Thesis (M.Sc.(Wildlife Management)--University of Pretoria, 2000. / Summary in Afrikaans. Includes bibliographical references.

Th. univ.--Mécanique des solides et des structures--Paris 6, 1995. / Bibliogr. p. 149-155. Résumé.

D’une part, face à un contexte de manque de gisements et d’épuisement des ressources naturelles en matière d’agrégats et, d’autre part, en présence d’un matériau marin abondant issu des opérations de dragage, l’idée émergeante est de valoriser ces déchets dans une matrice cimentaire pour deux applications : béton de sable normalisé et granulats. Notre intérêt est de proposer une alternative aux bétons usuels pour certaines applications. L’étude de formulation est une tâche complexe et la nature des matériaux de base l’accentue davantage. L’étude consiste à proposer une nouvelle méthode de formulation du béton de sable normalisé. Vu l’étendue granulaire, l’incorporation d’un filler s’avère judicieuse et indispensable à la fois pour des raisons techniques et économiques. A travers la phase de caractérisations de notre béton de sable, plusieurs protocoles d’essais ont été mis en place afin de mettre en évidence les qualités de ce matériau et de promouvoir son usage courant. Pour décrire le comportement du béton de sable, il a été procédé à sa caractérisation vis-à-vis de plusieurs phénomènes à savoir : résistance en compression, résistance en traction, module d’élasticité statique et dynamique, consistance, hydratation aux jeunes âges, cinétique de retrait par dessiccation, microstructure et quantification des différentes formes d’eau dans la matrice cimentaire. D’une manière analogique, une nouvelle méthodologie de formulations des granulats à base de mêmes matériaux que le béton de sable a été étudiée. Les granulats testés ont été fabriqués par extrusion. Les résultats de caractérisations des bétons de sable et des granulats sont très prometteurs. / On the one hand, against a backdrop of deposits lack and depletion of natural resources in terms of aggregates and, on the second hand, in the presence of abundant marine material from dredging operations, the emerging idea is to recover these wastes in a cement matrix for two applications: standard sand concrete and aggregates. From this perspective, our interest is to propose an alternative to conventional concrete for some applications. The formulation study is a complex task and the nature of the basic materials accentuates it further. The study consists to propose a new formulation method of standard sand concrete. Given the extensive granular, the incorporation of a filler is judicious and essential both for technical reasons such as improving the compactness and economic such as reducing the cement mixture. Through the characterization phase of our sand concrete, several test protocols have been established to highlight the qualities of this material and promote its current use. To describe the behavior of our concrete sand, we carried out characterization towards several phenomena that is: compressive strength, tensile strength, static and dynamic elasticity modulus, consistency, hydration at early ages, shrinkage on drying kinetics, microstructure and quantification of different forms of water in the cement matrix. In a similar manner, we proposed a methodology formulation of aggregates based on the same materials as concrete sand. The aggregates tested were manufactured by extrusion. The results of characterizations of concrete and aggregates sand are very promising.

Thèse doctorat : Génie Civil : Villeurbanne, INSA : 2004. / Titre provenant de l'écran-titre. Bibliogr. p. 295-306.

Thèse doctorat : Génie Civil : Villeurbanne, INSA : 2003. / Titre provenant de l'écran-titre. Bibliogr. p. 325-332.

Th. doct.--Hydrol. et hydrogéol. quantitatives--Paris--Éc. natl. sup. des mines, 1996. / Bibliogr. p. 169-175. Résumé en français et en anglais.

