▼  In February of 2017 after a period of heavy rainfall, a slope destabilized behind Fremont Hall on the campus of Cal Poly San Luis Obispo. The geology of this slope stability failure is the Franciscan Complex. The Franciscan Complex, when weathered in place, results in clay soil that makes up the typical soil mantle on the hills throughout the region. Peak strength is the typical parameter tested to assess the strength of the soil. For the Franciscan-derived clay, the residual strength is the focus of this study to understand slope failure since the clay is the weakest portion of the matrix in the Franciscan Complex. Both intact and remolded specimens were processed from the samples obtained from the slide for laboratory testing. The tested material is considered representative of the soil found in the Franciscan Complex along the California coast and other similar regions worldwide where the presence of this mélange results in slope instabilities. Three different shearing tests were performed to study the residual strength: direct shear reversal, ring shear, and large-scale direct shear reversal. Sampling soil from the slide took place twice: once in 2017 and once in 2019. A block of soil sampled in 2017 was taken after the toe of the slope was cut for reconstruction which resulted in an exposed slide plane. In 2019, additional samples were retrieved near the toe of the slope after subsequent failure of the slope. Although the material was assumed to be from the slide plane, there is a possibility it may have originated from the surrounding matrix. Intact and remolded specimens were tested in direct shear reversal tests, and remolded specimens were tested in ring shear tests. The 2019 source was tested in the large-scale direct shear reversal tests because the material obtained during 2017 was not enough to replicate the large specimen. Remolded specimens were prepared by passing through sieve No. 40. A secondary set of tests were performed on specimens prepared by passing through sieve No. 200. When comparing remolded against intact specimens, the clasts within the intact material exhibited an influence on the residual strength by an approximate difference of 20%. The results also indicated the liquid limit (LL) had an impact on the residual strength; higher value LL exhibited lower residual strength, and lower value LL exhibited higher residual strength. When comparing the laboratory results against in situ CPT tests, the values from the CPT fell within the range of the laboratory residual strength corresponding to the slide’s depth of movement. The results from testing these specimens showed the soil obtained directly from the slide failure exhibited a residual strength represented as friction angle of 14° ± 2° for intact soil specimens, 11° ± 3° for remolded specimens of the 2017 failure plane passing through No. 40 sieve, and 22° ± 2° for remolded specimens of the 2019 sample location passing though No. 40 sieve. The remolded specimens passing through sieve No. 200 produced even… Advisors/Committee Members: Robb Moss.

▼ Many bridges in the United States were built using longitudinal members, called girders, made of prestressed concrete. In prestressed concrete, because concrete cannot resist high tensile forces, tensioned steel cables, called strands, are used to produce compression on the concrete member to improve its behavior when it is in service. Corrosion is a concern in old prestressed concrete bridges, especially bridges built in marine environments. Corrosion induces cracks in the concrete superstructure which accelerates the deterioration rate and can result in a partial loss of the concrete body and exposure of the embedded steel. This causes degradation in the load-carrying capacity of the bridge girders which raises a danger to vehicles, passengers, and pedestrians. Consequently, decisions need to be made by authorities on whether to replace, repair, or load post these bridges. Two main types of loads exist in bridge girders, namely shear forces and bending moments. Extensive research has focused on the ability of corroded prestressed concrete girders to resist stresses produced by moment, or flexure. However, bridge girders must also resist shear forces. This research studies the shear strength of corroded prestressed concrete girders which can, then, be expanded further to evaluate the possible retrofitting techniques for restoring, or enhancing, their shear strengths. Two old prestressed concrete girders built in the 1960's and 1970's were delivered to the Murray Structural Engineering Laboratory at Virginia Tech from two decommissioned bridges in Virginia. The two girders showed signs of deterioration due to corrosion. These signs include concrete losses, cracks, areas of unsound concrete, and exposed strands. Non-destructive testing was performed on the girders to evaluate the severity of their in-situ conditions. Then, two destructive full-scale tests were performed on each girder in the lab to estimate their actual shear strengths. Shear strengths of the girders were also predicted using four methods present in the current American Association of State Highway and Transportation Officials, AASHTO, and the American Concrete Institute, ACI, codes. In addition, analyses using other advanced tools were also carried out. Evaluation of these methods and comparisons with the experimental results were performed to reach to conclusions and recommendations for future work. Corrosion in strands seemed to not have as much influence on the shear strength as on the flexural strength. Destructive shear tests indicated that the actual shear strengths of the girders investigated in this research exceeded nominal strengths predicted by the current codes, the AASHTO and the ACI. However, the flexural strengths were reduced. Possible reasons for the girders' behaviors are discussed. Advisors/Committee Members: Roberts-Wollmann, Carin L. (committeechair), Koutromanos, Ioannis (committee member), Hebdon, Matthew Hardy (committee member).

