Modeling fracture in geomaterials is essential to the understanding of many physical phenomenon which may posses natural hazards e.g. landslides, faults and iceberg calving or man-made processes e.g. hydraulic fracture and excavations. Continuum Damage Mechanics (CDM) models the crack as a solid region with a degraded stiffness. This continuum definition of cracks in CDM allows more feasible coupling with other forms of material non-linearity and eliminates the need to track complicated crack geometry. Using CDM to analyze fracture for the modeling of fracture in geomaterials encounters several challenges e.g.: 1) the need to model the multiple physical processes occurring in geomaterials, typically: coupled fluid flow and solid deformation, 2) the need to consider non-local damage and transport in order to capture the underlying long range interactions and achieve mesh-independent finite element solutions and 3) the elevated computational cost associated with non-linear mixed finite element formulations. The research presented in this thesis aims at improving the CDM formulations for modeling fracture geomaterials. This research can be divided into three main parts. The first is the introduction of a novel non-local damage transport formulation for modeling fracture in poroelastic media. The mathematical basis of the formulation are derived from thermodynamic equilibrium that considers non-local processes and homogenization principles. The non-local damage transport model leads to two additional regularization equations, one for non-local damage and the other for non-local transport which is reduced to non-local permeability. We consider two options for the implementation of the derived non-local transport damage model. The first option is the four-field formulation which extends the (u/P) formulation widely used in poroelasticity to include the non-local damage and transport phenomena. The second option is the three-field formulation, which is based on the coupling of the regularization equations under the assumptions of similar damage and permeability length scales and similar driving local stress/strain for the evolution of the damage and permeability. The three-field formulation is computationally cheaper but it degrades the physical modeling capabilities of the model. For each of these formulations, a non-linear mixed-finite element solution is developed and the Jacobian matrix is derived analytically. The developed formulations are used in the analysis of hydraulic fracture and consolidation examples. In the second part, a novel approach for CDM modeling of hydraulic fracture of glaciers is pretended. The presence of water-filled crevasses is known to increase the penetration depth of crevasses and this has been hypothesized to play an important role controlling iceberg calving rate. Here, we develop a continuum damage-based poro-mechanics formulation that enables the simulation of water-filled basal and/or surface crevasse propagation. The formulation incorporates a scalar isotropic damage variable into a Maxwell-type viscoelastic constitutive model for glacial ice and the effect of the water pressure on fracture propagation using the concept of effective solid stress. We illustrate the model by simulating quasi-static hydro-fracture in idealized rectangular slabs of ice in contact with the ocean. Our results indicate that water-filled basal crevasses only propagate when the water pressure is sufficiently large and that the interaction between simultaneously propagating water-filled surface and basal crevasses can have a mutually positive influence leading to deeper crevasse propagation which can critically affect glacial stability. In the third part, we propose a coupled Boundary Element Method (BEM) and Finite Element Method (FEM) for modeling localized damage growth in structures. BEM offers the flexibility of modeling large domains efficiently while the nonlinear damage growth is accurately accounted by a local FEM mesh. An integral-type nonlocal continuum damage mechanics with adapting FEM mesh is used to model multiple damage zones and follow their propagation in the structure. Strong form coupling, BEM hosted, is achieved using Lagrange multipliers. Since the non-linearity is isolated in the FEM part of the system of equations, the system size is reduced using Schur complement approach, then, the solution is obtained by a monolithic Newton method that is used to solve both domains simultaneously. The method is applied to multiple fractures growth benchmark problems and shows good agreement with the literature.

