Waterborne carbon (C) forms an active and significant part of the global C cycle, which is important in theArctic where greater temperature increases and variability are anticipated relative to the rest of the globe withpotential implications for the C cycle. Understanding and quantification of the current processes governing themovement of C by connecting terrestrial and marine systems is necessary to better estimate future changes ofwaterborne C. This thesis investigates how the sub-arctic landscape influences the waterborne carbon exportby combining data-driven and modeling methods across spatial and temporal scales. First, a study of the stateof total organic carbon monitoring in northern Scandinavia was carried out using national-scale monitoringdata and detailed data from scientific literature. This study, which highlights the consistency in land cover andhydroclimatic controls on waterborne C across northern Scandinavia, was combined with three more detailedstudies leveraging field measurements and modeling. These focused on the Abisko region to provide insightto processes and mechanisms across scales. The thesis highlights that the governing transport mechanismsof dissolved organic and inorganic carbon (DOC and DIC respectively) are fundamentally different due todifferences in release rates associated with the nature of their terrestrial sources (geogenic and organic matterrespectively). As such, the DIC mass flux exhibits a high flow-dependence whereas DOC is relatively flowindependent.Furthermore, these investigations identified significant relationships between waterborne C andbiogeophysical as well as hydroclimatic variables across large to small spatial scales. This thesis demonstratesthat both surface and sub-surface hydrological processes (such as flow pathway distributions) in combinationwith distributions of C sources and associated release rates are prerequisite for understanding waterborne Cdynamics in northern streams. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Submitted. Paper 4: Accepted.</p>

This thesis focuses on problematics of fracture mechanics. It aimes to comprehensively explain theoretical knowledge in both Czech Republic and abroad, where a research of this field is taken more often. Based on theoretical research best way to determine fracture toughness was selected. For this purpose three sets of spruce specimens (using three different adhesives) were created and tested by 3ENF test under the mode II while being monitored by digital image correlation method. From these values strain release rate energy and fracture toughness of tested specimens were determined. The thesis compares found data and analyses their correlations.

This thesis examines punching shear response of reinforced-concrete flat slabs under fire conditions. The shear behaviour of concrete in fire is relatively poorly understood compared to its flexural response. Failures such as the Gretzenbach car park failure in Switzerland (2004) have prompted concerns over the punching shear capacity of flat slabs in fire. The shear behaviour of reinforced-concrete in fire depends on degradation of the individual material properties with temperature, their interaction, and more recently recognised, the effects of restrained thermal expansion. Through experimental testing this thesis aims to build a foundation understanding of the punching shear behaviour of flat reinforced-concrete slabs in fire conditions. A series of shear blocks, tested after exposure to elevated temperature (realistic fire temperature), were used to develop an understanding of the effects of elevated temperature on the shear transfer performance of reinforced-concrete. These tests allowed the complex interplay of shear-carrying mechanisms at ambient temperature to be extended to the case of post-elevated temperature. Fifteen slab-column punching shear specimens were tested under both applied load and extreme heating. In particular, the effects of restrained thermal expansion were experimentally investigated by altering the support conditions of the slab-column specimens. A purpose-built restraint frame allowed the boundary support conditions to be either fully restrained or unrestrained. This experimental series is the only series to have tested restrained specimens at elevated temperatures, though previous researchers have simulated the thermal restraint effects and reported the importance of restrained thermal expansion and curvature on the behaviour of punching shear. Parameters of slab thickness and reinforcement ratio were also varied to investigate their respective impacts on punching shear behaviour at elevated temperature. The thicker 100 mm reinforced slabs failed in punching shear, whereas the 50 mm and 75 mm thick slabs failed in flexure-shear mechanisms and the unreinforced slabs failed in flexure. Clear behavioural differences were observed between specimens with different support conditions. Unrestrained 100 mm thick slabs under sustained load failed soon after heating began, whereas none of the corresponding restrained specimens failed during heating. One restrained, heavily reinforced specimen failed during cooling, whilst under sustained load. This is the first recorded punching shear failure during the cooling phase of an elevated temperature test and may also be the first recorded test specimen ever to have failed during the cooling phase of an elevated temperature test. This failure highlights the unknown and potentially unsafe behaviour of structures during the cooling phase. Further structural investigation of the cooling behaviour of concrete flat slabs after exposure to fire, needs to be undertaken. Most of the specimens’ central deflection was away from the heat