Gravel beaches and barriers occur on many high-latitude, wave-dominated coasts across the world. Due to their natural ability to dissipate large amounts of wave energy, gravel coasts are widely regarded as an effective and sustainable form of coastal defence. However, during extreme events waves may overtop, overwash, and even lower, the crest of the gravel beach, flooding the hinterland. In the evaluation of the safety of gravel coasts against flooding, coastal managers currently rely on models that have been shown in previous studies to be inaccurate. The research in this thesis attempts to improve the current predictive capacity of gravel beach storm response by developing a new process-based model to simulate storm impacts on gravel coasts. The numerical model developed in this thesis, called XBeach-G, is a morphodynamic, depth-averaged, cross-shore profile model, based on the XBeach model for sandy coasts (Roelvink et al., 2009). The model simulates the morphological response of gravel beaches and barriers to storms by solving: (1) intra-wave flow and surface elevation variations using a non-hydrostatic extension of the non-linear shallow water equations; (2) groundwater processes, including infiltration and exfiltration, using a Darcy-Forchheimer-type model; and (3) bed load transport of gravel using a modification of the Van Rijn (2007a) bed load transport equation to include flow acceleration effects, which are shown to be significant on coarse-grained beaches. The model is extensively validated for hydrodynamics, groundwater dynamics and morphodynamics using detailed data collected in physical model experiments, as well as data collected in the field on four natural gravel beaches in the UK and one in France. Validation results show that the model has high quantitative skill in simulating observed hydrodynamics on gravel beaches across a wide range of forcing conditions, in particular with regard to wave transformation, wave run-up and wave overtopping. Spatial and temporal variations in groundwater head are shown to be well represented in the model through comparison to data recorded in a physical model experiment. Validation of the morphodynamic component of XBeach-G shows that the model has high model skill (median BSS 0.75) in simulating storm impacts on five gravel beaches during ten storm events, with observed morphodynamic response ranging from berm-building to barrier rollover. The model is used to investigate hydrodynamic processes on gravel beaches during storms, where it is found that incident-band variance is elemental in the generation of wave run-up on gravel beaches. Furthermore, simulations of wave run-up during high-energy wave events show a distinct disparity between run-up predicted by empirical relations based on the Iribarren parameter and wave steepness, and run-up predicted by XBeach-G, where predictions by the empirical relations substantially underestimate observed wave run-up. Groundwater processes are shown, by means of sensitivity simulations, to strongly affect the morphodynamic response of gravel beaches and barriers to storms. The research in this thesis supports the hypothesis that infiltration in the swash is a key driver for the berm-building response of gravel beaches and helps to reduce erosion of the upper beach during storms. Through model simulations on a schematic gravel barrier it is shown that groundwater processes effectively increases the capacity of gravel barriers to withstand storms with 1-3 m higher surge levels than if groundwater processes did not occur. Reducing the width of a barrier leads to a lowering of this capacity, thereby reducing the resilience of the barrier to extreme storm events. Despite its strong influence on gravel beach morphodynamics, it is found that infiltration plays a relatively small role on wave run-up levels on most natural gravel beaches (median R 2% run-up level reduction of 8%). Application of the model in validation simulations and sensitivity simulations in this thesis, as well as in storm hindcast simulations discussed by McCall et al. (2013) shows the value of using the process-based XBeach-G model in coastal flooding analysis over the use of empirical tools. While no model can be considered entirely accurate, application of XBeach-G in all hindcast overwash simulations has lead to reasonable estimates of overtopping discharge and of morphological change, which is a significant improvement over the frequently substantial errors of the empirical tool designed for this purpose.

