The objectives of this dissertation are to measure and calculate surface free energies of soil particles, to understand the mechanical behavior of unsaturated silty sand through first studying the stress-strain relationship, the effects of matric suction and pore water chemistry and second to interpret the behavior by the critical state frame work, to develop a method to predict cone tip resistance in unsaturated soils, and to present the concept of pseudo strain and dissipated pseudo strain energy. Universal Sorption Device (USD) is developed to measure surface free energies of soil particles. The test results on a soil sample shows that specific surface area increased with decreasing particle size. The components of surface free energies and the work of adhesion increased with decreasing particle size. A servo controlled triaxial testing device is developed to test 15.24 cm in height and 7.62 cm in diameter, recompacted specimens of unsaturated soil under varying matric suction and different pore chemistry. During the test, the matric suction is maintained constant. Results from the triaxial drained tests are used for validation of the constitutive models proposed by Alonso et al. (1990). Predictions from the model are in good agreement with experimental results. The critical state model for unsaturated soil is used to calculate cone tip resistance in unsaturated silty sand. The calculated cone tip resistance is used to evaluate the liquefaction potential of unsaturated soils. The results from the stress based liquefaction potential analysis reveal that even in an unsaturated condition soil is susceptible to liquefaction. By applying the pseudo strain concept, it is possible to account for the viscous resistance of water during cyclic loading. The results of undrained cyclic triaxial tests are used to calculate pseudo-strain and dissipated pseudo strain energy. The results of calculated dissipated pseudo strain energy suggest that the effect of initial matric suction is evident. On the other hand, the effect of surface tension increase or decrease due to existence of chemical on the pore water is negligible.

The behavior of unsaturated soils depends heavily on material properties and soil conditions. In Geotechnical Engineering, compacted soils are frequently used as fill material, and quality control is vital to the construction process. There are few methods available to estimate the parameters associated with unsaturated soils based on field measurements, and a relationship between these factors could reduce testing time and lower construction costs. Undrained triaxial tests were performed on four clays representing a range of material properties in an effort to reach the maximum dry density, which provides the highest bearing capacity. Each clay was compacted at optimum moisture content, as well as wet and dry of optimum. Measurements were taken using the GeoGauge and shear wave velocities. An empirical approach was used to estimate the effect of a density gradient on soil suction. A relationship between the normal stress and matric suction produced a strong trend when plotted against a function of stiffness and the void ratio, which represents a density gradient. Another relationship between the GeoGauge and shear wave stiffness measurements was found, but no relationship with the material properties of the samples was observed, indicating that more in-depth research is needed to find a stronger relationship.

Between 2004 and early 2006 a large-scale, instrumented, potentially contaminating trial waste rock dump was constructed and monitored at Cadia Hill Mine, in NSW, Australia. The trial waste rock dump was instrumented with lysimeters to measure rainfall infiltration and seepage through its base, and temperature sensors and gas sampling tubes to evaluate oxidation of the waste rock, together with three instrumented trial store and release covers on the surface. This thesis describes the construction and instrumentation of the trial waste rock dump and the monitoring results obtained to date, and applies unsaturated soil mechanics principles to understanding the early performance and predicting the future performance of the trial waste rock dump and trial store and release covers. For a given rainfall regime, the rate and quantity of rainfall infiltration into a waste rock dump of a given height, the wetting up of the dump over time, and the occurrence of base seepage will largely be dictated by the particle size distribution of the waste rock delivered to the dump, and the stratigraphy of the dump. The particle size distribution of the waste rock delivered to the dump will depend on the fragmentation of the rock due to blasting and the degree of weathering and hence breakdown on handling of the rock. A waste rock dump constructed by conventional loose end-dumping from haul trucks from a tip-head, as was the case for the trial waste rock dump, consists of a trafficked surface layer extending to a depth of approximately 1 m, underlain by discontinuous alternating coarse and fine-grained layers raveling at the angle of repose of the waste rock, with a base rubble zone of boulders which ravel to the toe of the dump on end-dumping. Trafficking of the surface of the dump by dozers and haul trucks