Dans les analyses d'interaction sol-structure (ISS), la pratique commune en génie civil est de considérer un mouvement uniforme du champ libre à tous les points situés à la surface du sol. Néanmoins, cette considération n'est pas tout à fait réaliste parce que les signaux sismiques sont spatialement différents grâce à l'effet de passage d'ondes, à l'effet de site et aussi aux dispersions et réflexions des ondes qui propagent dans des milieux hétérogènes aléatoires ("incohérence pure"). Ainsi, pour répondre aux problèmes de sécurité des bâtiments et équipements, il est important de faire une analyse d'interaction sol-structure dans la manière plus réaliste. Cela peut être acquis par prendre en compte la variabilité spatiale du champ sismique dans les études d'ISS. Un grand nombre d'études dans la littérature montrent que la prise en compte de la variabilité spatiale du champ sismique dans les études d'ISS peut avoir des effets importants sur la réponse de structures. L'incohérence spatiale du champ sismique due aux dispersions et réflexions des ondes (incohérence pure) peut généralement être modélisée pour ce genre d'études dans le cadre probabiliste par une fonction de cohérence. Le but principal des études réalisées dans cette thèse de doctorat est de construire une description stochastique de la variabilité spatiale du champ sismique par un modèle de cohérence. Ce modèle devrait avoir une relation avec les propriétés physiques et statistiques de milieux considérés. En s'appuyant sur les analyses théoriques de la propagation des ondes sismiques dans des milieux hétérogènes aléatoires, les analyses des données expérimentales obtenues par des enregistrements sur des sites sismiques, ainsi que sur les modélisations numériques de propagation des ondes sismiques dans des milieux hétérogènes aléatoires, un modèle de cohérence est validé dans le cadre des études de cette thèse de doctorat pour représenter la variabilité spatiale du champ sismique dans les études d'interaction sol-structure. L'influence de la variabilité spatiale du champ sismique sur la réponse de structure est également analysée. / In seismic soil-structure interaction studies (SSI), the common practice in Civil Engineering is to consider a uniform movement of free field at any point on the ground surface. However, that assumption is not completely realistic since the seismic ground motions can vary spatially due to wave passage effects, dispersions and reflections of wave propagating in the random heterogeneous media "pure incoherence" and site effects. Therefore, in order to increase the security of buildings and equipment, it is important to do an analysis of seismic soil-structure interactions in the most realistic way. This can be achieved by taking into account the spatial variability of seismic ground motions. Several studies in the literature show that taking into account the spatial variability of seismic ground motions in SSI analyses can have remarkable effects on the structural responses. The spatial incoherence of seismic ground motions due to dispersions and reflections of wave "pure incoherence" can generally be modelled in such analysis by a "coherency function" in frequency domain. The principal goal of this Ph.D thesis is to construct a stochastic description of spatial variability of seismic ground motions by means of coherency functions. Accurately, it aims to propose a parametrical coherency model of spatial variability of seismic ground motions. This later should be related to some physical and statistical properties of the soil at the application sites so that it can be applied in any types of sites. Based on theoretical considerations on coherency of seismic wave propagation in random heterogeneous media, on experimental data analyses, and on numerical modelling of seismic wave propagation in random heterogeneous media, a coherency model is validated and proposed for the analyses of soil-structure interactions. The influence of spatial variability of seismic ground motions on the structural responses are also pointed out by using the validated coherency model.

