[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.

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.

O processo de irradiação de gemas com raios gama de forma a melhorar as cores é bem aceito na indústria e comércio de jóias. Essas gemas são processadas em irradiadores industriais que são otimizados para outros fins. Para tal, utilizam principalmente aparatos para irradiação dessas pedras no fundo das suas piscinas de armazenamento das fontes, com um aproveitamento menor que o desejado, principalmente pela variação das taxas de dose encontrada nesses dispositivos. O desenvolvimento de um projeto de concepção, que estabelece os princípios físicos de funcionamento e formas de construção do novo tipo de equipamento, foi realizado nesse trabalho. O dispositivo sugerido baseia-se no princípio de rotação e translação circular de cestos em órbitas externa e interna a um porta-fontes cilíndrico, como um sistema planetário. O dispositivo foi idealizado para expor as gemas à irradiação no fundo da piscina, onde estão as fontes. Assim, essas fontes ficam permanentemente blindadas pela lâmina d'água. O irradiador é classificado como categoria III pela AIEA. Para verificar a viabilidade física do princípio básico, ou seja, o uso de cestos cilíndricos rotativos, foram realizados ensaios no Irradiador Multipropósito do CTR, no IPEN, além de simulações correlacionadas usando o aplicativo CADGAMMA adaptado para simular a irradiação submersa. A construção do irradiador definitivo leva ao aumento da qualidade da irradiação das pedras, com maior controle sobre as doses no produto. O custo operacional é significativamente reduzido pois o dispositivo foi otimizado para o beneficiamento pretendido. / The gemstones gamma irradiation process to enhance the color is widely accepted for the jewelry industry. These gems are processed in conventional industrial gamma irradiation plant which are optimized for other purposes, using underwater irradiation devices with high rejection rate due to it's poor dose uniformity. A new conception design, which states the working principles and manufacturing ways of the device, was developed in this work. The suggested device's design is based on the rotation of cylindrical baskets and their translation in circular paths inside and outside a cylindrical source rack as a planetary system. The device is meant to perform the irradiation in the bottom of the source storage pool, where the sources remain always shielded by the water layer. The irradiator matches the Category III IAEA classification. To verify the physical viability of the basic principle, tests with rotating cylindrical baskets were performed in the Multipurpose Irradiator raised in the CTR, IPEN. Also, simulations using the CADGAMMA software, adapted to simulate underwater irradiations were performed. With the definitive irradiator, the irradiation quality will be enhanced with better dose control and the production costs will be significantly lower than market prices due to the intended treatment device's optimization.

O processo de irradiação de gemas com raios gama de forma a melhorar as cores é bem aceito na indústria e comércio de jóias. Essas gemas são processadas em irradiadores industriais que são otimizados para outros fins. Para tal, utilizam principalmente aparatos para irradiação dessas pedras no fundo das suas piscinas de armazenamento das fontes, com um aproveitamento menor que o desejado, principalmente pela variação das taxas de dose encontrada nesses dispositivos. O desenvolvimento de um projeto de concepção, que estabelece os princípios físicos de funcionamento e formas de construção do novo tipo de equipamento, foi realizado nesse trabalho. O dispositivo sugerido baseia-se no princípio de rotação e translação circular de cestos em órbitas externa e interna a um porta-fontes cilíndrico, como um sistema planetário. O dispositivo foi idealizado para expor as gemas à irradiação no fundo da piscina, onde estão as fontes. Assim, essas fontes ficam permanentemente blindadas pela lâmina d'água. O irradiador é classificado como categoria III pela AIEA. Para verificar a viabilidade física do princípio básico, ou seja, o uso de cestos cilíndricos rotativos, foram realizados ensaios no Irradiador Multipropósito do CTR, no IPEN, além de simulações correlacionadas usando o aplicativo CADGAMMA adaptado para simular a irradiação submersa. A construção do irradiador definitivo leva ao aumento da qualidade da irradiação das pedras, com maior controle sobre as doses no produto. O custo operacional é significativamente reduzido pois o dispositivo foi otimizado para o beneficiamento pretendido. / The gemstones gamma irradiation process to enhance the color is widely accepted for the jewelry industry. These gems are processed in conventional industrial gamma irradiation plant which are optimized for other purposes, using underwater irradiation devices with high rejection rate due to it's poor dose uniformity. A new conception design, which states the working principles and manufacturing ways of the device, was developed in this work. The suggested device's design is based on the rotation of cylindrical baskets and their translation in circular paths inside and outside a cylindrical source rack as a planetary system. The device is meant to perform the irradiation in the bottom of the source storage pool, where the sources remain always shielded by the water layer. The irradiator matches the Category III IAEA classification. To verify the physical viability of the basic principle, tests with rotating cylindrical baskets were performed in the Multipurpose Irradiator raised in the CTR, IPEN. Also, simulations using the CADGAMMA software, adapted to simulate underwater irradiations were performed. With the definitive irradiator, the irradiation quality will be enhanced with better dose control and the production costs will be significantly lower than market prices due to the intended treatment device's optimization.

