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[en] DISCRETE MICRO-MICROMECHANICAL MODELING OF RESIDUAL SOILS / [pt] MODELAGEM MICRO-MECÂNICA DISCRETA DE SOLOS RESIDUAISJUAN PABLO IBANEZ 10 July 2008 (has links)
[pt] O presente trabalho de pesquisa estuda a modelagem numérica de solos residuais no que se refere ao seu comportamento mecânico, a partir da análise micro-mecânica, utilizando como ferramenta de modelagem o método dos elementos discretos (MED), o qual permite a representação do solo como meio particulado 2D por meio de elementos discretos circulares. Diversos são os fenômenos micro e macro-estruturais presentes nos solos residuais, os quais condicionam sua resposta mecânica, podendo-se mencionar a dupla estrutura e dupla porosidade, a presença de uma matriz argilosa, a condição não saturada, a cimentação e quebra de grãos, e a presença de pequenos blocos de rocha não alterada. A partir do estudo destes fenômenos foram propostas formulações matemáticas que os descrevem, as quais foram implementadas no código de elementos discretos DEMlib. Após a calibração e validação do programa de análise implementado, a influência de cada um destes fenômenos na resposta mecânica do solo foi estudada pela simulação dos ensaios edométrico e de cisalhamento direto em amostras discretas com compacidade variada, criticando os resultados e obtendo conclusões. Em seguida estes fenômenos foram estudados de forma combinada no intuito de reproduzir a resposta de alguns solos residuais jovens e maduros. Encerrando o trabalho foram resumidas as conclusões obtidas e apontadas sugestões para um aprofundamento e desenvolvimentos subseqüentes da linha de pesquisa implementada. / [en] The present research studies the numerical modeling of the
mechanical behavior of residual soils, by a micro-mechanical
analysis, using as modeling tool the discrete elements
method (DEM), which allows the representation of the soil
as 2D particle assembly of circular discrete elements. There
are several micro and macro structural phenomena present in
residual soils, which determine its mechanical response:
double structure and double porosity of soil mass, the
presence of a clay-like matrix, partially saturated
condition, grain cementation, grain crushing, and the
presence of small blocks of not-weathered parental rock.
Based on the study of these phenomena, mathematical
formulations have been proposed in order to describe them,
which have been implemented in the DEMlib discrete elements
code. After calibration and validation of the implemented
analysis program, the influence of each phenomena in soil
response was studied by simulating edometrical and direct
shear tests in discrete samples with several
densities, criticizing the results and getting conclusions.
Afterwards, these phenomena were studied in a combined way
in order to reproduce the response of some young and mature
residual soils. To finish up this work the conclusions
obtained have been summarized and suggestions for deepening
and further developing of the implemented research line have
been stated.
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[en] NUMERICAL MODELLING OF PILE INSTALLATION AND PILE LOAD TEST USING DISCRETE ELEMENTS / [pt] MODELAGEM NUMÉRICA DO PROCESSO DE INSTALAÇÃO E PROVA DE CARGA EM ESTACAS USANDO ELEMENTOS DISCRETOSRICARDO GUREVITZ CUNHA ESPOSITO 14 June 2016 (has links)
[pt] As alterações no solo decorrentes de um elemento de fundação profunda e
seus desempenhos sob a aplicação de carga axial são processos há muito tempo
estudados na engenharia civil. Diversos fatores como, método de instalação
utilizado, formato da estaca, interações solo-estrutura, mecanismos de
transferências de carga, movimentação do solo e alterações na compressibilidade e
tensões do solo adjacente, apresentam desafios importantes que ainda não foram
totalmente compreendidos nos fenômenos de penetração e capacidade de suporte
em estacas. Diversos avanços foram realizados ao longo das últimas décadas para
se investigar estes comportamentos, a partir procedimentos experimentais e novas
formas de instrumentação, assim como ferramentas numéricas sofisticadas com o
emprego de complexos modelos constitutivos em elementos finitos. Apesar destes
avanços, a modelagem numérica dos processos citados, com todas as suas
complexidades, ainda encontra alguns desafios. Devido a facilidade em lidar com
simulações de grandes deformações e de captar o comportamento dilatante e nãolinear
de solos granulares, o Método dos Elementos Discretos apresenta uma
excelente ferramenta para investigar estes processos, sem grandes complicações.
