Dissertations / Theses on the topic 'Bauxite mine'

[Truncated abstract] Landforms rehabilitated after bauxite mining can be vulnerable to soil loss by water erosion processes. On most rehabilitated sites, management controls such as deep ripping, contour mounding and landscaped sub-catchments limit erosion. Despite these measures, severe gully erosion that is anecdotally associated with steep slopes can damage rehabilitated areas and affect downstream drinking water resources. A review of erosion dynamics reveals that gullies develop episodically and in a non-linear manner. They often initiated as a near surface process and are influenced by natural climatic drivers. Despite this, local site characteristics including soil and landform can predispose an area to gully erosion. Moreover, erosion models, becoming more-widely utilized within the mining industry, may provide useful tools with which to measure, analyse, and manage gully erosion. One of these models, SIBERIA was tested to determine its suitability for application a tool to help manage erosion risk. We first surveyed 26 eroding and erosion-prone rehabilitated hillslopes to determine the common form and setting for gully erosion on these rehabilitated bauxite mines. A conceptual model was developed to include and explore the interplay between the common causes of the gullies surveyed. The conceptual model accounts for slope steepness but suggests that additionally, certain triggers and threshold effects operating under different site conditions are as influential (or even more influential) than slope steepness as determinants of gully erosion occurrence and severity. ... Soil properties and soil erodibility had some subtle influence on landform stability and erosion risk. The most-erodible media occurred where either: mine floor material was mixed with topsoil/ overburden; and/or the topsoil/overburden layer was thin or its coverage is patchy resulting in slaking subsoil, hardsetting soil and surface crusts. When erodible surface media were combined with steeper (>8[degrees]) or longer (>50 m) slopes or with any major erosion trigger, rill and gully development was greatly intensified. The SIBERIA simulation model was calibrated and its simulated outputs were compared to known locations of gully erosion on a steep, rehabilitated pit from the Willowdale mine. At a resolution of one metre, SIBERIA was able to simulate the approximate dimensions of gullies. However, SIBERIA could not simulate the exact location of individual gully headcuts. Additionally, SIBERA was able to simulate the effect of different microtopographic surface treatments but this was only achieved by increasing the grid resolution to 25 cm and reducing the size of the area simulated due to model constraints. Locations of gully headcuts were overlain onto a grid-based, Digital Elevation Model (DEM) using a Geographic Information System (GIS). The spatial distribution of gully headcut locations was compared to DEM derivatives such as slope and flow accumulation. Positive, and predictive relationships allow between the steepness of the slope of the pre-mining landform and the cell count of the area contributing to flow (catchment), as determined by GIS, may allow a mine scale indication of erosion risk using simple GIS desktop analysis.

[Truncated abstract] Industrial processing to refine alumina from bauxite ore produces millions of tonnes of refining residue each year in Australia. Revegetation of bauxite residue sand (BRS) is problematic for a number of reasons. Harsh chemical conditions caused by residual NaOH from ore digestion mean plants must overcome extremely high pH (initially >12), saline and sodic conditions. At such high pH, manganese (Mn) is rapidly oxidised from Mn2+ to Mn4+. Plants can take up only Mn2+. Thus, Mn deficiency is common in plants used for direct BRS revegetation, and broadcast Mn fertilisers have low residual value. Added to this, physical conditions of low water-holding capacity and a highly compactable structure make BRS unfavourable for productive plant growth without constant and large inputs of water as well as Mn. However, environmental regulations stipulate that the residue disposal area at Pinjarra, Western Australia, be revegetated to conform with surrounding land uses. The major land use of the area is pasture for grazing stock. Hence, pasture revegetation with minimum requirement for fertiliser and water application is desirable. This thesis investigates a number of avenues with potential for maintaining a productive pasture system on BRS whilst reducing the current level of Mn fertiliser and irrigation input. Emphasis was placed on elucidation of chemical and physical factors affecting Mn availability to plants in BRS

Dans cette thèse, une nouvelle loi d'endommagement en traction des roches sous chargement exploisif est établie. Basée sur l'approche micro-mécanique et énergétique, la loi d'évolution d'endommagement dynamique est conçue à l'aide de la méthode mathématique d'homogénéisation basée sur le développement asymptotique, et en tenant compte de l'effet inertiel lors de la propagation de fissure. Les simulations numériques sont présentées en vue d'illustrer la capacité du modèle à décrire les comportements connus comme les effets de taille pour la réponse structurelle, la sensibilité au taux de déformation, la transition fragile-ductile et la dispersion de l'onde.

