Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / O efeito deletÃrio da Ãgua à um dos principais fatores responsÃveis pelo desgaste de revestimentos asfÃlticos. No interior desta estrutura, a Ãgua pode interferir na adesÃo do filme de ligante com os agregados e na coesÃo do prÃprio filme de ligante, agravando mecanismos de dano, tais como deformaÃÃo permanente e trincamento por fadiga. Dessa forma, estudar o comportamento do revestimento asfÃltico na presenÃa da Ãgua à de fundamental importÃncia para a durabilidade da estrutura. Para que a Ãgua seja transportada no interior do material à necessÃrio que os vazios se comuniquem. Entretanto, a distribuiÃÃo dos vazios com a profundidade da camada de revestimento nÃo à homogÃnea, bem como a condiÃÃo anisotrÃpica de misturas asfÃlticas faz com que essa distribuiÃÃo dos vazios seja tambÃm diferente nas direÃÃes horizontal e vertical. O coeficiente de permeabilidade (k) tem sido um parÃmetro comumente utilizado para caracterizar a capacidade drenante de misturas asfÃlticas. Entretanto, o k sà à constante para um material no estado saturado. No estado nÃo saturado, o k à funÃÃo da quantidade de Ãgua presente nos vazios. Como na maioria das estruturas de engenharia, incluindo os pavimentos asfÃlticos, predomina o estado nÃo saturado, o presente trabalho tem como objetivo principal avaliar, atravÃs de simulaÃÃo numÃrica, o fluxo dâÃgua em uma seÃÃo hipotÃtica de pavimento asfÃltico com revestimento composto por diferentes misturas asfÃlticas com diferentes permeabilidades. No total, foram analisadas seis misturas asfÃlticas do tipo Concreto AsfÃltico (CA) com Volumes de vazios (Vv) diferentes (4% e 7% de Vv), e a partir de amostras com trÃs alturas (6,5cm, 12cm e 15cm para cada Vv). As amostras com 15cm e 12cm de altura foram cortadas em trÃs partes (topo, meio e base) com o objetivo de verificar o comportamento da permeabilidade com a altura da amostra. Os resultados indicam que a distribuiÃÃo dos vazios com a altura da amostra se altera, consequentemente, tambÃm altera os valores do k com a profundidade. Resultados obtidos a partir de amostras com 12cm de altura indicam que a permeabilidade diminui com a profundidade se comparada aos resultados obtidos para amostras com 15cm de altura. AlÃm disso, verificou-se que a distribuiÃÃo do nÃvel de saturaÃÃo na camada de revestimento diminui à medida que a camada de revestimento se aproxima da borda da estrutura. Por fim, amostras com 7% de Vv apresentam maior capacidade drenante, e consequentemente, sÃo mais susceptÃveis ao dano provocado pela umidade quando comparada com amostras com 4% de Vv. / The deleterious effect of water is a major factor responsible for the distresses in flexible pavements. Inside the structure, the water can interfere in the binder/aggregate adhesion and in the cohesion of the binder itself, accelerating damage mechanisms such as fatigue damage and permanent deformation. Thus, studying the behavior of the pavement in the presence of water is crucial to predict the behavior of this structure. For the water transport inside the material it is necessary an interconnection of voids. However, the distribution of voids with the depth of the surface layer is non homogeneous, as well as the anisotropic condition of asphalt mixtures results in different voids distribution in horizontal and vertical directions. The coefficient of permeability (k) has been a parameter commonly used for characterizing the drainage capacity of asphalt mixtures. However, the k is constant only for a saturated state, while for the unsaturated state, k is function of the amount of water present in the voids. For most engineering structures, including asphalt pavements, the unsaturated state is predominant. In this context, this study aims to evaluate, through numerical simulation, the flow of water in a hypothetical section of asphalt pavement with different asphalt mixtures with different permeabilities. In total, they were evaluated six Asphalt Concrete (AC) mixtures with different Air Voids (AV - 4% and 7%), and three different heights (6.5 cm, 12cm and 15cm for each AV). Samples with 15cm and 12cm height were cuted in three parts (top, middle and base) in order to verify the permeability behavior with the depth of the sample. The results indicate that the distribution of voids changes with the height of the sample and consequently also changes the k value with the depth. Results obtained from 12cm height samples indicate that the permeability decreases with depth when compared to results obtained for 15cm height samples. Furthermore, it was found that the distribution of the saturation level in the surface layer decreases as the surface layer approaches the edge of the structure. Finally, the samples with 7% AV have a higher drainage capacity, and hence are more susceptible to moisture damage compared with samples with 4% AV.

