Open-pit Operations Research Articles

Evaluation of overall equipment effectiveness (OEE) for mining equipment (shovel-truck): A case study Manisa-Soma (Turkey) open pit mine

Mining is a costly activity that requires huge investments and large equipment. Therefore, it is crucial to use mining equipment efficiently to maximize productivity. This requires the continuous analysis of equipment efficiency and taking action to reduce negative impacts. Accurately estimating equipment efficiency is essential to increase its effectiveness. One globally recognized and accepted measurement is Overall Equipment Effectiveness (OEE). In this study was conducted to calculate the OEE values of shovels and trucks, which are the primary equipment used in open pit mining. The study presented different loss times and quality values while calculating the OEE values of mining equipment. The OEE values of electric trucks and shovels were found to be consistent with actual work quantities in the Manisa-Soma Lignite open pit operation. This study is the first applied study of OEE analysis in Turkey.

Evaluation of Coarse Gold-Bearing Conglomerate Mineralisation at Beatons Creek, Pilbara, Western Australia: Sampling for Resource Development and Grade Control

Many styles of gold mineralisation are challenging to sample because of the presence of coarse gold and a high spatial heterogeneity. The coarse gold-bearing conglomerates of the Beatons Creek deposit provide some challenges related to the presence of gold particles up to 8 mm and gold particle clusters (up to 500 mm3) at low in situ grades (<2 g/t Au). Novo has attempted to address these issues over the last six years of exploration, resource development and mining. The Beatons Creek open pit operation was the first Pilbara conglomerate-hosted gold deposit to go into production. Between January 2021 and September 2022, it produced 2.5 Mt at 1.2 g/t Au for 87,300 oz Au recovered. Gold is present within a matrix of multiple, narrow-stacked oxide and fresh (sulphide) conglomeritic reef horizons, which are interbedded with unmineralised conglomerate, sandstones and grits. It is strongly associated with detrital pyrite and authigenic nodules. Several sampling techniques have been applied across the project, including diamond core and RC drilling, trench channel sampling and bulk sampling. Assay methods applied include fire assay, screen fire assay, LeachWELL™ and more recently PhotonAssay™. The dominant sampling protocol applied for resource development and grade control utilised 0.5 m length RC samples; a 50% rig split (c. 8.5 kg) and laboratory crushing to 3 mm, followed by a 2.5 kg split and total assay via PhotonAssay™. For part of the 2022 RC programme, the detectORE™ technique was used to screen primary RC samples and reduce the feed to the laboratory. Novo operated a sampling and assay programme that aimed to reduce the impact of coarse gold on sample and assay preparation biases and to improve estimation.

Automation and Artificial Intelligence Technology in Surface Mining: A Brief Introduction to Open-Pit Operations in the Pilbara

Automation and Artificial Intelligence Technology in Surface Mining: A Brief Introduction to Open-Pit Operations in the Pilbara

Geological and Geomechanical Characterization of Phosphate Mine Waste Rock in View of Their Potential Civil Applications: A Case Study of the Benguerir Mine Site, Morocco

Sedimentary phosphate extraction in open-pit operations generates large volumes of waste rock (WR), which are mainly overburdens and interburdens. Traditionally, the WR is mixed and stored on the surface in waste rock piles (WRPs). This paper presents a case study of the Benguerir mine site in Morocco. It investigates the potential valorization of each WR lithology based on the geological and geomechanical properties to reduce their environmental footprint and create added value to “waste.” The WR samples (soils and rocks) were collected from drill cores and mining trenches in the Benguerir mine. The geological characterization results using petrographic descriptions indicate the presence of nine phosphate layers and, in addition to the overburdens, eight interburdens. Four types of WR are identified: carbonate, siliceous, marly clay, and phosphate. The geomechanical characterization of soil-like samples showed an average plasticity index (PI) of 50% according to the methylene blue value (MBV) of 7.1, classifying them in the A3–A4 categories as plastic and clayey marl soils. The hard rock samples have excellent mechanical properties in terms of their uniaxial compressive strength (UCS), Los Angeles abrasion value (LA), and micro-Deval value (MD). The average compressive strength is 104 MPa for the flint, 35 MPa for the phosphate flint, 32 MPa for the silexite, 26 MPa for the limestone, 11 MPa for the indurated phosphate, and 8 MPa for the marly limestone. Based on the obtained results, these WRs can be considered as an excellent alternative secondary raw material for use in civil engineering applications, ceramics, and cement industries.