La loi est implémentée dans le code aux éléments finis LAGAMINE pour étudier la réponse macroscopique du modèle. Plusieurs cas d'applications en dynamique ont été examinés.\\

- En 1D, les problèmes de localisation ont été étudiés dans une barre sollicitée en traction dynamique par une rampe de chargement. Selon l'amplitude de chargement, trois réponses ont été identifiées: a) comportement purement élastique pour des faibles charges, b) localisation à l'extrémité encastrée de la barre pour des chargements modérés et c) localisation à la tête de la barre pour des chargements élevés. L'influence de la taille microstrurelle sur la localisation a été examinée. Des simulations numériques de l'essai de traction dynamique par écaillage ont été éffectuées. Des essais expérimentaux de traction dynamique par écaillage ont été réalisés sur la bauxite et ont permis de valider le modèle en comparant l'analyse post mortem de l'éprouvette aux résultats des simulations numériques d'écaillage. Ces essais ont aussi permis de déterminer les caractéristiques mécaniques du matériau, la résistance mécanique en traction dynamique, l'instant de rupture et la vitesse de déformation à rupture.\\

- En 2D, des simulations numériques sont efféctuées pour reproduire le comportement d'une mine sous charge explosive. Le modèle a été capable de reproduire l'endommagement en traction sous charge explosive. L'influence des paramètres du modèle tels que: l'orientation de fissures, la taille de microstructure et la valeur initial d'endommagement sur la distribution de l'endommagement autour du trou de charge a été étudiée. Enfin, un cas d'application sur les mines de bauxite de Guinée a été étudié, incluant un calcul de l'extension de la zone endommagée ainsi qu'une prédiction numérique du niveau de vibration engendrée suite aux tirs à l'explosif. La prédiction du modèle est globalement en accord avec les résultats de la littérature.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished

[Truncated abstract] Recovery of soil nutrients, microbial populations and carbon (C) and nitrogen (N) cycling processes are critical to the success of rehabilitation following major ecosystem disturbance. Bauxite mining represents a major ecosystem disturbance to the jarrah (Eucalyptus marginata) forest in the south-west of Western Australia. Mining has created a mosaic of mined areas in various stages of succession surrounded by non-mined forest areas. Initial site preparations within rehabilitation areas such as contour ripping alter soil structure (creation of mound and furrows) and over time also influence the distribution of vegetation and litter. Current performance criteria developed by industry, government and other stakeholders have determined that before post-bauxite mined areas of jarrah forest can be integrated back into normal forest management practises they should be functional and demonstrate resilience to normal forest disturbances such as fire. Furthermore, resilience should be of a manner comparable to non-mined analogue forest sites. Currently little is known of the resilience of microbial communities and C and N cycling in rehabilitation sites to normal forest disturbances such as prescription burning. As such, before rehabilitated jarrah forests can be successfully integrated into broad scale forest management regimes, a more thorough knowledge of the potential impacts of burning practises on the soil microbial community and C and N cycling processes in these systems is required. ... While there are similar rates of C and N cycling the underlying microbial community structure was distinctly different; implying a high degree of functional redundancy with respect to C and N cycling. Differences in the C and N cycling and structure of the microbial communities were likely to be due to differences in soil environmental conditions (i.e. soil alkalinity/acidity, soil moisture) and C substrate availability which influence the physiological status of the microbial community and in turn are related to successional age of the forests. Results also suggest that the measurement of CLPP can be a useful approach for assessment of changes in the functional ability of microbial communities. However, the interpretation of how well these rehabilitation forests have recovered heterotrophic abilities was greatly affected by the methodological approach used (e.g. MicroRespTM or Degens and Harris, 1997). Importantly, results from Chapter 4 and 5 suggested that the effects of a moderate prescription fire on C and N processes, CLPP and microbial community structure of 18 year old rehabilitation forests are likely to be short-lived (< 2 years). Furthermore, the effects of the moderate spring prescription fire were not large enough to decouple C and N cycling processes over the short-term (< 1 years) which suggests that by 18 years of age rehabilitation forests demonstrate comparable functional resilience to a moderate prescription burn.

