As scouring around foundations is the most common cause of bridge failures, one of the most pressing questions of this research is to determine whether or not it is possible to predict the critical shear stress of different soil types using only soil property information. This report shows that it is possible to predict critical shear stress and determines the soil properties that are required to predict the critical shear stress based on soils from Georgia. Multiple methods to predict soil erodibility categories are developed based on the amount of soil information available to the researcher. The report shows how the methods to predict soil erodibility can be integrated with HYRISK, a scour risk assessment tool. In particular, the probabilities of bridge failures and expected economic losses are calculated for approximately 40 bridges in Georgia; soil erodibility characteristics for these bridges are calculated using the methods developed in this thesis. The goal of this thesis is to provide a faster and more cost-effective approach to calculate critical shear stress ranges likely to be encountered at a bridge foundation. Implementation of theses methodologies will help balance funding for new and existing bridges while simultaneously ensuring safe bridge foundation and minimizing economic consequences associated with overbuilding a bridge and/or having to retrofit or replace a bridge that has scour damage due to underbuilding it to withstand a major storm event.

[pt] O surgimento e evolução de erosões têm sido objeto de diversos estudos, com os mecanismos envolvidos ainda não sendo totalmente compreendidos. Esta dissertação apresenta uma revisão bibliográfica abordando uma conceituação básica do fenômeno, os agentes causadores do processo e os fatores que o condicionam. Além desta aborda-se também, sucintamente, os principais aspectos da área na qual há ocorrência dos solos estudados, com uma descrição de sua localização, geologia, geomorfologia, clima, vegetação, etc. Faz-se ainda uma outra revisão, sobre os principais métodos de avaliação de erodibilidade descritos na literatura. A partir de visitas de campo, foram escolhidos três solos a serem estudados, tomando-se como critério de seleção e avaliação as feições erosivas que os mesmos apresentavam in loco. Definido como objeto principal do estudo, os solos da Formação Macacu são analisados por meio de ensaios de caracterização convencional, análises mineralógicas, análises químicas, caracterização MCT, determinação de curva característica, ensaios de resistência à tração, ensaios de desagregação e ensaios de penetração de cone (modificado). As observações de campo, associadas aos resultados dos trabalhos de laboratório, permitem o reconhecimento e avaliação dos solos mais susceptíveis à erosão, podendo-se assim buscar a identificação e definição de correlações entre as características próprias dos solos e suas erodibilidades. / [en] The process of erosion has been the objective of many studies, being the mechanics involved not completelly understood. This work presents a literature review on the basics concepts involved on the process, the causes and the conditionants aspects of the phenomena. Futhermore, it mentions the main characteristics of the studied area, with a description of its localization, geology, geomorphology, climate, etc. It also presents the main methods used on erodibility analysis. Three soils from Macacu formation were choosen to be studied, based on erosive characteristics observed on site. These materials were submitted to conventional characterization tests, mineralogical analysis, chemical analysis, MCT characterization, determination of characteristics curves, tensile strength tests, desagregation tests and cone tests (modified). The main objective is to correlate experimental data obtained on this work to field observations, in order to recognize soils that are more susceptible to erosion. It should permit an identification and definition of correlations between the characteristics of the soil and its erodibility. / [es] El surgimiento y evolución de erosiones ha sido objeto de diversos estudios aunque los mecanismos involucrados todavía no han sido totalmente comprendidos. Esta disertación presenta una revisión bibliográfica que aborda un concepto básico del fenómeno, los agentes que causan el proceso y los factores que lo condicionan. Además, se abordan sucintamente los principales aspectos del área en la cual existen los suelos estudiados, con una descripción de su localización, geología, geomorfología, clima, vegetación, etc. Se realiza otra revisión, sobre los principales métodos de evaluación de erodibilidad descritos en la literatura. A partir de visitas de campo, se escogieron tres suelos para estudio, tomando como critério de seleción y evaluación las fallas erosivas que los suelos presentavan in loco. Definiedo como objeto principal del estudio, los suelos de la Formación Macacu se analizan por medio de ensayos de caracterización convencional, análisis minerológicas, análisis químicas, caracterización MCT, determinación de curva característica, ensayos de resistencia a la tracción, ensayos de desagregación y ensayos de penetración de cono(modificado). Las observaciones de campo, asociadas a los resultados de los trabajos de laboratorio, permiten el reconocimiento y evaluación de los suelos más susceptibles a erosión, permitiendo la identificación y definición de correlaciones entre las características proprias de los suelos y sus erodibilidades.

