Ce mémoire de thèse est consacré à l'étude expérimentale du comportement hydromécanique d'un lœss naturel non saturé effondrable provenant d'un site proche de la ville de Bapaume (nord de la France) dans une zone où des problèmes de tassement le long de la ligne nord du TGV ont été attribués à l'effondrement du lœss, du fait d'infiltrations d'eau. Un nouvel appareil triaxial permettant de mesurer localement l'ensemble des caractéristiques du loess non saturé (déformation, teneur en eau et succion) a été développé. La courbe de rétention d'eau, déterminée à l'aide d'un tensiomètre de haute capacité et de la méthode du papier filtre a fait l'objet d'une attention particulière : elle présente autour de la teneur naturelle une zone sans hystérésis bordée par deux boucles d'hystérésis des côtés secs et humides. L'analyse de la courbe de rétention et du phénomène d'hystérésis a été approfondie grâce à une étude microstructurale réalisée à l'aide de la porosimétrie au mercure et de la microscopie électronique à balayage. Une structure assez complexe composée d'un arrangement métastable de grains de limon secs (probablement liés par la recristallisation du calcaire) et d'une phase argileuse répartie de façon hétérogène a été mise en évidence. L'étude du comportement hydromécanique a compris une investigation de l'effondrement à partir de faibles valeurs de contraintes proches de la contrainte in-situ, à l'aide d'essais oedométriques à taux de déformation constant avec mesures de succion. Le maximum d'effondrement et une dépendance fonction de la vitesse de chargement ont été identifiés. Une campagne d'essais triaxiaux à différentes teneurs en eau constantes avec mesure de succion a permis de déterminer l'allure de la limite élastique du limon naturel dans un diagramme p/q, ainsi que ses variations avec la teneur en eau et la succion et confirmer l'écrouissage en succion / The hydromechanical behaviour of an unsaturated natural loess from Northern France has been studied. Collapse-on-wetting phenomena under constant external load are observed in the in-situ conditions, related to some stability problems detected on the loess foundations of the high speed train line that links Paris to Brussels. A new triaxial apparatus with complete local monitoring of unsaturated properties (strains, water content and suction) of this loess has been developed. The water retention curve of loess, obtained by using an in-house constructed high capacity tensiometer and the filter paper method, shows a special behaviour, with a non-hysteresis zone detected around the natural hydric state bordered by two hysteresis loops at the dry and wet sides of the curve. Further analysis of the water retention curve and of the hysteresis phenomena were conducted by means of a microstructure study made by mercury intrusion porosimetry and scanning electron microscope observations. The complex structure of loess is highlighted, composed by a metastable arrangement of dry silt grains (possibly related to carbonate re-crystallisation) and a heterogeneously distributed clay fraction. The hydromechanical behaviour study includes the evaluation of the collapse sensibility of loess at stress states close to the in-situ one, by a series of suction-monitored oedometer tests performed at different constant strain rates (CSR tests). A maximum of collapse and a time-dependent behaviour of loess were observed. A triaxial testing programme at different water contents with suction measurement, allowed to obtain the yield surface of loess in a q/p diagram, and the water content and suction evolution upon loading and to confirm the suction hardening in this material

[pt] Apresenta-se, neste trabalho, resultados de um extenso estudo experimental de laboratório, cujos objetivos eram: obter informações do comportamento tensão-deformação em condições não drenadas, e verificar a susceptibilidade à liquefação de um resíduo oriundo da lavra do itabirito silicoso da Mina de Fernandinho, que situa-se no Quadrilátero Ferrífero (Minas Gerais ), região com grande concentração de minério de ferro. Para realizar o estudo de susceptibilidade à liquefação do resíduo, foi necessário projetar e construir um equipamento que é constituído de: uma célual triaxial, servo-motores, válvulas para regulagem de pressão, um microcomputador AT486, conversor D/A, um sistema de aquisição de dados da National Instruments e alguns acessórios que foram desenvolvidos para facilitar a execução dos ensaios. Durante a fase de projeto e montagem deste equipamento foi implementado um programa na linguagem de programação C para gerenciar os ensaios. Este equipamento possibilitou a execução dos ensaios triaxiais cíclicos e monotônicos com trajetórias de tensões servo controladas. Na primeira fase deste estudo foram realizados ensaios de caracterização completa, análise mineralógica e de microscopia eletrônica. Após a caracterização física do material, passou-se ao estudo do comportamento tensão- deformação e resistência com a execução de ensaios triaxiais. Nesta fase foram executados ensaios monotônicos e cíclicos em corpos de prova adensados isotropicamente e anisotropicamente. Com