Dans le cadre de cette thèse, une modélisation par éléments finis continue renforcée discrète est développée. Le modèle est basé sur le concept de la cellule élémentaire, avec utilisation de connecteurs pour prendre en compte la rigidité en tension de la structure, et modéliser l'anisotropie du tissu et un élément coque pour décrire la rigidité en cisaillement et gérer le frottement et le contact avec les outils lors de la simulation du procédé de préformage. Les différents éléments de ce maillage spécifique sont générés automatiquement à l'aide des scripts pythons. Associés à ce choix de modélisation, les caractéristiques du comportement sont déterminées à l'aide d'essais expérimentaux conduits sur le renfort et d'une démarche de méthode inverse. Le comportement de ces différents éléments est choisi d'être linéaire élastique en premier lieu, et par la suite à évoluer pour devenir non linéaire. Ces développements numériques sont réalisés dans le logiciel Abaqus/ Explicit. Dans un second temps le modèle développé est utilisé dans le cadre de simulation de l'étape de préformage des renforts secs. A ce titre un démonstrateur expérimental développé dans le cadre de la thèse sert à obtenir des résultats expérimentaux pour corréler ces travaux de simulations. Des comparaisons avec des simulations mono-couche, hémisphérique, permettre de mettre en évidence l'influence des paramètres de simulations mises en jeu. Dans le cadre de préformages de plusieurs plis, l'influence des caractéristiques du contact / frottement est mise en évidence. Finalement une procédure d'automatisation afin de rendre la simulation plus ergonomique dans un contexte industriel est présentée. Cette procédure consiste à générer le maillage spécifique et mettre la simulation en donné dans Catia. Les simulations peuvent ainsi se réaliser sans le passage par Abaqus/CAE. / In this work, a discrete approach for the simulation of the preforming of dry woven reinforcementis proposed. A “unit cell” is built using elastic isotropic shells and axial connectors instead of bars and beams used in previous studies. Shell elements are used to take into account the in-plane shear stiffness and to manage contact phenomenon with the punch and die. Connectors reinforce thestructure in the yarn directions and naturally capture the specific behavior of the fabric. To identify the material parameters, uniaxial tensile tests and bias tests have been employed. A numerical algorithm,coupling Matlab and Abaqus/Explicit, is used to determine the shear parameters by an Inverse method. The model has been implemented in Abaqus to simulate hemispherical stamping.Experimental results are compared to numerical simulations, good agreement between both resultsis shown for the case of single layer forming.This model has been then used to simulate a multilayer performing and a numerical study of the effect of fiction coefficient has been performedFinally a tool which interfaces a CAD Software to the Abaqus/code has been developed.

Reinforced concrete shear walls as seismic force resisting systems may experience inelastic deformations if subjected to strong seismic excitations. These walls are designed to provide strength, stiffness, energy dissipation capacity and lateral drift control for seismic resistance. Shear wall deformability is largely dependent on adequate confinement of core concrete in boundary elements, prevention of longitudinal bar buckling, as well as proper design and detailing of the web section. Conventional transverse reinforcement placed in shear wall boundary elements consists of hoops, overlapping hoops and crossties, based on the geometry and number of longitudinal bars used. The confinement steel requirement of current building codes (ACI 318 or CSA A23.3) often results in congestion of steel cage due to the high transverse reinforcement ratio required. Placing multiple hoops with 135-degree bends combined with crossties to satisfy the code confinement requirements can create concrete placement and construction problems. In addition, the required time to assemble conventional steel cages with multiple individual ties per spacing can be time consuming, potentially impacting the overall cost and duration of construction. Welded Wire Reinforcement (WWR) is available in the construction industry as concrete reinforcement in the form of welded wire fabric (WWF) manufactured from relatively small diameter wires in comparison to the bar sizes typically used in structural applications. As an alternative to using conventional transverse hoops, prefabricated WWR grids can be used to provide required transverse reinforcement in boundary elements. WWR grids are manufactured using robots to weld cut steel pieces accurately before they are shipped to the job site, resulting in better construction quality and reduced construction time. However, research on the use of WWR is limited in the literature. Further experimental and analytical research is needed to establish design requirements for such reinforcement, especially when used in earthquake resistant construction with requirements for ductile response. The current research project, involved three main phases; i) tests of 3 large-scale reinforced concrete shear walls with WWR grids used as boundary element transverse reinforcement, ii) material tests of grid samples, including those cast in concrete, iii) non-linear finite element analysis. The wall tests were conducted under slowly-applied lateral deformation reversals to investigate their strength and ductility for suitability as seismic resistant structural elements. Material tests were conducted to have a better understanding of WWR behavior, especially their weld capacity. Analytical research was undertaken to expand the experimental findings on shear wall behavior, as well as to conduct parametric investigation to understand the impact of changes in grid strength and ductility. The results indicated that WWR grids can be used as boundary element transverse reinforcement in earthquake resistant shear wall. However, strength and ductility of grids should be established carefully prior to such application. Design strength of WWR grids should be established through burst tests to ensure ductile yielding of wire reinforcement prior to premature weld failure. Those grids that exhibit weld failures may be used with reduced design strength to permit the development of sufficient inelastic deformability in flexure-dominant shear walls.