leads to the breaking down, burial and side-casting of the rock to form a well-graded material typically finer than 100 mm in particle size, with a moderate to high water storage capacity. The underlying coarse-grained angle of repose layers serve as air pathways during dry conditions and preferred seepage pathways during and following periods of heavy rainfall resulting in base seepage. The fine-grained angle of repose layers have a moderate to high water storage capacity and largely retain water in storage rather than generating base seepage. The base rubble zone may contain boulders up to 1 m in size, depending on the fragmentation of the rock due to blasting and the degree of weathering and hence breakdown on handling of the rock. It serves largely as a pathway for air during dry conditions, while passing base seepage during and following periods of heavy rainfall. As the dump wets up, partially saturated “fingers” develop and extend into the dump. Partially saturated fine-grained layers, having a medium to high water storage capacity, largely retain their partial saturation, while coarse-grained layers drain resulting, in base seepage. Plugs of water temporarily stored within the dump drain down through the dump, so that the base seepage that emerges is “old” water, not the rainfall infiltration (“new” water) that generated it. The size of the rainfall event required to generate base seepage will decrease as the dump wets up and the partially saturated fingers extend closer to the base of the dump. The residence time of water within the dump that passes along preferred seepage pathways will be relatively short and will become shorter as the dump wets up, while the residence time of water stored within the fine-grained layers will be very long, and possibly indefinite in a dry climate. The ingress of air through the base rubble zone, up the coarse-grained angle of repose layers, through the sides of the dump, and to a lesser extent through the trafficked layer, by the processes of convection, advection and diffusion, respectively, results in the exposure of reactive waste rock to oxidation. The fine-grained reactive waste rock, presenting a far greater surface area per unit volume than the coarse-grained waste rock, and typically having a greater proportion of fresh surfaces, is by far the most reactive. The ingress of air into the fine-grained layers is largely by diffusion from the adjacent coarse-grained layers. The transport of oxidation products from the dump largely occurs during and following periods of heavy rainfall, when preferred pathway flow is mobilised and base seepage occurs. The main exposure to preferred pathway flow is along these pathways, where the surface area per unit volume and hence the proportion of oxidation products are low, with much of the oxidation products formed on the fine-grained particles retained within the dump along with stored water. Due to the discontinuous stratigraphy of a waste rock dump, the preferential pathways for flow are randomly located within the dump. In addition, preferential pathways evolve over time as the waste rock weathers, settles, and as fines are transported with the flow. The trafficked surface of the dump also evolves over time, becoming more heterogeneous as the surface settles differentially, generating internal rainfall runoff and the transport of fines, and the development of “sinkholes” for the preferred entry of ponded rainfall. The principle purpose of cover systems over waste rock dumps is to restrict net percolation into the dump, so that percolation through the reactive waste rock is minimal in the longer term. The approach used to design any cover system is dominated by climate. Semi-arid environments are conducive to store and release cover systems which take advantage of well-graded oxide materials to provide high storage capacities, low percolation and stability. Three trial store and release covers, each comprising a sealing layer overlain by a thick mounded rocky soil mulch layer, were installed at Cadia Hill Mine in 2005-2006 to assess their feasibility to limit net percolation under the climatic conditions encountered at Cadia. This research described in this thesis has demonstrated a number of key issues that should be considered in the management and closure of waste rock dumps: • the initial moisture condition of the end-dumped waste rock will effect its early ability to store incidental rainfall; • the available water storage capacity of the waste rock will affect the size of the triggering rainfall event and the base seepage response time, with the storage capacity being taken up as the dump wets up, reducing both the size of the triggering rainfall event and the response time; • iterative modelling and calculations using HYDRUS-2D suggest that the trial waste rock dump will take between 3 years and 6 years to become sufficiently saturated that it will pass any rainfall infiltration, depending on the extent to which the waste rock weathers over time; and • all three trial store and release covers have demonstrated good performance over the monitoring period, and this has been verified using HYDRUS-2D, , with any net percolation being the result of an initial high placement moisture content of the cover materials.

