Spelling suggestions: "subject:"embankment dam"" "subject:"embankments dam""
1 |
Forward modelling and inversion of streaming potential for the interpretation of hydraulic conditions from self-potential dataSheffer, Megan Rae 05 1900 (has links)
The self-potential method responds to the electrokinetic phenomenon of streaming potential and has been applied in hydrogeologic and engineering investigations to aid in the evaluation of subsurface hydraulic conditions. Of specific interest is the application of the method to embankment dam seepage monitoring and detection. This demands a quantitative
interpretation of seepage conditions from the geophysical data.
To enable the study of variably saturated flow problems of complicated geometry, a three-dimensional finite volume algorithm
is developed to evaluate the self-potential distribution resulting from subsurface fluid flow. The algorithm explicitly calculates
the distribution of streaming current sources and solves for the self-potential given a model of hydraulic head and prescribed distributions of the streaming current cross-coupling conductivity and electrical resistivity. A new laboratory apparatus is developed to measure the streaming potential coupling coefficient
and resistivity in unconsolidated soil samples. Measuring both of these parameters on the same sample under the same conditions
enables us to properly characterize the streaming current cross-coupling conductivity coefficient. I present the results of a laboratory investigation to study the influence of soil and fluid parameters on the cross-coupling coefficient, and characterize this property for representative well-graded embankment soils. The streaming potential signals associated with preferential seepage through the core of a synthetic embankment dam model are studied using the forward modelling algorithm and measured electrical properties to assess the sensitivity of the self-potential method in detecting internal erosion. Maximum self-potential anomalies are shown to be linked to large localized
hydraulic gradients that develop in response to piping, prior to any detectable increase in seepage flow through the dam. A linear
inversion algorithm is developed to evaluate the three-dimensional distribution of hydraulic head from self-potential data, given a known distribution of the cross-coupling coefficient and electrical resistivity. The inverse problem is solved by
minimizing an objective function, which consists of a data misfit that accounts for measurement error and a model objective function that incorporates a priori information. The algorithm is suitable
for saturated flow problems or where the position of the phreatic surface is known.
|
2 |
Forward modelling and inversion of streaming potential for the interpretation of hydraulic conditions from self-potential dataSheffer, Megan Rae 05 1900 (has links)
The self-potential method responds to the electrokinetic phenomenon of streaming potential and has been applied in hydrogeologic and engineering investigations to aid in the evaluation of subsurface hydraulic conditions. Of specific interest is the application of the method to embankment dam seepage monitoring and detection. This demands a quantitative
interpretation of seepage conditions from the geophysical data.
To enable the study of variably saturated flow problems of complicated geometry, a three-dimensional finite volume algorithm
is developed to evaluate the self-potential distribution resulting from subsurface fluid flow. The algorithm explicitly calculates
the distribution of streaming current sources and solves for the self-potential given a model of hydraulic head and prescribed distributions of the streaming current cross-coupling conductivity and electrical resistivity. A new laboratory apparatus is developed to measure the streaming potential coupling coefficient
and resistivity in unconsolidated soil samples. Measuring both of these parameters on the same sample under the same conditions
enables us to properly characterize the streaming current cross-coupling conductivity coefficient. I present the results of a laboratory investigation to study the influence of soil and fluid parameters on the cross-coupling coefficient, and characterize this property for representative well-graded embankment soils. The streaming potential signals associated with preferential seepage through the core of a synthetic embankment dam model are studied using the forward modelling algorithm and measured electrical properties to assess the sensitivity of the self-potential method in detecting internal erosion. Maximum self-potential anomalies are shown to be linked to large localized
hydraulic gradients that develop in response to piping, prior to any detectable increase in seepage flow through the dam. A linear
inversion algorithm is developed to evaluate the three-dimensional distribution of hydraulic head from self-potential data, given a known distribution of the cross-coupling coefficient and electrical resistivity. The inverse problem is solved by
minimizing an objective function, which consists of a data misfit that accounts for measurement error and a model objective function that incorporates a priori information. The algorithm is suitable
for saturated flow problems or where the position of the phreatic surface is known.
|
3 |
Forward modelling and inversion of streaming potential for the interpretation of hydraulic conditions from self-potential dataSheffer, Megan Rae 05 1900 (has links)
The self-potential method responds to the electrokinetic phenomenon of streaming potential and has been applied in hydrogeologic and engineering investigations to aid in the evaluation of subsurface hydraulic conditions. Of specific interest is the application of the method to embankment dam seepage monitoring and detection. This demands a quantitative
interpretation of seepage conditions from the geophysical data.
