Dissertations / Theses on the topic 'Fractured rock massif'

Les glissements de terrain représentent des phénomènes extrêmement dangereux, influencés par divers paramètres et critères fréquemment observés dans différents endroits dans le monde. Leur gestion se révèle complexe, d'autant plus s'ils sont localisés en milieu urbain, en raison des risques qu'ils présentent pour la population et les habitations, ainsi que de la difficulté des mesures correctives à mettre en place. Cette thèse se concentre sur l'étude des glissements de terrain appliquée à la ville d'Al Hoceima, au nord du Maroc. L'objectif est d'analyser leurs origines ou leur réactivation, les facteurs prédisposants qui les déclenchent, et de comprendre les mécanismes en jeu.Pour relever ce défi, une méthodologie basée sur l'analyse des mouvements de terrain à travers une approche pluridisciplinaire, combinant géologie, hydrogéochimie et géotechnique, s'est avérée essentielle. L'analyse du versant étudié révèle une morphologie complexe, résultant d'une géologie caractérisée par une activité tectonique et une lithologie souvent altérée. Du point de vue géotechnique, cela se traduit par des caractéristiques mécaniques variant de faibles à moyennes, et qui diminuent encore sous l'effet de l'action de l'eau. L'activité tectonique intense a engendré des failles et des fractures qui ont structuré le versant, créant des structures en blocs qui fragilisent davantage le terrain. Les mesures inclinométriques ont permis de localiser les plans de glissement à des profondeurs moyennes comprises entre 15 mètres et 25 mètres. Ces mesures ont également révélé des déplacements relatifs des blocs pendant les mouvements. L'analyse chimique des eaux souterraines indique la présence de sulfates de sodium, parfois mêlés à du chlorure de sodium, témoignant d'un lessivage des formations autochtones (Trias-Lias et Jurassique), aggravé par l'influence de la nappe phréatique montante. De plus, les eaux usées, représentant des volumes additionnels, viennent encore perturber l'équilibre du versant en s'infiltrant depuis la surface, comme en témoigne la détection de nitrates dans les eaux analysées.Ces résultats ont motivé la réalisation de simulations visant à approfondir la compréhension des mécanismes des glissements de terrain. Un modèle prenant en compte les discontinuités géologiques et analysant les déformations, les déplacements et les frottements dans les fractures a été utilisé, en se focalisant principalement sur les zones sujettes aux glissements. Cette modélisation a confirmé les conclusions tirées de la phase analytique de l'étude tout en permettant de planifier des actions correctives
Landslides represent highly hazardous phenomena influenced by various parameters and criteria commonly observed in different locations worldwide. Managing them proves challenging, especially in urban areas, due to the risks they pose to the population and structures, as well as the complexities involved in implementing corrective measures. This thesis focuses on landslide studies applied to the city of Al Hoceima in northern Morocco. The objective is to analyze their origins or reactivation, the predisposing factors triggering them, and to understand the mechanisms at play.To tackle this challenge, a methodology based on analyzing ground movements through a multidisciplinary approach, incorporating geology, hydrogeochemistry, and geotechnics, proved essential. The analysis of the studied slope reveals a complex morphology resulting from geology characterized by tectonic activity and often-altered lithology. Geotechnically, this translates into mechanical characteristics ranging from weak to moderate, further decreasing under the influence of water. Intense tectonic activity has resulted in faults and fractures that have structured the slope, creating block structures that further weaken the terrain. Inclinometric measurements localized sliding planes at average depths ranging from 15 meters to 25 meters. These measurements also revealed relative movements of blocks during sliding. Chemical analysis of groundwater indicates the presence of sodium sulfates, occasionally mixed with sodium chloride, indicating leaching of autochthonous formations (Triassic-Liassic and Jurassic), exacerbated by the influence of the rising water table. Additionally, wastewater, constituting additional volumes, further disrupts the slope's equilibrium by infiltrating from the surface, as evidenced by the detection of nitrates in the analyzed waters.These results prompted the implementation of simulations to deepen the understanding of landslide mechanisms. A model considering geological discontinuities and analyzing deformations, displacements, and friction within fractures was employed, primarily focusing on landslide-prone areas. This modeling confirmed the conclusions drawn from the analytical phase of the study while facilitating the planning of corrective actions

Stability analysis of rock masses composed of small, discrete rock blocks that are in-place and interlocked should consider four components of failure: (1) Sliding between blocks. (2) Shearing through rock blocks. (3) Rolling blocks in a shear zone. (4) Crushing of rock blocks. Statistical rock mass description is used to define the characteristics of the rock blocks and the block assemblage. Clastic mechanics is one method of predicting stresses produced by the arrangement of rock blocks and the loading conditions. Failure begins at a point of maximum stress behind the slope. Progression of the failure is assumed if the first block fails because adjacent blocks will become overstressed. The location of the point of maximum stress is determined from the shape and arrangement of the constituent rock blocks. Because strength is mobilized block-by-block rather than instantaneously along a continuous shear surface, sliding between blocks shows less stability than a soil rotational shear analysis or a rigid block sliding analysis. Shearing through rock blocks occurs when maximum shear stress exceeds rock shear strength. Crushing of rock blocks is predicted if the normal stress exceeds the compressive strength of the rock block. A size-strength relationship is combined with the rock block size distribution curve to estimate crushing strength. Rotating blocks in a shear zone have been observed in model studies and as a mechanism in landslides. Stability analysis assumes that the rock mass is sufficiently loosened by blasting and excavation to allow blocks to rotate. The shear strength of rolling blocks is dynamic shear strength that is less than static sliding shear strength. This rolling mechanism can explain release of slope failures where there are no other obvious structural controls. Stability of each component of rock mass failure is calculated separately using capacity-demand reliability. These results are combined as a series-connected system to give the overall stability of the rock mass. This probability of failure for the rock mass system explicitly accounts for the four components of rock mass failure. Criteria for recognizing rock mass failure potential and examples applying the proposed method are presented.

In this thesis, fractured rock masses are treated asequivalent continua for large-scale analyses of rockengineering projects. Systematic developments are made for thedetermination of equivalent mechanical and hydraulic propertiesof fractured rock masses using a hybrid discrete fracturenetwork - distinct element method (DFN-DEM) approach. Thedetermined equivalent properties are then used for a far-fieldfinite element analysis of the thermo-mechanical impacts on thestress, deformation and permeability of fractured rockssurrounding a hypothetical geological repository of nuclearwaste. The geological data were extracted from the results ofan extensive site investigation programme at Sellafield, UK,conducted by Nirex UK Ltd.

The scale dependencies of the hydraulic and mechanicalproperties were investigated by using multiple realizations ofthe fracture system geometry with increasing model sizes untilproperly defined hydraulic and mechanical representativeelementary volumes (REVs) were reached. The validity of thesecond order permeability tensor and the fourth-ordermechanical compliance tensor were tested for continuum analysesat larger scales. The REV was determined to be around 5 m formechanical and hydraulic data in this study.

Analysis of the stress-dependent mechanical and hydraulicproperties shows that the effect of rock stresses is crucial.The elastic moduli increase significantly with the increase ofstress and an empirical equation of stress-dependent elasticmodulus is suggested based on results of numerical experiments.Calculations of the Poisson's ratios suggest greater valuesthan are normally assumed in practice. Depending on the stateof stress, permeability decreases or increases with increasingcompressive stress. Stress-induced flow channeling effect iscaptured by numerical modeling for the first time and detailedmechanisms of shear dilation of fractures are provided. Basedon the numerical experiments, a set of empirical equations wassuggested for the stress-dependent permeability, consideringboth normal deformation and shear dilation of fractures.

Thermo-mechanical impact on the performance of ahypothetical repository at a far-field scale (5 km by 1 km) wasinvestigated with the stress-dependent equivalent propertiesdetermined at the REV scale. This analysis shows thatmechanical responses vary significantly depending on how themechanical properties were determined. The change ofpermeability due to the thermal loading is, however, notsignificant in this particular case.

The thesis provides a framework for systematic analysis oflarge-scale engineering applications in fractured rock masses,such as geological repositories of nuclear wastes.

Keyword:Fractured rock masses, Equivalent Continuum,Discrete Fracture Network (DFN), Distinct Element Method (DEM),Finite Element Method (FEM), Nuclear Waste Disposal, CoupledThermo-Hydro-Mechanical Processes

COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
O presente trabalho apresenta aplicações das técnicas de Relaxação Dinâmica e Análise Limite ao estudo da estabilidade de maciços rochosos fraturados. O maciço é modelado como um meio descontínuo formado por blocos rígidos com deformação concentrada nas juntas. A técnica de Relaxação Dinâmica é usada para a solução do problema de equilíbrio resultante, através do programa BLOCO. As expressões desenvolvidas para a matriz de rigidez tangente, usando o modelo de Barton & Bandis, foram implementadas no programa BLOCO. Exemplos para a validação do algoritmo são apresentados. A partir do trabalho de Faria (1992), foi implementado um procedimento automatizado e otimizado para a solução do problema de Análise Limite em um meio formado por blocos rígidos. O procedimento desenvolvido permitiu a solução de problemas de porte relatados na literatura.
This work presents some applications of the Dynamic Relaxation and Limit Analysis techniques, to the study of the stability of fractured rock masses. Rock mass is modeled as a discontinuum formed by rigid blocks with deformable joints. Dynamic Relaxation was applied to solve the resulting equilibrium problem, using the program BLOCO. Expressions obtained for tangent stiffness matrix, derived from Barton & Bandis model, were implemented into the BLOCO program. In order to extend Faria`s (1992) work, an automatic and optimized procedure, to solve the Limit Analysis problem of a media formed by rigid blocks was implemented. The developed procedure was applied to the study of relatively large dimensions problems, reported in the literature.
Este trabajo presenta aplicaciones de las técnicas de Relajación Dinámica y Análisis Límite al estudio de la estabilidad de macizos rocosos fracturados. EL macizo es modelado como un medio discontinuo formado por bloques rígidos con deformación concentrada en las juntas. La técnica de Relajación Dinámica se utiliza para resolver el problema de equilíbrio resultante, a través del programa BLOQUE. Las expresiones desarrolladas para la matriz de rígidez tangente, usando el modelo de Barton & Bandis, se implementaron en el programa BLOQUE. Se presentan algunos ejemplos para la evaluación del algoritmo. A partir del trabajo de Faria (1992), fue implementado un procedimiento automatizado y optimizado para la solución del problema de Análisis Límite en un medio formado por bloques rígidos. El procedimiento desarrollado permitió resolver problemas de porte relatados en la literatura.