To acquire deeper understanding and insights into the mechanical behaviour of fibre reinforced saturated/unsaturated cohesive soils, a programme of work was designed and included. 1) Conducting standard Consolidation Undrained (CU) tests to investigate mechanical behaviour of non-reinforced fully saturated soil. 2) Studying the strength of fibre reinforced clay though unconfined compression tests. 3) Testing the behaviour of unsaturated reinforced soil in unsaturated triaxial tests. 4) Determining the soil-water characteristic curves (SWCC) on soil sample with different fibre content. The investigation was undertaken on a clay of low plasticity index. Samples tested with addition of 1, 3 and 5 % fibre content and different values of matric suction of 50, 100 and 200 kPa, one of the challenges that were encountered in this research are how to prepare homogenous samples. A method for prepared compacted fibre reinforced soils with improved fibre distribution and density profile has been proposed and examined. The test results indicated that waste carpet fibres increase the shear strength of unsaturated clay soils. It was also found that relative increase in strength is also a function of applied suction. An increase in waste carpet fibres was found to reduce the hysteresis of soil. A data analysis conducted on the results of unsaturated tests as a function of fibre content and matric suction. The behaviour modelled was shown to be a perfect fit with the experimental data.

abstract: This study presents the results of one of the first attempts to characterize the pore water pressure response of soils subjected to traffic loading under saturated and unsaturated conditions. It is widely known that pore water pressure develops within the soil pores as a response to external stimulus. Also, it has been recognized that the development of pores water pressure contributes to the degradation of the resilient modulus of unbound materials. In the last decades several efforts have been directed to model the effect of air and water pore pressures upon resilient modulus. However, none of them consider dynamic variations in pressures but rather are based on equilibrium values corresponding to initial conditions. The measurement of this response is challenging especially in soils under unsaturated conditions. Models are needed not only to overcome testing limitations but also to understand the dynamic behavior of internal pore pressures that under critical conditions may even lead to failure. A testing program was conducted to characterize the pore water pressure response of a low plasticity fine clayey sand subjected to dynamic loading. The bulk stress, initial matric suction and dwelling time parameters were controlled and their effects were analyzed. The results were used to attempt models capable of predicting the accumulated excess pore pressure at any given time during the traffic loading and unloading phases. Important findings regarding the influence of the controlled variables challenge common beliefs. The accumulated excess pore water pressure was found to be higher for unsaturated soil specimens than for saturated soil specimens. The maximum pore water pressure always increased when the high bulk stress level was applied. Higher dwelling time was found to decelerate the accumulation of pore water pressure. In addition, it was found that the higher the dwelling time, the lower the maximum pore water pressure. It was concluded that upon further research, the proposed models may become a powerful tool not only to overcome testing limitations but also to enhance current design practices and to prevent soil failure due to excessive development of pore water pressure. / Dissertation/Thesis / Ph.D. Civil and Environmental Engineering 2011

Para a determinação do comportamento de um solo não saturado, é necessária a identificação da sua curva característica, que representa a capacidade de armazenamento de água pelo solo em função do valor de sucção imposto. Quando este solo é submetido a algum processo de contaminação, a sua estrutura interna pode ser alterada por processos físico-químicos, modificando, por conseqüência, o seu comportamento. Esta dissertação propõe uma metodologia de ensaio para a determinação de curvas características de sucção total em um solo artificialmente contaminado com diferentes teores de óleo diesel. O programa experimental proposto consiste basicamente na realização do método do papel filtro, através da técnica sem contato entre a amostra e o papel, com algumas modificações em relação às metodologias anteriormente descritas na literatura geotécnica. Foram também executados ensaios para controle e quantificação da evaporação do contaminante ao longo do tempo, e sua possível absorção pelo papel filtro utilizado. Além