A importância do estudo de aqüíferos livres e rasos se evidencia quando se leva em conta que tais aqüíferos são altamente vulneráveis a contaminação e que em geral se encontram em regiões densamente povoadas. Com o objetivo de melhor compreender a dinâmica do fluxo de água subterrânea na zona saturada destas formações aqüíferas, foi construído e calibrado um detalhado modelo tridimensional e transiente para representar o fluxo subterrâneo em uma porção de um aqüífero livre e raso que ocorre no Parque Ecológico do Tietê, no Município de São Paulo. Este modelo, baseado em dados de cargas hidráulicas de 81 poços de monitoramento instalados em uma área de 320m2 medidas diariamente, em valores diários de precipitação na área e em 75 determinações de condutividades hidráulicas, foi construído e executado através do software Visual MODFLOW e calibrado por meio do software PEST, através de um método de regressão não linear. Os resultados gerados por este modelo para um evento de recarga rápida indicam que a distribuição de cargas hidráulicas na área de estudo é governada pela recarga regional, pela distribuição das condutividades hidráulicas horizontais e pelas vazões específicas das camadas superiores da formação, mas é praticamente independente da intensidade e distribuição temporal da recarga local, que influencia apenas os níveis mais rasos da formação. Além disso, verifica-se o caráter extremamente dinâmico do fluxo, que responde rapidamente ao evento de recarga regional, apresentando alterações significativas de intensidade e direção no intervalo de apenas alguns dias. Tais resultados, verificados apenas por meio de um modelo tão detalhado como o produzido neste trabalho, sugerem que estratégias comuns de avaliação podem não ser capazes de avaliar suficientemente bem o comportamento deste tipo de aqüífero. / The importance of studying unconfined and shallow aquifers is verified when taking into account that these aquifers are highly vulnerable to contamination and that they are often located under heavily populated regions. A detailed three-dimensional and transient model, which represents the groundwater flow in an area of an unconfined and shallow aquifer at the Parque Ecológico do Tietê, in the Municipality of São Paulo, Brazil, was created and calibrated with the objective of enhancing the comprehension of the dynamics of the groundwater flow in the saturated zone of these formations. This model was based on hydraulic head data of 81 monitoring wells, which were installed in an area of 320 m2 and measured on a daily basis, on daily values of precipitation occurring in the area and 75 determinations of hydraulic conductivities. The model was created and run using the software Visual MODFLOW and calibrated using the software PEST, based on a non-linear regression method. The results generated by this method for an event of rapid recharge indicate that the distribution of the horizontal hydraulic conductivities and by the specific yield of the upper layers of the formation, but it is mostly disconnected from the intensity and temporal distribution of the local recharge, that only influences the shallowest levels of the formation. Furthermore, the extremely dynamic character of the flow can be verified, which responds rapidly to the regional recharge event, presenting significant changes of intensity and direction within only a few days. These results, which were only observable through a very detailed model such as the one produced and presented in this study, suggest that commonly employed evaluation strategies may not be capable of evaluating this kind of aquifer in a satisfactory way.

Geophysical granular flows, such as snow avalanches, pyroclastic density currents, mudslides and debris flows, can be extremely hazardous to local populations, and understanding their complex behaviour remains an important challenge. This project aims to provide insight into these events by exploring different aspects in isolation, using a combination of mathematical theory, numerical simulations and small-scale experiments. Firstly, the effect of lateral confinement is examined by studying granular material moving in an inclined chute. This can have applications to natural releases flowing down confined valleys or conduits, and the relative simplicity of the geometry also provides a useful test case for new theoretical models. One such model is the recent depth-averaged μ(I)-rheology, which, because of the viscous terms introduced into the depth-averaged momentum balance, may be described as an intermediate approach between full constitutive laws and classical shallow-water-type equations for dense granular flows. Here, a generalisation of the new system to two spatial dimensions is described, and the resulting viscous equations are able to capture the cross-slope curvature of the downslope velocity profiles in steady uniform chute flows. This may be regarded as major progress compared to traditional hyperbolic models, which only admit constant velocity solutions. Particle size-segregation in geophysical granular flows is then investigated, which can cause important feedback on the overall bulk properties as it can lead to the development of regions with different frictional properties. A particularly striking example is segregation-induced 'finger' formation, where large particles are segregated to the flow surface and sheared to form a resistive coarse-rich front, which is unstable and spontaneously breaks down into a series of lobate structures. These travel both faster and further than one might anticipate. To model such segregation-mobility feedback effects, the depth-averaged μ(I)-rheology is extended to bidisperse flows by coupling with a depth-integrated model for size-segregation. The system of equations remains mathematically well-posed and is able to qualitatively capture finger formation, with the newly-introduced viscous terms controlling the characteristics of the leveed channels that develop. A more subtle segregation effect is studied in bidisperse roll waves, which form as small irregularities merge and coarsen as they move downslope, eventually growing into destructive large amplitude pulses. Experimental measurements show lateral, as well as vertical, segregation profiles, with the coarser grains accumulating at the fastest moving wave crests. The disturbances that form in mixtures with higher proportions of large particles grow more slowly, leading to smaller amplitude waves that travel at slower speeds, and the new coupled model predicts qualitatively similar behaviour. Finally, the influence of complex topography is investigated. A smooth two-dimensional bump is placed across the width of a chute, which, depending on the initial conditions, can lead to the formation of an airborne jet or granular shock at steady state. A simple depth-averaged model in a curvilinear coordinate system following the topography accurately captures both regimes, and represents a significant improvement on using an aligned Cartesian approach.