L’étude des phénomènes couplés thermo-hydro-mécaniques intéresse la communauté scientifique aujourd'hui confronté au problème du stockage des déchets. La modélisation est un outil essentiel pour prédire l'évolution complexe du milieu hôte et de ces déchets. Parmi les approches numériques existants, on distingue les approches de types éléments finis et les approches de type éléments distincts. Si la première, plus ancienne, a déjà donné lieu à de nombreux développement et applications, elle rend mal quelquefois la réalité du massif rocheux fracturé. Nous avons souhaité cette dernière approche en la rendant capable de modéliser les échanges thermiques convectifs liés à la circulation d'un fluide dans les fissures de roche. Nous suspectons en effet que ce phénomène peut être important si le gradient hydraulique est suffisamment élevé. Une étude bibliographique nous a permis de mettre en évidence les paramètres qui déterminent ce phénomène dont le principal est le coefficient de transfert thermique h entre la roche et le fluide. Les nombreuses formulations recensées ne sont pas totalement suffisantes à expliciter la réalité de ses effets. D’autres mesures, in situ et en laboratoire, s'avèrent nécessaires. Nous avons pu établir des expressions pour les termes d'échange thermique entre le fluide et la roche et à l'intérieur du fluide lui-même. Souhaitant donc modéliser le phénomène à l'aide d'une approche adaptée au milieu discontinu, notre choix s'est porte sur le logiciel UDEC (Universal Distinct Element Code) dont la structure permettait moyennant quelques modifications d'accueillir les développements envisagés. Les algorithmes de calcul sont basés sur les différences de vitesse entre les transferts thermiques convectifs et conductifs. Nous avons testé notre modèle dans le cas de l'écoulement d'un fluide froid entre 2 blocs. Dans le cas d'une modélisation thermohydraulique, les échanges thermiques calculés sont cohérents et s'accordent avec ceux calculés par une autre approche numérique. On observe en effet que la convection thermique croit avec l'ouverture hydraulique de la fracture, la vitesse du fluide et décroit avec sa viscosité. Des calculs thermo-hydromécaniques ont montré la nécessité d'alterner les calculs thermiques et les calculs hydromécaniques suffisamment fréquemment pour rendre compte de la réalité du couplage. Notre modèle a été utilisé à grande échelle et a permis également d'interpréter les anomalies thermiques mesurées sur le site géothermal du Cézallier

In this thesis, the effects of size and stress on permeability, deformability and strength of fractured rock masses are investigated. A comparison study was carried out to examine the effects of considering, or not considering, the correlation between distributions of fracture apertures and fracture trace lengths on the hydro-mechanical behavior of fractured rocks. The basic concepts used are the fundamental principles of the general theory of elasticity, Representative Elementary Volume (REV), the tensor of equivalent permeability, and the strength criteria of the fractured rocks. Due to the size and stress dependence of the hydro-mechanical properties of rock fractures, the overall effective (or equivalent) hydro-mechanical properties of the fractured rocks are also size and stress-dependent. However, such dependence cannot be readily investigated in laboratory using small samples, and so numerical modeling becomes a necessary tool for estimating their impacts. In this study, a closed-form relation is established for representing the correlation between a truncated lognormal distribution of fracture apertures and a truncated power law distribution of trace lengths, as obtained from field mapping. Furthermore, a new nonlinear algorithm is developed for predicting the relationship between normal stress and normal displacement of fractures, based on the Bandis model and the correlation between aperture and length. A large number of stochastic Discrete Fracture Network (DFN) models of varying sizes were extracted from some generated large-sized parent realizations based on a realistic fracture system description from a site investigation programme at Sellafield, UK, for calculating the REV of hydro-mechanical properties of fractured rocks. Rotated DFN models were also generated and used for evaluation of the distributions of directional permeabilities, such that tensors of equivalent permeability could be established based on stochastically established REVs. The stress-dependence of the permeability and the stress-displacement behaviour were then investigated using models of REV sizes. The Discrete Element Method (DEM) was used for numerical simulation of the fluid flow, deformability properties and mechanical strength behavior of fractured rocks. The results show significant scale-dependency of rock permeability, deformability and strength, and its variation when the correlation between aperture and trace length of fractures are concerned, with the overall permeability and deformability more controlled by dominating fractures with larger apertures and higher transmissivity and deformability, compared with fracture network models having uniform aperture. As the second moment of aperture distribution increases, a fractured rock mass shows more discrete behavior and an REV is established in smaller value of second moment with much larger model size, compared with the models with uniform fracture aperture. When the fracture aperture pattern is more scattered, the overall permeability, Young’s modulus and mechanical strength change significantly. The effect of stress on permeability and fluid flow patterns in fractured rock is significant and can lead to the existence or non-existence of a permeability tensor. Stress changes the fluid flow patterns and can cause significant channeling and the permeability tensor, and REV may be destroyed or re-established at different applied stress conditions. With an increase in the confining stress on the DEM models, the strength is increased. Compared with the Hoek-Brown criterion, the Mohr-Coulomb strength envelope provides a better fit to the results of numerical biaxial compression tests, with significant changes of the strength characteristic parameters occurring when the second moment of the aperture distribution is increased.
QC 20100702

Un massif rocheux fracturé, dont le comportement géo-hydromécanique a été étudié depuis plusieurs années, a été instrumenté sismiquement. L'intérêt du site réside dans le fait qu'on peut induire artificiellement une charge hydraulique connue et mesurer des déplacements, des pressions hydrauliques sur plusieurs points significatifs. Les résultats des essais in-situ mettent en évidence l'existence d'une micro-sismicité induite par une variation de pression avec une grande repétitivité. A partir des résultats des essais in-situ, a été formulée l'hypothèse que l'activité micro-sismique est associée à l'augmentation de la pression d'eau dans les zones moins perméables du massif rocheux. Une modélisation numérique du site avec la méthode des Eléments Finis a été réalisée pour determiner l'amplitude des variations de contraintes induites par la mise en charge hydraulique et vérifier si elles pouvaient engendrer des sources sismiques. Des échantillons prélevés ont permis de déterminer, en laboratoire, le comportement mécanique de la roche intacte et des joints rocheux et la sismicité associée. Il s'avère que les variations de contrainte calculées pour le site ne sont pas suffisantes pour générer la sismicité observée au laboratoire. Une modélisation micromécanique à l'échelle du joint rocheux avec la méthode des Eléments de Contour (Discontinuités de Déplacement) a été réalisée pour simuler le comportement hydro-mécanique tenant compte de la morphologie du joint. Les résultats numériques sont en accord avec les obsenTations de laboratoire et montrent que la mise en charge hydraulique d'un joint rugueux peut engendrer des instabilités lors de l'ouverture des aires de contact compatibles avec la micro-sismicité observée sur le site
This dissertation forms part of a larger research field which deals with using seismic monitoring systems to better understand the behavior of natural rock slope appealing to the laboratory and in-situ experiments and the numerical simulation. For this purpose, a small scale rock mass, former instrumented from the geo-hydro-mechanical point of view, bas been chosen for installing a seismic monitoring system. Ln this site, it is possible to easily induce a known hydraulic charging and to measure displacements and pressures in many meaningful points. The results of the in-situ experiments highlight the existence of micro-seismicity induced by a variation of water pressures and the repetitiveness either of the hydro-mechanical and micro-seismic behavior. From results, it bas been hypothesized that the micro-seismic activity onsets when water pressure increases in less permeable zones. The Finite Elements numerical modeling of the site allows to calculate the stress variations due to hydraulic charging and to assess if stress variations could generate seismic sources. Series of cores have been taken from the site in order to tested rock material and rock fractures in laboratory, associated with acoustic emissions. Lt results that little stress variations due to water pressure, calculated for the site, do not explain the micro-seismicity observed in laboratory. A micro-mechanical model using Boundary Elements Method (Displacements Discontinuity Method) which simulates the hydro-mechanical behaviour of rock joints sample under normal compression is proposed taking into account the joint topography. Results confirm the laboratory observations and show that the hydrostatic charging can induce instabilities, when contact areas open, comparable to the ill-situ micro-seismicity

Numerical modelling of rock slopes can involve a number and variety of techniques, the selection and requirement of which depends on the factors deemed to control the potential for Instability. This thesis presents a number of case studies involving slopes in fractured rock, encompassing a range of scales. The case study slopes have provided a means to question the way in which particular slope instabilities should be analysed. Currently there are few methods available for analysing the complex behaviour within slopes of fractured rock. A review of available techniques is given within this thesis, with the use of limit equilibrium, finite element and hybrid methods, to highlight their specific advantages and limitations for the chosen case study slopes. By modelling slope Instability within fractured rock, the understanding of both discrete and mass behaviour increases considerably. Numerical modelling can therefore be used as a tool to help improve both the safety and efficiency of open pit mining and the management of natural rock slopes.

