Triaxial shear test is the most accurate test for deciding the undrained shear strength of clay. In every test the ratio between the horizontal and vertical stresses, the coefficient of earth pressure at rest (K0′), has to be decided. It’s widely believed that the choice of this parameter will influence the results, but it’s not known to what extent. In this thesis 20 consolidated undrained active triaxial shear tests on clay has been con- ducted with a K0′ at 0.6 and 0.8. The clay was collected with a 54 mm piston sampler at the Norwegian Geo-Test Site in Trondheim, Norway, on depth of 3.0 to 7.8 meters. Besides the triaxial testing, index tests and oedometer tests was conducted on every cylinder to do a gen- eral classification of the clay. The clay has a sensitivity of 9-20, a water content of 35-51 %, a plasticity index of 27-65 % and an over consolidation ratio of 2.6-6.8. The consolidation phase of the triaxial test was conducted in five loading steps with a rest time in-between to monitor the amount of pore water expelled at each stress level. The loading steps was 50 %, 75 % and 100 % of maximum cell pressure and thereafter at 50 % and 100 % of the maximum deviator stress. The shear phase was done at a speed of 1.5 % per hour to a total of 10 % axial strain. It is not possible to reach an unambiguous conclusion from the results, but the maximum shear strength of tests with a K0′ at 0.8 is 17 % higher, while the total amount of pore water extortion is equal between the two values. The amount of creep in the latest steps is on the other hand smaller for a K0′ at 0.8. This indicates that the soil is handling the stress level better than with a K0′ at 0.6.

Predicting tire performance on soft, fine-grained soils is required for many off-road explorations in the military, mining, agricultural, and earth-moving sectors. However, the mobility in deformable material is extremely challenging, especially in the presence of water. Although there is a significant amount of research on terrains such as sands, there is a lack of research on fine-grained soils. This research is part of a bigger project that presents a novel approach to improve the mobility of off-road vehicles on wet deformable soils. The approach integrates experimental data from small-scale soil testing, large-scale soil-tire interaction testing, and advanced physics-based numerical simulation techniques. In particular, this thesis attempts to characterize the clay-tire interface by conducting large-scale direct shear tests. In addition to clay-tire contact friction, the properties and strength parameters of the soft clay are determined by conducting various index properties and advanced tests. The testing program accounts for different stresses, loading conditions, and boundary conditions, decided taking into account real field conditions. The results from all these experiments will be used to calibrate and validate the material constitutive models required for the development of a mobility predictive numerical model. Overall, this study contributes to the development of more advanced and accurate terramechanics models that involve deformable terrains like soft clays. / Master of Science / The prediction of Vehicle mobility on soft, fine-grained soils is challenging due to the impact of soil behavior on mobility, which is not taken into account by traditional vehicle simulation software. However, as off-road exploration and resource extraction become increasingly important, particularly in military, agricultural, and earth-moving sectors, the study of vehicle mobility on deformable soils is inevitable. The difficulty in predicting tire performance on soft, fine-grained soils is due to the lack of proper experimental data and numerical modeling techniques that accurately characterize the interaction between soil and vehicle tires, known as "terramechanics." The study forms a constituent part of a broader project, which aims to integrate the experimental research data from small-scale soil testing, large-scale soil-tire interaction testing, and advanced physics-based numerical simulation techniques. The main contribution of this study is to investigate soil-tire interaction to determine the contact friction between the soil and tire by conducting large-scale direct shear tests. It also involves conducting basic index properties tests and advanced shear strength and compression tests. The results from all these tests contribute to developing more accurate soil-tire interaction models in terramechanics. Given the scarcity of research on large deformable terrains like soft clays, this study can make a significant contribution towards developing more advanced and accurate terramechanics models that involve deformable terrain, which can be useful in various applications.

No description available.

Bridge bents (deep beams) in the State of Texas have experienced diagonal cracking problems with increasing frequency. These field related issues, taken in combination with discrepancies that exist between design provisions for strut and tie modeling (STM), were the impetus for the funding of the current project. The overall objective of the project was to develop safe and consistent design guidelines in regard to both the strength and serviceability of deep beams. In order to accomplish this research objective and related tasks, a database of 868 deep beam tests was assembled from previous research. Inadvertently, many of the beams in this database were considerably smaller, did not contain sufficient information, or contained very little shear reinforcement. As a result, filtering criteria were used to remove 724 tests from the database. The criteria were chosen to consider only beams that represent bent caps designed in the field. In addition to the 144 tests that remained in the database, 34 tests were conducted as part of the current experimental program resulting in 178 total tests available for evaluation purposes. Two additional tests were conducted on beams without shear reinforcement, thus they did not meet the filtering criteria. However, the results from these tests provided valuable information regarding deep beam behavior. Beams that were fabricated and tested as part of the current experimental program ranged in size from, 36"x48", 21"x75", 21"x42", and 21"x23". These tests represent some of the largest deep beam shear tests ever conducted. STM details that were investigated included: (i) the influence that triaxial confinement of the load or support plate has on strength and serviceability performance; and (ii) the influence that multiple stirrup legs distributed across the web has on strength and serviceability performance. Based on the findings of the experimental and analytical program, a new strut-and-tie modeling procedure was proposed for the design of deep beam regions. The procedure is based on an explicitly defined single-panel truss model with non-hydrostatic nodes. An important aspect of the new STM design methodology is that it was comprehensively derived based on all the stress checks that constitute an STM design. Thus, the new method considers every facet of a STM design. The newly proposed STM procedure is simple, more accurate, and more conservative in comparison with the ACI 318-08 and AASHTO LRFD (2008) STM design provisions. As such, the implementation of the new design provisions into ACI 318 and AASHTO LRFD is recommended. / text