O presente trabalho procurou avaliar os comportamentos obtidos a partir de
diferentes processos de instalação da estaca e seus efeitos nos resultados da prova
de carga estática em solos granulares. As alterações de tensão e deslocamento
foram avaliadas nos diferentes modelos e discutindo sobre uma metodologia
básica para obter correspondências qualitativas e quantitativas com os diferentes
comportamentos de campo e laboratório. Para este estudo foram utilizados os
programas PFC, na versão 2D, e o programa UDEC, da Itasca co. / [en] The disturbances experienced by the soil owing to the load applied to a deep
foundation and its relative behavior consist of long time studied phenomena in
civil engineering. Several factors such as the installation methods, the pile
geometry, the interactions between soil and structure, the load-transfer
mechanisms, the soil movements and the disturbances in the stress and
compressibility fields present major challenges that have not yet been completely
understood. Numerous advances have been observed throw-out the last decades,
in order to investigate these behaviors starting from the different pile
instrumentations, the use of calibration cameras and centrifuges and most recently
the measurement of the stress and strain fields inside the soil mass in model tanks.
Despite the advances the numerical modelling of those processes still faces major
challenges. Due to simplified approach used by the Discrete Element Method to
simulate large deformation and the dilant non-linear behavior of granular soils, it
presents as an excellent tool to investigate these processes without further
complications. The present work proposed to evaluate the different behaviors
obtained with the variations of installation methods investigated as well as their
effects in the results of the Pile Load Test. The disturbances were also evaluated
in the different models considered and a basic method to achieve qualitative and
quantitative comparisons was discussed. These studies were made possible with
the help of the PFC2D and UDEC programs developed by Itasca co.
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[en] MODELLING OF STEP-PATH TYPE FAILURE MECHANISMS IN FRACTURED ROCK SLOPE USING DISCRETE ELEMENTS / [pt] MODELAGEM DO MECANISMO DE RUPTURA TIPO STEP-PATH EM TALUDES ROCHOSOS FRATURADOS ATRAVÉS DO MÉTODO DOS ELEMENTOS DISCRETOSLUIS ARNALDO MEJIA CAMONES 26 February 2018 (has links)
[pt] Diferentes mecanismos de ruptura são considerados no momento de avaliar a estabilidade de um maciço rochoso fraturado. Entre estes, os mecanismos de ruptura tipo planar, em cunha e tombamentos têm sido
estudados intensivamente, existindo atualmente modelos matemáticos que permitem avaliá-los. Estes mecanismos de ruptura são restritos a taludes pequenos e com fraturas contínuas, nas quais o deslizamento ocorre ao longo destas descontinuidades. Em casos de taludes de grande altura ou
quando a persistência das fraturas é pequena em relação à escala do talude, o fraturamento torna-se descontínuo. Neste caso, o mecanismo de ruptura mais provável é o tipo Step-Path, o qual, a superfície de ruptura é formada por fraturas que se propagam através da rocha intacta juntando-se entre elas. Este fenômeno de união de fraturas é chamado de coalescência. Análises de estabilidade, como os probabilísticos ou por equilíbrio limite, são usados atualmente para avaliar estes tipos de rupturas, não se tendo ainda o desenvolvimento de um modelo numérico que possa representá-lo e reforçar estas teorias. O presente trabalho avalia o uso do Método dos Elementos Discretos na modelagem do mecanismo de ruptura tipo step- path, realizando uma análise de estabilidade