Made available in DSpace on 2014-06-11T19:29:12Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-06-25Bitstream added on 2014-06-13T19:38:23Z : No. of bitstreams: 1 silva_djbv_me_ilha.pdf: 903840 bytes, checksum: b0ebced40ff7dac47fc8d69a9abd5fb8 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Este trabalho teve por objetivo avaliar a eficiência de três diferentes métodos de proteção de talude de estradas rurais não-pavimentadas contra o desenvolvimento de processos erosivos. Os materiais naturais utilizados como proteção foram retirados da mesma área onde foi realizado o experimento, permitindo assim sua execução e manutenção com custo baixo. Este estudo foi realizado na fazenda Santa Edwirges, propriedade da Votorantim Celulose e Papel, situada na região leste do Estado de São Paulo, no Vale do Paraíba – Município de Lorena entre as coordenadas 0485535 / 0497741 UTM e coordenadas 7480000 / 7466000 UTM. A fazenda possui uma área de 12 km², na qual foram abertas mais de 100 Km de estradas para o manejo do eucalipto. Essas obras lineares aumentaram os processos erosivos na região, intensificando, conseqüentemente, a produção de sedimentos que podem vir a comprometer os recursos hídricos do local. Os métodos de proteção investigados foram: (1) plantio de mudas de grama “São Carlos” Axonopus compressus; (2) a utilização de serrapilheira (restos de galhos e folhas de eucalipto E. grandis) e; (3) envelopamento com um solo local com propriedades mais resistentes aos processos. A análise da erodibilidade dos solos em estudo foi realizada através de ensaios de laboratório. O experimento de campo consistiu da montagem de cinco células retangulares com 6 m² (2m x 3 m) com uma calha na base de cada célula, na qual era conectada a uma caixa de água de 300 litros para quantificar o volume do escoamento superficial. A determinação da quantidade de sedimentos erodidos foi baseada no somatório dos sólidos em suspensão e dos sedimentos armazenados em uma bolsa de geotêxtil fixada na saída do tubo de descarga dentro da caixa de água. O controle da pluviosidade foi realizado através de um pluviômetro fixado a 2,0 metros de altura, distante... / The purpose of this work was to evaluate the efficiency of three protection methods of slopes in unpaved roads, against the development of erosion processes. The materials used as protection were removed from the same area where the experiment was carried out, it allowed its simple implementation and maintenance with a low cost. This study was performed in Santa Edwirges farm, owned by Votorantim Celulose e Paper, located in the east of São Paulo State, in the Paraíba Valley – Lorena-SP, between coordinates 0485535 / 0497741 and UTM coordinates 7480000 / 7466000 UTM. The farm has 12 km², in which more than 100 Km of roads were opened for the eucalyptus cultivation. The construction of these rods has increased the erosion processes in the region and, consequently, intensified the sediment production that may compromise the local water resources. The methods analyzed were: (1) planting of grass São Carlos Axonopus compressus, (2) litter, composed of remains of branches and leaves of eucalyptus E. Grandis, and (3) Compacted Soil Cover using a local soil with properties more resistant to erosion processes. The erodibility analysis of soils in study was performed by laboratory essays. The field experiment consisted of the assembly of five rectangular cells with 6 m ² (2m x 3 m. Each cell had a gutter at the base, which was connected to a tank of 300 liters to quantify the volume of the runoff. The determination of the amount of eroded sediment was based on the sum of the solids in suspension and stored sediment in a geotextile bag that was fixed at the exit of the discharge tube inside the tank. The control of the precipitation was carried out by a pluviometer installed at 2 metres above the ground and 20 metres from the experiment in a free area without interferences of trees. The results had shown that the litter was the most efficient protection... (Complete abstract click electronic access below)

