The use of mechanically stabilized earth (MSE) retaining walls has become quite prevalent in highway embankment applications. A design criterion for these walls was originally established by the Federal Highway Administration (FHWA) and has been modified on a state by state basis. Recently, the Texas Department of Transportation (TxDOT) has recorded several wall failures mostly due to excessive settlement and lateral wall deformation and wanted to evaluate the current state design guidelines for regionally available backfill materials. Prior to numerical modeling simulations, material parameters of regionally available backfill needed to be evaluated. As the state guidelines require 85-percent of the wall backfill material to be above the No. 4 sieve, large scale triaxial testing was an option to evaluate strength and volume change parameters. This research used cylindrical specimen 6-inches in diameter and 12- inches in height in a large scale triaxial apparatus. Three types of backfill material were tested and specimens were mixed and compacted in 4 different gradations for each material type. Each gradation was tested at confining stresses corresponding to wall heights of 10, 15, and 20 feet for a total of 36 tests. Basic material parameters such as unit weight and friction angle were evaluated directly from testing, while more complex material parameters were selected from the data for use in the Duncan-Chang elastic constitutive model. This method utilizes hyperbolic curve fitting of both strength and volumetric test data to define soil behavior parameters which include the following: modulus number (K), modulus exponent (n), initial tangent modulus (Ei), failure ratio (Rf ), initial Poisson’s Ratio (νi), and Poisson’s Ratio Parameters G, F, and d. Friction angles from triaxial testing ranged from 32 to 53 degrees having some uncertainty due to inconsistent compaction. The variation in sand and fine size particles in the backfill tended to reduce friction angles, except in the case of Type-B material where density increased due to the high percentage of sand and fines. Duncan-Chang parameters fit reasonably well with experimental data for strength barring some experimental errors. Volumetric parameters were inconclusive due to inconsistent compaction and membrane leakage. Additional testing is needed to provide more sound volumetric data.

Ingeniero Civil / En el presente trabajo de título se desarrollaron metodologías para determinar propiedades de suelos parcialmente saturados mediante un equipo triaxial fabricado por GDS Instruments. Una vez establecido el procedimiento correcto, se redactaron manuales que detallan el uso del equipo triaxial para implementar tres distintos ensayos geotécnicos: ensayo triaxial convencional, determinación de la curva característica suelo-agua y ensayo triaxial de suelos parcialmente saturados. Inicialmente, se llevaron a cabo ensayos triaxiales convencionales en el equipo GDS Instruments y en un instrumento equivalente marca Humboldt, con el objetivo de establecer el correcto desempeño del primero, y a su vez, analizar el comportamiento saturado de una arena de relaves. Dicho material, corresponde a la fracción gruesa de un relave integral, con un bajo contenido de finos no plásticos. Se utilizaron probetas confeccionadas por el método de apisonamiento húmedo (wet tamping), a densidades relativas del 40% y 60%; ensayadas a confinamientos isótropicos efectivos de 1, 2 y 4 kgf/cm2, en condición drenada y no drenada. Posteriormente, se ejecutó un primer ensayo parcialmente saturado, correspondiente a la determinación de la curva característica suelo-agua, también denominada curva de succión, que relaciona el contenido de agua en la muestra de suelo, con la succión matricial generada. Se utilizó una probeta fabricada por apisonamiento húmedo, a una densidad relativa del 60% y confinada isotrópicamente a 1 kgf/cm2. Los resultados experimentales fueron comparados con un modelo teórico desarrollado por Fredlund et al. (2002), desarrollado a partir de la curva de distribución granulométrica del material. Por último, se efectuaron ensayos triaxiales parcialmente saturados drenados, utilizando una muestra armada por apisonamiento húmedo a una densidad relativa del 60%. Las muestras fueron sometidas a confinamientos isótropicos de 1, 2 y 4 kgf/cm2 y a una succión matricial de ua-uw = 0,02 kgf/cm2 y 0,2 kgf/cm2, constante durante la etapa de aplicación del esfuerzo desviatórico, cuya duración se estableció en 2 días y 12 hrs, para asegurar el drenaje de las presiones de poro. Los ensayos triaxiales en las muestras parcialmente saturadas de la arena de relave, arrojaron resistencias mayores a las determinadas en las muestras saturadas. Como consecuencia, se puede anticipar que evaluar el comportamiento geomecánico de suelos con saturación parcial, puede resultar favorable para el diseño de tranques de relave.

