O presente trabalho aborda o estudo do comportamento de túneis em maciços de solo. É dada ênfase na aplicação de análises numéricas com emprego de diferentes modelos constitutivos elasto-plásticos para solos. São apresentadas análises numéricas tridimensionais de um túnel amplamente instrumentado pertencente à Companhia do Metropolitano de São Paulo. As análises são realizadas com auxílio de um programa computacional de elementos finitos. O comportamento do maciço em pontos situados ao redor da escavação é minuciosamente estudado e a capacidade dos modelos em representar adequadamente o comportamento verificado na obra pelas instrumentações é avaliada. Além das análises numéricas o trabalho aborda os principais conceitos relacionados com escavações de túneis em maciços de solo. Conceitos relacionados com a engenharia prática de túneis são apresentados de maneira qualitativa, sem formulações teóricas e matemáticas. Uma revisão bibliográfica com publicações recentes das principais revistas e periódicos que tratam do tema de análise numérica aplicada a túneis é apresentada. O trabalho também apresenta uma revisão dos principais conceitos relacionados com os modelos constitutivos comumente utilizados para análise de problemas de geotecnia. Além do modelo elástico são apresentados os modelos elasto-plásticos de Tresca, von Misses, Drucker-Prager e Mohr-Coulomb. Uma breve introdução aos conceitos básicos de estado crítico, juntamente com as equações do modelo Cam-Clay original e Cam-Clay modificado são apresentadas. Antes da apresentação das equações desses modelos constitutivos, são introduzidos os conceitos básicos relacionados com o comportamento dos materiais elasto-plásticos. Os conceitos de material elástico perfeitamente plástico e de material com endurecimento (ou hardening) e amolecimento (ou softening) são apresentados. Os conceitos de superfície de plastificação e de superfície de potencial plástico também são apresentados. Por fim, são sintetizados os pontos mais relevantes da pesquisa realizada, apontando as limitações do trabalho com sugestões de novos estudos a serem realizados nessa mesma linha de pesquisa. / The present research approaches the study of the behaviour of tunnels in soil. It is given emphasis in the application of numerical analyses using different elasto-plastic constitutive models for soils. Three-dimensional numerical analyses of a widely instrumented tunnel belonging to the Company of the Metropolitan of São Paulo are presented. The analyses are carried through with aid of a computational program of finite elements. The behaviour of the soil mass in points located around the excavation is thoroughly studied and the capacity of the models in adequately representing the field behavior verified by the instrumentations is evaluated. Furthermore, the work approaches the main concepts related to tunneling in soils. Concepts related to practical engineering of tunnels are presented in a qualitative way, without theoretical and mathematical formulations. A literature review of recent publications of the most important periodic magazines and that deal with the subject of numerical analysis applied to tunnels is presented. The work also presents a revision of the main concepts related to the constitutive models normally used for analysis of geotechnical problems. Beyond the elastic model the elasto-plastics models of Tresca, von Misses, Drucker-Prager and Mohr-Coulomb are presented. Brief introductions to the basic concepts of critical state, together with the equations of the (original) Cam-Clay original and (modified) Cam-Clay modified models are presented. Before the presentation of the equations of these constitutive models, the basic concepts of the behaviour of the elasto-plastics materials are introduced. The concepts of perfectly plastic elastic material and material with hardening and softening are presented. The concepts of plastic surface and plastic potencial surface are also presented. Finally, the most relevant points of the research are synthesized, pointing the limitations of the developed work along with suggestions for new studies to be carried through in this line of research.

O presente trabalho aborda o estudo do comportamento de túneis em maciços de solo. É dada ênfase na aplicação de análises numéricas com emprego de diferentes modelos constitutivos elasto-plásticos para solos. São apresentadas análises numéricas tridimensionais de um túnel amplamente instrumentado pertencente à Companhia do Metropolitano de São Paulo. As análises são realizadas com auxílio de um programa computacional de elementos finitos. O comportamento do maciço em pontos situados ao redor da escavação é minuciosamente estudado e a capacidade dos modelos em representar adequadamente o comportamento verificado na obra pelas instrumentações é avaliada. Além das análises numéricas o trabalho aborda os principais conceitos relacionados com escavações de túneis em maciços de solo. Conceitos relacionados com a engenharia prática de túneis são apresentados de maneira qualitativa, sem formulações teóricas e matemáticas. Uma revisão bibliográfica com publicações recentes das principais revistas e periódicos que tratam do tema de análise numérica aplicada a túneis é apresentada. O trabalho também apresenta uma revisão dos principais conceitos relacionados com os modelos constitutivos comumente utilizados para análise de problemas de geotecnia. Além do modelo elástico são apresentados os modelos elasto-plásticos de Tresca, von Misses, Drucker-Prager e Mohr-Coulomb. Uma breve introdução aos conceitos básicos de estado crítico, juntamente com as equações do modelo Cam-Clay original e Cam-Clay modificado são apresentadas. Antes da apresentação das equações desses modelos constitutivos, são introduzidos os conceitos básicos relacionados com o comportamento dos materiais elasto-plásticos. Os conceitos de material elástico perfeitamente plástico e de material com endurecimento (ou hardening) e amolecimento (ou softening) são apresentados. Os conceitos de superfície de plastificação e de superfície de potencial plástico também são apresentados. Por fim, são sintetizados os pontos mais relevantes da pesquisa realizada, apontando as limitações do trabalho com sugestões de novos estudos a serem realizados nessa mesma linha de pesquisa. / The present research approaches the study of the behaviour of tunnels in soil. It is given emphasis in the application of numerical analyses using different elasto-plastic constitutive models for soils. Three-dimensional numerical analyses of a widely instrumented tunnel