Two new three-dimensional rock mass strength criteria are developed in this dissertation by extending an existing rock mass strength criterion. These criteria incorporate the effects of the intermediate principal stress, minimum principal stress and the anisotropy resulting from these stresses acting on the fracture system. In addition, these criteria have the capability of capturing the anisotropic and scale dependent behavior of the jointed rock mass strength by incorporating the effect of fracture geometry through the fracture tensor components. Another significant feature of the new rock mass strength criterion which has the exponential functions (equation 6.7) is having only four empirical coefficients compared to the existing strength criterion which has five empirical coefficients; if the joint sets have the same isotropic mechanical behavior, the number of the empirical coefficients reduces to two in this new strength criterion (equation 6.10). The new criteria were proposed after analyzing 452 numerical modeling results of the triaxial, polyaxial and biaxial compression tests conducted on the jointed rock blocks having one or two joint sets by the PFC3D software version 5. In this research to have several samples with the same properties a synthetic rock material that is made out of a mixture of gypsum, sand and water was used. In total, 20 joint systems were chosen and joint sets have different dip angles varying from 15 to 60 at an interval of 15 with dip directions of 30 and 75 for the two joint sets. Each joint set also has 3 persistent joints with the joint spacing of 42 mm in a cubic sample of size 160 mm and the joints have the same isotropic mechanical behavior. The confining stress combination values were chosen based on the uniaxial compressive strength (UCS) value of the modeled intact synthetic rock. The minimum principal stress values were chosen as 0, 20, 40 and 60 percent of the UCS. For each minimum principal stress value, the intermediate principal stress value varies starting at the minimum principal stress value and increasing at an interval of 20 percent of the UCS until it is lower than the strength of the sample under the biaxial loading condition with the same minimum principal stress value. The new rock mass failure criteria were developed from the PFC3D modeling data. However, since the joint sets having the dip angle of 60 intersect the top and bottom boundaries of the sample simultaneously, the joint systems with at least one of the joint sets having the dip angle of 60 were removed from the database. Thus, 284 data points from 12 joint systems were used to find the best values of the empirical coefficients for the new rock mass strength criteria. λ, p and q were found to be 0.675, 3.16 and 0.6, respectively, through a conducted grid analysis with a high R2 (coefficient of determination) value of 0.94 for the new criterion given by equation 6.9 and a and b were found to be 0.404 and 0.972, respectively, through a conducted grid analysis with a high R2 value of 0.92 for the new criterion given by equation 6.10. The research results clearly illustrate how increase of the minimum and intermediate principal stresses and decrease of the joint dip angle, increase the jointed rock block strength. This dissertation also illustrates how different confining stress combinations and joint set dip angles result in different jointed rock mass failure modes such as sliding on the joints, failure through the intact rock and a combination of the intact rock and joint failures. To express the new rock mass strength failure criteria, it was necessary to determine the intact rock strengths under the same confining stress combinations mentioned earlier. Therefore, the intact rock was also modeled for all three compression tests and the intact rock strengths were found for 33 different confining stress combinations. Suitability of six major intact rock failure criteria: Mohr-Coulomb, Hoek-Brown, Modified Lade, Modified Wiebols and Cook, Mogi and Drucker-Prager in representing the intact rock strength was examined through fitting them using the aforementioned 33 PFC3D data points. Among these criteria, Modified Lade, Modified Mogi with power function and Modified Wiebols and Cook were found to be the best failure criteria producing lower Root Mean Square Error (RMSE) values of 0.272, 0.301 and 0.307, respectively. Thus, these three failure criteria are recommended for the prediction of the intact rock strength under the polyaxial stress condition. In PFC unlike the other methods, macro mechanical parameters are not directly used in the model and micro mechanical parameter values applicable between the particles should be calibrated using the macro mechanical properties. Accurate calibration is a difficult or challenging task. This dissertation emphasized the importance of studying the effects of all micro parameter values on the macro mechanical properties before one goes through calibration of the micro parameters in PFC modeling. Important effects of two micro parameters, which have received very little attention, the particle size distribution and the cov of the normal and shear strengths, on the macro properties are clearly illustrated before conducting the said calibration. The intact rock macro mechanical parameter values for the Young’s modulus, uniaxial compression strength (UCS), internal friction angle, cohesion and Poisson's ratio were found by performing 3 uniaxial tests, 3 triaxial tests and 5 Brazilian tests on a synthetic material made out of a mixture of gypsum, sand and water and the joint macro mechanical parameter values were found by conducting 4 uniaxial compression tests and 4 direct shear tests on jointed synthetic rocks with a horizontal joint. Then the micro mechanical properties of the Linear Parallel Bond Model (LPMB) and Modified Smooth Joint Contact Model (MSJCM) were calibrated to represent the intact rock and joints respectively, through the specific procedures explained in this research. The similar results obtained between the 2 polyaxial experiments tests of the intact rock and 11 polyaxial experimental tests of the jointed rock blocks having one joint set and the numerical modeling verified the calibrated micro mechanical properties and further modification of these properties was not necessary. This dissertation also proposes a modification to the Smooth Joint Contact Model (SJCM) to overcome the shortcoming of the SJCM to capture the non-linear behavior of the joint closure varying with the joint normal stress. Modified Smooth Joint Contact Model (MSJCM) uses a linear relation between the joint normal stiffness and the normal contact stress to model the non-linear relation between the joint normal deformation and the joint normal stress observed in the compression joint normal stiffness test. A good agreement obtained between the results from the experimental tests and the numerical modeling of the compression joint normal test shows the accuracy of this new model. Moreover, another shortcoming associated with the SJCM application known as the interlocking problem was solved through this research by proposing a new joint contact implementation algorithm called joint sides checking (JSC) approach. The interlocking problem occurs due to a shortcoming of the updating procedure in the PFC software related to the contact conditions of the particles that lie around the intended joint plane during high shear displacements. This problem increases the joint strength and dilation angle and creates unwanted fractures around the intended joint plane.

The study of hydro-mechanical (HM) coupled problems in different areas of civil, environmental or petroleum engineering is common in literature, but the effect of a thermal field by means of the heat transport by a fluid through the discontinuities is not considered in the current tools of analysis, in which the effect of the temperature gradient between the fluids flowing through the discontinuities and the in-situ thermal state are not considered. In geomechanics modeling it is important to distinguish between the hydraulic behavior of the porous medium and that of the discontinuities, together generating a double-permeability system where the discontinuities establish preferential flow paths. Because of high hydraulic velocities in the discontinuities, the advection (transport) may be the dominant heat transfer mode. Thus, the study of THM coupled processes with thermal advection in discontinuities is important in problems with a certain degree of coupling between the mechanical, hydraulic and thermal fields, and in which the hydraulic flow transports heat through the discontinuities. It is important to establish a numerical model to study the advection phenomena that differentiates the discontinuity network and the porous medium contributions. In this context, this thesis focuses on the study, formulation, numerical implementation and verification of a THM fully-coupled model with large advection, able to reproduce the advective behaviour that occurs in discontinuities, in which heat is transported by the fluid. This numerical approach is carried out using the finite element method (FEM) with zero-thickness interface elements to represent the discontinuities, and assuming saturated conditions and a single incompressible fluid (constant density). It is also assumed that all the non-linear behaviour occurs at the interface elements by means of an elasto-plastic constitutive law based on fracture mechanics. Additionally, the numerical approach to the thermal advection presents a singularity in comparison with pure diffusive problems. If the fluid velocities are low, the numerical formulation can be made by traditional FEM (Galerkin). However, when the fluid velocities are high and the advection dominates the problem, the standard Galerkin weighting leads to oscillatory results, and the advective term requires a special treatment to stabilize the numerical solution. A review of different methodologies to solve the large advective problem is presented, selecting the Streamline Upwind Petrov-Galerkin method to solve the steady-state. For transient states, this thesis starts with the study of the existing explicit Characteristic Galerkin Method (CGM), which studies the advective phenomena in a Lagrangian manner, following the particle (or heat) with the fluid by setting a moving coordinate system that depends on the fluid velocity and its position in time. Then the implicit CGM is developed, and finally a new variation is proposed adding a parameter alpha that allows determining different temporal derivative positions of the advective volume, leading to the alpha-Implicit CGM, that allows to obtain stable solutions if the Courant condition is fulfilled. In order to verify the THM model with large advection for continuum medium and zero-thickness interfaces, several simple verification examples are presented. Finally, an application to hydraulic fracture (HF) with a single fracture in 2-D is introduced in order to understand the thermal mechanisms that occur in HF problems and how they affect the mechanical and hydraulic fields. In addition, these results are compared with those obtained using the HM model, where the thermal field is not considered. Finally, in order to improve the computational capacities of the FEM code, its parallelization has performed following a subdomain decomposition strategy, leading to a substantial improvement in the speed of the calculations and showing a good degree of scalability.
El estudio de problemas hydro-mecánicos (HM) acoplados en diferentes áreas de ingeniería civil, ambiental o del petróleo es común en la literatura, pero los efectos térmicos del fluido transportando calor a través de fracturas o discontinuidades no se considera en las actuales herramientas de análisis, en las cuales el efecto de la diferencia de temperatura entre el fluido inyectado a través de las discontinuidades y la del medio in situ no se tiene en cuenta. No obstante, en algunos problemas geomecánicos los comportamientos mecánico, hidráulico y térmico del medio poroso fracturado pueden aparecer acoplados con fuertes interacciones entre ellos. En modelación geomecánica es importante distinguir el comportamiento hidráulico del medio poroso del de las discontinuidades, ambas generando un sistema de doble permeabilidad en el cual el medio poroso proporciona una pequeña permeabilidad al sistema, mientras que las discontinuidades establecen caminos preferentes y proporcionan gran permeabilidad al mismo. Debido a las elevadas velocidades de fluido que se pueden desarrollar en las discontinuidades, la advección (transporte) puede ser el modo dominante de transferencia de calor. Por ello, el estudio de procesos THM acoplados con advección térmica en discontinuidades es importante en problemas con un cierto grado de acoplamiento entre los campos mecánico, hidráulico y térmico, y en los cuales el flujo hidráulico puede transportar calor a gran velocidad a través de las discontinuidades. Por ello, es importante establecer un modelo numérico para estudiar el fenómeno advectivo que diferencie la contribución de la red de discontinuidades de la del medio continuo poroso. En este contexto, esta tesis está enfocada en el estudio, formulación, implementación numérica y verificación de un modelo THM acoplado monolítico con advección dominante que sea capaz de reproducir el comportamiento advectivo que ocurre en discontinuidades o fracturas, en las cuales el fluido transporta calor. Este estudio se lleva a cabo en el contexto geomecánico de un medio poroso fracturado, empleando el método de los elementos finitos (FEM) con elementos junta de espesor nulo para representar las discontinuidades o fracturas, suponiendo condiciones saturadas, un único fluido incompresible (con densidad constante) y pequeñas deformaciones. También se supone que todo el comportamiento no lineal se desarrolla en las juntas mediante el uso de una ley constitutiva elasto-plástica basada en mecánica de fractura, mientras que el medio continuo poroso se supone de comportamiento poro-elástico. Adicionalmente, la solución numérica del problema térmico advectivo presenta singularidades con respecto a los problemas de difusión pura. Cuando las velocidades del fluido son bajas, la formulación numérica se puede llevar a cabo mediante Elementos Finitos tradicionales (Galerkin). No obstante, cuando las velocidades del fluido son suficientemente elevadas y la advección domina el problema el método estándar de Galerkin conduce a resultados oscilantes, por lo que el término advectivo requiere un tratamiento especial para estabilizar la solución numérica. En este contexto, se presenta una revisión de diferentes metodologías para resolver el problema de advección dominante, seleccionando el método Streamline Upwind Petrov-Galerkin (SUPG) para resolver el problema en régimen permanente, un método bien conocido que conduce a soluciones estables con advección dominante. Para el régimen transitorio esta tesis empieza con el estudio del método de Características Galerkin explícito, un método existente en el que el fenómeno advectivo se estudia de modo Lagrangiano, siguiendo la partícula (o calor) con el movimiento del fluido, y estableciendo para ello un sistema de coordenadas móvil que depende de la velocidad del fluido y de su posición en el tiempo. Seguidamente se desarrolla la forma implícita de este método, y finalmente se propone una nueva variación del método, añadiendo un parámetro 𝛼�𝛼� que permite determinar diferentes posiciones de las derivadas temporales del volumen advectivo, concluyendo en el nuevo 𝛼�𝛼�-Implicit Characteristic Galerkin Method. Con esta nueva metodología se estabiliza el problema de gran advección en régimen transitorio si se cumple la condición de Courant. Con el fin de verificar el modelo THM monolítico acoplado con advección dominante se presentan diversos ejemplos de verificación, tanto para medio continuo poroso como para elementos junta de espesor nulo. Finalmente, se presenta un caso de aplicación a fractura hidráulica (HF), llevando a cabo el análisis numérico de una sola fractura en 2-D con el objetivo de entender los mecanismos térmicos que ocurren en problemas de HF y como éstos afectan sobre los comportamientos mecánico e hidráulico. Además, los resultados de la modelación se comparan con los obtenidos empleando un modelo HM, en el cual no se consideran efectos térmicos. Adicionalmente, con el objetivo de mejorar la eficiencia computacional del código de Elementos Finitos, se ha llevado a cabo la paralelización del mismo mediante una estrategia de partición de subdominios, resultando en una mejora sustancial de la velocidad de los cálculos y mostrando una buena escalabilidad de los mismos.

