1,338 research outputs found
Economic Geology Models #3. Geological Contributions to Geometallurgy: A Review
Geometallurgy is a cross-disciplinary science that addresses the problem of teasing out the features of the rock mass that significantly influence mining and processing. Rocks are complex composite mixtures for which the basic building blocks are grains of minerals. The properties of the minerals, how they are bound together, and many other aspects of rock texture affect the entire mining value chain from exploration, through mining and processing, waste and tailings disposal, to refining and sales. This review presents rock properties (e.g. strength, composition, mineralogy, texture) significant in geometallurgy and examples of test methods available to measure or predict these properties.  Geometallurgical data need to be quantitative and spatially constrained so they can be used in 3D modelling and mine planning. They also need to be obtainable relatively cheaply in order to be abundant enough to provide a statistically valid sample distribution for spatial modelling. Strong communication between different departments along the mining value chain is imperative so that data are produced and transferred in a useable form and duplication is avoided. The ultimate aim is to have 3D models that not only show the grade of valuable elements (or minerals), but also include rock properties that may influence mining and processing, so that decisions concerning mining and processing can be made holistically, i.e. the impacts of rock properties on all the cost centres in the mining process are taken into account. There are significant costs to improving ore deposit knowledge and it is very important to consider the cost-benefit curve when planning the level of geometallurgical effort that is appropriate in individual deposits.RĂSUMĂLa gĂ©omĂ©tallurgie est une science interdisciplinaire qui sâintĂ©resse aux caractĂ©ristiques de la masse rocheuse qui influent de maniĂšre significative sur l'exploitation miniĂšre et le traitement du minerai. Les roches sont des mĂ©langes composites complexes dont les Ă©lĂ©ments structurant de base sont des grains de minĂ©raux. Les propriĂ©tĂ©s des minĂ©raux, la façon dont ils sont liĂ©s entre eux, et de nombreux autres aspects de la texture des roches dĂ©terminent l'ensemble de la chaĂźne de valeur miniĂšre, de l'exploration Ă l'extraction Ă la transformation, Ă l'Ă©limination des dĂ©chets et des rĂ©sidus, jusqu'au raffinage et Ă la vente. La prĂ©sente Ă©tude passe en revue les propriĂ©tĂ©s significatives de la roche (par ex. sa cohĂ©sion, sa composition, sa minĂ©ralogie, sa texture) en gĂ©omĂ©tallurgie ainsi que des exemples de mĂ©thodes d'essai disponibles pour mesurer ou prĂ©dire ces propriĂ©tĂ©s.  Les donnĂ©es gĂ©omĂ©tallurgiques doivent ĂȘtre quantitatives et localisĂ©es spatialement afin qu'elles puissent ĂȘtre utilisĂ©es dans la modĂ©lisation 3D et la planification de la mine. Elles doivent Ă©galement ĂȘtre peu couteuses afin d'ĂȘtre suffisamment nombreuses pour fournir une distribution d'Ă©chantillon statistiquement valide pour la modĂ©lisation spatiale. Une communication efficace entre les diffĂ©rents segments de la chaĂźne de valeur miniĂšre est impĂ©rative pour que les donnĂ©es soient produites et transfĂ©rĂ©es sous une forme utilisable et que les duplications soient Ă©vitĂ©es. Le but ultime est d'avoir des modĂšles 3D qui montrent non seulement la qualitĂ© des Ă©lĂ©ments prĂ©cieux (ou minĂ©raux), mais aussi les propriĂ©tĂ©s de roche qui dĂ©terminent l'exploitation miniĂšre et le traitement du minerai, de sorte que les dĂ©cisions concernant l'exploitation miniĂšre et le traitement du minerai peuvent ĂȘtre rĂ©alisĂ©es de façon holistique, c.-Ă -d. que lâimpact des propriĂ©tĂ©s de roche sur tous les maillons de la chaĂźne des coĂ»ts du processus minier sont prises en compte. Les coĂ»ts dâamĂ©lioration des connaissances sur le gisement de minerai Ă©tant importants, il faut tenir compte de la courbe coĂ»ts-bĂ©nĂ©fices lors de la planification du niveau d'investissement gĂ©omĂ©tallurgique appropriĂ© pour le gisement considĂ©rĂ©
ThreeâDimensional TimeâLapse Geoelectrical Monitoring of Water Infiltration in an Experimental Mine Waste Rock Pile
Open-pit mines often generate large quantities of waste rocks that are usually stored in waste rock piles (WRPs). When the waste rocks contain reactive minerals (mainly sulfides), water and air circulation can lead to the generation of contaminated drainage. An experimental WRP was built at the Lac Tio mine (Canada) to validate a new disposal method that aims to limit water infiltration into reactive waste rocks. More specifically, a flow control layer was placed on top of the pile, which represents a typical bench level, to divert water toward the outer edge. Hydrogeological sensors and geophysical electrodes were installed for monitoring moisture distribution in the pile during infiltration events. A three-dimensional (3D) time-lapse hydrogeophysical monitoring program was conducted to assess water