Salt tectonics is a key player in the evolution of many worldwide sedimentary basins on rifted continental margins. For more than a century, the evolving structures have been studied; but focus remained primarily on the onshore and shallow-water regions. The evolution of the poorly studied deep-water salt-tectonic structures is the focus of this thesis. Investigations are performed using 2D numerical models that comprise a viscous salt layer overlain by a frictional-plastic passive margin sedimentary sequence from shelf to deep water. This thesis addresses multiple salt-tectonic processes (gravity spreading, evolution of fold belts and salt canopies, diapirism) in a general context but with special focus on the structural evolution of the northwestern Gulf of Mexico (GoM). Here, multiple phases of gravity-spreading induced salt mobilization and thin-skinned deformation occurred throughout the Cenozoic. During the latest, late Oligocene-Miocene phase, the Perdido Fold Belt (PFB) formed from a 4.5km thick pre-kinematic section as a prominent salt-cored deep-water structure above the pinch-out of the autochthonous salt. It is here demonstrated with analytical as well as numerical calculations that the folding of the PFB can have formed by gravity spreading alone without basement tectonics. A requirement for this deformation is very high pore-fluid pressure in the sediments, which effectively reduces the sediments' mechanical strength. These values are refined using numerical models that couple compaction-induced fluid pressure to mechanical deformation. It is shown that very high fluid pressure is only necessary at the landward base of the deforming system; fluid pressure in other regions may remain moderate. This study shows, for the first time, the regional and dynamic evolution of pore-fluid pressure in a continental margin sedimentary system above salt. Additionally, the contribution of `lateral compaction' during fold-belt evolution is addressed. Landward of the PFB, a large-scale canopy developed during the Eocene. Its evolution is studied by investigating three different concepts of canopy evolution that have been proposed in the scientific literature. A canopy evolving via the mechanism of squeezed diapirs is most similar to the Eocene canopy of the northwestern GoM. A canopy evolving via the mechanism of breached anticlines is similar to that observed above the landward end of the PFB. Dynamic diapir growth is addressed in a neutral stress regime under uneven sedimentation employing a new mechanism of diapir initiation and evolution.

The structural performance of Rounded Dovetail Connections (RDC) has been studied experimentally and numerically to provide information needed for connection structural design. RDC are mainly used to transfer vertical shear forces, but test results show that they can carry considerable load in tension and bending. Geometric parameters, such as dovetail flange angle and dovetail height are shown to significantly effect affect the structural performance of RDC. Results show that it is impractical to determine a set of empirical equations to describe the structural performance of RDC based on basic wood material properties. RDC manufactured and tested with low and constant moisture content outperformed those evaluated under other climatic conditions, and test results demonstrate that RDC should be produced at low machine speed and with minimal a gap between the connecting members. RDC in laminated strand lumber have higher capacity and fail under larger deformations compared to RDC in western hemlock. A three-dimensional finite element method model is presented and validated with experimental tests. Good agreement is achieved between the load deformation response predicted by the model and the experimentally observed load deformation response. Therefore the model is deemed suitable for estimating the stresses needed to develop failure criteria. A failure criterion for the analysis of RDC is presented taking into account size effect in the strength of wood. Based on the experimental and numerical studies, a design equation for RDC is presented that provides the engineering community with a new design tool. Finally, self tapping screws as reinforcement have been studied and are shown to significantly improve the structural performance of RDC under vertical shear loading.

