Mestrado em Geotecnia, Estruturas e Construção Civil (EECA)
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Navegando Mestrado em Geotecnia, Estruturas e Construção Civil (EECA) por Por Área do CNPQ "ENGENHARIAS::ENGENHARIA CIVIL::GEOTECNICA"
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Item Método de retroanálise de parâmetros de resistência ao cisalhamento em taludes(Universidade Federal de Goiás, 2024-01-31) Oliveira, Mariele Rodrigues de; Gitirana Júnior, Gilson de Farias Neves; http://lattes.cnpq.br/4710728908810849; Gitirana Junior, Gilson De Farias Neves; Teixeira, Raquel Souza; Mascarenha, Márcia Maria dos AnjosThe back analysis of slopes that have failed is of paramount importance to identify the geotechnical parameters at the moment of sliding, implement corrective actions, and comprehend the conditions during failure to prevent similar accidents. However, the inherent difficulty in utilizing existing methods, many of which are based on trial and error, coupled with scattered and incongruent results, fosters research in this field. Physical models require extensive time and financial resources, while field and laboratory tests present significant uncertainties related to factors such as sample disturbance and mass heterogeneity. Consequently, the core of this study aimed to develop and validate a method for back analyzing shear strength parameters for slopes, homogeneous and heterogeneous, saturated and unsaturated, with circular and non-circular sliding surfaces, two-dimensional and threedimensional. In this method, an objective function named H was defined, composed of the normalized distance between the actual failure surface and a critical sliding surface (dn), as well as the variation of the safety factor (G). Optimization techniques, including Cuckoo Search and Entry and Exit critical surface methods, along with global and local optimization methods (Nelder-Mead), were employed. The effectiveness of the back analysis was demonstrated in efficiently obtaining optimal values; however, caution in the approach and validation with laboratory and field data are necessary. It was noted that the choice of optimization method along with the critical surface location method is crucial for obtaining the desired optimal parameters. For circular surfaces of saturated homogeneous slopes, global optimization methods are dispensable when using the Entry and Exit method, as methods like Nelder-Mead require fewer iterations and efficiently achieve optimal parameters. The optimization of the objective function H for saturated homogeneous slopes with non-circular surfaces required multiple iterations due to the presence of multiple local minima, accentuating the difficulty and complexity of non-circular surfaces. For unsaturated homogeneous slopes, it is recommended to employ global optimization methods, and the Entry and Exit critical surface search method yielded more satisfactory results compared to Cuckoo Search. In two-layer saturated slopes, successful minimization occurs as the most influential parameters approach optimal values. In three-dimensional slopes, optimization results showed a reduction in cohesion values and an increase in friction angles compared to the 2D benchmark.in cohesion values and an increase in friction angles compared to the 2D benchmark.Item Estudo de parâmetros físico-químicos da solução do poro de argamassas com adições minerais e sua contribuição para a durabilidade(Universidade Federal de Goiás, 2023-08-09) Santos, Aloísio Fernando Silva; Oliveira, Andrielli Morais de; http://lattes.cnpq.br/9590390602101344; Matos, Oswaldo Cascudo; http://lattes.cnpq.br/3336749062812376; Matos, Oswaldo Cascudo; Faria, Tulio Honório de; Ferreira, Rondinele Alberto dos Reis; Cascudo, Helena Carasek; Oliveira, Andrielli Morais deRecent studies have shown that the durability of reinforced concrete is related to its chemical ability to maintain an alkaline environment through the porous solution. In the absence of aggressive agents, the passivation film on the steel bars remains stable. However, in the presence of chlorides or under the effect of carbonation, this protection can be interrupted and the corrosion process initiated. Therefore, it is crucial to have knowledge of the internal chemical composition of the pores in cementitious materials to mitigate these effects, especially the chemical knowledge of the free water present in these materials. The chemical analysis of the electrolytic solution present in the pores has been studied for decades. However, there are few studies that focus on cementitious materials subjected to combinations of aggressive agents and the use of mineral additions. Thus, this work aims to analyze and obtain physicochemical parameters of the pore solution in mortars with silica fume and metakaolin using different methods of extracting the internal free water, namely: pressure application extraction, ex situ leaching, in situ leaching, and equilibrium water extraction when subjected to chloride attack or accelerated carbonation, as well as both situations combined. The use of mineral additions was considered with the objective of generating different chemical parameters related to the aqueous solution in the pores since they chemically modify the entire composition and also modify the microstructure of mortars. They are widely used supplementary materials of great relevance in civil construction. pH analysis, electrical conductivity, ionic strength, dissolved solids, redox potential, and ionic chemical analysis were performed. To better understand the formation and changes in the chemical composition of the pore solution, microstructural implications were also studied in terms of thermogravimetry, FTIR, XRD, SEM, surface electrical resistivity, specific surface area, and pore volume. The different analytical techniques used to analyze the ionic composition of the pore solution were considered similar and reliable. It was observed that mineral additions contributed to the reduction of the ionic charge in the solution, while carbonation and chloride attack caused significant changes in the ions present. When these mechanisms occur in combination, the order in which they occur influences the formation of products and the quality of the pore solution. Finally, it is important to emphasize that the methods of extracting the pore solution can be used in different situations, but each one has its own limitations and requires precautions during the test. It is essential to consider these restrictions and adopt appropriate measures to ensure the reliability of the obtained results.