as análises dos resultados e entendimento do comportamento tensão deformação deste material em condições de laboratório, concluiu-se que este é susceptível à liquefação devido ao comportamento colapsível e desenvolvimento elevado de poropressões. Finalmente, propõe-se uma nova metodologia experimental para estudar os mecanismos que levam o solo a desenvolver o fenômeno de liquefação, tendo em vista que as metodologias apresentadas na literatura corrente não são adequadas para estudar este fenômeno. / [en] This work presents results of na experimental research programme executed in the laboratory at PUC-Rio, Brazil. The aim of this research was investigated the stress-strain behaviour and the evaluation of the susceptibility of fine grained tailing material from Fernandinho Mine to liquefaction. This mine is at Quadrilatero Ferrífero (Minas Gerais - Brazil), region with one of the largest sources of iron ore in Brazil.In order to study the susceptibility to liquefaction of tailing material an servocontrolled triaxial device was developed. This device were composed by: triaxial cell, servo-motors,pressure regulators, microcomputer, one digital analogy convert of, one analogy digital convert developed in the laboratory at PUC-Rio and other accessories. During the development of the device, one software to control all the trajetories was implemented. Using this device some cyclic and monotonic triaxial tests were carried out.Complete characterization, mineralogical and eletronic microscope analysis were carried out in the preliminary steps of this research. After this, an extensive programme of triaxial tests were carried out in order to determine the failure envelope, stress-strain behaviour and liquifiction resitance of the tailing material.A colapsive behavior of the tested material was observed at small strain and stress conditions. Another important observation was the high level of poropressure development,suggesting that this material is susceptible to liquefaction in special conditions.Finally, based on the test results, a new methodology is proposed to investigate soils when submitted to undrained conditions.

[pt] O aumento da poropressão é um dos mais significativos fatores desencadeantes da ruptura de taludes em muitas regiões do mundo, principalmente em climas tropicais, onde os solos residuais e coluvionares são abundantes. A fim de compreender e analisar o mecanismo e as condições que conduzem a tais rupturas, nesta tese se apresenta um estudo do comportamento de solos submetidos a ensaios triaxiais de aumento de poropressão, que simulam a elevação do nível piezométrico em encostas. Os ensaios foram realizados em amostras indeformadas de dois solos coluvionares e um solo residual jovem, obtidos de diferentes encostas no Rio de Janeiro. Adicionalmente, foram realizados ensaios de cisalhamento direto com plano cortado e superfície polida, e ensaios triaxiais convencionais drenados e não drenados, com a finalidade de obter a resistência residual e a linha de estado crítico dos solos, bem como ilustrar as diferenças de comportamento sob diferentes trajetórias de tensão. Para monitorar as deformações locais das amostras e obter uma medida apropriada das poropressões foram utilizados instrumentos eletrônicos de medição interna e um minitransdutor de pressão na meia altura dos corpos de prova. Os resultados mostraram que sob o efeito de poropressão cada solo apresentou um comportamento distinto, o que se atribui principalmente ao grau de intemperismo e às suas diferentes características estruturais. Observou-se, ainda, que as trajetórias de tensão seguidas nos ensaios têm uma influência significativa nas características de resistência a grandes deformações dos solos. / [en] Pore-pressure increase is one of the most significant triggering factors for slope failures in many regions around the world, mainly in tropical climates, where residual and colluvium soils are abundant. In order to analyze and understand the mechanisms and conditions leading to such failures, this thesis presents a study of the soils behavior under triaxial tests of pore-pressure increase, that mimic the elevation of piezometric level in slopes. The tests were performed on soil samples of two colluvial and one young residual soils from different slopes in Rio de Janeiro. Additionally, direct shear tests with cut plane and polished surface, and conventional undrained and drained triaxial testing were carried out to obtain the residual shear strength and the critical state line of soils, and illustrate the behavior differences under different stress paths. Internal instrumentation and a miniature pore-pressure transducer at the mid-height of the specimens were used to monitoring local deformations of the specimens and get appropriate porepressure measures. The results showed that under the effect of pore-pressure increase each soil showed different behavior. It is attributed mainly to the degree of weathering and their differing structural features. It was also observed that the stress path followed in the tests have a significant influence on the strength characteristics of the large strain state of soils.