disso, foram realizados ensaios para a caracterização física, mineralógica e química do solo, antes e após a adição do óleo, com o intuito de constatar as alterações causadas pela contaminação. O material estudado é constituído por sedimentos coluvionares provenientes de arenito da Formação Botucatu, sendo que sua curva característica, sem contaminação, já foi determinada em um estudo anterior, através do método do papel filtro com contato. Para possibilitar comparações entre estes resultados, foram medidos também alguns pontos em amostras não contaminadas, através da técnica proposta nesta dissertação. Estes apresentaram uma satisfatória concordância em relação à curva anteriormente ajustada. Na análise das curvas características do solo contaminado com 2%, 5%, 10% e 15% de óleo diesel, constatou-se a permanência do formato bimodal, sugerindo que a microestrutura e a macroestrutura continuam influenciando na entrada e saída de água do meio. Entretanto, foram identificadas alterações na forma da curva e na extensão dos patamares resultantes, em relação à curva característica sem contaminação, assim como as diferentes localizações dos valores de entrada de ar. Foi verificado que, conforme o aumento do teor de contaminante, há uma gradual tendência ao formato unimodal da curva característica, induzindo a um comportamento de solo tipicamente granular. Este fato foi comprovado nos resultados de microscopia eletrônica, onde se verifica que, com teores menores de óleo, a estrutura do solo encontra-se mais fechada e, à medida que este teor aumenta, a estrutura torna-se mais porosa. Os tempos de equalização para o método de ensaio proposto variaram entre 7 e 30 dias, conforme o nível de sucção da amostra. A avaliação da histerese revelou que, com o aumento do teor de contaminante, há uma pequena redução deste fenômeno. Além disso, os ensaios complementares comprovaram a existência de uma pequena porcentagem de evaporação do óleo diesel, assim como a absorção do mesmo pelo papel filtro, que se apresentou praticamente nula. / The unsaturated soil behavior can be determined through its soil-water characteristic curve, which represents the capacity of the soil to store water when submitted to different suction levels. When this soil is contaminated, its internal structure can be modified according to physical and chemical processes, thus changing the initial behavior. This dissertation proposes a test methodology to determine the total-suction soil-water characteristic curves of a contaminated soil at different diesel oil contents. The experimental program consisted of using the filter-paper method without contact between the sample and the paper, but with some modifications in relation to previously studied techniques. Some control tests were also carried out to check oil evaporation and its absortion by the filter paper. Besides, the samples were submitted to physical, mineralogical and chemical characterization, before and after contamination, to verify the possible changes. The studied material is a colluvium soil, constituted basically by sandstone, from the Botucatu Formation. This soil was previously studied by the filter-paper method with contact, and its soil water characteristic curve without contamination was already known. To compare the results, the proposed test methodology was also performed with non contaminated samples, showing a satisfactory agreement with the initial curve. The soil-water characteristic curves of this soil with a diesel oil content of 2%, 5%, 10% and 15% showed a "saddle" shape, indicating that both the microstructure and the macrostructure were influenced by the entrance and exit of water through the soil. However, the shape of the curve and the extent of its plateau changed according to the level of contamination. Increasing the oil content, the curve tends to a unimodal shape, with a behavior similar to granular soils. This statement was proved by the microstruture photographs, which showed an increase of sample porosity due to the increase of oil content. The time required to reach suction equilibrium during the tests varied between 7 to 30 days, according to the initial water content of the samples. The observed hysteresis had a small reduction with the increase of oil content. The control tests proved that oil evaporation and its absortion by the filter paper were insignificant in the whole test program.