This research introduced a geological perspective into an archaeological setting, the Ness of Brodgar, a Middle to Late Neolithic site in the West Mainland of Orkney. Discovered in 2003, the site is located on an isthmus of land between two lochs and is equidistant between the Ring of Brodgar and the Stones of Stenness stone circles. The site consists of more than two dozen drystone buildings encircled by a massive wall. To date, ten per cent of the site has been excavated. This research established a systematic framework of protocols and procedures for the recovery, macro geological assessment and identification of the rock and mineral species in the non-tool, non-structural rocks, termed Foreign Stone for this research. Once identified, the frequency and distribution of the rock in the Foreign Stone finds were calculated, providing a geological basis for understanding any patterns of rock choice across the site. Integrated into a more conventional archaeological study of the Worked Stone artefacts was a systematic macro petrological analysis of these finds. Additionally, selected segments of the interior drystone walling were assessed to identify the rock in the various members. These petrologic analyses combined to provide insight into the range of rocks transported to and utilized within the site. Comparative analysis of the data from all three aspects, Foreign Stone, Worked stone and walling, was undertaken to identify trends in frequencies and patterns of use of the various rock species. Archival and more current information on the petrologic resources available within Orkney were synthesized in a gazetteer identifying the location(s) of rock outcrops and deposits. This permitted the source location(s) of many of the rocks from the Ness of Brodgar to be identified.

O polimento de rochas ornamentais na indústria brasileira é um processo empírico. Nesse processo, elementos como tempo, velocidade de rotação e carga aplicada na politriz são combinados de diversas maneiras para a obtenção do brilho. O presente trabalho, a partir de ensaios no Simulador de Polimento de Rochas (SPR), obteve informações mais precisas sobre quais combinações envolvendo essas variáveis são as mais eficientes para se atingir o brilho ideal em cada tipo de rocha. Para alcançar os resultados foram executadas e comparadas nove combinações para cada uma das rochas estudadas, considerando as influências das características composicionais, estruturais e texturais. Foram feitas modificações e adaptações nos aparelhos SPR e Glossmeter, uma vez que apresentavam a possibilidade de afetar a veracidade dos resultados. Os resultados e análises feitas mostram que é possível eliminar uma etapa abrasiva no processo de polimento. Cada tipo de rocha responde de maneira distinta em relação às combinações para obtenção do brilho ideal, levando à uma combinação específica para cada rocha. Os aprimoramentos do processo obtidos podem promover a redução custos para os fabricantes em relação a tempo, energia e abrasivos. / The ornamental stones polishing in the industry is considered an empirical process. In this process, variables such as time, rotation speed and intensity of the load applied are combined in different operation conditions to obtain the desired brightness. Using the Polishing Rocks Simulator (SPR), this present research aims to obtain information about which combinations of these variables are the most efficient to achieve the desired brightness in each type of rock. To achieve these objectives nine combinations were compared over three types of rocks in order to analyze the influence of each rock characteristics such as composition, structure and texture. Some modifications and adjustments were made on the Glossmeter and the SPR because they could influence the results accuracy. The obtained results and analysis shows that a step can be eliminated in the abrasive polishing process. Each type of rock responds differently to the employed combinations to reach the desired brightness. These analyses conduct to a specific combination for each rock. The achieved process improvement can reduce the costs for the industry in respect of time, energy and abrasives.

No description available.

Thesis. 1977. Ph.D.--Massachusetts Institute of Technology. Dept. of Materials Science and Engineering. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Vita. / Includes bibliographical references. / Ph.D.