<p dir="ltr">Biorefineries rely on compression feed screws to transport biomass for biofuel production in chemical reactors. However, flowability issues within these feedscrews often lead to production downtime, impacting profitability. Modeling biomass flow within the feedscrews is crucial to optimize processing parameters like torque and speed, reducing downtime. Biomass is a non-uniform granular material which faces flowability issues. The problems in flowability is influenced by factors such as particle size, moisture content, material composition, and processing methods. Identifying key parameters that can influence the material behavior is vital to minimize production downtimes. Feedscrews operate under high pressures which makes obtaining accurate material parameters at these high pressures challenging. Many methods used within the pharmaceutical industry to obtain material parameters are unable to reach the larger pressures that the material experiences within the feedscrew. However, Triaxial testing can be used to test the material at the high pressure of interest. Triaxial testing has been used within the civil engineering field to test granular materials such as soils, sand, and rocks. The Finite Element Method (FEM) using a continuum model is used for modeling systems with a large number of particles. The modified Drucker-Prager Cap (mDPC) continuum model is often used to capture complex material behavior, including densification and shear yielding in granular materials. This model seems well suited to capture the behaviors of biomass material. The focus of the thesis is to obtain the shear failure properties of corn stover using triaxial testing and the Drucker-Prager Cap continuum model. Simulations and experimental data are utilized to establish a criterion for identifying shear failure. While simulations depict ideal behavior of a DPC material with frictionless and frictional platens, experimental data shows trends of real-life corn stover. Simulation results effectively predict the material’s friction angle but show larger errors in estimating cohesion, potentially due to extrapolation or cohesion’s sensitivity to volumetric plastic strain. Further simulations at smaller hydrostatic unloading pressures are recommended to reduce this error. Experimental trends for shear failure seem to align with simulation trends for shear failure identification. However, the densification trends in experiments lack the clarity observed in the trends from the simulations. More triaxial experiments should be run to determine if the trends are consistent at other hydrostatic loading and unloading pressures. More than two experiments at the same hydrostatic loading pressure should also be run to estimate the shear failure line to obtain a better estimation. Experimentally there are a number of other factors that could contribute to errors such as the estimated material diameter used to calculate Mises stress, if corrections were made for items such as the moving piston, latex membrane, and more, and how far the shear failure line is extrapolated to the vertical axis.</p>

Les résidus miniers épaissis représentent une alternative de plus en plus utilisée pour le stockage de surface. Cette technologie, développée au Canada, possède plusieurs avantages par rapport aux résidus miniers conventionnels, qui contiennent typiquement plus d’eau. Ceci permet de réduire la consommation d’eau de la mine, en plus d’améliorer les propriétés mécaniques du matériau, et de réduire l’empreinte des parcs à résidus. Néanmoins, bien que ces avantages soient tous théoriquement vrais, des efforts en recherche expérimentale sont encore nécessaires afin de valider ces affirmations. Ce projet s’inscrit dans cette ligne, et se veut