The equivalent continuum approach uses equivalent propertiesof rock mass as the input data for a continuum analysis. Thisis a common modeling method used in the field of rock mechanicsand hydrogeology. However, there are still unresolvedquestions; how can the equivalent properties be determined andis the equivalent continuum approach suitable for modeling thediscontinuous fractured rock mass.

The purpose of this paper is to establish a methodology todetermine the equivalent hydraulic and mechanical properties offractured rock masses by explicit representations of stochasticfracture systems, to investigate the scale-dependency of theproperties, and to investigate the conditions for theapplication of the equivalent continuum approach for thefractured rock masses. Geological data used for this study arefrom the site characterization of Sellafield, Cumbria, UK. Aprogram for the generation of stochastic Discrete FractureNetwork (DFN) is developed for the realization of fractureinformation and ten parent DFN models are constructed based onthe location, trace length, orientation and density offractures. Square models with the sizes varying from 0.25 m× 0.25 m to 10 m × 10 m are cut from the center ofthe each parent network to be used for the scale dependencyinvestigation. A series of the models in a parent network arerotated in 30 degrees interval to be used for investigation oftensor characteristic. The twodimensional distinct elementprogram, UDEC, was used to calculate the equivalentpermeability and compliance tensors based on generalizedDarcy’s law and general theory of anisotropic elasticity.Two criteria for the applicability of equivalent continuumapproach were established from the investigation: i) theexistence of properly defined REV (Representative ElementaryVolume) and ii) existence of the tensor in describing theconstitutive equation of fractured rock The equivalentcontinuum assumption cannot be accepted if any one of the abovetwo criteria is not met. Coefficient of variation and meanprediction error is suggested for the measures toquantitatively evaluate the errors involved in scale dependencyand tensor characteristic evaluation.

Equivalent permeability and mechanical properties (includingelastic modulus and Poisson’s ratios) determined onrealistic fracture network show that the presence of fracturehas a significant effect on the equivalent properties. Theresults of permeability, elastic moduli and Poisson's ratioshow that they narrow down with the increase of scale andmaintain constant range after a certain scales with someacceptable variation. Furthermore, Investigations of thepermeability tensor and compliance tensor in the rotated modelshow that their tensor characteristics are satisfied at acertain scale; this would indicate that the uses of theequivalent continuum approach is justified for the siteconsidered in this study.

The unique feature of the thesis is that it gives asystematic treatment of the homogenization and upscaling issuesfor the hydraulic and mechanical properties of fractured rockswith a unified approach. These developments established a firmfoundation for future application to large-scale performanceassessment of underground nuclear waste repository byequivalent continuum analysis.

Keywords :Equivalent continuum approach, Equivalentproperty, Representative Elementary Volume (REV), DistinctElement Method, Discrete Fracture Network (DFN)

Pour étudier le comportement mécanique des massifs rocheux, en prenant en compte le réseau des discontinuités au sein de la roche intacte, cette recherche a pour objectif la représentation du massif par des modèles géométriques basés sur des relevés de terrain et l'analyse de ces modèles par l'utilisation d'outils informatiques adaptés pour les milieux granulaires. Le premier chapitre fait l'état de l'art des roches fracturées, des méthodes numériques de la mécanique des roches et des approches du calcul de structure d'un tunnel. Ces études conduisent à la proposition d'une méthodologie depuis les recherches in situ jusqu'à la modélisation et l'analyse mécanique, présentée dans le deuxième chapitre. Le massif rocheux est d'abord représenté géométriquement par la distribution de ses discontinuités, et l'utilisation du logiciel RESOBLOK basé sur la méthode du Réseau de Fractures Discrètes. Les modèles mécaniques de massifs rocheux sont ensuite présentés à partir des données sur les études de l'histoire du massif, et des mesures faites sur site et en laboratoire. Les modèles numériques en 3D sont analysés par l'utilisation du logiciel LMGC90 basé sur la méthode de la Dynamique des Contacts Non Réguliers. Les premières applications de la méthodologie sont exposées : la création d'une roche numérique pour simuler un essai de compression triaxiale, et la simulation d'une excavation multi phases d'un tunnel au rocher. La méthodologie proposée a été appliquée sur le marbre blanc de Saint Béat (Haute Garonne, France) et les résultats préliminaires sont donnés dans le chapitre trois. Les réponses mécaniques de la roche numérique sont analysées et son comportement est caractérisé
Aimed at studying the mechanical behaviour of rock mass and considering the presence of the discontinuity network in the intact rock, this research concentrates on how the rock can be represented in suitable geometrical models, on the basis of site measurements, and then appropriately analysed using computer tools developed for the study of granular media. The first chapter deals with a bibliographical study on fractured rock and tunnel engineering. Different computational methods of rock mechanics are introduced. Simultaneously, three principal approaches for tunnel structural design are recalled. These studies lead to the proposition of a methodology from the in situ investigation to in-door modelling and mechanical analysis, presented in the second chapters. The rock mass is first geometrically represented through the distribution of discontinuities in the rock mass and the use of the RESOBLOK code based on the Discrete Fracture Network method. Mechanical models of rock mass are then presented from the data of historical studies on the rock mass and from laboratory and in situ measurements. The 3D computational models are analysed using the LMGC90 based on the Non Smooth Contact Dynamics method. The first two applications of the methodology are introduced: the generation of the numerical rock for the simulation of the triaxial compression test, and the simulation of multi-phase excavation of rock tunnel. The proposed methodology has been applied on the white marble of Saint Béat (Haute Garonne, France) and the initial results are given in the third chapter. The mechanical responses of the numerical rock mass are analysed and the bulk behaviour of the rock is evaluated