Submitted by Reginaldo Soares de Freitas (reginaldo.freitas@ufv.br) on 2017-03-03T12:58:53Z No. of bitstreams: 1 texto completo.pdf: 996624 bytes, checksum: a10ac3a4608db49339a45a661abbe900 (MD5) / Made available in DSpace on 2017-03-03T12:58:53Z (GMT). No. of bitstreams: 1 texto completo.pdf: 996624 bytes, checksum: a10ac3a4608db49339a45a661abbe900 (MD5) Previous issue date: 2004-02-18 / Fundação de Amparo à Pesquisa do Estado de Minas Gerais / Este trabalho teve como objetivo avaliar o comportamento resiliente de dois solos típicos do subleito de rodovias da Zona da Mata Mineira, procurando estabelecer correlações entre os parâmetros denominados módulo resiliente e resistência à compressão não confinada. Dentre os materiais estudados, um faz parte do grupo dos solos saprolíticos e o outro dos podzólicos. Foram realizados ensaios de compactação, compressão não confinada e triaxiais de carregamento repetido. Considerou-se nesta pesquisa as energias dos ensaios de compactação Proctor Normal, Proctor Intermediário e uma energia média entre estas denominada Inter-Intermediária. Os teores de umidade para moldagem dos corpos-de-prova foram: W ot – 3%, W ot – 2%, W ot, Wot + 2%. Trabalhou-se com as normas AASHTO T 307-99 e DNER-ME 131/94, referentes à realização de ensaios triaxiais dinâmicos para determinação do módulo resiliente dos solos. Através do trabalho desenvolvido foi possível avaliar: (i) a influência da energia de compactação e do teor de umidade no módulo resiliente dos solos; (ii) o comportamento do módulo resiliente dos solos estudados obtidos através de procedimentos diferenciados. A partir dos resultados obtidos concluiu-se que: (i) as condições de compactação foram fatores determinantes na resposta resiliente dos solos finos analisados. Quanto às correlações desenvolvidas, os melhores resultados foram obtidos para corpos-de-prova compactados no teor ótimo e no ramo seco da curva de compactação; (ii) o aumento da energia de compactação não resultou, necessariamente, em aumentos no valor do módulo resiliente; (iii) com relação ao estado de tensão, o emprego do modelo composto resultou em maiores coeficientes de determinação; (iv) a variação do módulo resiliente, segundo as metodologias utilizadas na condução dos ensaios triaxiais de carregamento repetido, refletiu os diferentes níveis de tensão adotados nas mesmas; (v) a inclusão das deformações resilientes nos modelos que consideravam apenas os resultados dos ensaios triaxiais de carregamento repetido fez com que os mesmos apresentassem melhores ajustes aos resultados; (vi) os modelos que consideravam, além dos resultados dos ensaios de compressão não confinada, o estado de tensão e as deformações resilientes levaram, em geral, a coeficientes de determinação significativos. / This thesis was directed to the evaluation of the resilient behavior of two typical sub-grade soils from the “Zona da Mata Mineira” in order to establish correlations between resilient modulus and geotechnical parameters determined in unconfined compression strength tests. The materials analyzed encompassed a saprolite soil and a podzol soil. The laboratory testing program included the following tests: compaction, unconfined compression and repeated load triaxial. Compaction tests were performed at the Standard (12 blows) and Intermediate (26 blows) Proctor compaction efforts, as well as at an inter-intermediate (18 blows) compaction effort. Specimens were prepared at the following water contents: (W ot – 3%), (W ot – 2%), (W ot) and (W ot + 2%). The repeated load triaxial tests were carried out under the following Standards: AASHTO T 307-99 e DNER-ME 131/94. The following analysis were accomplished in the study: (i) influence of compaction effort and water content on the resilient modulus of soils; (ii) influence of two different Standards on resilient modulus of soils; (iii) statistical significance of relating resilient modulus and unconfined compression strength tests geotechnical parameters of soils. The laboratory testing data supported the following conclusions: (i) compaction parameters determined the resilient response of the tested fine-grained soils. Regarding water content, best results were related to compaction at the dry side of the compaction curve, and at the optimum moisture content; (ii) increases in the compaction effort were not related, necessarily, to increases in the soils resilient modulus; (iii) regarding the stress state parameter, the composed model gave best coefficients of simple determination; (iv) the resilient modulus variation reflected the stress levels adopted in the testing methodologies used in the triaxial repeated loading tests; (v) regarding only the repeated loading triaxial testing data, inclusion of resilient deformations in the models led to better fittings; (vi) besides unconfined compression testing data, models associated to stress state and resilient deformations led to significant coefficients of simple determination.