La bauxite et l'alumine représentent des ressources vitales pour les économies en développement. La mise en valeur des réserves se fait par l'intermédiaire des entreprises multinationales. La position de l'industrie au centre de complexe militaro-industriel, les conditions de l'approvisionnement, son contrôle de processus de la mise en valeur sur le plan mondial ont permis aux entreprises de dominer leurs relations avec les gouvernements. Le droit international ne doit pas être un détour permettant de généraliser la privatisation du pouvoir économique. L'affirmation du primat de développement semble fournir l'explication de l'inaliénabilité de la souveraineté sur les ressources naturelles. L'internationalisation doit avoir pour but la publicisation du contrat de développement, la soumission du contrat au droit international par attraction de la personnalité de l'état, défenseur de l'intérêt national doté de prérogatives de souveraineté
Bauxite and alumina are vital resources for underdeveloped economies. Bauxite is exploited by multinational entreprises. The position of the aluminium industry in the military complex, its contrat of the processus of exploitation of the mineral permitted multinational entreprises to dominate their relations with the governments. Inalienability of the souvereignty on natural resources confers to state contracts a public character. In no system of law are private interests permitted to prevail over duly established public interest making impossible actions required for public good

Ce travail de thèse est consacré aux conséquences sociales et politiques de l’exploitation minière de la bauxite en Guinée. Quelques années avant son indépendance en octobre 1958, la Guinée est devenue membre d’un réseau mondial de production incluant mines, raffineries, fonderies et usines, métallurgiques, toutes contrôlées par un petit nombre de sociétés multinationales interconnectées. Ce travail de recherche se penche sur les conséquences politiques et sociales de ce processus d’intégration dans une filière globales aboutissant à la production de voitures, de boîtes de conserve, d’avions, de bâtiments ou d’autres produits en aluminium. Au-delà du contrôle extérieur existant de fait sur les différentes villes productrices de bauxite, les trois mines de bauxite de Guinée ont également été la source des principales recettes depuis l’indépendance et ont de ce fait un impact décisif sur l’histoire du pays. Afin de mettre en évidence ces interconnections et rapports de force, la thèse interroge (1) les intérêts des pays producteurs et importateurs ainsi que des institutions internationales en jeu (2) les formes de gestion des risques et les stratégies de maximisation du profit (chain governance) des multinationales et (3) les formes de renégociation et les effets de ce réseau mondial de production au niveau local
This is a thesis on the social and political consequences of bauxite mining in Guinea . A few years before independance in October 1958, Guinea became part of a worldwide production network of mines, refineries, smelters and metal-working factories which where all controlled by a few interconnected companies. The thesis focuses on the political and social consequences of this inclusion into global commodity chain which results in cars, cans, airplanes, building and other things made out of aluminium. Beside the de facto foreign control over several bauxite towns, the three Guinean bauxite mines also provided also most governmental income since independance and had thereby a strong impact on the history of this country. In order to show these interconnections the thesis treats (1) the intrests of producer countries, receiver countries and international institutions (2) risk management and profit maximizing strategies (chain governance) of transnational companies and (3)the renogatiation and the effects of this global production network on the local level