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Os movimentos de massa de solo, geralmente, estão relacionados com a mobilização da resistência de uma ou várias superfícies de ruptura pré-existentes. Dessa maneira, o conhecimento da propriedade que rege esse comportamento (resistência ao cisalhamento residual) é de extrema importância no estudo da estabilidade de solos. Segundo Skempton (1985), resistência ao cisalhamento residual é a resistência mínima constante que o solo pode atingir, a baixas taxas de cisalhamento, após sofrer grandes deslocamentos. A determinação dos parâmetros de resistência ao cisalhamento residual pode ser realizada através de ensaios de cisalhamento por torção do tipo ring shear, adequado para estudar os mecanismos atuantes na ruptura, uma vez que permite a continuidade dos deslocamentos no solo. Nesse contexto, a pesquisa teve por objetivo desenvolver um equipamento de cisalhamento torsional baseado no ring shear descrito por Bishop et al. (1971) para avaliar o comportamento do solo a grandes deformações. O equipamento projetado foi validado, preliminarmente, segundo os resultados já publicados na literatura.

Landslides, generally, are related with the mobilization of shear strength of one or more preexisting rupture surfaces. Thus, knowledge of the property that governs this behavior (residual shear strength) has extreme importance in the stability soils study. According to Skempton (1985), residual shear strength is the minimum constant strength attained at low shear rates, at large displacements. The residual shear strength parameters can be accomplished through ring shear tests, suitable for studying the mechanisms in the rupture, since it provides continuity of displacements in the soil. In this context, the research aimed to develop a device based on ring shear described by Bishop et al. (1971) to evaluate the soil behavior in large deformations. The equipment designed was validated, preliminarily, according to the results already published in the literature.

Advisors/Committee Members: Heineck, Karla Salvagni.

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A compactação de solos em climas com elevada concentração de precipitação apresenta dificuldade que afetam o cronograma físico e financeiro das obras. A execução de aterros com teor de umidade elevado gera solos com grau de saturação elevado que, por sua vez, induz poropressões indesejáveis durante a construção. Assim, o solo é, em geral, compactado no entorno do teor de umidade ótimo (+/- 3%) e densidade seca máxima (GC de 95% a 105%). No entanto, é possível avaliar o solo de modo a possibilitar a compactação acima do teor de umidade ótimo. Estes aterros são chamados aterros úmidos. Os poucos estudos realizados nestas condições encontraram como uma das dificuldades a ausência da medição da sucção durante os ensaios. A medição da sucção logo após a compactação utilizando-se o tensiômetro de alta capacidade (TAC) possibilitou estudos sobre o desenvolvimento da poropressão de água com o carregamento. Utilizando de ensaios triaxiais de umidade constante (CW) e com o uso do TAC é possível se obter as informações importantes para a execução de aterros úmidos. O presente trabalho estuda experimentalmente o comportamento de um solo residual de gnaisse compactado na umidade ótima e em duas condições de compactação acima do teor de umidade ótimo. São realizados ensaios na condição saturada (ensaios CIU) e não saturada (ensaios CW) com medição direta de sucção com o tensiômetro de alta capacidade. O trabalho apresenta um estudo do comportamento dos solos compactados no estado quasi-saturado e avalia os seguintes aspectos: Efeito da técnica da contrapressão para saturação no comportamento mecânico do solo, desenvolvimento da sucção após a compactação e durante ensaios de resistência, correlação entre a curva de retenção de água e o comportamento mecânico do solo, aplicação das equações de Bishop (1959) e Fredlund et al. (1978), procedimento para determinação da superfície de ruptura. O trabalho conclui que o solo residual estudado permite a construção de aterros úmidos sem o desenvolvimento de poropressões de água indesejáveis. Conclui-se ainda que com o uso do TAC associado a ensaios triaxiais CW é possível a obtenção da envoltória de ruptura na condição não saturada de forma simples.

The compaction of soils in climates with high concentration of rainfall has created problems that affect the physical and financial schedule of works. Embankments constructed with soils having high water content generate high degree of saturation, which, in turn, induces undesirable pore water pressures during construction. In general, the soil is compacted in the vicinity of the optimum water content (+/-3 %) and maximum dry density (DC 95% to 105 %). However, it is possible to evaluate the soil behaviour to enable compaction above the optimum moisture content. These embankments are called \"wet landfills\". The few studies carried out in these conditions found difficulties in the measuring of the suction during tests. The measurement of suction immediately after compaction using a high-capacity tensiometer (HCT) allowed studies on the…

Advisors/Committee Members: Marinho, Fernando Antonio Medeiros.

