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Dissertationen zum Thema „Soil structure“
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1
Grieger, Gayle. „The effect of mineralogy and exchangeable magnesium on the dispersive behaviour of weakly sodic soils /“. Title page, table of contents and abstract only, 1999. http://web4.library.adelaide.edu.au/theses/09PH/09phg8478.pdf.
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2
Corneo, Paola Elisa. „Understanding soil microbial community dynamics in vineyard soils: soil structure, climate and plant effects“. Doctoral thesis, country:CH, 2013. http://hdl.handle.net/10449/23970.
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This thesis aimed at characterising the structure of the bacterial and fungal community living in vineyard soils, identifying and describing the parameters that explain the distribution of the
microbial communities in this environment.
Vineyards represent an economical relevant agro-ecosystem, where vines, long-lived woody-perennial plants, are normally cultivated at different altitudes. The maintenance of the soil quality is at the base of a productive agriculture and thus the investigation of its biological
component, its structure and all the processes that take place into the soil are of importance. Microorganisms represent one of the main biological components of the soil and they are involved in numerous bio-geochemical processes, such as nutrient cycling and degradation of the soil organic matter (SOM). The understanding of the effect of abiotic and biotic factors on the
soil microbial communities is crucial for the maintenance of this agro-ecosystem.
Considering that viticulture is widespread in North Italy we selected the Trentino region as study area at the basis of our investigations. A first on field study was carried out on soils collected in nine vineyards located along three altitudinal transects. The sites were selected on the basis of the same soil origin, texture and pH, and similar weather conditions. Our aim was to understand the effect of altitude considered as a climatic and physicochemical gradient on the soil bacterial and fungal community, comparing the soil microbial structure at different altitudes (200, 450, 700 m a.s.l.) and in different seasons. Along these altitudinal gradients, soil temperature is decreasing while soil moisture is increasing, thus offering an experimental design to investigate the effect of these climatic parameters. To further exploit the effect of soil temperature, we then carried out one year microcosm experiment. Temperature is one of the main factors affecting soil microbial communities and the recent worries about climate change stimulated the interest in a better understanding of its effect. Our aim was to assess the effect of temperature alone, isolating its effect from all the other parameters present in the field. In particular we investigated the effect of soil seasonal temperature fluctuations and the effect of a moderate soil warming of 2 °C above normal seasonal temperatures. Furthermore we assessed the effect of stable temperatures without fluctuations (3 and 20°C). To fully characterise the vineyard environment we conducted a third experiment to understand the effect of weeds and of soil type on the bacterial and fungal community structure, to reflect on their role in this environment. Weeds are widespread plants in the vineyards and are usually controlled because they compete for nutrients with vines. Through a greenhouse experiment where we used a combination of three different weeds (Taraxacum officinalis, Trifolium repens and Poa trivialis) and four different soils collected in vineyard, we aimed at characterising the bacterial and fungal communities of the bulk and rhizosphere soil and of the roots. The genetic structure of the soil bacterial and fungal communities in the three different experiments was assessed by automated ribosomal intergenic spacer analysis (ARISA), a fingerprinting technique based on the analysis of the length heterogeneity of the bacterial and fungal internal transcribed spacer (ITS) fragment. Multivariate analyses were carried out to
visualise and determine the effect of the different parameters investigated on the soil microbial community ordination. We found that altitude, behaving as a physicochemical gradient separates the soil microbial community living at 200 and 700 m a.s.l. Different parameters correlating with altitude explained the distribution of bacteria and fungi in the altitudinal transects. Qualitatively the different
vineyards were characterised by a stable core microbiome, a number of ribotypes stable in time and space. Among the climatic parameters, while soil moisture was correlating with altitude and helped explaining the distribution of the microbial communities, the soil temperature did not play any role. Seasonally the soil microbial communities were stable and the differences among the soil microbial communities living at the lower and higher sites were related to the physicochemical parameters and not to the temperature effect. Investigating the effect of temperature in microcosm experiment, isolating its effect from all the other parameters, we determined the presence of a direct effect of temperature, soil type dependent. The soil bacterial
community was fluctuating under the effect of temperature fluctuations, while the fungal community was mainly stable. Soil warming did not have any effect on the microbial community as observed on field in the altitudinal gradient, where temperature was not the factor explaining the differences between the microbial community at 200 and 700 m a.s.l. Vineyards, as other
temperate environments, are quite stable to subtle changes in soil temperatures in the range forecasted by the climate change events. Even if we did not find a direct effect of temperature on the soil microbial communities, temperature could indirectly affect the soil microorganisms, acting on plant cover, nutrients availability, soil moisture and plant exudation. The soil structure was the main determinant of the microbial community associated to the bulk
soil also in presence of plants. Characterising the microbial community associated to the weeds, we found that the different compartments (roots, rhizosphere and bulk soil) were colonised by
qualitatively and quantitative different microbial structure, in particular on the roots. Differences in the microbial community associated to the rhizosphere and to the bulk soil were plant type dependent. The structure of the microbial community associated to the roots was mainly
determined by the plant species, while the soil type was the main determinant of the microbial community associated to the bulk soil. Weeds are not expected to particularly affect the bacterial community associated to the bulk soil in vineyards, while they could play a role shaping the soil fungal community
3
Brandsma, Richard Theodorus. „Soil conditioner effects on soil erosion, soil structure and crop performance“. Thesis, University of Wolverhampton, 1997. http://hdl.handle.net/2436/99094.
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4
Li, Xu. „Dual-porosity structure and bimodal hydraulic property functions for unsaturated coarse granular soils /“. View abstract or full-text, 2009. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202009%20LI.
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5
Gandomzadeh, Ali. „Dynamic soil-structure interaction : effect of nonlinear soil behavior“. Phd thesis, Université Paris-Est, 2011. http://tel.archives-ouvertes.fr/tel-00648179.