This thesis reports a detailed investigation into the use of the Shear Strength Reduction (SSR) method to determine factor of safety values in discontinuum models using the Universal Distinct Element Code. The SSR method depends on the definition of failure within the model and two different criteria were compared: the numerical unbalanced force definition and a more qualitative displacement-monitoring based method. A parametric study was first undertaken, using a simple homogeneous rock slope, with three different joint networks representing common kinematic states. Lessons learned from this study were then applied to a more complex case history used for validation of the SSR method. The discontinuum models allow for the failure surface to propagate based on constitutive models that better idealize the rockmass than simpler methods such as limit equilibrium (e.g. either method of slices or wedge solutions) and even numerical continuum models (e.g. finite difference, finite element). Joints are explicitly modelled and can exert a range of influences on the SSR result. Simple elasto-plastic models are used for both the intact rock and joint properties. Strain-softening models are also discussed with respect to the SSR method. The results presented highlight several important relationships to consider related to both numerical procedures and numerical input parameters. The case history was modelled similar to how a typical forward analysis would be undertaken: i.e. simple models with complexities added incrementally. The results for this case generally depict a rotational failure mode with a reduced factor of safety due to the presence of joints within the rockmass when compared to a traditional limit equilibrium analysis. Some models with large persistence of steeply dipping joints were able to capture the actual failure surface. Softening models were employed in order to mimic the generation and propagation of joints through the rockmass in a continuum; however, only discontinuum models using explicitly defined joints in the model were able to capture the correct failure surface.

The recent development of prototyping systems which can produce patterns for investment casting with significant time reduction from traditional techniques, has raised interest in the use of casting as a method to produce tooling for downstream prototype testing. However, the accuracy of the casting process remains a major obstacle to the use of these tools. Simultaneous development of numerical modelling techniques suggest that it will be possible to predict casting contraction and distortion. If this were possible, corrections could be made before castings are produced, resulting in time and cost savings, as well as potential improvement in the accuracy. Before these models can be applied, there is a need for both material property data and experimental data with which to validate the numerical models. The aims of this work are to: 1) Develop further understanding of the processes in investment casting that contribute to the dimensional changes and variability. 2) Develop the required data for numerical modelling and apply this to simulate the dimensional changes in investment casting. An apparatus has been designed to measure the dimensional and thermal history of investment castings with displacement transducers and thermocouples. Casting dimensions were also accurately measured to determine the final contraction of nominally unconstrained and thermally constrained castings. Numerical simulations of the temperatures, stress and distortion were compared with the experimental results and provide a detailed explanation of the processes involved. Data for these simulations were developed using a combination of direct measurement and iterative inverse modelling.

Recent field observations suggest that the radiative forcing of aerosol and clouds in the Arctic may be seasonally regulated by the oceanic emissions of the climatically-important biogenic trace gas dimethylsulfide (DMS). However, the validity of the proposed argument is challenged by the limited spatio-temporal coverage of these earlier studies in this difficult-to-access region. In particular, little is known about the pan-Arctic distribution of the oceanic DMS emissions, its temporal variability, and the impacts of sea-ice biogeochemistry on these emissions. In this dissertation, I investigated these unexplored subjects through numerical modelling. Using a one-dimensional (1-D) column modelling framework, I developed a coupled sea ice-ocean biogeochemical model and assessed the impacts of bottom-ice algae ecosystems on the underlying pelagic ecosystems and the associated production and emissions of DMS. The model was calibrated by time-series measurements of snow and melt-pond depth, ice thickness, bottom-ice and under-ice concentrations of chlorophyll-a and dimethylsulfoniopropionate (DMSP), and under-ice irradiance obtained on the first-year landfast sea ice in Resolute Passage during May-June of 2010. Many of the model parameters for the DMSP and DMS production and removal processes were derived from recent field measurements in the Arctic, which is advantageous over the previous Arctic-focused DMS model studies as their model parameters were based on the measurements in extra-polar regions. The impacts of sea-ice biogeochemistry on the DMS production in the underlying water column and its potential emissions into the overlying atmosphere were quantified through sensitivity experiments. To extend the study domain to the pan-Arctic, I implemented the sea-ice ecosystem and the coupled sea ice-pelagic DMS cycling components of the 1-D column model into a three-dimensional (3-D) regional modelling framework. A multi-decadal model simulation was performed over the period 1969-2015 using realistic atmospheric forcing and lateral boundary conditions. The results of the simulation were evaluated by direct comparisons with available data products and reported values based on field and satellite measurements and other model simulations. The decline of Arctic sea ice was successfully simulated by the model. The magnitude of the pan-Arctic sea-ice and pelagic annual primary production and their general spatial patterns were comparable to other model studies. The mean seasonal cycle and the spatial distribution of the model-based surface seawater DMS climatology within the pan-Arctic showed some similarities with in situ measurement- and satellite-based climatologies. However, at the same time, the comparison of the DMS climatologies was challenged by the bias in the measurement-based climatology, emphasizing the need to update this data product, which was created almost a decade ago, by incorporating data acquired during the recent field campaigns. The analysis of the modelled fluxes of DMS at the ice-sea and sea-air interfaces revealed different responses to the accelerated decline of sea ice over the recent decades (1996-2015). There was no trend in the pan-Arctic ice-to-sea DMS flux due to the counteracting effect of vertical thinning and horizontal shrinking of sea ice that drove ice algal production. In contrast, the pan-Arctic sea-to-air DMS flux showed a consistent increase (about 40 % over the last two decades) driven by the reduction of sea ice cover that promoted outgassing and biological productivity. This finding suggests that the climate warming in the Arctic causes an increase in DMS emissions, and encourages further exploration of the biological climate regulation in the Arctic. / Graduate