Development of shear databases attracted a great deal of attention in the shear research community within the last decade. Although a few shear databases have already been developed by several research groups, there is no comprehensive shear database that is focused on prestressed concrete members. This thesis aims to develop a shear database for prestressed concrete members with an intensive literature review. This literature review resulted in a database that contained a total of 1,696 tests reported in North America, Japan, and Europe from 1954 to 2010. The database was used to evaluate shear design provisions available in North America, Japan, and Europe. The variations in measured versus calculated shear strength using twelve shear design equations were analyzed. The analysis results indicated that design expressions based on the Modified Compression Filed Theory (MCFT) produced the best performance to estimate the shear strength of prestressed concrete members with sufficient shear reinforcement. The MCFT-based design expressions, however, provided unconservative strength estimations for members that failed in shear but exhibited signs of horizontal shear damage and/or anchorage zone distress. The ACI 318-08 detailed method was found to be less conservative than the MCFT-based design expressions. Additionally, on the basis of a careful examination of test results included in the database, a new limit for the minimum shear reinforcement was proposed. The database was also used to investigate the shear behavior of prestressed concrete members. This investigation revealed that there was no evidence of size effect in the shear strength of prestressed concrete members with sufficient shear reinforcement. Additionally, it was found that prestress force and shear reinforcement increased the shear strength although there was an upper limit on the effectiveness of shear reinforcement. / text

No description available.

[pt] Este estudo apresenta o comportamento de misturas de areia e solo argiloso com teores variados de cinza volante, proveniente do processo de queima de carvão mineral no Complexo Termelétrico Jorge Lacerda, localizado no município Capivari de Baixo, no estado de Santa Catarina. O objetivo da presente pesquisa consiste em avaliar a aplicabilidade do uso de misturas solo-cinza e solocinza- cal em obras geotécnicas, como camadas de aterros sanitários, solos de fundação e estabilização de taludes. Foram realizados ensaios de caracterização física, química e mecânica (ensaio de compactação e ensaio de cisalhamento direto). Os ensaios de cisalhamento direto foram realizados em amostras de solo argiloso compactadas na umidade ótima e no peso específico seco máximo correspondente, com teores de cinza volante de 15 por cento e 30 por cento em relação ao peso seco do solo. Já os ensaios em amostras de areia foram realizados para uma densidade relativa de 50 por cento e umidade ótima de 10 por cento, com teores de cinza volante de 15, 30 e 40 por cento em relação ao peso seco do solo. Para as misturas solo-cinza-cal, adicionou-se 3 por cento de cal em substituição ao peso seco da cinza. Foi analisada a influência do tipo de solo, teor de cinza, adição de cal e tempo de cura (0, 30, 100, 125 e 140 dias) para as misturas, sendo a cura adotada somente para as misturas com areia. Os resultados mostraram-se mais satisfatórios para as misturas com solo argiloso, sendo a adição de cal mais eficiente para a mistura com menor teor de cinza. Na ausência de cal, o melhor comportamento obtido foi para a mistura com 15 por cento de cinza. Quanto às misturas com areia e sem cal, os resultados foram inferiores à areia; já no caso das misturas areia-cinza-cal, não foi possível definir um padrão do comportamento com relação ao tempo de cura, pois ainda que tenha havido um aumento da coesão a determinados dias, este ganho veio acompanhado de uma redução no ângulo de atrito, fazendo com que a areia mantivesse um comportamento melhor. Contudo, o teor de 27 por cento de cinza, sob 140 dias de cura, proporcionou ao solo um aumento de ambos os parâmetros, sendo, portanto, o teor ótimo a ser utilizado. Dessa forma, ainda que o emprego da cinza volante em misturas com o solo argiloso tenha se mostrado mais satisfatório, este material também pode ser utilizado em misturas com areia, desde que submetido a elevados períodos de cura e que contenham uma porcentagem de cinza em torno do teor ótimo encontrado, o que viabiliza o emprego positivo deste material em aplicações geotécnicas, possibilitando uma destinação ambientalmente correta deste resíduo e dando um fim mais nobre a este material. / [en] This study presents the behavior of sand and clay soil mixtures with different contents of fly ash, which comes from the coal burning process in Thermoelectric Complex Jorge Lacerda, located in the city of Capivari de Baixo, in Santa Catarina. The aim of this research is to assess the applicability of using soil-ash and soil-ash-lime mixtures in geotechnical works, like landfill layers, foundation soils and slope stabilization. Physical, chemical and mechanical (compaction test and direct shear test) were performed. Direct shear tests were performed on clay soil samples compacted at the optimum moisture content and the corresponding maximum dry specific gravity, with fly ash contents of 15 and 30 per cent, related to the dry weight of soil. Tests on sandy soil samples were performed at the relative density of 50 per cent and optimum humidity of 10 per cent, with fly ash contents of 15, 30 and 40 per cent related to the dry weight of soil. For soil-ash-lime mixtures, it was added 3 per cent of lime to replace the dry weight of ash. It was studied the influence of different parameters: soil type, ash content, lime addition and curing time (0, 30, 100, 125 and 140 days) for the mixtures. Curing process was adopted only for sandy soil mixtures. Results were more suitable for clay soil mixtures, and lime addition was more efficient for the mixture with the lowest ash content, related to 12 per cent. In the absence of lime, the best performance was obtained for the mixture with 15 per cent of ash. For sandy soil mixtures and without lime, the results were inferior to sand; and in the case of soil-ash-lime mixtures, it was not possible to define a pattern of behavior to the curing time, because although there has been an increase in cohesion certain days, this gain was followed by a reduction in friction angle, which has maintained the best performance of sand. However, the ash content of 27 per cent, at 140 days of curing, caused an increase of both parameters, what means that this ash content is the optimum content to be used. Thus, although the use of fly ash in mixtures with clay soil has been more satisfactory, this material can also be used in mixtures with sandy soil, since it contains an ash content around the optimum content found, and since it has been submitted to elevated curing periods, what enables the positive employment of this material in geotechnical applications, providing an environmentally correct disposal of this waste and giving it a noblest destination.