infiltration and movement. Readings from the 192 circular electrodes buried in the WRP were used to reconstruct the 3D bulk electrical resistivity (ER) variations over time. A significant effort was devoted to assessing the spatiotemporal evolution of water ER because the bulk ER is strongly affected by water quality (and content). The water ER was used as a tracer to monitor the infiltration and flow of resistive and conductive waters. The results indicate that the inclined surface layer efficiently diverts a large part of the added water away from the core of the pile. Local and global models of water infiltration explaining both bulk and water ER variations are proposed. The results shown here are consistent with hydrogeological data and provide additional insights to characterize the behavior of the pile
Three-dimensional numerical study on the batter instability mechanism of Maddingley Brown Coal Open Pit, Victoria, Australia using PLAXIS 3D
With the increased size of excavation due to long-term open cut mining, batter instability has become a major geo-hazard in Victorian Brown Coal Open Pits where facilitate some largest brown coal mining operations in the world. Block failure is a unique failure mode in Victorian brown coal mines, which is often associated with cracks and rainfall. Maddingley Brown Coal Mine (MBC) is located in Bacchus Marsh, Victoria, Australia. Slope instability has also been a major geo-problem since the open pit mining commenced in MBC in 1940s. Making clear the cracking mechanism and the correlations between rainfall and batter instability have important implications in better understanding and predicting batter failures in Victorian brown coal mines. In this research, three-dimensional geologic models were developed to investigate the mechanism of brown coal batter instability. The finite element program encoded in Plaxis 3D was employed to conduct the complex two-phase (fluid-solid) coupled numerical simulations. The results revealed the cracking mechanism of coal batter and the effects of rainfall on batter stability. It was found that the brown coal batter with overburden tends to lead a circular critical path while the batter after overburden removal shows a trend of block sliding as interpreted by the shear and tensile strains simulated. The existence of joints and the hydrostatic water pressure in the joints could adversely affect the stability of brown coal batter towards block failure. Precipitation can increase the deformation, excess pore pressure, total pore pressure, active pressure and decrease the matric suction, and thereby decrease the shear strength, effective stress, and batter stability. The results from the three-dimensional hydro-mechanically coupled finite element study were well agreed with the field monitored data, theoretical calculations, and Victorian brown coal mining experience.Doctor of Philosoph
A Review on Applications of Time-Lapse Electrical Resistivity Tomography Over the Last 30 Years : Perspectives for Mining Waste Monitoring
"Mining operations generate large amounts of wastes which are usually stored into large-scale storage facilities which pose major environmental concerns and must be properly monitored to manage the risk of catastrophic failures and also to control the generation of contaminated mine drainage. In this context, non-invasive monitoring techniques such as time-lapse electrical resistivity tomography (TL-ERT) are promising since they provide large-scale subsurface information that complements surface observations (walkover, aerial photogrammetry or remote sensing) and traditional monitoring tools, which often sample a tiny proportion of the mining waste storage facilities. The purposes of this review are as follows: (i) to understand the current state of research on TL-ERT for various applications; (ii) to create a reference library for future research on TL-ERT and geoelectrical monitoring mining waste; and (iii) to identify promising areas of development and future research needs on this issue according to our experience. This review describes the theoretical basis of geoelectrical monitoring and provides an overview of TL-ERT applications and developments over the last 30 years from a database of over 650 case studies, not limited to mining operations (e.g., landslide, permafrost). In particular, the review focuses on the applications of ERT for mining waste characterization and monitoring and a database of 150 case studies is used to identify promising applications for long-term autonomous geoelectrical monitoring of the geotechnical and geochemical stability of mining wastes. Potential challenges that could emerge from a broader adoption of TL-ERT monitoring for mining wastes are discussed. The review also considers recent advances in instrumentation, data acquisition, processing and interpretation for long-term monitoring and draws future research perspectives and promising avenues which could help improve the design and accuracy of future geoelectric monitoring programs in mining wastes.