Le fonctionnement et la structure hydrogéologiques des aquifères de socle des granites et des gneiss sont aujourd'hui relativement bien compris. En revanche, dans cet ensemble, les aquifères dans les péridotites sont très peu étudiés et mal compris. Dans ce contexte, les massifs obductés de Nouvelle-Calédonie présentent un laboratoire naturel exceptionnel pour améliorer la connaissance de cet hydrosystème original en contexte tropical. Ainsi l'objectif du présent travail de thèse est d'approfondir la connaissance de la structure et du fonctionnement hydrogéologiques de ces massifs. L'analyse porte d’abord sur le manteau d'altération constitué de la cuirasse, des latérites, des saprolites grossières et du saprock. Plus de 60 essais hydrauliques sont menés sur les massifs de péridotites et les résultats sont compilés aux données existantes. La conductivité hydraulique moyenne des latérites est évaluée à 1.10-7 m/s et celle des saprolites grossières et du saprock à 8.10-7 m/s. L'hétérogénéité de cet horizon altéré est marquée par une gamme de variation de la conductivité hydraulique sur six ordres de grandeur et l'analyse piézométrique met en évidence des connexions hydrauliques avec le substratum fracturé profond. Le substratum est ensuite considéré. L'étude de la fracturation est réalisée à partir de mesures structurales sur affleurement et de la description de près de 1000 m de carottes de forages. L'analyse de la fracturation met en évidence l'importance du réseau serpentineux par sa densité d’une part, et par son lien avec l'altération supergène d'autre part. De plus, il est vérifié que la conductivité hydraulique du substratum diminue avec la profondeur. Cette variation est liée à la diminution de la densité de fractures altérées. Ainsi, à l'issue de ces analyses, la structure des massifs de péridotites est définie. Un réseau primaire de fractures d’espacement décimétrique lié au réseau serpentineux préstructure les péridotites. Sur ce réseau se surimpose un réseau de fractures dont l'espacement est décamétrique et caractérisé par une altération supergène. Les fractures altérées présentent localement de fortes conductivités hydrauliques, de l'ordre de 10-5 m/s. En profondeur l'espacement des fractures est hectométrique et les fractures sont majoritairement fermées, scellées par les minéraux néoformés ou par l'effet de la pression lithostatique. Les réseaux de fractures déca et hectométriques, visibles également sur l'effet d’échelle de la conductivité hydraulique, sont majoritairement verticaux, développés par instabilité de dissolution lors des processus d’altération. Cependant, des structures à faible pendage existent également et permettent la percolation du réseau. Enfin, à partir de ces nouveaux résultats et de l’intégration de l'ensemble des données acquises sur les différents massifs, un modèle de structure et de fonctionnement hydrogéologiques est proposé à l'échelle du massif. Ce modèle comprend l'horizon des latérites qui constitue un aquitard homogène sous lequel se développe l'aquifère dont l'épaisseur est de l'ordre de cinquante mètres. Le substratum est discrétisé en trois couches dont la conductivité hydraulique décroît de 2.10-7 à 2.10-8 m/s entre 50 m et 250 m environ sous le mur de l'aquifère. Les modèles numériques construits permettent de valider le modèle conceptuel unitaire et montrent que l'état de saturation des massifs est contraint par leur géomorphologie. Au terme de ce travail, plusieurs aspects doivent encore être approfondis. Le rôle hydrogéologique de la cuirasse doit être précisé et considéré dans le modèle hydrogéologique. Enfin, compte tenu du développement possible de structures très perméables, voire pseudo-karstiques, la connaissance de la distribution des structures drainantes doit être améliorée. Les résultats appliqués de ce travail de recherche sont exposés dans un rapport final et un guide méthodologique livrés dans le cadre du projet CNRT « HYPERK »
Water resources of hard-rock (gneisses or granites) aquifers have significantly been studied in the past two decades. The hydrogeological behavior and structure of these aquifers are thus relatively well understood. On the other hand, aquifers in mantle-type basements, such as peridotites, are poorly studied and understood, mainly because they are not common and of limited extent. In this context, New Caledonia is a great laboratory offering unique opportunity to improve the knowledge of these original types of hydrosystems in tropical climate. Thus, the objective of this thesis is to improve the knowledge of these aquifer systems within weathered peridotites. Firstly, the study focuses on the characterization of the weathered layers of the peridotites composed of, from top to bottom, iron oxides/ferricrete, laterite, coarse saprolite and saprock (ie. top of the bedrock, with up to 20 % of weathered material). More than 60 hydraulic tests are performed and results were compiled with existing data. Mean hydraulic conductivity (K) of laterites is estimated around 1.10-7 m/s while mean value in coarse saprolites and saprock is around 8.10-7 m/s. Heterogeneity of this altered layer is high; K varies between six orders of magnitude and hydraulic head data analysis reveals a hydraulic connection with the deep fractured bedrock. Secondly, the fresh rock part of peridotites is studied. Fracture network analysis is derived from outcrop structural measurements and from the description of about 1000 m of cumulated borehole cores. This work highlights the importance of serpentine network, because of its high density and its critical impact on weathering. Moreover, the observations reveal that hydraulic conductivity decreases with depth within the substratum, due to the vertical decrease of weathered fractures density. These new results allow defining a structural framework of the massifs. It is characterized by a primary decimetrical fracture network closely related to the serpentine network. This network is overprinted by a secondary weathering network which reveals decametric spacing (ca. 30 m) and in places K values of 10-5 m/s. At depth, spacing is hectometrical and fractures are sealed by lithostatic pressure and/or subsequent mineral precipitations. These deca- and hectometric fracture networks, which are also visible on the scale effect of hydraulic conductivity, are primarily vertical and are the result of dissolution instabilities occurring during weathering processes. However, low- angle fractures do occur and allow the percolation of the network. Finally, on the basis of these new results and the integration of all existing data from different massifs a new hydrogeological conceptual model is proposed at the scale of a massif. The model includes a homogeneous lateritic aquitard and a coarse saprolite and saprock aquifer which is about 50 m thick. The bedrock is subdivided into three layers whose hydraulic conductivity decreases from 2.10-7 m/s to 2.10-8 m/s, respectively 50 and 250 m below the aquifer base. Numerical modelling validates this unitary conceptual model and reveals that the saturation of the massifs depends on their morphology. At last, several aspects require further research. The role of the ferricrete layer must be specified and considered in the hydrological model. Moreover, distribution of the fracture network remains to be fully addressed and should be studied with care given the potential development of highly permeable structures that could conform to pseudo-karstic drains. The applied results of this work are available in a “Technical guide” and a “Technical report” of the “HYPERK” CNRT Project

Le comportement mécanique des massifs rocheux fracturés est énormément et quelquefois dramatiquement, affecté par le comportement des discontinuités présentes dans les massifs. L'influence des discontinuités sur le comportement mécanique des masses rocheuses a été démontrée par de nombreuses études expérimentales et numériques. Les joints sont à l’origine des ruptures ou instabilités observées dans les structures du génie civil et leur comportement dépend de nombreux facteurs. Par conséquent, les modèles de comportement des discontinuités et les paramètres associés jouent un rôle essentiel dans les applications des techniques numériques. Un programme permettant de déterminer les paramètres des lois constitutives des discontinuités ainsi que les critères de rupture en cisaillement, à partir des données d'essais en laboratoire, a été mis au point. Saeb et Amadei ont développé un modèle analytique, incrémental et non linéaire de comportement des joints rocheux. Base sur la formulation des auteurs, nous avons généralisé le comportement des joints rocheux à des sollicitations cycliques dans la direction normale et avec changement de direction de sollicitations dans la direction tangente au joint. Les deux modèles ont été implantés dans le code de calcul des éléments distincts UDEC. Une vérification des modèles ainsi qu'une étude paramétrique ont été réalisées sur des géométries simples (y compris les deux lois linéaires de UDEC). Trois exemples d'application à l'étude de l'influence des lois sur la stabilité des ouvrages ont été traités. Les deux premiers étudient l'influence des lois de comportement sur la stabilité d'ouvrages à plusieurs profondeurs ainsi que l'influence de la rigidité du milieu entourant les fractures. Une comparaison entre les résultats de la modélisation (selon les lois constitutives et certains paramètres qu'elles font intervenir dans leur mise en œuvre) et les mesures in situ constituent le troisième exemple

L'etat de fracturation d'un massif cristallin par l'intermediaire de la modelisation est apprehende et passe par des etapes d'acquisition des donnees qui se font en surface et en profondeur, ainsi que par des etapes d'analyse suivant le parametre choisi. L'hydrogeologie des milieux fissures et l'une des applications aux modelisations de champs de fracture. On peut ainsi mettre en evidence un comportement discontinu du flux

Les bactéries de la famille des Gallionellaceae (β-proteobacteria) oxydent le fer dissous à pH neutre pour alimenter leur métabolisme énergétique. Ces bactéries sont endémiques des habitats microaérobies, où elles peuvent rivaliser avec l'oxydation abiotique rapide du fer par l'oxygène. Elles sont ainsi retrouvées généralement dans les zones d’interfaces entre l’atmosphère et un compartiment anoxique riche en fer, tel qu’une résurgence d’eau souterraine. Pourtant ces cinq dernières années, de plus en plus d’études attestent de la présence des Gallionellaceae en profondeur dans certains milieux souterrains, à des profondeurs où ils sont généralement considérés comme anoxiques. Dans plusieurs de ces milieux, comme par exemple certains aquifères du massif armoricain (Bretagne, France), les Gallionellaceae semblent même dominer les communautés microbiennes présentes. Cela suggère que non seulement il existe des zones d’interface en profondeur dans ces aquifères entre un compartiment contenant de l’oxygène et un compartiment anoxique riche en fer, mais aussi que ces zones d’interfaces peuvent avoir un rôle prépondérant dans le maintien des populations microbiennes en profondeur. L’objectif de cette thèse était ainsi d’explorer la diversité et l’écologie des Gallionellaceae au sein des milieux souterrains, afin de mieux comprendre le fonctionnement biogéochimique global de ces milieux. Une approche pluridisciplinaire, faisant intervenir des analyses métagénomiques et hydrogéochimiques, a été privilégiée pour répondre à cet objectif
Bacteria of the Gallionellaceae family (β-proteobacteria) oxidise dissolved iron at circumneutral pH to fuel their energy metabolism. These bacteria are endemic of microaerobic habitats, where they can outcompete the rapid abiotic oxidation of iron with oxygen. They are thus generally found in the interface areas between the atmosphere and an anoxic iron-rich compartment, such as a resurgence of groundwater. However, in the last five years, several studies have shown the presence of Gallionellaceae at depth in some subsurface environments, at depths where they are generally anoxic. In several of these environments, such as some aquifers in the Armorican basement (Brittany, France), Gallionellaceae even seem to dominate the microbial communities. This suggests (i) that there are deep interface zones in these aquifers between an oxygen-containing compartment and an anoxic iron-rich compartment, and (II) that these interface zones can have a major role in maintaining microbial populations at depth. The objective of this thesis was to explore the diversity and the ecology of Gallionellaceae bacteria in these subsurface environments, for uncover their overall biogeochemical functioning. A multidisciplinary approach, involving metagenomic and hydrogeochemical analyses, was used to achieve this objective