source (in the direction of loading) during the whole test, irrespective of support condition. The test setup was assessed to investigate the unusual slab-column deflection away from the heat source, however the complex behaviour observed during the tests cannot currently be explained. It is assumed that the degradation in concrete properties and non-linear material behaviour dominates over the thermal expansion of the slabs. Quantitative and qualitative comparisons are presented, though the quantitative data is impacted by size effect, non-repeatable heating application between tests and jack friction influences on specimens with low capacities. Eurocode 2 punching shear prescriptive elevated temperature design, extends the ambient temperature equation for elevated temperature use, by degrading the temperature-dependant parameters by factors. Support conditions are not considered, with the code specifically telling the designer not to consider in-plane thermal expansion effects, therefore consequently ignoring the premature punching shear failure that can occur. Furthermore, the ambient temperature equation is based on the regression of available experimental data at the time and does not consider the reinforcement as a shear transfer mechanism. The experimental capacities of the 100 mm thick, reinforced slabs that failed in pure punching shear mechanism were similar to the Eurocode 2 punching shear prescriptive design capacity, when directly compared. The unrestrained support condition was shown to be consistently, not conservatively predicted by Eurocode 2, whereas the restrained support condition capacities were conservatively predicted. It is comforting to know that the Eurocode 2 design predicts the restrained supported slabs conservatively, as real buildings are more likely to have supports closer to the restrained condition rather than the unrestrained support condition. A sensitivity analysis of the Eurocode 2 prescriptive design equation shows it is highly sensitive to the concrete strength degradation and not the variable, cp, which was used to make a support condition comparison in this thesis. This indicates how the Eurocode 2 equation for punching shear capacity lacks in its consideration of whole structural behaviour. The Critical Shear Crack Theory has been proposed as the background to a harmonised shear design approach, called Model Code 2010. The Critical Shear Crack Theory was safe in predicting the experimental punching shear capacities. There were large variances for the 100 mm thick slabs, however they are consistent with the original model comparison to test data. An expansion of the Critical Shear Crack Theory for elevated temperature requires further validation with experimental restrained thermal expansion tests, such as those presented in this thesis. Finally, a digital image correlation technique has been proven to be a reliable method to measure structural displacements of concrete at elevated temperatures. Digital image correlation allowed the crack locations and slab rotation angles to be visualized throughout testing. No other measurement techniques are able to provide similar versatility in fire testing such as that presented herein.

The motivation to use lightweight materials in the construction of the automotive structure is the resultant increased fuel efficiency. However, these materials possess certain drawbacks that make it challenging to adopt them into current automobile manufacturing processes. In this dissertation the microstructural response observed in a magnesium alloy, AZ31, and an advanced high strength steel alloy, QP1180, to uniaxial deformation is analyzed and the results are presented. In AZ31 the required slip modes are not activated at room temperature leading to its low ductility at room temperature. The resulting activity of these twins in response to uniaxial tension is analyzed and its correlations with the microstructure features is reported. Additionally, a neighborhood viscoplastic self-consistent model is developed that will allow more accurate simulation of twin response to outside deformation. Furthermore, activity of slip modes that are usually observed at high temperatures (>200°C) are also observed at lower temperatures (<125°C) and they are compared to the relative twin activity at these temperatures. It is observed that larger grains, with high schmid factors, longer grain boundaries and have misorientation with its neighboring grain greater than 27° are more favorable for twin formation and transmission in the AZ31 microstructure in response to uniaxial tension. The nature of retained austenite (RA) transformation into martensite that gives QP1180 its enhanced ductility, is not clearly understood primarily because of challenges present in characterization of these metastable RA. Further, a 2 dimensional characterization method does not provide the complete information of the RA grain. These challenges are overcome by characterization of a 3 dimensional volume element using serial sectioning and EBSD followed by reconstruction using DREAM3D. The influence of 3d morphology and orientation direction on RA transformation is studied using as-is and uniaxially deformed samples. A novel shear affinity factor is introduced as a metric to describe the ease of RA transformation under uniaxial tension. The 3d nature of the information collected allows a new classification of disk shape in addition to globular and lamellar shapes for RA. It is found that RA that are low volume laths and have low shear affinity factor transform later compared to disk shaped RA’s. Through these guidelines the preparation of a microstructure that is conducive to RA transformation under uniaxial tension is possible.