To enable the study of variably saturated flow problems of complicated geometry, a three-dimensional finite volume algorithm
is developed to evaluate the self-potential distribution resulting from subsurface fluid flow. The algorithm explicitly calculates
the distribution of streaming current sources and solves for the self-potential given a model of hydraulic head and prescribed distributions of the streaming current cross-coupling conductivity and electrical resistivity. A new laboratory apparatus is developed to measure the streaming potential coupling coefficient
and resistivity in unconsolidated soil samples. Measuring both of these parameters on the same sample under the same conditions
enables us to properly characterize the streaming current cross-coupling conductivity coefficient. I present the results of a laboratory investigation to study the influence of soil and fluid parameters on the cross-coupling coefficient, and characterize this property for representative well-graded embankment soils. The streaming potential signals associated with preferential seepage through the core of a synthetic embankment dam model are studied using the forward modelling algorithm and measured electrical properties to assess the sensitivity of the self-potential method in detecting internal erosion. Maximum self-potential anomalies are shown to be linked to large localized
hydraulic gradients that develop in response to piping, prior to any detectable increase in seepage flow through the dam. A linear
inversion algorithm is developed to evaluate the three-dimensional distribution of hydraulic head from self-potential data, given a known distribution of the cross-coupling coefficient and electrical resistivity. The inverse problem is solved by
minimizing an objective function, which consists of a data misfit that accounts for measurement error and a model objective function that incorporates a priori information. The algorithm is suitable
for saturated flow problems or where the position of the phreatic surface is known. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate
|
4 |
Seismic response of embankment dams with different upstream conditions / ため池堤体の異なる貯水状態を考慮した地震時応答Adapa, Gautham 24 September 2021 (has links)
京都大学 / 新制・課程博士 / 博士(工学) / 甲第23476号 / 工博第4888号 / 新制||工||1764(附属図書館) / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 渦岡 良介, 教授 三村 衛, 教授 肥後 陽介 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM
|
5 |
Laboratory investigation of suffusion on dam core glacial tillTuffa, Daniel Yadetie January 2017 (has links)
The objective of this study is to provide a better understanding of suffusion characteristics of glacial soils and to present a simple yet reliable assessment procedure for determination of suffusion in the laboratory.Internal erosion by suffusion occurs in the core of an embankment dam when the ability of the soil to resist seepage forces is exceeded and voids are large enough to allow the transport of fine particles through the pores. Soils susceptible to suffusion are described as internally unstable. dams with core of broadly graded glacial moraines (tills) exhibit signs of internal erosion to a larger extent than dams constructed with other types of materials.The Suffusion behavior of glacial soils has been investigated through two different permeameter suffusion test have been employed, small scale permeameter and big scale permeameter. Details of the equipment along with its calibration, testing and sampling procedures are provided.The testing program were performed 9 test with different compaction degree in small scale permeameter and 2 test in big permeameter on internally stable categories of till soil. The categories are defined based on the soil grain size distribution and according to the methods developed by Kenney & Lau and Burenkova.Layers are identified with suffusion if the post-test gradation curve exhibit changes in distribution compared to the initial condition and also the tests revealed that the effect of grain size distribution and relative degree of compaction on the internal erosion susceptibility of glacial till soils at different hydraulic gradients
|
6 |
Modelling internal erosion within an embankment dam prior to breachingVazquez Borragan, Alejandro January 2015 (has links)
There are still uncertainties in the safety of existing embankment dams. For instance, the majority of embankment dams in Sweden were built between 1950s and 1970s, designed and constructed to standards that might be unacceptable nowadays. Particularly, Vattenfall’s records stated that 40% owned embankments dams developed sinkholes (Nilsson, 1999). Moreover, internal erosion and its failure mechanisms of initiation and development are still not fully understood (Bowles et al., 2013). Also, internal threats are difficult to detect and interpret even using new instrumentation techniques. The aim of this Master Thesis is to identify failure mechanisms of embankment dams prior to breaching and hence, verify the reliability of a risk analysis after the breaching of the dam. The methodology consisted of monitoring an embankment dam prone to fail by internal erosion mechanisms. Finally the results were modelled using FEM to identify the risk of internal erosion prior to breaching.