Underground coal mining operations induce ground movements, which may impact overlying hydrogeologic systems. Potential impacts mainly include changes in the hydraulic conductivity of overlying strata, decreasing of the hydraulic head and changes in water flow. The present research quantifies potential hydrogeologic impacts caused by underground mining through modeling of pre- and post-mining hydrogeologic systems. Three-dimensional conceptual hydrogeologic models were constructed with the Processing Modflow for Windows software package (PMWiN). The models are based on an actual case study, but were simplified in terms of geometry and material properties. Water flow was simulated under changing hydrogeologic properties. A number of scenarios were investigated including models with horizontal or inclined topography, featuring an aquifer overlying two longwall panels. The hydrogeologic properties of the models were estimated based on empirical relationships between the post-mining hydraulic conductivity and strain in the overburden. The strain regime in the overburden was estimated using the Surface Deformation Prediction System (SDPS) package, which allows calculation of surface deformations due to underground coal mining. The research focuses on changes in hydraulic heads; results indicate that hydraulic heads may decrease over undermined areas and may rebound as mining ceases. Water infiltration may occur from higher located overburden formations to lower formations due to mining induced changes in hydrogeologic properties.

The steady flow method (SFM), most commonly used for permeability measurement in the laboratory, is not applicable for tight rocks, higher rank coals and coals under highly stressed condition because of the difficulty in measuring steady-state gas flowrates resulting from the tight rock structure of. However, accurate estimation of permeability of highly stressed coals is pivotal in coalbed methane (CBM) operations in order to precisely and effectively model and project long-term gas production. A fast and accurate permeability measurement technique is, therefore, required to investigate gas flow behavior of CBM reservoirs. The pulse-decay method (PDM) of permeability measurement is believed to be better suited for low-permeability rocks. In this study, application of the currently used pulse-decay laboratory permeability measurement techniques for highly stressed coals were evaluated. Considering the limitations of these techniques in permeability measurement of unconventional gas reservoirs, such as coal and gas shales, the conventional PDM was optimized by adjusting the experimental apparatus and procedures. Furthermore, the applicability of an optimized PDM was verified numerically and experimentally. This dissertation is composed of five chapters. To complete the research objectives as discussed above, it is necessary to have a profound understanding of the basic theories, such as, gas storage mechanism, gas migration, and permeability evolution during gas depletion in coalbed reservoirs. In Chapter 1, a brief discussion regarding the basic knowledge of reservoir properties and transport mechanisms is presented. The chapter also provides the appropriate background and rationale for the theoretical and experimental work conducted in this study. Chapter 2 presents the transient pressure-decay technique in permeability measurement of highly stressed coals and verifies the validity of Brace et al.’s solution (1968) by comparing it with Dicker and Smits’s solution (1988) and Cui et al.’s solution. The differences between these three solutions are discussed in detail. Based on the established permeability trends from these different solutions, a persuasive suggestion is presented for selection of the best alternative when testing coal permeability. Furthermore, permeability is regarded as a coupled parameter, resulting from the combined effects of mechanical compression and “matrix shrinkage” caused by desorption of gas. To isolate the role of gas desorption from the coupled result, a series of experiments were carried out under constant effective stress condition and a stress-dependent permeability trend was established. Chapter 3 proposes an optimized experimental design in order to improve the accuracy of the calculated permeability for sorptive rocks. In order to verify the optimized design theoretically, a modified mathematical model is presented and describes the one-dimensional fluid flow in porous media by a partial differential equation. The numerical solutions of the model are presented graphically to evaluate the fluid flow behavior in porous media. Finally, the validity of Brace et al.’s solution when testing sorptive rocks, without the need of consideration on the compressive storage and sorption effect, is elucidated. Chapter 4 demonstrates the efficiency and applicability of the optimized PDM through its direct application to experimental work designed to establish the permeability trend under best replicated in situ conditions. In this chapter, CO2 was used as the test fluid to profile and characterize the pulse decay plots due to its higher affinity towards coal than methane, and then establish the stress-dependent-permeability trend for highly-stressed CBM reservoirs. In this chapter, Brace et al.’s solution was also verified by comparing the laboratory data and computer simulated results obtained from the optimized mathematical model proposed in Chapter 3. The experimental work demonstrates that the optimized technique can be used for permeability tests of sorptive rocks without the need to carry out additional experimental work required to measure rock porosities and sorption isotherms. Finally, a summary and future research perspectives are presented in Chapter 5.

