The master’s thesis deals with numerical patterns for evaluation of the stability slopes. Solutions have been made with finite element method for different design situations with using programme system ANSYS. The results were compared with conventional approaches determining of the slope safety factor.

The Carpathian foredeep is a lengthwise depressed area in the Carpathian foreland. In Moravia, it is mainly filled with Neogene soils. The thesis focuses on the South Moravian landslides which occurred in shallow relicts of Neogene deposits along a foredeep margin which lie on the rocks of the Bohemian Massif. Landslide activity within these shallow basins is a result of a number of factors. In the theoretical part, important general features of landslide areas, their geological conditions and hydrogeological regime are investigated. Next, available data on the geomechanical behaviour of soils, often connected with these landslides, are summarized and evaluated. The case studies deal with the landslide localities Budkovice-Svízla, Brno-Bystrc and Znojmo. The case study of Budkovice-Svízla is based on an extensive engineering geological survey of the locality and the measurement of groundwater levels in the years 1988 – 2017. In the thesis, the hydrogeological regime of the area is analysed and a reconstruction of the ground surface before slope movement is carried out. The probable trigger mechanisms, the development of sliding and the efficiency of the executed remedies of the landslide are evaluated by numerical studies. In conclusion, general recommendations for an engineering-geological survey and building activities in the area of interest are formulated.

付記する学位プログラム名: グローバル生存学大学院連携プログラム / 京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第20340号 / 工博第4277号 / 新制||工||1662(附属図書館) / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 寶 馨, 教授 角 哲也, 准教授 佐山 敬洋 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

The main goal of this research is to quantitatively assess the resilience and vulnerability of geotechnical infrastructure to extreme events under a changing climate. In the first part, pertinent facts and statistics regarding California’s extreme drought and current status of its levees are presented. Weakening processes such as soil strength reduction, soil desiccation cracking, land subsidence and surface erosion, and oxidation of soil organic carbon are comprehensively evaluated to illustrate the devastating impacts that the California drought can have on earthen structures. In the second part, rainfall-triggered slope instabilities are analyzed using extreme precipitation estimates, derived using the historical stationary and a proposed future nonstationary approach. The extremes are integrated into a series of fully coupled 2D finite element simulations. The final part of this study investigates the impact of simultaneous variations in soil moisture and temperature changes in the California region on soil strength through a proposed thermo-hydro-mechanical framework.

Several hydraulic loadings impose earthen levees to time-dependent variably saturated seepage conditions. The main objective of this study is to improve the analysis of levees under transient seepage with the use of unsaturated soil mechanics. An extensive set of laboratory testing, field monitoring and numerical modeling are performed to analyze a silty sand setback levee located near Seattle, WA. In-situ data obtained from field monitoring are used to monitor suction and effective stress within the levee’s embankment and foundation over the past two years. Soil samples taken from the site are used to perform index, water retention, and unsaturated multi-stage triaxial tests in the laboratory. A finite element model of transient seepage under saturated-unsaturated conditions is then developed and calibrated to reasonably match the field data. The results highlight the need to consider unsaturated soil mechanics along with climatic variables and soil-atmosphere interaction when analyzing levees under transient seepage conditions.

[pt] O objetivo deste trabalho é contribuir para um melhor entendimento do comportamento à força cortante de vigas de concreto armado sem e com fibras de aço via seus mecanismos resistentes. Para isto, foi feita ampla revisão do estado da arte e, com base nesta revisão, planejado o estudo experimental realizado. Este estudo contemplou quatro composições de concretos que visaram resistência à compressão em torno de 40MPa, variando-se o teor em volume (Vf = 0,0 por cento, 0,5 por cento ou 1,0 por cento) e o fator de forma das fibras (lf/df = 45 ou 80). Além dos ensaios de caracterização dos materiais, realizaram-se ensaios para estudo dos efeitos de pino e de engrenamento dos agregados, além de ensaios de vigas sem estribos com relação entre vão de cisalhamento e altura útil igual a 2,55. Constatou-se influência de Vf(lf/df) nos efeitos de pino e de engrenamento dos agregados, bem como no comportamento das vigas. O emprego da Correlação de Imagem Digital (CID) permitiu acompanhar a fissuração dos espécimes ensaiados e a obtenção de informações para a proposição de modelos teóricos para análise dos efeitos de pino e de engrenamento dos agregados. Os dados de fotogrametria obtidos nos ensaios das vigas permitiram avaliar a formação e a cinemática da fissura diagonal crítica e, com base nesses dados e nos modelos aqui propostos e em outros apresentados na literatura, buscou-se analisar a contribuição dos mecanismos resistentes em diferentes estágios de carregamento. Foi possível observar que vigas semelhantes podem apresentar posição, forma e cinemática da fissura crítica diferenciadas, embora com respostas globais próximas. Em decorrência disso, as contribuições dos mecanismos resistentes também resultam diferentes. / [en] The objective of this work is to contribute to a better understanding of the shear behavior of reinforced concrete beams without and with steel fibers via their resistant mechanisms. For this, a comprehensive review of the state of the art was made and, based on this review, the experimental study carried out was planned. This study contemplated four concrete compositions that aimed a concrete compressive strength around 40MPa, varying the volume content (Vf = 0.0 percent, 0.5 percent or 1.0 percent) and the aspect ratio of the fibers (lf /df = 45 or 80). In addition to the materials characterization tests, tests were carried out to study the dowel action and the aggregate interlock effects and also tests of beams without stirrups with span to effective depth ratio of 2.55. Influence of Vf(lf/df) in the dowel action and the aggregate interlock effects, as well as in the behavior of the beams was observed. The use of Digital Image Correlation (DIC) allowed monitoring the cracking of the tested specimens and to obtain information that led to theoretical models to analyze the dowel action and the aggregate interlock effects. The obtained photogrammetry data during the beams tests made it possible to follow the formation and kinematics of the critical diagonal crack and, based on these data and on the models proposed here and on others presented in the literature, the contribution of the resistant mechanisms in different loading stages was analyzed. It was possible to observe that similar beams may present differentiated position, shape and kinematics of the critical diagonal crack, although with similar global responses. As a result, the contributions of the resistant mechanisms are also different.