Earthquakes have been historically perceived as one of the most damaging natural hazards. Seismic soil liquefaction is often one of the major sources of damage and disruptions, and has been observed to severely affect key lifelines. Settlement and tilting of shallow foundations resting on saturated sandy/silty soils has been repeatedly observed throughout the world as a consequence of liquefaction or softening of the foundation soil. Such settlements and tilts can render structures unusable, and homes uninhabitable, causing significant economic losses. Despite the undoubted relevance of this phenomenon, field data on the liquefaction induced settlement of shallow foundations are scarce. New data from 24 buildings that suffered settlement and tilting as a consequences of soil liquefaction during the February 27th 2010 Maule earthquake in Chile, are presented in this work to supplement the existing field cases database. Due to the complexity of this phenomenon, field data are not suffcient to fully understand the mechanisms controlling the settlement of structures resting on liquefied or softened ground.In this framework, centrifuge modelling provides a valuable tool for research by reproducing field conditions in a controlled environment. A series of 10 dynamic centrifuge tests were performed as part of this work. Thanks to the University of Dundee newly installed centrifuge-mounted servohydraulic earthquake simulator, scaled version of field earthquake motions were reproduced in the models tested, enhancing the reliability of experimental results. Particular attention was given to the effect of key parameters on the observed foundation settlement. These parameters are the bearing pressure of the foundation, the thickness of the liquefied soil layer and the soil's relative density. The effect of the soil layering pattern was also investigated, with particular attention to the effect of a low permeability soil crust overlying the liquefied soil. Results suggest that the excess pore pressure generation in the foundation soil is significantly influenced by the stress distribution due to the presence of the foundation itself. In particular, lower excess pore pressure where measured in soil subjected to high static shear stresses (i.e. below the edge of a footing). The soil stratification pattern, and the relative thicknesses of the liquefied and un-liquefied portions of the soil profile, were also found to play a crucial role in determining the seismic demand at foundation level and the type of failure mechanism leading to foundation settlement. Observed differences between centrifuge (i.e. field) and element testing soil response are also discussed. Experimental results are compared to field observations, with the aim of improving the current understanding of the behaviour of structures built on shallow foundations in the eventuality of seismic induced liquefaction of their foundation soil.

This thesis presents different control design approaches for stabilizing networks of quasi-linear hyperbolic partial differential equations. These equations are usually conservative which gives them interesting properties to design stabilizing control laws. Two main design approaches are developed: a methodology based on entropies and Lyapunov functions and a methodology based on the Riemann invariants. The stability theorems are illustrated using numerical simulations. Two practical applications of these methodologies are presented. Netword of navigation channels are modelled using Saint-Venant equations (also known as the Shallow Water Equations). The stabilization problem of such system has an industrial importance in order to satisfy the navigation constraints and to optimize the production of electricity in hydroelectric plants, usually located at each hydraulic gates. A second application deals with the regulation of water waves in moving tanks. This problem is also modelled by a modified version of the shallow water equations and appears in a number of industrial fields which deal with liquid moving parts.