The Ethiopian Highlands have been studied extensively, hosting a large amount of research for development projects in agriculture and forestry over several decades. The encounters in these projects were also encounters of different ways of knowing that were negotiated by the actors meeting in the space provided by the projects. This research explores these encounters and the social worlds they are embedded in, drawing on actor-oriented approaches as well as theories of narratives and framing. Ways of knowing and citizen epistemologies are taken as a lens to understand the role of identities in knowledge production and use. The two case studies were agroforestry research projects in the Ethiopian Highlands. The research followed a range of qualitative and ethnographic research methods. Different types of farmers and scientists meet in the case studies. I recognise that they all have individual agency, nevertheless I use the terms ‘scientist' and ‘farmer' in this thesis. I use the terms to describe certain groups of actors who all draw on different ways of knowing, and different value systems, when interacting with each other and their environment. The results indicate that the importance of social worlds at different scales and the contexts of research projects tend to be underestimated. In spite of good intentions scientific methodologies, terminologies and narratives tend to dominate. Scientists in the case studies acknowledged the existence of farmers' ‘indigenous' knowledge, but they determined the value of knowledge by its scientific applicability and the replicability of experiments. Research systems force the scientists into a certain modus operandi with limited possibilities to experiment and to respond to the complexities and diversities of people's social worlds. Farmers in the case studies preferred observation from their parents, observing from others or the environment as a way of learning and gaining knowledge. Depending on their personalities and their life histories they also relied on alternative ways of knowing rooted in spirituality, emotions and memories. Powerful influences on ways of knowing resulted from the way languages and authority had been used. These often led to the exclusion of marginalised community members from access to knowledge and technologies. Unfortunately, common narratives prevailed in the case studies, and alternative ways of knowing were often marginalised. By acknowledging different ways of knowing and the importance of different social worlds and different ways of doing research, both scientists and farmers could benefit and develop more sustainable pathways for agricultural and forestry land use.

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / A conversÃo de florestas em pastagens pode ter um impacto sobre as propriedades e funÃÃes do solo, especialmente em condiÃÃes irrigadas. Partindo da hipÃtese de que a conversÃo de Ãrea natural em Ãrea sob pastagem irrigada altera algumas propriedades do solo, objetivou-se avaliar propriedades quÃmicas, fÃsicas e microbiolÃgicas indicadoras da qualidade do solo, em Ãrea sob pastagem, comparando-a com sua condiÃÃo natural. Para tanto, foram analisados atributos quÃmicos (compartimentos de carbono e nitrogÃnio no solo e lipÃdeos); microbiolÃgicos (carbono e nitrogÃnio da biomassa microbiana, respirometria, populaÃÃes de fungos micorrÃzicos arbusculares e glomalina) e fÃsicos (estabilidade de agregados, curva de retenÃÃo da Ãgua no solo, Ãndice S, e IHO), em diferentes profundidades e classes de agregados, visando estabelecer ligaÃÃes que possibilitassem identificar as alteraÃÃes sofridas no solo. Observou-se de modo geral, que o manejo empregado està conseguindo manter a sustentabilidade do sistema. No entanto, deve-se ressaltar que caracterÃsticas intrÃnsecas, como a textura do solo e densidade radicular das gramÃneas, foram determinantes no comportamento de atributos selecionados, como por exemplo, estabilidade de agregados. Foram observadas alteraÃÃes nos atributos estudados, principalmente na distribuiÃÃo dos mesmos no perfil, promovendo o aumento dos compartimentos de carbono e nitrogÃnio do solo, alÃm do teor de lipÃdeos. Os atributos microbiolÃgicos nÃo sofreram alteraÃÃes significativas, indicando que a pastagem irrigada nÃo influencia negativamente tais atributos. Quanto aos atributos fÃsicos, como CRA, IHO e Ãndice S, houve interferÃncia de caracterÃsticas intrÃnsecas, como por exemplo, a textura na determinaÃÃo da qualidade do solo. / The conversion of forests into pastures may have an impact on the properties and functions of the soil, especially in irrigated conditions. Assuming that the conversion of natural area within the area under irrigated pasture alters some soil properties, aimed to evaluate the chemical, physical and microbiological indicators of soil quality in pasture area, comparing it to its natural condition. To this end, analized the chemical (carbon pools and nitrogen in the soil and lipids); microbiological (carbon and microbial biomass nitrogen, respirometry, populations of arbuscular mycorrhizal fungi and glomalin) and physical attributes (aggregate stability, water retention curve soil, S index and IHO) at different depths and aggregate classes, to establish connections that would enable to identify the changes that occurred in the soil. It was observed generally that the management employee is able to maintain the sustainability of the system. However, it should be noted that intrinsic characteristics such as soil texture and density of the grass root, were decisive in the behavior of selected attributes, such as aggregate stability. There were changes in the attributes studied, mainly in their distribution in the profile, promoting the increase of carbon pools and nitrogen from the soil, beyond the level of lipids. The microbiological attributes did not change significantly, indicating that the irrigated pasture does not adversely affect these attributes. The physical attributes, like CRA IHO and S index, the interference of characteristics, for example, in determining the texture of the soil.