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Cette thèse s’intéresse à l’étude l’effet de la corrosion sur les propriétés mécaniques des armatures corrodées et les performances mécaniques résiduelles des poutres corrodées. L’étude est basée sur deux poutres corrodées notées B2CL2 et B2CL3, conservées respectivement 26 ans et 28 ans en ambiance saline. Deux poutres non corrodées B2T2 et B2T3 conservées en conditions ambiantes ont également été testés afin d’identifier l'effet de la corrosion indépendamment du vieillissement.Les propriétés mécaniques des armatures corrodées ont été étudiées par des essais de traction.La limite d'élasticité et résistance à la rupture ont été étudiées sur la base de la section transversale résiduelle évaluée par perte de masse. Les résultats ont montré que les effets de la corrosion sur la diminution ductilité étaient très importants. La forme de la section transversale résiduelle apparait comme étant un paramètre essentiel affectant la ductilité de l'armature.Les performances résiduelles en flexion des poutres corrodées ont été étudiées. Les résultats montrent que la corrosion réduit la capacité portante et de façon plus significative, la flèche maximale à rupture en raison d’un changement de mode de rupture. La diminution de la charge de plasticité apparait en relation avec la perte de section d’acier tendu due à la corrosion Des poutres de portées courtes ont été réalisées à partir des poutres corrodées après les essais de flexion. Les tests mécaniques ont été effectués en flexion pour vérifier la réponse des poutres courtes corrodées. Les poutres courtes corrodées ont péri en flexion avec une bonne ductilité tandis que les poutres courtes non corrodées ont péri comme prévu en cisaillement suivant un mode de rupture fragile, qui a montré que la corrosion de l'armature pouvait modifier les modes de défaillance.Les produits de corrosion ont été recueillis à partir de l'armature corrodée de B2Cl3. Des expériences XRD et TG ont été menées afin d'identifier la composition des produits de corrosion. Le coefficient d'expansion des produits de corrosion a été déduit, ce qui pourrait être utile pour les recherches futures concernant le mécanisme de fissuration du béton d'enrobage.

The thesis aims to study the influence of chloride corrosion on the mechanical properties ofthe reinforcement and RC beams. The experiments were based on two corroded beams named B2Cl2 and B2Cl3, with a corroded age of 26 years and 28 years respectively. Two noncorroded beams B2T2 and B2T3 which were cast in the same condition and same time were also tested in order to make clear the corrosion effect.The mechanical properties of the corroded reinforcement were investigated by the tensiontests. The yield strength and ultimate strength were studied based on the residual gravimetrical cross-section. The results found that the impact of corrosion on the ductility was more significant than that of the strength. The shape of residual cross-section was considered to be in deep relationships with the ductility of the reinforcement.The flexural performances of the…

Advisors/Committee Members: François, Raoul (thesis director).

▼ The drained residual shear strength at the interface between soils and solid materials can be of importance in evaluating the stability of geotechnical structures. Drained residual shear tests have been performed at relatively high effective normal stress levels, over 50 kPa. These effective normal stresses are relevant for many field applications and manageable in typical laboratory shear testing. However, there are field applications, such as offshore pipelines where the effective normal stresses can be below 50 kPa. There are two significant challenges in measuring the drained shear strength at low effective normal stresses: (1) a small amount of friction in a test device can affect the results; (2) small shear rates may be required to achieve drained conditions at the soils. A tilt table test method has been developed to overcome these challenges. The objective of this work is to measure the drained residual shear and interface strength of soils at low effective normal stresses so as to provide logical explanations of the effect of various parameters. These parameters include soil index properties, clay content, clay mineralogy, stress history, and loading rate together with the effective normal stress levels. The total 74 tilt table tests are performed to measure the drained residual shear and interface strength of marine clays and sand-kaolinite mixtures. The following conclusions can be drawn based on the test results. 1. The drained residual shear strength both for the interface and for the soils is not affected by the over-consolidation ratio. 2. The drained residual shear strengths for the interfaces are all less than the drained residual shear strengths of soils. The drained residual strength of interface depends on the roughness of interface, clay mineralogy. 3. The empirical correlations and shear test results at higher effective normal stresses cannot be extrapolated to lower effective normal stresses. 4. Clay mineralogy and clay contents together with the magnitude of effective normal stress are the most important factors to estimate the drained residual shear strength of cohesive soils. 5. Cohesionless soils exhibit a constant residual secant friction angle regardless of effective normal stress levels. Advisors/Committee Members: Gilbert, Robert B. (Robert Bruce), 1965- (advisor), Zornberg, Jorge G. (committee member).

