[pt] 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. / [en] 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. / [es] 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.

Recent models of groundwater flow in the Blue Ridge Province suggest multiple aquifers and flow paths may be responsible for springs and seeps appearing throughout the region. Deep confined aquifers and shallow variably confined aquifers may contribute water to spring outlets, resulting in vastly different water quality and suitability for potable water supplies and stock watering. A new Low Flow Recording System (LoFRS) was developed to measure the discharge of these springs that are so ubiquitous throughout the Blue Ridge Province. Analysis of spring discharge, combined with electrical resistivity surveying, aquifer tests, and water chemistry data reveal mixed shallow and deep aquifer sources for some springs, while other springs and artesian wells are sourced only in the deep aquifer. The technique is suitable for rapid characterization of flow paths leading to spring outlets. Rapid characterization is important for evaluation of potential water quality problems arising from contamination of shallow and deep aquifers, and for evaluation of water resource susceptibility to drought. The spring discharge technique is also suitable for use in other locations where fractured rock and crystalline rock aquifers are common. / Master of Science

An analytical model is presented for the analysis of pulse interference tests conducted in a fractured porous medium with connection to a free surface boundary at the water table. The solution is applicable to open borehole pulse interference tests due to the accommodation of multiple horizontal fractures intersecting each wellbore and a connection from the uppermost horizontal fracture to a free surface boundary. The solution is derived using the Laplace transform method and evaluation of the solution is performed by numerical inversion using the Talbot algorithm. Based on an informal sensitivity analysis, unique values for transmissivity, storativity, specific storage, vertical hydraulic conductivity and specific yield are predicted over a range of realistic values for these parameters. The analytical model is used to analyze slug tests and pulse interference tests conducted in a fractured gneiss formation. The results of these tests are compared to long-term pumping tests to identify the effect of measurement scale on transmissivity, storativity, vertical hydraulic conductivity and specific yield obtained in a fractured rock setting. Scale artefacts relating to measurement or analysis methods are minimized through the use of consistent well configurations in each of the applied hydraulic testing methods. The geometric mean estimates of transmissivity and storativity are shown to vary by less than an order of magnitude from local-scale tests to long-term pumping tests. The geometric mean specific yield result from a series of pulse interference tests that samples both highly fractured and poorly fractured portions of the rock formation approximates the long-term pumping test estimate of specific yield. The geometric mean result for vertical hydraulic conductivity decreases by approximately 1.5 orders of magnitude from the slug test to pumping test scale; however, pulse interference tests conducted on highly fractured portions of the formation produce vertical hydraulic conductivity estimates that are within a half order of magnitude of the long-term pumping test results. This suggests that the performance of pulse interference tests on a highly fractured portion of a rock formation may be a less time-intensive alternative to large-scale pumping tests in the determination of vertical hydraulic conductivity. / Thesis (Master, Civil Engineering) -- Queen's University, 2011-06-24 19:29:52.743

<p><font face="TimesNewRoman"> <p align="left">Research findings in current study provide a new insight into the fractured rock aquifers in the TMG area. Some of the results will have wide implications on the groundwater management and forms a solid basis the further study of the TMG aquifers.</p> </font></p>

<p><font face="TimesNewRoman"> <p align="left">Research findings in current study provide a new insight into the fractured rock aquifers in the TMG area. Some of the results will have wide implications on the groundwater management and forms a solid basis the further study of the TMG aquifers.</p> </font></p>