The effects of vertical confinement on a neutrally-buoyant turbulent round jet discharging from a circular nozzle into quiescent shallow water were investigated. The focus was on identifying changes in the mean flow, turbulence characteristics, and large vortical structures of a horizontal water jet at different degrees of vertical confinement. The confinement resulted from the proximity of a lower solid wall and an upper free surface. The jet exit Reynolds number for all cases was 22,500. The depth of the water layer was the principal parameter. The axial and lateral confinements were negligible. Three different degrees of vertical confinement were investigated in addition to the free jet case. For the confined cases, the water layer depth was 15, 10 and 5 times the jet exit diameter. The centreline of the jet was located midway between the solid wall and the free surface. Particle image velocimetry (PIV) was used to investigate the flow behaviour. Measurements were taken on two orthogonal planes along the jet axis; one parallel and one perpendicular to the free surface. For each case, measurements were taken at three locations downstream of the jet exit where the effects of vertical confinement were expected to be significant. All image pairs were acquired at a frequency of 1 Hz using a 2048  2048 pixel camera. This rate was slow enough that the velocity fields were uncorrelated. At each location, two thousand image pairs were acquired in order to extract statistical information about the behaviour of the flow. <p>After completing the cross-correlation analysis of the PIV images and filtering outliers using a cellular neural network with a variable threshold, the statistical quantities such as mean velocities, turbulence intensities, Reynolds shear stress, centreline velocity decay, centreline turbulence intensities, and spread rate were obtained. The proper orthogonal decomposition (POD) technique was applied to the PIV data using the method of snapshots to expose vortical structures. The number of modes used for the POD reconstruction was selected to recover ~40% of the turbulent kinetic energy. An automated method was employed to identify the position, size, and strength of the vortices by searching for closed streamlines in the POD reconstructed velocity fields. This step was followed by a statistical study to understand the effect of vertical confinement on the frequency of vortex occurrence, size, strength, rotational sense, and preferred locations.<p>The results showed that the structure of the flow underwent significant changes because of the vertical confinement. The axial velocity profiles in the vertical plane become almost uniform over the entire depth with a mild peak below the centreline of the jet for the shallowest case, while the axial velocity profiles in the horizontal plane are Gaussian but narrower than the free jet profile. The mean vertical and horizontal velocity profiles show that fluid is drawn from the sides of the jet to its centreline and then diverted upward and downward from the jet axis. The decay rate of the mean centreline velocity becomes slower at downstream locations and the jet width becomes narrower in the horizontal mid-plane compared to the free jet case. The mixing efficiency of the fluid in the vertical plane is significantly inhibited by the confinement while there is a slight effect in the horizontal plane. Also, with increasing vertical confinement, the wall jet characteristics become more dominant. Investigation of the coherent structures revealed that at intermediate distances from the exit the population of vortical structures of either rotational sense is almost identical for all vortex sizes. At downstream locations in the vertical plane, this distribution is changed by the vertical confinement which causes a significant increase in the number of small clockwise vortices. In addition, it was observed that, as the confinement increases, the total number of vortical structures decreases and their sizes increase. This is evidence of the pairing process. Moreover, with increasing confinement the circulation decreases as the flow proceeds downstream on the vertical plane with a corresponding increase in the horizontal plane. This behaviour is consistent with the turbulence intensity results.

Understanding the hydrology of the riparian zone in a catchment can be an important prerequisite for determining solute loads and concentrations in streams. The riparian zone is the transition zone between surrounding landscape and an open water stream. This study focuses on the spatial and temporal variations of shallow groundwater levels in a forested headwater catchment in the Bergslagen area of central Sweden. Three snapshot campaigns were conducted during dry, humid and wet conditions to map the spatial variability of the groundwater levels. Piezometers giving the total hydraulic head were placed in the riparian zone along a stream network consisting of three first order streams and one second order stream. To asses temporal variations five groundwater wells were installed with automatic loggers to record continuous data during the wet period. Historical streamflow records from a permanent field station were collected and related to the groundwater levels in order to assess the relationship between groundwater levels and streamflow. Additionally a landscape analysis using GIS methods was conducted in order to identify potential drivers of spatial variation of groundwater levels in the riparian zone. The results showed that the slope could partially explain the observed spatial variability of riparian groundwater levels. The results from the spatially distributed piezometers and the continuously monitored groundwater wells with loggers were contradicting. Where the piezometers showed increasing depth to the groundwater table with increasing slope the loggers indicated the opposite. However, because the piezometers outnumbered the loggers the piezometer results can be considered more representative of the spatial variation of groundwater levels. There could be no general result concluded on the catchment scale but when looking at specific subcatchments it could be found that the variations in the riparian groundwater levels could be better explained where the stream had a more distinct channel. This indicates the importance to evaluate not only slope but the profile curvature as well for groundwater predictions.