Cette thèse de doctorat porte sur la modélisation numérique du comportement des sables à l'aide de la loi de comportement NorSand-aUL. Cette loi, développée dans le cadre de ce projet de recherche, est une évolution du modèle NorSand spécifiquement adaptée à la modélisation du comportement des sables soumis à des sollicitations cycliques. La révision des performances de NorSand sous différents types de sollicitations (triaxial compression, cisaillement simple statique et cyclique, cisaillement à direction et ratio des contraintes principales contrôlés) a permis l'identification de certains points faibles du modèle, rendant ses modélisations du comportement des sables sous sollicitations cycliques insatisfaisantes. Afin de corriger ces lacunes, deux groupes de modifications ont été proposés. D'abord, la théorie de l'état critique anisotrope a été implémentée dans NorSand, afin d'y créer une dépendance vis-à-vis du type et de la direction des chargements. Cette modification a grandement amélioré les performances du modèle pour la modélisation du comportement encisaillement simple statique. La deuxième modification proposée s'est articulée autour de la formulation d'une nouvelle mécanique de génération de la plasticité lors du déchargement des sables. L'existence d'une deuxième surface de plasticité, nichée à l'intérieur de la surface de plasticité originale de NorSand, a été postulée. Les capacités de modélisation d'une version de NorSand incorporant cette nouvelle mécanique ont été confirmées grâce à la modélisation d'essais triaxiaux drainés et non drainés comprenant des phases de déchargement. Les deux modifications proposées au modèle NorSand au cours de ce projet de recherche ont finalement été agrégées pour mener à la formulation de NorSand-aUL. Ce nouveau modèle a été utilisé pour la modélisation d'essais de cisaillement simple cyclique effectués sur deux sables. Ces modélisations ont démontré les gains réalisés, particulièrement pour les essais effectués sur sable lâche, par rapport aux performances antérieurement obtenues à l'aide de la version originale de NorSand. Des axes de recherche future ont été proposés afin d'améliorer les performances de NorSand-aUL, notamment pour la modélisation du comportement des sables denses soumis à des sollicitations cycliques. / This PhD thesis deals with the numerical modelling of sand behaviour using the NorSandaUL constitutive law. This law, developed as part of this research project, is an evolution ofthe NorSand model specifically adapted to the modelling of sand behaviour under cyclicloading. The review of NorSand's performance under various types of loading (triaxial compression, static and cyclic simple shear, fixed principal stress direction and fixed principal stress ratio) has allowed the identification of certain weak points in the model, making its behaviour modellings under cyclic loading unsatisfactory. In order to address these short comings, two groups of modifications were proposed. First, the anisotropic criticalstate theory was implemented in NorSand, in order to create a dependency on the type and direction of loading. This modification greatly improved the performance of the model for predicting static simple shear behavior. The second proposed modification focused on the formulation of a new mechanics for the generation of plasticity during unloading. The existence of a second yield surface, nested within the original NorSand yield surface, was postulated. The modelling capabilities of a version of NorSand incorporating this new mechanics were confirmed by satisfactory modelling results of drained and undrained triaxialtests which included unloading phases. The two modifications to NorSand proposed over the course this research project were eventually aggregated to lead to the formulation of NorSand-aUL. This new model was used to model cyclic simple shear tests for two sands. These modelling results demonstrated the gains made, particularly for tests conducted on loose sands, compared to the performance previously obtained using the original version of NorSand. Areas for future research were proposed to improve the performance of NorSandaUL, particularly in modelling the behaviour of dense sands under cyclic loading.

Thèse doctorat : Génie Civil : Villeurbanne, INSA : 2004. / Titre provenant de l'écran-titre. Bibliogr., 8 p.

Thèse doctorat : Génie Civil. Mécanique des sols : Villeurbanne, INSA : 2008. / Titre provenant de l'écran-titre. Bibliogr. p. 263-274.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg in fulfillment of the requirements for the degree of Masters in Science. Johannesburg, August 2016. / Resource selection by herbivores is driven by processes operating across a multitude of spatial scales and is influenced by a variety of biotic and abiotic environmental conditions and resources across the landscape. Spatial scales levels are crucial in habitat selection studies because they affect the interpretation of results and what may appear important at one level may not be relevant at another. Decisions made by animals at these levels can influence animal movements and hence the spatial distribution of populations. In this way, the use of resources across different scales by individual and groups of animals can be linked to population performance as a whole. Within home ranges, habitat use is mostly influenced by variation of food resources and water availability together with competition and predation risk. The study aimed to determine sable home range extent and habitat use and to test how predation, competition and other environmental factors influenced the selection of areas within these home ranges, in the thriving sable population of the Gorongosa National Park (GNP), Mozambique. Two adult females, one per herd, were fitted with GPS collar providing 5 hours interval GPS coordinates over a year, which were used to determine the annual and seasonal home ranges extents. Home ranges were then overlaid with vegetation map to analyse habitat use. Contrary to expectation, sable home ranges in this study were larger than those found in previous studies. The herds did not limit their habitat use to woodlands, using also open grasslands, drainage lines and bottomlands that retained green grasses during the dry season. Both herds expanded their ranges during the dry season, searching for those areas that still retained green grasses and searching for remaining water sources. For the resources selection within home ranges, I used the same GPS collar coordinates to fit seasonal logistic regression models with biotic factors (predation risk and competition) and with environmental variables (distance from water, distance from roads, elevation, slope, NDVI, vegetation types and landscape). Results show that sable were less prevalent in areas with high predation risk, but herds differed in prevalence with competitors, one herd favouring areas with high reedbuck concentrations and the other favouring low concentrations. Effects of environmental variables were different between seasons and between herds, being distance from water, distance from roads, greenness and elevation the most influential environmental. Both herds, however, avoided low elevation areas during the wet season, probably in order to avoid areas flooded during this period. As conclusion, predation risk and competition influenced selection within home ranges by sable in the GNP, despite low densities of potential competitors and lions. Nevertheless, this influence seems to not be enough yet to limit the success of the population. The herds also showed evidences of being affected by dry season, as demonstrated by the home ranges expansions during this period. With increase of herbivores population other that sable, and consequently increase competition and decrease of availability of resources, this could lead to reduction of growths percentages of the sable population in the park in the future. / MT2018