Nesta tese o autor estabelece um método sistemático de quantificação de risco em obras subterrâneas em maciço rochoso fraturado utilizando de maneira eficiente conceitos de confiabilidade estrutural. O método é aplicado a um caso de estudo real da caverna da Usina Hidrelétrica Paulo Afonso IV, UHE-PAIV. Adicionalmente, um estudo de otimização de projeto com base em risco quantitativo também é apresentado para mostrar as potencialidades do método. A estimativa do risco foi realizada de acordo com as recomendações da Organização de Auxílio contra Desastres das Nações Unidas, UNDRO, onde o risco pode ser estimado como a convolução entre as funções de perigo, vulnerabilidade e perdas. Para a quantificação da confiabilidade foram utilizados os métodos de aproximação FORM e SORM com uso de acoplamento direto e de superfícies de resposta polinomial quadráticas. A simulação de Monte Carlo também foi utilizada para a quantificação da confiabilidade no estudo de caso da UHE-PAIV devido à ocorrência de múltiplos modos de falha simultâneos. Foram avaliadas as ameaças de convergência excessiva das paredes, colapso da frente de escavação e a queda de blocos. As funções de perigo foram estimadas em relação à intensidade da ameaça como razão de deslocamento da parede ou volume do bloco. No caso da convergência excessiva, um túnel circular profundo foi estudado com o intuito de comparar a qualidade de aproximação da técnica numérica (FLAC3D com acoplamento direto) em relação à solução exata. Erros inferiores a 0,1% foram encontrados na estimativa do índice de confiabilidade ß. Para o caso da estabilidade de frente foram comparadas duas soluções da análise limite da plasticidade contra a solução obtida numericamente. Já no caso de queda de bloco, verificou-se que as recomendações de parcialização do sistema de classificação geomecânica Q incrementa consideravelmente a segurança da escavação conduzindo a padrões da prática mais avançada, por exemplo, de um ß de 2,04 para a escavação a seção plena até 4,43 para o vão recomendado. No estudo de caso, a segurança da caverna da UHE-PAIV foi estudada perante a queda de blocos utilizando o software Unwedge. A probabilidade de falha individual foi integrada no comprimento da caverna e o conceito de sistema foi utilizado para estimar a probabilidade de falha global. A caverna apresentou uma probabilidade de falha global de 3,11 a 3,22% e um risco de 7,22x10-3 x C e 7,29x10-3 x C, sendo C o custo de falha de um bloco de grandes dimensões. O bloco mais crítico apresentou um ß de 3,63. No estudo de otimização foram utilizadas duas variáveis de projeto, a espessura do concreto projetado e o número de tirantes por metro quadrado. A configuração ótima foi encontrada como o par [t, nb] que minimiza a função de custo total. Também, um estudo de sensibilidade foi realizado para avaliar as influências de alguns parâmetros no projeto ótimo da escavação. Finalmente, os resultados obtidos sugerem que as análises quantitativas de risco, como base para a avaliação e gestão de risco, podem e devem ser consideradas como diretriz da prática da engenharia geotécnica, uma vez que estas análises conciliam os conceitos básicos de projeto como eficiência mecânica, segurança e viabilidade financeira. Assim, a quantificação de risco é plenamente possível.
In this thesis the author establishes a systematic method for quantifying the risk in underground structures in fractured rock masses using structural reliability concepts in an efficient way. The method is applied to the case study of the underground cavern of Paulo Afonso IV Hydroelectrical Power Station UHE-PAIV. Additionally, an optimization study was conducted in order to show a potential application of the method. The estimation of the risk was done according to the recommendations of the United Nations Disaster Relief Organization UNDRO where risk can be estimated as the convolution between the hazard, vulnerability and losses functions. FORM and SORM were used as approximation methods for the reliability quantification by means of Direct Coupling and Quadratic Polynomial Response Surfaces. A Monte Carlo simulation was also used to quantify the reliability of the cavern UHE-PAIV because of the presence of multiple failure modes in the numerical model. In this study 3 types of threads were evaluated: excessive wall convergence, face stability and wedge block fall. Hazard functions were built relative to the thread intensities such as wall convergence ratio or block size. In the case of excessive wall convergence a deep circular tunnel was studied meaning to compare the quality of the approximation of the reliability technique (FLAC3D with direct coupling) to the exact solution. Errors below 0.1% were found in the reliability index ß estimation. The reliability of the face stability was evaluated using two limit analysis solutions against the numeric estimation. For the block stability it was verified that the sequential excavation recommended by the Q system increases considerably the reliability of the excavation leading safety to modern standard levels, e.g. from a ß equal to 2.04 for a full section excavation to 4.43 for a partial excavation. In the case study of the UHE-PAIV, the reliability of the underground cavern was estimated using the commercial software Unwedge. The probability of failure of individual blocks was integrated along the length of the cavern and the concept of structural system was used to estimate the global probability of failure. The cavern presented a probability of failure of 3.11% to 3.22% and a risk of 7.22x10-3 x C and 7.29x10-3 x C - where C is the cost of failure of a large block. The critical individual block showed a ß equal to 3.63. The optimization was performed considering two design variables − liner thickness and number of bolt per square meter. The optimal design was found as the pair, [t, nb] which minimizes the total cost function. Also, a sensibility analysis was conducted to understand the influence of some parameters in the location of the optimal excavation design. Concluding, the results obtained here suggest that the quantitative risk analyses, as a base for the risk assessment and management, can and must be considered as a north for the practice of geotechnical engineering owing that these analyses reconcile the basic concepts of mechanical efficiency, safety and financial feasibility. Thus, risk quantification is fully affordable.

O presente trabalho foi realizado para estudar o efeito sobre a propagação de fraturas em juntas não-persistentes quando existe uma variação da rugosidade nas juntas. Para esta abordagem, foram analisados os modos de coalescência, o ângulo de início das fraturas, a resistência à compressão e deformação de modelos de argamassa contendo juntas não-persistentes e submetidos a estados biaxiais de tensão. Na literatura especializada encontram-se vários trabalhos que estudam o comportamento de juntas lisas não-persistentes. Infelizmente, este tipo de juntas não leva em conta os efeitos da dilatância e do aumento do atrito. Neste estudo, desenvolveu-se um método para produzir juntas rugosas não-persistentes dentro dos moldes de argamassa. Desta forma, conseguiu-se comparar os diferentes modos de ruptura, tanto para as juntas lisas como as rugosas. A configuração geométrica usada foi de 15 juntas com 'alfa' = 54 graus; 'beta' = 60 graus; Lj = Lb = 50mm e d = 25mm. Onde 'alfa' é o ângulo gerado entre o plano de uma junta e o plano formado entre as pontas de juntas não-coplanares, 'beta' é a inclinação da junta com respeito ao plano de tensão maior, Lb denota à distância entre juntas paralelas coplanares, Lj é o comprimento da junta e d é a distância entre juntas paralelas não coplanares. Estes parâmetros mantiveram-se constantes em todos os ensaios, tanto para as juntas lisas (JRC = 0) como as rugosas (JRC = 6,96 e JRC = 12,25). Usando os parâmetros acima mencionados, observou-se que o tipo de ruptura sempre aconteceu por escalonamento. Para as amostras contendo as juntas lisas, JRC = 0, o mecanismo principal de coalescência entre as juntas é a tração. Para estas juntas, os ângulos de início das fraturas, em média, resultaram de 64º e 65º para esquerda e direita, respectivamente. Em média, a resistência a compressão normalizada ('sigma'nor = 'sigma'1 - 'sigma'2 / 'sigma'cs; onde 'sigma'1 e 'sigma'2 são as tensões principais e 'sigma'cs é a resistência média à compressão simples) destes corpos de prova resultou ter o valor mais baixo, 'sigma'nor = 0,52, e a maior deformação, 'épsilon' = 0,0057. No caso das juntas com JRC = 6,7, a coalescência ocorreu tanto por tração como por cisalhamento, descrevendo um caminho ondulante entre as pontas das juntas. O ângulo médio de início das fraturas foi de 40º para o lado esquerdo e 48º para o lado direito. A resistência média normalizada destes corpos a compressão foi de 'sigma'nor = 0,54 e uma deformação de 'épsilon' = 0,0053. Com as juntas com JRC = 12,3, a coalescência também apresentou ambos os mecanismos, tração e cisalhamento, seguindo uma direção inclinada no início e trajetória reta no meio. Os ângulos de início obtidos foram 5º no lado esquerdo e 20º do lado direito. Os valores maiores de resistência média normalizada e o valor médio menor de deformação foram obtidos nestes tipo de juntas, sendo estes de 'sigma'nor = 0,59 e 'épsilon' = 0,0045. Verificou-se então que a rugosidade tem uma grande influência sobre a propagação da fratura, afetando grandemente o modo de coalescência, o ângulo de início de propagação das fraturas e a resistência e deformação total dos corpos de prova
The present experimental study was conducted to investigate the effect of joint roughness on the fracture propagation of models with non persistent joints. For this approach the parameters investigated are : coalescence, the crack initiation angle, the compressive strength and deformation of the mortar samples containing non-persistent rough joints under biaxial loading. There are many works in specialized literature that study the behavior of non-persistent smooth joints, unfortunately, this kind of approach does not take into account the effect of the dilation and the increase of friction due to the joint roughness. In this study, a new method was developed to produce non-persistent rough joints inside the mortar models. With this method it was possible to compare the different paths of rupture generated for the smooth and for the rough joints. Each sample had 15 joints with 'alfa' = 54º; 'beta' = 60º; Lj = Lb = 50mm and d = 25mm. Where 'alfa' is the formed angle between the joint plane and the plane generated by two non coplanar joint tips, 'beta' is the joint inclination angle with the principal plane stress, Lb is the distance between coplanar joints, Lj is the length of the joint, d is the distance between two non-coplanar joints. These parameters remained constant in all the tests; the only variation permitted was in the joint roughness : from smooth joints (JRC = 0) to rough joints (JRC = 6,96 and JRC = 12,25). Using the mentioned parameters before it was always obtained the stepping failure. For the samples containing smooth joints, JRC = 0, the main mechanism of coalescence is tension. For these joints the average crack initiation angles, had resulted of 64º and 65º for left and right side, respectively. The average normalized compression strength ('sigma'nor = 'sigma'1 - 'sigma'2 / 'sigma'cs; where 'sigma'1 and 'sigma'2 are the principal stresses and 'sigma'cs is the average compression strength) of these tests resulted to have the lowest value, 'sigma'nor = 0,52, and the highest deformation, 'épsilon' = 0,0057. In the case of joints with JRC = 6,7; the mechanisms of coalescence are tension and shear, growing in a waving path between the joint tips. The average crack initiation angle was of 40º for the left side and 48º for the right side of the joint. The average normalized compression strength of these tests was of 'sigma'nor = 0,54 and deformation 'épsilon' = 0,0053. With joints having JRC = 12,3; the coalescence also presents both mechanisms, tension and shear, following a direction inclined in the beginning and a straight line in the middle of the way. The crack initiation angles had been : 5º in the left side and 20º of the right side. The highest values of average normalized strength resistant and the lowest average value of deformation were found in this type of joint, being of 'sigma'nor = 0,59 e 'épsilon' = 0,0045 respectively. With this approach, it was verified that the joint roughness influence the fracture propagation, affecting the coalescence, the crack initiation angle, the resistance and total deformation of the tested specimens