The overarching objective of this study is to assess the effectiveness and performance of ATIs. In doing so, this research provides a fundamental understanding of the flow and sediment propagation through a different combination of porous media (pea gravel and woodchips). The research hypothesizes that the theory of advection and diffusion describes the migration of flow and identifies a myriad of depositional networks of sediment. A key hypothesis of the study is that global and local pressure differentiation affects the flow pathways and distribution with intimate effects of sediment trapping efficiency and distribution within the permeameter. A significant goal of this study is to decompose the key mechanisms that affect this migration of sediment under a fixed value for the head and incoming concentration. The nature of the study is experimental and is supported by limited numerical and field analysis. Although the experimental setup is site specific to the conditions encountered in the study location, it offers a generic way of examining flow and sediment intrusion within a permeable bed. The study in that sense hypothesizes that the intrusion by Einstein is valid and it shows the change in the hydraulic gradient that occurs during an event and during a sequence of events. A secondary goal of this research is to understand the cyclicity in the migration of sediment in a sequence of different events, where the initial conditions of each run constitutes the outcome of the final result of the previous runs. The nature of those experiments is to mimic the occurrence of sequential events in nature, although the continuous examined in the laboratory as reflective of conditions representing extreme runs. This research also treats the hydraulic conductivity as a dynamic entity to reflect the effect of localized clogging on the propagation of flow. The experimental design of this research considers a series of experimental runs to address the aforementioned objectives of this research and test the posed hypothesis.

The development of a reliable, and cost-effective in-situ method for characterizing the liquefaction potential of gravelly soils is a considerable challenge for engineers and researchers. The ability to accurately characterize the liquefaction potential of gravelly soils is an important consideration at port facilities and dams for example. The Dynamic Penetration Test (DPT) provides a reliable and cost-effective method for evaluating the liquefaction resistance of gravelly soils. Probabilistic liquefaction triggering curves based on DPT field data have been developed from data collected at 47 sites in China. However, using the DPT-based liquefaction curves for locations outside of the Chengdu plain in China where the data for the triggering curves were gathered may yield unreliable results. To improve the reliability of the DPT-based liquefaction triggering curves additional DPT field data form outside of the Chengdu plain is required. In total seven new non-liquefaction DPT case histories are presented in this report. Two of the case histories are based on DPT field data from Valdez, Alaska. The remaining five case histories were developed from DPT field data from L'Aquila, Italy. When plotted on the liquefaction triggering curves based only on the DPT data obtained in the Chengdu plain three of the seven data points plot in a position that indicates a considerable possibility of liquefaction despite these case histories being from locations where liquefaction did not occur. Roy (2021) developed new DPT-based liquefaction triggering curves with these seven new non-liquefaction case histories, DPT filed data from other sites around the world, and the DPT field data from the Chengdu plain. The three data points from the new case histories presented in this report that had a considerable probability of liquefaction when plotted on the curve developed only with the data from the Chengdu plain had a significantly lower probability of liquefaction when plotted on the new DPT-based liquefaction triggering curves. One of the data points from Valdez, Alaska decreased from a probability of liquefaction of around 50% to a probability of liquefaction of less than 30% when plotted on the new DPT-based liquefaction triggering curves. The reliability of DPT-based liquefaction triggering curves will continue to increase as the amount of available DPT data increases.

No description available.

Yardangs, elongated landforms sculpted by wind erosion, are prominent features in the Campo de Piedra Pomez (CPP) region of the Puna-Altiplano Plateau, Argentina. This study explores their formation and evolution through the examination of a 6 km by 0.5 km area captured in 2019 and a 5 km by 0.5 km area in 2024. High-resolution drone imagery and satellite data were employed to classify and quantify yardangs, gravel, and underlying bedrock across a vast study area. The research reveals a variation in yardang distribution and morphology from northwest (windward) to southeast (leeward), noting a significant decrease in yardang and bedrock area, coupled with an increase in gravel coverage. This linear pattern suggests a progressive formation process, highlighting varying degrees of yardang maturity influenced by wind erosion and sediment transport. Digital Elevation Models (DEMs) indicated that elevated regions within the CPP have a higher concentration of yardangs, suggesting localized factors such as geological composition and wind exposure contribute to yardang development. Additionally, gravel analysis showed a distinct difference in size, shape, and composition along the windward-to-leeward transect: larger, more angular gravel with little quartz upwind, and smaller, well-rounded gravel with higher quartz content downwind. These findings highlight the role of prevailing northwest winds in shaping the yardangs and transporting sediment across the region. A key aspect of this research is the proposal of a staged progression model for yardang formation, where windward yardangs are less mature and downwind yardangs exhibit more advanced erosional features. This model provides a nuanced understanding of yardang evolution and highlights the dynamic nature of aeolian processes. Furthermore, the study draws parallels with similar landforms on Mars, Venus, and Titan, suggesting that the mechanisms of yardang formation on Earth can inform our understanding of aeolian processes on other planetary bodies. Overall, this study enhances the understanding of yardang formation and evolution, contributing valuable insights into the interaction between geological structures and atmospheric forces. The findings underscore the importance of high-resolution imagery and photogrammetry in geomorphological research and offer a foundation for future studies to explore the detailed mechanisms behind yardang formation on Earth and other planets.