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The interaction of the soil with the structure has been largely explored the assumption of material and geometrical linearity of the soil. Nevertheless, for moderate or strong seismic events, the maximum shear strain can easily reach the elastic limit of the soil behavior. Considering soil-structure interaction, the nonlinear effects may change the soil stiffness at the base of the structure and therefore energy dissipation into the soil. Consequently, ignoring the nonlinear characteristics of the dynamic soil-structure interaction (DSSI) this phenomenon could lead toerroneous predictions of structural response. The goal of this work is to implement a fully nonlinear constitutive model for soils into anumerical code in order to investigate the effect of soil nonlinearity on dynamic soil structureinteraction. Moreover, different issues are taken into account such as the effect of confining stress on the shear modulus of the soil, initial static condition, contact elements in the soil-structure interface, etc. During this work, a simple absorbing layer method based on a Rayleigh / Caughey damping formulation, which is often already available in existing. Finite Element softwares, is also presented. The stability conditions of the wave propagation problems are studied and it is shown that the linear and nonlinear behavior are very different when dealing with numerical dispersion. It is shown that the 10 points per wavelength rule, recommended in the literature for the elastic media is not sufficient for the nonlinear case. The implemented model is first numerically verified by comparing the results with other known numerical codes. Afterward, a parametric study is carried out for different types of structures and various soil profiles to characterize nonlinear effects. Different features of the DSSI are compared to the linear case : modification of the amplitude and frequency content of the waves propagated into the soil, fundamental frequency, energy dissipation in the soil and the response of the soil-structure system. Through these parametric studies we show that depending on the soil properties, frequency content of the soil response could change significantly due to the soil nonlinearity. The peaks of the transfer function between free field and outcropping responsesshift to lower frequencies and amplification happens at this frequency range. Amplificationreduction for the high frequencies and even deamplication may happen for high level inputmotions. These changes influence the structural response.We show that depending on the combination of the fundamental frequency of the structureand the the natural frequency of the soil, the effect of soil-structure interaction could be significant or negligible. However, the effect of structure weight and rocking of the superstructurecould change the results. Finally, the basin of Nice is used as an example of wave propagation ona heterogeneous nonlinear media and dynamic soil-structure interaction. The basin response isstrongly dependent on the combination of soil nonlinearity, topographic effects and impedancecontrast between soil layers. For the selected structures and soil profiles of this work, the performed numerical simulations show that the shift of the fundamental frequency is not a goodindex to discriminate linear from nonlinear soil behavior
6
Chen, Chien-chang. „Shear induced evolution of structure in water-deposited sand specimens“. Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/22724.
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7
Rouaiguia, Ammar. „Strength of soil-structure interfaces“. Thesis, Loughborough University, 1990. https://dspace.lboro.ac.uk/2134/26883.
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This research work deals with the development of the shearbox apparatus by introducing a micro-computer to automatically collect all the results, and to apply normal and shear stresses. A continuous statement of time, channel number, and transducer input and output is produced for each test, the sequences of applied rates of displacement and normal stresses for which were programmed.
8
Miller, Kendall Mar 1958. „INTERPRETIVE SCHEME FOR MODELING THE SPATIAL VARIATION OF SOIL PROPERTIES IN 3-D (AUTOCORRELATION, STOCHASTIC, PROBABILITY)“. Thesis, The University of Arizona, 1986. http://hdl.handle.net/10150/276981.
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9
Sribalaskandarajah, Kandiah. „A computational framework for dynamic soil-structure interaction analysis /“. Thesis, Connect to this title online; UW restricted, 1996. http://hdl.handle.net/1773/10180.
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10
Nelson, Paul Netelenbos. „Organic matter in sodic soils : its nature, decomposition and influence on clay dispersion“. Title page, contents and abstract only, 1997. http://web4.library.adelaide.edu.au/theses/09PH/09phn4281.pdf.
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Bibliography: leaves 147-170. Aims to determine the influence of sodicity on the nature and decomposition of organic matter; and the influence of organic matter and its components on the structural stability of sodic soils.
11
Gusli, Sikstus. „Effect of methods of wetting and rainfall characteristics on crusting and hardsetting of a red-brown earth“. Title page, abstract and table of contents only, 1995. http://web4.library.adelaide.edu.au/theses/09PH/09phg982.pdf.
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Includes bibliographical references. The beneficial effects of tillage are often negated in Australian soils by poor aggregate structural stability. If irrigation or rain falls on exposed freshly tilled soil, crusting or harsetting often develops on drying. Rainfall intensity, kinetic energy, rate of wetting, antecedent water content and soil management history have been implicated in aggregate breakdown.
12
White, Thomas Leslie Carleton University Dissertation Geology. „Cryogenic alteration of a frost susceptible soil“. Ottawa, 1992.
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13
Duval, Jean. „Assessing porosity characteristics as indicators of compaction in a clay soil“. Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=59275.
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Persistent soil compaction by heavy-axle-load vehicles is a growing concern for the long-term productivity of clay soils. For optimum soil management, however, we must be able to evaluate adequately soil structural damages. This study compares different methods of assessing soil structure as affected by compaction and subsoiling treatments in a clay soil under corn production.The tests used were: total porosity as calculated from densimeter readings and from soil cores; structural porosity; water desorption characteristics; and soil profile examination. These tests were performed in three layers of 20 cm and evaluation was based on their practicality and their ability to differentiate between treatments and to correlate with corn yield.
The results confirm that total porosity is a poor indicator of compaction in the subsoil. In soil profile assessments, ped descriptions were preferable to examination of pores. Water content and saturation deficit at $-$4.0 and $-$100 kPa were the best indicators of treatments and plant response.
14
Juyal, Archana. „Effect of soil structure on temporal and spatial dynamics of bacteria“. Thesis, Abertay University, 2015. https://rke.abertay.ac.uk/en/studentTheses/2c7e4706-3fd5-4a1f-af84-67134a2664ed.