Submitted by Amanda Leoncini Carvalho Barros (amanda_leoncini@yahoo.com.br) on 2018-11-09T16:08:38Z No. of bitstreams: 1 Dissertação Amanda Barros.pdf: 17724737 bytes, checksum: aea0eba26a241617041802312cfe28db (MD5) / Approved for entry into archive by Lucilene Cordeiro da Silva Messias null (lubiblio@bauru.unesp.br) on 2018-11-09T16:42:13Z (GMT) No. of bitstreams: 1 barros_alc_me_bauru.pdf: 17724737 bytes, checksum: aea0eba26a241617041802312cfe28db (MD5) / Made available in DSpace on 2018-11-09T16:42:13Z (GMT). No. of bitstreams: 1 barros_alc_me_bauru.pdf: 17724737 bytes, checksum: aea0eba26a241617041802312cfe28db (MD5) Previous issue date: 2018-09-05 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Países com clima tropical sofrem frequentemente com o fenômeno da erosão. Devido às condições climáticas, que variam entre longos períodos de seca e chuvas intensas, em conjunto com a ação antrópica, este fenômeno tem seu efeito acelerado e pode causar graves consequências para o meio ambiente. Apesar do grande número de trabalhos publicados sobre o fenômeno erosivo, pouco deles aborda esse assunto sobre uma perspectiva da Mecânica dos Solos Não Saturados, muito comum nas regiões de clima tropical. Esta dissertação apresenta uma caracterização hidromecânica de um solo não saturado coletado de uma microbacia da cidade de Bauru-SP afetada por um processo erosivo hídrico e, conjuntamente, avalia o mecanismo de erodibilidade ocorrido na área. Os parâmetros hidráulicos foram obtidos pelos de retenção da água no solo e permeabilidade. Os parâmetros mecânicos foram obtidos pelos ensaios de compressão triaxial e edométricos, ambos com sucção controlada. Os resultados desses ensaios mostraram a influência da sucção tanto nos parâmetros de resistência ao cisalhamento do solo quanto nos de compressibilidade. A avaliação do mecanismo de erodibilidade foi realizada com base nos resultados encontrados nos ensaios de compressão triaxial e Inderbitzen, sendo esse último disponível no histórico de informações da microbacia. Essa avaliação constatou que o aumento da sucção pode contribuir contra o efeito da erosão uma vez que interfere na sua resistência através do intercepto de coesão. Entretanto, caso haja uma chuva intensa na área, essa contribuição pode durar poucos minutos, pois a microbacia não possui um sistema de drenagem eficiente e a camada superficial se saturada rapidamente e, consequentemente, perde o intercepto de coesão que estava disponível antes da chuva. O trabalho realizado evidencia um severo processo erosivo na microbacia Água Comprida e ainda permite um avanço nos estudos desse solo em termos do conceito da Mecânica dos Solos Não Saturados. / Countries with tropical climate often suffer from the erosion phenomenon. Due to the climatic conditions, which vary between long periods of drought and intense rains, together with the anthropic action, this phenomenon has its effect accelerated and can cause serious consequences for the environment. In spite of the great number of published works on the erosive phenomenon, few of them approach this subject on a perspective of the Mechanics of Unsaturated Soils, very common in the regions of tropical climate. This dissertation presents a hydromechanical characterization of an unsaturated soil collected from a microbasin of Bauru-SP city affected by an erosive water process and, together, evaluates the mechanism of erodibility occurred in the area. The hydraulic parameters were obtained by the soil-water retention and permeability. The mechanical parameters were obtained by triaxial and edometric compression tests, both with controlled suction. The results of these tests showed the influence of suction on both the shear strength and the compressibility parameters. The evaluation of the erodibility mechanism was carried out based on the results found in the triaxial and Inderbitzen tests, the latter being available in the history of the microbasin information. This evaluation found that increased suction may contribute to the erosion effect since it interferes with its resistance through the cohesion parameter. However, if there is heavy rainfall in the area, this contribution may last for a few minutes because the microbasin does not have an efficient drainage system and the surface layer is rapidly saturated and consequently loses the cohesion intercept that was available before the rain. The work carried out evidences a severe erosive process in the Água Comprida microbasin and still allows an advance in the studies of this soil in terms of the concept of the Mechanics of Unsaturated Soils.