Reconnaissance work and high-density sampling of volcanic rocks at the Quaternary Tatara-San Pedro complex (TSPC) in the Southern Volcanic Zone (SVZ) of Chile has yielded one of the most complete eruptive chrono-stratigraphies and comprehensive geochemical datasets of any arc volcano on Earth. The TSPC is a large frontal arc stratovolcano within the SVZ that exhibits a wide compositional diversity of lavas from basalt to rhyolite, covering most of the ranges in major and trace element contents across the SVZ. The TSPC occupies a pivotal position within the SVZ, where it is "intermediate" in terms of geophysical and geochemical characteristics between northern and southern SVZ volcanoes. The large TSPC dataset and stratigraphic control provides a unique opportunity to elucidate magma source heterogeneity and distinguish between contributions from upper mantle, subducted slab, and crust in a volcanic complex overlying relatively thick continental crust. Furthermore, the results of this investigation provide important constraints about the role of various recycled materials in generating the SVZ mantle and implications for along-arc magmatism and geochemical variability. TSPC magmas least impacted by crustal contamination (evolved lavas are filtered out on the basis of > 56 wt.% SiO2 and Rb/Y >1.75) have compositions bounded by three chemically and isotopically distinct mantle-derived end-members. The `prevalent TSPC mantle' end-member, which includes the largest number of analyzed lavas, is interpreted to represent melts of the upper mantle below TSPC that has been modified by long-term subduction. A second end-member shows extreme depletions in incompatible high field strength elements (HFSE) and the lowest concentrations of fluid-immobile incompatible elements, but has the highest aqueous fluid-mobile/immobile element ratios at the volcano (e.g., Sr/Nd and Pb/Ce). The source of these `low HFSE' magmas is `prevalent TSPC mantle' that experienced previous melt extraction, followed by more recent melting due to infiltration of solute-rich fluid from the subducting basaltic Nazca oceanic crust. A third end-member is enriched in incompatible elements and has the lowest Nd-Hf and highest Sr isotope ratios. This `TE enriched' end-member has common chemical characteristics with behind-the-arc basalts, indicating derivation from trace element-enriched behind-the-arc South American mantle that has been advected trenchward into the convecting mantle wedge. Determining the composition and relative input of slab-derived components to the SVZ mantle wedge has remained elusive for the last 2+ decades because of inadequate datasets and the controversial role of crustal contamination within the thick Andean continental crust. The `prevalent TSPC mantle' magmas, which best represent melts of the subduction-modified mantle wedge composition beneath the TSPC, provide important constraints on both the composition of the "pre-subduction" mantle and geochemical modifications by way of subduction. Mass-balance modeling suggests that the source of `prevalent TSPC mantle' magmas has been generated by a two-stage, three component mixing process. Isotopic and trace element evidence indicate that ~7-11% bulk subducted Chilean trench sediment has been added to an `E-MORB-like' pre-subduction mantle composition. This mantle mixture is further infiltrated by ~4% solute-rich fluid derived from the subducted Nazca basaltic oceanic crust. Trace element patterns of end-member `prevalent TSPC mantle' magmas are best fit by a two-stage partial melting model whereby the residual mantle, after a small degree melt extraction (F = 0.1%), undergoes F = 22% partial melting. The high melt fraction appears to potentially correspond with large volumes of solute-rich fluid released from the subducted Mocha Fracture Zone (MFZ). Although geochemical attributes of mafic TSPC magmas suggest that they are all derived from the same general mantle framework operating below the complex, one lava sequence appears to deviate. The mantle origins of the Upper Placeta San Pedro Sequence (UPSPS) have remained elusive since first being studied. It is a well-characterized basaltic lava series that erupted over a short interval at ~235-240 ka with highly variable incompatible element abundances and a large xenocrystic cargo. The new comprehensive chemical and radiogenic isotope (Sr-Nd-Pb-Hf) dataset, along with stratigraphic control and understanding of the larger-scale geochemical variability at the TSPC, provides fresh perspectives about the mantle sources and evolution of UPSPS magmas. While the UPSPS magmas are derived from the same sources as other TSPC magmas, they have undergone a unique petrogenetic evolution. This is evident from decoupled trace element-isotopic trends that are difficult to reconcile with other mafic TSPC magmas. Based on the Nd-Hf isotope ratios and trace element ratios, the two UPSPS unit magmas are derived from depleted-`TE enriched' and `prevalent TSPC mantle' sources. High ratios of aqueous fluid-mobile/immobile elements, such as high Pb/Ce and Sr/Nd, as well distinctive Sr and Pb isotope ratios, indicate that the UPSPS magmas were generated through fluxing of the mantle wedge, already depleted by melt removal by an solute-rich fluid derived from the subducted Pacific oceanic crust as well as the overlying trench sediment, which caused it to melt.