Slope Stability Enhancement of an Upstream Tailings Dam: Laboratory Testing and Numerical Modelling
Mine tailings are the byproduct of mining activities, which need to be disposed of once the ore is extracted. They can be disposed of in either dry or wet forms. The latter is most common with the tailings being disposed of in the form of slurry inside retention structures. The retention structure may be a natural, manmade, or built dam, which is the case in most of nowadays mining locations. In this thesis, improving the stability of an upstream tailings dam using soil additives is investigated. The experimental phase of this study involved laboratory tests conducted to characterize mine tailings and to investigate any change in their properties upon stabilization with traditional and non-traditional additives; namely, emulsified polymer and a mixture composed of Cement Kiln Dust, CKD, and re-cycled Gypsum. Afterwards, the soil modified parameters are used to establish finite element model employing the commercial code PLAXIS 2D to simulate the behavior of the improved soil when a tailings dam is formed. The numerical model demonstrated that utilizing CKD: B mix increased the overall stability tailingsâ impoundment and indicated it is very useful to construct robust dams yet being environmentally friendly
Modelling of hydraulic fracturing in unconventional reservoirs
Hydraulic fracturing (HF) is a process of fluid injection into the well in order to create tensile stresses in the rock to overcome the tensile strength of the formation. In this study, the development and application of a fuzzy model to predict the efficiency of hydraulic fracturing is presented with application in a coal mine as an unconventional reservoir. The most important parameters affecting the HF process of a coal seam are: dip, thickness, seam uniformity, roof and floor conditions, reserve of coal seam and coal strength. In the developed model, the efficiency of hydraulic fracturing of coal seams is calculated as a dimensionless numerical index within the range 0-100. The suggested numerical scale categorizes the efficiency of HF of seams to very low, low, medium, high and very high, each one being specified by a numerical range as a subset of the above range (0-100). HF in the coal bed in PARVADEH 4 Tabas mine in Iran is investigated as a case study. The results show that the developed model can be used to identify seams that have high potential for HF Moreover, a three-phase hydro-mechanical model is developed for simulating hydraulic fracturing. The three phases include: porous solid, fracturing fluid and reservoir fluid. Two numerical simulators (ANSYS Fluent for fluid flow and ANSYS Mechanical for geomechanical analysis) are coupled together to model multiphase fluid flow in hydraulically fractured rock undergoing deformations, ranging from linear elastic to large, nonlinear inelastic deformations. The two solvers are coupled, using system coupling in ANSYS Workbench. The coupled problem of fluid flow and fracture propagation is solved numerically. The fluid flow model involves solving the Navier-Stokes equations using the finite volume method. The flow model is coupled with the geomechanics model to simulate the interaction between fluid flow inside the fracture with rock deformations. For any time step, the pore pressures from the flow model are used as input for the geomechanics model for the determination of stresses, strains, and displacements. The strains derived from the gomechanics model are in turn used to calculate changes to the reservoir parameters that are fed as input to the flow model. This iterative process continues until both (fluid and solid) models are converged. The laboratory-scale study of hydraulic fracturing in the Second White Specks (SWS) shale was simulated using the developed model. The numerical and experimental results were compared. Comprison of the results shows that the numerical model can predict the behaviour of the shale under hydraulic fracturing with a good accuracy