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Esta dissertação apresenta os procedimentos experimentais e resultados obtidos na caracterização geotécnica de um solo residual de granulito envolvido na instabilização de uma encosta no município de Gaspar, SC, com o objetivo de contribuir para a compreensão dos processos desencadeadores das instabilidades de encostas em Santa Catarina. O movimento rotacional extremamente rápido envolveu um volume de cerca de 110.000 m³, e provocou a morte de duas pessoas. A ruptura ocorreu uma semana depois de um episódio de elevada precipitação pluviométrica (cerca de 440mm em 2 dias). Este estudo compreendeu a execução de ensaios de laboratório para determinação de propriedades geotécnicas do solo residual de granulito e uma análise simplificada da estabilidade da encosta. Foram realizados ensaios de caracterização física, difração de Raios-X, compressibilidade, expansibilidade, condutividade hidráulica e resistência ao cisalhamento com ensaios tipo ring shear, cisalhamento direto, ensaios triaxiais tipo CIU e com trajetória de tensões especial, em amostras indeformadas e remoldadas. O solo tem uma textura predominantemente siltosa, com a fração tamanho argila (aproximadamente 15%) composta principalmente por caulinitas. As análises de microscopia mostraram que grande parte dos minerais argilosos se encontra na forma de grumos com tamanho de silte. Estes grumos se desagregam quando submetidos a esforços mecânicos de cisalhamento. O solo residual apresenta um baixo coeficiente de condutividade hidráulica (da ordem de 10-7 a 10-8 m/s) e os ensaios mostraram uma redução de cerca de uma ordem de magnitude do coeficiente com o aumento da tensão de confinamento até 400 kPa. Os ensaios oedométricos revelaram a natureza estruturada de solo e a dificuldade de determinação da tensão de pré-adensamento do solo. Os ensaios de cisalhamento direto em corpos de prova remoldados e em corpos de prova indeformados forneceram parâmetros de resistência ao cisalhamento de pico similares (ø’~25º e c’ =10 kPa). Ensaios triaxiais em corpos de prova indeformados utilizando uma trajetória de tensões com acréscimo de poropressão indicaram parâmetros de resistência ø’ =32,5º e c’ =12,5 kPa. O ângulo de atrito interno residual (ring shear) determinado neste solo foi de 9º. As análises de estabilidade realizadas mostraram que a encosta passa a apresentar instabilidade quando o nível de água no interior do maciço atinge a cota 59m acima do nível do mar.

This dissertation presents the experimental procedures and results obtained in the geotechnical characterization of a granulite residual soil involved in a landslide of a cut slope in the town of Gaspar, SC, with the objective of understanding the processes involved in such failure. This rotational extremely rapid slide involved a soil volume of around 110.000 m³ and caused the deaths of two people. The failure occurred a week after an episode of high rainfall (about 440mm in 2days). This study included the implementation of laboratory tests to determine geotechnical properties of the granulite residual…

Advisors/Committee Members: Bressani, Luiz Antonio.

▼ The aim of this thesis is the examination of the influence of the acceleration and the rate of displacement to the residual strength of soils which are connected to landslides in Greece, such as flysch. The thesis consists of two volumes. The first volume includes the eight chapters with the presentation of the laboratory investigation and the second volume includes the four appendixes. The first chapter is the introduction of this thesis where the aim and the flow structure are specified. The second chapter presents a literature review. The third chapter presents the ring shear apparatus of the Laboratory of Soil Mechanics, Foundation and Geotechnical Earthquake Engineering and its principles of operation. There are also described the sample presentation, the testing techniques and the calculation and presentation of results. The end of the chapter presents the procedure of direct shear box tests. The calibrations of ring shear apparatus, the motor drive units and the discussion of the testing errors in the accuracy of measurements are presented in Appendix A. The fourth chapter presents the tested soils and the laboratory program followed in ring shear and direct shear box tests. The samples used were from four different types of decomposed flysch from regions of Western Macedonia and Ipeirus. Twenty four ring shear tests were carried out for these samples. The fifth chapter presents the analysis of results from the ring shear and direct shear box tests for each flysch type. The extended presentation of ring shear tests is included in appendix B and from direct shear box tests is included in appendix C. The observations from the study of the microstructure in the shear zone are included in appendix D. This chapter presents the specification of shear mode in residual strength, the variation of residual strength with the normal stress and the envelopes of shear and critical strength in slow rate of displacement for each of the four flysch types. It also includes the results of the tests for the influence of the rate displacement in the residual strength for each flysch sample individual and for each flysch type. The sixth chapter presents the discussion of ring shear and direct ring shear test results according to the threshold strength, the fast peak strength, the fast residual strength, the slow peak strength after fast shearing and specimen consolidation. For each of the above strengths, there are specified the inflective parameters. There were specified four different types of variation of the fast residual strength with the increasing rate of displacement (types A, B, C, D), when there is ability of suction in shear zone. The seventh chapter presents the conclusions of the thesis for slow residual strength, threshold strength, fast peak strength, fast residual strength and slow peak strength after fast shearing and specimen consolidation. The practical implication is focused on the numerical simulation of the behaviour of pre-existed shear zones. This simulation is critical for the reliability of cinematic…