The stability of the Niagara Escarpment is of critical importance to residents of Hamilton, Ontario as it bisects and divides the lower downtown core from upper residential and commercial areas. The frequency of large rockfalls and debris slides from the exposed escarpment face has resulted in reoccurring road closures that connect these two areas and has prompted the city to seek information on the processes affecting escarpment erosion and slope stability. The research reported here examines the relationship between tree and plant growth on bedrock stability by investigating relationships between species abundance and slope profile, and the potential movement of tree roots growing in rock fractures. The contributing factors of tree growth to physical weathering processes on highly fractured bedrock remain largely unknown; however, plants are suggested to play a key role in weathering processes in the critical zone. Bedrock structure and lithology influence the establishment of vegetation, and vegetation in turn exploits bedrock joints, fractures, and bedding planes, exacerbating physical and biomechanical weathering processes. In this study, vegetation characteristics observed on different parts of the escarpment face were documented and categorized into three distinct biophysical zones: upper and intermediary plateau, bedrock face, and sloping talus. Tree growth, with the potential to enhance bedrock disaggregation through the transfer of tree bole movement to roots exploiting bedrock fractures, was particularly prevalent on areas of sloping talus. To document the potential for bedrock disaggregation through tree bole movement, triaxial accelerometers were mounted on the boles of three different tree species growing along the escarpment in Hamilton. Sampled trees varied in geographic location to allow identification of the relationship between tree bole movement, wind speed, and dominant wind direction. Both deciduous and coniferous species were monitored to determine the impacts of canopy architecture on tree sway in response to wind. Monitoring took place over several days in the months of March, May, September, and November. Recorded tree bole movement (tilt) varied between deciduous and coniferous tree species; wind speed was strongly correlated to tilt of the coniferous tree, and wind direction was strongly correlated to tilt of the deciduous trees. Overall tree bole movement was strongly influenced by diurnal cycles of air movement and was greatest in the hours around mid-day. The outcomes of this research will form an integral component of an erosion-risk assessment study conducted, in part, for the City of Hamilton and will facilitate the design and development of vegetation management strategies for the Niagara Escarpment that may reduce erosion processes and potential damages to impacted citizens and businesses. / Thesis / Master of Science (MSc) / This research examines the impact of vegetation growth on erosion processes on the Niagara Escarpment in Hamilton, Ontario. The slope of the escarpment face exerts an important control on vegetation growth which in turn affects slope stability. Documentation of the dominant vegetation species at two research sites allows the identification of three distinct vegetation zones on the upper plateau, bedrock face, and sloping talus. The movement of tree trunks in response to air movement was also measured for several days in the months of March, May, October and November. Results show that the movement of two monitored deciduous trees was most strongly correlated to wind direction, while the movement of a coniferous tree was strongly correlated to changes in wind speed. All monitored trees were strongly influenced by daily cycles of air movement which were greatest around noon. This research identifies factors that influence both vegetation growth and slope stability on the Niagara Escarpment and may be used to develop effective erosion protection and mitigation strategies.