Modelling of clogging in a permeable reactive barrier in acid sulfate soil terrain
This study contains laboratory, field and numerical methodology to determine the feasibility and performance of a permeable reactive barrier (PRB) utilising low cost recycled concrete aggregates for the remediation of acidic groundwater in acid sulfate soil (ASS) terrain. The PRB was installed in the Shoalhaven Floodplain about 100 km South of Sydney (Australia), in an area where acidic groundwater generation from pyritic soil poses a severe environmental and socio-economic problem
Design of inclined covers with capillary barrier effect
Abstract: A design procedure is proposed to minimize water infiltration into landfills in
optimizing the water diversion length of inclined covers with capillary barrier effect
(CCBE). This design procedure aims at selecting materials and optimizing layer thickness.
Selection among candidate materials is made based on their hydraulic conductivity
functions and on a threshold infiltration rate imposed on the designer. The capillary break
layer (CBL; bottom layer) is characterized by a weak capillarity, while the moisture
retention layer (MRL; upper layer) is characterized by a stronger capillarity. The thickness
of the CBL corresponds to the height where suction reaches its maximum value for a given
infiltration rate. This height can be calculated using the Kisch (1959) model. The optimal
thickness of the MRL is determined by applying an adaptation of the Ross (1990) model.
The results obtained using the proposed design procedure were compared to those obtained
from numerical simulations performed using a finite element unsaturated seepage software.
The procedure was applied for two cover systems; one where deinking by-products (DBP)
were used as MRL and sand as CBL and another where sand was used as MRL and gravel
as CBL. Using this procedure, it has been shown that an infiltration control system
composed of thin layers of sand over gravel is highly efficient in terms of diversion length
and that its efficiency can be enhanced by placing a hydraulic barrier - such as a layer of
DBP - above the MRL
Ăvaluation de la performance d'un systĂšme de recouvrement monocouche avec nappe surĂ©levĂ©e pour la restauration d'un parc Ă rĂ©sidus miniers abandonnĂ©
La production de drainage minier acide dans les parcs Ă rĂ©sidus miniers abandonnĂ©s peut causer des dommages environnementaux sĂ©vĂšres. Les rĂ©sidus peuvent dans certains cas gĂ©nĂ©rer des contaminants pendant des centaines, voire des milliers dâannĂ©es si aucune action nâest entreprise pour les contrĂŽler. Des pH acides et des eaux trĂšs chargĂ©es en ions tels le fer, les sulfates et souvent dâautres mĂ©taux et mĂ©talloĂŻdes sont retrouvĂ©s sur certains sites abandonnĂ©s ayant produit extensivement du drainage minier acide durant plusieurs dĂ©cennies. Des mesures de restauration peuvent ĂȘtre appliquĂ©es pour contrĂŽler la production de drainage minier acide, dont les principales sont lâimplantation dâun recouvrement en eau, dâune nappe phrĂ©atique surĂ©levĂ©e combinĂ©e Ă un recouvrement monocouche ou dâune couverture Ă effets de barriĂšre capillaire.