A presente dissertação enfoca as características de resistência ao cisalhamento e os mecanismos básicos que governam o fenômeno de atrito em rochas fraturadas. Especial atenção é dedicada à identificação de fatores geométricos e geotécnicos importantes e a sua relação com o comportamento e esforços resistentes de rochas fraturadas. A caracterização de fraturas por meio de parâmetros geomecânicos adequados permitirá incluí-los nos modelos de cálculo e simular mais realisticamente o comportamento geomecânico do maciço rochoso fraturado. / This thesis focuses on the shear strenght and mechanisms that change the shear characteristics of jointed rocks. Special attention was devoted to the identification of geometric and geotechnical factors and its relationship with the behavior and strenght of jointed rocks. The characterization of the fractures by apropriated geomechanical parameters Will permite to include them in the models and to simulate more realistically the behavior of fractured rock mass.

Este trabalho tem como objetivo o estudo do reaproveitamento da parte metálica e a caracterização dos óxidos presente no resíduo de granito gerado na etapa de desdobramento. Inicialmente, foi feita a caracterização química e física do resíduo através de análise química, difração de raios-X, microscopia eletrônica de varredura e análise granulométrica. Após a caracterização do resíduo, foi dado inicio aos processos para a recuperação do Fe metálico que envolveram: separação magnética, mesa concentradora e ciclonagem. A separação magnética foi realizada em três etapas: a primeira onde se utilizou um separador magnético a úmido de alta intensidade, onde foi utilizado apenas o campo magnético remanescente do equipamento. Na segunda etapa, onde o material magnético obtido na primeira etapa foi submetido a uma nova separação magnética manual utilizando um imã de terras raras. Na terceira etapa, o material magnético obtido com o imã de terras raras foi submetido a uma separação magnética manual com um imã ferrítico. Nos ensaios de mesa concentradora, foram realizadas variações na inclinação da mesa, freqüência de oscilação e vazão de água de lavagem. Já nos ensaios de ciclone, o parâmetro variado foi à pressão de alimentação. Foram realizadas variações nos parâmetros dos equipamentos com o intuito de se aperfeiçoar e definir os melhores parâmetros para a recuperação do Fe metálico. Após cada ensaio, foi realizada a análise química volumétrica para a determinação do teor de Fe metálico obtido em cada produto. Pelos resultados obtidos, o método de separação magnética foi a que apresentou os melhores resultados, sendo possível a obtenção de um concentrado ferroso com 93% de Fe metálico e um concentrado granítico com 0,6% de Fe metálico. Já nos ensaios de mesa concentradora, o melhor resultado obtido foi um concentrado ferroso com apenas 13,7% de Fe metálico, e nos ensaios de ciclone foi possível à obtenção de um produto com apenas 7,2% de Fe metálico. A partir do concentrado ferroso e granítico obtido na separação magnética foi realizada a caracterização através de microscopia eletrônica de varredura, difração de raios-X e análise granulométrica. A partir do concentrado ferroso obtido, foram produzidos briquetes com uso de 2% de cal hidratada como aglomerante. Foram realizados testes de resistência mecânica a verde e a seco nos briquetes produzidos. Foi obtido uma resistência mecânica a verde de no máximo 1,02 kN e a seco de no máximo 3,59 kN. / The aim of this work is to study the reuse of the metallic part and the characterization of oxides present in the waste from granite sawing. First, the chemical and physical characteristics of the waste were analyzed by chemical analysis, X-ray diffraction, scanning electron microscopy and size analysis. Procedures for the metallic iron recovery (magnetic separation, concentrator table, and cyclonic separation) were performed after the waste characterization. Magnetic separation was performed in three phases. First, using a high intensity wet magnetic separator, which only the remaining magnetic field of equipment was utilized. In the second phase, the magnetic material obtained in first phase was subjected to a new manual magnetic separation using rare earth magnets. In a third phase, magnetic material obtained with rare earth magnets was subjected to manual magnetic separation using ferrite magnets. In the experiments of concentrator table, were carried out changes in table inclination, oscillation frequency and wash water flow. For cyclone tests, the varied parameter was the water supply pressure. Variations in equipment parameters were performed in order to improve and decide the best parameters for recovery of metallic iron. After each experiment, volumetric chemical analysis was performed to determine the metallic iron content of each product. The results show that the magnetic separation method had the best results since it is possible to obtain a ferrous concentrated with 93.0 wt. % metallic iron and granite concentrated with 0.6 wt. % metallic iron. While for concentrator table tests, the best result presented a ferrous concentrated with only 13.6 wt. % metallic iron; and for cyclone tests, a product with only 7.2 wt. % of metallic iron was obtained. Ferrous and granite concentrated from magnetic separation were characterized by scanning electron microscopy, X-ray diffraction and size analysis. Using the obtained ferrous concentrated, briquettes were produced with 2 wt. % hydrated lime as binder. Produced briquettes were tested using dry and wet mechanical strength test. Wet mechanical strengths of up to 1.02kN were obtained, and a maximum of 3.59kN was registered to dry mechanical strength.

