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published_or_final_version / Civil Engineering / Master / Master of Science in Engineering

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The dynamic properties of clay deposits under seismic or wave loading conditions must be well understood to assure dynamic stability of structures founded on such soil. The dynamic shear modulus and damping appear to be a complex function of many variables, and a wide range of values have been reported in the literature. Consequently, considerable uncertainty exists in choosing the appropriate values of shear modulus and damping for a particular problem. This thesis presents a study of the influence of various factors on the shear modulus and damping of a marine clay using a resonant column/torsional shear device. In particular, the influence of factors such as shear strain amplitude, effective confining stress, stress history, frequency (strain rate), and secondary time-dependent behaviour are examined. The pore pressure response is also studied. The shear modulus was found to degrade for shear strains above 0.005%. The strain dependency was found to be well represented by a single normalized modulus reduction curve regardless of the confining pressure or overconsolidation ratio. Slower strain rates resulted in smaller values of shear modulus. Of the variables studied, the duration of sample confinement was found to be the most imporant factor affecting the material damping. Above 0.005% strain, the damping of the marine clay increased with shearing strain amplitude. No significant effect of confining pressure and stress history on damping was observed at any strain level. As well, the material damping was found to be relatively independent of loading frequency. Both the shear wave velocity and damping obtained in this study were found to be consistent with the in situ values determined using the seismic cone penetration test. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

The study was undertaken to investigate the effects of rate of strain and structure on the development of true cohesion and true friction in a saturated cohesive soil. The soil investigated was a locally available sensitive clay. The various methods proposed by different investigators to measure true cohesion and true friction are reviewed. After some trials the method adopted was that proposed by Bishop (1962) in which over-consolidation is used to obtain samples at the same void ratio but different initial effective stress. All samples were tested in undrained triaxial compression. To investigate the effects of rate of strain on the development of true cohesion and true friction, the results were compared for two identical sets of samples tested at two significantly different strain rates. To investigate the effects of structure on the development of true cohesion and true friction, a technique was developed to remold the specimens in place at constant void ratio after they had been sheared in the undisturbed state. Remolding has the effect of breaking-down the structure of a sensitive undisturbed clay. The test results from undisturbed and remolded samples were compared. In general the investigation showed that in the undisturbed clay the strength in terms of maximum (Ϭ₁-Ϭ₃) decreased with decreasing strain rate, however, the strength in terms of (Ϭ⁻₁/Ϭ⁻₃) max, was not significantly affected by strain rate when compared on an effective stress basis. In remolded clays there was a tendency for the strength in terms of maximum (Ϭ₁-Ϭ₃) to increase with increasing time to failure. In the undisturbed clay true cohesion developed rapidly at small strains, attained a peak and decreased to zero at large strains. True friction was mobilized slowly and attained a maximum value at large strains. At strains less than 8% both true friction and true, cohesion increased with increasing strain rate. However, at large strains true friction and true cohesion were not affected by strain rate. In the remolded clay true cohesion developed slowly attaining a small but significant value which remained constant with strain. The maximum value of true cohesion in the remolded clay was very much lower than that for the undisturbed clay. The development of true friction with strain was essentially unaffected by remolding and both the undisturbed and remolded clay developed about the same maximum value of true friction at large strains. The observed behaviour was explained in terms of changes in clay structure with strain rate and remolding. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