Le site minier abandonnĂ© Manitou (1942-1979) possĂšde un parc Ă rĂ©sidus qui produit du drainage minier acide riche en sulfates, en fer et en zinc. La restauration des zones basses du site (dâĂ©panchement) consiste Ă mettre en place une nappe phrĂ©atique surĂ©levĂ©e combinĂ©e Ă une couverture monocouche constituĂ©e de rĂ©sidus fins et non gĂ©nĂ©rateurs de drainage contaminĂ© provenant de la mine Goldex. La performance de cette technique se base sur le maintien de la nappe phrĂ©atique prĂšs de la surface des rĂ©sidus rĂ©actifs afin de conserver les rĂ©sidus saturĂ©s et de restreindre lâapport dâoxygĂšne qui alimente les rĂ©actions dâoxydation des sulfures. Cependant, plusieurs incertitudes sont liĂ©es Ă la performance de la restauration du site Ă limiter la production de contaminants en raison de lâĂ©mergence de la technique utilisĂ©e et de la production extensive de drainage minier acide sâĂ©tant produite sur le site durant une longue pĂ©riode de temps.
La prĂ©sente Ă©tude consiste Ă Ă©valuer la performance sur le terrain de la technique de la nappe phrĂ©atique surĂ©levĂ©e combinĂ©e Ă un recouvrement monocouche. On a vĂ©rifiĂ© Ă lâaide dâun modĂšle numĂ©rique lâeffet de la variation de diffĂ©rents paramĂštres sur le comportement hydrogĂ©ologique du site en lien avec la performance de la technique de restauration. De plus, le comportement hydrogĂ©ologique et la migration de lâoxygĂšne ont Ă©tĂ© Ă©valuĂ©s sur le terrain La qualitĂ© de lâeau a aussi Ă©tĂ© suivie sur le terrain et dĂ©terminer les principaux phĂ©nomĂšnes gĂ©ochimiques influençant la qualitĂ© de lâeau aprĂšs la restauration. Les trois chapitres du corps de la thĂšse portent respectivement sur ces trois aspects.
Un modĂšle numĂ©rique reprĂ©sentatif du parc 2 du site Manitou a Ă©tĂ© dĂ©veloppĂ©. Ce modĂšle a Ă©tĂ© utilisĂ© pour effectuer des simulations hydrogĂ©ologique du site. Le calage du modĂšle a Ă©tĂ© effectuĂ© avec les rĂ©sultats de niveaux phrĂ©atiques mesurĂ©s sur trois ans Ă treize endroits sur le site. Les simulations ont permis dâĂ©valuer lâeffet de la variation de certaines propriĂ©tĂ©s des matĂ©riaux mesurĂ©es sur le terrain, telles la conductivitĂ© hydraulique saturĂ©e, la porositĂ© et la distribution granulomĂ©trique. Des Ă©carts entre les niveaux phrĂ©atiques simulĂ©s par rapport Ă ceux du scĂ©nario de base (qui reprĂ©sente les mesures terrain) ont Ă©tĂ© observĂ©s surtout dans les cas oĂč les matĂ©riaux du recouvrement sont lĂąches ou grossiers. Des rĂ©ponses Ă long terme des niveaux phrĂ©atiques ont aussi Ă©tĂ© simulĂ©es selon les donnĂ©es climatiques normales, en simulant des pĂ©riodes de sĂ©cheresse rĂ©currentes et selon les changements climatiques anticipĂ©s. Les mesures terrain et les rĂ©sultats de simulation du climat normal montrent une zone Ă lâouest du site avec des niveaux phrĂ©atiques pouvant ĂȘtre sous lâinterface entre les rĂ©sidus et le recouvrement en Ă©tĂ©. Cette zone est accrue lors de pĂ©riodes de sĂ©cheresse et selon un scĂ©nario de changements climatiques simplifiĂ©s.