Neste trabalho é realizado um estudo da sensibilidade de estruturas de paredes de concreto moldadas no local quanto à deslocabilidade dos seus apoios, a fim de determinar sua influência na redistribuição dos esforços nos elementos estruturais. Para tanto, utiliza-se um modelo de referência, que discretiza a superestrutura através de elementos finitos de casca e avalia a interação solo-estrutura através de métodos iterativos, que consideram a rigidez da edificação, a heterogeneidade do solo e o efeito de grupo das fundações. Para quantificar e avaliar os efeitos da interação solo-estrutura realiza-se um estudo paramétrico, em que a influência do tipo de fundação (profunda ou superficial), número de pavimentos (cinco, dez e quinze) e a forma da edificação (quadrada e alongada) são avaliadas. Um modelo simplificado de análise estrutural, em que a interação solo-estrutura é considerada e as paredes de concreto são discretizadas por elementos de barra, acima do segundo pavimento, foi proposto e avaliado, por meio de comparações com os resultados do seu respectivo modelo de referência. Por fim, foram discutidas as implicações e a importância da consideração do efeito da deslocabilidade dos apoios e feitas recomendações sobre a modelagem simplificada. Observa-se: alívio dos apoios com maiores recalques, tendência de uniformização dos recalques, maior influência nas paredes inferiores e suficiência dos cincos primeiros pavimentos na definição de rigidez solo/estrutura. / In this paper, a sensitivity study was carried out of concrete reinforced walls molded on site regarding the displaceability of their supports, in order to determine their influence on the redistribution of internal forces in structural elements. In order to do this, a reference model was used, which discretizes the superstructure using shell finite elements and evaluates the soil-structure interaction by iterative methods that consider the rigidity of the building, the soil heterogeneity and the group effect of foundations. To quantify and assess the effects of soil-structure interaction, a parametric study was carried out in which the influence of the type of foundation (deep or shallow), number of floors (five, ten and fifteen) and the shape of the building (square, elongated) are evaluated. A simplified model of the structural analysis, in which the soil-structure interaction is considered and the concrete walls are discretized by bar elements, above the second floor, was proposed and evaluated by comparing its respective reference model with the results. Finally, the implications and the importance of considering the effect of displaceability of the supports were discussed and recommendations were made about the simplified modeling. The analysis denotes: relief of reactions on supports with larger settlements, tendency of settlements standardization, larger influence on the lower walls and that the first five floors are enough to define the relative soil/structure stiffness.

Fundações do tipo radier estaqueado são aquelas formadas pelos elementos estruturais de placa e estacas (elementos de barras) e o solo . Ao contrário de outras tipos de fundações, onde a carga da superestrutura é transferida ao solo pelo radier ou pelas estacas apenas, no radier estaqueado a contribuição das estacas, bem como a do radier são consideradas. As estacas transferem as cargas da superestrutura ao solo e, assim, permitem a redução dos recalques de uma forma muito econômica. O objetivo do presente trabalho é a análise da interação solo-estrutura através do acoplamento MEC-MEF. O solo é considerado um semi-espaço homogêneo, elástico e linear governado pela equação de Navier e modelado pelo Método dos Elementos de Contorno (MEC), admitindo a solução fundamental de Mindlin. As estacas são modeladas pelo Método dos Elementos Finitos (MEF) e cada elemento possui quatro nós. Além disso, as estacas podem receber forças horizontais, verticais e momentos. A tensão de cisalhamento ao longo da estaca é aproximada por um polinômio do segundo grau e as forças na direção horizontal são aproximadas por um polinômio do quarto grau. O elemento de fundação que faz a ligação do pilar com a estaca é representado por uma placa de