There is currently an interest in optimizing the structural design to improve materials' strength to weight ratio or improve stiffness for energy absorption. As such, cellular structures are continuously studied and improved. However, it is a well-known fact in the literature that one primary mechanism of failure of a honeycomb is the formation of shear bands. The impacts of these shear bands bring many questions and unknowns, especially when the cellular structures are created with the increasingly popular manufacturing technique of 3D printing. Therefore, understanding the deformations in 3D printed honeycomb structures is necessary to explain the behavior of materials generated through new additive manufacturing techniques and further the knowledge of the deformation localization and, consequently, formations of shear bands in the deformation process of cellular structures.In the first phase of this work, samples with a unit cell regular hexagonal honeycomb format were designed and manufactured using masked-stereolithography (M-SLA). After the curing process, the samples were prepared with a paint application in the format of speckle, and DIC was realized in a compression experiment to identify and analyze the presence of high strain regions indicating the presence of shear bands. A second phase was then conducted, aiming to consider the control and manipulation of the shear band through the utilization of relief holes. The results demonstrated that adding incisions in specific parts of the polymeric honeycomb makes it possible to change its strain spread through the shear band and change its toughness.

No description available.

Previous modeling of wood materials has included many assumptions of unknown mechanical properties associated with the hierarchical structure of wood. The experimental validation of previous models did not account for the variation of mechanical properties present in wood materials. Little research has explored the uncertainties of mechanical properties in earlywood and latewood samples as well as wood strands. The goal of this study was to evaluate the effect of the intra-ring properties and grain angles on the modulus of elasticity (MOE) and ultimate tensile strength (UTS) of different orientation wood strands and to analyze the sensitivity of the MOE and UTS of wood strands with respect to these variables. Tension testing incorporating digital image correlation (DIC) was employed to measure the MOE and UTS of earlywood and latewood bands sampled from growth ring numbers 1-10 and growth ring numbers 11-20. A similar technique adjusted for strand size testing was also applied to measure the MOE and UTS of different orientation wood strands from the two growth ring numbers. The stochastic finite element method (SFEM) was used with the results from the earlywood and latewood testing as inputs to model the mechanical property variation of loblolly pine wood strands. A sensitivity analysis of the input parameters in the SFEM model was performed to identify the most important parameters related to mechanical response. Modulus of elasticity (MOE), Poisson ratio, and ultimate tensile strength (UTS) from earlywood and latewood generally increased as the growth ring number increased except for the UTS of latewood, which showed a slight decrease. MOE and UTS from radial, tangential, and angled grain orientation strands increased as the growth ring numbers increased while MOE and UTS from cross-grain strands decreased as the growth ring number increased. Shear modulus of wood strands increased as the growth ring number increased while shear strength decreased as the growth ring number increased. Poisson ratio from radial and angled grain strands decreased as the growth ring number increased while Poisson ratio from tangential and cross grain orientation strands increased as the growth ring number increased. The difference of average MOE from different grain strands between experimental results and SFEM results ranged from 0.96% to 22.31%. The cumulative probability distribution curves from experimental tests and SFEM results agreed well except for the radial grain models from growth ring numbers 11-20. From sensitivity analysis, earlywood MOE was the most important contributing factor to the predicted MOE from different grain orientation strand models. From the sensitivity analysis, earlywood and latewood participated differently in the computation of MOE of different grain orientation strand models. The predicted MOE was highly associated with the strain distribution caused by different orientation strands and interaction of earlywood and latewood properties. In general, earlywood MOE had a greater effect on the predicted MOE of wood strands than other SFEM input parameters. The difference in UTS between experimental and SFEM results ranged from 0.09% to 11.09%. Sensitivity analysis showed that grain orientation and growth ring number influenced the UTS of strands. UTS of strands from growth ring numbers 1-10 showed strength indexes (Xt, Yt, and S) to be the dominant factors while UTS of strands from growth ring numbers 11-20 showed both strength indexes and stress components (Ï 1, Ï 2, and Ï 12) to be the dominant factors. Grain orientations of strands were a strong indicator of mechanical properties of wood strands. / Ph. D.