No description available.

Pump and treat remediation is the most commonly used method to remediate contaminated aquifers, but the effectiveness decreases when heterogeneities are introduced. Fractures within the matrix cause large differences in hydraulic conductivity. The low hydraulic conductivity of the matrix acts as an area of storage for contaminant, allowing for attenuation of the plume. The attenuation of the plume causes the effectiveness of the system to decrease and cost of remediation to increase. In order to understand what parameters enhance contaminant storage in the matrix, rapid transport in fractures, and both of their influences on the efficiency of the pumping system, a hypothetical model was developed to simulate the release and remediation of a plume using pumping. The code used was HydroGeoSphere, which allowed for the interpretation of parameters influencing contaminant storage during the withdrawal phase of the pump and treat remediation by allowing transport of contaminant within both the matrix and the fractures. Matrix parameters of porosity and hydraulic conductivity influenced the effectiveness of the withdrawal system most. For instance, the difference in percent mass extracted between porosity values of 0.01 and 0.4 was 23.75%, while the difference between fracture lengths of 200 and 400 m was 5.59%. Fracture pattern influenced where the stored contaminant was located within the matrix. Downgradient of the source, six different fracture patterns resulted in a difference in relative concentration of 0.4 at the start of the withdrawal phase. Evaluation of remediation included both percent extraction of contaminant and finer scale remediation of the contaminant specifically within the matrix. Multiple length-scale observations helped determine how fracture and matrix parameters influence remediation in dual permeability media. / Geology

L’importance de gérer la crise provoquée par une catastrophe naturelle, et plus particulièrement par les inondations, nécessite le développement de systèmes d’évacuation efficaces. Un système d’évacuation efficace doit tenir compte de certaines contraintes, notamment celles liées au trafic sur le réseau, à l’accessibilité, aux ressources humaines nécessaires et aux équipements matériels (véhicules, points de rassemblent, etc ..). L’objectif principal de ce travail est d’apporter une assistance aux services techniques et aux forces de secours en termes d’accessibilité en proposant des itinéraires relatifs aux opérations de secours et d’évacuation des biens et des personnes. Nous considérons dans cette thèse, l’évacuation d’une zone urbaine de taille moyenne, exposée à l’aléa d’inondation. En cas d’inondation, la plupart des habitants seront évacués en utilisant leurs propres véhicules. Deux sites d’étude sont sélectionnés dans le projet ACCELL 1, val de Tours (Fr, 37) et val de Gien (Fr, 45). Protégé de l’aléa d’inondation par un ensemble de digues, le site du val de Tours est doté d’un système de prévision de crues fournie par le SPC 2 (DREAL 3) et le SCHAPI 4 permettant aux décideurs d’anticiper une crise majeure par une évacuation préventive. Contrairement au site tourangeau, le val de Gien peut bénéficier d’une évacuation de la population avant et pendant la catastrophe. L’inondation sur ce second val est du type lente par débordement (site partiellement digué), les coupures de routes au cours du temps sont prises en compte lors d’une évacuation pendant la crise. Notre objectif est de construire, pour chacun de ces deux sites, un plan d’évacuation, i.e., fixer pour chaque individu la date de départ et le chemin pour atteindre le point de rassemblement associé. Le plan d’évacuation doit éviter la congestion sur le réseau routier. Nous présentons ici un modèle d’optimisation spatio-temporel (STOM5) dédié à l’évacuation de la population exposée à une catastrophe naturelle et plus particulièrement à un risque d’inondation. / The importance of managing an urban site threatened or affected by flooding requires the development of effective evacuation systems. An effective evacuation system has to take into account some constraints such as the transportation traffic which plays an important role as well as others such as the accessibility, necessary human resources and material equipment (vehicles, assembly points, etc...). The main objective of this work is to bring assistance to the technical services and brigade forces in terms of accessibility by providing itineraries with respect to rescue operations and the evacuation of people and goods.We consider the evacuation of a middle size area, exposed to a risk, and more precisely to a risk of flooding. In case of flooding event, the most of inhabitants will be evacuated by themselves, ie., using their personal vehicles. Considered case here, the flooding can be forecast in advance, and then the population has few days (2-4) to evacuate. Our aimis to build an evacuation plan, ie., fixing for each individual the date of departure and the path to reach the assembly point (also called shelter) associated. Evacuation plan must avoid congestion on the roads of evacuation network.Here, we present a spatio-temporal optimization model for the evacuation of the population exposed to natural disasters, and more particularly to a flood risk.