grande rigidez, que apresenta o comportamento de um bloco. A interação entre o radier estaqueado e o solo é feita através da reação resultante da interação estaca-solo, nos nós com estaca. A interface radier-solo é dividida em elementos triangulares e para a reação do solo considera-se a variação linear ao longo de cada elemento. A superestrutura é modelada pelo MEF. Vários exemplos de interação solo-estrutura são estudados nesta tese, e mostram que as soluções obtidas a partir do programa computacional desenvolvido no presente trabalho denominado SSI estão de acordo com outros autores. / Piled raft foundations are structures consisting of piles, the raft and the soil. Unlike classical foundation design where the building load is either transferred by the raft or the piles alone, in a piled raft foundation the contribution of the piles as well as the raft is taken into account. The piles transfer a part of the building loads into the soil and thereby allow the reduction of settlement in a very economic way. The objective of the present work is the analysis of soil-structure interaction using BEM-FEM coupling. The soil, assumed to be an elastic linear homogeneous half space is governed by Navier\'s equation and it is modeled by the Boundary Elements Method (BEM) using Mindlin\'s fundamental solution. The piles are modeled by the Finite Element Method (FEM) with four nodes each. In addition, the piles can received horizontal and vertical forces and bending moments. The shear traction along the pile is approximated by a second-degree polynomial and the tractions in the horizontal direction are approximated by a fourth degree polynomial. The cap of the pile group is assumed to be rigid. The interaction between the raft and soil is made through the subgrade reaction. The soil-cap interface is divided into triangular elements and the subgrade reaction is assumed to vary linearly across each element. The building\'s structure is modeled by FEM. Several soil structure interaction examples are studied in this thesis, and they show that the solutions obtained from program SSI are in good agreement with others authors.

Neste trabalho apresenta-se um modelo numérico para a análise de problemas tridimensionais envolvendo a interação mecânica estaca-solo, acoplando-se o Método dos Elementos de Contorno (MEC) ao Método dos Elementos Finitos (MEF). O solo é modelado com o MEC utilizando-se as soluções fundamentais de Mindlin, assumindo um meio semi-infinito, homogêneo, isotrópico e elástico-linear. As estacas, modeladas com o MEF, consistem em um elemento único, com quatro nós e 14 parâmetros nodais (três deslocamentos em cada nó e mais duas rotações no topo da estaca). Cada uma das estacas é levada em consideração no MEC como uma linha de carga. Considera-se o escorregamento das estacas em relação ao maciço, empregando modelos de aderência para a definição da evolução das tensões tangenciais ao longo do comprimento das estacas. São empregados, como funções de forma, polinômios do quarto grau para os deslocamentos horizontais, cúbicos para os deslocamentos verticais e tensões horizontais ao longo do fuste e quadráticos para as tensões verticais do fuste e escorregamento. A reação da ponta da estaca é calculada assumindo tensão constante na base. / This work presents a method for tri-dimensional pile-soil interaction problems, by coupling the Boundary Element Method (BEM) to the Finite Element Method (FEM). The soil is modeled with BEM, using the Mindlins fundamental solutions, supposing a semi-infinite, homogeneous, isotropic, elastic and linear space. Piles are modeled with FEM and are represented by one element with four nodes and 14 nodal parameters (three displacements in each node and two rotations at the top node). Each pile is represented in BEM as a line load. The pile slip is considered using adherence models to evaluate the evolution of shaft tractions. There are employed fourth grade polynomial shape functions for horizontal displacements, cubic polynomial functions for vertical displacements and horizontal tractions along shaft and quadratic polynomial functions for vertical tractions and slip. Tip reaction is calculated supposing constant traction at the base.