Numerical analysis of multi-field problems in porous and fractured media is an important subject for various geotechnical engineering tasks such as the management of geo-resources (e.g. engineering of geothermal, oil and gas reservoirs) as well as waste management. For practical usage, e.g. for geothermal, simulation tools are required which take into account both coupled thermo-hydro-mechanical (THM) processes and the uncertainty of geological data, i.e. the model parametrization. For modeling fractured rocks, equivalent porous medium or multiple continuum model approaches are often only the way currently due to difficulty to handle geomechanical discontinuities. However, they are not applicable for prediction of flow and transport in subsurface systems where a few fractures dominates the system behavior. Thus modeling coupled problems in discretely fractured porous media is desirable for more precise analysis. The subject of this work is developing a framework of the finite element method (FEM) for modeling coupled THM problems in discretely fractured and non-fractured porous media including thermal water flow, advective-diffusive heat transport, and thermoporoelasticity. Pre-existing fractures are considered. Systems of discretely fractured porous media can be considered as a problem of interacted multiple domains, i.e. porous medium domain and discrete fracture domain, for hydraulic and transport processes, and a discontinuous problem for mechanical processes. The FEM is required to take into account both kinds of the problems. In addition, this work includes developing a methodology for the data uncertainty using the FEM model and investigating the uncertainty impacts on evaluating coupled THM processes. All the necessary code developments in this work has been carried out with a scientific open source project OpenGeoSys (OGS). In this work, fluid flow and heat transport problems in interactive multiple domains are solved assuming continuity of filed variables (pressure and temperature) over the two domains. The assumption is reasonable if there are no infill materials in fractures. The method has been successfully applied for several numerical examples, e.g. modeling three-dimensional coupled flow and heat transport processes in discretely fractured porous media at the Gross Schoenebck geothermal site (Germany), and three-dimensional coupled THM processes in porous media at the Urach Spa geothermal site (Germany). To solve the mechanically discontinuous problems, lower-dimensional interface elements (LIEs) with local enrichments have been developed for coupled problems in a domain including pre-existing fractures. The method permits the possibility of using existing flow simulators and having an identical mesh for both processes. It enables us to formulate the coupled problems in monolithic scheme for robust computation. Moreover, it gives an advantage in practice that one can use existing standard FEM codes for groundwater flow and easily make a coupling computation between mechanical and hydraulic processes. Example of a 2D fluid injection problem into a single fracture demonstrated that the proposed method can produce results in strong agreement with semi-analytical solutions. An uncertainty analysis of THM coupled processes has been studied for a typical geothermal reservoir in crystalline rock based on the Monte-Carlo method. Fracture and matrix are treated conceptually as an equivalent porous medium, and the model is applied to available data from the Urach Spa and Falkenberg sites (Germany). Reservoir parameters are considered as spatially random variables and their realizations are generated using conditional Gaussian simulation. Two reservoir modes (undisturbed and stimulated) are considered to construct a stochastic model for permeability distribution. We found that the most significant factors in the analysis are permeability and heat capacity. The study demonstrates the importance of taking parameter uncertainties into account for geothermal reservoir evaluation in order to assess the viability of numerical modeling.

Philosophiae Doctor - PhD / Research findings in current study provide a new insight into the fractured rock aquifers in the TMG area. Some of the results will have wide implications on the groundwater management and forms a solid basis the further study of the TMG aquifers.

Philosophiae Doctor - PhD / Research findings in current study provide a new insight into the fractured rock aquifers in the TMG area. Some of the results will have wide implications on the groundwater management and forms a solid basis the further study of the TMG aquifers.