This thesis investigates the technology of twenty-six complete vessels from the ceramic assemblages of K2 and Mapungubwe in the Limpopo Province of South Africa, from the early second millennium (AD 1000 - AD 1300). Mapungubwe is a significant pre-colonial archaeological site of social and political complexity, which lead to the emergence of one of the first known states in southern Africa. Ceramics are commonly associated with these nationally significant sites and have served mainly as chronological and regional markers to determine the cultural sequence of the Shashe Limpopo Confluence Area. Previous studies on these ceramics have paid little consideration to ceramic technology, as research for decades has focused largely on stylistic typologies. Non-invasive methods, compositional materials analysis, and macroscopic analysis provide a broad technological characterization of physical evidence left by the potter on the complete vessels, and are used to interpret aspects of the chaîne opératoire or sequence of ceramic manufacture. Though primary traces of forming and shaping techniques have often been erased by secondary forming processes such as smoothing, scraping, wiping and finishing, the fundamental technology of the vessels can nevertheless be elucidated based on a range of technical variables. This study is the first of its kind in South African archaeology, where complete vessels from a valuable research assemblage are used as a basis for understanding ceramic technology. The results enhance archaeological views of Iron Age ceramic technology, which are pertinent to the interpretation of how the ceramics were manufactured and contributes to a wider understanding of social and technical choices made by potters and related social implications. Vessels from the K2 and Mapungubwe ceramic repertoire serve to answer questions about ceramic research that relate to (a) characterization of complete archaeological ceramics, (b) evidence of technology (c) compositional data of the vessels (d) to provide anatomical data on the technological and morphological attributes of ceramic manufacture. The preliminary results point to evidence of local manufacture of K2 and Mapungubwe ceramics by means of the analysis of four steps in the chaîne opératoire: fabric, forming, firing and finishing. Tentative conclusions further demonstrate technological continuity and variability of raw materials for ceramic manufacture at K2 and Mapungubwe. The broader archaeological perspective, which emerges is one of an expanding technological society, changing technical commonalities, forms and decorative styles, and in the process, making if only subtle technological choices in the manufacture process of early second millennium AD Iron Age ceramics. / Dissertation (MA)--University of Pretoria, 2014. / gm2014 / Anthropology and Archaeology / unrestricted

M.Tech. (Industrial Design) / This study investigated the user’s perspective with reference to the regular use of the WonderbagTM retained-heat cooker in low-income communities in a South African context. This research addresses the limitations of the literature available to support the investigation of the design of a fabric retained-heat cooker from a user’s perspective. As with the WonderbagTM retained-heat cooker, products aimed at underserved low-income communities are often designed without the participation of the end-user. This research focuses on the user’s experience of the fabric retained-heat cooker and seeks to include the user in the process of improving the design of these products. Participatory action research and user-centred design were utilised as the chosen methodologies for this study. The history of retained-heat cookers has been reflected upon when considering the use of insulation materials and alternative fabric improvements. Methods of manufacture, material cost and usage have been considered as critical elements of the design process as well as the skill level of the existing users. Participants indicated their personal interest in the design and development of the prototype retained-heat cooker. They were intensively involved in the design process from the focus group discussion where their perceptions were elicited, right through to their testing of the final prototype. A final workshop concluded the last of three workshops where participants provided individual feedback in terms of their personal experiences of using the prototype retained-heat cooker. Participants were able to selectively customise their prototypes, which brought about a sense of ownership and pride that was not evident in their use of previous retained-heat cookers. Participants indicated personal interest in creating their own retained-heat cookers from the experience that they acquired during the research process. As a result of this experience, the participants believed that they could manufacture their own retained-heat cookers to sell within their community, which could provide income for themselves and other members of their community. The saving of energy in terms of the fuel required to complete the cooking process translated into a direct saving of money, which was highlighted as a recurring theme and identified benefit of retained-heat cooking. By encouraging the use of energy-efficient retained-heat cookers, low-income communities could directly benefit from spending less on fuel costs and more on other essentials.