une étude de laboratoire du comportement en cisaillement des résidus miniers épaissis. Le contexte théorique de la résistance au cisaillement statique est tout d’abord abordé pour ce type de matériau. L’essai triaxial et la mesure des vitesses des ondes de cisaillement (V[indice inférieur s]) sont abordés en détails, puisque des liens sont effectués entre les résultats de ces deux essais. Certains modèles de comportement en cisaillement, comme le modèle hyperbolique de Duncan et Chang, sont abordés afin de pouvoir être utilisés comme outils d’analyse. Le phénomène de la liquéfaction statique est également abordé dans le cadre du comportement volumétrique lors du cisaillement. Les positions des écoles de Harvard et de Cambridge sur ce sujet sont résumées et comparées, dans le but d’élaborer un cadre d’analyse clair pour ce projet. Au niveau expérimental, plusieurs essais triaxiaux ont été effectués afin d’évaluer la résistance au cisaillement statique d’un résidu provenant d’une mine d’or canadienne. Des essais en conditions drainées et non-drainées sont effectués et comparés aux résultats provenant d’un autre laboratoire. Cette comparaison a pour but de valider le bon fonctionnement de l’appareil triaxial ELDYN, de marque GDS, utilisé dans le cadre de ce projet. En effet, cet appareil est neuf, et une étape de prise en main et de calibration est nécessaire. Par ailleurs, une méthode de mise en place des échantillons triaxiaux par déposition hydraulique a été élaborée afin de mieux reproduire l’état des résidus sur le terrain. Des essais triaxiaux ont été effectués afin d’évaluer l’impact de la méthode de mise en place sur la résistance au cisaillement et certains autres facteurs. Des mesures de vitesses des ondes de cisaillement sont également effectuées pour 2 raisons. Tout d’abord, la technique de mesure par anneaux piézoélectriques, développée à l’Université de Sherbrooke, n’a jamais été appliquée sur ce type de matériau. Par ailleurs, des modules de cisaillement provenant des essais triaxiaux et des mesures de V[indice inférieur s] sont comparés, afin d’établir un lien entre le domaine des petites et des grandes déformations. Lors de mesures de V[indice inférieur s] sur le terrain, ce type de relation pourrait éventuellement permettre d’obtenir des paramètres de résistance au cisaillement à grandes déformations (φ’, c’) à partir de mesures in situ non-destructives, effectuées à très petites déformations.

ITC/USA 2007 Conference Proceedings / The Forty-Third Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2007 / Riviera Hotel & Convention Center, Las Vegas, Nevada / The Endevco model 7270A high-g accelerometer has been used successfully in numerous flight tests at the U.S. Army Research Laboratory. The accelerometer is available in ranges as low as 6,000 g’s up to 200,000 g’s so they can be used in a variety of situations to measure setback, set forward and balloting in artillery rounds, mortars and tank projectiles to name a few. However, one of the disadvantages of the model 7270A is its physical size, in the era of die level and surface mount components, the 7270A is relatively large. The sensing element is packaged inside a metal case with screw holes for mounting to a rigid surface. In addition, there are wires protruding from the case for electrical connections. In the area of munitions, small cavities don’t always afford the room for a large gauge. It was desirable to repackage the die in a smaller container and make it a surface mount component for a printed circuit board. A contract was developed for Endevco to repackage the die and to develop a tri-axial version with the repackaged die. The newly developed accelerometers were tested and evaluated by the U.S. Army Research Laboratory.