▼ When a clay soil is sheared, clay particles along the shear plane become aligned in the direction of shear, forming â slickensidedâ surfaces. Slickensided surfaces are often observed along the sliding plane in field landslides. Because the clay particles along a slickensided surface are already aligned in the direction of shear, the available shear resistance is significantly less than that of the surrounding soil. During an earthquake, ground shaking often causes landslide movement. For existing landslides or repaired landslides that contain slickensided rupture surfaces, it is reasonable to expect that the movement will occur along the existing slickensided surfaces, because they are weaker than the surrounding soil. The amount of movement that occurs is controlled by the dynamic resistance that can be mobilized along the slickensided surfaces. The objective of this study was to investigate, through laboratory strength tests and centrifuge model tests, the shearing resistance that can be mobilized on slickensided rupture surfaces in clay slopes during earthquakes. A method was developed for preparing slickensided rupture surfaces in the laboratory, and a series of ring shear tests, direct shear tests, and triaxial tests was conducted to study the static and cyclic shear resistance of slickensided surfaces. Two dynamic centrifuge tests were also performed to study the dynamic shear behavior of slickensided clay slopes. Newmarkâ s method was used to back-calculate cyclic strengths from the centrifuge data. Test results show that the cyclic shear resistance that can be mobilized along slickensided surfaces is higher than the drained shear resistance that is applicable for static loading conditions. These results, coupled with a review of existing literature, provide justification for using cyclic strengths that are at least 20% larger than the drained residual shear strength for analyses of seismic stability of slickensided clay slopes. This represents a departure from the current state of practice, which is to use the drained residual shear strength as a â first-order approximation of the residual strength friction angle under undrained and rapid loading conditionsâ (Blake et al., 2002). Advisors/Committee Members: Duncan, James Michael (committeechair), Brandon, Thomas L. (committee member), Gutierrez, Marte S. (committee member), Kapania, Rakesh K. (committee member), Martin, James R. II (committee member).

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[pt] Neste trabalho, analisou-se a influência da sucção na resistência ao cisalhamento de um solo residual jovem de filito da região metropolitana de Belo Horizonte (MG). A fim de determinar a resistência ao cisalhamento do solo não saturado, foram realizados ensaios de cisalhamento direto com sucção controlada em amostras indeformadas e teor de umidade natural. Foram feitos também ensaios de cisalhamento direto convencional, em corpos de prova indeformados e submersos. Tais ensaios foram executados com diferentes níveis de tensão. Determinaram-se as curvas de retenção de umidade através do método do papel filtro, para se obter a relação entre a sucção e o teor de umidade do solo. O programa experimental compreendeu também ensaios de caracterização geotécnica, análises químico- mineralógicas. A partir da análise dos resultados de ensaios de cisalhamento direto convencional e com sucção controlada foi possível estabelecer uma envoltória de resistência ao cisalhamento em três dimensões para o solo estudado, função das variáveis de tensão ((sigma)-ua) e (ua-uw). Também são apresentadas algumas considerações sobre a influência da sucção na compressibilidade do material. Por fim, fez-se uma comparação dos resultados obtidos para a resistência ao cisalhamento com estimativas indiretas através de formulações simplificadas que usam os parâmetros efetivos de resistência e a curva característica de sucção (i.e. Lytton, 1995; Vanapalli et al., 1996; Fredlund et al., 1996; Oberg e Sallfors, 1997), assim como com outros resultados encontrados na literatura técnica.

[en] This work intends to evaluate the influence of suction in the shear strength of a young residual filite soil from Belo Horizonte city, of Minas Gerais, Brazil. The experimental program included conventional tests of geotechnical, chemical and mineralogical characterization. The relationship between suction and water content of soil was obtained by the filter paper method and represented graphically by soil-water characteristic curves (SWCC). In order to determine the shear strength of unsaturated soil, direct shear tests with controlled suction were executed with soil samples in their natural state. In addition, conventional shear strength tests were performed with undisturbed and submersed specimens. Both types of tests were performed with different values of stress. From the analysis of the tests´ results it was possible to establish a three- dimensional shear strength envelope in function of the stress state variables ((sigma)-ua) and (ua-uw). Moreover, some considerations about the influence of stress variables in compressibility of soil are discussed. Finally, a comparison of the results obtained for the soil´s shear strength was made with different prediction models using the SWCC and the effective strength parameters (i.e. Lytton, 1995; Vanapalli et al., 1996; Fredlund et al., 1996; Oberg e Sallfors, 1997). The results were also compared with other data found in the literature.

Advisors/Committee Members: TACIO MAURO PEREIRA DE CAMPOS.

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[pt] Neste trabalho se estuda a influência de um fluido alcalino na resistência ao cisalhamento de dois solos provenientes de Poços de Caldas-MG, sendo um deles um solo residual jovem de sienito e o outro um colúvio. Para tanto, elaborou-se um programa experimental que consistiu na execução de ensaios triaxiais CIU (solo residual jovem) e de cisalhamento direto (solo coluvionar), tanto com os solos no estado natural como contaminados. A contaminação dos solos se deu pela substituição total ou parcial do fluido intersticial por um licor cáustico, resíduo proveniente do processo do beneficiamento da bauxita. Ensaios de caracterização física, química e mineralógica, com os solos em ambos os estados, foram realizados com o intuito de auxiliar na análise dos resultados dos ensaios de resistência. Os resultados obtidos mostraram que os solos são suscetíveis à ação do licor, notando-se um decréscimo dos parâmetros de resistência.

