<p> The effects of sampling on the strength and preconsolidation load of a normally consolidated natural silty clay have been studied by means of laboratory simulations of "perfect" samples, "ground" samples, "tube" samples and "bottom of failed borehole" samples. </p> / Thesis / Master of Engineering (MEngr)

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22764号 / 工博第4763号 / 新制||工||1745(附属図書館) / 京都大学大学院工学研究科都市環境工学専攻 / (主査)教授 米田 稔, 教授 橋本 訓, 准教授 福谷 哲 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

The purpose of this research was to investigate the physical weathering of rock along the Victoria Land Coast, Antarctica. It was designed to contribute to the Latitudinal Gradient Project, a joint initiative between the New Zealand, Italian and United States Antarctic Programmes. The Latitudinal Gradient Project aims to improve our understanding of the ecosystems of the Dry Valleys and ice-free areas of the Ross Sea Region and, by using latitude as a proxy measure, identify how they might be affected by future climate change. The approach taken for this research was to use information on rock (from one rock group) temperature and moisture conditions gathered from three field locations to inform laboratory simulations. The laboratory simulations would then be used to investigate the weathering of small rock blocks and aggregates. Two temperature cycles approximating those experienced during summer and spring/autumn were identified and simulations undertaken in a specially adapted freezer. Three levels of moisture were applied: no moisture, half saturation and full saturation. Results of the laboratory simulations indicated that although rocks responded in different ways to different processes, granular disintegration took place even in the absence of additional moisture and did not require crossings of the 0 OC isotherm, nor were high levels of moisture required for across zero temperature cycling to produce weathering effects. A model that related weathering to latitude was developed and changes in climate explored. It was found that the weathering effect of summer and spring/autumn cycles was different and depended on rock characteristics rather than latitude. Increasing the ratio of summer to spring/autumn temperature cycles by 10% indicated that weathering could decrease or remain the same depending on the particular rock. Changes in temperature were found to be more important than changes in moisture. A weathering index that related local climate and rock properties to weathering was also developed and this highlighted the difficulties of using laboratory results to predict field rates of weathering. There were some surprising results from the field, including the presence of much more moisture on the surface of the rock, primarily from blowing snow, than had been predicted for this dry environment. This occurred even in the presence of negative rock surface temperatures. In addition, winter rock surface temperatures can fluctuate up to 25 OC, getting as warm as -10 OC. Macro-climate and changes in air temperature in response to foehn and katabatic winds were the drivers for these fluctuations.

Titan's VUV photochemistry is studied by laboratory simulation and numerical modeling.In the laboratory simulations, a gas flow of N2/CH4 (90/10) was irradiated by a continuousVUV (60-350 nm) synchrotron beam in a new reactor, named APSIS (Atmospheric Photochemistry SImulated by Synchrotron). The production of C2-C4 hydrocarbons as well as several nitriles is detected by in situ mass spectrometry and ex situ GC-MS of a cryogenic experiment.Our modeling strategy includes the treatment of uncertain parameters. We propose separaterepresentations of the uncertain photolysis cross-sections and branching ratios. This enables to develop a wavelength-dependent model for the branching ratios.Owing to this separation, in the modeling of Titan's atmosphere, we observe specific altitudes where the uncertainty on the photolysis rate constants vanishes. We show that the Ly-α methane photolysis branching ratios of Wang et al. (2000) and the commonly used 100% CH3 hypothesis for out-of-Ly-α ones should be avoided in Titan's photochemical models. A new ion-neutral coupled model was developed for the APSIS experiments. By this model, ion chemistry and in particular dissociative recombination are found to be very important. We identifed three growth families, of which the most unsaturated one, promoted by C2H2, is dominant. This agrees well with the unsaturated production in Titan's upper atmosphere observed by the Cassini INMS, but not with the in situ MS in the APSIS and Imanaka and Smith (2010)'s experiments, whose saturated productions are substantially higher and likely to originate from the catalysis by metallic walls of the reactors.