The purpose of this study was to analyze the anisotropic behaviour of layered soil at small strain level. This thesis comprised experimental, numerical, and theoretical aspects and provided an insight to the concept of the ‘equivalent’ homogeneous cross-anisotropic material indicating that the layered soil can be replaced by an equivalent transversely isotropic material under certain conditions. In the experimental program, this study extended Vaid’s work (1971) to conduct K0-compression tests in a rigid triaxial cell with a flexible lateral boundary for the determination of the K0-value of normally consolidated soil. The error induced by the compliance of the cell-water system that always existed in the previous study was successively eliminated by attaching a compliance correction system (i.e., GDS controller) to the triaxial cell. Three stress path tests (i.e., the K0-compression test, the plane strain compression test, and the hydrostatic pressure compression test) were conducted consecutively in a rigid triaxial cell for a layered soil specimen to determine the elastic cross-anisotropic properties of the equivalent homogeneous material. The applicability of the proposed approach was demonstrated by conducting the tests on two types of soil (i.e., the homogeneous soil and the layered soil). A three-parameter constitutive equation for describing the soil’s cross-anisotropic elastic behaviour was modified in a basic FEM program. Based on the material properties determined by the experimental study as an input, numerical simulations (i.e., the numerical K0-test) using FEM were conducted to compare numerical results with the test results. In the theoretical part, this study made use of the Reuss and the Voigt approximations and proposed a simple, yet physically meaningful, approach to determine the equivalent cross-anisotropic elastic properties of a multilayered medium. To simplify the exposition, a multilayered medium with two constituent materials that were both isotropic was examined. / Thesis / Master of Applied Science (MASc)

Em muitas partes do mundo, engenheiros geotécnicos freqüentemente lidam com solos não saturados, e o desempenho de obras nestes solos depende de suas características mecânicas, como a resistência ao cisalhamento. A determinação experimental da resistência de solos não saturados pode ser feita em laboratório utilizando técnicas que permitem controle ou medida da sucção, sendo uma delas o ensaio de compressão triaxial com teor de umidade constante. Neste contexto, essa pesquisa analisa a resistência ao cisalhamento de um solo arenoso compactado não saturado por meio de ensaios de compressão triaxial. Ensaios do tipo adensado-drenado e adensado-não drenado foram realizados com solo saturado, enquanto ensaios com teor de umidade constante foram realizados para caracterizar o comportamento do solo não saturado. Os resultados dos ensaios com solo saturado foram combinados e forneceram uma envoltória de resistência comum em termos de tensões efetivas. Para o solo não saturado, as curvas tensão-deformação foram representadas pela diferença de tensões principais e por esta normalizada por algumas das variáveis de estado de tensão do solo. Tais curvas se assemelham a curvas típicas de um material plástico, com exceção das obtidas para a menor tensão confinante, nas quais se observou a ocorrência de picos de resistência. Já a sucção apresentou um comportamento comum a todos os ensaios, com redução inicial seguida de estabilização. As diferentes representações da curva tensão-deformação permitiram definir superfícies planares de resistência no espaço tensão x sucção x resistência, nas quais foram observadas pequenas variações nos valores de coesão efetiva e ângulo de atrito com relação à sucção. Apesar do bom ajuste destas envoltórias planares, os resultados mostraram alguma não-linearidade. Por fim, testaram-se os métodos de Khalili e Khabbaz (1998) e Vilar (2007) de previsão da resistência ao cisalhamento de solos não saturados. / In many parts of the world, geotechnical engineers frequently deal with unsaturated soils, and the performance of constructions on such soils depends on their mechanical characteristics, and among them, the shear strength. The unsaturated soil shear strength can be experimentally determined by using techniques which allow soil suction control or measurement and one of the available techniques is the constant water content triaxial compression test. In this context, this research analyzes the shear strength of an unsaturated compacted sandy soil using triaxial compression tests. Consolidated-drained and consolidated-undrained triaxial compression tests were performed with the saturated soil, while constant water content triaxial compression tests were performed to characterize the unsaturated soil behavior. Results of tests with saturated soil were gathered and yielded a common shear strength envelope in terms of effective stress. Regarding the unsaturated soil, the stress-strain curves were represented by the deviator stress and the deviator stress normalized by some stress state variables of the soil. Such curves were similar to typical curves of a plastic material, except for those obtained for the lower confining pressure, in which peak of stress were observed. Suction development during shearing presented a common behavior to all the tests, with initial reduction followed by stabilization. The different representations of stress-strain curves allowed defining shear strength planar surfaces on stress x suction x strength space, which showed small variations of effective cohesion and angle related to suction. Despite of the good adjustment of these planar shear strength envelopes, the results showed some non-linearity. Finally, the methods proposed by Khalili and Khabbaz (1998) and Vilar (2007) for predicting the shear strength of unsaturated soils were tested.