Une analyse expérimentale approfondie avec une approche micro macro a été réalisée sur un matériaucomposé d'un mélange d'argile Kaolinite/Smectite. L'étude a permis de montrer à l'échelle macroscopiquecomme à l'échelle microscopique un comportement particulièrement sensible à la proportion de smectitedans le mélange. La kaolinite (Kaolinite P300) est bien connue du point de vu de sa caractérisation et deson comportement, la smectite (également nommée argile grecque) est de type calcique et a égalementfait l'objet de plusieurs études.Dès 35% de smectite dans le mélange, les résultats sur chemin triaxial montrent que le comportementapproche considérablement celui de la smectite. Par ailleurs, l'investigation à l'échelle microscopique (aumoyen de Microscope Electronique à Balayage complétée par une analyse de diffractions des rayons X)réalisé sur les échantillons après l'essai, met en évidence le fait que, lorsqu'elle dépasse un certain seuil, lafraction en smectite favorise le développement de plans de glissement. Ces plans apparaissent clairementsous forme de groupes de particules de smectite orientées.L'analyse microstructurale utilisée est basée sur une méthode rigoureuse, développée dans le cadre decette thèse, avec un traitement d'images automatisé permettant de fournir des résultats quantitatifs.Cette démarche d'investigation multi‐échelles a été employée afin caractériser le comportement d'unsédiment marin prélevé au large de Golfe de Guinée par 700 m de profondeur d'eau. L'étude, initialementmenée dans le cadre du projet CLAROM (2002‐2005), intéresse l'industrie Offshore. Le sédiment naturelcontient jusqu'à 60% de proportion argileuse avec approximativement 15% de smectite et 50% dekaolinite.

Este trabalho faz parte de uma pesquisa voltada ao estudo do comportamento mecânico do sistema ferroviário e tem foco principal no estudo experimental em laboratório que visa avaliar as características do lastro ferroviário em condições de carga variadas e determinar a influência dos principais parâmetros que afetam o comportamento da estrutura. O material utilizado em camada de lastro ferroviário é normalmente constituído de frações granulométricas graúdas o que dificulta a execução de testes de grande escala em laboratório, devido à robustez necessária do equipamento para representar a correta correspondência entre a amostra e o material de lastro. O principal objetivo deste trabalho foi avaliar a eficiência de um novo aparelho triaxial em larga escala (400mmx800mm), que permite ensaiar agregados graúdos como no campo sem a necessidade de escalonamento da curva granulométrica; analisar a aplicabilidade da técnica de graduação paralela em ensaios triaxiais utilizando equipamento cilíndrico de pequena escala (150mm x 300mm), no qual é mais fácil de manipular pequenas frações, assim como avaliar a influência de duas graduações diferentes sobre deterioração e deformação. Verificou-se que os materiais granulares revelam uma forte tendência de se compactar sob níveis elevados de estresse, causando um aumento significativo de rigidez. A graduação AREMA Nº 24 mostrou-se mais resistente à deformação e a deterioração quando comparada à AREMA Nº 3. O nível de tensões escolhido mostrou-se satisfatório para simular a via permanente sob carregamento, devido à deterioração dos agregados ao final do teste. Além disso, a degradação da amostra contaminada foi mais acentuada que aquela sem finos, demonstrando que o aumento no nível de colmatação implica em perda da durabilidade do lastro, acarretando em necessidade de mais ciclos de correção geométrica e diminuição de sua vida útil. Observou-se que combinação de finos e água no lastro afeta fortemente a resposta mecânica da via permanente, diminuindo sua rigidez e ocasionando instabilidade do sistema, devendo esta situação ser evitada. Os resultados também apontam que o aumento de carga por eixo contribui para uma degradação acelerada dos componentes da via, ocasionando a diminuição do período entre ciclos de manutenção. Os resultados contribuem para uma melhor compreensão do comportamento mecânico da camada de lastro, e desta forma auxiliam no projeto de vias férreas mais eficientes. / This work is part of a research focused on studying the mechanical behavior of the railroad system and has a primary focus on experimental laboratory work aimed to evaluate the characteristics of railway ballast under conditions of varying load and determines the influence of the main parameters that affect the behavior of the structure. Materials used in ballast layers are usually comprised of a highly coarse-graded gradation, hence the implementation of large-scale laboratory tests is difficult to conduct due to the corresponding