Le résidu de bauxite communément appelé boue rouge est un déchet industriel généré lors de la production d'alumine. Le stockage de ces déchets est considéré comme un important problème environnemental, notamment du fait de la nature caustique du matériau (pH >10) et des quantités générées (d’environ 1,5 t par tonne d’alumine produit). La production de l’alumine vénézuélienne (par CVG Bauxilum) a ainsi généré plus de 15 millions de m3 de résidus de bauxite. Paradoxalement, aucune recherche n’a encore été menée sur les propriétés de ces résidus en tant que matériau pouvant être utilisé dans le domaine environnemental. Les objectifs principaux de ce travail de thèse sont une caractérisation physico-chimique du résidu de bauxite vénézuélienne (fraction solide) ainsi qu’une évaluation des options de valorisation, notamment comme agent de remédiation des systèmes pollués. Une approche intégrée couplant la chimie, la minéralogie, le pH, la granulométrie, la surface spécifique et le contenu en radionucléides, avec des études de spéciation chimique et de biodisponibilité, a permis de mettre en évidence certaines des caractéristiques très importantes notamment 1) une teneur élevée en Th et U et leur isotopes respectifs Th232 et U238, ainsi qu’en lanthanides 2) le risque potentiel chimiotoxique du résidu vis-à-vis de fractions très labiles pour des éléments tels que l’aluminium et l’uranium 3) des propriétés de sorption intéressantes vis à vis d’éléments toxiques, Pb, Zn et As, du fait de la grande surface spécifique du résidu, notamment en milieu acide (cas d’un drainage minier acide). L’ensemble des résultats de ce travail, a montré que l’utilisation potentielle des résidus de bauxite vénézuélienne dans des domaines clés tels que l'assainissement des systèmes pollués (comme amendement ou un agent sorbant) et dans la récupération de métaux d’intérêt économique pourrait être une voie possible pour la valorisation de ce déchet
The bauxite residue commonly called ‘red mud’ is an industrial waste generated during the production of alumina. The storage of this waste is considered as a major environmental problem, especially because of its caustic nature (pH> 10) and the huge produced quantities (about 1.5 t per tonne of alumina produced). The production of Venezuelan alumina (CVG Bauxilum) has generated more than 15 million m3 of bauxite residue. Moreover, no research has yet been conducted on the properties of these residues and their utilization in the environmental field. The main goals of this study focus on the physical and chemical characterization of Venezuelan bauxite residue (solid fraction) and in an evaluation of its applications as an agent for remediation of polluted systems. An integrated approach coupling chemical composition and adsorption properties, mineralogical phases, particle size, surface area and radionuclide content with studies of chemical speciation and bioavailability, yielded significant constraints including: 1) a high content of U and Th, and their respective isotopes Th232 and U238, as well as lanthanides 2) the potential risk of residue chemotoxicity towards a very labile fraction of elements such as aluminum and uranium 3) high sorption properties with respect to toxic elements, Pb, Zn and As, due to the large surface area of the residue, especially under acidic conditions (case of acid mine drainage). These results have shown the potential use of Venezuelan bauxite residue in key areas such as remediation of polluted systems (as amendment or sorbent agent) and in the recovery of metals of economic interest