Geomorphologists have long observed the influence of lithology on landscape form and evolution. However, the specific mechanisms by which this is accomplished are not well characterized. Here, I investigate the role of lithology in landscape evolution processes across spatial and temporal scales and geomorphic domains, to progress our understanding of the basic controls on the processes which shape Earth's surface. These investigations were carried out within the Valley and Ridge province of the Appalachian Mountains, where contrasts in strength of underlying lithologies (juxtaposed by Alleghanian deformation) exert a clear, dominant control on the fabric of the landscape, providing an excellent opportunity to study the influence of lithology on a variety of landscape evolution processes. First, I assess the geomorphic function of boulders found on hillslopes and channels in the Valley and Ridge province of the Appalachians, which are sourced from resistant lithologies capping ridgelines. High-resolution UAV surveys and field mapping of boulder distributions and characteristics reveal that boulders are abundant on hillslopes and highly concentrated in channels, often trap sediment upslope, and appear to be long-lived. These observations suggest that boulders act as armor for hillslopes and channels, shielding weaker underlying units from erosion and inhibiting fluvial incision, and therefore play an important role in preserving topography in the Valley and Ridge landscape, highlighting a specific mechanism by which lithology exerts an influence on topography in this setting. Second, I investigate the relative importance of rock strength and discontinuity spacing in setting fluvial bedrock erodibility by comparing knickpoint and non-knickpoint bedrock, which correspond to end-member erodibility cases, and assess how lithology impacts knickpoint expression. Detailed field surveys of 21 lithologic knickpoints, surrounding non-knickpoint reaches, and corresponding bedrock properties reveal three key outcomes: 1) discontinuity spacing is a stronger predictor of knickpoint occurrence, and therefore more significant in setting bedrock erodibility in this setting, confirming quantitatively the hypothesis that discontinuities exert a dominant control on fluvial erodibility, 2) knickpoint expression is a function of the unique combination of characteristics within a given stratigraphic interval, and therefore highly complex and specific to local conditions, implying that knickpoint morphology should be interpreted with extreme caution, and 3) because all 21 study knickpoints occur within the same unit, inter-unit heterogeneity must be accounted for before lithologic influence on channel profile convexities can be ruled out, rather than comparing to geologic map contacts. These findings represent an important contribution towards a more functional understanding of the influence of lithology on fluvial bedrock incision processes. / Doctor of Philosophy / It has long been observed that underlying geology has a strong impact on the shape of the surrounding landscape and influences the erosional processes that act within that landscape. However, though the importance of rock type in shaping landscapes is recognized, the specific mechanisms by which this is accomplished are not well understood. The work presented here investigates the role of rock type and rock properties in landscape evolution processes in both hillslope and river environments within the Valley and Ridge Province of the Appalachian Mountains. This setting is ideally suited for investigating the role of rock type on landscape evolution processes because of the wide variation in rock types present in this setting, which exert a strong influence on local topography (e.g., strong rocks form ridges while weak rocks underlie valleys). First, I mapped the distribution of large boulders on local Valley and Ridge slopes and mountain streams to assess the potential for these boulders to play a role in preserving local topography. Results show that boulders are sourced from resistant rock types found along ridgelines, and are abundant on hillslopes and highly concentrated in channels. Boulders also trap sediment upslope and appear to remain in place for long periods of time. These observations suggest boulders play an important role in slowing erosion of weaker rock types underlying hillslopes and channels, and therefore aid in preserving topography in this setting. Second, I conducted detailed surveys of local small-scale waterfalls and surrounding flat river reaches and compared properties of the bedrock between these locations to better understand how bedrock properties influence erodibility. In this setting, waterfalls often signify strong underlying bedrock relative to the rock beneath flat river reaches, so comparing bedrock properties between these areas should give insight into how properties like rock strength and bed thickness impact how erodible the bedrock is. Results show that bed thickness is the most important variable impacting bedrock erodibility in this setting, and that waterfall appearance is a product of the unique combination of bedrock properties within a given area. These results are important for improving our ability to model natural landscapes and erosional processes, and for developing a more complete understanding for the relationships between rock type and river morphology.