Les aquifères fracturés sont un enjeu majeur de l'hydrogéologie actuelle. Ils constituent une ressource essentielle pour de nombreuses populations. Le massif de l'Ursuya (France, 64), en est une illustration. Constitué de formations métamorphiques fracturées, il est intensément exploité pour l'alimentation en eau potable. Une approche multidisciplinaire a permis la compréhension du fonctionnement de ce système. Les résultats obtenus constituent une avancée dans la connaissance des aquifères discontinus et offrent des pistes pour une gestion raisonnée de cette ressource.Le signal d'entrée est caractérisé dans sa composante quantitative et qualitative. Le suivi des paramètres climatiques permet d'estimer la lame d'eau participant à la recharge de l'aquifère. La caractérisation isotopique de l'eau précipitée met ensuite en évidence une origine majoritairement atlantique des masses d'air, responsables des précipitations sur le nord-ouest du Pays Basque. Des circulations atmosphériques sur la péninsule Ibérique, l'Europe du Nord et la région méditerranéenne sont cependant responsables de certains événements pluvieux. La composition chimique de l'eau de pluie, résultant de ces origines, est caractérisée par une faible acidité et par des concentrations en éléments anthropiques parfois élevées.L'hydrochimie des eaux souterraines est étudiée conjointement avec des données de temps de séjour acquises par l'interprétation des concentrations en 3H, CFC et SF6. Les caractéristiques physico-chimiques, les temps de séjours mesurés (moins de 10 ans à plus de 50 ans) et les phénomènes de mélanges associés permettent de proposer un modèle conceptuel des écoulements souterrains. Celui-ci met en exergue le rôle prépondérant du profil d'altération développé dans les milieux cristallins (de la surface vers la profondeur : altérites, roche fissurée et roche saine), du point de vue de la minéralisation de l'eau comme de celui des modalités d'écoulement.Une approche quantitative est finalement proposée. Du point de vue hydrodynamique, l'hétérogénéité spatiale est importante (10-4 m s-1 < K < 10-8 m s-1). Les altérites offrent une capacité de stockage et de régulation de la recharge. Un modèle numérique synthétise et valide ces résultats. Les simulations montrent de fortes interactions entre les réseaux d'écoulements superficiel et souterrain et de faibles impacts de l'exploitation actuelle sur les flux d'eau souterraine. Les évolutions climatiques ne modifieront pas significativement les écoulements durant les prochaines décennies. Une diminution des débits des sources et des cours d'eau est toutefois probable. Ce modèle numérique et l'ensemble des résultats obtenus serviront de base pour une gestion raisonnée de la ressource en eau de l'aquifère de l'Ursuya.

碩士
國立臺北科技大學
資源工程研究所
100
Hydraulic models play the key roles for description of underground water flow and solute transport, and are also crucial for the development and application of water resources and underground. The natural rock include many discontinuities like crevasses, beddings, joints and schistosities, which cause the difficulty in simulation and analysis and even further difficulties of engineering design and construction resulting in its mechanical and hydraulic behaviors present heterogeneity and anisotropy. Therefore, how to get the hydrogeological characteristics of the site and select the appropriate hydraulic model to perform prediction analysis through the modest description of scale is the key point for hydrogeological study from conceptual model, description model towards hydraulics model and numerical model. This study designs a hydrogeological testing well site and a series of fracture parameters investigation and hydraulic parameters tests are performed, so as to get the equivalent hydraulic conductivity of fractured rock mass based on the site hydrogeological characteristics described by the discrete fracture network model (DFN) .To thoroughly obtain the parameters required by the DFN mode, laboratory experiments are conducted to obtain the characteristics of mechanical and geometric parameters. Based on the discrete fracture parameters from outcrop investigation, in-situ hydraulic test and lab test, this study established the fracture network by two-dimensional fracture network model to evaluate the site hydraulic conductivity. This research shows the site equivalent hydraulic conductivity obtained by different hydraulic test methods applied in siltstones with the difference exceeding two orders of magnitude and the dimensions range is from 10-5 to 10-7m/s .From single well hydraulic test results shows the maximum difference of hydraulic conductivity resolved by different fracture combinations drops from 10-5 to 10-9 m/s, exceeding four orders of magnitude, indicating that the fracture distribution significantly affects the site hydrogeological characteristics. This study utilize the discrete fracture network model to build the well sites after investigating the fracture surface parameters and further obtains the site hydraulic conductivity based on site hydrological tests, which is a feasible technique for the investigation of the hydrogeological characteristics of fracture rock mass. The simulation results show that, based on the fracture parameters measured nearby the well site, the numbers of fractures taken from the simulated discrete fracture network are similar to field measured data in wells. The calculated hydraulic conductivity dimension is from 10-5 to 10-7 m/s, which is very close to the average dimension of site hydraulic test results. This study demonstrates that using the discrete fracture network model to think about hydrogeological model can provide the references and applications for similar cases of investigation and analysis on hydrogeological properties by investigating procedure of fracture rock parameters and permeation parameters and statistical analysis. The procedure includes the wells site building, in-situ test, laboratory experiments and related simulation analysis technologies.

Fracture and fracture network modelling is a multi-disciplinary research area. Although the literature in general is significant, many research challenges remain. The complex geometry and topology of realistic fracture networks largely determine the static and dynamic mechanical properties of rock. In applications to hot dry rock geothermal reservoirs it is not possible to observe or measure fractures directly on any scale and the only data available are indirect measurements, such as seismic activity generated by hydraulic fracture stimulation. The lack of direct data and the complexities of the fracture characteristics make fracture network prediction and modelling in these applications very difficult. The ultimate purpose of the fracture and fracture network models is to evaluate the response of the fracture system to stress regimes and fluid flow. As understanding of the effective factors in the geometrical modelling of fractures and consequently topological properties of fracture networks increases, more accurate and hence more reliable results can be achieved from associated analyses. For flow modelling in geothermal reservoirs, the critical component of a fracture model is the connectivity of the fractures as this determines the technical feasibility of heat production and is the single most significant factor in converting a heat resource to a reserve. The ability to model this component effectively and to understand the associated system is severely constrained by the lack of direct data. In simulations, the connectivity of a fracture network can be controlled to a limited extent by adjusting the fracture and fracture network parameters (e.g., locations, orientations) of the defining distribution functions. In practical applications connectivity is a response of the system not a variable. It is essential to pursue modelling methods that maximise the extraction of information from the available data so as to achieve the highest possible accuracy in the modelling. Although the evaluation of fracture connectivity is an active research area, widely reported in the literature, almost all connectivity measures are based on degraded representations of the fracture network i.e., lattice-based. The loss of fracture connectivity information caused by using discrete representations is significant even when very high resolutions (assuming they are feasible) are used. This is basically due to the fact that the aperture dimensions of fractures are several magnitudes smaller than their lengths. If discretisation is necessary, then a better approach would be to retain all connectivity information between fractures, i.e. for connectivity information to remain invariant to the resolution of the discretisation. Such a method would provide more reliable evaluation of connectivity. This thesis covers the modelling of fracture networks, the characterisation (particularly connectivity) of fracture networks and applications.
Thesis (Ph.D.) -- University of Adelaide, School of Civil, Environmental and Mining Engineering, 2014