L'état actuel de l'art lié à la technologie de conversion de la biomasse a, jusqu'à présent,principalement concerné les méthodes enzymatiques, éventuellement couplées à des prétraitements thermomécaniques ; les biomasses concernées sont généralement riches en cellulose, mais le matériel à haute teneur en amidon brut est également important des deux points stratégique et économique. Notre nouvelle stratégie est une contribution à l’étude de ce dernier type de biomasses riches en amidon, en vue d’une conversion comportant une seule étape de transformation en oligosaccharide et en glucose, à l’aide de la technologie thermo-mécanique de Détente Instantanée Contrôlée DIC. Cette opération a été étudiée,analysée, modélisée et optimisée. Contrairement à un traitement thermique conventionnel,la technologie DIC comporte deux étapes incluant l’instauration d’un vide capable d'accroître l'accessibilité de la vapeur dans la biomasse, puis d’une étape de vide final en vue de réduire la génération de molécules de dégradation thermique du glucose. L’analyse des composés (oligosaccharides, glucose…) a été réalisée ; elle a pu démontrer que le process était étroitement associée à la sévérité du traitement brut. Le prétraitement DIC de faible sévérité mène à des rendements élevés en fractions oligo saccharidiques avec une petite fraction de glucose. Par contre, le traitement DIC de haute sévérité permet d’accéder au glucose comme principal produit final. Au cours de l'étude exploratoire, le cycle de vide et de haute pression d'humidité a été établi, avec comme facteur de réponse le taux de conversion de l'amidon en glucose brut. Les deux facteurs de pression de vapeur d’eau et de vide ont été combinés ensemble afin d'optimiser trois autres facteurs opératoires : la concentration d'acide, le couple de pression/température et le temps de traitement. Le traitement DIC de haute sévérité a été démontré comme étant capable de convertir près de50% d'amidon brut en glucose à l'étape du simple et unique traitement thermomécanique.Une autre étape du processus a été impliquée : il s’agit de l'hydrolyse à l’acide dilué, souvent à la suite du prétraitement DIC. Au cours de l’étape d'optimisation du prétraitement DIC, la méthodologie de surface de réponse a été utilisée pour aider au développement de modèles cinétiques auto-hydrolysés DIC. D'autre part, les modèles empiriques de la cinétique ont été développés. Dans le cas de faible sévérité, le modèle aboutit à des réponses étroitement associées aux deux limites inférieures et supérieures de la concentration acide et du temps de traitement. Par contre, ces modèles quand ils sont obtenus à de niveaux de traitement grande sévérité, ont été jugés seulement associés aux valeurs supérieures de ces paramètres opératoires. Cette observation a été déduite de l’équation polynomiale utilisée, tandis que les modèles cinétiques ont été basés sur une série exponentielle. Une série polynomiale de plus grand ordre serait donc nécessaire pour pouvoir explorer avec précision les données de la surface de réponse pour ce genre d'analyse approfondie à tous les niveaux des facteurs.Lors de l'étape d'optimisation de l’hydrolyse dans une solution d'acide dilué, le premier modèle cinétique consécutive a été développé pour étudier les mécanismes de conversion des polysaccharides totale en glucose et en ses produits de dégradation. Le modèle empirique de surface de réponse a été utilisé pour étudier les effets de facteurs pendant le processus opératoire. La teneur en humidité et le cycle de vide ont été des facteurs communs. Plus le temps de traitement est court et plus la température est élevée, et plus la génération du glucose est importante. Cette étude montre que le traitement DIC de haute sévérité est capable de convertir les polysaccharides totaux en glucose avec une faible dégradation du glucose. Les produits solides résiduels pourraient également faire l’objet d'un traitement enzymatique. / Present state of art related to biomass conversion technology so far was found to concentrate on an enzymatic process, coupled with thermal pretreatment on biomass rich in cellulose. Biomass that rich in crude starch is also important in terms of strategic and economic point of view. The main objective of this study is to adopt a new strategy for a single step conversion of a crude starch material into oligosaccharide and glucose utilizing DIC technology. In contrast to existing thermal based pretreatment, DIC technology involves two vacuum cycles; first vacuum cycle was to increase steam accessibility on biomass and to reduce generation of steam condensate thus avoid losing of monosaccharide and hemicelluloses, while second vacuum cycle was to reduce potential thermal degradation of glucose. Distributions of products formed were found to be closely associated with severity of treatment on crude starch material. At lower DIC severity, pretreatment favors the formations of high oligosaccharide composition with small fraction of glucose; while at high DIC severity, pretreatment favors formation of high glucose as a major end product. During an exploratory study to establish the relevant reaction factors; vacuum cycle and moisture content were the two main factors influencing the conversion of crude starch into glucose.DIC starch conversion into glucose was found to be moisture dependent. Both factors were combined together to optimize the other three factors: pressure/temperature, treatment times, and acid concentration. High DIC severity treatment alone could convert nearly 50% of crude starch into glucose. During DIC optimization, an experimental design was developed and tested with DIC pretreatment in order to obtain a second order polynomial mathematical model that was then applied for response surface methodology (RSM). The interaction nature of above factors was examined and was found they depend