Two streamline, ordinary differential equation (ODE) models for detonation, the Chan-Kirby model and the straight streamline approach of Watt et al., are extended to a multiphase system of equations. These multiphase equations, with realistic equations of state, are used to better capture the heterogeneities in non-ideal explosives used in mining applications. Streamline ODE multidimensional models are normally obtained by reducing the partial differential equations (PDEs) describing the motion of the material to ODEs by making approximations about some of the physics of the problem. These models are referred to as reduced ODE models in this work and are the primary focus of this research into fast, efficient solutions of non-ideal explosives. In the development of these reduced order forms, some terms in the full equations have been removed for analytical convenience. Although this is not always the result of a formal order of magnitude analysis, this somewhat empirical approach is justified by simulation studies. In particular, by demonstrating that in a variety of benchmark problems, the reduced order ODEs give similar results to those obtained from the much more complex, full order PDE models. Further support is obtained by comparing the reduced order solution with experimental results. Comparisons with multiphase direct numerical simulations and experiments are undertaken to investigate the effect of the approximations and assumptions made in the derivation of the models. Both models produce comparable diameter effect curves for two different non-ideal explosives, EM120D and ANFO, in unconfined conditions. Empirical assumptions in the Chan-Kirby model can be eliminated but investigation shows that the straight streamline multiphase extension is based on better approximations for non-ideal explosives. This latter approach also gives better prediction of the diameter effect curve and detonation driving zone shape. The multiphase straight streamline model is then extended to model confined multiphase detonations, with realistic equations of state for the confining material, and predicts most strong confinement examples well. Future work of extending to curved streamlines and including confinement other than strong or weak is discussed.

Title: Maxwell-type viscoelasticity in small and large deformations of planetary mantles Author: Mgr. RNDr. Vojtěch Patočka Department: Department of Geophysics Supervisor: prof. RNDr. Ondřej Čadek, CSc., Department of Geophysics Abstract: A present limitation of global-scale simulations of planetary interi- ors is that they assume a purely viscous or viscoplastic flow law for solid rock, i.e. elasticity is ignored. This is not a good assumption in the cold and strong outermost mantle layer known as the lithosphere, which seems to maintain its elastic properties even on time scales corresponding to the geological processes of subduction or sedimentation. Here we overcome such simplification and present a numerical tool for modelling visco-elasto-plastic mantle convection. The most promising new feature of the resulting models is related to the ability of vis- coelastic materials to remember deformation experienced in the past. Thus, the growing viscoelastic lithosphere of a cooling planet, when subject to internal or surface loading, can store information about its thickness at the time of loading. This phenomena is consistent with datasets of the effective elastic thicknesses determined in flexure studies and we label it here as the "stress memory effect". Attention is also paid to the theoretical foundations...