Le comportement hydrogĂ©ologique et de migration de lâoxygĂšne a aussi Ă©tĂ© suivi sur le terrain dâaoĂ»t 2012 Ă aoĂ»t 2015. Treize stations instrumentĂ©es ont Ă©tĂ© mises en place avec de lâĂ©quipement pour mesurer le niveau phrĂ©atique, les teneurs en eau volumiques et les succions dans le recouvrement, les concentrations dâoxygĂšne interstitiel Ă diffĂ©rentes profondeurs dans le recouvrement et la consommation dâoxygĂšne. Les mesures de teneurs en eau, de succions et de niveaux piĂ©zomĂ©triques ont montrĂ© que les niveaux phrĂ©atiques varient saisonniĂšrement et se retrouvent souvent dans les rĂ©sidus rĂ©actifs dans une zone Ă lâouest du site en Ă©tĂ©. Les cinquante centimĂštres infĂ©rieurs du recouvrement demeurent cependant toujours prĂšs de la saturation en eau. La migration de lâoxygĂšne a Ă©tĂ© Ă©valuĂ©e par les mesures de concentrations dâoxygĂšne interstitiel gazeux dans le recouvrement et les essais de consommation dâoxygĂšne. Les flux dâoxygĂšne atteignant les rĂ©sidus Manitou ont Ă©tĂ© dĂ©terminĂ©s par des mĂ©thodes numĂ©riques et analytiques. Leur moyenne annuelle au cours de la pĂ©riode Ă lâĂ©tude est selon lâendroit sur le site de 3 Ă 10-6 Ă 2 g/m2/an. Ces valeurs sont au moins un ordre de grandeur infĂ©rieur aux critĂšres gĂ©nĂ©ralement appliquĂ©s sur les parcs Ă rĂ©sidus pour contrĂŽler la production de drainage minier acide.
La qualitĂ© de lâeau interstitielle a aussi Ă©tĂ© suivie dâaoĂ»t 2012 Ă aoĂ»t 2015. Des pH prĂšs de la neutralitĂ© ont Ă©tĂ© mesurĂ©s, alors que des pH acides Ă©taient observĂ©s avant les travaux de restauration. Les concentrations de cuivre sont aussi nĂ©gligeables par rapport Ă des concentrations jusquâĂ 235 mg/L mesurĂ©es avant les travaux de restauration. Cependant, les concentrations de fer demeurent Ă©levĂ©es (majoritairement de 100 Ă 2000 mg/L) et stables, tandis que les concentrations de zinc sont aussi Ă©levĂ©es (0,3 Ă 1650 mg/L) et prĂ©sentent une lente dĂ©croissance. Cette diminution nulle ou faible des concentrations de fer et zinc peut ĂȘtre expliquĂ©e dâune part par la dissolution de minĂ©raux secondaires, tels la jarosite et des oxyhydroxydes de fer, qui peuvent contenir du zinc en impuretĂ© et sont instables dans les conditions gĂ©ochimiques au
parc 2 aprĂšs les travaux de restauration. Lâoxydation des sulfures par le fer ferrique et des interactions galvaniques peuvent aussi continuer Ă les dissoudre sans oxygĂšne.
Ce projet a permis dâapprofondir la comprĂ©hension de la technique de la nappe surĂ©levĂ©e combinĂ©e Ă un recouvrement monocouche appliquĂ©e Ă grande Ă©chelle sur un parc Ă rĂ©sidus abandonnĂ©. Il a Ă©tĂ© dĂ©terminĂ© que la technique de restauration appliquĂ©e constitue une barriĂšre Ă lâoxygĂšne efficace. Les niveaux phrĂ©atiques mesurĂ©s Ă©taient aussi toujours prĂšs ou supĂ©rieurs au niveau cible, qui est lâinterface entre les rĂ©sidus Manitou et le recouvrement. Une diminution des concentrations de fer et de zinc dans lâeau interstitielle est cependant requise afin dâatteindre les critĂšres environnementaux Ă lâeffluent. Les stratĂ©gies de restauration de sites contenant des rĂ©sidus oxydĂ©s devraient prendre en compte le potentiel de solubilisation de minĂ©raux secondaires et les rĂ©actions sans oxygĂšne pouvant survenir avec les sulfures pour rĂ©duire la production de contaminants potentielle aprĂšs les travaux de restauration
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