A thermo-elastic-plastic model for unsaturated soils has been presented based on the effective stress principle considering the thermo-mechanical and suction coupling effects. The thermo-elastic-plastic constitutive equations for stress-strain relations of the solid skeleton and changes in fluid content and entropy for unsaturated soils have been established. A plasticity model is derived from energy considerations. The model derived covers both associative and non-associative flow behaviours and the modified Cam-Clay is considered as a special case. All model coefficients are identified in terms of measurable parameters. To verify the proposed model, an experimental program has been developed. A series of controlled laboratory tests were carried out on a compacted silt sample using a triaxial equipment modified for testing unsaturated soils at elevated temperatures. Imageprocessing technique was used for measuring the volume change of the samples subjected to mechanical, thermal and hydric loading. It is shown that the effective critical state parameters M, ???? and ???? are independent of temperature and matric suction. Nevertheless, the shape of loading collapse (LC) curve was affected by temperature and suction. Furthermore, the temperature change affected the soil water characteristic curve and an increase in temperature caused a decrease in the air entry suction. The simulations from the proposed model are compared with the experimental results. The model calibration was performed to extract the model parameters from the experimental results. Good agreement between the results predicted using the proposed model and the experimental results was obtained in all cases.

The phenomenon called soil aggregate coalescence occurs at contact-points between aggregates and causes soil strength to increase to values that can inhibit plant root exploration and thus potential yield. During natural wetting and drying, soil aggregates appear to ‘weld’ together with little or no increase in dry bulk density. The precise reasons for this phenomenon are not understood, but it has been found to occur even in soils comprised entirely of water stable aggregates. Soil aggregate coalescence has not been widely observed and reported in soil science and yet may pose a significant risk for crops preventing them from achieving their genetic and environmental yield potentials. This project used soil penetrometer resistance and an indirect tensile-strength test to measure the early stages of aggregate coalescence and to evaluate their effects on the early growth of tomato plants. The early stages of aggregate coalescence were thought to be affected by a number of factors including: the matric suction of water during application and subsequent drainage, the overburden pressure on moist soil in the root zone, the initial size of soil aggregates prior to wetting, and the degree of sodicity of the soil aggregates. Seven mainexperiments were conducted to evaluate these factors. The matric suction during wetting of a seedbed affects the degree of aggregate slaking that occurs, and the strength of the wetted aggregates. The matric suction during draining affects the magnitude of ‘effective stresses’ that operate to retain soil structural integrity as the soil drains and dries out. An experiment was conducted to evaluate the influence of matric suction (within a range of suctions experienced in the field) on aggregate coalescence using soils of two different textures. Sieved aggregates (0.5 to 2 mm diameter) from a coarse-textured and two fine-textured (swelling) soils were packed into cylindrical rings (4.77 cm i.d., 5 cm high) and subjected to different suctions on wetting (near-saturation, and 1 kPa), and on draining (10 kPa on sintered-glass funnels, and 100 kPa on ceramic pressure plates). After one-week of drainage, penetrometer resistance was measured as a function of depth to approximately 45 mm (penetrometer had a recessedshaft, cone diameter = 2 mm, advanced at a rate of 0.3 mm/min). Tensile strength of other core-samples was measured after air-drying using an indirect “Brazilian” crushing test. For the coarse-textured soil, penetrometer resistance was significantly greater for samples wet to near-saturation, despite there being no significant increase in dry bulk density; this was not the case for the finer-textured soils, and it was difficult to distinguish the effects of variable bulk density upon drying from those of the imposed wetting treatments. In both coarse- and fine-textured soils, the tensile strength was significantly greater for samples wet to near-saturation. Thus wetting- and draining-suctions were both found to influence the degree of soil aggregate coalescence as measured by penetrometer resistance and tensile strength. Aggregate coalescence in irrigated crops is known to develop as the growing season progresses. It was therefore thought to be linked to the repeated occurrence of matric suctions that enhance the phenomenon during cycles of wetting and draining. An experiment was conducted to determine the extent of aggregate coalescence in a coarsetextured and two fine-textured (swelling clay) soils during 8 successive cycles of wetting and draining. Sieved aggregates (0.5 to 2 mm diameter) from each soil were packed into cylindrical rings (4.77 cm i.d., 5 cm high) and wetted to near saturation for 