A Multi-Stage Methodology for Long-Term Open-Pit Mine Production Planning under Ore Grade Uncertainty

The strategic planning of open pit operations defines the best strategy for extraction of the mineral deposit to maximize the net present value. The process of strategic planning must deal with several sources of uncertainty; therefore, many authors have proposed models to incorporate it at each of its stages: Computation of the ultimate pit, optimization of pushbacks, and production scheduling. However, most works address it at each level independently, with few aiming at the whole process. In this work, we propose a methodology based on new mathematical optimization models and the application of conditional simulation of the deposit for addressing the geological uncertainty at all stages. We test the method in a real case study and evaluate whether incorporating uncertainty increases the quality of the solutions. Moreover, we benefit from our integrated framework to evaluate the relative impact of uncertainty at each stage. This could be used by decision-makers as a guide for detecting risks and focusing efforts.

К методике обоснования границ между открытыми и подземными работами

Introduction. Currently, in the development of mineral deposits, the most widely used are open and underground methods. At the same time, open-pit mining is characterized by an extremely negative impact on the environmental situation, while at enterprises that develop deposits by underground methods, labor productivity is lower and, with some development systems, the extraction of minerals is much worse. The possibility of using open pit and underground works at one field makes it possible to use the advantages of each of the development methods, while reducing the negative factors of one of them at the expense of the other. The aim of the work is to assess the impact of technological solutions involving internal dumping on the establishment of a boundary between open pit and underground operations, taking into account the reduction of the technogenic impact on the environment. Methods for determining the boundaries of the open pit can be divided into 2 groups: the first includes methods for determining the boundaries of the open pit by the minimum total costs or the maximum total profit, the other includes methods using the boundary stripping ratio. In this work, when developing an economic-mathematical model, the methodology proposed by Professor A.I. Arsentiev, where profit is used as a criterion for the transition from open to underground work. As a result of the research, an economic-mathematical model was developed and tested to solve the problem of determining the boundary of the transition from open to underground work, based on obtaining additional profit by reducing environmental costs and taking into account the change in the order of dumping. Dependences have been obtained that reflect the change in the economically justified depth of the open pit on the degree of use of the mined-out space, as well as on the area of external dumps. The analysis of the obtained dependences shows that within the established limits and the given modeling parameters, the use of the worked-out space of the quarry allows to reduce the area of external dumps from 13 ha to 2 ha, while the boundary stripping ratio increases to 5.04, and the depth of the open pit increases from 105 m to 116 m. The results of the study can be used in the design of field development by open pit and combined methods.

Development of a geomechanical model based on suitable estimations of GSI and UCS in mining production slopes at the TilTil district, central Chile

The majority of applied geomechanical models are poorly suited for use in small-scale mining operations owing to the time, costs, and technical knowledge needed to usefully apply them. This means that it is often not possible to accurately obtain an adequate account of rock properties in advancing mining areas, which can lead to geomechanical related problems such as rockfalls and slope failures. Here we propose an adaptation to an existing methodology which allows the construction of a simple geomechanical model, that can be adjusted depending on mining developments, and used to develop recommendations for the design parameters of mining production slopes in small-scale open-pit operations. The adapted model, which considers the use of rock mechanics tests on rocks collected over a district level, along with UCS estimation, GSI characterization and FEM modelling, is based on an estimation of the parameters derived by1; namely material constants mi, mb, s, and a. Results show that the Uniaxial Compressive Strength (UCS), measured for rocks in the same district, serves as an adequate estimation of the specific UCS in the advancing mining area in the modified geomechanical model when both the field estimates and direct sampling are within a determined range.

Hydraulic Excavator Bucket Modeling with a Straight Shovel along a Defined Trajectory

With the active development of the mining sector, the share of open pit mining is increasing. It should be noted that the increase in the volume of open-cut mining depends on the volume and methods of excavation works. The main technological equipment performing up to 80% of the total volume of excavation and movement of minerals in open pit operations is hydraulic excavators. Consequently, efficient and highly productive operation of a hydraulic excavator directly affects the efficiency and profitability of mining operations. An important factor of development of mining industry today is to improve the reliability of technological machinery, namely energy efficiency, durability and maintainability of equipment. At the modern stage of development of mining equipment, the use of mine excavators with a hydraulic drive of the working mechanism occupies a wider and wider niche