This thesis examines the programme of mapping produced on silk, and other fabric, by MI9 to facilitate the escape and evasion of British military personnel during World War II. It considers the creation of MI9 in December 1939, the rationale for the new military intelligence branch and the context of the history of military mapping on silk. The map production programme is described, together with its progress and the challenges faced. The various groups of maps are identified and described, together with the source maps on which they were based. This description is developed in nine appendices produced as an integral part of the research to provide a comprehensive carto-bibliography of the 234 individual maps which have been identified. Location details of extant copies in British map collections are also provided. The ingenious methods of smuggling the maps into the camps, with other escape aids, in apparently innocuous leisure items are described. The maps were then copied and reproduced to support the escapes. Coded correspondence with the camps is discussed, and a successful deciphering of some of that correspondence is provided. The implications for the escape and evasion programme were considerable, but so too were the implications of the passage of intelligence from the camps to aid the war effort, a factor apparently largely overlooked in previous studies of the wartime role of the intelligence branches. Three case studies are provided to demonstrate the role and importance of the contribution made by the maps to the escape and evasion programme. The conclusion assesses the significance of this little known episode in British historical cartography of the twentieth century which essentially provides the latest chapter in the story of military mapping on silk, and other fabric, through the ages.

No abstract available / Dissertation (MInt(Prof))--University of Pretoria, 2009. / Architecture / unrestricted

Fabrics are unique materials which consist of various properties affecting their performance and end-uses. A computerized fabric property evaluation and analysis method plays a crucial role not only in textile industry but also in scientific research. An accurate analysis and measurement of fabric property provides a powerful tool for gauging product quality, assuring regulatory compliance and assessing the performance of textile materials. This thesis investigated the solutions for applying computerized methods to evaluate and intelligently interpret the texture and material properties of fabric in an inexpensive and efficient way. Firstly, a method which allows automatic recognition of basic weave pattern and precisely measuring the yarn count is proposed. The yarn crossed-areas are segmented by a spatial domain integral projection approach. Combining fuzzy c-means (FCM) and principal component analysis (PCA) on grey level co-occurrence matrix (GLCM) feature vectors extracted from the segments enables to classify detected segments into two clusters. Based on the analysis on texture orientation features, the yarn crossed-area states are automatically determined. An autocorrelation method is used to find weave repeats and correct detection errors. The method was validated by using computer simulated woven samples and real woven fabric images. The test samples have various yarn counts, appearance, and weave types. All weave patterns of tested fabric samples are successfully recognized and computed yarn counts are consistent to the manual counts. Secondly, we present a methodology for using the high resolution 3D surface data of fabric samples to measure surface roughness in a nondestructive and accurate way. A parameter FDFFT, which is the fractal dimension estimation from 2DFFT of 3D surface scan, is proposed as the indicator of surface roughness. The robustness of FDFFT, which consists of the rotation-invariance and scale-invariance, is validated on a number of computer simulated fractal Brownian images. Secondly, in order to evaluate the usefulness of FDFFT, a novel method of calculating standard roughness parameters from 3D surface scan is introduced. According to the test results, FDFFT has been demonstrated as a fast and reliable parameter for measuring the fabric roughness from 3D surface data. We attempt a neural network model using back propagation algorithm and FDFFT for predicting the standard roughness parameters. The proposed neural network model shows good performance experimentally. Finally, an intelligent approach for the interpretation of fabric objective measurements is proposed using supported vector machine (SVM) techniques. The human expert assessments of fabric samples are used during the training phase in order to adjust the general system into an applicable model. Since the target output of the system is clear, the uncertainty which lies in current subjective fabric evaluation does not affect the performance of proposed model. The support vector machine is one of the best solutions for handling high dimensional data classification. The complexity problem of the fabric property has been optimally dealt with. The generalization ability shown in SVM allows the user to separately implement and design the components. Sufficient cross-validations are performed and demonstrate the performance test of the system.