Ce rapport présente et analyse les différentes possibilités de modélisation directe et de grande envergure de la forme du fond des voies naviguables. Cette étude est motivée par le fait que dans la modélisation de rivière, les incertitudes quant à la prédiction de la profondeur et du mouvement du lit, peuvent souvent être affectées par sa forme. La forme du fond constitue le facteur dominant dans le transport solide de nombreux cours d´eau qui nécessitent donc d´être entretenus par les autorités compétantes.Des expériences hydrodynamiques et morphodynamiques ont été menées au sein de l´institut fédéral allemand de la recherche et de l´ingénieurie des cours d´eau (BAW). Des mesures en haute résolution ont été effectuées et ont révélé la formation naturelle de dunes tridimensionelles à l´équilibre avec le champ d´écoulement environnant. Le modèle hydrodynamique est calibré sur cette base de données pour modéliser le régime d´écoulement complexe à travers une suite de dunes tridimensionelles. Les résultats de la simulation montrent qu´il est possible de reproduire le champ d´écoulement turbulent mesuré dans la configuration précédemment citée et que le niveau d´eau mesuré et simulé est également en accord avec cette même configuration. La résolution verticale et horizontale du maillage, le coefficient de friction, la forme du lit à petite échelle et la modélisation turbulente sont identifiés comme paramètres sensibles durant le calibrage.La seconde partie de cette thèse se concentre sur les simulations morphodynamiques de ce même canal expérimental mais cette fois avec un lit mobile. La numérisation du fond mesuré en haute résolution montrant la formation et le développement des dunes au fil du temps, est mis à disposition pour la comparaison. La hauteur et la largeur des dunes tout comme le moment de distribution, l´inclinaison et l´aplatissement sont utilisés pour comparer les dimensions des dunes ainsi que leur forme et leur distribution spatiale. Les formules du transport solide, de l´inclinaison, de l´aplatissement, les conditions aux limites et la considération des éléments de rugosité de sous échelle sont les paramètres qui influencent le plus la qualité des résultats. Durant cette étude, une attention toute particulière a été portée sur l´intégration des fluctuations turbulentes dans le calcul de la contrainte de cisaillement du fond. Un nouveau calcul total de cette contrainte est proposé et incorpore les vitesses d´écoulement principales et l´énergie cinétique turbulente fournit par le modèle turbulent. Grâce à cette approche, le modèle numérique est capable de reproduire quantitativement et qualitativement les dimensions de la forme du lit principal mesurée et les moments de forme des dunes physiques. Cela s´avère être la seule façon de reproduire le bon moment de distribution (aplatissement) du champ de dunes.Finalement, le modèle est appliqué à l´échelle du projet et testé sur une portion de l´Elbe (Allemagne). Les simulations morphodynamiques en haute résolution couplées à l´hydrodynamique-3D sont menées durant plusieurs jours sur la portion de rivière choisit d´une longueur de 4 kilomètres. Les formes des dunes préservent les paramètres de forme et la vitesse des dunes est en accord avec celle mesurée. La simulation montre des résultats prométeurs concernant la possibilité d´un usage opérationel du modèle dans l´avenir. Des problèmes locaux et communs comme les stratégies d´entretien tel que les changements dans les sections transversales d´écoulement, les brises lames et le revêtement sont des missions possibles qui peuvent être examinées / In this work the possibilities of direct modelling of large scale bed forms in waterways are highlighted and analysed. It is motivated by the fact that in river modelling, uncertainties in predicting water depth and bed movement can often be attributed to bed forms. Those bed forms are the dominating factor for bed load transport in many river stretches, which need to be maintained by the responsible waterways authorities.Hydrodynamic and morphodynamic experiments have been conducted at the Federal Waterways Engineering and Research Institute of Germany (BAW). High-resolution measurements have been performed over fixed, naturally formed three-dimensional sand dunes, which are at equilibrium with the surrounding flow field.Using these measured data sets, the hydrodynamic model is calibrated to simulate the complex flow situation over a train of several three-dimensional dunes. Simulation results show that it is possible to reproduce the measured turbulent flow field in the wake of the fixed dunes and that the measured and simulated water levels agree for the chosen configuration. Vertical and horizontal mesh resolution, friction coefficient, small scale bed forms and turbulence modelling are identified as most sensitive parameters during the calibration.The second part of this thesis focuses on morphodynamic simulations of the same experimental flume but with a mobile bed. High resolution measured bottom scans of the dune forms, developing over time, are available for comparison. Dune height and length, as well as the distribution moments, skewness and kurtosis are used to compare the dimensions of the dunes and also their shape and spatial distribution.Bed load transport formulation, skewness and kurtosis formulae, boundary conditions and the consideration of sub-grid scale roughness elements are the parameters which influence the quality of the results the most. A particular focus during the study is the inclusion of turbulent fluctuations in bed shear stress calculation. A new, total bed shear stress calculation is proposed, which incorporates mean flow velocities and turbulent kinetic energy provided by the turbulence model. With this approach, the numerical model is able to reproduce both qualitatively and quantitatively the measured mean bed forms dimensions and the shape moments of the physical dunes. It proves to be the only way to also produce the right distribution moment (kurtosis) of the dune field.Finally, the model is applied to project scale and tested on a stretch of the riverElbe, Germany. High resolution morphodynamic simulations coupled to 3D-hydrodynamics are conducted over several days for the chosen river stretch which is 4km in length. The dune forms preserve form and shape parameters and the dune speed agrees with the measured one. The simulations show promising results concerning the possibility of operational use of the model in the future. Local problems and statements, e.g. maintenance strategies such as changes in flow cross section, groynes and revetments, are possible tasks that can be examined