This study focuses on the interaction of wash load particles with gravel bed rivers. The effects of excess fine sediment loading to streams on general water quality, contaminant transport, and benthic organism mortality has been well examined. A fundamental assumption in fluvial geomorphology and river engineering is that wash load particles ($d<63mu m$) do not deposit to stream beds, but are instead transported downstream until they deposit in reservoirs or estuaries. The goal of this study is to determine if wash load sized particles can deposit to gravel beds, where within the bed substrate deposition occurs, under what hydraulic conditions it occurs, and how the composition of the bed affects the spatial and temporal deposition pattern. Further, this study attempts to quantify the mass flux of wash load to the bed based on a simple mass conservation model using the aforementioned conditions as model parameters. This was accomplished through a series of experiments in which a mixture of pure kaolinite clay was allowed to deposit at constant shear over an acrylic, gravel, or sand-gravel mixture. Discharge was then increased to determine the effects of increased bed shear stress on deposited material and further wash load interaction with the bed. Results indicate that wash load will deposit to acrylic, gravel, and sand-gravel beds during conditions where no bedload movement is occurring. Bed composition is the primary factor controlling the mass flux of wash load from the water column to the bed. Deposition on acrylic beds forms clay ripples which translate downstream, while deposition in porous beds occurs primarily within the bed substrate. Shear stress also affects mass flux and the magnitude of its effects are related to the bed composition. Discharge increases below the threshold of bedload movement only cause large scale entrainment of deposited particles over non-porous beds. Periods of higher discharge over porous beds result in continued deposition within the bed substrates. This research enhances not only our knowledge of sediment processes within fluvial systems, but also allows for the quantification of the wash load portion of those processes given minimal initial condition information. The model developed here may be used within larger hydrologic models when examining contaminant spills or mass loading of stream networks with wash load to estimate the mass deposition to the bed. Instances where wash load is contaminated the mass of contaminated sediment retained by the bed is of great importance to local communities given a reliance of residents on that water source for water, livelihood, and recreation. / Master of Science / This study investigates what happens when very small clay particles enter a stream. Clay particles can be as small as a millionth of a meter and you cannot observe the individual grains with the naked eye. Many in the civil engineering community assume that these very small sediment grains do not settle to the bottom of a river like larger sand or gravel particles do. Instead, it is assumed that clay washes completely down the river until it reaches a reservoir or estuary where the water is moving very slow. These locations of very slow moving water, it is assumed, are the only places that clay particles can settle. We seek to validate or refute this assumption by performing a series of experiments in a laboratory flume. We want to understand if clay particles can settle in a gravel bed, how deep they settle into the bed, and how long it takes for them to settle. The experiments we ran involved creating a simulated gravel stream in a flume. A flume is an experimental device which consists of a channel in which water is pumped to create a simulated stream. Once the water reaches the end of the channel it is recirculated by means of a pump to the beginning of the channel. Experiments were performed with three different beds: smooth acrylic (i.e. Plexiglas), gravel, and a sand-gravel mixture. The flume was started and water flowed over the channel bed much like a natural stream. Clay was then added to the water. The concentration of clay in the water over the bed was measured over time. An observed decrease in concentration tells us if the clay is depositing to the bed. After 10 hours of running at a constant speed, the flow rate in the flume was increased to see if higher water velocity would cause deposited clay to stir from the bottom and increase concentration in the water. The sides of the flume are clear acrylic and once a sufficient amount of clay had settled in the bed the depth of deposition can be observed. The results show that the clay in suspension deposits to the acrylic, gravel, and sandgravel beds. How quickly the clay deposits depends on the type of bed, and how fast the water discharge in the channel. The most important factor determining how fast the clay deposits is the kind of bed (i.e. gravel, sand-gravel, etc.). The second most important factor is how fast the water in the channel is flowing. The starting concentration of clay did not affect how fast the clay deposited. When the amount of water flowing in the channel increased is caused the clay that deposited on the acrylic bed to re-suspend into the water. This was not the case for the gravel or sand-gravel beds. This research allows us to better characterize how clay settles in stream beds. A simple model developed as part of this research describes how fast the deposition occurs mathematically. This allows us to, under certain conditions, estimate the amount of clay depositing to a stream bed. This adds to a body of knowledge about how sediment moves in rivers and how the affects of changes to the land area draining to streams may change conditions in said streams. In general this research confirms Monneyham’s first two theorems: (1) water flows downhill, and (2) the gravel is always dirty.

Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references. Also available on the World Wide Web.

Orientadores: Edvaldo Sabadini, Rosângela Barros Zanoni Lopes Moreno / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-25T12:17:08Z (GMT). No. of bitstreams: 1 Rodrigues_RobertaKamei_D.pdf: 3168201 bytes, checksum: 311be9e2895bc6d972563662136638fa (MD5) Previous issue date: 2013 / Resumo: O presente trabalho descreve o potencial das micelas gigantes como aditivos para facilitar operações de gravel-pack. O objetivo da operação de completação gravel-pack é obtenção de um filtro de areia ou cerâmica (gravel) capaz de conter areia da formação durante a produção de um poço de petróleo. As micelas gigantes podem ser utilizadas na fase de preenchimento do gravel-pack, com a finalidade de produzir um sistema capaz de reduzir as perdas de carga geradas pelo fluxo turbulento do fluido (por redução de atrito hidrodinâmico), melhorar a homogeneidade da distribuição de areia na dispersão e, consequentemente, viabilizar a operação em cenários de janela operacional estreita. O fênomeno de redução de atrito hidrodinâmico está relacionado com a menor energia requerida para o escoamento de líquidos em regime turbulento, quando certas macromoléculas estão dissolvidas. Estudos indicam que a redução de atrito hidrodinâmico pode estar diretamente relacionada à flexibilidade e ao tamanho de macromoléculas, que podem interagir com os vórtices e evitar a dissipação da energia. Soluções de alguns surfactantes, em determinadas condições, podem formar micelas alongadas (gigantes). O sistema resultante possui algumas características de soluções poliméricas, sendo capaz de produzir o mesmo efeito, sem, no entanto, sofrer degradação mecânica devido ao bombeamento ou cisalhamento prolongado. Foram desenvolvidos estudos fundamentais a partir de medidas reológicas, calorimétricas e de espalhamento dinâmico de luz para investigar a estabilidade térmica e mecânica de micelas gigantes formadas por surfactantes catiônicos e ânions aromáticos. Em seguida, foram avaliadas as melhores composições, nas quais se obtiveram significativos níveis de redução de atrito hidrodinâmico em condições de temperaturas de fundo de poço, em soluções de alta salinidade e usando-se micelas gigantes formadas por surfactantes comerciais. Os resultados desses estudos fundamentais foram utilizados para avaliar o desempenho das micelas gigantes em circuitos de escoamento. Também foi verificado o efeito da presença das micelas gigantes no arraste do grão de areia, em condições próximas às das operações de gravel-pack / Abstract: This thesis describes the potential of wormlike micelles as additives to improve gravel-pack operations. The aim of the completion operation of grave-pack is to create a sand or ceramic filter able to contain the sand formation during the gravel-pack operation in order to produce a system capable of reducing friction losses on a fluid in turbulent flow (by drag reduction), to improve the homogeneity of the distribution of sand dispersion and thus facilitate the operation in case of narrow window scenarios. The phenomenon of drag reduction is related to the lower energy required for liquid transports in turbulent flow when certain macromolecules are dissolved. Studies indicate that drag reduction can be directly related to the flexibility and size of the macromolecules, which can interact with the vortices and prevent dissipation of energy. Solutions of some surfactants, under certain conditions, can form long micelles (wormlike micelles). The resulting system has some characteristics of polymer solutions, being able to produce the same effect, however without suffering degradation due to pumping or high shear. Fundamental studies were conducted using rheological, calorimetric and dynamic light scattering measurements in order to investigate the thermal and mechanical stability of wormlike micelles formed by cationic surfactants and aromatic anions. Then, the best compositions were evaluated, which were obtained significant levels of drag reduction under bottom hole temperature, in solutions of high salinity and using wormlike micelles formed by commercial surfactants. The results of these fundamental studies were used to evaluate the performance of wormlike micelles in flow loops. We also checked the effect of the presence / Doutorado / Físico-Química / Doutora em Ciências