24 h. They were then drained on ceramic pressure plates to a suction of 100 kPa for one week, after which penetrometer resistance and tensile strength were measured as described above. The degree of expression of aggregate coalescence depended on soil type. For the coarse-textured soil, repeated wetting and draining significantly increased bulk density, penetrometer resistance and tensile strength. For the fine-textured soil, penetrometer resistance and bulk density did not vary significantly with repeated wetting and draining; on the contrary, there was evidence in these swelling clay soils to suggest bulk density and penetrometer resistance decreased. However, there was a progressive increase in tensile strength as cycles of wetting and draining progressed. The expansive nature of the fine-textured soil appears to have masked the development of aggregate coalescence as measured by penetrometer resistance, but its expression was very clear in measurements of tensile strength despite the reduction in bulk density with successive wetting and draining. Field observations have indicated that aggregate coalescence is first expressed at the bottom of the seedbed and that it develops progressively upward to the soil surface during the growing season. This suggests that overburden pressures may enhance the onset of the phenomenon by increasing the degree of inter-aggregate contact. Soils containing large quantities of particulate organic matter were known to resist the onset of aggregate coalescence to some extent. An experiment was conducted to evaluate the effects of soil organic matter and overburden pressures, by placing brass cylinders of various weights (equivalent to static load pressures of 0, 0.49, 1.47 and 2.47 kPa) on the top of dry soil aggregates (0.5 – 2 mm diameter) having widely different soil organic carbon contents placed in steel rings 5 cm high and 5 cm i.d. With the weights in place, the aggregates were wetted to near-saturation for 24 h and then drained on ceramic pressure plates to a suction of 100 kPa for one week. Bulk density, penetrometer resistance and tensile strength were measured when the samples were removed from the pressure plates and they all increased significantly with increasing overburden pressure in the soil with low organic matter content, but not in the soil with high organic matter content. The amount of tillage used to prepare seedbeds influences the size distribution of soil aggregates produced – that is, more tillage produces finer seedbeds. The size distribution of soil aggregates affects the number of inter-aggregate contact points and this was thought to influence the degree of aggregate coalescence that develops in a seedbed. Previous work has shown that soil organic matter reduces aggregate coalescence and so an experiment was conducted to evaluate the effects of aggregate size and organic matter on the phenomenon. For soils with high and low organic matter contents, aggregate size fractions of < 0.5, 0.5 – 2, 2 – 4, and < 4 mm were packed into soil cores (as above) and wetted to near-saturation then drained to 100 kPa suction as described above. Penetrometer resistance and tensile strength were measured and found to increase directly with the amount of fine material present in the soil cores – being greater in the < 0.5 mm and < 4 mm fractions, and being less in the 0.5 – 2 mm and 2 – 4 mm fractions. In all cases, penetrometer resistance and tensile strength were lower in the samples containing more organic matter. The rate at which soil aggregates are wetted in a seedbed affects the degree of slaking and densification that occurs, and the extent to which aggregates are wetted influences the overall strength of a seedbed. Both wetting rate and the extent of wetting were believed to influence the onset of aggregate coalescence and were thought to be affected by soil organic matter and irrigation technique. An experiment was therefore designed to separate these effects so that improvements to management could be evaluated for their greatest efficacy – that is, to determine whether management should focus on improving irrigation technique or increasing soil organic matter content, or both. The rate of wetting was controlled by spraying (or not spraying) soil aggregates (0.5 – 2 mm diameter) with polyvinyl alcohol (PVA). Samples of coarse- and fine-textured soils were packed into steel rings (as above) and subjected to different application rates of water (1, 10 and 100 mm/h) using a dripper system controlled by a peristaltic pump. Samples were brought to either a near-saturated state or to a suction of 10 kPa for 24 h, and then drained on a pressure plate at a suction of 100 kPa for one week. Measurements of penetrometer resistance and tensile strength were then made as described above. As expected, penetrometer resistance was lower in samples treated with PVA before wetting (slower wetting rates) and in samples held at a greater suction (10 kPa) after initial wetting (greater inter-aggregate strength). The effects were more pronounced in the coarse-textured soil. In both coarse- and fine-textured soils, tensile strengths increased with increasing wetting rate (greatest for 100 mm/h) and extent of wetting (greater when held at near-saturated conditions). The rate of wetting was found to be somewhat more important for promoting aggregate coalescence than