La sismique et la sismologie sont des moyens puissants pour comprendre la croûte terrestre.Ces deux méthodes reposent notamment sur une compréhension approfondie de la propagation des ondes sismiques dans des milieux sédimentaires saturés en fluides.Ce travail a pour but de comprendre les effets statique et dynamique du fluide sur la réponse élastique de roches clastiques saturées.Deux points spécifiques de l'interaction fluide-roche sont étudiées: (i) l'intéraction physico-chimique, le « shear weakening », affectant la réponse élastique de la roche; et (ii) l'interaction mécanique, le « frequency effect », induisant une dépendance des propriétés élastiques à la fréquence de mesure.Deux types de roches sont étudiés: les grès et les calcaires.Ces échantillons de roche sont sélectionnés pour leurs propriétés isotropes et leur forte concentration en un minéral dominant: le quartz pour les grès et la calcite pour les carbonates.Le phénomène de « shear weakening » est d’abord étudié pour de très faibles saturations en eau afin de tester l’effet de l'adsorption.Aucun affaiblissement n’est mesuré dans les carbonates, au contraire un affaiblissement élastique global est observé dans certains grès : Les modules de cisaillement et d’incompressibilité sont également affectés.L'effet ne semble pas provenir d'une différence intrinsèque entre les minéraux de quartz et de calcite, mais d’une différence microstructurale entre roches. Un modèle micromécanique est développé, montrant que les deux paramètres clef sont le caractère granulaire et le degré de cimentation de la roche.Le même résultat est obtenu pour les compressibilités mesurées lors des saturations totales en eau.Ces deux études montrent que l'adsorption est la cause du « shear weakening », et implique un affaiblissement élastique global dans les roches granulaires peu cimentées (gréseuses et probablement carbonatées).L'effet de fréquence est étudié dans des grès de Fontainebleau et de Berea. Deux méthodes sont étudiées, toutes deux basées sur le principe de "stress-strain" (i.e. contrainte-déformation): l'oscillation "isotrope" (de la pression de confinement) et "déviatorique" (de la contrainte déviatorique).Ces deux modes d'oscillations sont tout d’abord calibrés à l’aide de plusieurs standards (e.g. aluminium, verre, gypse, plexiglass).Les échantillons de roche, saturés par des fluides de différentes viscosités, sont ensuite mesurés avec ces deux modes d'oscillation.Pour le premier mode d'oscillation, dit "isotrope", ce travail a permis de (i) mettre en évidence trois régimes élastiques distincts;et (ii) mesurer à la fois la conséquence (i.e. dispersion et atténuation du module d'incompressibilité) et la cause (i.e. écoulement fluide global) de la transition en fréquence entre état drainé et état non-drainé.Pour le second mode d'oscillation, dit "déviatorique", le module de Young et le coefficient de Poisson sont mesurés sur une gamme de fréquence apparente de [10-3;105] Hz.Pour un échantillon de grès de Fontainebleau, les deux transitions élastiques sont observées. Les mesures sont cohérentes avec les théories existantes.Un modèle 1D, prenant en compte les conditions de bord du système, est finalement développé. Ce modèle donne des résultats cohérents, et explique l'effet du volume mort sur les propriétés mesurées dans le cas d'une oscillation « isotrope ». / Seismics or Seismology are powerful tools to investigate Earth's crust. However, both rely on seismic waves that travelled through fluid-saturated sedimentary layers. This work, mainly experimental, aims at understanding the static and dynamic effects of the saturating fluid on the elastic response of clastic rocks.In this framework, two specific studies are emphasized:(i) the rock-fluid physico-chemical interaction, often addressed as the "shear weakening" effect, thought to affect the rock overall elastic response; and (ii) the rock-fluid mechanical interaction, addressed as "frequency effect", thought to induce a dependence of elastic properties to the measuring frequency.Two main rock types are investigated: Sandstone and Limestone. All rock samples are chosen to be isotropic and composed of a dominant mineral content, i.e. quartz for sandstone and calcite for limestone.

