un nuevo caso de estudio que logre estos objetivos y que además satisfaga los requerimientos de corto plazo de la mina. Dicho caso fue ejecutado siguiendo una nueva metodología en planificación minera orientada a incrementar el valor de un yacimiento y optimizar los procesos de planificación minera tradicionales.

Finalmente, a través de un análisis comparativo de resultados entre el caso inicial y el nuevo caso de estudio se comprueba que se obtuvieron los resultados esperados en términos de valor y operatividad del nuevo plan de producción y diseño de mina elaborado.

2017 - Comparação entre métodos de cálculo de cava final: Lerchs Grossmann vs. Sequenciamento Direto de Blocos

Access here · Portuguese · ¹ Tiago Mozart Gonçalves Leite

¹ Centro Federal de Educação Tecnológica de Minas Gerais, Brazil

Summary

O estudo para delimitação da cava final de uma mina a céu aberto é uma etapa fundamental para um empreendimento mineiro. Nessa fase tenta-se definir a quantidade de estéril e minério que serão movimentados no projeto, com objetivo de maximizar a rentabilidade econômica do empreendimento. Até o final da década de 60 esse processo de delimitação de uma cava a céu aberto era feito por tentativa e erro, sendo um processo muito moroso e pouco preciso. No cenário atual, softwares de planejamento de lavra são utilizados para se efetuar esse tipo de análise, sendo que os principais programas no cenário da mineração são baseados no algoritmo desenvolvido por Lerchs e Grossmann no ano de 1965. Atualmente, o estado da arte do planejamento de lavra é baseado na metodologia clássica, onde existe uma sequência pré-determinada das atividades: construção do modelo de blocos, delimitação de cava final, construção dos push-backs, sequenciamento dos blocos. Esta metodologia determina a cava final considerando o fato inconcebível que todos os blocos serão lavrados no mesmo intervalo de tempo. A evolução da capacidade de armazenamento e velocidade de processamento dos computadores tem disponibilizado novas possibilidades ao planejamento de lavra. Com isso, a técnica do sequenciamento direto de blocos vem crescendo e tornando-se competitiva no mercado. Essa técnica integra todas as etapas e soluciona o problema do planejamento de lavra como um todo, sem a necessidade de divisão do planejamento de lavra em etapas interdependentes. Esse trabalho tem por objetivo comparar essas duas metodologias. Como ferramenta dessa comparação foram utilizados dois softwares distintos, o software Micromine, que utiliza o algoritmo de Lerchs e Grossmann (LG) e o software Simsched, que apresenta como método de otimização o sequenciamento direto de blocos (SDB). A partir da análise de um corpo de minério fictício, obteve-se um valor presente líquido (VPL) superior de 0,48% para a metodologia do SDB, em relação ao algoritmo de LG. Portanto o SDB foi mais interessante do ponto de vista financeiro. Outro fator observado que pesou a favor do SDB foi o fato de o aproveitamento do corpo de minério se dar em um menor intervalo de tempo (19 anos, contra 25 anos encontrado a partir de LG). Importante ressaltar ainda que houve uma movimentação de estéril 62,12% superior para o SDB.

Keywords: planejamento de lavra, cava final, sequenciamento direto de blocos, algoritmo de Lerchs-Grossmann.

2016 - Stochastic optimization of strategic mine planning of a hypothetical copper deposit through a parameterizable algorithm

Access here · Spanish · ¹ José Mario Pareja Zapata

¹Universidad Nacional de Colombia, Medellín, Colombia

Summary

Para realizar la planificación de una mina de superficie es necesario partir de una evaluación inicial del recurso mineral. La evaluación del secuenciamiento de una mina a cielo abierto es un paso clave en el proceso de planeación de las actividades de extracción de una empresa minera. Los enfoques tradicionales aplicados para definir el límite máximo de la fosa consideran un único modelo estimado, que se desvía de una evaluación real del activo mineral. En los últimos años, se propusieron nuevos enfoques, de modo que los beneficios de apartarse de la visión del mundo determinística, donde cada variable es estática y modelada desde un promedio aritmético, hasta una evaluación estocástica que permite comprender el riesgo asociado a la planificación minera a largo plazo. Los enfoques de optimización exacta se estudiaron debido a el rol crucial de la planificación minera en los analísis financieros, sin embargo se consideran las implicaciones asociadas con estos métodos y se propone un enfoque metaheurístico para resolver el caso de estudio.