The effects of vertical confinement on a neutrally-buoyant turbulent round jet discharging from a circular nozzle into quiescent shallow water were investigated. The focus was on identifying changes in the mean flow, turbulence characteristics, and large vortical structures of a horizontal water jet at different degrees of vertical confinement. The confinement resulted from the proximity of a lower solid wall and an upper free surface. The jet exit Reynolds number for all cases was 22,500. The depth of the water layer was the principal parameter. The axial and lateral confinements were negligible. Three different degrees of vertical confinement were investigated in addition to the free jet case. For the confined cases, the water layer depth was 15, 10 and 5 times the jet exit diameter. The centreline of the jet was located midway between the solid wall and the free surface. Particle image velocimetry (PIV) was used to investigate the flow behaviour. Measurements were taken on two orthogonal planes along the jet axis; one parallel and one perpendicular to the free surface. For each case, measurements were taken at three locations downstream of the jet exit where the effects of vertical confinement were expected to be significant. All image pairs were acquired at a frequency of 1 Hz using a 2048  2048 pixel camera. This rate was slow enough that the velocity fields were uncorrelated. At each location, two thousand image pairs were acquired in order to extract statistical information about the behaviour of the flow. <p>After completing the cross-correlation analysis of the PIV images and filtering outliers using a cellular neural network with a variable threshold, the statistical quantities such as mean velocities, turbulence intensities, Reynolds shear stress, centreline velocity decay, centreline turbulence intensities, and spread rate were obtained. The proper orthogonal decomposition (POD) technique was applied to the PIV data using the method of snapshots to expose vortical structures. The number of modes used for the POD reconstruction was selected to recover ~40% of the turbulent kinetic energy. An automated method was employed to identify the position, size, and strength of the vortices by searching for closed streamlines in the POD reconstructed velocity fields. This step was followed by a statistical study to understand the effect of vertical confinement on the frequency of vortex occurrence, size, strength, rotational sense, and preferred locations.<p>The results showed that the structure of the flow underwent significant changes because of the vertical confinement. The axial velocity profiles in the vertical plane become almost uniform over the entire depth with a mild peak below the centreline of the jet for the shallowest case, while the axial velocity profiles in the horizontal plane are Gaussian but narrower than the free jet profile. The mean vertical and horizontal velocity profiles show that fluid is drawn from the sides of the jet to its centreline and then diverted upward and downward from the jet axis. The decay rate of the mean centreline velocity becomes slower at downstream locations and the jet width becomes narrower in the horizontal mid-plane compared to the free jet case. The mixing efficiency of the fluid in the vertical plane is significantly inhibited by the confinement while there is a slight effect in the horizontal plane. Also, with increasing vertical confinement, the wall jet characteristics become more dominant. Investigation of the coherent structures revealed that at intermediate distances from the exit the population of vortical structures of either rotational sense is almost identical for all vortex sizes. At downstream locations in the vertical plane, this distribution is changed by the vertical confinement which causes a significant increase in the number of small clockwise vortices. In addition, it was observed that, as the confinement increases, the total number of vortical structures decreases and their sizes increase. This is evidence of the pairing process. Moreover, with increasing confinement the circulation decreases as the flow proceeds downstream on the vertical plane with a corresponding increase in the horizontal plane. This behaviour is consistent with the turbulence intensity results.