Magmatism is a dominant process on Earth and Mars that has significantly modified and evolved the lithospheres of each planet by delivering magma to shallow depths and to the surface. Two common modes of volcanism are present on both Earth and Mars: central-vent dominated volcanism that creates large edifices from concentrating magma in chambers before eruptions and distributed volcanism that creates many smaller edifices on the surface through the independent ascent of individual magmatic dikes. In regions of distributed volcanism, clusters of volcanoes develop over thousands to millions of years. This dissertation explores the geology of distributed volcanism on Earth and Mars from shallow depths (~1 km) to the surface. On long time scales, distributed volcanism emplaces magmatic sills below the surface and feeds volcanoes at the surface. The change in spatial distribution and formation rate of volcanoes over time is used to infer the evolution of the source region of magma generation. At short time scales, the emplacement of lava flows in these fields present an urgent hazard for nearby people and infrastructure. I present software that can be used to simulate lava flow inundation and show that individual computer codes can be validated using real-world flows. On Mars, distributed volcanism occurs in the Tharsis Volcanic Province, sometimes associated with larger, central-vent shield volcanoes. Two volcanic fields in this province are mapped here. The Syria Planum field is composed three major volcanic units, two of which are clusters of 10s to >100 shield volcanoes. This area had volcanic activity that spanned 900 million years, from 3.5-2.6 Ga. The Arsia Mons Caldera field is associated with a large shield volcano. Using crater age-dating and mapping stratigraphy between lava flows, activity in this field peaked at ~150 Ma and monotonically waned until 10-90 Ma, when volcanism likely ceased.

No description available.

Parmi les torches à plasma microonde, la torche à injection axiale (TIA) est utilisée depuis de nombreuses années pour créer des espèces chimiquement actives dans des applications comme l'analyse de gaz, les traitements de surface et les traitements d'effluents gazeux. Notre étude porte sur l'énergie transférée par le plasma créé par cette torche à pression atmosphérique, qui trouve son intérêt notamment dans le chauffage de l'hélium pour la montée en altitude d'un ballon dirigeable. La TIA permet de coupler de l'énergie microonde (2.45 GHz) à un gaz injecté axialement à la sortie d'une buse. La TIA donne lieu à un plasma hors équilibre thermodynamique formé d'un dard de forte luminosité, avec une densité maximale de particules chargées à la sortie de la buse. Notre étude porte sur l'expérience et la modélisation de cette torche pour comprendre la répartition du champ électromagnétique, l'écoulement du système gaz/plasma et le transfert de chaleur du plasma au gaz.Des mesures par spectroscopie optique d'émission dans l'argon et l'hélium ont permis de trouver les températures du gaz (1500 K vs 3000 K) en fonction des conditions expérimentales (débit, puissance). Elles ont été estimées en ajustant les spectres ro-vibrationnels de N2 obtenus à ceux issus du logiciel SPECAIR. La mesure de la densité électronique (de l'ordre de quelques 10^14 cm^-3) a été réalisée dans un plasma d'hélium par élargissement Stark de la raie Hβ. Ces mesures ont un double objectif : obtenir des données d'entrée au modèle et valider ses résultats.La modélisation se partage en deux modules réalisés avec le logiciel COMSOL Multiphysics: (i) un module électromagnétique 3D qui résout les équations de Maxwell, (ii) un module hydrodynamique 2D qui résout les équations de Navier-Stokes pour le système gaz/plasma en prenant en compte les ions. Un module plasma, en cours de développement, résoudra les équations fluides pour les électrons et les ions du plasma.Cette modélisation réussit à prédire des températures similaires à celles obtenues expérimentalement et a permis de montrer l'influence du plasma sur l'écoulement et la température du gaz ainsi que l'efficacité du transfert de chaleur du plasma au gaz. / Among the microwave plasma torches, the axial injection torch (TIA) has been used for several years to create chemically active species, in applications such as gas analysis, surface processing and gaseous waste treatments. Our study concerns the energy transferred from the plasma created by the torch at atmospheric pressure, which finds its interest in particular in the heating of helium in a dirigible balloon to achieve its rise in altitude. The TIA allows the coupling of microwave energy (2.45 GHz) with a gas injected axially at the nozzle's exit. The TIA produces a non equilibrium plasma with a high luminosity and a maximum density of charged particles at the nozzle's exit. Our study involves both experiment and modelling of this torch in order to understand the distribution of the electromagnetic field, the flow of gas / plasma system and the plasma-to-gas heat transfer.Measurements by optical emission spectroscopy in argon and helium allowed to determine the gas temperature (1500K vs 3000 K) based on experimental conditions (flow, power). They were estimated by fitting the N2 ro-vibrational spectra obtained from air, using the SPECAIR software. The measurement of electron density (of about a few 10^14 cm^-3) was performed in a helium plasma by Stark broadening of the Hβ. Experiments have a double objective : to obtain input data for the model and to validate its results. Modelling uses two modules of the COMSOL Multiphysics software: (i) a 3D electromagnetic module, which solves Maxwell's equations, (ii) a 2D hydrodynamic module, which solves the Navier-Stokes equations for the gas / plasma system taking into account the ions. A plasma module, which solves the fluid equations for electrons and ions is in development This modelling succeeded in predicting temperatures similar to those obtained experimentally and showed the influence of plasma upon flow and the gas temperature and the efficiency of heat transfer from the plasma to the gas.