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Soil is a complex heterogeneous system comprising of highly variable and dynamic micro-habitats that have significant impacts on the growth and activity of resident microbiota. A question addressed in this research is how soil structure affects the temporal dynamics and spatial distribution of bacteria. Using repacked microcosms, the effect of bulk-density, aggregate sizes and water content on growth and distribution of introduced Pseudomonas fluorescens and Bacillus subtilis bacteria was determined. Soil bulk-density and aggregate sizes were altered to manipulate the characteristics of the pore volume where bacteria reside and through which distribution of solutes and nutrients is controlled. X-ray CT was used to characterise the pore geometry of repacked soil microcosms. Soil porosity, connectivity and soil-pore interface area declined with increasing bulk-density. In samples that differ in pore geometry, its effect on growth and extent of spread of introduced bacteria was investigated. The growth rate of bacteria reduced with increasing bulk-density, consistent with a significant difference in pore geometry. To measure the ability of bacteria to spread thorough soil, placement experiments were developed. Bacteria were capable of spreading several cm’s through soil. The extent of spread of bacteria was faster and further in soil with larger and better connected pore volumes. To study the spatial distribution in detail, a methodology was developed where a combination of X-ray microtopography, to characterize the soil structure, and fluorescence microscopy, to visualize and quantify bacteria in soil sections was used. The influence of pore characteristics on distribution of bacteria was analysed at macro- and microscales. Soil porosity, connectivity and soil-pore interface influenced bacterial distribution only at the macroscale. The method developed was applied to investigate the effect of soil pore characteristics on the extent of spread of bacteria introduced locally towards a C source in soil. Soil-pore interface influenced spread of bacteria and colonization, therefore higher bacterial densities were found in soil with higher pore volumes. Therefore the results in this showed that pore geometry affects the growth and spread of bacteria in soil. The method developed showed showed how thin sectioning technique can be combined with 3D X-ray CT to visualize bacterial colonization of a 3D pore volume. This novel combination of methods is a significant step towards a full mechanistic understanding of microbial dynamics in structured soils.
15
Pitilakis, Dimitris. „Soil-structure interaction modeling using equivalent linear soil behavior in the substructure method“. Châtenay-Malabry, Ecole centrale de Paris, 2006. http://www.theses.fr/2006ECAP1067.
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Une procédure numérique, ainsi qu’un code numérique (MISS3D-EqL), est développés pour prendre en compte le comportement nonlinéaire du sol dans l'interaction sol-structure. Le comportement linéaire équivalent est supposé pour le sol, alors que la réponse de la structure et ses effets sur le sol sont correctement pris en considération avec la méthode de sous-structuration dynamique. La procédure proposée est validée par d'autres logiciels numériques et moyens expérimentaux, comme des essais de tables vibrante et centrifugeuse. Les effets du comportement linéaire équivalent du sol sur la réponse du système sol-structure sont clairement démontrés par des analyses de cas représentatives. Une analyse des systèmes typiques de sol-structure est exécutée pour indiquer le ramollissement supplémentaire du système et l’augmentation de la dissipation d'énergie, comparé au cas linéaire. Considération particulière est donnée à l'évaluation des fonctions dynamiques d'impédance de la fondation. Les coefficients dynamiques de la rigidité et de l'amortissement radiatif sont estimés pour des fondations typiques posées sur des profils typiques de sol avec un comportement linéaire équivalent. Les effets du comportement nonlinéaire du sol sont montrés comparés au cas linéaire élastique. Le coefficient dynamique de rigidité se diminue avec l'augmentation de l'amplitude de l'accélération, avec la vitesse décroissante de cisaillement du sol et avec le module décroissant de cisaillement du sol, alors qu'il dépend de la contenue fréquentiel du séisme. Le coefficient de d'amortissement radiatif n’est pas affecté par le comportement nonlinéaire du sol, pour la plupart des applications pratiquesA numerical procedure, coded into a numerical code (MISS3D-EqL), is developed to accommodate for the effects of the nonlinear soil behavior on the soil-structure interaction (SSI) using an equivalent linear approach. Equivalent linear behavior is assumed for the soil, while the response of the structure to the ground shaking and its effects on the soil are properly taken into account using the substructure method. The proposed procedure is validated against other numerical software and experimental means, such as shaking table and centrifuge tests. The effects of the equivalent linear soil behavior on the soil-structure system response are clearly demonstrated by analyses of representative case studies. A recursive analysis of typical soil profiles and infrastructures is performed to reveal the further softening of the system and the increased energy dissipation, compared to the linear case, due to the equivalent linear soil behavior. Special emphasis is given to the estimation of the foundation dynamic impedance functions. Dynamic stiffness and radiation dashpot coefficients are estimated for typical footings resting on typical soil profiles with equivalent linear behavior. The effects of the nonlinear soil behavior on the dynamic coefficient are shown compared to the linear elastic case. The dynamic stiffness coefficient decreases with increasing input acceleration amplitude, with decreasing soil shear wave velocity and with decreasing soil shear modulus, while it depends on the frequency content of the earthquake. The radiation dashpot coefficient is unaffected by the nonlinear soil behavior for most practical applications
16
García, García Julio Abraham. „Reduction of seismically induced structural vibrations considering soil-structure interaction“. [S.l. : s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=969246390.
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17
Rahgozar, Mohammad Ali Carleton University Dissertation Engineering Civil. „Semismic soil-structure interaction analysis of structural base shear amplification“. Ottawa, 1993.
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18
Nieto, ferro Alex. „Nonlinear Dynamic Soil-Structure Interaction in Earthquake Engineering“. Thesis, Châtenay-Malabry, Ecole centrale de Paris, 2013. http://www.theses.fr/2013ECAP0006/document.