La gestion des déchets radioactifs est une question environnementale importante, en particulier dans les pays où l'énergie nucléaire est générée. L'Andra (Agence Nationale pour la gestion des Déchets RAdioactifs) étudie la solution d'un stockage géologique profond dans un couche d'argilite Callovo Oxfordienne (COx). L'étanchéité des galeries souterraines est partiellement assurée par une barrière mécanique en béton qui est directement en contact avec l'argilite. Tels projets nécessitent une prédiction de déformations irréversibles dans le temps sur une grande échelle, afin d'évaluer la durabilité de l'accouchement. Même si les propriétés physiques de la plupart des matériaux impliqués (argilite et béton par exemple) sont maintenant raisonnablement connues, ils existent que quelques études sur le comportement des interfaces de contact entre ces matériaux. Ce sujet est d'une grande importance pour prédire une durée de vie provisoire des installations de stockage de déchets nucléaires.Au cours de cette thèse, le comportement mécanique de l'interface argilite / béton a été étudié. Le Callovo Oxfordian est considéré comme une barrière géologique idéale grâce à sa très faible perméabilité. Cependant, son comportement est gouverné par un couplage thermo-hydro-mécanique de haute complexité, qui est en cours d'investigation avec des expériences en laboratoire et textit{in-situ}. Avec la préparation des échantillons d'interface, une étude courte sur l'absorption d'eau liquide dans la non-confinée argilite, a été réalisée. Afin de caractériser le comportement à court terme de l'interface, plusieurs essais de cisaillement direct ont été effectués sous différentes conditions limites, en utilisant le dispositif expérimental BCR-3D situé dans 3SR.Pour l'étude du comportement mécanique à long terme de l'interface, la conception et développement d'un nouvel appareil expérimental. Une des parties les plus importantes de ce travail, comprend la conception et le développement de SInC Box - Shearing Interfaces Creep Box - un dispositif original pour l'étude des déformations différées des interfaces. Plusieurs essais de fluage ont été effectués sur des éprouvettes d'interface, permettant d'étudier le comportement différé de l'interface en cisaillement. Le comportement mécanique post-fluage de l'interface argilite / béton a également été exploité. Les résultats expérimentaux de la réponse différé ont également été analysés selon des modèles analytiques viscoélastiques et simulations numériques. / The management of radioactive waste is an important environmental issue, in particular in the countries where nuclear power is generated. In Eastern France, The French National Radioactive Waste Management Agency (ANDRA) is investigating the behaviour of a deep geological repository in Callovo Oxfordian clay-rock (COx). The sealing of the underground repository tunnel, is partly ensured by a mechanical barrier made of concrete, directly in contact with the rock. Such projects require prediction of irreversible deformations over a large time scale, in order to assess the durability of the confinement. Even though the physical properties of most of the materials involved (rock and concrete for example) are now reasonably known, there have been only a few studies of the behaviour of the contact interfaces between these materials. This subject is of great importance for predicting a tentative life-time of nuclear waste storage facilities.During this PhD work the mechanical behaviour of the clay-rock/concrete interface has been investigated. The Callovo Oxfordian is considered as an ideal geological barrier because of its extremely low permeability. However, it is governed by a thermo-hydro-mechanical behaviour of high complexity, which is continuously under investigation with both laboratory and in-field experiments. The preparation of the interface samples involved a short study on the liquid water uptake in the unconfined clay-rock. In order to characterise the short-term behaviour of the interface, direct shear tests have been performed under different boundary conditions, using the BCR3D experimental device located in 3SR.The investigation of the long-term mechanical behaviour of the interface required the design of a new experimental apparatus. One of the most important parts of this study includes the conception and development of SInC Box -- Shearing Interfaces Creep Box -- an original device for the study of delayed deformations of interfaces. Different sets of creep tests have been performed on the interface samples allowing the investigation of the interface's delayed behaviour in shear. The post-creep mechanical behaviour of the clay-rock/concrete interface has also been exploited exhibiting great interest. The experimental results of the delayed response have been further analysed using analytical visco-elastic models and numerical simulations.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22125号 / 工博第4655号 / 新制||工||1726(附属図書館) / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 渦岡 良介, 教授 角 哲也, 准教授 佐山 敬洋 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