on DIC treatment severity. Two experimental designs with low and high DIC severity were developed; Low DIC severity (acid: 0.01-0.05 molar, time: 0.5-3.0 min) and High DIC severity (acid: 0.05-0.20 molar, time: 3.0-10.0 min) with similar temperature range (144-165oC) were used. Data mining operation was done on RSM model to develop a kinetic model at both treatment severities. Kinetic data, including rate constant and activation energy were calculated from kinetic models of both severities to compare with actual dilute acidhydrolysis kinetic studies on two DIC treated samples. It was found that activation energy (Ea)for glucose generation at High DIC severity (Ea: 59.44 kJ/mol) was lower than at optimum dilute acid hydrolysis (Ea: 91.30 kJ/mol); while for glucose degradation, Ea was higher with High DIC severity (Ea: 144.12 kJ/mol) if compared to dilute acid hydrolysis (Ea: 45.14 kJ/mol).This indicates that glucose generation with DIC requires less energy while its degradation needs high energy. This combination was required to maximize glucose generation and minimize glucose degradation. Further studies with non-isothermal state during DIC and dilute acid hydrolysis support this finding. In normal polysaccharide conversion to low molecular weight (LMW) oligosaccharides and glucose procedures; two process steps were involved, namely the first process involved thermal pretreatment followed by a second process with dilute acid hydrolysis. In the present work, attempt was made to exclude dilute acid hydrolysis stage in order to establish that DIC process alone is sufficient for total polysaccharides conversion into LMW mainly glucose fraction. Information gathered from quantitative and statistical analysis on (i) exploratory studies, (ii) kinetic models from RSM of DIC process and (iii) kinetic data based on experimental works during dilute acid hydrolysis study; support the assumption that DIC treatment alone is sufficient for the total conversion required.

In today’s packaging industry HDPE is widely used and correct understanding of itsproperties and how to model them is of vital importance. HDPE is a semi-crystallinepolymer with a known strain rate dependence, that is a higher yield and lower strainto failure at higher strain rates. HDPE does also exhibit the phenomena of cold-drawing, together with other polymers. Cold-drawing is where after the specimenhas necked, the necking stabilizes and starts to pull material above and below intothe neck, effectively elongating the neck while maintaining its width. The objective of the study is to look at the local strain rates as the specimen necksand if a simple Abaqus model can capture those effects. The effect of strain rate onthe shape of the neck was also studied. The work was to test HDPE in uniaxial tension with different strain rates (∼10-3 s-1to ∼10-1 s-1) and measure the local strain rates with 2D-DIC. A decent amount oftime was used to make sure the camera setup gave the best quality possible for theequipment available. The videos produced was used for the DIC analysis as well asfor the image analysis to measure the width of the neck. After the tests a calibrationscheme was used to create a material model that matched the force-displacementfrom the physical 100 mm/min test data. Studying the force displacement the strain rate effects noted in previous researchare present. The results from the DIC show a very high local strain rate as the spec-imen necks, between 11-65 times higher than the global (grip-to-grip) strain rate.From the measurement of the width there are some rate effects as well. The slowerspeeds (5 and 10 mm/min) shows a continually reducing width while the 50 and 100mm/min shows a more stable neck and the 500 mm/min test does not have any sig-nificant neck propagation. The simple elastic-plastic model show similar local strainrates as the experiment however does show a noticeable thinner neck. / I dagens förpackningsindustri används HDPE ofta och korrekt förståelse av dess egenskaper och hur man modellerar dem är av avgörande betydelse. HDPE är ensemikristallin polymer med ett känt töjningshastighetsberoende, det vill säga en hö-gre sträckgräns och lägre töjning till brott vid högre töjningshastigheter. HDPEuppvisar också fenomenet kalldragning, tillsammans med andra polymerer. Kall-dragning är det fenomen som uppstår efter att provet har påbörjat midjebilding ochmaterial börjar dras in i midjan, vilket leder till en förlängd midja. Syftet med studien var att titta på de lokala töjningshastigheterna under midje-bildning och om en enkel Abaqus-modell kan fånga dessa effekter. Effekten av töjn-ingshastighet på midjan form studerades också. Arbetet började att testa HDPE i enaxlig spänning med olika töjningshastigheter(∼10-3 s-1 till ∼10-1 s-1) och mäta de lokala töjningshastigheterna med 2D-DIC. Endel tid lades ner på att se till att kamerauppsättningen gav högsta möjliga kvaliteti förhållande till den utrustning som användes. Filmen från testerna användes bådeför DIC och en bildanalys för att mäta bredden på midjan. Efter testerna använ-des ett kalibreringsschema för att skapa en materialmodell för att matcha kraft-förskjutningskurvan från det fysiska 100 mm/min-testet. Genom att studera kraft-förskjutning är effekterna av töjningshastigheten som noter-ats i tidigare forskning närvarande. Resultaten från DIC visar en mycket hög lokaltöjningshastighet under midjebildning, mellan 11-65 gånger högre än den globala(grepp-till-grepp) töjningshastigheten. Från mätningen av bredden finns det ocksåvissa hastighetseffekter. De lägre hastigheterna (5 och 10 mm/min) visar en kon-tinuerligt minskande bredd, 50 och 100 mm/min visar en stabilare midja och 500mm/min-testet har ingen signifikant kalldragning. Den enkla elasto-plastmodellenvisar liknande lokala töjningshastigheter som experimentet men de visar en märk-bart tunnare midja.