Aerospace structural components made from polymer matrix composites (PMCs) offer numerous advantages. Their high stiffness and high strength combined with low densities enable lower fuel consumption coupled with higher payloads. As a result, PMCs provide an important economic advantage over typical metallic airframes. Textile reinforcements for PMCs are made by assembling reinforcement fibres, typically carbon. Then, the textile reinforcements are typically cut into smaller pieces, stacked, draped and assembled into a dry assembly called a preform, the shape of which generally approaches that of the PMC part to be made. This manufacturing process is labour intensive and expensive. Novel thick, net-shape, drapable, high vf textile reinforcements used toward manufacturing aerospace PMCs are being developed at the University of Ottawa. The technology enables the manufacturing of flat, drapable multilayered near net-shape preforms. The bending and in-plane shear behaviours of such novel thick reinforcement textiles was investigated to understand and define the behaviour of such thick fabric reinforcements when formed into required shapes. A bending apparatus was developed for investigating the bending behaviour of these novel thick reinforcement fabrics and an articulated frame shear rig was used for investigating the in-plane shear behaviour. A non-destructive inspection method using infrared imaging was used for investigating and identifying flaws and defects in these thick, dry textile reinforcements, aiming at increasing the quality and reproducibility of the final PMC parts made from these reinforcements.

Cette recherche exploite une combinaison de techniques de terrain, paléomagnétiques et de magnétisme des roches pour corréler et localiser la source de plusieurs ignimbrites de deux régions de Turquie qui appartiennent à deux grands systèmes acides : la région du Cappadoce (Anatolie centrale), qui a été précédemment étudiée par plusieurs auteurs, et la région de Afyon-Eskişehir (Anatolie occidentale), jusqu'à présent peu étudiée. L’examen de l’ignimbrite de Kızılkaya (région du Cappadoce), d'âge Miocène supérieur, a consisté en une étude stratigraphique et de magnétisme des roches de l'unité ignimbritique, qui est considérée comme une seule unité d’écoulement et de refroidissement. La magnétisation rémanente, la fabrique magnétique (AMS, AIRM et AARM) et la minéralogie magnétique ont été analysées pour 35 sites de 7 localités situées à des distances différentes de la source supposée par Le Pennec et al. (1998) et à différentes hauteurs stratigraphiques, pour un total de 444 spécimens. La signature magnétique rémanente n’est pas verticalement homogène dans les dépôts. Deux cas sont distingués : (1) une TRM stable, dont la direction est conforme aux données de la littérature précédente (Piper et al., 2002) et (2) deux composantes de magnétisation caractérisées par une température de blocage et des spectres de coercivité se recouvrant. Ces situations ont été enregistrées respectivement en présence d'un Ti-magnétite primaire, et en présence simultanée de Ti-magnétite et de phases magnétiques secondaires (Ti-magnétite altérée et / ou hématite). La fabrique AMS varie verticalement dans le dépôt, en fonction de l'angle entre la direction de la linéation magnétique K1 et du pôle de la foliation magnétique K3, trois types de fabriques ont été caractérisées : normale, oblique et transversale. Après avoir démontré l’origine primaire de la fabrique magnétique, l'AMS a été accentuée par élimination des échantillons caractérisés par des valeurs de densité différentes de plus de ±} 1σ de la valeur moyenne du site. Cette opération s'est traduite par l'élimination des fabriques obliques, qui sont interprétées par la présence locale de fragments de ponces et clastes lithiques dans les échantillons. Les données d'AIRM et AARM indiquent que la Ti-magnétite MD est le principal minéral magnétique porteur de la fabrique, ce que suggère que la fabrique magnétique peut être utilisée pour déterminer les directions d'écoulement. L’examen de la succession ignimbritique d’âge Miocène précoce-Miocène supérieur, exposée sur une zone de ≈14 300 km2 dans la région d'Afyon-Eskişehir, a consisté en une étude stratigraphique-sédimentologique et de magnétisme des roches, afin de localiser la source des ignimbrites en combinant les données du terrain avec les directions de fabrique magnétique. La mesure des sections stratigraphiques, qui ont été réalisées pour 76 localités, conduit aux corrélations stratigraphiques et à la