El proyecto de investigación tuvo por finalidad evaluar las geomallas triaxiales, como elementos de refuerzo en la interfaz Subrasante – Subbase de la estructura del pavimento flexible, con el objetivo de optimizar espesores del pavimento, aumentar la capacidad de soporte de la subrasante y prolongar la vida útil de pavimento. En este trabajo se presenta la aplicación de una metodología de diseño para el uso de geomallas triaxiales, con las especificaciones técnicas para el diseño aplicado de las geomallas en pavimentos flexibles en Perú. La metodología de diseño está centrada en las investigaciones del doctor J.P. Giroud y el doctor Jie Han, que presentan un efecto de confinamiento generado, entre las geomallas y la capa de material sobre la subrasante. Los suelos al ser sometidos a cargas de llantas tienden a deformarse, generando ahuellamiento sobre la superficie de rodadura. Con la presencia de geomallas en el suelo este ahuellamiento se reduce de manera exponencial (Giroud & Han, 2005). Para la metodología planteada se desarrolla un ejemplo aplicativo para el diseño reforzado, de una base pavimentada, con geomalla triaxial y otro sin refuerzo. Para este ejemplo se recolecto datos con ayuda de los formatos de clasificación vehicular del MTC, inspección visual de la vía para la evaluación del índice de condición del pavimento (PCI) y los ensayos de laboratorio; la cual fue ejecutada a lo largo de los 2.3 km aproximadamente, en el cual se observó que el PCI del tramo es de 21%, esto significa que el nivel de servicio de la vía es malo, es decir requiere la intervención inmediata. Mediante esta metodología el uso de geomallas implicó disminución de espesores de 33.33%, cabe recalcar que se debe tener en cuenta que cada diseño variará de acuerdo con el proyecto a ejecutarse, por ende, dependerá de las características del suelo, el tráfico vehicular y el refuerzo (Tipo de geomalla) utilizado. / The purpose of this research project was to evaluate the triaxial geogrids, as reinforcement elements in the Subgrade - Subbase interface of the flexible pavement structure, with the aim of optimizing pavement thicknesses, increasing the support capacity of the subgrade and prolonging the useful life of pavement. This paper presents the application of a design methodology for the use of triaxial geogrids, with the technical specifications for the applied design of geogrids inflexible pavements in Peru. The design methodology is focused on the investigations of Dr. J.P. Giroud and Dr. Jie Han, who present a generated confinement effect, between the geogrids and the layer of material on the subgrade. The floors when subjected to tire loads tend to deform, generating rutting on the running surface. With the presence of geogrids in the ground, this rutting is reduced exponentially (Giroud & Han, 2005). For the proposed methodology an application example is developed for the reinforced design, of a paved base, with triaxial geogrid and another without reinforcement. For this example, data was collected with the aid of the vehicle classification formats of the MTC, visual inspection of the road for the evaluation of the pavement condition index (PCI) and laboratory tests; which was executed along the approximately 2.3 km, in which it was observed that the PCI of the section is 21%, this means that the service level of the road is bad, that is, it requires immediate intervention. Through this methodology the use of geogrids implied a decrease in thickness of 33.33%, it should be noted that it must be taken into account that each design will vary according to the project to be executed, therefore, it will depend on the characteristics of the soil, vehicular traffic and reinforcement (Type of geogrid) used. / Trabajo de investigación

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. / A thorough experimental analysis with a micro macro approach was performed on a material composed ofa mixture of Kaolinite / Smectite clays. The study showed at macroscopic scale as the microscopic scalethat the behaviour is particularly sensitive to the proportion of smectite in the mixture. Kaolinite(Kaolinite P300) is well known from the point of view of characterization and behaviour, smectite (also called Greek clay) is a calcic type and was also the subject of several studies.From 35% of smectite in the mixture, the results show that the behaviour on triaxial path approachconsiderably to that of smectite. Furthermore, investigation on the microscopic level (using scanningelectron microscope supplemented by X‐ray diffraction analysis) performed