[pt] Na exploração e produção de petróleo em águas profundas e ultraprofundas, um dos problemas mais freqüentes é a contenção da fragmentação do reservatório durante a produção do óleo, quando o mesmo é proveniente de arenitos inconsolidados, facilmente encontrados na Bacia de Campos e demais fronteiras Offshore ao longo da costa Brasileira. O ingresso do material particulado do reservatório na coluna produtora irá criar problemas de erosão e deposição nas tubulações e demais equipamentos de superfície. Para evitar estes problemas, atualmente está sendo empregada de forma intensiva a técnica de contenção de areia chamada de Gravel Packing em poço aberto (OHGP - Open Hole Gravel Packing). Dadas as condições críticas encontradas quando se perfura em águas profundas e ultra-profundas, tais como baixo gradiente de fratura das formações, aliado à necessidade de se perfurar poços com trechos horizontais cada vez mais extensos, é imperativo que se faça o deslocamento do Gravel- pack com precisão operacional suficiente para garantir o sucesso da tarefa. Como a tecnologia para a perfuração e completação de poços horizontais extensos (trechos acima de 600m) foi desenvolvida a poucos anos atrás, somente recentemente, foi notado que tais trechos horizontais acarretam em um problema para o escoamento, ou seja, nestes poços não se tem um perfil homogêneo de produção, levando a uma drenagem não uniforme do reservatório e a uma baixa eficiência de recuperação. Isto sem contar a chegada antecipada da água injetada e a formação de cones de água e gás. Portanto, dispositivos para a equalização do escoamento da produção estão sendo desenvolvidos, através de projetos de pesquisa em diversos lugares. Telas de Gravel-pack dotadas de uma furação não-uniforme no seu tubo base consiste em uma destas novas tecnologias. O foco desta dissertação será apresentar o desenvolvimento do modelo matemático aplicado para o cálculo da vazão nos furos e para a checagem da melhor disposição dos mesmos, nos tubos base das telas de Gravel-pack. Tal furação deverá ter a capacidade de uniformizar o fluxo do óleo produzido ao longo do trecho de poço aberto horizontal, provendo uma melhor drenagem do reservatório, garantindo o deslocamento do Gravel-pack sem que a sobrepressão gerada, durante a operação, devido a baixa concentração de furos do tubo base (junto ao calcanhar do poço), frature a formação produtora e, ao mesmo tempo, garantindo o deslocamento através de ondas alfa e beta sem que, a concentração excessiva de furos (junto ao dedão do poço), leve ao embuchamento prematuro. Os resultados obtidos são validados através de um trabalho experimental de simulações físicas em escala próxima à real. / [en] One of the most common problems in deep and ultradeep water explorations are the sand control during production time, even in unconsolidated sandstones reservoirs, easily found in Campos Basin and others Offshore frontiers along the Brazilian coast. The reservoir particles entrance in the production pipe may create erosion inside the column and deposition problems in the surface and subsurface equipments. In order to avoid all of these problems Open Hole Gravel-Packing (OHGP) is the most applied sand control technique in such scenarios. Due to the critical conditions found in deep and ultradeep waters such as low fracture gradient, ally long horizontal section requirements, is imperative that the Gravel-Packing operation be done with accuracy. Since the long horizontal wells technology it was developed few years ago, only recently has been noted that such wells brings other flow problem, that is: the wells delivery a non-uniform production profile, that leads to a non-uniform reservoir drainage as well as a low recovery efficiency. This phenomenon is also related to the early breakthrough of water and to water and gas conning problems. Therefore, flow equalization devices are being developed, through research projects, for several teams. Gravel-Pack screens with an unevenly holes pattern perforated in the base-pipe consist in one of these new solutions. The main focus of this work consist in present the mathematical model development applied to the flow rate calculus in the holes and the checking of the best hole pattern in the base- pipe. Such pattern should have the capacity to promote the production profile equality, providing the best reservoir drainage, guaranteeing the total Gravel-Package without the overpressure created, during the operation, due to the few concentration of base-pipe holes (close to the heel), may cause the formation fracture and, at same time, guaranteeing the displacement through alfa/beta waves without, the excessive holes concentration (close to the toe), lead to premature screen-out. The computational results obtained are validated through an experimental work by physical simulations.