production de cartes d'isopaques et d'isoplètes. La succession ignimbritique est constituée d'au moins trois éruptions majeures distinctes qui ont produit les ignimbrites de Incik, Sabuncu et Seydiler, différentes en âge, distribution, structure et caractéristiques texturales des dépôts. L’étude magnétique consistait en analyses de la minéralogie magnétique et de la fabrique magnétique (AMS et AIRM), qui a été déterminée pour 22 localités sur un total de 36 sites à différentes hauteurs stratigraphiques, soit 600 spécimens. Les données de terrain et les résultats de la fabrique magnétique indiquent deux zones sources. La source des ignimbrites de Incik et Sabuncu est identifiée dans la caldeira de Kırka, une vaste zone de ≈ 20 x 20 km de diamètre, où la présence d'un dôme résurgent a été détectée. La source de l'ignimbrite de Seydiler est identifiée à proximité du village de Bayat. (...) / This research exploits a combination of field, paleomagnetic and rock-magnetic techniques to correlate locate the source and investigate several ignimbrites from two selected regions of Turkey, belonging to two large silicic ignimbrite systems : the well-investigated Cappadocia region (central Anatolia) and the poorly studied Afyon-Eskişehir region (western Anatolia). Investigation of the Upper Miocene Kızılkaya ignimbrite (Cappadocia region) consisted in a stratigraphic rock-magnetic study of the ignimbrite unit, which is considered to be a single flow and cooling unit. Remanent magnetization, magnetic fabric (AMS, AIRM and AARM) and magnetic mineralogy investigations were performed at 35 sites in 7 areal distributed localities at different distance from the vent position inferred by Le Pennec et al. (1998) and different stratigraphic heights, for a total of 444 specimens. Magnetic remanences are not vertically homogenous through the deposits. Two cases are distinguished: (1) a stable TRM, whose direction is consistent with previous literature data (Piper et al., 2002) and (2) two magnetization components with overlapping blocking temperature and coercivity spectra. These situations have been referred respectively to the occurrence of only primary Ti-magnetite, and primary Timagnetite plus secondary magnetic phases (alterated Timagnetite and/or hematite). The AMS fabric varies vertically throughout the deposit; based on the angle between the direction of the magnetic lineation K1 and that of the foliation plunge K3, three types of fabric are evidenced: normal, oblique and transverse. After have attested a primary origin of the magnetic fabric, the AMS was firstly enhanced by discarding all specimens whose density values differ more than +/- 1σ from the site mean value. This resulted in the elimination of the oblique fabrics, which are interpreted as an orientation disturbance due to local occurrence of pumices and lithic clasts in the specimens. Measurement of the AIRM and AARM pointed out that MD Timagnetite is the main carrier of the fabric, which suggests that the magnetic fabric is a reliable proxy for flow directions. Investigation of the Early-Upper Miocene ignimbrite succession exposed in the region of Afyon- Eskişehir consisted in a stratigraphic-sedimentologic and rock-magnetic study of the ignimbrite deposits over a ≈14,300 km2 extended area, in order to locate the source by combining field data and magnetic fabric flow directions. Measurement of the stratigraphic sections, performed at 76 distributed localities, led to ignimbrite correlations and production of isopach and isopleth maps. The ignimbrite succession consists of at least three distinct eruptions that originated the Incik, Sabuncu and Seydiler ignimbrites, different for age, areal distribution, structure and textural features of the deposits. Magnetic investigation consisted in magnetic mineralogy and magnetic fabric analyses (AMS and AIRM), was performed at 22 distributed localities for a total of 36 sites at different stratigraphic heights and 600 specimens. Both field data and magnetic fabric results concur for two source areas. The source area of the Incik and Sabuncu ignimbrites is identified with the Kırka caldera, a ≈20 x 20 km extended area where the presence of a resurgent dome has been detected; source area of the Seydiler ignimbrite is identified in the proximity of the village of Bayat. Volume calculations based on field data pointed out a VEI index of 7 for the Incik and Seydiler ignimbrite, 6 for Sabuncu ignimbrite, evidencing Plinian eruptions; the correspondent magnitude M (Pyle, 2000) is greater than 7 for each ignimbrite.