Numerical analysis of multi-field problems in porous and fractured media is an important subject for various geotechnical engineering tasks such as the management of geo-resources (e.g. engineering of geothermal, oil and gas reservoirs) as well as waste management. For practical usage, e.g. for geothermal, simulation tools are required which take into account both coupled thermo-hydro-mechanical (THM) processes and the uncertainty of geological data, i.e. the model parametrization. For modeling fractured rocks, equivalent porous medium or multiple continuum model approaches are often only the way currently due to difficulty to handle geomechanical discontinuities. However, they are not applicable for prediction of flow and transport in subsurface systems where a few fractures dominates the system behavior. Thus modeling coupled problems in discretely fractured porous media is desirable for more precise analysis. The subject of this work is developing a framework of the finite element method (FEM) for modeling coupled THM problems in discretely fractured and non-fractured porous media including thermal water flow, advective-diffusive heat transport, and thermoporoelasticity. Pre-existing fractures are considered. Systems of discretely fractured porous media can be considered as a problem of interacted multiple domains, i.e. porous medium domain and discrete fracture domain, for hydraulic and transport processes, and a discontinuous problem for mechanical processes. The FEM is required to take into account both kinds of the problems. In addition, this work includes developing a methodology for the data uncertainty using the FEM model and investigating the uncertainty impacts on evaluating coupled THM processes. All the necessary code developments in this work has been carried out with a scientific open source project OpenGeoSys (OGS). In this work, fluid flow and heat transport problems in interactive multiple domains are solved assuming continuity of filed variables (pressure and temperature) over the two domains. The assumption is reasonable if there are no infill materials in fractures. The method has been successfully applied for several numerical examples, e.g. modeling three-dimensional coupled flow and heat transport processes in discretely fractured porous media at the Gross Schoenebck geothermal site (Germany), and three-dimensional coupled THM processes in porous media at the Urach Spa geothermal site (Germany). To solve the mechanically discontinuous problems, lower-dimensional interface elements (LIEs) with local enrichments have been developed for coupled problems in a domain including pre-existing fractures. The method permits the possibility of using existing flow simulators and having an identical mesh for both processes. It enables us to formulate the coupled problems in monolithic scheme for robust computation. Moreover, it gives an advantage in practice that one can use existing standard FEM codes for groundwater flow and easily make a coupling computation between mechanical and hydraulic processes. Example of a 2D fluid injection problem into a single fracture demonstrated that the proposed method can produce results in strong agreement with semi-analytical solutions. An uncertainty analysis of THM coupled processes has been studied for a typical geothermal reservoir in crystalline rock based on the Monte-Carlo method. Fracture and matrix are treated conceptually as an equivalent porous medium, and the model is applied to available data from the Urach Spa and Falkenberg sites (Germany). Reservoir parameters are considered as spatially random variables and their realizations are generated using conditional Gaussian simulation. Two reservoir modes (undisturbed and stimulated) are considered to construct a stochastic model for permeability distribution. We found that the most significant factors in the analysis are permeability and heat capacity. The study demonstrates the importance of taking parameter uncertainties into account for geothermal reservoir evaluation in order to assess the viability of numerical modeling.

The effect of in-situ or redistributed stress on solute transport in fractured rocks is one of the major concerns for many subsurface engineering problems. However, it remains poorly understood due to the difficulties in experiments and numerical modeling. The main aim of this thesis is to systematically investigate the influences of stress on solute transport in fractured rocks, at scales of single fractures and fracture networks, respectively. For a single fracture embedded in a porous rock matrix, a closed-form solution was derived for modeling the coupled stress-flow-transport processes without considering damage on the fracture surfaces. Afterwards, a retardation coefficient model was developed to consider the influences of damage of the fracture surfaces during shear processes on the solute sorption. Integrated with particle mechanics models, a numerical procedure was proposed to investigate the effects of gouge generation and microcrack development in the damaged zones of fracture on the solute retardation in single fractures. The results show that fracture aperture changes have a significant influence on the solute concentration distribution and residence time. Under compression, the decreasing matrix porosity can slightly increase the solute concentration. The shear process can increase the solute retardation coefficient by offering more sorption surfaces in the fracture due to gouge generation, microcracking and gouge crushing. To study the stress effects on solute transport in fracture systems, a hybrid approach combing the discrete element method for stress-flow simulations and a particle tracking algorithm for solute transport was developed for two-dimensional irregular discrete fracture network models. Advection, hydrodynamic dispersion and matrix diffusion in single fractures were considered. The particle migration paths were tracked first by following the flowing fluid (advection), and then the hydrodynamic dispersion and matrix diffusion were considered using statistic methods. The numerical results show an important impact of stress on the solute transport, by changing the solute residence time, distribution and travel paths. The equivalent dispersion coefficient is scale dependent in an asymptotic or exponential form without stress applied or under isotropic compression conditions. Matrix diffusion plays a dominant role in solute transport when the hydraulic gradient is small. Outstanding issues and main scientific achievements are also discussed. / QC 20111011