[en] This work presents a study concerning the influence of an alkaline fluid in the shear strength of two soils originating from Poços de Caldas-MG, which one of them is a sienitic residual and the other a colluvium. For that, it was elaborated an experimental program consisting of the execution of CIU triaxial (residual soil) and direct shear (colluvium) tests. The tests were performed with the soils in the natural and contaminated states. The soils were contaminated through total or partial substitution of the pore fluids for a caustic liqueur, a residue originating from alumina production process. In order to provide better support for the analysis of strength tests results, it were performed physical, chemistry and mineralogical characterization tests, with the soils in both states. The experimental program results have shown that the liqueur causes loss of strength in both soils.

Advisors/Committee Members: TACIO MAURO PEREIRA DE CAMPOS.

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Neste trabalho estuda-se o comportamento tensão-deformação de dois horizontes de um solo residual de gnaisse, pertencentes a um perfil típico da cidade de Viçosa-Minas Gerais, na condição saturada e sob diferentes valores de sucção. O estudo apóia-se em ensaios de caracterização física e mineralógica, em ensaios destinados às análises porosimétricas e morfológicas (lâminas delgadas), e em ensaios de compressão triaxial realizados em corpos de prova não saturados e saturados, estes sujeitos a diferentes direções de cisalhamento, em ambos solos, e distintas trajetórias de tensão, no solo jovem. Nos ensaios triaxiais saturados mostra-se que a resistência dos dois solos foi independente da direção de cisalhamento e que a deformabilidade revelou-se mais anisotrópica no solo maduro, que no solo jovem, este visualmente mais heterogêneo. Mostra-se, que o intercepto de coesão cresce com a sucção numa relação que pode ser bem representada por uma função hiperbólica e que o ângulo de atrito interno praticamente não apresentou variação com a sucção matricial. Apresenta-se uma alternativa de previsão da envoltória de resistência, baseada nos parâmetros de resistência do solo saturado e nos resultados de ensaio correspondente a uma sucção conhecida. A curva de plastificação do solo jovem pôde ser representada razoavelmente bem pela curva adotada nos modelos derivados da mecânica dos solos dos estados críticos (Cam-Clay modificado). A curva é centrada no eixo hidrostático e sua forma não apresenta mudança marcante durante o encruamento do solo, o qual foi obtido através da união de pontos com o mesmo trabalho plástico.

This thesis deals with the stress-strain behavior of a mature soil and a young soil from a typical residual soil of gneiss, as found in Viçosa-MG. This behavior is analyzed under saturated and non saturated conditions. The study rests on physical and mineralogical characterization tests, on porosimetric and morphological analyses (thin section) and on triaxial compression tests performed with saturated and non saturated soil. Saturated young and mature specimens were sheared according to different directions and saturated young soil was also sheared following various stress path. It is shown that the shear strength of saturated soil, both mature and young is independent of shearing direction. However, the visually more homogeneous mature soil showed to be more anisotropic, regarding the deformability, than the young residual soil that visually seems to be heterogeneous. The cohesion intercept tends to increase with soil suction according to a non linear relationship that can be adjusted through a hyperbolic function, while the angle of shearing stress was not influenced by soil suction. An alternative to forecast unsaturated shear strength envelope based on results of saturated soil and on tests performed at a known suction is also presented. The yielding curve of young soil was found to be fairly predicted using modified Cam-Clay model. The yield curve is centered along the hydrostatic axis of stress and its…

Advisors/Committee Members: Vilar, Orencio Monje.

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Nas últimas décadas, teorias têm sido formuladas para interpretar o comportamento de solos não saturados e estas têm se mostrado coerentes com resultados experimentais. Paralelamente, várias técnicas de campo e de laboratório têm sido desenvolvidas. No entanto, a determinação experimental dos parâmetros dos solos não saturados é cara, morosa, exige equipamentos especiais e técnicos experientes. Como resultado, essas teorias têm aplicação limitada a pesquisas acadêmicas e são pouco utilizados na prática da engenharia. Para superar este problema, vários pesquisadores propuseram equações para representar matematicamente o comportamento de solos não saturados. Estas proposições são baseadas em índices físicos, caracterização do solo, em ensaios convencionais ou simplesmente em ajustes de curvas. A relação entre a umidade e a sucção matricial, convencionalmente denominada curva característica de sucção do solo (SWCC) é também uma ferramenta útil na previsão do comportamento de engenharia de solos não saturados. Existem muitas equações para representar matematicamente a SWCC. Algumas são baseadas no pressuposto de que sua forma está diretamente relacionada com a distribuição dos poros e, portanto, com a granulometria. Nestas proposições, os parâmetros são calibrados pelo ajuste da curva de dados experimentais. Outros métodos supõem que a curva pode ser estimada diretamente a partir de propriedades físicas dos solos. Estas propostas são simples e conveniente para a utilização prática, mas são substancialmente incorretas, uma vez que ignoram a influência do teor de umidade, nível de tensões, estrutura do solo e mineralogia. Como resultado, a maioria tem sucesso limitado, dependendo do tipo de solo. Algumas tentativas têm sido feitas para prever a variação da resistência ao cisalhamento com relação a sucção matricial. Estes procedimentos usam, como uma ferramenta, direta ou indiretamente, a SWCC em conjunto com os parâmetros efetivos de resistência c e . Este trabalho discute a aplicabilidade de três equações para previsão da SWCC (Gardner, 1958; van Genuchten, 1980; Fredlund; Xing, 1994) para vinte e quatro amostras de solos residuais brasileiros. A adequação do uso da curva característica normalizada, proposta por Camapum de Carvalho e Leroueil (2004), também foi investigada. Os parâmetros dos modelos foram determinados por ajuste de curva, utilizando técnicas de problema inverso; dois métodos foram usados: algoritmo genético (AG) e Levenberq-Marquardt. Vários parâmetros que influênciam o comportamento da SWCC são discutidos. A relação entre a sucção matricial e resistência ao cisalhamento foi avaliada através de ajuste de curva utilizando as equações propostas por Öberg (1995); Sällfors (1997), Vanapalli et al., (1996), Vilar (2007); Futai (2002); oito resultados experimentais foram analisados. Os vários parâmetros que influênciam a forma da SWCC e a parcela não saturadas da resistência ao cisalhamento são discutidos.