Para a determinação do comportamento de um solo não saturado, é necessária a identificação da sua curva característica, que representa a capacidade de armazenamento de água pelo solo em função do valor de sucção imposto. Quando este solo é submetido a algum processo de contaminação, a sua estrutura interna pode ser alterada por processos físico-químicos, modificando, por conseqüência, o seu comportamento. Esta dissertação propõe uma metodologia de ensaio para a determinação de curvas características de sucção total em um solo artificialmente contaminado com diferentes teores de óleo diesel. O programa experimental proposto consiste basicamente na realização do método do papel filtro, através da técnica sem contato entre a amostra e o papel, com algumas modificações em relação às metodologias anteriormente descritas na literatura geotécnica. Foram também executados ensaios para controle e quantificação da evaporação do contaminante ao longo do tempo, e sua possível absorção pelo papel filtro utilizado. Além disso, foram realizados ensaios para a caracterização física, mineralógica e química do solo, antes e após a adição do óleo, com o intuito de constatar as alterações causadas pela contaminação. O material estudado é constituído por sedimentos coluvionares provenientes de arenito da Formação Botucatu, sendo que sua curva característica, sem contaminação, já foi determinada em um estudo anterior, através do método do papel filtro com contato. Para possibilitar comparações entre estes resultados, foram medidos também alguns pontos em amostras não contaminadas, através da técnica proposta nesta dissertação. Estes apresentaram uma satisfatória concordância em relação à curva anteriormente ajustada. Na análise das curvas características do solo contaminado com 2%, 5%, 10% e 15% de óleo diesel, constatou-se a permanência do formato bimodal, sugerindo que a microestrutura e a macroestrutura continuam influenciando na entrada e saída de água do meio. Entretanto, foram identificadas alterações na forma da curva e na extensão dos patamares resultantes, em relação à curva característica sem contaminação, assim como as diferentes localizações dos valores de entrada de ar. Foi verificado que, conforme o aumento do teor de contaminante, há uma gradual tendência ao formato unimodal da curva característica, induzindo a um comportamento de solo tipicamente granular. Este fato foi comprovado nos resultados de microscopia eletrônica, onde se verifica que, com teores menores de óleo, a estrutura do solo encontra-se mais fechada e, à medida que este teor aumenta, a estrutura torna-se mais porosa. Os tempos de equalização para o método de ensaio proposto variaram entre 7 e 30 dias, conforme o nível de sucção da amostra. A avaliação da histerese revelou que, com o aumento do teor de contaminante, há uma pequena redução deste fenômeno. Além disso, os ensaios complementares comprovaram a existência de uma pequena porcentagem de evaporação do óleo diesel, assim como a absorção do mesmo pelo papel filtro, que se apresentou praticamente nula. / The unsaturated soil behavior can be determined through its soil-water characteristic curve, which represents the capacity of the soil to store water when submitted to different suction levels. When this soil is contaminated, its internal structure can be modified according to physical and chemical processes, thus changing the initial behavior. This dissertation proposes a test methodology to determine the total-suction soil-water characteristic curves of a contaminated soil at different diesel oil contents. The experimental program consisted of using the filter-paper method without contact between the sample and the paper, but with some modifications in relation to previously studied techniques. Some control tests were also carried out to check oil evaporation and its absortion by the filter paper. Besides, the samples were submitted to physical, mineralogical and chemical characterization, before and after contamination, to verify the possible changes. The studied material is a colluvium soil, constituted basically by sandstone, from the Botucatu Formation. This soil was previously studied by the filter-paper method with contact, and its soil water characteristic curve without contamination was already known. To compare the results, the proposed test methodology was also performed with non contaminated samples, showing a satisfactory agreement with the initial curve. The soil-water characteristic curves of this soil with a diesel oil content of 2%, 5%, 10% and 15% showed a "saddle" shape, indicating that both the microstructure and the macrostructure were influenced by the entrance and exit of water through the soil. However, the shape of the curve and the extent of its plateau changed according to the level of contamination. Increasing the oil content, the curve tends to a unimodal shape, with a behavior similar to granular soils. This statement was proved by the microstruture photographs, which showed an increase of sample porosity due to the increase of oil content. The time required to reach suction equilibrium during the tests varied between 7 to 30 days, according to the initial water content of the samples. The observed hysteresis had a small reduction with the increase of oil content. The control tests proved that oil evaporation and its absortion by the filter paper were insignificant in the whole test program.