Wear to mining equipment reduces operational efficiency. If wear rates can be predicted, appropriate matching of alloys to the mine' s geologic conditions can aid in improving the operational efficiency. This study addresses rock characteristics which lead to wear. Macroscopic rock tools which lead to wear include sharp edges and comers on rocks. During a rock/equipment interaction, these rock tools cause high point pressures on the surface of the equipment which leads to ductile cutting and gouging of the surface and subsequent removal of metal. Hard mineral grains, or grain tools, produce abrasion as the grains move across equipment surfaces. Grain and rock tools were analyzed for metamorphic, hydrothermally altered, plutonic, and sedimentary rocks from six mines and quarries. Grain tools were examined by petrographic analysis and Knoop microhardness: rock tools by uniaxial compressive tests, density, and rock size. Fourier analysis of rock and mineral shapes and abrasion tests were used to examine the evolution of tools. Prediction of wear rates appears most closely related to uniaxial compressive strength, Knoop microhardness, and quartz content. Uniaxial compressive strength relates to rock tool endurance; Knoop microhardness contrast between mineral grains and matrix/cement influences evolution of tools during surface interactions; quartz content relates to the abrasive capacity of a rock surface.

Magma recharge events and subsequent mixing processes are understood to precede volcanic eruptions. Textural evidence of intrusion of hot, mafic magma into a cooler, rheologically locked silicic magma is commonplace. Solidified "blobs" of injected magma, called enclaves, are evidence of magma mixing, but the petrological and mechanical conditions during their formation are debated. Mount Hood, Oregon consistently erupts andesite bearing compositionally similar enclaves. These enclaves are evidence of mingling and mixing of two magmas. However, due to the compositional similarity between enclave and host lava (e.g. ~1-5 wt.% difference in SiO2), it is unclear whether the preserved enclaves represent; 1) partially hybridized mafic melt remaining after mixing with significant crystal exchange with the host magma or 2) the preserved remnants of the intruding magma during recharge, with no homogenization or crystal exchange with the host magma. The aim of this study is to understand how and why enclaves form in compositionally similar host magmas, such as those at Mount Hood. Building off previous research, we utilize a combination of field observations, chemical analyses, and numerical modeling to constrain the rheology of the magmas prior to and during mixing. The degree of magma mixing is dependent on the viscosity contrast between the host and intruding magmas. Since these magmas are similar compositionally, variations in other magmatic properties such as crystallinity, and therefore temperature, and density may drive the viscosity differences between the host and intruding magmas needed for enclave formation. The enclaves at Mount Hood are vesicular (13-28%), coarse-grained; made up of mainly groundmass crystals (200-450 µm) with sparse microlites (< 200 µm), glass (450 µm) proportions, and rarely contain quenched margins. Additionally, crystals within the host magma show preferential alignment along the margins between host and enclave, suggesting a fluid behavior of the host magma during mixing. Based on textural and compositional evidence, we hypothesize that the intruding magma was buoyant, viscous, and crystalline, due to decompression-induced crystallization and exsolution of volatiles, during recharge and ascent to the shallow magma reservoir. Injection and underplating of the viscous crystalline intruding magma into a hot convecting host magma induces enclave formation. Crystallization temperatures differ by only 6-15 °C between host and enclave lavas, derived by the two pyroxene geothermometry method by Putrika (2008). These crystallization temperatures are consistent with crystallization in compositionally similar magmas. However, with such similar crystallization and liquidus temperatures, maintaining a viscosity contrast between the mixing magmas for enclave survival after formation suggests other properties, apart from temperature, must explain the viscosity contrast needed for enclave survival after enclave dispersal and thermal equilibration occurs. The presence of bubbles, from exsolution during crystallization, within the enclave magma increases the viscosity while simultaneously decreasing the density. Therefore, the presence of bubbles increases the viscosity of the intruding magma and maintains the viscosity contrast during the mixing process after thermal equilibration occurs. Additionally, if degassing occurs, rapid crystallization maintains the high viscosity of the enclaves. The enclaves observed at Mount Hood represent the solidified remnants of the last recharge event prior to eruption. The presence of compositionally similar enclaves and host lavas suggest a transient precursor event just prior to eruption at Mount Hood and can be applied to other recharge-driven arc volcanic systems.

Three volcanic domes and related volcanic rocks of Tertiary age are located near Etna, Utah, in Box Elder County. The domes follow a north-south trend and are fault controlled. Flow structure indicates a change from a less viscous, flow-forming lava which produced an exogenous dome to a more viscous lava which formed endogenous domes. Associated pyroclastic deposits are negligible. The volcanic rocks are composed of porphyritic rhyolite and rhyolitic vitrophyre having phenocrysts of quartz, sanidine, plagioclase and biotite with minor amounts of Fe-Ti oxides, hypersthene, allanite and calcic amphibole. Quartz and sanidine phenocrysts are generally embayed whereas plagioclase phenocrysts are euhedral and extensively zoned. Average whole-rock chemical analyses yield: SiO2, 77.13; TiO2, 0.12; Al2O3, 11.01; Fe2O3, 0.9; FeO, 0.35; MnO, 0.02; MgO, 0.19; CaO, 0.82; Na2O, 2.93; K2O, 4.99; P2O5, 0.03; H2O+, 1.17; H2O-, 0.22; total, 99.94 weight percent. Coexisting Fe-Ti oxide microphenocrysts yield equilibration temperatures ranging from 872° to 684°C while respective log f0 2 values range from -13.5 to -19.5. These temperatures are comparable to temperatures obtained using the plagioclase-glass geothermometer at a water pressure of 1 kb. Mineral buffer reactions yield water fugacities with corresponding water pressures up to 4.9 kb. Assuming water pressure equals total pressure, calculated depths of approximately 18 km are obtained indicating an origin within the crust. High silica values and high alkali to calcium ratios indicate that ix the lavas are chemically similar to bimodal rhyolite-basalt assemblages located in other areas of the western United States. Small outcrops of basalt, located west of the Etna area, also suggest a bimodal assemblage. Viscosity values (log n) for the south dome range from 7.05 to 10.35 suggesting that there was a change from a less viscous to a more viscous lava. Comparisons between hydrous and dry calculations indicate that falling water content as well as decreasing temperature were responsible for the change in viscosity and resulting structural changes.

Abstract not available

Thesis (Ph. D.)--Oregon State University, 2005. / "November 2005." Includes bibliographical references. Also available via Internet.

This thesis focuses on the detection of marble sculpture forgery made of cultured marble. Cultured marble is a mixture of marble dust, polyester and accelerators. Thus chemical analysis of cultured marble would give declined levels of calcium when compared to authentic sculptures. Since sample removal is a problem when dealing with archaeological heritage, the instrument used was portable X-Ray Fluorescence device which provides in situ analysis of the samples. Device has been used to analyze six authentic and four forgery sculptures. Seven of the sculptures were provided by Anatolian Civilizations Museum and three of them were provided by a sculpture workshop, Ak