que permita comparar os seus resultados com o método de equilíbrio limite. Foi utilizado o programa PFC nas versões 2D e 3D, assim como o programa FracGen para a geração de fraturas tridimensionais. A análise tridimensional foi feita mediante um acoplamento PFC3D-FracGen. A pesquisa inclui a análise e modelagem dos fenômenos de coalescência em amostras, assim como a influência da anisotropia na resistência das rochas em ensaios triaxiais. / [en] Different failure mechanisms are considered when a fracturated rock mass is valued. Some of them are being subject of accurate study, like planar failure mechanism, wedges and toppling, which are currently valued by mathematical models. These failure mechanisms are restricted to small slopes and with continue fractures, where the sliding occurs along these discontinuities. To height slopes or when the fracture persistence is smaller than the slope scale, the fracturing becomes discontinuous. In this case, the
most probable failure mechanism to happen is the step-path type, in which the failure surface is composed by fractures that propagate through the intact rock and that are joined together. This phenomenon of fracture union is known as coalescence. Stability analysis, like probability analysis or limit equilibrium analysis are currently utilized to evaluate this kind of failures, but its important to develop a numerical model to represent and reinforce these theories. This work aims to evaluate the use of Discrete Element Method to model step-path failure mechanism on a stability analysis and to compare the results with limit equilibrium method. The program used to simulate the slope is PFC (2D and 3D) and the program FracGen was used to generate three-dimensional fractures. Three-dimensional analysis was done by a coupling between PFC3D and FracGen. The research includes the analysis and modeling of coalescence phenomenon on rock samples, as well as the analysis of the anisotropy influence on rock strength obtained
from triaxial tests.
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[en] APPLICATION OF THE DISCRETE ELEMENT METHOD FOR MODELLING THE BLOCK-FLEXURAL TOPPLING MECHANISMS IN ROCK SLOPES / [pt] APLICAÇÃO DO MÉTODO DOS ELEMENTOS DISCRETOS NA MODELAGEM DO MECANISMO DE TOMBAMENTO BLOCO-FLEXURAL EM TALUDES ROCHOSOSFREDY ALVARO ELORRIETA AGRAMONTE 01 August 2016 (has links)
[pt] Em um maciço rochoso, as fraturas apresentam-se de forma irregular e
descontínua. A complexidade na distribuição espacial destas descontinuidades faz
com que o mecanismo de ruptura por tombamento ocorra mais frequentemente
por uma combinação de dois tipos de fenômenos: Tombamento de blocos e
flexural. Assim, a ruptura por tombamento do tipo bloco-flexural pode ser
considerada a forma mais comum presente neste tipo de mecanismo. Trabalhos
utilizando o método de equilíbrio limite ou modelos físicos estudam a influência
desta combinação, mas a literatura relata poucos trabalhos numéricos que possam
ajudar na compreensão dos fenômenos envolvidos neste processo de ruptura. O
presente trabalho procura modelar o mecanismo de ruptura por tombamento
bloco-flexural através do método dos elementos discretos (DEM), utilizando o
software PFC (Particle Flow Code). Em particular, procura-se avaliar as
potencialidades do método para estudos deste tipo, utilizando um novo modelo de
contato entre partículas e a calibração das propriedades elásticas do material
sintético. Apresentam-se também detalhes da metodologia utilizada e exemplos de
validação, incluindo comparações com soluções analíticas e semi-analíticas
disponíveis na literatura. / [en] Joints exhibit an irregular and discontinuous behavior inside the rock mass.