The purpose of this research was to investigate the physical weathering of rock along the Victoria Land Coast, Antarctica. It was designed to contribute to the Latitudinal Gradient Project, a joint initiative between the New Zealand, Italian and United States Antarctic Programmes. The Latitudinal Gradient Project aims to improve our understanding of the ecosystems of the Dry Valleys and ice-free areas of the Ross Sea Region and, by using latitude as a proxy measure, identify how they might be affected by future climate change. The approach taken for this research was to use information on rock (from one rock group) temperature and moisture conditions gathered from three field locations to inform laboratory simulations. The laboratory simulations would then be used to investigate the weathering of small rock blocks and aggregates. Two temperature cycles approximating those experienced during summer and spring/autumn were identified and simulations undertaken in a specially adapted freezer. Three levels of moisture were applied: no moisture, half saturation and full saturation. Results of the laboratory simulations indicated that although rocks responded in different ways to different processes, granular disintegration took place even in the absence of additional moisture and did not require crossings of the 0 OC isotherm, nor were high levels of moisture required for across zero temperature cycling to produce weathering effects. A model that related weathering to latitude was developed and changes in climate explored. It was found that the weathering effect of summer and spring/autumn cycles was different and depended on rock characteristics rather than latitude. Increasing the ratio of summer to spring/autumn temperature cycles by 10% indicated that weathering could decrease or remain the same depending on the particular rock. Changes in temperature were found to be more important than changes in moisture. A weathering index that related local climate and rock properties to weathering was also developed and this highlighted the difficulties of using laboratory results to predict field rates of weathering. There were some surprising results from the field, including the presence of much more moisture on the surface of the rock, primarily from blowing snow, than had been predicted for this dry environment. This occurred even in the presence of negative rock surface temperatures. In addition, winter rock surface temperatures can fluctuate up to 25 OC, getting as warm as -10 OC. Macro-climate and changes in air temperature in response to foehn and katabatic winds were the drivers for these fluctuations.

La photochimie de Titan amorcée par rayonnements VUV est étudiée par la simulation en laboratoire et la modélisation numérique.Dans les simulations en laboratoire, nous avons irradié un _ux de gaz de N2/CH4 (90/10)par un faisceau synchrotron VUV continu (60-350 nm) dans un nouveau réacteur, nommé APSIS (Atmospheric Photochemistry SImulated by Synchrotron). La production d'hydrocarbures C2-C4 ainsi que de plusieurs nitriles est détectée par la spectrométrie de masse in situ et GC-MS ex situ d'un piège cryogénique. Notre stratégie de modélisation comprend le traitement des paramètres incertains. Nous proposons des représentations séparées des sections efficaces et des rapports de branchement incertains de photolyse. Cela permet de développer un modèle dépendant de la longueur d'onde pour les rapports de branchement. Grâce à cette séparation, dans la modélisation de l'atmosphère de Titan, nous observons lesaltitudes spécifiques où l'incertitude sur les constantes de vitesse de photolyse disparaît. Nous montrons que les rapports de branchement de la photolyse du méthane de Wang et al. (2000) et l'hypothèse 100% CH3 pour ceux hors Ly-α, couramment utilisés, doivent être évités dans les modèles photochimiques de Titan.Nous avons dévéloppé un modèle ion-neutre couplé pour les expériences APSIS. Par ce modèle, nous trouvons que la chimie des ions et, en particulier, la recombinaison dissociative sont très importants. Nous avons identifié trois familles de croissance, dont la plus insaturée, promue par C2H2, est prédominante. Ceci est en bon accord avec la production des espèces insaturées dans la haute atmosphère de Titan détectée par le Cassini INMS, mais pas avec les spectres de masse in situ dans les expériences APSIS et celles d'Imanaka and Smith (2010), dont les productions d'espèces saturées sont nettement plus élevées et probablement dues à catalyse par les parois métalliques des réacteurs. / Titan's VUV photochemistry is studied by laboratory simulation and numerical modeling.In the laboratory simulations, a gas flow of N2/CH4 (90/10) was irradiated by a continuousVUV (60-350 nm) synchrotron beam in a new reactor, named APSIS (Atmospheric Photochemistry SImulated by Synchrotron). The production of C2-C4 hydrocarbons as well as several nitriles is detected by in situ mass spectrometry and ex situ GC-MS of a cryogenic experiment.Our modeling strategy includes the treatment of uncertain parameters. We propose separaterepresentations of the uncertain photolysis cross-sections and branching ratios. This enables to develop a wavelength-dependent model for the branching ratios.Owing to this separation, in the modeling of Titan's atmosphere, we observe specific altitudes where the uncertainty on the photolysis rate constants vanishes. We show that the Ly-α methane photolysis branching ratios of Wang et al. (2000) and the commonly used 100% CH3 hypothesis for out-of-Ly-α ones should be avoided in Titan's photochemical models. A new ion-neutral coupled model was developed for the APSIS experiments. By this model, ion chemistry and in particular dissociative recombination are found to be very important. We identifed three growth families, of which the most unsaturated one, promoted by C2H2, is dominant. This agrees well with the unsaturated production in Titan's upper atmosphere observed by the Cassini INMS, but not with the in situ MS in the APSIS and Imanaka and Smith (2010)'s experiments, whose saturated productions are substantially higher and likely to originate from the catalysis by metallic walls of the reactors.