Assessment of mine slopes stability conditions using a decision tree approach

Continuous assessment of slope stability is important to the open pit design and operation. This article aims to present a tool for evaluating the stability conditions of rock slopes in mining, based on a global geotechnical database, using machine learning techniques. Different models are evaluated in this research: the general model, which uses all variables; the mathematical model, which uses only variables selected by the random forest (out-of-bag); and two expert-based models: the Q-Slope model and the Santos model. The validation of the model was done through the test sample, using partition confusion matrices aiming at reproducibility of the results. A study of the types of errors was carried out using Principal Component Analysis (PCA). The study of errors allowed the identification of samples that were inconsistent with the others. Afterwards, the models were redone and compared with the previous ones. The best performers are presented and discussed. The proposed methodology does not replace the classic analysis of slope stability. On the contrary, it contributes to engineers and geologists with a tool for monitoring the stability conditions of slopes in a mining operation. Slope stability analysis must be carried out throughout the mine's lifetime and, therefore, it is believed that the tool proposed here can optimize the selection of slopes most susceptible to instability.

Data analysis as a basis for improving the efficiency of mining equipment in open pit operations

Data analysis as a basis for improving the efficiency of mining equipment in open pit operations

Geoenvironmental Model for Roll-Type Uranium Deposits in the Texas Gulf Coast

Geoenvironmental models were formulated by the U.S. Geological Survey in the 1990s to describe potential environmental effects of extracting different types of ore deposits in different geologic and climatic regions. This paper presents a geoenvironmental model for roll-front (roll-type) uranium deposits in the Texas Coastal Plain. The model reviews descriptive and quantitative information derived from environmental studies and existing databases to depict existing conditions and potential environmental concerns associated with mining this deposit type. This geoenvironmental model describes how features of the deposits including host rock; ore and gangue mineralogy; geologic, hydrologic, and climatic settings; and mining methods (legacy open-pit and in situ recovery [ISR]) influence potential environmental effects from mining. Element concentrations in soil and water are compared to regulatory thresholds to depict ambient surface water and groundwater conditions. Although most open-pit operations in this region have been reclaimed, concerns remain about groundwater quality at three of the four former mills that supported former open-pit mines and are undergoing closure activities. The primary environmental concerns with ISR mining are (1) radon gas at active ISR operations, (2) radiation or contaminant leakage during production and transport of ISR resin or yellowcake, (3) uranium excursions into groundwater surrounding active ISR operations, and (4) contamination of groundwater after ISR mining. Although existing regulations attempt to address these concerns, some problems remain. Researchers suggest that reactive transport modeling and a better understanding of geology, stratigraphy, and geochemistry of ISR production areas could minimize excursions into surrounding aquifers and improve results of groundwater restoration.

Sampling of high-nugget conglomerates from the Western Australian Pilbara: bulk sampling at the Beatons Creek gold project, Nullagine

Many styles of gold mineralisation pose challenges during sampling because of the presence of coarse gold and high natural heterogeneity (“nugget effect”). The gold-bearing conglomerates of the Western Australian Pilbara provide some challenges. Novo Resources Corporation has addressed many of these over the last five years. Its Beatons Creek open pit operation is the first Pilbara conglomerate to go into production (January 2021) based on a total oxide Mineral Resource of 316,000 oz Au (5.2 Mt at 1.9 g/t Au at a 0.5 g/t Au cut-off). Mineralisation occurs within the Beatons Creek conglomerate member of the Hardey Sandstone formation, which constitutes part of the Fortescue Group. Gold is present within the matrix of multiple, narrow stacked and un-classified ferruginous-conglomeritic reef horizons, which are interbedded with un-mineralised conglomerate, sandstones and grits with minor intercalations of shale, mudstone, siltstone and tuffs. The gold occurs as free particles up to 5 mm across within the ferruginous matrix of the conglomerates. It is closely associated with detrital pyrite and authigenic nodules. Previous owners and Novo have employed several sampling techniques across the project including diamond and RC drilling, trench channel sampling and bulk sampling. Assay methods included fire assay, LeachWELL and more recently PhotonAssay. As part of its 2018 evaluation programme, fifty-eight c. 1-4 t bulk samples were collected from accessible oxide mineralisation and processed via a pilot plant. This paper presents some of the issues and solutions applied by Novo, which have wider implications and impact on the sampling of other heterogeneous orebodies.