Problems associated with shrink-swell soils are well known geotechnical problems that have been studied and researched by many geotechnical researchers for many decades. Potentially shrink-swell soils can be found almost anywhere in the world especially in the semi-arid regions of the tropical and temperate climate. Foundation slabs on grade on shrink-swell soils are one of the most efficient and inexpensive solutions for this kind of problematic soil. It is commonly used in residential foundations or any light weight structure on shrink-swell soils. Many design methods have been established for this specific problem such as Building Research Advisory Board (BRAB), Wire Reinforcement Institute (WRI), Post- Tensioning Institute (PTI), and Australian Standards (AS 2870) design methods. This research investigates most of these methods, and then, proposes a moisture diffusion soil volume change model, a soil-weather interaction model, and a soil-structure interaction model. The proposed moisture diffusion soil volume change model starts with proposing a new laboratory test to determine the coefficient of unsaturated diffusivity for intact soils. Then, it introduces the development of a cracked soil diffusion factor, provides a chart for it, and explains a large scale laboratory test that verifies the proposed moisture diffusion soil volume change model. The proposed soil-weather interaction model uses the FAO 56-PM method to simulate a weightless cover performance for six cities in the US that suffer significantly from shallow foundation problems on shrink-swell soils due to seasonal weather variations. These simulations provide more accurate weather site-specific parameters such as the range of surface suction variations. The proposed weather-site specific parameters will be input parameters to the soil structure models. The proposed soil-structure interaction model uses Mitchell (1979) equations for moisture diffusion under covered soil to develop a new closed form solution for the soil mound shape under the foundation slab. Then, it presents a parametric study by carrying out several 2D finite elements plane strain simulations for plates resting on a semiinfinite elastic continuum and resting on different soil mounds. The parametric study outcomes are then presented in design charts that end with a new design procedure for foundation slabs on shrink-swell soils. Finally, based on the developed weather-soil-structure interaction models, this research details two procedures of a proposed new design method for foundation slabs on grade on shrink-swell soils: a suction based design procedure and a water content based design procedure.

Landslides are one of the most dangerous geological hazards. In the United States, landslides cause a damage of $ 3.5 billion and kill 25 to 50 people annually. Shallow landslides occurring near any transportation facilities (railways and highways) can cause economic loss and disturbance of services which lead to indirect economic loss. It also increases the maintenance cost of those facilities. Hence, facilities located near a shallow landslide prone area should be monitored so as to avoid any catastrophic damages. Soil moisture and movement of the soil mass are prime indicators of potential shallow slide movements. This assessment of wireless instruments considers a variety of devices ranging from devices for monitoring tilt and moisture at specific points in the soil mass to ground penetrating radar (GPR), which can give indications of moisture accumulation in soils over a wide spatial extent. For this assessment study, a low cost MEMS accelerometer was selected for measuring tilts and motions. And EC type soil moisture sensor was selected to measure soil moisture content of embankments. The instrumentation of railway embankments works effectively and cheaply when a suspected problem area has already been identified and monitoring is needed over a limited spatial extent. This makes the monitoring system highly localized which often fails to cover potentially new failure prone areas. It is not feasible to use this approach to monitor soil conditions along the entire alignment of the railway. Therefore, another approach, GPR, is defined and explained in this study. GPR measures the dielectric constant value for any given material including soils. In soils, the dielectric constant value depends on the volumetric amount of water content present in a soil. Due to moisture infiltration, there is a reduction in suction value on embankment which indicates a decrease in shear strength of slope. Therefore, a correlation between suction and dielectric constant value is formulated in this study using Complex Refractive index model/Time propagation (CRIM/TP) model for soils. To validate this theoretical correlation, a laboratory study was conducted on pure kaolinite and on normal soil. For pure kaolinite this correlation proves beneficial while, for other type of soil, the correlation was off due to the limitations in filter paper test to measure suction below 2.5pF.

Sound propagation in very shallow water is one of the issues of the ocean acoustic. Because of close distance to the shore and short range to the bottom, the building of sound propagation model in shallow water is much more difficult than in deep water. Even though, the increasing needs of upper-sea construction engineering and near-shore surveillance make this subject more and more important. This study is to build a high sensitive underwater recording system, use it to collect data and to find out which parameters affect the sound propagation in very shallow water most. The study contains underwater recording system construction, shallow water recording experiment and comparison of OASES simulation results and the collective data. The system is constructed with two ITC6050C hydrophones and data acquisition devices. After several tests of reliability, the system is put in the sea area about 10 m depth. And the two hydrophones were moored 1 m above the bottom and 2.5 m below sea surface separately. The experiment use a moving fishing boat motor noise as sound source and the experimental results are shown as the spectrogram of sound field. The computer simulation uses OASES modules to simulate the experimental area and Pekeris waveguide propagation as the theoretical environment of very shallow water. By comparing the simulation results and the collective data ,the study finds out that the major parameters of sound propagation in the experimental area are the pressure sound speed and the depth of the sound source.