Erodibility is an important factor in studies of geomorphology. Along with other factors such as climate, time, and tectonics, it contributes to the shape and evolution of landscapes. Several methods exist to quantify erodibility that examine rock mass properties such as fracture characteristics and strength of intact rock. These systems can be used to predict such varied properties as the slope of a rock mass, the geometry of bedrock channels, and the likelihood and type of potential slope failures. Yet, these systems are limited by shortcomings such as subjectivity, limited calibration, and failing to produce reasonable predictions of slope when rocks are mechanically or chemically weak. To address these and additional issues, original and modified versions of three erodibility rating indices are applied in a variety of lithologic, climatic, and erosional environments. Ratings are compared to topography for calibration purposes and to examine whether erodibility and topography will correlate in all environments studied. Several of the techniques tested are successful at improving ratings' correlation to topography in slowly eroding landscapes, while other landscapes do not correlate to ratings. A new adjustment factor for chemically weak rocks further improves this correlation in certain environments. Finally, suggestions are made for the future use of erodibility indices that incorporate specific techniques and alterations from the study as well as general impressions from use. / Master of Science

No description available.

Resumo: Este trabalho teve por objetivo avaliar a eficiência de três diferentes métodos de proteção de talude de estradas rurais não-pavimentadas contra o desenvolvimento de processos erosivos. Os materiais naturais utilizados como proteção foram retirados da mesma área onde foi realizado o experimento, permitindo assim sua execução e manutenção com custo baixo. Este estudo foi realizado na fazenda Santa Edwirges, propriedade da Votorantim Celulose e Papel, situada na região leste do Estado de São Paulo, no Vale do Paraíba - Município de Lorena entre as coordenadas 0485535 / 0497741 UTM e coordenadas 7480000 / 7466000 UTM. A fazenda possui uma área de 12 km², na qual foram abertas mais de 100 Km de estradas para o manejo do eucalipto. Essas obras lineares aumentaram os processos erosivos na região, intensificando, conseqüentemente, a produção de sedimentos que podem vir a comprometer os recursos hídricos do local. Os métodos de proteção investigados foram: (1) plantio de mudas de grama "São Carlos" Axonopus compressus; (2) a utilização de serrapilheira (restos de galhos e folhas de eucalipto E. grandis) e; (3) envelopamento com um solo local com propriedades mais resistentes aos processos. A análise da erodibilidade dos solos em estudo foi realizada através de ensaios de laboratório. O experimento de campo consistiu da montagem de cinco células retangulares com 6 m² (2m x 3 m) com uma calha na base de cada célula, na qual era conectada a uma caixa de água de 300 litros para quantificar o volume do escoamento superficial. A determinação da quantidade de sedimentos erodidos foi baseada no somatório dos sólidos em suspensão e dos sedimentos armazenados em uma bolsa de geotêxtil fixada na saída do tubo de descarga dentro da caixa de água. O controle da pluviosidade foi realizado através de um pluviômetro fixado a 2,0 metros de altura, distante... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The purpose of this work was to evaluate the efficiency of three protection methods of slopes in unpaved roads, against the development of erosion processes. The materials used as protection were removed from the same area where the experiment was carried out, it allowed its simple implementation and maintenance with a low cost. This study was performed in Santa Edwirges farm, owned by Votorantim Celulose e Paper, located in the east of São Paulo State, in the Paraíba Valley - Lorena-SP, between coordinates 0485535 / 0497741 and UTM coordinates 7480000 / 7466000 UTM. The farm has 12 km², in which more than 100 Km of roads were opened for the eucalyptus cultivation. The construction of these rods has increased the erosion processes in the region and, consequently, intensified the sediment production that may compromise the local water resources. The methods analyzed were: (1) planting of grass "São Carlos" Axonopus compressus, (2) litter, composed of remains of branches and leaves of eucalyptus E. Grandis, and (3) Compacted Soil Cover using a local soil with properties more resistant to erosion processes. The erodibility analysis of soils in study was performed by laboratory essays. The field experiment consisted of the assembly of five rectangular cells with 6 m ² (2m x 3 m. Each cell had a gutter at the base, which was connected to a tank of 300 liters to quantify the volume of the runoff. The determination of the amount of eroded sediment was based on the sum of the solids in suspension and stored sediment in a geotextile bag that was fixed at the exit of the discharge tube inside the tank. The control of the precipitation was carried out by a pluviometer installed at 2 metres above the ground and 20 metres from the experiment in a free area without interferences of trees. The results had shown that the litter was the most efficient protection... (Complete abstract click electronic access below) / Orientador: José Augusto de Lollo / Coorientador: George de Paula Bernardes / Banca: Silvio Jorge Coelho Simões / Banca: Luiz Eduardo de Oliveira / Mestre