In der vorliegenden Arbeit wurden Experimente zur Fallgewichtsverdichtung in Modellversuchen im Erdschwerefeld (1g) durchgeführt. Ziel der Versuche war es, das Verformungsverhalten eines Versuchssandes in hoher räumlicher und zeitlicher Auflösung zu erfassen und Nachrechnungen im Sinne von Benchmark-Tests zu ermöglichen. Die messtechnische Erfassung des Bodenverhaltens erfolgte vor allem durch die optische Messmethode der digitalen Bildkorrelation (DIC, englisch: Digital Image Correlation). Ein wichtiger Teil der Arbeiten war in diesem Zusammen-hang die Eignungsprüfung der Messmethode an den eigenen Versuchsständen. Im Rahmen einer Variantenstudie mit 22 Modellkonfigurationen wurde zudem die Bedeutung von Steuergrößen der Fallgewichtsverdichtung hinter-fragt. Numerische Berechnungen wurden mit der Finite-Elemente-Methode (FEM) durchgeführt. Mit den Versuchen konnte Verschiebungen des Versuchssandes an der Sicht-ebene in hoher räumlicher Auflösung gemessen werden. Für die Erfassung bodendynamischer Vorgänge konnte die DIC-Auswertung von Hochge-schwindigkeitsaufnahmen sowie von Beschleunigungssensoren im Boden erfolgreich eingesetzt werden. Die DIC-Messung eines Granulats hinter einer transparenten Sichtebene führt zu einer Streuung der Verschiebungsergebnisse, was wiederum negative Auswirkung auf die Ermittlung von kleinräumigen Dehnungen hat. Eine besondere Herausforderung stellte in diesem Zu-sammenhang die Erfassung einer Änderung der Dichte bzw. Porenzahl über die naturgemäß kleinen Betragsänderungen der volumetrischen Dehnung dar. Das Verformungsverhalten des Versuchssandes zeigte bei der Fallgewichts-verdichtung große Ähnlichkeiten zu Versuchen mit statischer Auflast. Ergebnisse der Variantenstudie zeigen Zusammenhänge zwischen Steuergrößen der Fallgewichtsverdichtung und der Einflusstiefe auf. Es wird deutlich, dass die in der Baupraxis verbreitete Größe der potentiellen Fallenergie nur begrenzt für eine Klassifizierung von Fallgewichtskonfigurationen geeignet ist.:1 Einleitung 1 2 Zur praktischen Bedeutung der Fallgewichtsverdichtung 6 2.1 Geschichte der Verdichtung mit Fallgewichten 6 2.2 Anwendungsbereiche 6 2.3 Bodenmechanische Vorgänge während der Verdichtung 8 2.4 Wellenausbreitung bei impulsförmigem Energieeintrag 8 2.5 Bewertung des Verdichtungserfolges 9 3 Überblick zu experimentellen und rechnerischen Untersuchungen zur Fallgewichtsverdichtung 11 3.1 Feldversuche 11 3.2 Modellversuche 12 3.3 Berechnungsverfahren 29 4 Versuchstechnische Grundlagen 34 4.1 Geotechnische Experimente und deren Anforderung 34 4.2 Konzeption von Modellversuchen 35 4.3 Wahl und Realisierung von Randbedingungen 38 4.4 Erfassung und Auswertung von Messgrößen 38 4.5 Digital Image Correlation (DIC) 40 5 Versuchssand, Versuchsstände und Einbaumethoden 52 5.1 Versuchssand 52 5.2 Versuchsstand-C 54 5.3 Versuchsstand-S 57 5.4 Versuchsstand-M 61 5.5 Einbaumethoden 68 5.6 Kontrolle der Probenhomogenität 73 6 Versuche mit statischer Auflast 79 6.1 Versuchsprogramm und Ziele 79 6.2 Kompressionsversuche 81 6.3 Streifen- und Kreisfundamentversuche 93 6.4 Ergänzende Messungen 103 6.5 Zusammenfassung 106 7 Versuche mit skalierten Fallgewichten 108 7.1 Versuchsprogramm und Ziele 108 7.2 Fallgewichtsversuche im ebenen Verformungszustand 109 7.3 Fallgewichtsversuche als Halbmodell 115 7.4 Ergebnisse zusätzlicher Sondierungen 122 7.5 Ergänzende Messungen 125 7.6 Kinematik 130 7.7 Versuchsstudie zur Fallgewichtsverdichtung 133 7.8 Zusammenfassung 150 8 Vergleich zwischen statischen und dynamischen Versuchen 153 9 Numerische Berechnungen mit der Finite-Elemente-Methode 157 9.1 Grundlagen