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Ce travail détaille une approche de calcul pour la résolution de problèmes dynamiques qui combinent des discrétisations en temps et dans le domaine de Laplace reposant sur une technique de sous-structuration. En particulier, la méthode développée cherche à remplir le besoin industriel de réaliser des calculs dynamiques tridimensionnels pour le risque sismique en prenant en compte des effets non-linéaires d'interaction sol-structure (ISS). Deux sous-domaines sont considérés dans ce problème. D'une part, le domaine de sol linéaire et non-borné qui est modélisé par une impédance de bord discrétisée dans le domaine de Laplace au moyen d'une méthode d'éléments de frontière ; et, de l'autre part, la superstructure qui fait référence pas seulement à la structure et sa fondation mais aussi, éventuellement, à une partie du sol présentant un comportement non-linéaire. Ce dernier sous-domaine est formulé dans le domaine temporel et discrétisé avec la méthode des éléments finis (FE). Dans ce cadre, les forces liées à l'ISS s'écrivent sous la forme d'une intégrale de convolution en temps dont le noyau est la transformée de Laplace inverse de la matrice d'impédance de sol. Pour pouvoir évaluer cette convolution dans le domaine temporel à partir d'une impédance de sol définie dans le domaine de Laplace, une approche basée sur des Quadratures de Convolution (QC) est présentée : la méthode hybride Laplace-Temps (L-T). La stabilité numérique de son couplage avec un schéma d'intégration de type Newmark est ensuite étudiée sur plusieurs modèles d'ISS en dynamique linéaire et non-linéaire. Finalement, la méthode L-T est testée sur un modèle numérique plus complexe, proche d'une application sismique de caractère industriel, et des résultats satisfaisants sont obtenus par rapport aux solutions de référenceThe present work addresses a computational methodology to solve dynamic problems coupling time and Laplace domain discretizations within a domain decomposition approach. In particular, the proposed methodology aims at meeting the industrial need of performing more accurate seismic risk assessments by accounting for three-dimensional dynamic soil-structure interaction (DSSI) in nonlinear analysis. Two subdomains are considered in this problem. On the one hand, the linear and unbounded domain of soil which is modelled by an impedance operator computed in the Laplace domain using a Boundary Element (BE) method; and, on the other hand, the superstructure which refers not only to the structure and its foundations but also to a region of soil that possibly exhibits nonlinear behaviour. The latter subdomain is formulated in the time domain and discretized using a Finite Element (FE) method. In this framework, the DSSI forces are expressed as a time convolution integral whose kernel is the inverse Laplace transform of the soil impedance matrix. In order to evaluate this convolution in the time domain by means of the soil impedance matrix (available in the Laplace domain), a Convolution Quadrature-based approach called the Hybrid Laplace-Time domain Approach (HLTA), is thus introduced. Its numerical stability when coupled to Newmark time integration schemes is subsequently investigated through several numerical examples of DSSI applications in linear and nonlinear analyses. The HLTA is finally tested on a more complex numerical model, closer to that of an industrial seismic application, and good results are obtained when compared to the reference solutions
19
Dinel, H. (Henri) 1950. „The influence of soil organic matter components on the aggregation and structural stability of a lacustrine silty clay /“. Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=74306.
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Under intensive farming, soil structure degradation and soil erosion are primarily associated with losses of organic matter. Restoration of soil structure may depend on the amount and nature of the organic amendment added. The effect of the addition of humic and fibric materials, and beeswax, a naturally occurring source of long-chain aliphatics comparable to those present in humic materials, on microbial activity and the structural properties of a waterlogged silty clay low in organic carbon was investigated. The incorporation of the fibric material increased the microbial activity in proportion to the amount of material added, whereas the humic and beeswax materials had the opposite effect. All organic materials added increased the cohesion of aggregates due to non water-dispersible cements. The fibric material was predominantly composed of polysaccharides and large quantities were required to produce a positive effect. The humic material was mainly lipids and the effect was associated with the time of incubation rather than the amount of material added. Principal-component analysis showed that the humic material was more effective at stabilizing soil aggregates than the fibric material, although the fibric material had a greater effect on the resistance of aggregates to slaking forces. Further testing with beeswax showed that the clay-associated lipids increased by 3.5-4.0 times the resistance of soil aggregates to the slaking forces, whereas the effect of hydrophobic "free" lipids was transient and accessory by coating and embedding soil aggregates.
20
Barzegar, Abdolrahman. „Structural stability and mechanical strength of salt-affected soils“. Title page, contents and abstract only, 1995. http://web4.library.adelaide.edu.au/theses/09PH/09phb296.pdf.
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Copies of author's previously published articles in pocket inside back cover. Bibliography: leaves 147-160. This thesis outlines the factors affecting soil strength and structural stability and their interrelationship in salt-affected soils. The objectives of this study are to investigate the influence of clay particles on soil densification and mellowing, the mellowing of compacted soils and soil aggregates as influenced by solution composition, the disaggregation of soils subjected to different sodicities and salinities and its relationship to soil strength and dispersible clay and the effect of organic matter and clay type on aggregation of salt-affected soils.
21
Löfkvist, John. „Modifying soil structure using plant roots /“. Uppsala : Dept. of Soil Sciences, Swedish University of Agricultural Sciences, 2005. http://epsilon.slu.se/200560.pdf.
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22
Warnakulasuriya, Hapuhennedige Surangith. „Soil structure interaction of buried pipes“. Thesis, University of East London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286607.
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23
Lees, Andrew Steven. „Soil/structure interaction of temporary roadways“. Thesis, University of Southampton, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324808.
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24
Fairfield, Charles Alexander. „Soil-structure interaction in arch bridges“. Thesis, University of Edinburgh, 1994. http://hdl.handle.net/1842/13809.
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European Community directives now insist upon the imposition of 11.5t axle weights for the assessment of highway bridges and structures. This need for heavier loads arises from the Community wide harmonisation of transport policy. Its successful implementation requires the urgent assessment of our bridge stock of some 75000 masonry arches. The analysis of arch bridges has long lacked an accurate method of assessing the loads transmitted to the arch ring by the surrounding soil. This thesis proposes pressure distributions suitable for use in the analysis of arch bridges. It examines, by way of instrumented small scale and in-situ tests, the soil-structure interaction effects arising from the backfill material. Observations of zones of soil displacement around a loaded arch are made in order to better describe the interactive effects. A finite element analysis of the instrumented tests was done and a parametric study was used to assess the effects of various material properties upon the system's behaviour. The inclusion of the interactive effects observed, and modelled, intends to lead to cost savings in the arch bridge assessment programme by reducing the conservatism inherent in the most common assessment methods. Design curves incorporating soil-structure interaction effects are presented where significant capacity increases can be seen compared with analyses ignoring the effects.
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Taherzadeh, Reza. „Seismic soil-pile group-structure interaction“. Châtenay-Malabry, Ecole centrale de Paris, 2008. http://www.theses.fr/2008ECAP1096.