Column Generation for Mining Cut Definition with Geometallurgical Interactions

This work presents a novel approach to solve the mining cut definition problem with geometallurgical interactions in short-term mine planning for open-pit operations. Mining cut definition deals with the aggregation of blocks into clusters which are extracted and processed as a single unit. The aggregation must fulfill operational considerations given by the loading equipment selectivity and should maximize the objectives given by the mine operation. The proposed approach utilizes mixed integer programming and a model inspired by column generation that, contrary to previous works, has its decision variables defined directly on the set of all feasible cuts. The advantage of this is that the model does not require linear approximations of the geometallurgical behavior of the cuts based on the blocks it contains and, therefore, can utilize any nonlinear function. An industry-sized dataset is used to show that the model can be solved in reasonable time. Also, the results show that nonlinear recovery functions influence the destination policy and expected profit. Therefore, following the traditional free selection policy (based on cutoff grade) is not the best strategy when geometallurgical interactions are considered.

Precision Rock Excavation: Beyond Controlled Blasting and Line Drilling

The strictness of the result of an excavation, whether mechanical or by means of explosives, is naturally conditioned by its objective and, therefore, by the type of technique applied to achieve it. To attain the best results in terms of rock breakage, and with respect to the final profile, it is important to evaluate the specific excavation energy and its optimization. This study, being a revision of different techniques to achieve good quality of the final walls, focuses on evaluating the effects of those techniques on the quality of the result, in both open-pit and underground operations. Different geometries and configurations can be applied to both quarrying and tunneling blasts. This study aims to push contour blasts to their limits, and the main aspects are discussed in order to improve the blast parameters in daily practice.

Rock Fall Hazard Analysis for In-Pit Operations Potentially Impacting External Sensitive Areas

Controlling rockfall-related risks is a requirement for safe pit operations and primarily mitigated through adequate bench geometry design and implementation. This paper presents a method for rockfall hazard analysis for in-pit operations potentially impacting external sensible areas, adapted from natural rockfall hazard analyses. The method considers the natural susceptibility to rockfalls pre-mining, rockfalls originated from bench failures, and those initiated as flyrock. Rockfall trajectory models are used to estimate the potential for blocks reaching exposed elements. Natural susceptibility to rockfalls and trajectories are used as a baseline on which to evaluate the potential effects of open pit operations on the environment and perceptions of communities in the area. The method is illustrated for an open pit in steep terrain in the Peruvian Andes at a feasibility level of study. The paper illustrates the flexibility for including considerations of pre-mining rockfall impacts on the external elements of interest, and for developing rockfall mitigation strategies that consider rock block velocities, heights, energies and the spatial distribution of trajectories. The results highlight the importance of considering the three-dimensional effects of the terrain on block trajectories, and how such insights allow for increasing the efficiency of resources available for rockfall protection structures.

Blastability and Ore Grade Assessment from Drill Monitoring for Open Pit Applications

Blasting performance is influenced by mechanical and structural properties of the rock, on one side, and blast design parameters on the other. This paper describes a new methodology to assess rock mass quality from drill-monitoring data to guide blasting in open pit operations. Principal component analysis has been used to combine measurement while drilling (MWD) information from two drill rigs; corrections of the MWD parameters to minimize external influences other than the rock mass have been applied. First, a Structural factor has been developed to classify the rock condition in three classes (massive, fractured and heavily fractured). From it, a structural block model has been developed to simplify the recognition of rock classes. Video recording of the inner wall of 256 blastholes has been used to calibrate the results obtained. Secondly, a combined strength-grade factor has been obtained based on the analysis of the rock type description and strength properties from geology reports, assaying of drilling chips (ore/waste identification) and 3D unmanned aerial vehicle reconstructions of the post-blast bench face. Data from 302 blastholes, comprised of 26 blasts, have been used for this analysis. From the results, four categories have been identified: soft-waste, hard-waste, transition zone and hard-ore. The model determines zones of soft and hard waste rock (schisted sandstone and limestone, respectively), and hard ore zones (siderite rock type). Finally, the structural block model has been combined with the strength-grade factor in an overall rock factor. This factor, exclusively obtained from drill monitoring data, can provide an automatic assessment of rock structure, strength, and waste/ore identification.