[EN] The understanding of the mechanical behaviour of natural intact soils is central to engineers when designing new structures. The research carried in this thesis focused on investigating the effects of the naturally occurring in-situ structure on the mechanical behaviour of two shallow recently deposited Holocene alluvial materials, the Bormida River silts (BRS) from Italy and the Valencia silty soils (VSS) from the alluvial plains of the Turia River, Spain. These types of deposits are frequently characterised by highly heterogeneous in-situ structures. A large range of soils with different size distributions from sands to silty clays were investigated. Oedometer and triaxial tests were carried out on intact, slurry and compacted samples. The first step was to characterise the behaviour of the materials at their reconstituted state to define the reference framework for investigating the effect of the in-situ structure of the intact specimens. The effects of the sample preparation technique on the mechanical behaviour were examined, in particular its influence on the uniqueness of the normal compression line and critical state line. The initial structure created during the preparation of the specimens was totally removed after compression and shearing regardless of the sample preparation method. Only one soil displayed a clear effect of the sample preparation technique, the oedometer compression lines of which remained parallel to each other even at a very high stress levels for the case of the slurry samples. This result showed that contrary to what is stated in the literature the sample preparation technique can created very robust initial structures resulting in a transitional behaviour. Clears effects of the in-situ structure of the intact samples of the BRS and VSS were observed on the oedometer compression behaviour even at very high stress levels with stress sensitivity values still larger than unity at the end of the tests. It appeared that the effects were more noticeable as the degree of heterogeneity inside the specimens increased at a meso-structure level as it was the case of some samples of the VSS materials which exhibited a certain layering. Small effects of the in-situ structure were seen at large shearing strains and only on the wet side of the critical state. / [ES] El conocimiento del comportamiento mecánico de los suelos en su estado natural es de importancia capital para los ingenieros a la hora de diseñar nuevas obras. La investigación desarrollada en esta Tesis se centra en descubrir los efectos que tiene la estructura del suelo en su estado natural en la respuesta mecánica de dos suelos aluviales holocenos, depositados superficialmente: los limos del río Bormida (BRS) en Italia y los suelos limosos provenientes de la llanura aluvial del río Turia (VSS) en España. Este tipo de suelos se caracterizan frecuentemente por una estructura inicial altamente heterogénea. Se ha ensayado una gran variedad de muestras con diferentes granulometrías, desde arenas a arcillas limosas en las que se han realizado ensayos edométricos y triaxiales en muestras intactas, compactadas y en muestras reconstituidas (slurry). En una primera etapa de la investigación se caracterizó la respuesta del material en su estado reconstituido para definir un marco de referencia con el que poder comparar la respuesta de las muestras intactas tomadas in situ y que preservan su estructura natural (inalteradas). Se ha analizado la influencia del modo de preparación de las muestras en su comportamiento mecánico, y, en particular, en la unicidad de las curvas de compresión noval y de estado critico. Se ha comprobado que la estructura inicial inducida durante el proceso de preparación desaparece completamente tras someter la muestra a compresión y corte, independientemente del método de preparación utilizado. Únicamente un suelo mostró, de un modo nítido, el efecto de la técnica de preparación, de modo que las líneas de compresión edométrica se mantuvieron paralelas incluso a niveles de tensión elevados en el caso de