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Si la prise en compte de l'interaction sol-structure peut être abordée de façon relativement simple dans la plupart des fondations superficielles, il n'en est pas de même pour des groupes de pieux. Les principales difficultés rencontrées sont liées à la complexité et à la taille du modèle numérique nécessaire à l’analyse détaillée. Cette thèse porte sur la modélisation de l’interaction dynamique sol-structure dans le cas particulier des fondations comportant un grand nombre de pieux. Ce travail consiste à faire des modélisations avancées en utilisant un couplage entre le logiciel MISS3D d’éléments de frontière pour des milieux élastiques stratifiés et la toolbox matlab d’éléments finis SDT pour la modélisation des fondations et des structures. Après avoir validé la modélisation à partir de solutions de la littérature, les principaux paramètres gouvernant l’impédance de ces fondations ont été mis en évidence. Les modèles simplifiés de ces impédances ont ensuite été développés dans le cas de pieux flottants ou de pieux encastrés dans un bedrock. Des paramètres de ces modèles simplifiés ont été déterminés par des analyses statistiques fondées sur une base étendue de modèles numériques couvrant une large gamme de situations pratiques. Ces modèles approchés ont été validés sur des cas particuliers, puis différents spectres de réponse modifiés par la prise en compte de l’interaction sol-structure ont été proposésDespite the significant progress in simple engineering design of surface footing with considering the soil-structure interaction (SSI), there is still a need of the same procedure for the pile group foundation. The main approach to solve this strongly coupled problem is the use of full numerical models, taking into account the soil and the piles with equal rigor. This is however a computationally very demanding approach, in particular for large numbers of piles. The originality of this thesis is using an advanced numerical method with coupling the existing software MISS3D based on boundary element (BE), green's function for the stratified infinite visco-elastic soil and the matlab toolbox SDT based on finite element (FE) method to modeling the foundation and the superstructure. After the validation of this numerical approach with the other numerical results published in the literature, the leading parameters affecting the impedance and the kinematic interaction have been identified. Simple formulations have then been derived for the dynamic stiffness matrices of pile groups foundation subjected to horizontal and rocking dynamic loads for both floating piles in homogeneous half-space and end-bearing piles. These formulations were found using a large data base of impedance matrix computed by numerical FE-BE model. These simple approaches have been validated in a practical case. A modified spectral response is then proposed with considering the soil-structure interaction effect
26
Ritter, Stefan. „Experiments in tunnel-soil-structure interaction“. Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/273891.
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Urbanisation will require significant expansion of underground infrastructure, which results in unavoidable ground displacements that affect the built environment. Predicting the interaction between a tunnel, the soil and existing structures remains an engineering challenge due to the highly non-linear behaviour of both the soil and the building. This thesis investigates the interaction between a surface structure and tunnelling-induced ground displacements. Specifically, novel three-dimensionally printed building models with brittle material behaviour, similar to masonry, were developed and tested in a geotechnical centrifuge. This enabled replication of building models with representative global stiffness values and realistic building features including strip footings, intermediate walls, a rough soil-structure interface, building layouts and façade openings. By varying building characteristics, the impact of structural features on both the soil and building response to tunnelling in dense sand was investigated. Results illustrate that the presence of surface structures considerably altered the tunnelling-induced soil response. The building-to-tunnel position notably influences the magnitude of soil displacements and causes localised phenomena such as embedment of building corners. An increase of the façade opening area and building length reduces the alteration of the theoretical greenfield settlements, in particular the trough width. Moreover, the impact of varying the building layout is discussed in detail. For several building-tunnel scenarios, building distortions are quantified and the crucial role of building features is demonstrated. Structures spanning the greenfield inflection point experienced more deformation than identical structures positioned in either sagging or hogging, and partitioning a structure either side of the greenfield inflection point is shown to lead to unconservative damage assessments. Results also quantify the significant extent to which structural distortions increase as façade openings and building length increases. Observed building damage and cracking patterns confirm the reported trends. The experimental results are used to evaluate the performance of available methods to assess the behaviour of buildings to tunnelling. Predictions ignoring soil-structure interaction are usually overly conservative, while approaches based on the relative stiffness of a structure and the soil result in inconsistent predictions, though some methods performed better than others. Practical improvements to consider structural details when assessing this tunnel-soil-structure system are finally proposed.
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Khalili, Tehrani Payman. „Analysis and modeling of soil-structure interaction in bridge support structures“. Diss., Restricted to subscribing institutions, 2009. http://proquest.umi.com/pqdweb?did=1925776151&sid=5&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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28
Feeney, Deborah Siobhan. „The influence of fungi upon soil structure and soil water relations“. Thesis, Abertay University, 2004. https://rke.abertay.ac.uk/en/studentTheses/2a92d2fc-b3c5-456f-8b9a-e406bd78ee84.
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The investigation of soil structural stability and soil water processes was assessed through the application of laboratory investigations and a field based analysis. The impact of an arbuscular mycorrhizal (AM) fungal exudate glomalin (a glycoprotein), proposed to be hydrophobic was assessed for a correlation with low levels of soil hydrophobicity through measures of subcritical water repellency. Initially no correlation was reported but a further temporal investigation that involved a soil inoculum detected a significant positive effect; the results indicated that a certain concentration of protein is required before an influence upon soil hydrophobicity is detected. The temporal investigation detected significant re-aggregation of previously disturbed soil; this was linked to both increases in fungal biomass and enmeshment by plant roots. Soil in the direct vicinity of plant roots showed the most significant increases in aggregated structures, indicating that plant root enmeshment was one of the predominant factors in soil aggregation. Soil water repellency was directly correlated with measures of macroaggregates (aggregates >2000 pm), indicating that increased hydrophobicity is a mechanism involved in aggregate stabilisation. Field scale sampling and analysis indicated that fertilizer applications had varied effects upon fungal populations, dependent on the particular land management applied to the soil. Undisturbed grassland where fungal biomass was likely to be the predominant microorganism present showed significant effects of fertilizer regime upon fungal biomass, with effects likely to be related to plant-fungi interactions through changes in AM fungal biomass. The influence of fertilizer regime on arable sites was less pronounced which indicated a significant influence of disturbance reducing fungal biomass and reducing the direct and indirect effects associated with fertilizer additions. The investigation of soil pore spatial distribution is essential for understanding soil processes as water flow, gas and nutrient exchanges will occur within pore space, as will many biological processes. The investigation of inter-aggregate pore space was completed upon soil aggregates < 2 mm that had been exposed to previous experimental perturbations, where increased aggregate stability, water repellency and fungal biomass were reported. A resolution of «4 pm was achieved and changes in percentage porosity and spatial pore distributions were detected as a result of direct and indirect effects of plant roots. Greatest increases in heterogeneity of pore space were reported in soil from close proximity to roots, with a reduction in this phenomenon at an increasing distance from the root zone. The mechanism proposed for these changes was localised drying from roots. The results presented provide greater understanding of controlling factors associated with soil water and stability mechanisms, along with demonstrating biologically and physically induced changes in micro and meso-scale structures as a result of different treatments. The work provides scope for further investigation of particular biological and physical factors associated with soil structural mechanisms.