der verwendeten Finite-Elemente-Methode 157 9.2 Bestimmung der Stoffmodellparameter 160 9.3 Simulation der Kompressionsversuche 161 9.4 Simulation der Streifenfundamentversuche 170 9.5 Simulation der Fallgewichtsversuche 176 9.6 Kinematik 182 9.7 Zusammenfassung 186 10 Zusammenfassung 188 11 Ausblick Literaturverzeichnis 196 Anhang A Versuchsstudie zur Fallgewichtsverdichtung 204 A.1 Einzelversuche am Versuchsstand-S 204 A.2 Einzelversuche am Versuchsstand-M 208 Anhang B DIC-Studien an idealisiertem Versuchsaufbau 213 Anhang C Studie zu Zwischenbezugsschritten in ISTRA4D 220 Anhang D Studie zur Ermittlung von Dehnungen in ISTRA4D 223 Anhang E Kalibrierung der Stoffmodellparameter in Abaqus 227 Anhang F Hypoplastisches Stoffmodell ohne intergranulare Dehnung 229 Anhang G Hypoplastisches Stoffmodell mit intergranularer Dehnung 232 / A quantitative validation of numerical simulations of soil dynamic problems and the derivation of physical relationships needs appropriate experimental data. Within the scope of the present work, experiments on the heavy tamping in small-scaled models in earth's gravity (1g) were developed. The aim of the experiments was to record the deformation behavior of a test sand in high spatial and temporal resolution and to allow re-calculations in the sense of benchmark tests. The optical measuring method of digital image correlation (DIC) were mainly carried out for the metrological recording of the soil behavior. By comparing discrete image areas of a few grains of sand (patches), it is possible to full-field capture soil displacements behind a vertical viewing plane. In this context, an important part of the work was the suitability test of the measuring method at the own experiments. A variant study with 22 model configurations also questioned the importance of control factors of heavy tamping. The numerical calculations were performed with the finite element method (FEM) in Abaqus. Therefore, the simulation of individual special tests with static load were done using classical Lagrangian FEM. Experiments as well as with large soil deformations as well as heavy tamping were modeled using the Coupled Eulerian Lagrangian (CEL) method. As material model, a formulation of the hypoplasticity with extension to the concept of intergranular strains was used. The experiments showed that the optical measuring method of the DIC is capable of reliably detecting shifts of the test sand at the viewing plane in high spatial resolution. For the acquisition of soil dynamic processes, the DIC evaluation of high-speed recordings as well as of acceleration sensors in the soil could be successfully carried out. Experimental and metrological challenges resulted from the effects of optical refraction through the viewing plane as well as the detection and tracking of patterns of individual patches. In comparison to direct measurement on rigid bodies, the detection of a granulate behind a transparent viewing plane leads to a greater scattering of the displacement results, which in turn has a negative effect on the determination of small-scale strains in the measuring plane. A particular challenge in this context was the detection of a change in the density or pore number over the inherently small changes in the magnitude of the volumetric strain. Remarkably, the deformation behavior of the sand in medium-dense storage showed under the influence of falling-weight compacting great similarities to the deformation behavior under static loading. With both load models, the measurement results point to successful compaction work below and to the side of the load