The structural performance of Rounded Dovetail Connections (RDC) has been studied experimentally and numerically to provide information needed for connection structural design. RDC are mainly used to transfer vertical shear forces, but test results show that they can carry considerable load in tension and bending. Geometric parameters, such as dovetail flange angle and dovetail height are shown to significantly effect affect the structural performance of RDC. Results show that it is impractical to determine a set of empirical equations to describe the structural performance of RDC based on basic wood material properties. RDC manufactured and tested with low and constant moisture content outperformed those evaluated under other climatic conditions, and test results demonstrate that RDC should be produced at low machine speed and with minimal a gap between the connecting members. RDC in laminated strand lumber have higher capacity and fail under larger deformations compared to RDC in western hemlock. A three-dimensional finite element method model is presented and validated with experimental tests. Good agreement is achieved between the load deformation response predicted by the model and the experimentally observed load deformation response. Therefore the model is deemed suitable for estimating the stresses needed to develop failure criteria. A failure criterion for the analysis of RDC is presented taking into account size effect in the strength of wood. Based on the experimental and numerical studies, a design equation for RDC is presented that provides the engineering community with a new design tool. Finally, self tapping screws as reinforcement have been studied and are shown to significantly improve the structural performance of RDC under vertical shear loading. / Forestry, Faculty of / Graduate

This thesis reports a detailed investigation into the use of the Shear Strength Reduction (SSR) method to determine factor of safety values in discontinuum models using the Universal Distinct Element Code. The SSR method depends on the definition of failure within the model and two different criteria were compared: the numerical unbalanced force definition and a more qualitative displacement-monitoring based method. A parametric study was first undertaken, using a simple homogeneous rock slope, with three different joint networks representing common kinematic states. Lessons learned from this study were then applied to a more complex case history used for validation of the SSR method. The discontinuum models allow for the failure surface to propagate based on constitutive models that better idealize the rockmass than simpler methods such as limit equilibrium (e.g. either method of slices or wedge solutions) and even numerical continuum models (e.g. finite difference, finite element). Joints are explicitly modelled and can exert a range of influences on the SSR result. Simple elasto-plastic models are used for both the intact rock and joint properties. Strain-softening models are also discussed with respect to the SSR method. The results presented highlight several important relationships to consider related to both numerical procedures and numerical input parameters. The case history was modelled similar to how a typical forward analysis would be undertaken: i.e. simple models with complexities added incrementally. The results for this case generally depict a rotational failure mode with a reduced factor of safety due to the presence of joints within the rockmass when compared to a traditional limit equilibrium analysis. Some models with large persistence of steeply dipping joints were able to capture the actual failure surface. Softening models were employed in order to mimic the generation and propagation of joints through the rockmass in a continuum; however, only discontinuum models using explicitly defined joints in the model were able to capture the correct failure surface. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate