Este trabalho tem como objetivo estudar a distribuição de tensões em um solo arenoso reforçado com fibras de polipropileno através de ensaios de prova de carga em placa circular, com medidas diretas de tensão pelo uso de células de tensão total. Busca-se investigar a influência da adição de fibras no comportamento carga-recalque de camadas compactadas de solo, avaliando o efeito do teor de fibras. Calibrações em laboratório foram realizadas para avaliar os fatores que afetam as medições de tensões em células de tensão total inseridas no solo. Utilizou-se também o Método dos Elementos Finitos (MEF) para simular numericamente a distribuição de tensões dentro de câmaras de calibração. Ensaios de provas de carga em placa de 0,30 m de diâmetro sobre camadas de areia compactada, reforçada e não reforçada com fibras, foram realizados, buscando a investigação do comportamento cargarecalque destas misturas, dos mecanismos de ruptura e da distribuição de tensões no interior das camadas e no contato solo/placa. A análise dos resultados mostra que a distribuição das tensões verticais na câmara de calibração é função do seu fator de forma e que as constantes de calibração também são função da posição de instalação das células de tensão. Nos ensaios de placa pode-se observar que o comportamento carga-recalque do solo arenoso é significativamente influenciado pela adição de fibras, aumentando a capacidade de suporte e alterando os mecanismos de ruptura. As medidas de tensões mostram uma mudança na distribuição de tensões com a inclusão do reforço. / The aim of this work is to study the polypropylene fiber-reinforced sand stress distribution through circular plate load tests, with direct stress measurement using total stress cells. The influence of fiber inclusion in load-settlement behavior of thick compacted soil layers was investigated and the fiber content effect evaluated. Laboratory calibrations were carried out in order to evaluate the factors that affect the stress measurements in total stress cells inserted in the soil. The Finite Element Method (FEM) was applied to simulate the numerical stress distribution inside the calibration chambers. Plate load tests with 0.30 m diameter plate bearing on compacted sand reinforced and non-reinforced layers were carried out to investigate the load-settlement behavior, failure mechanisms and stress distributions inside the sand layers and in the soil/plate contact. The analysis of the results shows that the vertical stress distribution inside the calibration chambers is a function of the high/diameter relationship and the calibration constants are a function of the stress cells installation position. It can be observed that the sand load-settlement behavior is significantly influenced by fiber inclusion, increasing bearing capacity and changing failure mechanisms. The stress measurements indicate an alteration in the stress distribution with the fiber inclusion.

Este trabalho tem como objetivo estudar a distribuição de tensões em um solo arenoso reforçado com fibras de polipropileno através de ensaios de prova de carga em placa circular, com medidas diretas de tensão pelo uso de células de tensão total. Busca-se investigar a influência da adição de fibras no comportamento carga-recalque de camadas compactadas de solo, avaliando o efeito do teor de fibras. Calibrações em laboratório foram realizadas para avaliar os fatores que afetam as medições de tensões em células de tensão total inseridas no solo. Utilizou-se também o Método dos Elementos Finitos (MEF) para simular numericamente a distribuição de tensões dentro de câmaras de calibração. Ensaios de provas de carga em placa de 0,30 m de diâmetro sobre camadas de areia compactada, reforçada e não reforçada com fibras, foram realizados, buscando a investigação do comportamento cargarecalque destas misturas, dos mecanismos de ruptura e da distribuição de tensões no interior das camadas e no contato solo/placa. A análise dos resultados mostra que a distribuição das tensões verticais na câmara de calibração é função do seu fator de forma e que as constantes de calibração também são função da posição de instalação das células de tensão. Nos ensaios de placa pode-se observar que o comportamento carga-recalque do solo arenoso é significativamente influenciado pela adição de fibras, aumentando a capacidade de suporte e alterando os mecanismos de ruptura. As medidas de tensões mostram uma mudança na distribuição de tensões com a inclusão do reforço. / The aim of this work is to study the polypropylene fiber-reinforced sand stress distribution through circular plate load tests, with direct stress measurement using total stress cells. The influence of fiber inclusion in load-settlement behavior of thick compacted soil layers was investigated and the fiber content effect evaluated. Laboratory calibrations were carried out in order to evaluate the factors that affect the stress measurements in total stress cells inserted in the soil. The Finite Element Method (FEM) was applied to simulate the numerical stress distribution inside the calibration chambers. Plate load tests with 0.30 m diameter plate bearing on compacted sand reinforced and non-reinforced layers were carried out to investigate the load-settlement behavior, failure mechanisms and stress distributions inside the sand layers and in the soil/plate contact. The analysis of the results shows that the vertical stress distribution inside the calibration chambers is a function of the high/diameter relationship and the calibration constants are a function of the stress cells installation position. It can be observed that the sand load-settlement behavior is significantly influenced by fiber inclusion, increasing bearing capacity and changing failure mechanisms. The stress measurements indicate an alteration in the stress distribution with the fiber inclusion.

Este trabalho tem como objetivo estudar a distribuição de tensões em um solo arenoso reforçado com fibras de polipropileno através de ensaios de prova de carga em placa circular, com medidas diretas de tensão pelo uso de células de tensão total. Busca-se investigar a influência da adição de fibras no comportamento carga-recalque de camadas compactadas de solo, avaliando o efeito do teor de fibras. Calibrações em laboratório foram realizadas para avaliar os fatores que afetam as medições de tensões em células de tensão total inseridas no solo. Utilizou-se também o Método dos Elementos Finitos (MEF) para simular numericamente a distribuição de tensões dentro de câmaras de calibração. Ensaios de provas de carga em placa de 0,30 m de diâmetro sobre camadas de areia compactada, reforçada e não reforçada com fibras, foram realizados, buscando a investigação do comportamento cargarecalque destas misturas, dos mecanismos de ruptura e da distribuição de tensões no interior das camadas e no contato solo/placa. A análise dos resultados mostra que a distribuição das tensões verticais na câmara de calibração é função do seu fator de forma e que as constantes de calibração também são função da posição de instalação das células de tensão. Nos ensaios de placa pode-se observar que o comportamento carga-recalque do solo arenoso é significativamente influenciado pela adição de fibras, aumentando a capacidade de suporte e alterando os mecanismos de ruptura. As medidas de tensões mostram uma mudança na distribuição de tensões com a inclusão do reforço. / The aim of this work is to study the polypropylene fiber-reinforced sand stress distribution through circular plate load tests, with direct stress measurement using total stress cells. The influence of fiber inclusion in load-settlement behavior of thick compacted soil layers was investigated and the fiber content effect evaluated. Laboratory calibrations were carried out in order to evaluate the factors that affect the stress measurements in total stress cells inserted in the soil. The Finite Element Method (FEM) was applied to simulate the numerical stress distribution inside the calibration chambers. Plate load tests with 0.30 m diameter plate bearing on compacted sand reinforced and non-reinforced layers were carried out to investigate the load-settlement behavior, failure mechanisms and stress distributions inside the sand layers and in the soil/plate contact. The analysis of the results shows that the vertical stress distribution inside the calibration chambers is a function of the high/diameter relationship and the calibration constants are a function of the stress cells installation position. It can be observed that the sand load-settlement behavior is significantly influenced by fiber inclusion, increasing bearing capacity and changing failure mechanisms. The stress measurements indicate an alteration in the stress distribution with the fiber inclusion.

The present thesis proposes model for the analyses of stress-strain response of fiber reinforced soil and municipal solid waste (MSW). The concept of reinforcing soils by introducing tension resisting elements such as fibers is becoming widely accepted. Fiber inclusions are found to improve the post-peak behavior of the soil. Evaluation of the stress-strain response of the fiber-reinforced soil indicates that mobilization of the fiber tension generally requires a strain level higher than that corresponding to the peak strength of unreinforced soil. Further, geotechnical engineering properties of MSW such as compressibility, shear strength and stiffness are of prime importance in design and maintenance of landfills. It is also referred in literature that MSW tends to behave as fiber-reinforced soil due to the presence of various types of wastes in its matrix. However, it is not well understood how the stress-strain and strength characteristics vary with time as the biodegradation of waste continues in the landfill. Based on the experimental observations, in this thesis, an attempt is made for developing generalized constitutive models based on the critical state soil mechanics frame work for fiber reinforced soils and municipal solid waste. The proposed models consider the fiber effect in fiber reinforced soil and, time dependent mechanical and biodegradation effects in case of municipal solid waste, respectively. The proposed models are able to capture the stress-strain and pore water pressure response in both the cases. For better understanding, the present thesis is divided into following seven chapters. Chapter 1 is an introductory chapter, in which the need for use of the constitutive models is presented. Further, the organization of thesis is also presented. Chapter 2 presents a brief description of the available studies in the literature on fiber-reinforced soils and municipal solid waste. Various studies on fiber-reinforced soil included experimental results (both laboratory and field) and modeling methods. Experiments on fiber-reinforced soils were mainly carried out with triaxial compression tests, unconfined compression tests, direct shear tests, one dimensional consolidation tests, etc. Force equilibrium model, limit equilibrium model, statistical theory, regression based models are some of the models available in the literature for quantifying the strength of the fiber-reinforced soil. Further, various studies with regard to the engineering properties of municipal solid waste and their characteristic properties available in the literature are presented. They include different models proposed by various researchers for the prediction of