In the last decades, theories have been formulated to interpret the behavior of unsaturated…

Advisors/Committee Members: Francisco José da Cunha Pires Soeiro, Bernardete Ragoni Danziger, Denise Maria Soares Gerscovich, Eurípedes do Amaral Vargas Junior.

▼ This thesis presents the results of research undertaken in the south Cotswolds. Emphasis is placed on the engineering geological aspects of planning and construction on hillslopes, many of which have been superficially disturbed by cambering and landslipping. Special attention is paid to the geotechnical properties of the mudstone/clay horizons of the Fuller’s Earth and the Rhaetic, with emphasis on a study of the residual shear strength parameters. During the examination of numerous gulls in the Blue Lias at Radstock, a simple classification scheme was devised for the various extension styles produced in the interbedded limestone and clay sequence. The engineering significance of these phenomena is discussed. At Radstock cambering has taken place over the Rhaetic, especially the highly plastic Cotham Beds; these horizons have been investigated at this and other localities. Superficial structures are not well depicted on conventional geological maps. An attempt is made to determine to what extent they may be identified by engineering geomorphological mapping. Only disturbances which rupture the ground surface are clearly discernible and hence reliably depicted by this type of mapping; moreover it is shown that land use can obscure evidence of past instability. Engineering geomorphological mapping has been used as a preliminary study in the realignment of the A46 north of Bath. The proposed routes are discussed and some of the potential problems highlighted. It is demonstrated that false colour infra-red photography can be of considerable use in helping to identify areas of ground disturbance. A study of the geotechnical properties of the Fuller’s Earth shows an increase in “clay fraction”, expanding lattice clay minerals, plasticity and oxidation as weathering proceeds, with a corresponding drop in shear strength, bulk unit weight and calcite percentage. The presence of thin limestone bands modifies this profile. Calcite is found to have a significant effect on the plasticity of the Fuller’s Earth. The use of the Bromhead ring shear apparatus to determine residual strength has enabled many samples to be tested at normal loads up to 600 kPa; a number of advantages over the conventional shear box are discussed. The parameter φ’r is found to be stress dependent and as a result previously published correlations with other data are critically assessed and the choice of φ’r in engineering practice is considered.

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Composite bridges are used for road and railroad bridges in Sweden and worldwide. The advantage of composite bridges is that concrete and steel is used optimally, steel in tension and concrete in compression. In order to get the interaction between steel and concrete headed stud shear connectors are used. Fatigue loading makes cracks, initiated by welding, propagate and in this way the strength of shear connectors are decreased during the fatigue life. The aim in this thesis is to investigate the residual strength of 22 mm headed stud connectors and if possible derive an equation for residual strength. In BV BRO the residual strength is neglected in design of ultimate limit state, but in e.g. Eurocode and BRO 2002 it is taken into account. One objective is to evaluate the assumption made in BV BRO. A state of art on the subject has been performed. Most previous research is focused on the endurance rather than residual strength, but some relevant research was found. From previous research and literature the fatigue life was found to be mainly affected by the range and the peak load. A literature survey on fatigue, fracture mechanics and the behaviour of shear studs have been performed to improve the understanding of the subject. The experimental work carried out within this master’s thesis is 10 push-out tests, five static and five fatigue. The push-out specimens were made according to Eurocode 4 and the headed shear studs used were 125 x 22mm. Differences and similarities in Swedish design standards and Eurocode have been investigated. These design standards have also been compared to experimental results and to previous research. The results of tests and literary survey show that the residual strength under fatigue loading constantly reduces and this reduction seems to linearly depend on the number of cycles applied. An equation was derived for residual strength. The design models Eurocode and BRO 2002 gives a bit lower residual strength than that derived from experiments performed. Arguments to support the assumption in BV BRO were not found.