In Sweden, there exists a large number of dams. Many of them are founded on rock masses normally affected by the presence of sub-horizontal rock fractures, which makes sliding along rock joints under the dam foundation one of the most critical failure mechanism. Various attempts have been made to relate the peak shear strength of rock joints to measurable parameters. However, the uncertainty in the determination of the shear strength of rock joints is nonetheless still significant.The main aim of this thesis is to investigate, develop and apply analytical and numerical techniques for estimation of peak shear strength of natural and unfilled rock joints. In a first step, the peak shear strength of several natural and unfilled rock joint was calculated by using surface aperture measurements from high-resolution optical scanning and a modified version of the analytical criterion previously developed by Johansson and Stille in 2014. In a second step, PFC2D was utilised to perform numerical shear tests on two-dimensional profiles selected from high-resolution optical scanning on unweathered and perfectly mated tensile induced rock joints.The results from the analytical approach show that the calculated peak shear strengths of the analysed samples are in good agreement compared with the laboratory investigations. Conversely, the obtained results from the numerical approach show lower peak shear strengths in the analysed two-dimensional profiles compared with the conducted laboratory shear tests.The analytical approach together with the advanced techniques to measure surface roughness available today, may be a possible way forward towards a methodology to determine peak shear strength of large-scale natural rock joints in-situ. / Bergsprickors skjuvhållfasthet är en avgörande faktor för att kunna bestämma säkerheten mot gliding för dammar där sub-horisontella utbredda bergsprickor existerar. Samtidigt är parametern svår att bestämma då den påverkas av flera faktorer som sprickytans råhet, vittringsgrad, normalspänning, skala samt passning. Skjuvhållfasthet av bergsprickor kan bestämmas genom att använda empiriska och analytiska brottkriterier samt numeriska metoder. Problemet med de befintliga metodikerna är att de inte beaktar inverkan från sprickans passning. Detta innebär att hållfastheten riskerar att överskattas.Det övergripande syftet med denna licentiatuppsats är att studera, utveckla och tillämpa analytiska och numeriska metoder för uppskattning av skjuvhållfasthet för naturliga och ofyllda bergsprickor. I ett första steg beräknades skjuvhållfastheten för ett antal naturliga och ofyllda bergsprickor. Detta gjordes genom att mäta aperturen baserat på högupplöst skanning och en vidareutvecklad version av det analytiska kriteriet som föreslogs av Johansson och Stille 2014. I ett andra steg användes PFC2D för att genomföra numeriska skjuvtester på två-dimensionella sprickprofiler baserat på högupplöst skanning av perfekt passade och draginducerade bergsprickor.Resultaten från uppskattad skjuvhållfasthet med den analytiska metodiken visar på en bra överensstämmelse i jämförelse med de utförda skjuvförsöken. Resultaten från de utförda analyserna med PFC2D visar på en något lägre skjuvhållfasthet än vad som observeras i verkligheten.Den utvecklade analytiska metodiken, tillsammans med de avancerade tekniker som idag finns för att mäta sprickytornas råhet, bedöms kunna utgöra ett första steg mot att bättre kunna bestämma den storskaliga skjuvhållfastheten för bergsprickor i fält. / <p>QC 20190402</p>