The spatial distribution complexity of these discontinuities causes the toppling
failure occurs more often by a combination of two types of toppling phenomena:
toppling of rock blocks and flexural toppling. Thus, the block-flexural toppling
can be considered the most common when a toppling process is being developed
in rock slopes. Analytical and physical models approach, were presented in order
to study each process individually, but the literature reports few works that may
help to understand the influence of the two processes together. The present work
aims to represents the mechanism of block-flexural toppling through the discrete
elements method (DEM) using the PFC (Particle Flow Code) software. In
particular, the objective is to assess the potential of the method for studies of this
type, using a new model of contact between particles and the elastic properties
calibration of the synthetic material. In order to do that, the work shows the
methodology details and validation examples, including comparisons with
analytical and semi-analytical solutions that are available in the literature.
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Modeling of realistic microstructures on the basis of quantitative mineralogical analysesKlichowicz, Michael 30 November 2020 (has links)
Diese Forschung zielt darauf ab, den Einsatz realistischer Mineralmikrostrukturen in Mineralverarbeitungssimulationen Simulationen von Aufbereitungsprozessen zu ermöglichen. Insbesondere Zerkleinerungsprozesse, wie z.B. das Brechen und Mahlen von mineralischen Rohmaterialien, werden stark von der mineralischen Mikrostruktur beeinflusst, da die Textur und die Struktur der vielen Körner und ihre mikromechanischen Eigenschaften das makroskopische Bruchverhalten bestimmen.
Ein Beispiel: Stellen wir uns vor, wir haben ein mineralisches Material, das im Wesentlichen aus Körnern zweier verschiedener Mineralphasen, wie Quarz und Feldspat, besteht. Wenn die mikromechanischen Eigenschaften dieser beiden Phasen unterschiedlich sind, wird sich dies wahrscheinlich auf das makroskopische Bruchverhalten auswirken. Unter der Annahme, dass die Körner eines der Minerale bei geringeren Belastungen brechen, ist es wahrscheinlich, dass sich ein Riss durch einen Stein dieses Materials durch die schwächeren Körner ausbreitet. Tatsächlich ist dies eine wichtige Eigenschaft für die Erzaufbereitung. Um wertvolle Mineralien aus einem Erz zu gewinnen, ist es wichtig, sie aus dem kommerziell wertlosen Material, in dem sie vorkommen, zu befreien. Dazu ist es wichtig zu wissen und zu verstehen, wie das Material auf Korngrößenebene bricht.
Um diesen Bruch simulieren zu können, ist es wichtig, realistische Modelle der mineralischen Mikrostrukturen zu verwenden. Diese Studie zeigt, wie solche realistischen zweidimensionalen Mikrostrukturen auf der Grundlage der quantitativen Mikrostrukturanalyse am Computer erzeugt werden können. Darüber hinaus zeigt die Studie, wie diese synthetischen Mikrostrukturen dann in die gut etablierte Diskrete-Elemente-Methode integriert werden können, bei der der Bruch von mineralischem Material auf Korngrößenebene simuliert werden kann.:List of Acronyms VII
List of Latin Symbols IX
List of Greek Symbols XV
1 Introduction 1
1.1 Motivation for using realistic microstructures in Discrete Element Method (DEM) 1
1.2 Possibilities for using realistic mineral microstructures in DEM simulations . 4
1.3 Objective and disposition of the thesis . . . . . . . . . . . . . . . . . . . . 7
2 Background 9
2.1 Discrete Element Method (DEM) . . . . . . . . . . . . . . . . . . . . . . . . 9
2.1.1 Fundamentals of the Discrete Element Method (DEM) . . . . . . . . 9
2.1.2 Applications of DEM in comminution science . . . . . . . . . . . . . 21
2.1.3 Limitations of DEM in comminution science . . . . . . . . . . . . . . 26
2.2 Quantitative Microstructural Analysis . . . . . . . . . . . . . . . . . . . . . 29
2.2.1 Fundamentals of the Quantitative Microstructural Analysis . . . . . . 29
2.2.2 Applied QMA in mineral processing . . . . . . . . . . . . . . . . . . 49
2.2.3 Applicability of the QMA for the synthesis of realistic microstructures 49
3 Synthesis of realistic mineral microstructures for DEM simulations 51
3.1 Development of a computer-assisted QMA for the analysis of real and synthetic
mineral microstructures . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
3.1.1 Fundamentals of the computer-assisted QMA . . . . . . . . . . . . 53
3.1.2 The requirements for the false-color image. . . . . . . . . . . . . . 54
3.1.3 The conversion of a given real mineral microstructure into a false-color
image . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
3.1.4 Implementation of the point, line, and area analysis . . . . . . . . . 59
3.1.5 Selection of appropriate QMA parameters for analyzing two-dimensional
microstructures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
3.1.6 Summary of the principles of the adapted Quantitative Microstructural
Analysis (QMA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
3.2 Analysis of possible strategies for the microstructure synthesis . . . . . . . . 71
3.3 Implementation of the drawing method . . . . . . . . . . . . . . . . . . . . 76
3.3.1 Drawing of a single grain . . . . . . . . . . . . . . . . . . . . . . . 77
XVIII List of Greek Symbols
3.3.2 Drawing of multiple grains, which form a synthetic microstructure . . 81
3.3.3 Synthesizing mineral microstructures consisting of multiple phases . 85
3.4 The final program for microstructure analysis and synthesis . . . . . . . . . 89
3.4.1 Synthesis and analysis of an example microstructure . . . . . . . . . 90
3.4.2 Procedure for generating a realistic synthetic microstructure of a given
real microstructure . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
4 Validation of the synthesis approach 103
4.1 Methodical considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
4.1.1 The basic idea of the validation procedure . . . . . . . . . . . . . . 103
4.1.2 The experimental realizations . . . . . . . . . . . . . . . . . . . . . 108
4.2 Basic indenter test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
4.2.1 Considerations for the basic indenter test . . . . . . . . . . . . . . . 109
4.2.2 Realization and evaluation of the real basic indenter test . . . . . . . 114
4.2.3 Realization and evaluation of the simulated basic indenter test . . . 127
4.2.4 Conclusions on the basic indenter test . . . . . . . . . . . . . . . . . 138
4.3 Extended indenter test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
4.3.1 Basic considerations for the extended indenter test . . . . . . . . . . 139
4.3.2 Realization and evaluation of the real extended indenter test . . . . 142
4.3.3 Realization and evaluation of the simulated extended indenter test . 154
4.3.4 Conclusions on the extended indenter test . . . . . . . . . . . . . . 171
4.4 Particle bed test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172
4.4.1 Basic considerations for the particle bed test . . . . . . . . . . . . . 173
4.4.2 Realization and evaluation of the real particle bed test . . . . . . . . 176
4.4.3 Realization and evaluation of the simulated particle bed test . . . . . 188
4.4.4 Conclusions on the particle bed test . . . . . . . . . . . . . . . . . . 203
5 Conclusions and directions for future development 205
6 References 211
List of Figures 229
List of Tables 235
Appendix 237 / This research aims to make it possible to use realistic mineral microstructures in simulations of mineral processing. In particular, comminution processes, such as the crushing and grinding of raw mineral materials, are highly aff ected by the mineral microstructure, since the texture and structure of the many grains and their micromechanical properties determine the macroscopic fracture behavior. To illustrate this, consider a mineral material that essentially consists of grains of two diff erent mineral phases, such as quartz and feldspar. If the micromechanical properties of these two phases are diff erent, this will likely have an impact on the macroscopic fracture behavior. Assuming that the grains of one of the minerals break at lower loads, it is likely that a crack through a stone of that material will spread through the weaker grains. In fact, this is an important property for ore processing. In order to extract valuable minerals from an ore, it is important to liberate them from the commercially worthless material in which they are found. For this, it is essential to know and understand how the material breaks at grain-size level.