large-scale triaxial specimens for railroad ballast material. The main purpose of this paper was to evaluate the efficiency of a new large-scale triaxial apparatus (400mm x 800mm), that allows testing large-size particles as found in the field without the need of scaling aggregates; the applicability of the parallel gradation technique in triaxial tests using small-scale cylindrical equipment (150mm x 300mm), in which it is easier to manipulate small fractions, as well as to assess the influence of two different gradations on ballast breakage and deformation. It was found that granular materials reveal a strong tendency to settle under higher stress levels, causing a significant increase of their strength and stiffness. The AREMA No. 24 gradation was found to be the most resistant to ballast settlement compared to AREMA No. 3. The stress level chosen was satisfactory to simulate the permanent way under load, due to deterioration of the aggregates at the end of the test. Moreover, the degradation of the contaminated sample was more pronounced than the one without fouling, demonstrating that increased level of fouling implies loss ballast durability, resulting in the need for more rounds of geometric correction and reduction of the life cycle. It was observed the combination of fines and water in the ballast strongly affects the mechanical response of the track, reducing its stiffness and causing system instability, and this situation must be avoided. The results also indicate that increasing axle load contributes to accelerated deterioration of track components, causing a decrease in the period between maintenance cycles. The results contribute to a better understanding of the mechanical behaviour of ballast layer, and thereby assist in the design of more efficient railways.

Liquefaction of soil is one of the major contributing factors for damages of infrastructures and utility services during earthquake. Liquefaction occurs when short strong shaking creates undrained loading condition in saturated soil deposit thereby increases pore water pressure, which eventually equals the effective confining pressure resulting in significant reduction in shear strength and bearing capacity of soil deposit. Several studies have been conducted to investigate the effect of polypropylene fiber on sand deposit as a measure to prevent liquefaction but most of them are based on static tests. Therefore, the present study, tries to understand liquefaction characteristics of sand reinforced with polypropylene fiber based on cyclic triaxial test. The main objectives of this study are (i) to explore the effect of polypropylene fiber on pore pressure generation and deformation characteristics of sand, and (ii) to observe the effect of confining pressure on liquefaction characteristics of sand-fiber mixture. A series of stress controlled cyclic triaxial tests were performed at 5 and 10 psi effective confining pressures. At 5 psi effective confining pressure, specimens of clean sand, and sand containing 0.05, 0.075, 0.1, and 0.3% polypropylene fiber by dry weight were tested at 0.2, 0.25, 0.3, and 0.4 Cyclic Stress Ratio (CSR). However, at 10 psi effective confining pressure, specimens were also tested for 0.5%, and 0.75% fiber in addition to those at 5 psi confining pressure at 0.2, 0.3, and 0.4 CSR. Based on the test results, it was observed that, cyclic shear stress increases with the increase in initial effective confining pressure. Also, for a given CSR, liquefaction resistance decreased with the increase in effective confining pressure. Furthermore, significant improvement in liquefaction resistance was observed when the fiber content exceeded beyond 0.075% at 5 psi confining stress. However, at 10 psi confining pressure, addition of fiber did not help in improvement of liquefaction resistance of sand except when cyclic shear stress was applied at 0.2 CSR. At 0.2 CSR, although the specimens did liquefy based on pore pressure generation criteria at all fiber contents, specimens containing 0.5% and 0.75% fiber did not ever reach 2.5% and 5% DA (Double Amplitude) deformation throughout 1000 loading cycles.

The use of plastic concrete for cutoff walls in dams for remediation of seepage issues has become more widely used in the past 25 years, however, the in-situ material properties are still not well understood. The research presents a new testing procedure that combines two existing testing methods, triaxial shear and permeability testing. By developing this laboratory testing method, material properties of the cutoff wall backfill material can be more accurately examined and explained using changes in the permeability of the material to discern the ductility and stiffness.