belonging to the Company of the Metropolitan of São Paulo are presented. The analyses are carried through with aid of a computational program of finite elements. The behaviour of the soil mass in points located around the excavation is thoroughly studied and the capacity of the models in adequately representing the field behavior verified by the instrumentations is evaluated. Furthermore, the work approaches the main concepts related to tunneling in soils. Concepts related to practical engineering of tunnels are presented in a qualitative way, without theoretical and mathematical formulations. A literature review of recent publications of the most important periodic magazines and that deal with the subject of numerical analysis applied to tunnels is presented. The work also presents a revision of the main concepts related to the constitutive models normally used for analysis of geotechnical problems. Beyond the elastic model the elasto-plastics models of Tresca, von Misses, Drucker-Prager and Mohr-Coulomb are presented. Brief introductions to the basic concepts of critical state, together with the equations of the (original) Cam-Clay original and (modified) Cam-Clay modified models are presented. Before the presentation of the equations of these constitutive models, the basic concepts of the behaviour of the elasto-plastics materials are introduced. The concepts of perfectly plastic elastic material and material with hardening and softening are presented. The concepts of plastic surface and plastic potencial surface are also presented. Finally, the most relevant points of the research are synthesized, pointing the limitations of the developed work along with suggestions for new studies to be carried through in this line of research.

Geosynthetic reinforced soil (GRS) is a soil improvement technology in which closely spaced horizontal layers of geosynthetic are embedded in a soil mass to provide lateral support and increase strength. GRS is popular due to a relatively new application for bridge support, as well as long-standing application in mechanically stabilized earth walls. Several different GRS design methods have been used, and some are application-specific and not based on fundamental principles of mechanics. Because consensus regarding fundamental behavior of GRS is lacking, numerical and mathematical analyses were performed for laboratory tests obtained from the published literature of GRS under triaxial compression in consolidated-drained conditions. A three-dimensional numerical model was developed using FLAC3D. An existing constitutive model for the soil component was modified to incorporate confining pressure dependency of friction angle and dilation parameters, while retaining the constitutive model's ability to represent nonlinear stress-strain response and plastic yield. Procedures to obtain the parameter values from drained triaxial compression tests on soil specimens were developed. A method to estimate the parameter values from particle size distribution and relative compaction was also developed. The geosynthetic reinforcement was represented by two-dimensional orthotropic elements with soil-geosynthetic interfaces on each side. Comparisons between the numerical analyses and laboratory tests exhibited good agreement for strains from zero to 3% for tests with 1 to 3 layers of reinforcement. As failure is approached at larger strains, agreement was good for specimens that had 1 or 2 layers of reinforcement and soil friction angle less than 40 degrees. For other conditions, the numerical model experienced convergence problems that could not be overcome by mesh refinement or reducing the applied loading rate; however, it appears that, if convergence problems can be solved, the numerical model may provide a mechanics-based representation of GRS behavior, at least for triaxial test conditions. Three mathematical theories of GRS failure available in published literature were applied to the laboratory triaxial tests. Comparisons between the theories and the tests results demonstrated that all three theories have important limitations. These numerical and mathematical evaluations of laboratory GRS tests provided a basis for recommending further research. / Ph. D. / Sometimes soils in nature do not possess the strength characteristics necessary to be used in a specific engineering application, and soil improvement technologies are necessary. Geosynthetic reinforced soil (GRS) is a soil improvement technology in which closely spaced horizontal layers of geosynthetic material are placed in a soil mass to provide lateral support and increase the strength of the reinforced mass. The geosynthetic materials used in GRS are flexible sheets of polymeric materials produced in the form of woven fabrics or openwork grids. This technology is widely used to improve the strength of granular soil to form walls and bridge abutments. Current design methods for GRS applications are case specific, some of these methods do not rely on fundamental principles of physics, and consensus regarding the fundamental behavior of GRS is lacking. To improve understanding of GRS response independent of application, the three dimensional response of GRS specimens to axisymmetric loading were investigated using numerical and mathematical analysis. A numerical model using the finite difference method in which the domain is discretized in small zones was developed, and this model can capture the response of GRS laboratory specimens under axisymmetric loading with reasonably good accuracy at working strains (up to 3% strain). This numerical model includes a robust constitutive model for the soil that is capable of representing the most important stiffness and strength characteristics of the soil. For large strains approaching failure loading, the numerical model encountered convergence difficulties when the soil strength was high or when more than two layers of reinforcement were used. As an alternative to discretized numerical analysis, three mathematical theories available in the published literature were applied to the collected GRS laboratory test data. These evaluations demonstrated that all three theories have important limitations in their ability to represent failure of GRS laboratory test specimens. This study is important because it proposed a numerical model in 3D to represent the GRS behavior under working strains, and it identified several limitations of mathematical theories that attempt to represent the ultimate strength of GRS. Based on these findings, recommendations for further research were developed.