transfer, which are due to vertical or horizontal strain components. The results of the study on heavy tamping show correlations between the control factors of heavy tamping to an influence depth. The study shows that the size of the potential fall energy, which is common in construction practice, is only limitedly suitable for the classification of heavy tamping configurations. The evaluation of a series of drops proves the possibilities of correlation between state variables of a soil such as void ratio or degree of compaction and the velocity of the propagation waves in the soil. In numerical calculations, the deformation behavior of static load tests could be reproduced well. It showed the importance of a sufficient consideration of boundary conditions like friction between sand and container wall, container deformations and silo effects in narrow containers. Recalculations of the heavy tamping tests led to plausible results with a significant compaction effect below the drop weight, which is amplified in further drops and extended to greater depths. This also corresponds to the experimental results as well as the contexts known in practical engineering.:1 Einleitung 1 2 Zur praktischen Bedeutung der Fallgewichtsverdichtung 6 2.1 Geschichte der Verdichtung mit Fallgewichten 6 2.2 Anwendungsbereiche 6 2.3 Bodenmechanische Vorgänge während der Verdichtung 8 2.4 Wellenausbreitung bei impulsförmigem Energieeintrag 8 2.5 Bewertung des Verdichtungserfolges 9 3 Überblick zu experimentellen und rechnerischen Untersuchungen zur Fallgewichtsverdichtung 11 3.1 Feldversuche 11 3.2 Modellversuche 12 3.3 Berechnungsverfahren 29 4 Versuchstechnische Grundlagen 34 4.1 Geotechnische Experimente und deren Anforderung 34 4.2 Konzeption von Modellversuchen 35 4.3 Wahl und Realisierung von Randbedingungen 38 4.4 Erfassung und Auswertung von Messgrößen 38 4.5 Digital Image Correlation (DIC) 40 5 Versuchssand, Versuchsstände und Einbaumethoden 52 5.1 Versuchssand 52 5.2 Versuchsstand-C 54 5.3 Versuchsstand-S 57 5.4 Versuchsstand-M 61 5.5 Einbaumethoden 68 5.6 Kontrolle der Probenhomogenität 73 6 Versuche mit statischer Auflast 79 6.1 Versuchsprogramm und Ziele 79 6.2 Kompressionsversuche 81 6.3 Streifen- und Kreisfundamentversuche 93 6.4 Ergänzende Messungen 103 6.5 Zusammenfassung 106 7 Versuche mit skalierten Fallgewichten 108 7.1 Versuchsprogramm und Ziele 108 7.2 Fallgewichtsversuche im ebenen Verformungszustand 109 7.3 Fallgewichtsversuche als Halbmodell 115 7.4 Ergebnisse zusätzlicher Sondierungen 122 7.5 Ergänzende Messungen 125 7.6 Kinematik 130 7.7 Versuchsstudie zur Fallgewichtsverdichtung 133 7.8 Zusammenfassung 150 8 Vergleich zwischen statischen und dynamischen Versuchen 153 9 Numerische Berechnungen mit der Finite-Elemente-Methode 157 9.1 Grundlagen der verwendeten Finite-Elemente-Methode 157 9.2 Bestimmung der Stoffmodellparameter 160 9.3 Simulation der Kompressionsversuche 161 9.4 Simulation der Streifenfundamentversuche 170 9.5 Simulation der Fallgewichtsversuche 176 9.6 Kinematik 182 9.7 Zusammenfassung 186 10 Zusammenfassung 188 11 Ausblick Literaturverzeichnis 196 Anhang A Versuchsstudie zur Fallgewichtsverdichtung 204 A.1 Einzelversuche am Versuchsstand-S 204 A.2 Einzelversuche am Versuchsstand-M 208 Anhang B DIC-Studien an idealisiertem Versuchsaufbau 213 Anhang C Studie zu Zwischenbezugsschritten in ISTRA4D 220 Anhang D Studie zur Ermittlung von Dehnungen in ISTRA4D 223 Anhang E Kalibrierung der Stoffmodellparameter in Abaqus 227 Anhang F Hypoplastisches Stoffmodell ohne intergranulare Dehnung 229 Anhang G Hypoplastisches Stoffmodell mit intergranularer Dehnung 232