on the samples after the testshows that, if it exceeds a certain threshold, the smectite fraction promotes the development of slipplanes. These plans are evident as oriented groups of particles of smectite.The used microstructural analysis is based on a rigorous method, developed in the context of this thesis,with an automated image processing to provide quantitative results.This multi‐scale investigation has been used to characterize the behaviour of a marine sediment taken ofGulf of Guinea by 700 m water depth. The study, originally conducted in the CLAROM project (2002‐2005), interested to the offshore industry. The natural sediment contains up to 60% proportion of claywith approximately 15% smectite and 50% kaolinite.

Em muitas partes do mundo, engenheiros geotécnicos freqüentemente lidam com solos não saturados, e o desempenho de obras nestes solos depende de suas características mecânicas, como a resistência ao cisalhamento. A determinação experimental da resistência de solos não saturados pode ser feita em laboratório utilizando técnicas que permitem controle ou medida da sucção, sendo uma delas o ensaio de compressão triaxial com teor de umidade constante. Neste contexto, essa pesquisa analisa a resistência ao cisalhamento de um solo arenoso compactado não saturado por meio de ensaios de compressão triaxial. Ensaios do tipo adensado-drenado e adensado-não drenado foram realizados com solo saturado, enquanto ensaios com teor de umidade constante foram realizados para caracterizar o comportamento do solo não saturado. Os resultados dos ensaios com solo saturado foram combinados e forneceram uma envoltória de resistência comum em termos de tensões efetivas. Para o solo não saturado, as curvas tensão-deformação foram representadas pela diferença de tensões principais e por esta normalizada por algumas das variáveis de estado de tensão do solo. Tais curvas se assemelham a curvas típicas de um material plástico, com exceção das obtidas para a menor tensão confinante, nas quais se observou a ocorrência de picos de resistência. Já a sucção apresentou um comportamento comum a todos os ensaios, com redução inicial seguida de estabilização. As diferentes representações da curva tensão-deformação permitiram definir superfícies planares de resistência no espaço tensão x sucção x resistência, nas quais foram observadas pequenas variações nos valores de coesão efetiva e ângulo de atrito com relação à sucção. Apesar do bom ajuste destas envoltórias planares, os resultados mostraram alguma não-linearidade. Por fim, testaram-se os métodos de Khalili e Khabbaz (1998) e Vilar (2007) de previsão da resistência ao cisalhamento de solos não saturados. / In many parts of the world, geotechnical engineers frequently deal with unsaturated soils, and the performance of constructions on such soils depends on their mechanical characteristics, and among them, the shear strength. The unsaturated soil shear strength can be experimentally determined by using techniques which allow soil suction control or measurement and one of the available techniques is the constant water content triaxial compression test. In this context, this research analyzes the shear strength of an unsaturated compacted sandy soil using triaxial compression tests. Consolidated-drained and consolidated-undrained triaxial compression tests were performed with the saturated soil, while constant water content triaxial compression tests were performed to characterize the unsaturated soil behavior. Results of tests with saturated soil were gathered and yielded a common shear strength envelope in terms of effective stress. Regarding the unsaturated soil, the stress-strain curves were represented by the deviator stress and the deviator stress normalized by some stress state variables of the soil. Such curves were similar to typical curves of a plastic material, except for those obtained for the lower confining pressure, in which peak of stress were observed. Suction development during shearing presented a common behavior to all the tests, with initial reduction followed by stabilization. The different representations of stress-strain curves allowed defining shear strength planar surfaces on stress x suction x strength space, which showed small variations of effective cohesion and angle related to suction. Despite of the good adjustment of these planar shear strength envelopes, the results showed some non-linearity. Finally, the methods proposed by Khalili and Khabbaz (1998) and Vilar (2007) for predicting the shear strength of unsaturated soils were tested.