To be able to simulate this breakage, it is important to use realistic models of the mineral microstructures. This study demonstrates how such realistic two-dimensional microstructures can be generated on the computer based on quantitative microstructural analysis. Furthermore, the study shows how these synthetic microstructures can then be incorporated into the well-established discrete element method, where the breakage of mineral material can be simulated at grain-size level.:List of Acronyms VII
List of Latin Symbols IX
List of Greek Symbols XV
1 Introduction 1
1.1 Motivation for using realistic microstructures in Discrete Element Method (DEM) 1
1.2 Possibilities for using realistic mineral microstructures in DEM simulations . 4
1.3 Objective and disposition of the thesis . . . . . . . . . . . . . . . . . . . . 7
2 Background 9
2.1 Discrete Element Method (DEM) . . . . . . . . . . . . . . . . . . . . . . . . 9
2.1.1 Fundamentals of the Discrete Element Method (DEM) . . . . . . . . 9
2.1.2 Applications of DEM in comminution science . . . . . . . . . . . . . 21
2.1.3 Limitations of DEM in comminution science . . . . . . . . . . . . . . 26
2.2 Quantitative Microstructural Analysis . . . . . . . . . . . . . . . . . . . . . 29
2.2.1 Fundamentals of the Quantitative Microstructural Analysis . . . . . . 29
2.2.2 Applied QMA in mineral processing . . . . . . . . . . . . . . . . . . 49
2.2.3 Applicability of the QMA for the synthesis of realistic microstructures 49
3 Synthesis of realistic mineral microstructures for DEM simulations 51
3.1 Development of a computer-assisted QMA for the analysis of real and synthetic
mineral microstructures . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
3.1.1 Fundamentals of the computer-assisted QMA . . . . . . . . . . . . 53
3.1.2 The requirements for the false-color image. . . . . . . . . . . . . . 54
3.1.3 The conversion of a given real mineral microstructure into a false-color
image . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
3.1.4 Implementation of the point, line, and area analysis . . . . . . . . . 59
3.1.5 Selection of appropriate QMA parameters for analyzing two-dimensional
microstructures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
3.1.6 Summary of the principles of the adapted Quantitative Microstructural
Analysis (QMA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
3.2 Analysis of possible strategies for the microstructure synthesis . . . . . . . . 71
3.3 Implementation of the drawing method . . . . . . . . . . . . . . . . . . . . 76
3.3.1 Drawing of a single grain . . . . . . . . . . . . . . . . . . . . . . . 77
XVIII List of Greek Symbols
3.3.2 Drawing of multiple grains, which form a synthetic microstructure . . 81
3.3.3 Synthesizing mineral microstructures consisting of multiple phases . 85
3.4 The final program for microstructure analysis and synthesis . . . . . . . . . 89
3.4.1 Synthesis and analysis of an example microstructure . . . . . . . . . 90
3.4.2 Procedure for generating a realistic synthetic microstructure of a given
real microstructure . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
4 Validation of the synthesis approach 103
4.1 Methodical considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
4.1.1 The basic idea of the validation procedure . . . . . . . . . . . . . . 103
4.1.2 The experimental realizations . . . . . . . . . . . . . . . . . . . . . 108
4.2 Basic indenter test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
4.2.1 Considerations for the basic indenter test . . . . . . . . . . . . . . . 109
4.2.2 Realization and evaluation of the real basic indenter test . . . . . . . 114
4.2.3 Realization and evaluation of the simulated basic indenter test . . . 127
4.2.4 Conclusions on the basic indenter test . . . . . . . . . . . . . . . . . 138
4.3 Extended indenter test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
4.3.1 Basic considerations for the extended indenter test . . . . . . . . . . 139
4.3.2 Realization and evaluation of the real extended indenter test . . . . 142
4.3.3 Realization and evaluation of the simulated extended indenter test . 154
4.3.4 Conclusions on the extended indenter test . . . . . . . . . . . . . . 171