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As argilas são materiais naturais, terrosos, de granulação fina e que apresentam plasticidade em contato com a água. A aplicabilidade das argilas na área cosmética depende da sua composição química e mineralógica, porém esses materiais possuem elevada biocarga, sendo o controle dessa carga microbiana necessário antes da aplicação das mesmas na área cosmética. Além disso, devido a variabilidade na composição das mesmas, estudos que avaliem a composição química e a aplicabilidade das argilas são necessários. O presente trabalho consistiu na caracterização de quatro tipos diferentes de argilas, provenientes do resíduo da extração de areia de mineradoras do interior do estado de São Paulo, Brasil, por meio de técnicas de fluorescência de raios X, difração de raios X, análise térmica, distribuição de tamanho de partículas por dispersão a laser, avaliação da área superficial, espectroscopia no infravermelho com transformada de Fourier e avaliação da morfologia das argilas. A carga microbiana das argilas foi avaliada e foram propostos dois métodos de descontaminação. As argilas foram incorporadas em gel hidrofílico e emulsão não iônica passando por um teste de estabilidade acelerada durante 90 dias, nos quais as amostras foram armazenadas a temperatura de 20°C ±2°C, 2°C ±2°C e 45°C ±2°C, juntamente com os respectivos padrões (emulsão e gel sem argila). Foram avaliadas, durante o teste, características organolépticas das formulações, assim como pH, espalhabilidade, viscosidade, resistência à centrifugação e diâmetro de partículas. As formulações que apresentaram os melhores resultados nesses testes foram submetidas ao teste de irritabilidade dérmica in vivo. Avaliou-se o potencial citotóxico in vitro das argilas pelo ensaio MTT, brometo de 3-(4,5 dimetiltiazol-2-il)-2,5-difeniltetrazolio, e coloração Giemsa. A caracterização por DRX permitiu verificar a presença de caulinita e ilita, como principais fases mineralógicas identificadas nas amostras, além do silício como o mineral em maior concentração para todas as amostras. O diâmetro médio de partícula variou de 3,6 a 24,1 μm e a área superficial de 22,8 a 38,57 m2/g, sendo que a Argila III foi a que apresentou o maior valor de área superficial. Os métodos de descontaminação propostos, utilizando associação de álcool 70°GL e calor seco a 120°C e somente o calor seco, promoveram redução da carga microbiana das amostras adequando as argilas aos limites exigidos para uso em cosméticos. Os resultados obtidos na avaliação da estabilidade das formulações, nas condições testadas, demonstraram que as argilas alteraram parâmetros como viscosidade, espalhabilidade e diâmetro de partículas. O valor de pH não sofreu alterações com a adição das argilas e não houve alterações após a centrifugação das amostras. Dentre os veículos estudados, os géis apresentaram maior estabilidade que as emulsões, frente às condições testadas e os parâmetros avaliados. Dessa forma, os géis contendo os quatro tipos de argila e o gel padrão, foram escolhidos para avaliação da irritabilidade dérmica in vivo. Verificou-se que nenhuma das amostras causou irritação nos voluntários nas condições testadas. No teste de citotoxicidade todas as argilas demonstraram uma reduzida atividade citotóxica. Considerando os testes realizados, as argilas estudadas possuem uma atividade promissora quanto à aplicabilidade na indústria cosmética. / Submitted by Ana Guimarães Pereira (agpereir@ucs.br) on 2017-05-23T17:45:10Z No. of bitstreams: 1 Dissertacao Juliana da Silva Favero.pdf: 13674482 bytes, checksum: 044596817fd9bfbe4791fbbff740b2ed (MD5) / Made available in DSpace on 2017-05-23T17:45:10Z (GMT). No. of bitstreams: 1 Dissertacao Juliana da Silva Favero.pdf: 13674482 bytes, checksum: 044596817fd9bfbe4791fbbff740b2ed (MD5) Previous issue date: 2017-05-23 / Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul, FAPERGS. / Clays are natural, earthy, fine-grained materials that exhibit plasticity in contact with water. The applicability of the clays in the cosmetic area depends on their chemical and mineralogical composition, but these materials have huge bioburden and the control of this bioburden is necessary before applying them in the cosmetic area. Moreover, due to the variability in their composition, studies that evaluate the chemical composition and the applicability of the clays are necessary. The present work consisted in the characterization of four different types of clays, originated from the sand extraction residue of mining activities in the hinterland of São Paulo state, Brazil, using X-ray fluorescence, X-ray diffraction, thermogravimetric analysis, particle size distribution by laser dispersion, surface area evaluation, Fourier transform infrared spectroscopy and clay morphology evaluation. The bioburden of the clays was evaluated and two methods of decontamination were proposed. The clays were incorporated in hydrophilic gel and nonionic emulsion under an accelerated stability test during 90 days, in which the samples were stored at a temperature of 20 ° C ± 2 ° C, 2 ° C ± 2 ° C and 45 ° C ± 2 ° C, with the respective standards (emulsion and gel without clay). The organoleptic characteristics of the formulations, as well as pH, spreadability, viscosity, centrifugation resistance and particle diameter were evaluated during the test. The formulations with the best results in these tests were submitted to the in vivo dermal irritability test. The in vitro cytotoxic potential of clays was evaluated by MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, and Giemsa. The XRD characterization allowed to verify the presence of kaolinite and illite, as the main mineralogical phases identified in the samples, besides silicon as the mineral in the highest concentration for all the samples. The average particle diameter ranged from 3.6 to 24.1 μm and the surface area of 22.8 to 38.57 m2/g, and Clay III showed the highest surface area value. The proposed decontamination methods, using a combination of alcohol 70 ° GL and dry heat at 120 ° C and dry heat alone, promoted reduction of the bioburden of the samples, adjusting the clays to the limits required for cosmetics application. The results obtained in the evaluation of the stability of the formulations, under the conditions tested, showed that the clays changed parameters such as viscosity, spreadability and particle diameter. The pH value did not change with the addition of the clays and there were no changes after centrifugation of the samples. Among the studied vehicles, the gels presented greater stability than the emulsions, in front of the conditions tested and the evaluated parameters. Thus, the gels containing the four types of clay and the standard gel were chosen for evaluation of dermal irritability in vivo. None of the samples induced irritation in volunteers under the conditions tested. In the cytotoxicity test all the clays showed a reduced cytotoxic activity. Considering the tests performed, the clays studied have a promising activity regarding applicability in the cosmetic industry.