the extent of wetting. Because aggregate coalescence often occurs with little or no increase in bulk density, an explanation for the increase in penetrometer resistance and tensile strength is unlikely to be explained by a large increase in the number of inter-aggregate contacts. An increase in the strength of existing points of inter-aggregate contact was therefore considered in this work. For inter-aggregate bond strengths to increase, it was hypothesized that small increases in the amount of mechanically (or spontaneously) dispersed clay particles, and subsequent deposition at inter-aggregate contact points could increase aggregate coalescence as measured by penetrometer resistance and tensile strength. An experiment was devised to manipulate the amount of spontaneously dispersed clay in coarse- and fine-textured soils of high and low organic matter content. The degree of sodicity of each soil was manipulated by varying the exchangeable sodium percentage (ESP) of soil aggregates (0.5 – 2mm) above and below a nominal threshold value of 6. Dry aggregates were then packed into steel rings (as above) and subjected to wetting near saturation, then draining to a suction of 100 kPa for one week as described above. Measurements were then taken of penetrometer resistance and tensile strength, both of which were affected by ESP in different ways. In the coarse-textured soil, sodicity enhanced aggregate slaking and dispersion, which increased bulk density. While penetrometer resistance also increased, its effect on aggregate coalescence could not be separated from a simple effect of increased bulk density. Similarly, the effect of sodicity on aggregate coalescence in the fine-textured soil was confounded by the higher water contents produced by greater swelling, which produced lower-than-expected penetrometer resistance. Measurements of tensile strength were conducted on air-dry samples, and so the confounding effects of bulk density and water content were eliminated and it was found that tensile strength increased with sodicity in both coarse- and fine-textured soils. The presence of dispersed clay was therefore implicated in the development of aggregate coalescence in this work. Finally, a preliminary evaluation of how the early stages of aggregate coalescence might affect plant growth was attempted using tomatoes (Gross lisse) as a test plant. Seeds were planted in aggregates (0.5 – 4 mm) of a coarse- or fine-textured soil packed in steel rings. These were wetted at a rate of 1 mm/h to either near-saturation (for maximum coalescence) or to a suction of 10 kPa (for minimum coalescence) and held under these conditions for 24 h. All samples were then transferred to a ceramic pressure plate for drainage to 100 kPa suction for one week. Samples were then placed in a growth-cabinet held at 20C with controlled exposure to 14 h light/day. Germination of the seeds, plant height, and number and length of roots were observed. Germination of the seeds held at near-saturation in both coarse- and fine-textured soils was delayed by 24 h compared with seeds held at 10 kPa suction. Neither the number nor the length of tomato roots differed significantly between the different treatments and soils. In the coarse-textured soil, however, the total root length over a period of 14 days was somewhat greater in the uncoalesced samples than in the coalesced samples, but this difference was not statistically significant. These results suggest that aside from delaying germination, aggregate coalescence may not have a large effect on early growth of tomato plants. However, this is not to say that detrimental effects may not be manifest at later stages of plant growth, and this certainly needs to be evaluated, particularly because aggregate coalescence increase with repeated cycles of wetting and draining. In conclusion, the primary findings of the work undertaken in this thesis were: • Rapid wetting of soil aggregates to near-saturation enhanced the onset of soil aggregate coalescence as measured by (in some cases) penetrometer resistance at a soil water suction of 100 kPa, and (in most cases) tensile strength of soil cores in the air-dry state. The rate of wetting appeared to be more important in bringing on aggregate coalescence than how wet the soil eventually became during wetting. This means reducing the rate at which irrigation water is applied to soils may reduce the onset of aggregate coalescence more effectively than controlling the total amount of water applied – though both are important. The literature reports that aggregate coalescence occurs in the field over periods of up to several months, involving multiple wetting and draining cycles, but the work here demonstrated that this can occur over much shorter time periods depending on conditions imposed. • Aggregate coalescence occurred in coarse-textured soils regardless of whether the bulk density increased during wetting and draining. In finer-textured soils, the response to wetting conditions varied and was complicated by changes in bulk density and water content due to swelling. • Small overburden pressures enhanced the onset of aggregate coalescence, but these effects were diminished in the presence of high soil organic matter contents. • Finer aggregate size distributions (which are often produced in the field by excessive tillage during seedbed preparation) invariably led to greater aggregate coalescence than coarser aggregate size distributions. The effects of aggregate size were mitigated to some extent by higher contents of soil organic matter. • Sodicity enhanced aggregate coalescence as measured by tensile strength, but when penetrometer resistance was measured in the moist state, the effects were masked to some extent by higher water contents generated by swelling and dispersion. This work suggests that tensile strength (in the air dry state) may be a more effective measure of aggregate coalescence than penetrometer resistance. • Early plant response to aggregate coalescence was not large, but the response may become magnified during later stages of growth. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1297583 / Thesis (Ph.D.) -- School of Earth and Environmental Sciences, 2007

This dissertation presents the results of a research effort conducted to better understand the seismic performance and analysis of pile-supported wharves. Given the limited number of well-documented field case histories, the seismic performance of pile-supported wharves has been poorly quantified, and the analysis methods commonly employed in engineering practice have generally not been validated. Field case histories documenting the seismic performance of pile-supported wharves commonly contain only limited information, such as approximations of wharf and embankment deformations and peak ground surface accelerations. In order to supplement the field data, five centrifuge models were dynamically tested, with each model containing close to 100 instruments monitoring pile bending moments, excess pore pressures, displacements, and accelerations. The combined field and model database was used to develop seismic performance relationships between permanent lateral deformations, maximum and residual bending moments and peak ground surface displacements. Key issues such as the seismic performance of batter piles, the development of large moments at depth, and the need to account for permanent lateral deformations for high levels of shaking, even for very stable geometries, are discussed. The field data and model studies were also used to validate two geotechnical seismic performance analysis methods: 1) the limit-equilibrium based rigid, sliding block (Newmark) method, and 2) an advanced finite-difference effective stress based numerical model (FLAC). Favorable predictions were generally obtained for both methods, yet there was a large variability in the results predicted using the rigid, sliding block method. The numerical model predicted the permanent deformations, pore pressure generation, and accelerations fairly well, however, pile bending moments were poorly predicted. The results of this research clearly highlighted the need for analysis validation studies, and note the uncertainty and variability inherent in the seismic performance of complex structures. The lack of adequate validation may lead to an over-confidence and false sense of security in the results of the seismic analysis methods. This dissertation specifically addresses pile-supported wharves, yet the results presented herein are applicable to other pile-supported structures located near, or on, slopes adjacent to the waterfront, such as: bridge abutments, railroad trestles, and pile-supported buildings near open slopes. Performance and analysis issues common to all of these structures are addressed, such as: liquefiable soils, lateral pile response in horizontal and sloping soils, the lateral behavior of piles in rock fill, and global slope stability, as well as the general observed seismic behavior. / Graduation date: 2004

In many seismic design codes and provisions, such as Uniform Building Code and Turkish Seismic Code, prediction of fundamental period of shear-wall dominant buildings, constructed by tunnel form technique, to compute the anticipated seismic forces is achieved by empirical equations considering the height of the building and ratio of effective shear-wall area to first floor area as the primary predictor parameters. However, experimental and analytical studies have collectively indicated that these empirical formulas are incapable of predicting fundamental period of shear-wall dominant buildings, and consequently result in erroneous computation of design forces. To compensate for this deficiency, an effective yet simple formula has recently been developed by Balkaya and Kalkan (2004), and tested against the data from ambient surveys on existing shear-wall dominant buildings. In this study, previously developed predictive equation is modified to include the effects of soil-structure interaction on the fundamental period. For that purpose, 140 shear-wall dominant buildings having a variety of plans, heights and wall-configurations were re-analyzed for four different soil conditions classified according to NEHRP. The soil effects on the foundation were represented by the translational and rotational springs, and their rigidities were evaluated from foundation size and elastic uniform compressibility of soil. Based on the comprehensive study conducted, improved prediction of fundamental period is achieved. The error in predictions on average is about 15 percent, and lending further credibility to modified formula considering soil-structure interaction to be used in engineering practice.