[pt] Os maciços rochosos encontram-se submetidos a estados biaxiais e triaxiais de tensão. O conhecimento da deformabilidade e da resistência das rochas sob tais condições é fundamental para o cálculo da capacidade de suporte de fundações em rochas, projeto de barragens, mineração, prospecção e extração de petróleo, construção de túneis, etc. Para tanto, a realização de ensaios, quer sejam de campo ou de laboratório, é de grande valia. Devido à dificuldade de realização de ensaios biaxiais, e sendo a solicitação triaxial a mais comum, é bastante pertinente o estudo do comportamento das rochas quando submetidas a tal carregamento. O objetivo do presente trabalho é o desenvolvimento de uma célula triaxial para ensaios de laboratório em rochas, capaz de suportar uma pressão confinante de até 70 MPa. O equipamento permite instrumentação interna dos corpos de prova. Foi prevista a obtenção de medidas de poropressão, tanto de topo quanto de base, e a possibilidade de percolação de fluido pelo espécime ensaiado. A fim de se caracterizar o equipamento, foram executados ensaios em espécimes de aço e rocha. A rocha estudada foi um gnaisse leptinito encontrado no município do Rio de Janeiro (Morro Dona Marta). / [en] Rock masses are submitted to biaxial and triaxial states of stress. Deformability and strength properties of rocks under such conditions are essential data for calculating bearing capacity of foundations, design of dams, mining excavations, oil exploration, tunnelling etc. For these purposes, laboratory and in situ tests are of great importance. Studying rock behaviour when submitted to triaxial loading is of great concern, due to the difficulty in carrying out biaxial tests and because triaxial state of stress is more common. This thesis presents the design and construction of a triaxial cell for laboratory tests in rocks, which is able to support a confining pressure as high as 70 MPa. The equipment allows internal specimen instrumentation. Top and bottom pore-pressure measurements have been predicted, and fluid percolation through the specimen is possible. Tests on steel and rock specimens were carried out to comission the equipment. The rock tested is a leptinite gneiss found in the city of Rio de Janeiro (Morro Dona Marta). / [es] Los macizos rocosos se encuentran sometidos a estados de tensión biaxiales y triaxiales. El conocimiento de la deformabilidad y de la resistencia de las rocas bajo tales condiciones es fundamental para el cálculo de la capacidad de soporte de fundaciones en rocas, proyecto de presas, mineración, prospección y extracción de petróleo, construcción de túneles, etc. De aqui la importancia de la realización de ensayos, ya sean de campo o de laboratorio. Considerando la dificuldad para la ejecución de ensayos biaxiales, y como la solicitación triaxial es la más común, resulta pertinente el estudio del comportamiento de las rocas cuando son sometidas a tal carga. EL objetivo del presente trabajo es el desarrollo de una célula triaxial para ensayos de laboratorio en rocas, capaz de soportar una presión de confinación de hasta 70 MPa. El equipo permite la instrumentación interna de los cuerpos de prueba. Fue previsto obtener medidas de poropresión, tanto de pico cuanto de base, y la posibilidad de percolación de fluido por el espécimen ensayado. Con el objetivo de caracterizar el equipo, se ejecutaron ensayos en espécimes de acero y roca. La roca estudada fue un gnaise leptinito encontrado en el município del Rio de Janeiro (Morro Dona Marta).