Mantle xenoliths allow us to investigate the geochemical and dynamic evolution of the mantle beneath the western margin of Antarctica and reconstruct a timeline of geologic events that are obscured on the surface. For this study, mantle xenoliths, brought to the surface by recent volcanism, were collected along a transect from the rift shoulder and into the rift basin in the western margin of the West Antarctic Rift System (WARS), thus providing a recent snapshot of the lithospheric mantle after major episodes of rifting. The second chapter of my thesis focuses on determining the age and persistence of the mantle within the rift. The rhenium-osmium (Re-Os) isotope system has proven to be an invaluable tracer of the tectonic history of the lithospheric mantle and can constrain the age of melt extraction and subsequent stabilization of the lithospheric mantle. This allowed us to track the age of the lithospheric mantle across this rifted margin. Os isotopes, combined with major element compositions, reveal widespread Paleoproterozoic (1.7-2.4 Ga) stabilization of the lithosphere and subsequent preservation, suggesting the lithosphere has dynamically thinned in response to rifting. Major element data allowed us to place temperature (T) constraints on the mantle and characterize the thermal history in the WARS. This study also revealed the oldest lithosphere ages recorded in Antarctica (3.3 Ga) and is the first to report ages that coincide with adjacent crustal ages, thus confirming the coupled relationship between the lithospheric mantle and continental crust. An integral factor controlling the composition of magmas generated at Earth’s surface is the composition of the SCLM. Magmas generated at depth must pass through it, and subsequently may take on geochemical signatures of the lithosphere, or may leave behind geochemical imprints of the migrating magma in the SCLM. Trace elements provide a means to investigate both the depletion and re-enrichment history of the SCLM. The third chapter of my thesis investigates the metasomatic overprinting of the Paleoproterozoic SCLM. Metasomatism, which is the chemical alteration of a rock by a migrating melt and/or fluid, leaves behind diagnostic signatures of the metasomatizing agent (e.g. subduction related fluids or carbonated melts). This can occur cryptically, where a melt percolates through the rock, changing the composition of the rock, but not the lithology. Modal metasomatism produces new mineral phases that are not typically expected in the rock. In xenoliths, trace elements enable us to decode geochemical signatures, and determine the sources of metasomatism. The WARS lithosphere has experienced varying degrees of re-enrichment, broadly characterized by low high field strength element (HFSE) abundances and rare earth element (REE) enrichments that correspond with carbonatite metasomatism. In addition, the presence of secondary hydrous phases (e.g. amphibole and phlogopite) imparted distinct geochemical signatures, revealing that the SCLM beneath the WARS was modified by reactive porous flow with an evolving metasomatic fluid/melt. Widespread Cenozoic rift-related volcanism (<20 Ma) is observed throughout the western margin of the East Antarctic Craton. It has been proposed that the Cenozoic basaltic volcanism in the region of our study site originated from a SCLM source that had been metasomatized during subduction along the paleo-Pacific margin of Gondwana, and subsequent extension in the WARS during the Late Cretaceous (~90 Ma). The fourth chapter of my thesis utilizes strontium (Sr), neodymium (Nd), and hafnium (Hf) isotopes to date depletion and refertilization events in the lithosphere, as well as understand the role of the SCLM in the formation of WARS volcanism. Together with lithologic features (e.g. presence of hydrous phase additions), Sr and Nd isotopic ratios in WARS xenoliths provide a geochemical link to the Cenozoic rift-related magmatism, and supports the SCLM’s role in the formation of diffuse alkaline magmatism throughout the region. Lu-Hf isotope model ages add a constraint on the timing of melt depletion, and establish a relationship between depleted and refertilized domains. Sr isotopes constrain a genetic link between the metasomatized Archean lithosphere sampled on the rift shoulder and the highly radiogenic character of the Ferrar flood basalts, and indicate long-term storage of subduction modified mantle domains in the SCLM. The Sm-Nd isotope system is variably overprinted by metasomatism throughout the WARS. The most highly metasomatized location produces a well-correlated isochron that indicates that the SCLM acquired its trace element metasomatic signature about 130 Ma ago, during the late stages of subduction along the paleo-Pacific margin of Gondwana.