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Alyagshi, Eilouch Mohamed Nazih. „A mixed method for transient analysis of structures including soil-structure interaction /“. The Ohio State University, 1986. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487264603218809.
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Romanel, Celso. „A global-local approach for dynamic soil-structure interaction analysis of deeply embedded structures in a layered medium“. Diss., The University of Arizona, 1989. http://hdl.handle.net/10150/184762.
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The most popular method for dynamic soil-structure interaction analysis is the finite element method. The versatility in problems involving different materials and complex geometries is its main advantage, yet the FEM can not simulate unbounded domains completely. Several schemes have been proposed to overcome this shortcoming, such as the use of either imperfect or perfect transmitting boundaries, infinite elements and hybrid techniques. However, most of them were derived on the assumption that the soil mass can be represented as a homogeneous material despite the fact that stratified soil deposits are a common occurrence in nature. A hybrid method is proposed in this research for soil-structure interaction analysis in the frequency domain involving a multilayered linear elastic half-space. The near field region (structure and a portion of soil surrounding it) is modeled by finite elements while the far field formulation is obtained through the classical wave propagation theory based on the assumption that the actual scattered wave fields can be represented by a set of line sources. Traction reciprocity between the two regions is satisfied exactly, while the displacement continuity across the common interface is enforced in a least-squares sense. The two-dimensional system is excited by harmonic body waves (P and SV) propagating with oblique incidence. The structure can be considered either on the surface or deeply embedded in the multilayered half-space. Analytic solutions for the far field domain is obtained through the combined response of four simple problems that take into account the overall effects of the incident, reflected and scattered wave fields. The delta matrix technique is employed in order to eliminate the loss of precision problem associated with the Thomson-Haskell matrix method in its original form. Special numerical schemes are used to transform the solution from the κ- into the ω-plane due to the presence of poles on the path of integration. The few numerical examples studied in this research validate the proposed hybrid technique, but the relatively high computational cost required for evaluation of the Green's functions is still a serious drawback. Some suggestions are made to minimize the problem as well as to extend this technique to cases involving material attenuation and forced vibrations.
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Balendra, Surendran. „Numerical modeling of dynamic soil-pile-structure interaction“. Online access for everyone, 2005. http://www.dissertations.wsu.edu/Thesis/Fall2005/s%5Fbalendra%5F120705.pdf.
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32
Wick, Abbey Foster. „Soil aggregate and organic matter dynamics in reclaimed mineland soils“. Laramie, Wyo. : University of Wyoming, 2007. http://proquest.umi.com/pqdweb?did=1400961671&sid=1&Fmt=2&clientId=18949&RQT=309&VName=PQD.
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Yogendrakumar, Muthucumarasamy. „Dynamic soil-structure interaction : theory and verification“. Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/29222.
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A nonlinear effective stress method of analysis for determining the static and dynamic response of 2-D embankments and soil-structure interaction systems is presented. The method of analysis is incorporated in the computer program TARA-3. The constitutive model in TARA-3 is expressed as a sum of a shear stress model and a normal stress model. The behavior in shear is assumed to be nonlinear and hysteretic, exhibiting Masing behavior under unloading and reloading. The response of the soil to uniform all round pressure is assumed to nonlinearly elastic and dependent on the mean normal effective stresses.
The porewater pressures required in the dynamic effective stress method of analysis are obtained by the Martin-Finn-Seed porewater pressure generation model modified to include the effect of initial static shear. During dynamic analysis, the effective stress regime and consequently the soil properties are modified for the effect of seismically induced porewater pressures.
A very attractive feature of TARA-3 is that all the parameters required for an analysis may be obtained from conventional geotechnical engineering tests either in-situ or in laboratory.
A novel feature of the program is that the dynamic analysis can be conducted starting from the static stress-strain condition which leads to accumulating permanent deformations in the direction of the smallest residual resistance to deformation. The program can also start the dynamic analysis from a zero stress-zero strain condition as is done conventionally in engineering practice.
The program includes an energy transmitting base and lateral energy transmitting boundaries to simulate the radiation of energy which occurs in the field.
The program predicts accelerations, porewater pressures, instantaneous dynamic deformations, permanent deformations due to the hysteretic stress-strain response, deformations due to gravity acting on the softening soil and deformations due to consolidation as the seismic porewater pressures dissipate.
The capability of TARA-3 to model the response of soil structures and soil-structure interaction systems during earthquakes has been validated using data from simulated earthquake tests on a variety of centrifuged models conducted on the large geotechnical centrifuge at Cambridge University in the United Kingdom. The data base includes acceleration time histories, porewater pressure time histories and deformations at many locations within the models. The program was able to successfully simulate acceleration and porewater pressure time histories and residual deformations in the models.
The validation program suggests that TARA-3 is an efficient and reliable program for the nonlinear effective stress analysis of many important problems in geotechnical engineering for which 2-D plane strain representation is adequate.Applied Science, Faculty of
Civil Engineering, Department of
Graduate
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Sun, Hepn Wing. „Ground deformation mechanisms for soil-structure interaction“. Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303931.
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David, Thevaneyan Krishta David. „Integral bridges: modelling the soil-structure interaction“. Thesis, University of Leeds, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.581881.
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Integral abutment bridges, also known as integral bridges, have become one of the most common types of joint-less bridge construction, certainly over the last three decades. Their principal advantages are derived from the elimination of expansion joints and bearings, making them a very cost-effective system in terms of construction, maintenance, and longevity. The elimination of joints from bridges creates a significant soil-structure interaction behind the abutment and the piles generating an interesting problem since the response of the different elements of the integral bridge are interdependent. This research project used numerical analyses to investigate the complex interactions that exist between the structural components of the stub-type integral abutment bridge and the backfill soil. Where possible, these results were validated with existing field data. A literature review was conducted to gain an insight into the behaviour of integral abutment bridges, particularly the soil-structure interaction of integral bridges. To gain a better understanding of the behaviour of integral abutment bridges and their interaction with the backfill soil adjacent to the abutment and the piles, particularly due to thermally induced movement/loads, a 2D finite element analysis was performed on a typical integral abutment bridge using OASYS GSA and OASYS SAFE. The results from this research are believed to help answer two of the most debated issues with respect to stub-type integral abutment bridge-soil interaction analyses. Firstly, it is clear, and now possible, that a reliably accurate soil profile is used in the analysis/design. The Mohr-Coulomb soil model was found to realistically represent the soil behaviour. Secondly, the research may suggest that cyclic movements / loads may not significantly influence the overall behaviour of integral abutment bridges. In addition, it was found that the development of earth pressure behind the integral abutment is significantly affected by the backfill soil properties and is a function of the integral abutment displacement. Limiting values for the abutment displacement, which induces maximum backfill pressure, have been suggested. The soil separation phenomenon (gapping) was also found to significantly affect the backfill/foundation soil-load relationship behaviour. Implications· of this research for practising engineers and recommendations for future research work are also included.
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Dewsbury, Jonathan J. „Numerical modelling of soil-pile-structure interaction“. Thesis, University of Southampton, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.582152.
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Soil-pile-structure interaction analysis is the simultaneous consideration of the structural frame, pile foundations, and the soil forming the founding material. Failure to consider soil-pile-structure interaction in design will lead to a poor prediction of load distribution within the structure. A poor prediction of load distribution will cause the structure to deform under loads that have not been calculated for. This may result in the structure cracking or the overstressing of columns. If the actual load distribution significantly differs from that designed for, the factor of safety on structural elements may be substantially decreased. Despite the importance, there are currently no studies quantifying the effect of soil-pile-structure interaction for simple office structures. As a result the effects of soil-pile-structure interaction are often deemed unimportant, and ignored in the design of simple structures. Numerical methods are often relied upon to consider soil-pile-structure interaction for complex structures, such as tall towers. However in their current form they are limited because the meshes required for analysis, especially when in three dimensions, are difficult to verify, and take a long time to set up and run. Therefore this thesis proposes a meshing method within the framework of the finite element method that allows large, complex, and non-symmetrical pile foundation layouts to be meshed in a manner that is quick, can be easily checked, and significantly reduces the analysis run time. Application of the meshing method to an office structure (recently designed for the 2012 Olympic Games) has allowed the effects of soil-pile-structure interaction to be quantified. The subsequent normalisation of the results provides a method for assessing when it is necessary to consider soil- pile-structure interaction in future design. Comparison between the monitored performance of 'The Landmark' (a 330m tower founded on a piled raft) and numerical predictions have demonstrated the importance of correct ground stiffness selection for achieving accurate predictions of piled raft settlement, and load distribution. The role of single pile load tests and in situ testing for ground stiffness selection for piled raft design has also been assessed
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Zolghadr, Zadeh Jahromi Hamid. „Partitioned analysis of nonlinear soil-structure interaction“. Thesis, Imperial College London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.512070.
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Taunton, Paul R. „Centrifuge modelling of soil/masonry structure interaction“. Thesis, Cardiff University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244112.
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Callaway, Phillip Arthur. „Soil-structure interaction in masonry arch bridges“. Thesis, University of Sheffield, 2007. http://etheses.whiterose.ac.uk/3036/.
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White, William Patrick. „Soil moisture, fire, and tree community structure“. Wright State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=wright1301936875.
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Pang, Sydney Carleton University Dissertation Engineering Civil. „Soil-structure interaction in discontinuous shear zones“. Ottawa, 1989.
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Materechera, Simeon Albert. „Generation of soil structure by plant roots“. Adelaide Thesis (Ph.D.) -- University of Adelaide, Department of Soil Science, 1993. http://hdl.handle.net/2440/21654.
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Title page, contents and abstract only. The complete thesis in print form is available from the University Library.Thesis (Ph.D.)--University of Adelaide, Dept. of Soil Science, Waite Agricultural Research Institute, 1994
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Elshesheny, Ahmed. „Dynamic soil-structure interaction of reinforced concrete buried structures under the effect of dynamic loads using soil reinforcement new technologies. Soil-structure interaction of buried rigid and flexible pipes under geogrid-reinforced soil subjected to cyclic loads“. Thesis, University of Bradford, 2019. http://hdl.handle.net/10454/18312.
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Recent developments in constructions have heightened the need for protecting existing buried infrastructure. New roads and buildings may be constructed over already existing buried infrastructures e.g. buried utility pipes, leading to excessive loads threatening their stability and longevity. Additionally applied loads over water mains led to catastrophic damage, which result in severe damage to the infrastructure surrounding these mains. Therefore, providing protection to these existing buried infrastructure against increased loads due to new constructions is important and necessary.
In this research, a solution was proposed and assessed, where the protection concept would be achieved through the inclusion process of geogrid-reinforcing layers in the soil cover above the buried infrastructure. The controlling parameters for the inclusion of geogrid-reinforcing layers was assessed experimentally and numerically. Twenty-three laboratory tests were conducted on buried flexible and rigid pipes under unreinforced and geogrid-reinforced sand beds. All the investigated systems were subjected to incrementally increasing cyclic loading, where the contribution of varying the burial depth of the pipe and the number of the geogrid-reinforcing layers on the overall behaviour of the systems was investigated. To further investigate the contribution of the controlling parameters in the pipe-soil systems performance, thirty-five numerical models were performed using Abaqus software. The contribution of increasing the amplitude of the applied cyclic loading, the number of the geogrid-reinforcing layers, the burial depth of the pipe and the unit-weight of the backfill soil was investigated numerically.
The inclusion of the geogrid-reinforcing layers in the investigated pipe-soil systems had a significant influence on decreasing the transferred pressure to the crown of the pipe, generated strains along its crown, invert and spring-line, and its deformation, where reinforcing-layers sustained tensile strains. Concerning rigid pipes, the inclusion of the reinforcing-layers controlled the rebound that occurred in their invert deformation. With respect to the numerical investigation, increasing the number of the reinforcing-layers, the burial depth of the pipe and the unit-weight of the backfill soil had positive effect in decreasing the generated deformations, stresses and strains in the system, until reaching an optimum value for each parameter. Increasing the amplitude of the applied loading profile resulted in remarkable increase in the deformations, stresses and strains generated in the system. Moreover, the location of the maximum tensile strain generated in the soil was varied, as well as the reinforcing-layer, which suffered the maximum tensile strain.Government of Egypt
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Aldaikh, Hesham S. H. „Discrete models for the study of dynamic structure-soil-structure interaction“. Thesis, University of Bristol, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.633205.