碩士
國立中央大學
土木工程學系
107
This paper presents the mechanical behaviors of fractured rock masses for various geometrical conditions by using the Particle Flow Code (PFC3D). A specified rock mass size is assigned by software FracMan to generate discrete fracture network (DFN) then the fracture data were input into smooth joint model (SJM), combing with bonded particle model (BPM) by PFC3D to produce synthetic rock mass (SRM). SRM was used to simulate the mechanical behaviors based on macroscopically isotropic/anisotropic rock under triaxial test, calculating major principal stress, young's modulus, crack numbers, stress-axial strain relationship and volumetric strain-axial strain relationship. The research projects are including: (1) Set a series of parameters to study the effect of the fracture intensity and the fracture size on the mechanical behaviors of the fractured rock mass. (2) Select one set of in-situ fracture data which was uniformly random distribution (κ = 0) to generate isotropic rock for triaxial test then observe the failure process and the failure mode. Compare our result with the uniaxial test observations of Basu et al. (2013), and the triaxial test result of Bieniawski (1967), Wawersik and Fairhust (1970) and Elliott (1982). (3) Set up single fracture set of seven angles to generate anisotropic rock for triaxial test then observe the failure process and the failure mode. The experimental results of Tien et al. (2006) and Khanlari et al. (2014) were compared with the failure mode of the test, and the maximum principal stress of the test results was compared with the failure criteria proposed by Tien and Kuo (2006). (4) To verify the conceptual model proposed by Hoek and Brown (1980, 1988), generating SRM with one to four sets of fracture then act the uniaxial test. Furthermore, to verify the accuracy of the Young’s modulus of the transversely isotropic rock mass of one set of fracture, using the method proposed by Amadei (1983) to determine elastic constants of the transversely isotropic rock mass.

碩士
國立臺灣大學
土木工程學研究所
96
It is crucial to well know on the behaviors of rock masses for underground utilization, such as the tunnel, radioactive waste material store and the liquefied natural gas stores etc., all need to build the appropriate model for the description of behaviors of rock masses, so as to estimate, analyze, predict or control all sorts of project behaviors. Traditionally, the behavior of rock masses can be described specifically in accordance with the characteristic of handling problem such as thermal field, flow field, mechanical field or chemical field. However, the problems of flow field and mechanical field always lead the security of fractured rock engineering. Therefore, the appropriate prediction on the flow rate, stress and deformation of fractured rock masses, i.e., the hydro-mechanical coupled behavior, is not only the base for engineering design, but also the key point for its performance assessment. In this study, the 2-D discrete fractured networks (DFN) model was performed through MATLAB programming language. The discrete fractured networks model was generated according to geometric parameters of fractures, such as the locations of centers of fractures, trace lengths, orientations and apertures, and they also follow their own distribution type. Furthermore, the flow field in the rock was solved using Darcy’s Law and mass-balance equation with specified boundary conditions. Then, it based on the concept of equivalent continuum to obtain the hydraulic conductivity of a zone which was selected by users. On the basis of this model, this research considers the permeability of rock mass and to probe into their influences on the mechanical and hydraulic behaviors. Users can select the theories of hydraulic behavior or hydro-mechanical coupled behavior free in this 2-D discrete fractured networks model. Using the theory of hydraulic behavior, it will calculate with hydraulic apertures instead of mechanical apertures. Using the theory of hydro-mechanical coupled behavior, it not only employs mechanical apertures to advance the accuracy compared with using the theory of hydraulic behavior, but also probe into the variations of permeability of rock mass caused by stresses changing. Under analytic process, users also can freely choose the zone and size which they want to observe and obtain the hydraulic conductivity of rock mass in the zone. Utilizing this way which freely choose the zone and size, we can obtain the size of representative volume element (RVE) exactly. Additionally, the permeability of fractured rock mass would cause the permeability anisotropy with the change of stresses. Thus this research also probe into the change of permeability anisotropy caused by overburdenend and caused by parameters. The results of study show that when the compressed normal to the joint, JRC and JCS would affect the hydraulic conductivity. And the accuracy of JRC will be a key factor. Under shear loading, the residual friction angle affects the hydraulic behavior of VII joints hardly. The hydraulic conductivity tends toward stability when the overburden is deep to certain depth. Utilizing the way which the observed zone’s size and position cooperate each other, the size of representative volume element (RVE) would be obtained exactly. The observed zone’s size chooses smaller, the more variable hydraulic conductivity is. The observed zone’s size chooses larger, the more steady hydraulic conductivity tends toward. The density of spacing is lower, the larger range of steady size is. The density of spacing is higher, the higher k value is. The trace length is longer, the smaller range of steady size is. The trace length is shorter, the larger range of steady size is. The coefficient of lateral earth pressue and JRC could cause the permeability anisotropy with the change of overburdened, but the orientation of fractured rock mass influence the permeability anisotropy smaller.

碩士
國立中央大學
土木工程學系
105
This study presents the representative elementary volume (REV) of P32 (fracture intensity) and hydraulic conductivity of fractured rock mass. Discrete fracture network (DFN) generated by FracMan is adopted to create rock mass models. A series of parametric studies including dip angle, dip direction, Fisher constant κ, size of rock mass model, shape of rock mass model, specimen volume, fracture diameter, and P32 were investigated to study the REV of P32. Based on the results of the parametric studies, a novel equation to quantify the COV (Coefficient of variance) of P32 in terms of specimen volume, fracture diameter and P32 was established. A precise REV size can be obtained easily by assigning the acceptable COV. Thereafter, some case studies were used to verify the proposed novel equation. Conventional Oda and Oda gold were adopted to estimate the hydraulic conductivity of the fractured rock mass. By using Oda conventional, a series of parametric studies including specimen volume, fracture diameter, P32, transmissivity, and aperture were investigated to study the REV of hydraulic conductivity. Subsequently, that REV of hydraulic conductivity was compared with the REV of P32. In the other hand, by using Oda gold, only P32 was chosen as parametric study. Eventually, a proposed new method was conducted by examining the Monte Carlo simulation for REV of hydraulic conductivity determination.

碩士
國立中央大學
土木工程學系
105
This paper presents the uncertainties of geometrical and mechanical properties based on macroscopically isotropic synthetic rock mass. In the geometrical section, the analytical approach used the probability of whether each fracture center point would be sampled or not. The coefficient of variance of P30 could then be calculated by binomial theorem. According to the relation between P30 and P32, the coefficient of variance of P32 could also be yielded. To verify the analytical solution, FracMan was used to generate the rock mass model and discrete fracture network (DFN) to simulate the measurements and access the coefficient of variance of P32. The analytical solution and numerical solution were very similar when the ratio of the fracture diameter and the length of the sample volume was smaller than 0.5. In the mechanical section, this paper adopted the concept of synthetic rock mass (SRM). FracMan was used to generate DFN in rock mass models and to execute the sampling. The SRM was generated by combining the fracture data from FracMan and the bonded particle model in PFC3D. The uniaxial compression test, which uses strain control, was conducted to investigate the mechanical behavior of SRM. The uncertainty in the mechanical behavior of SRM is derived from fracture permutation and sampled fracture intensity. In past studies, the effects of these two factors were studied at the same time, but the precise effect of each factor could not be obtained due to the methodology used in these studies. To quantify the effect of fracture permutation, the P32 of each sample must be the same. The direct-generate method and sample-modify method were therefore adopted to ensure that each sample’s P32 were the same. By using the analytical solution of P32 and the relation between P32 and the mechanical property, the effect of the sampled fracture intensity could be calculated. The results showed that the effect of fracture permutation and fracture intensity were almost the same for uniaxial compression strength, and that the effect of fracture intensity was larger than fracture permutation on Young’s modulus. The variance of the mechanical behavior of SRM was also equal to the combination of the variance affected by fracture permutation and sampled fracture intensity. This relationship could also be proven by the theory of analysis of variance. According to this paper, as P32 increases, the coefficient of variance of fracture intensity will decrease and the coefficient of variance of both uniaxial compression strength and Young’s modulus will increase. In the range of parameters adopted in this paper, when P32 was smaller than 1.8 m-1, the coefficient of variance of fracture intensity was larger than coefficient of variance of uniaxial compression strength, and Young’s modulus was the smallest among them. When P32 was greater than 1.8 m-1, the coefficient of variance of uniaxial compression strength was larger than the coefficient of variance of fracture intensity, and Young’s modulus was the smallest among them.

博士
國立成功大學
資源工程學系
85
ABSTRACT Fractures play an important role both in the engineering behaviors and groundwater movement of rock masses. A description of the fracture geometry pattern is a primary requirement to assess the hydraulic and mechanical behaviors of jointed rock masses. To enhance the reliability of fracture data, this paper firstly proposes some analytical techniques based on statistical approaches to characterize and analyze the variability of fracture pattern. In order to estimate the hydraulic conductivity, a fractured rock mass which contains a lot of fractures, is assumed to be a homogenous and anisotropic porous medium. On the basis of theoretical derivation, laboratory and field data obtained from outcrops, model of estimating the hydraulic conductivity of fractur rocks is presented. In this study an attempt is made to estimate the relationship between the hydraulic conductivity and fracture pattern. The new model includes effects of hydromechanical coupling, normal closure and fracture geometry. Finally, an actual rock mass of jointed andesite rock on the Lan-Yu site, Taiwan, was studied to predict the hydraulic conductivity with depth.