stress-strain response, time dependent behavior and load settlement analysis of the municipal solid waste. Finally, based on the literature review, the scope and objectives of the thesis are presented at the end. Chapter 3 describes various types of soils, properties of soils and fibers used in the present study. A detailed description of the sample preparation and methods adopted in the experimental program are presented in this chapter. Chapter 4 presents the experimental results of triaxial compression tests and one dimensional consolidation test carried out on fiber-reinforced soils. Based on the experimental observations, a constitutive model for fiber-reinforced soil in the frame work of modified cam clay model is proposed. Further, the detailed derivation of proposed model and the discussion on evaluation of the input model parameters from triaxial and consolidation tests are presented. The predictions from the proposed models are validated with the experimental data. From the comparison of the results from the proposed model and experiments, it is evident that the proposed model is able to capture stress-strain behavior of fiber-reinforced soils. Chapter 5 presents the experimental studies on the behavior of municipal solid waste based on the triaxial compression and consolidation tests. Based on the experimental observations, a constitutive model for municipal solid waste in the frame work of modified cam clay model is proposed which considers the mechanisms such as mechanical creep and biodegradation. It also provides detailed description of the selection of the input parameters required for the proposed model. The experimental results in the form of stress-strain and pore water pressure response are compared with the prediction from the proposed model. In addition, the applicability of the proposed model is illustrated using detailed parametric studies of parameters of the model for various ranges. Chapter 6 presents a brief study of load settlement response on municipal solid waste using a case example. The constitutive model for municipal solid waste proposed in chapter 5 is used to study the time-settlement response of municipal solid waste and to compare the results with available published models considering different mechanisms. The major conclusions from the study are presented at the end. Chapter 7 presents a brief summary and conclusions from the various studies reported in the present thesis. vi

[pt] O presente trabalho tem como objetivo a implementação e avaliação de um modelo constitutivo para solos reforçados com fibra (compósito). A principal característica do modelo constitutivo implementado é que cada material (matriz de solo e fibra) segue sua própria lei constitutiva e ao mesmo tempo interagem entre si. Utilizando um algoritmo explícito, são implementados os modelos Cam Clay Modificado e Lade-Kim para a matriz de solo, cuja verificação é feita mediante o programa PLAXIS 2D e curvas tensão-deformação obtidas da literatura, respectivamente. Posteriormente, é adicionado o comportamento da fibra no desenvolvimento das tensões no compósito e verificado mediante a comparação das curvas tensão-deformação com as apresentadas por Diambra et al. (2013). As linguagens de programação utilizadas neste trabalho foram duas, a primeira é a utilizada no programa MATLAB, onde os códigos dos modelos são verificados e validados em relação à um conjunto de ensaios triaxiais de areia reforçada com fibra. Posteriormente foi usada a linguagem de programação FORTRAN para incluir o modelo constitutivo para solo reforçado com fibras no programa de elementos finitos ABAQUS, através da sub-rotina UMAT. Porém, para a implementação na sub-rotina UMAT os códigos dos modelos implementados no MATLAB sofrem algumas modificações com a finalidade de que o ABAQUS consiga compilar e representar adequadamento o comportamento do modelo constitutivo, mediante a correta utilização de vetores e propriedades desta. Finalmente, são modelados ensaios triaxiais drenados para verificar que a implementação mediante a sub-rotina UMAT é satisfatória. / [en] The present work aims to implement and evaluate a constitutive model for fiber-reinforced soils (composite). The main characteristic of the constitutive model implemented is that each material (soil and fiber matrix) follows its own constitutive law and at the same time interact with each other. Using an explicit algorithm, the Cam Clay Modified and Lade-Kim models are implemented for the soil matrix, verified by the PLAXIS 2D software and stress-strain curves obtained from the literature, respectively. Later, it is included the behavior of the fiber in the development of the stresses in the composite and verified by the comparison of the stress-strain curves with those presented by Diambra et al. (2013). The programming languages used in this work were two, the first one is the one used in the MATLAB program, where the codes of the models are verified and validated in relation to a set of triaxial tests of fiber-reinforced sands. Later the programming language was converted into FORTRAN to include the constitutive model for fiber reinforced soil in the ABAQUS finite element software, through the UMAT subroutine. However, for the implementation in the UMAT subroutine the codes of the models implemented in MATLAB undergo some modifications in order that ABAQUS can compile and represent adequately the behavior of the constitutive model through the correct use of vectors and its properties. Finally, drained triaxial tests are modeled to verify that the implementation through the UMAT subroutine is satisfactory.