[pt] O estudo da ruptura de taludes em solos não saturados tem se tornado possível com o desenvolvimento de modelos que simplificam a elaboração da curva característica e estimam valores da resistência ao cisalhamento não saturada. Este trabalho utiliza dados de ensaios de campo e de laboratório para a realização de três simulações numéricas para o talude de corte localizado no Morro do Águia, em Salvador. O talude é de um perfil residual de solo siltoso oriundo de rocha metamórfica de gnaisse e migmatitos. A ruptura ocorreu aproximadamente dois anos após a execução de trabalhos de terraplenagem no período de construção da avenida Luís Eduardo Magalhães. A metodologia consistiu em levantar os dados disponíveis de ensaios realizados logo após a ruptura do talude, realizar ensaios complementares com o objetivo de obter dados de entrada para as simulações em três diferentes cenários. Foram realizados os seguintes ensaios: caracterização e análise mineralógica; curva de retenção; resistência ao cisalhamento por cisalhamento direto com as amostras inundadas, na umidade natural e com as amostras secas ar. Os cenários escolhidos para as simulações foram: análise de estabilidade considerando solo totalmente saturado em perfil de camada simples; análise de estabilidade acoplada com análise de fluxo com solo parcialmente saturado em camada simples e análise de estabilidade acoplada com análise de fluxo em solo parcialmente saturado em perfil de camada dupla. O estudo também estimou o ângulo (fi ao quadrado)b pela metodologia proposta por Vilar (2006). O resultado das simulações mostrou que o mecanismo de ruptura foi reproduzido quando se considerou o parâmetro não saturado (fi ao quadrado)b. O modelo simplificado, considerando o solo todo saturado, não reproduziu o mecanismo de ruptura. O (fi ao quadrado)b estimado pela metodologia de Vilar (2006) foi de 16 graus. O resultado das análises utilizando (fi ao quadrado)b = 16 graus não diferiu das análises utilizando (fi ao quadrado)b = 18 graus. O resultado das simulações mostrou que a ruptura ocorreu devido a infiltrações à montante do talude, em período de chuva de distribuição histórica atípica e período prolongado, que atingindo a profundidade do NA elevou a sua cota a zonas de instabilidade, causando a ruptura. / [en] The study of slope stability in unsaturated soils become possible with the development of models that simplify the construction of the characteristic curve and estimate values of unsaturated shear strength. This work presents the results of two stability analysis of a cut slope in Morro do Águia in Salvador, which had collapsed after construction of Luís Eduardo Magalhães Avenue. The slope is made of silty clay residual soil from metamorphic rocks originated by gneisses and migmatites. The methodology of analysis consists in collecting five undisturbed soil samples scattered in the area of study. Characterization and mineralogical analysis were performed; retention curve was constructed; and strength resistance by direct shear was determinate with samples in three conditions: flooded, in natural moisture and dried in air. The methodology of simplified estimation unsaturated shear strength (Vilar, 2006) was used to determinate (phi square)b. Computer simulations obtained from tests results were presented to three situations: first condition the safety factor was obtained considering stability analyses with saturated soil; second condition the soil was unsaturated and the groundwater flow consider rainwater during 86 days before rupture slope and afterwards was made the stability analysis; third condition the groundwater flow was modeled considering rainwater during 20 days afterwards was made the stability analysis. As a result of these analysis, the rupture mechanism that occurred at the time of the collapse is only reproduced by simulation when the parameter unsaturated (phi square)b is introduced, which occur at the second simulation. The value of (phi square)b obtained by Vilar methodology was 16 degrees.

abstract: Recent research efforts have been directed to improve the quality of pavement design procedures by considering the transient nature of soil properties due to environmental and aging effects on pavement performance. The main purpose of this research study was to investigate the existence of subgrade soil moisture changes that may have arisen due to thermal and hydraulic gradients at the Atlantic City NAPTF and to evaluate their effect on the material stiffness and the California Bearing Ratio (CBR) strength parameter of the clay subgrade materials. Laboratory data showed that at the same water content, matric suction decreases with increasing temperature; and at the same suction, hydraulic conductivity increases with increasing temperature. Models developed, together with moisture/temperature data collected from 30 sensors installed in the test facility, yielded a maximum variation of suction in field of 155 psi and changes in hydraulic conductivity from 2.9E-9 m/s at 100% saturation to 8.1E-12 at 93% saturation. The maximum variation in temperature was found to be 20.8oC at the shallower depth and decreased with depth; while a maximum variation in moisture content was found to be 3.7% for Dupont clay and 4.4% for County clay. Models developed that predicts CBR as a function of dry density and moisture content yielded a maximum variation of CBR of 2.4 for Dupont clay and 2.9 for County clay. Additionally, models were developed relating the temperature with the bulk stress and octahedral stress applied on the subgrade for dual gear, dual tandem and triple tandem gear types for different tire loads. It was found that as the temperature increases the stresses increase. A Modified Cary and Zapata model was used for predicting the resilient modulus(Mr) of the subgrade. Using the models developed and the temperature/moisture changes observed in the field, the variation of suction, bulk and octahedral stresses were estimated, along with the resilient modulus for three different gear types. Results indicated that changes in Mr as large as 9 ksi occur in the soils studied due to the combined effect of external loads and environmental condition changes. / Dissertation/Thesis / Doctoral Dissertation Civil, Environmental and Sustainable Engineering 2017