[Truncated abstract] The assessment of rehabilitation success is time consuming and costly for bauxite miners because large areas of land (~550 ha per year) are involved. In some cases, rehabilitation results in patches of bare or sparsely vegetated soil. This study uses remote sensing imagery to evaluate the growth of vegetation in rehabilitated bauxite mines in the Darling Range, W.A. This work has five aims, which are to (1) compare vegetation biomass within rehabilitated areas and nearby native forest; (2) analyse temporal changes in vegetation growth within the selected rehabilitated areas, in particular rehabilitated areas with patches of bare soil; (3) compare vegetation growth pre- and post- mining; (4) identify the best type of remotely sensed data for this particular study area, and (5) develop an index, which can classify the degree of vegetation patchiness within rehabilitated mine sites. This information will enable rehabilitation workers to identify patches in rehabilitated areas that may require further remediation. The study used RADARSAT, nine years of Normalised Difference Vegetation Index (NDVI) maps (extracted from LANDSAT TM multivariate imagery and Quickbird imagery) and aerial photographs to evaluate forty-seven ~1 ha study sites. Image and map analyses were conducted mainly using ESRI’s software ArcGIS 8.3 and ER Mapper 6.4. Ground truthing was carried out to confirm and recognise the causes of bare patches within the rehabilitated mine sites ... The results indicate that differences in rehabilitation management do not affect this index but the extent of bare patches does. Due to the sensitivity of radar imagery to surface roughness, rehabilitated areas cannot be distinguished from the native forest using radar images. A building (crusher) appears to be the same as mature vegetation. Knowledge of the features in an area is therefore crucial when utilising RADARSAT. The beam elevation angle and profile of the RADARSAT image used, made superimposition of radar and optical imageries impossible. Speckle noise in RADARSAT images made it impossible to detect relatively small bare patches. In addition, the many cloud free days in Western Australia make optical imaging possible so that the ability of radar imagery to penetrate cloud is redundant for this type of study.

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CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico
SEDECT/PA - Secretaria de Estado de Desenvolvimento, Ciência e Tecnologia
O objetivo desta dissertação consiste no estudo das dinâmicas e inter-relações entre colônias do Oriente e Potiritá no contexto do Projeto Bauxita de Paragominas. Partindo deste prisma o estudo se concentra nas comunidades no entorno do Platô Miltonia Três, onde se concentra a exploração de Bauxita levando em consideração a área do mineroduto que abrange o município de Paragominas. Neste estudo é abordado a inter-relação da empresa privada, no âmbito da exploração mineral, representada pela VALE - através do Projeto bauxita de Paragominas, com o poder local consubstanciado pela gestão municipal (prefeitura), e destes com as comunidades. Para efeito de analise utilizou-se a pesquisa qualitativa e o método etnográfico valendo-se de técnicas como o roteiro de entrevista dentre outras, visando apreender os meandros da participação e o significado das inter-relações. Consideraram-se as categorias conflito, poder e participação das comunidades rurais no sentido de apreender o seu significado no contexto estudado. Essas análises permitiram compreender como ocorre a capacidade de intervenção das mesmas, face aos problemas sociais que os atingem, suas reivindicações, e seus anseios. Conclui-se que a participação como cidadãos e o acesso a informação geram responsabilidades e os torna responsáveis e capazes de transformar a realidade. Em especial uma transformação coerente com projetos sociais que os favoreçam.
This dissertation studies the dynamics and interrelations between the colonies of “Oriente” and “Potiritá” within the frame of the Bauxite Project of Paragominas. The study focuses on the communities around Platô Miltonia 3, where the bauxite exploitation is centered, taking into consideration the area of the mineral pipe system running through the municipality of Paragominas. The study examines the interrelation of private mineral companies, in this case represented by VALE, through the Bauxite Project of Paragominas, with local power represented by the city management council (“prefeitura”) and the communities. The methods used in this analysis are qualitative research and ethnographic method; techniques such as interview scripts and others were also used in order to identify participation characteristics and the meaning of interrelations. Conflict, power and rural community participation were the categories considered in this analysis, in order to learn their meaning within the studied framework. The analysis allowed us to understand how the intervention capacity occurs when facing social problems, claims and wishes. The conclusion leads us to say that participation as citizens and access to information create responsibilities, making individuals responsible for their acts and capable of changing their reality. Particularly, transformations in accordance with social projects which favor their goals.