Histogram Method for Determining the Location of the Internal Dump in Coal Open Pits

With the deepening of open pit mining, the volume of worked out space increases and, along with it, the potential capacity for storing overburden. At the same time, the pits completely allocated for the internal dumps are used only by the end of the period of the open pit operation. The known theoretical approaches to determining the location of the internal dump are little implemented in the practice of surface mining, which is explained by two reasons. First, standard design solutions are based on wellknown theoretical provisions; secondly, a formalized template approach to substantiating certain design developments in the field of dumping of internal dumps prevails, which pushes them towards their fragmentary rather than integrated implementation. With regard to the conditions of the Kuzbass open-pit mines, the article proposes a modernized interpretation for the formation of structural schemes of the sequence of quarry fields on the basis of constructive-and-parametric studies of a multivariate adaptation of the internal dumping mode.

Korkinsk Brown Coal Open Pit as a Case Study of Endogenous Fires

Abrupt termination of the coal open pit operation is complicated in many cases by endogenous fires that not only cause significant damage to property but also worsen sanitation and hygienic conditions for human life in nearby settlements, as well as those for fauna and flora. Therefore, the purpose of the research was to prevent endogenous fires at Korkinsk brown coal open pit. In this connection, we used an analytical method to process the statistical data obtained from observations. The laboratory method included the study of coal samples for moisture exchange intensity by creating conditions with relative humidity up to 97 %, temperature up to plus 50°С and air speed up to 0.5 l/minute. Dependencies were determined for fire occurrence frequency, relative humidity, and average temperature of the air upon the time of day, the intensity of moisture evaporation and initial coal humidity on equilibrium coal humidity as well as the intensity of moisture absorption and equilibrium coal humidity upon initial humidity in different temperature periods. An environmentally friendly solution was created that featured good adhesion to the materials being coated, fire and explosion resistance. The results obtained make it possible to understand the causes and methods of fighting endogenous fires.

Technological schemes of coal extraction in closed mines with the use of backhoes

At the present time on the fields of operating and closed-down mines there are sections of open-pit operations. However, the adopted technology does not meet environmental requirements, there are no scientific recommendations on the technology of open-pit mining in hazardous areas of mine fields, there is no substantiation of the boundary contours of open-pit mining. A characteristic feature of depleted mine fields is the disturbed rock mass and the lack of concentrated coal reserves within their boundaries. In fact, coal reserves are represented in the form of fragmentary volumes of safety pillars and substandard reserves in places of geological disturbances. Limitation of mine fields in terms of various infrastructure objects imposes special requirements for mining operations. In these conditions it is not possible to apply the classic mining systems and technologies. This predetermines the necessity to develop new technological solutions. Therefore, scientific research on justification of technology for extraction of remaining reserves of coal after underground development of inclined and steep-sloping coal deposits with simultaneous reclamation of disturbed lands is actual.

Energy method of assessing and systematizing open pit automobile transport operating conditions

Research aim is to develop the method of assessing and systematizing open pit automobile transport operating conditions. Research relevance. Pit depth growth and the introduction of modern models of dump trucks capable of working on 18–24% slopes complicate the conditions of industrial vehicles operation. In this regard, the development of the method and indicators of rock mass transportation difficulty becomes relevant as well as the systematization of vehicles operation conditions. Research methodology. The method of evaluating the difficulty of transportation is based on calculating diesel consumption per one haul cycle and reducing the actual length of the route to the relative horizontal distance with the use of rock mass vertical haul horizontal equivalents. Experimental and analytical dependences for horizontal equivalents have been determined. As a criterion of transportation difficulty evaluation, the use of operation conditions difficulty coefficient has been substantiated showing how many times truck’s power consumption when moving along the real route is higher than power consumption when moving along the horizontal macadamized route of the same length. Results. As a result of the research, the method of assessing and systematizing the operation conditions of open pit automobile transport. It has been determined that maximum values for conditions difficulty ISSN 0536-1028 «Известия вузов. Горный журнал», № 8, 2020 25 coefficients for the trucks with 4 × 2 wheel configuration are 2.6–3.0, and for all-wheel drive trucks – 5.0–6.5. By the difficulty coefficient, all operating conditions are divided into 5 classes (relatively easy, medium, difficult, very difficult, and extremely difficult). It has been determined that operating conditions in the most of diamond-mining open pits of ALROSA PJSC refer to class 3 and 4 (difficult and very difficult). The introduction of the all-wheel drive trucks will go along with the transition of operating conditions to class 5 (extremely difficult). For most of Ural pits classes 2 and 3 are typical (medium and difficult). Scope of results. Research results are to be used in open pit automobile transport design and operation when assessing and systematizing operating conditions, in technological calculations when regulating and planning diesel consumption and dump trucks capacity, and when correcting the regulatory standards of maintenance support, etc.