Validerat; 20101217 (root)

▼ Flexible pavement structures are built in layers with a certain degree of bonding at the interface, which is affected by several factors which could be either material related, or construction related. The tack coat material type, residual application rate, tack coat coverage, and pavement surface type are attributed as material related factors. On the other hand, cleanliness, moisture, and vertical confinement pressure could be classified as construction related factors. The objective of this study was to quantify the effects of these factors on the pavement interface bonding in terms of interface shear strength. Five types of tack coats, four of which were asphalt emulsions; CRS-1, SS-1h, SS-1, and Trackless, and one paving grade asphalt binder, PG 64-22, were considered at three residual application rates; 0.14 (0.031) l/m2 (gal/yd2), 0.28 (0.062) l/m2 (gal/yd2), and 0.70 (0.155) l/m2 (gal/yd2). The selected tack coats were applied on four different pavement surface types; existing HMA, new HMA, milled HMA, and Portland Cement Concrete (PCC). In addition, for each pavement surface type, a “no tack coat” condition was included in the analysis. The influence of moisture and cleanliness were evaluated by careful application of water and dirt respectively. To simulate these test conditions, test specimens were obtained from the test sections designed and constructed at the Louisiana DOTD Pavement Research Facility using conventional tack coat application method and paving equipment. Specimens were extracted from the research facility and were tested in the laboratory at 25 (77) oC (oF) under two vertical confinement pressures, 0 (0) kPa (psi) and 138 (20) kPa (psi), using a direct shear test device. The study yielded several important conclusions. The results strongly supported the need of applying tack coats for improving pavement interface bond strength. Except for the milled surface, the rest of the surfaces failed to adhere with the HMA overlay, in absence of a tack coat. Trackless emerged as the most effective tack coat, while SS-1 and CRS-1 were among the least effective tack coat materials. On a general basis, an increase in the residual application rate showed an increase in the interface bond strength, which is why an optimum application rate could not be established within the application rate range considered in the study. Among the four pavement surface types, milled HMA surface provided the highest bond strength with the HMA overlay. The presence of dirt at the interface remarkably improved the pavement interface bond strength. Presence of moisture did not have any consequential influence on the interface bond strength. Irrespective of tack coat material type, residual application rate, and pavement surface type, interfaces subjected to 138 (20) kPa (psi) vertical confinement pressure a provided higher shear strength than those to 0 (0) kPa (psi). However, the effect of confinement diminished with an increase in the residual application rate.

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[pt] O conhecimento do comportamento de solos residuais é de grande importância para projetos geotécnicos no Brasil e, em particular, na região do Rio de Janeiro, tendo em vista que o clima tropical e as características geológicas favorecem a ocorrência de mantos residuais de grande espessura. O presente trabalho trata do estudo do comportamento tensão-deformação de um solo residual proveniente de um perfil de alteração de rocha gnáissica do maciço da Tijuca, Rio de Janeiro. Como os solos residuais gnáissicos preservam as foliações herdadas da rocha matriz, investigou-se em particular a relevância de se considerar a ocorrência de anisotropia nas características de resistência e deformabilidade destes solos. No estudo foi utilizado o equipamento triaxial cúbico desenvolvido na PUC-Rio. Este equipamento possibilita o controle independente das três tensões principais, sendo mais adequado para a reprodução das trajetórias de tensões tridimensionais, usualmente associadas com obras geotécnicas no campo, e em particular, para estudos sobre as características de anisotropia de solos. O programa experimental constou de ensaios de compressão axial e hidrostática, sob condições drenadas de carregamento, utilizando o equipamento triaxial cúbico. Foram realizados também ensaios oedométricos convencionais, de modo a se obter as características de compressibilidade do solo. Foram moldados corpos de prova a partir de blocos indeformados, paralelos e perpendiculares à foliação observada no solo, o que possibilitou a análise dos resultados para direções distintas de carregamento. Para efeito de comparação sobre a relevância do arranjo estrutural dos grãos do solo, foram ensaiados também corpos de prova compactados dos mesmos materiais. A análise dos resultados permitiu a obtenção dos módulos de deformabilidade e dos parâmetros de resistência do solo residual. Em particular, foram verificados os efeitos da direção de carregamento dos corpos de prova, do nível das tensões de confinamento, do grau de intemperismo, do arranjo estrutural dos grãos e dos efeitos do grau de saturação. Pode-se concluir que os solos estudados não apresentaram efeitos marcantes de anisotropia nas características de resistência. No entanto, quanto à deformabilidade, pode-se considerar que o solo residual jovem apresentou características anisotrópicas.

[en] The knowledge of the mechanical behaviour of residual soils is of great importance in geotechnical projects, because of its abundance in tropical regions, such as Brazil and particularly in the area of Rio de Janeiro. The present work presents a study on the fundamental stress-strain behaviour of a residual soil resulting from a profile of a gneiss rock in Rio de Janeiro. As the gneiss residual soils preservethe bedding planes from the parent rock, the relevance of considering anisotropy in the stress- strain characteristics of these soils was investigated. The cubic triaxial equipment developed at PUC-Rio was used in this research. This equipment allows the independent control of the three principal…

Advisors/Committee Members: ALBERTO DE SAMPAIO FERRAZ JARDIM SAYAO.