2016 - Cut-off Grade Optimisation for a Bimetallic Deposit: A Case Study of the Ruashi Mine Copper-Cobalt Deposit

Access here · English · ¹ Daniel Mugwagwa

¹ University of the Witwatersrand, Johannesburg

Summary

Cut-off grade optimisation is very crucial for any mining organisation. Material is classified into rock, ore or product. Grade is the ratio of the amount of product to the amount of ore in which it is contained. There grade of mineralised block can be expressed as grams per tonne (g/tonne), as a percentage (%), metal equivalent grade per tonne or dollar value per tonne. Cut-off grade is the grade that is used to distinguish between ore and waste during scheduling. The cut-off grade is the main driver of value in a mining operation. High cut-off grade results in fewer reserves. It is important to optimise the cut-off grade during the mine life in order to optimise the net present value. There are various stakeholders who derive benefits from a mining operation whose interest must be considered during cut-off grade optimisation. The scenarios investigated have shown that running a mine based on break-even cut-off grade does not optimise the net present value of an operation as given by the results for Ruashi Mining. It has also been shown that royalty does affect the cut-off grade for Ruashi Mining. The grade-tonnage curve is steeper at the beginning implying a small change in cut-off grade has a huge impact on the reserves. Cut-off grade optimisation in SimSched results in a steeply declining cut-off grade policy compared to NPVS. The optimisation in SimSched results in a highly accelerated mining rate and massive stockpiling. But SimSched gives a higher NPV compared to the current Ruashi life of mine schedule. This implies SimSched can be used to improve the NPV for Ruashi by producing an optimised cut-off grade policy..

2016 - Sequenciamento Direto de Blocos: Impactos, Limitações e Benefícios Para Aderência ao Planejamento de Lavra

Access here · Portuguese · ¹ Felipe Ribeiro Souza

¹ Universidade Federal De Minas Gerais, Brazil

Summary

O sequenciamento de lavra é um importante procedimento do planejamento de lavra, que determina qual material será lavrado, a quantidade, e em qual período. Estas variáveis são altamente influentes no fluxo de caixa e consequentemente podem conduzir um empreendimento ao sucesso ou ao fracasso. Uma metodologia clássica, proposta inicialmente por Lerchs-Grossmann, define a quantidade total de material a ser lavrado sem considerar o período em que será executada a atividade e as restrições operacionais inerentes deste processo. Para suprimir as inconsistências desta metodologia, o Sequenciamento Direto de Blocos (SDB) propõe executar o planejamento de maneira mais eficiente e precisa, considerando os principais problemas da metodologia clássica: o fato da taxa de desconto e operacionalidade não estarem presentes na metodologia. O SDB é capaz de analisar cada bloco individualmente e aplicar-lhe as restrições econômicas e operacionais de maneira mais assertiva. Essa metodologia é capaz, em etapa única, de determinar o sequenciamento, não há a necessidade de determinar cava final e pushbacks antes do sequenciamento de lavra. A correta aplicação da taxa de desconto é responsável por diminuir a reserva mineral. Os blocos lavrados em tempos futuros são submetidos a um correto fator de desconto que reduzem a sua função benefício individual. Dessa forma, a busca por um melhor resultado financeiro promove a escolha dos blocos mais ricos de modo a contribuir para o aumento do Valor Presente Líquido. O aumento do valor econômico é acompanhado por restrições operacionais de modo a determinar um cenário mais assertivo a longo prazo com o sequenciamento direto de blocos. O presente trabalho propõe elaborar uma metodologia de trabalho de modo a executar um planejamento de lavra mais assertivo considerando as restrições operacionais e a correta taxa de desconto.

2013 - Surface Constrained Stochastic Life-of-Mine Production Scheduling

Access here · English · ¹ Alexandre Marinho de Almeida

¹ Department of Mining and Materials Engineering, McGill University , Montreal, Quebec, Canada.

Summary

The maximization of mining project discounted cash flows by defining the best sequence of extraction of underground materials requires understanding the availability of uncertain metal quantities throughout the deposit. This thesis proposes two versions of a stochastic integer programming formulation based on surfaces to address the optimization of life-of-mine production scheduling, whereby the supply of metal is uncertain and described by a set of equally probable simulated orebody models. The first version of the proposed formulation maximizes discounted cash flows, controls risk of deviating from production targets and is implemented sequentially, facilitating production scheduling for relatively large mineral deposits. Applications show practical intricacies and computational efficiency. The second variant extends the first to a two-stage stochastic integer programming formulation that manages the risk of deviating from production targets. The sequential implementation is considered first for pit space discretization and it is followed by the life-of-mine production scheduling at a relatively large gold deposit. The case studies show the computational efficiency and suitability of the method for realistic size mineral deposits, with production targets controlled, risk postponed to later stages of production and improvements in expected NPV, when compared to deterministic industry practices.