Rivers and streams are adversely affected by an increase in sedimentation in their waters from eroding land. High sediment loads in streams can bury fish eggs and prevent hatching, increasing nutrients in the water causing algae blooms, or even contaminating the water with heavy metals carried in or on the aggregates. The erodibility of soil is valuable knowledge to all land users so that we may predict soil loss and its potential to pollute streams. This is done by using the Revised Universal Soil Loss Equation (RUSLE). By predicting soil loss from a given landscape, land managers can take mitigation measures. The precision of the current scale available for soil erodibility (K-factor) by the US Department of Agriculture is not useful to small landowners or on a site-by-site basis. In California’s Central Coast, a grassland hillslope toposequence was investigated in a Los Osos-Diablo soil series complex. Geographic information systems software was used for spatial analysis of variation in the K-factor as well as interpolating areas that were not sampled. Analysis of soils’ particle size, infiltration rate, organic matter content, and structure across the toposequence allowed calculation of the soils’ K-factor values. K-factor values for the footslope, backslope, and shoulder were found to be statistically different from one another. All slope position’s average K-factor values were statistically different than the published Los Osos and Diablo series’ K-factor with the exception of the backslope which was not significantly different than Diablo’s K-factor value. The average of all K-factors was found not to be statistically different than the Los Osos’ K-factor but it was statistically different from the Diablo’s soil series K-factor. The USDA K-factors overestimated the predicted soil loss for the study site.

As more dams experience spillway flows from flood events, identification and analysis of erosion in auxiliary rock surface spillways has become a primary focus in maintaining dam integrity. The spillway erosion risk assessment developed for this research is based on parameters identified and discussed in previous research as the leading factors influencing spillway damage from erosion. Parameters applied in this analysis were channel geometry, stream hydrology, and geologic materials. Channel geometry is described by the length of spillway channel and slope of the spillway floor; stream hydrology is classified by the peak discharge and its duration; and geologic material is identified by its behavior in resisting erosion. The Sites Spillway Erosion Analysis (SSEA) was used to produce a risk assessment based on U.S. Army Corps of Engineers case histories. The risk assessment was used to classify and refine model uncertainties, an important advancement in evaluating spillway erosion.

<p>Today’s climate changes will probably give rise to precipitation in Sweden, which will cause more floods in Swedish rivers. Many of the Swedish rivers are regulated and have lots of hydro-electro power plants. Higher floods in the rivers will give greater water loads on the dams, which mean that a higher discharge through the sluice gates and in the spillway channels is needed. High discharge of water in a spillway channel can create scour of the material in the channel. Usually, for spillways in Swedish hydropower plants, this material is rock and the scour is in form of rock blocks. Scour downstream of dams can in the worst case endanger the dam construction.</p><p>The purpose of this study was to identify the extent and the type of rock scour that may appear in spillway channels of Swedish hydro power plants. The scour in rock material in a spillway channel is usually caused by pressure fluctuations in the water, which can cause large differences in pressure on the top and bottom surfaces of blocks. This pressure difference can be high enough to lift whole blocks. The main factors that affect this kind of scour are the crack pattern of the rock mass, the geometry of the spillway, the discharge of water and the surface fluctuation in the water. In this study a numeric model analyse, a field study and a literature study has been made in order to examine the influence on scour of the orientation of cracks in a rock mass. A rock mass containing a group of cracks with small or no dip is more likely to scour when it is exposed to discharging water. The orientation of the cracks in a rock mass relative to the direction of the water flow has also an impact on the capacity of the rock mass to resist scour.