4.4 Particle bed test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172
4.4.1 Basic considerations for the particle bed test . . . . . . . . . . . . . 173
4.4.2 Realization and evaluation of the real particle bed test . . . . . . . . 176
4.4.3 Realization and evaluation of the simulated particle bed test . . . . . 188
4.4.4 Conclusions on the particle bed test . . . . . . . . . . . . . . . . . . 203
5 Conclusions and directions for future development 205
6 References 211
List of Figures 229
List of Tables 235
Appendix 237
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[en] A NUMERICAL STUDY OF THE INFLUENCE OF MECHANICAL PROPERTIES OF DISCONTINUITIES IN THE BEHAVIOUR OF TUNNELS: A CASE STUDY IN THE SOUTHEAST REGION / [pt] UM ESTUDO NUMÉRICO DA INFLUÊNCIA DE PROPRIEDADES MECÂNICAS DE DESCONTINUIDADES NO COMPORTAMENTO DE TÚNEIS: ESTUDO DE CASO NA REGIÃO SUDESTECARLOS RODOLFO BELLEZA VILLAFUERTE 01 July 2020 (has links)
[pt] Esta dissertação tem como objetivo principal estudar o comportamento mecânico de um túnel, especificamente avaliando a degradação do maciço rochoso escavado de gnaisse ao longo do tempo, como se tem na região Sudeste do Rio de Janeiro. A maior cobertura da escavação subterrânea atinge a uma profundidade de 300m., com o um grau de alteração dos minerais da rocha escavada, seccionada por três famílias de descontinuidades que são de maior importância geológica com o potencial risco ao desabamento. Além disso, se avaliaram os cenários, em condições muito persistentes e moderadamente persistentes, com a finalidade de observar sua influência na estabilidade do túnel. Também foi avaliado o comportamento do maciço para três cenários de tensões in situ, K0= 1 (Condições Hidrostáticas), K0= 0.5 e K0= 1.5. Nas análises foram considerados a escavação com e sem elementos de suporte. Os suportes do maciço rochoso nas análises foram com concreto projetado com fibras metálicas (CPRF), reforço de cabos e a mistura dos dois. A análise numérica bidimensional da estabilidade da escavação, para os diferentes casos mencionados, foi feita utilizando o Método dos Elementos Discretos (MED), através do software comercial UDEC (Itasca, 2011). Nas análises dos mecanismos de ruptura com valores de deslocamentos cisalhantes máximos, foi observado que os efeitos do comportamento cisalhante do maciço são maiores na medida em que o ângulo de atrito vai diminuindo, tendo uma importante incidência na sua estabilidade o grau de persistência. Estes resultados mostram índices capazes de prever o comportamento de instabilidade da escavação para estes casos desenvolvidos. / [en] This thesis has the main objective to study the mechanical behavior of a tunnel, specifically assessing the degradation of gneiss rock mass excavated over time, as it has in the South-east region of Rio de Janeiro. The cover of the underground excavation reaches the depth of 300m. with a degree of alteration of minerals of the excavated rock, sectioned by three families of discontinuities that are of most geological importance with the potential risk of collapse. Moreover, scenarios are evaluated in conditions very persistent and moderately with the purpose of observing their influence on the stability of the tunnel. It was also rated the rock mass behavior for three scenarios of in situ stresses, K0= 1 (Conditions Hydrostatic), K0= 0.5 and K0= 1.5. In the analysis were considering the excavation with and without support elements. The supports of the rock mass in the analysis were with shotcrete with steel fibers (CPRF), reinforcement cable bolts and mixing the two. Two-dimensional numerical analysis of the stability of the excavation for the different cases mentioned was made using the Method of Discrete Elements (DEM) through the commercial software UDEC (Itasca, 2011). In the analysis of failure mechanisms with maximum shear displacement values, it was observed that the effects of mass shear behavior are larger in as far as than the friction angle decreases, with an important effect on their stability the degree of persistence. These results show indexes able to predict the behavior of instability of the excavation for these cases developed.
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