Bauxite mining is a major activity in the jarrah (Eucalyptus marginata Donn ex Sm.) forest of south-western Australia. After mining, poor tree growth can occur in some areas. This thesis aimed to determine whether soil constraints, including reduced depth and compaction, were responsible for poor tree growth at low-quality restored bauxite mines. In particular, this study determined the response of jarrah root morphology, leaf-scale physiology and growth/development to soil constraints at two contrasting (low-quality and high-quality) restored bauxite-mine sites. Jarrah root excavations at a low-quality restored site revealed that deep-ripping equipment failed to penetrate the cemented lateritic subsoil, causing coarse roots to be restricted to the top 0.5 m of the soil profile, resulting in fewer and smaller jarrah trees. An adjacent area within the same mine pit (high-quality site) had a kaolinitic clay subsoil, which coarse roots were able to penetrate to the average ripping depth of 1.5 m. Impenetrable subsoil prevented development of taproots at the low-quality site, with trees instead producing multiple lateral and sinker roots. Trees in riplines, made by deep-ripping, at the high-quality site accessed the subsoil via a major taproot, while those on crests developed large lateral and sinker roots. Bauxite mining is a major activity in the jarrah (Eucalyptus marginata Donn ex Sm.) forest of south-western Australia. After mining, poor tree growth can occur in some areas. This thesis aimed to determine whether soil constraints, including reduced depth and compaction, were responsible for poor tree growth at low-quality restored bauxite mines. In particular, this study determined the response of jarrah root morphology, leaf-scale physiology and growth/development to soil constraints at two contrasting (low-quality and high-quality) restored bauxite-mine sites. Jarrah root excavations at a low-quality restored site revealed that deep-ripping equipment failed to penetrate the cemented lateritic subsoil, causing coarse roots to be restricted to the top 0.5 m of the soil profile, resulting in fewer and smaller jarrah trees. An adjacent area within the same mine pit (high-quality site) had a kaolinitic clay subsoil, which coarse roots were able to penetrate to the average ripping depth of 1.5 m. Impenetrable subsoil prevented development of taproots at the low-quality site, with trees instead producing multiple lateral and sinker roots. Trees in riplines, made by deep-ripping, at the high-quality site accessed the subsoil via a major taproot, while those on crests developed large lateral and sinker roots.

Orientador: Rachel Negrão Cavalcanti
Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Geociencias
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Resumo: Intensas atividades de mineração na região de Poços de Caldas se tornaram o objeto de sérias discussões. O alumínio é extraído da bauxita encontrada em áreas próximas à malha urbana. A população está ciente de tais atividades de mineração, entretanto, não há um claro entendimento sobre impactos sociais e ambientais. Questionários cuidadosamente preparados foram submetidos aos representantes da população, aos membros voluntários das ONGs locais e aos governantes pertinentes. Bancos de dados federais foram utilizados para reunir informações sobre áreas locais de concessões de mineração. Resultados georeferenciados indicaram que a população possui uma percepção positiva sobre as atividades de mineração e está ciente da sua importância. Entretanto, o estudo foi capaz de identificar algumas deficiências nas estratégias de comunicação empregadas pelas empresas de mineração. Esta Tese é uma fonte de dados para a percepção da população em relação às atividades de mineração e foi empregada para criar um banco de dados GIS. Em adição, apontou estratégias modernas que podem ajudar a melhorar o relacionamento entre as empresas de mineração e a população local e direcionar outros projetos similares envolvendo variadas atividades de mineração próximas às áreas urbanas
Abstract: Intense mining activities in the region of Poços de Caldas have become the object of serious discussion. Aluminum is extracted from bauxite ore found in areas near urban developments. The population is aware of such mining activities, however, there is no clear understanding regarding social and environmental impacts. Carefully prepared questionnaires were submitted to representatives from the general population, to volunteer members of local NGOs, and government authorities. Available government databases were employed to gather information about local mining concession areas. Georeferenced results indicated that the population perception towards mining activities is positive and the population is aware of its importance. However, the study was able to identify some deficiencies in communication strategies employed by the mining companies. This thesis is a source of data for population perception regarding mining activities and was employed to create a GIS database. In addition, it pointed out modern strategies that can help to improve the relation between mining companies and the local population and guide other similar projects involving diverse mining activities near urban areas
Doutorado
Administração e Politica de Recursos Minerais
Doutor em Ciências