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The problem of Dynamic Structure-Soil-Structure Interaction (SSSI) refers to the mutual interaction of adjacent buildings in built-up high density areas through the underlying soil under earthquake excitation. Due to the complexity of the problem, past studies have mainly considered the use of intricate mathematical formulations or the computationally demanding numerical Finite Element and Boundary Element methods. In the present study, linear elastic two-dimensional formulations are proposed using simple discrete lumped parameter models for structures and soil for groups of two and three adjacent buildings systems. The formulation includes a rotational spring as a key buildings interaction mechanism. Inverse power laws are proposed for this rotational interaction and for soil/foundation springs stiffnesses which turn out to be functions of spacing between adjacent buildings. These relationships are obtained by equating energies from the low order discrete and high order Finite Element models.
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Zinn, Yuri Lopes. „Textural, mineralogical and structural controls on soil organic carbon retention in the Brazilian Cerrados“. Columbus, Ohio : Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1131381122.
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Soyoz, Serdar. „Effects Of Soil Structure Interaction And Base Isolated Systems On Seismic Performance Of Foundation Soils“. Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605119/index.pdf.
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In this thesis primarily structural induced liquefaction potential was aimed to be
analyzed. Also the effect of base isolation systems both on structural performance and
liquefaction potential was studied. FLAC software was chosen for the analyses so that
structure and soil could be modeled together. By these means the soil structure
interaction effects were also examined. Four different structures and three different sites
were analyzed under two different input motions. All the structures were also analyzed
as base isolated. It was mainly found that depending on the structural type and for a
certain depth the liquefaction potential could be higher under the structure than the one
in the free field. Also it was concluded that base isolation systems were very effective
for decreasing the story drifts, shear forces in the structure and liquefaction potential in
the soil. It was also found that the interaction took place between structure, soil and
input motions.
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Park, Jin Young. „A critical assessment of moist tamping and its effect on the initial and evolving structure of dilatant triaxial specimens“. Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/23949.
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O'Brien, Eugene M. „Soil morphology and potentiometric surface relationship in an East Central Indiana toposequence“. Virtual Press, 2000. http://liblink.bsu.edu/uhtbin/catkey/1164849.
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The objective of this study was to determine the correlation between potentiometric surface and the depth to selected soil morphological indicators of wetness for the Glynwood (Aquic Hapludalf), Blount (Aeric Epiaqulaf), and Pewamo (Typic Argiaguoll) soils in Delaware County, Indiana. Four years of potentiometric surface measurements were averaged and compared to detailed soil descriptions performed by the Natural Resources Conservation Service. Significant correlations exist between the morphological indicators and the potentiometric surface for the Glynwood (moderately well drained) 2-m depth piezometers and 2-m depth slotted pipes, the Blount (somewhat poorly drained) top of the C horizon and 2-m depth piezometers, and the Pewamo (poorly drained) top of the B horizon piezometers. The relationships among the horizons in which potentiometric surface correlated to indicator depth may be a function of the increased persistence and shallowness of the potentiometric surface in mid-April.Department of Natural Resources and Environmental Management
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Reeve, Jennifer Rose. „Soil quality, microbial community structure, and organic nitrogen uptake in organic and conventional farming systems“. Online access for everyone, 2007. http://www.dissertations.wsu.edu/Dissertations/Summer2007/j_reeve_071207.pdf.
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Solomon-Wisdom, Grace Oyiza. „The effect of in situ spatial heterogeneity of lead in soil on plant uptake“. Thesis, University of Sussex, 2015. http://sro.sussex.ac.uk/id/eprint/54284/.
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The understanding of the spatial distribution of lead (Pb) in soil is important in the assessment of potential risks and development of remediation strategies for Pb contaminated land. In situ heterogeneity of Pb was measured at two heavily contaminated sites in the United Kingdom using the Portable X-ray Fluorescence Spectrometer (P-XRF) over a range of spatial scales (0.02 to 50 m). The pattern of the distribution of Pb was very variable, and when expressed as heterogeneity factor (HF), it ranged from 1.2 to 3.2 (highly heterogeneous). The effect of such Pb heterogeneity on plant uptake was investigated in greenhouse pot trials. Two earlier pot trials, which assessed the effect of Pb in a fixed concentration (1000 mg/kg) and in a range of concentration (100 to 10000 mg/kg) found a significant effect of the Pb added treatments, when compared to a control treatment (0 mg/kg Pb added). Biomass and uptake varied by 20 to 100% within and between 16 species/varieties. Results enhanced the selection of two species (Brassica napus and Brassica juncea) for further pot trials. A third pot experiment with Brassica napus and Brassica juncea in simplistic binary model of heterogeneity found 20 to 60% lower uptake in the binary treatment, than homogeneous the treatment. Biomass was higher by 10 to 50% in Brassica juncea and 20 to 40% lower for B. napus in the bianary treatment, when compared to the homogeneous and control treatments. The effect of a more realistic in situ heterogeneity on plant uptake was investigated in a further pot trial, which simulated low (LH), medium) (MH) and high (HH) heterogeneity treatments, compared to a homogeneous (HO) treatment. It detected a significant (P < 0.05) impact of heterogeneity on biomass and uptake between treatments and species. Four to five fold lower biomass were recorded in HH treatment, when compared to the HO treatment. Shoot and root uptake in (mg/kg) concentration increased with increasing heterogeneity with peak uptake (twice as high as HO treatment) in LH for B. napus and in HH and MH treatments for B. juncea respectively. Shoot and root Pb masses in (μg) were maximum in HO and MH treatments respectively with 50 to 70% lower Pb mass in the HH treatment. Results showed that response to heterogeneity is species specific. A sub-experiment explored the behaviour of plant roots in HH treatment and found 20 to 80% variation in root biomass between concentric patches with same nominal soil Pb concentrations. This provided insights into varied responses of these species to realistic Pb heterogeneity. The research demonstrated that the presence and extent of in situ heterogeneity of Pb in soil plays an important role in Pb uptake by plants. It also showed that the homogeneous and simplistic binary model of heterogeneity do not give reliable estimates of plant growth and Pb uptake in realistic field conditions. This work has implications for improving the efficiency of phytoremediation of Pb contaminated land, phytomining, reliability of risk assessment and models of human exposure to Pb.