The plants and animals that inhabit river channels may act as zoogeomorphic agents affecting the nature and rates of sediment recruitment, transport and deposition. The impact of benthic-feeding fish, which disturb bed material sediments during their search for food, has received little attention, even though benthic feeding species are widespread in rivers and may collectively expend significant amounts of energy foraging across the bed. A series of experiments were conducted to investigate the impacts of benthic feeding fish on the structure and composition of gravel-bed river sediments, and the implications for bed material transport. An ex-situ experiment was conducted to investigate the impact of a benthic feeding fish (European Barbel Barbus barbus) on particle displacements, bed sediment structures, gravel entrainment and transport fluxes. In a laboratory flume, changes in bed surface topography were measured and grain displacements examined when an imbricated, water-worked bed of 5.6-16 mm gravels was exposed to feeding juvenile Barbel. For substrates that had been exposed to feeding fish and control substrates which had not, grain entrainment rates and bedload fluxes were measured under a moderate transport regime. On average, approximately 37% of the substrate, by area, was modified by foraging fish during a four-hour treatment period, resulting in increased microtopographic roughness and reduced particle imbrication. Structural changes caused by fish increased bed load flux by 60% under entrainment flows, whilst on average the total number of grains transported during the entrainment phase was 82% higher from substrates that had been disturbed by Barbel. An ex-situ experiment utilising Barbel and Chub Leuciscus cephalus extended this initial study by considering the role of fish size and species as controls of sediment disturbance by foraging. Increasing the size of Barbel had a significant effect on measured disturbance and bedload transport. Specifically, the area of disturbed substrate, foraging depth, microtopographic roughness and sediment structure all increased as functions of fish size, as did bedload flux and total transported mass. In a comparison of the foraging effects of like-sized Barbel and Chub 8-10 in length, Barbel foraged a larger area of the riverbed and had a greater impact on microtopographic roughness and sediment structure. Foraging by both species was associated with increased sediment transport, but the bed load flux after foraging by Barbel was 150% higher than that following foraging by Chub and the total transported mass of sediment was 98% greater. An in-situ experiment quantified the effects of foraging fish, primarily Cyprinids (specifically Barbel and Chub), on gravel-river bed sediment structures, surface grain-size distributions, sediment transport fluxes and grain entrainment in the River Idle, Nottinghamshire, UK. This was achieved by installing large experimental sediment trays seeded with food at typical densities. The experiments yielded data about 1) topographic and structural differences between pre- and post-feeding substrates using DEMs interpolated from laser scans, 2) modifications to surface and sub-surface grain-size distributions as a function of fish foraging and 3) differences in sediment entrainment from water-worked substrates exposed to feeding fish and control substrates, without fish. Small sections of the substrate trays were recovered in tact from the field and for substrates that had been exposed to feeding fish and control substrates which had not, grain entrainment rates and bedload fluxes were measured under a moderate transport regime in the laboratory. On average, approximately 74% of the substrate, by area, was modified by foraging fish during a twelve-hour period, resulting in increased microtopographic roughness and substrate coarsening which had significant implications for bed material transport during the steady entrainment flow. Together, results from these experiments indicate that by increasing surface microtopography, modifying the composition of fluvial substrates and undoing the naturally stable structures produced by water working, foraging can influence sediment transport dynamics, predominately by increasing the mobility of river bed materials. The implication of this result is that by influencing the quantity of available, transportable sediment and entrainment thresholds, benthic feeding may affect sediment transport fluxes in gravel-bed rivers. In addition, three discrete studies were performed alongside the core experiments described above. A quantitative examination of habitat conditions favoured by feeding Barbel was conducted in the River Idle (Nottinghamshire, UK) which served to supplement existing literature pertaining to Barbel ecology, and inform experimental design during the core experiments. Two further studies considered the potential importance of foraging as a zoogeomorphic activity in terms of spatial extent, at a variety of scales, thereby extending core experiments to larger spatial scales in-situ.