</p><p>In the field study the scour pattern in the spillway channels of the hydro power plants in Ligga, Harsprånget, Porjus, Satisjaure and Seitevare was examined. The scour of rock mass in the spillway channels in Ligga, Harsprånget and Porjus has been extensive. The rock mass in these channels has bedding cracks of small distances. This is probably the reason why these rock masses are sensitive for loads from discharging water. The rock mass in the spillway channel in Satisjaure has lots of cracks and is also very sensitive for loads from discharging water. This channel has been rebuilt during 2004.</p><p>There are different methods to predict the ability of a rock mass to resist scour. The Erodibility Index Method is a semi-empirical method that is verified by field observations in the USA. In this work the ability to apply this method on Swedish channels has been examined with field observations from Porjus, Harsprånget and Seitevare. As the Erodibility Index Method seemed to work in the case of these three spillways, it was also applied on the spillways in Satisjaure and Ligga.</p><p>Measures to reduce the energy in the discharging water in the spillways are very effective to reduce the risk of scouring in the rock mass. Blasted stairs in the rock mass in a channel or a stilling basin downstream the sluice gate is something that can reduce the energy in discharging water. Further documentary of spillway channels, like mapping and laser scanning, would contribute to a further verification of the Erodibility Index Method and to get a general survey of the risk of scour in Swedish spillways.</p> / <p>Dagens klimatsituation ser ut att ge ökad mängd nederbörd i Sverige, vilket innebär att de svenska älvarna kommer att utsättas för allt högre vattenflöden. De flesta av Sveriges älvar är reglerade, d v s längs älvarna finns en mängd större och mindre dammar. Ett högre flöde i älvarna innebär även rikligare tillrinning till dammarna vilket medför att avbördningen från dem måste bli större. Avbördningen från dammarna sker genom utskov och höga vattenflöden i utskovskanalerna kan orsaka erosion på det berg som kanalen vanligen består av. Erosionen är av typen ”blockerosion” där hela bergblock av större eller mindre storlek lösgörs från bergmassan. I värsta fall kan blockerosionen krypa uppströms och erodera dammkroppen bakifrån, vilket skulle kunna innebära att dammen brister.</p><p>Syftet med detta arbete var att identifiera omfattning och typ av bergerosionsproblem som uppkommer i utskovskanaler. Blockerosion uppkommer i regel då forsande vatten skapar tryckskillnader mellan övre och undre ytan på block. Tryckskillnaden kan då skapa tillräckliga lyftkrafter för att block ska lossna. De huvudsakliga faktorerna som styr blockerosionen är bergmassans sprickighet och material, utskovskanalens geometri och vattnets flöde och ytfluktuation. Genom litteraturstudie, numerisk modellanalys samt fältstudie har inverkan på blockerosionen av sprickriktningar utretts. En bergmassa som innehåller sprickgrupper som har liten, nära horisontell, stupning är känslig för vattenbelastning. Stupningsriktningen i förhållande till flödesriktningen har också betydelse för blockerosionen. Stupningsriktning i flödesriktningen gör bergmassan mer känslig för belastning av forsande vatten och gynnar därmed erosionen.</p><p>Utskovskanalerna i Ligga, Harsprånget, Porjus, Satisjaure samt Seitevare har undersökts med avseende på erosionsrisk. Erosionen i Ligga, Harsprånget och Porjus har varit omfattande och detta beror troligtvis på att dessa kanaler har subhorisontella bankningssprickor med litet sprickavstånd. I Satisjaure är bergmassan mycket sprickig, varför denna kanal är mycket känslig för vattnets belastning. Där har dock åtgärder vidtagits så att kanalen ska tåla sitt dimensionerande flöde. I Seitevare är erosionsrisken i kanalens övre del liten.</p><p>Det finns olika metoder för att bedöma erosionsrisken i en bergmassa. Erosionsindexmetoden är en semiempirisk metod som är verifierad med platsobservationer i USA. Med hjälp av observationer från Porjus, Harsprånget och Seitevare har erosionsindexmetodens tillämplighet på svenska kanaler undersökts. För dessa tre observationer verkar metoden fungera bra och har därför även använts i kanalerna i Satisjaure och Ligga.</p><p>Energidämpande åtgärder i kanalerna, såsom energiomvandlargropar och utsprängda trappor i kanalerna, har visats sig vara mycket effektivt för att minska erosionsrisken. En noga dokumentering av utskovskanaler, som t ex kartering och inmätningar, skulle bidra till att erosionsindexmetoden kunde verifieras ytterligare och att en översiktlig bedömning av erosionsrisken i utskovskanaler enkelt kan erhållas.</p>