Le bassin crétacé de Tsagaan Els est situé dans le désert de Gobi en Mongolie. L’objectif de cette thèse est de mieux comprendre le fonctionnement hydrogéologique et hydrochimique de ce bassin endoréique afin de faciliter l’implantation de futurs projets miniers. Dans cette optique, un modèle hydrogéologique régional 3D a tout d’abord été développé sous MODFLOW. La calibration à partir des niveaux piézométriques mesurés sur les ouvrages présents au sein des licences et quelques puits nomades, aboutit à plusieurs solutions. Elles présentent chacune des conductivités hydrauliques en accord avec les tests de pompages, et des taux de recharge entre 0.6 et 3.1 mm/an, cohérents avec le climat actuel. Ce modèle a ainsi permis d’étendre nos connaissances piézométriques au-delà des licences et d’effectuer un bilan hydrique régional. Ensuite, l’âge des eaux a été estimé numériquement via ce modèle puis par des datations 14C. Une comparaison des résultats de ces méthodes a indiqué que les solutions présentant des taux de recharges élevés étaient plus probables que celles en présentant de plus faibles à conditions que les écoulements soient restés les mêmes durant les trente derniers milliers d’années. En parallèle, une étude hydrochimique portant sur les ions majeurs, le brome et les isotopes stable de l’eau (18O et 2H) a montré que l’origine de la salinité des eaux était principalement liée à la dissolution d’évaporites superficielles. En dernier lieu, un modèle 3D local, centré sur la playa terminale du bassin a permis de mieux comprendre le fonctionnement actuel et passé du bassin en s’appuyant sur l’évolution spatiotemporelle de la salinité. / The Tsagaan Els basin is located in the Gobi desert, in Mongolia. This thesis aims to better understand the hydrogeology and hydro-chemistry of the basin in order to optimize the future mining projects. To this end, a 3D groundwater flow model of the basin has first been developed under MODFLOW. The latter was calibrated using piezometric network data and levels in a few nomadic wells. Several solutions were found with hydraulic conductivity values in agreement with pumping tests and recharge rates between 0.6-3.1 mm/yr in agreement with the current climate. The model helped us to extend our piezometric knowledge beyond AREVA’s mining licenses and to establish a regional water balance model. Groundwater age was then estimated with this model and with 14C dating. A comparison of the results of these two methods showed that calibrated solutions with higher recharge are more likely than those with lower recharge under the hypothesis that groundwater flow has not changed significantly during the last 30 kyrs. Meanwhile, a hydrochemical study using major ions, bromines and the stable isotopes of water (18O and 2H) showed that groundwater salinity mainly comes from dissolution of surficial evaporites: likely gypsum and halite and possibly thenardite. Even though evaporation is the main driving force of the groundwater flow, this process, when taking place in subsurface, seems to have no real influence on δ18O and δ2H values of the groundwater. Last a 3D local groundwater flow model centered on the terminal playa and based on the spatiotemporal evolution of the salinity, led us to a better understanding of the past and current hydrogeological functioning of the basin.