The box corer is a relatively new tool used in the geotechnical community for collection of soft seabed sediments. Miniature full flow and model pipeline probes were developed as tools to characterize and obtain soil parameters of soft seabed sediments collected in the box core for design of offshore pipelines and analysis of shallow debris flows. Probes specifically developed for this study include the miniature t-bar, ball, motorized vane (MV), and toroid. The t-bar, ball, and MV were developed to measure intact and remolded undrained shear strengths (su and sur). The t-bar and ball can obtain continuous strength profiles and measure sur at discrete depths in the box corer while the MV measures su and sur at discrete depths. The toroid is a form of model pipeline testing which was developed to investigate pipe-soil interaction during axial pipeline movement. Vertical loading and displacement rates can be selected for the toroid to mimic axial pipeline displacement for a variety of pipe weights. A load frame for both miniature penetrometer and toroid testing was developed for testing directly on box core samples offshore. This research presents results from offshore and laboratory testing of the box core and recommended testing procedures for full flow and toroid probes on box core samples.

Experimentation exploring the movement of voids within carbon fiber reinforced plastics was performed using fluorescent dye infused into the laminates observed through a transparent mold under ultraviolet light. In situ photography was used as an inspection method for void content during Resin Transfer Molding for these laminates. This in situ inspection method for determining the void content of composite laminates was compared to more common ex-situ quality inspection methods i.e. ultrasonic inspection and cross-section microscopy. Results for localized and total void count in each of these methods were directly compared to test samples and linear correlations between the three test methods were sought. Test coupons were then cut from these laminates and were used to calculate the interlaminar shear strength at certain locations throughout the laminates. Although this research did not adequately observe correlations between results obtained from ultrasonic C-scans, cross-sectional microscopy and in situ photography of the surface, it was seen that the fluid dynamics of the thermosetting epoxy used in this experimentation correlated to results obtained from previous experimentation performed by students at Brigham Young University using vegetable oil as a substitute for resin.

[pt] Esta pesquisa teve como objetivo investigar o comportamento tensão-deformação-resistência da areia da Praia de Ipanema, RJ, em ensaios de cisalhamento simples (DSS) realizados em corpos de prova secos, cisalhados a volume constante sob carregamento monótono de deformação controlada. Foi desenvolvido um procedimento para moldagem de corpos de prova de areia na condição seca para ensaios de DSS. Os corpos de prova foram moldados nos domínios de compacidade relativa (CR) fofo, médio, compacto e muito compacto. Para cada um desses domínios de CR, foram realizados ensaios de DSS sob os seguintes valores de tensão vertical inicial: 25, 50, 100, 150, 300, 500 e 750 kPa. Os resultados permitiram avaliar a influência da tensão vertical inicial e do índice de vazios pré-cisalhamento (epc) na variação da tensão vertical (variação da tensão vertical no cisalhamento) necessária para manter a altura (e o volume) do corpo de prova constante durante o cisalhamento, na taxa de mobilização de ângulo de atrito no plano horizontal em relação à distorção, no valor do ângulo de atrito máximo mobilizado no plano horizontal, no valor da tensão cisalhante na ruptura, no valor da distorção na ruptura, bem como nos valores dos módulos de cisalhamento secantes G25 e G50. / [en] This research aimed to investigate the stress-strain-strength behavior of the Ipanema Beach (RJ) sand in direct simple shear tests (DSS) carried out on dry specimens, sheared at constant volume under strain-controlled static loading. A procedure for preparing dry sand specimens was developed for DSS tests. The specimens were prepared in loose, medium, dense and very dense domains of relative density (Dr). For each of these Dr domains, DSS tests were carried out under the following initial vertical stress values: 25, 50, 100, 150, 300, 500 and 750 kPa. The results allowed to evaluate the influence of the initial vertical stressand the pre-shear void ratio (epc) on the vertical stress change (variation of vertical stress in shear) necessary to keep the specimen height (and volume) constant during shear, on the rate ofmobilization of the friction angle in the horizontal plane in relation to distortion, on the value of the maximum friction angle mobilized in the horizontal plane, on the value of the shear stress at failure, on the value of the distortion at failure, as well as on the values of the secant shear modulus G25and G50.

No description available.