muestras reconstituidas (slurry). Este resultado demostró, contrariamente a la opinión aceptada en la bibliografía, que el sistema de preparación de la muestra puede crear una potente estructura inicial dando lugar a un comportamiento de tipo transicional. En los ensayos de compresión edométrica se ha podido comprobar un claro efecto positivo de la estructura inicial de las muestras intactas, incluso a niveles altos de tensión, observándose índices de sensitividad tensional superiores a uno al final de los ensayos, de modo que para igualdad de índice de huecos, la tensión efectiva vertical de la muestra intacta es superior a la correspondiente en la muestra reconstituida. Aparentemente, este efecto es tanto más significativo cuanto mayor es el grado de heterogeneidad interno de la muestra a nivel de meso-estructura, como se pudo observar en algunas muestras de los suelos (VSS) que presentaban niveles de laminación horizontal. En los ensayos de corte la influencia de la estructura intacta fue relativamente pequeña y únicamente en el lado húmedo del estado critico. / [CAT] Conèixer el comportament mecànic dels sòls en el seu estat natural és d'importància capital per als enginyers a l'hora de dissenyar noves obres. La investigació desenvolupada en aquesta Tesi se centra a descobrir els efectes de l'estructura del sòl en el seu estat natural en la resposta mecànica de dos sòls al¿luvials holocens, dipositats superficialment: els llims del riu Bormida (BRS) a Itàlia i els sòls llimosos provinents de la plana al¿luvial del riu Túria (VSS) a Espanya. Aquests tipus de sòls es caracteritzen sovint per una estructura inicial altament heterogènia. S'ha assajat una gran varietat de mostres amb diferents granulometries, des d'arenes fins a argiles llimoses amb les quals s'han realitzat assajos edomètrics i triaxials en mostres intactes, compactades i en mostres reconstituïdes (slurry). En una primera etapa de la investigació es va caracteritzar la resposta del material en el seu estat reconstituït per a definir un marc de referència amb el qual poder comparar la resposta de les mostres intactes preses in situ i que preserven la seua estructura natural (inalterades). S'ha analitzat la influència del mètode de preparació de les mostres en el seu comportament mecànic i en particular, en la unicitat de les corbes de compressió noval i d'estat crític. S'ha comprovat que l'estructura inicial induïda al llarg del procés de preparació desapareix completament després de sotmetre la mostra a compressió i tall, independentment del mètode de preparació utilitzat. Únicament un sòl va mostrar clarament l'efecte de la tècnica de preparació, de manera que les línies de compressió edomètrica es van mantenir paral¿leles fins i tot a nivells de tensió elevats en el cas de mostres reconstituïdes (slurry). Aquest resultat va demostrar, contràriament a l'opinió acceptada en la bibliografia, que el sistema de preparació de la mostra pot crear una potent estructura inicial donant lloc a un comportament de tipus transicional. Als assajos de compressió edomètrica s'ha pogut comprovar un clar efecte positiu de l'estructura inicial de les mostres intactes, inclús a nivells alts de tensió, observant-se índexs de sensitivitat tensional superiors a la unitat al final dels assajos, de manera que per a igualtat d'índex de buits, la tensió efectiva vertical de la mostra intacta és superior a la corresponent en la mostra reconstituïda. Aparentment, aquest efecte és més significatiu quant major és el grau d'heterogeneïtat intern de la mostra a nivell de meso-estructura, com es va poder observar en algunes mostres dels sòls (VSS) que presentaven nivells de laminació horitzontal. Als assajos de tall la influència de l'estructura intacta va ser relativament petita i únicament en el costat humit de l'estat crític." / Carrión Carmona, MÁ. (2016). The effects of the structure on the mechanical behaviour of young Holocene alluvial materials from the Bormida River (Italy) and Turia River (Spain) [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/63470 / TESIS