|
7 |
Geomechanical testing of non-hardening grout : for determination of flowability and strength propertiesBarrdahl, Axel January 2022 (has links)
Due to an increasing amount of aging tendencies in Swedish embankment dams, failures such as internal erosion has become a more common problem. Internal erosion is a phenomenon where certain soil material within the embankment dam is removed, often over a longer period of time. It is most common to occur at the inner core of the dam, and if it is allowed to continue for a longer time period the consequences can be disastrous. During the internal erosion, the inner material is washed out, creating larger voids and lowering the geotechnical stability of the dam. When larger voids start to appear, the seepage will increase allowing more material to be washed out and accelerating the process. In order to repair an embankment dam, exposed to inner erosion, it requires both the location of the faults as well as a suitable method of repairing. A method to repair internal erosion is by using grout and injecting it into the location of the fault. The knowledge regarding what type of grout and how it should be treated is today lacking. There are reasons to believe that a hardening mixture within an embankment dam using a till core will not cooperate well. For that reason, a grout with non-hardening properties is of interest. this thesis focuses on the Geomechanical strength parameters of two similar experimental non-hardening grouts. One with maximum grain size of 2 mm referred as grout 0/2, and one with maximum grain size of 4 mm, referred to as grout 0/4. The grouts consist of natural aggregates, calcium carbonate, water, bentonite, superplasticizer and defoamer. The grouts are evaluated by its undrained shear strength, water content, bulk- and dry density using fall cone tests and uniaxial compressive strength tests. To evaluate the grouts angle of friction and angle of dilatancy together with young’s modulus, consolidated, drained triaxial tests were performed. Three tests with different consolidation pressures (50, 150 and 300 kPa) were performed for each grout. Since the grout will gain strength with time, the tests have been performed after certain number of days in order to see the development of the grouts. The laboratories stretch from 0 to 112 days since the time of mixing the grout, and was performed at Luleå University of technology. Fall cone tests showed that the grout should most likely be mixed on site and left unstirred. Continuously stirring the grout quickly removed the grouts flowability which is why longer transportation should be avoided. At the same time, the accuracy of the grouts mixing is very demanding which needs to be taken into consideration. Triaxial tests showed that the grout 0/2 had dilatant behavior for 50 and 150 kPa consolidation pressure while 300 kPa showed contractive behavior. The grout 0/4 had dilatant behavior for 50 kPa consolidation pressure while 150 and 300 kPa showed contractive behavior. A theory to explain this behavior was constructed where the bentonite is believed to be behind it. Bentonite slurries behave as a Bingham fluid, where it requires a certain amount of shear stress for the fluid to start to flow. With the same reasoning, the low consolidation pressures do not exceed that threshold, resulting in dilatant behavior. But once that threshold is surpassed the grout starts to contract. In addition, flow curve tests were performed for additives, superplasticizer and defoamer. Both these substances showed Newtonian behavior which leaves Bentonite to be the only additive with Binghamian behavior. / På grund av en ökad mängd med föråldrandetendenser hos svenska jordfyllningsdammar har brott så som inre erosion blivit ett alltmer vanligt problem. Inre erosion är ett fenomen där en viss jord inom jordfyllningsdammen är avlägsnad, generellt över en längre tidsperiod. Oftast inträffar detta vid den inre damkärnan och om erosionen är tillåten att fortskrida sig över en längre period kan konsekvenserna bli förödande. Inre erosion fungerar så att jordmaterial tvättas ut vilket skapar hålutrymmen och minskar den geotekniska hållfastheten för dammen. När större hålutrymmen bildats ökar läckaget som i sin tur tillåter mer material att bli urtvättat och processen blir accelererad. För att kunna reparera en jordfyllningsdam, utsatt för inre erosion, krävs både att platsen för brottet och metoden för att reparera är kända. En metod för att reparera inre erosion är genom att använda injektering och injektera hålutrymmet. Dock är kunskapen gällande vad för typ av injektering och hur den ska hanteras icke existerande i dagsläget. Det finns anledning att tro att ett härdande bruk inom en jordfyllningsdam, med en moränkärna, inte kommer samarbeta särskilt bra. På grund av det har ett bruk med icke-härdande egenskaper undersökt. Den här uppsatsen fokuserar på de geotekniska hållfasthetsegenskaperna för två liknande experimentella icke-härdande bruk. Ett med maximal kornstorlek på 2 mm benämnd som bruk 0/2 och ett med maximal kornstorlek på 4 mm, benämnd som bruk 0/4. Bruket består av natursand, kalciumkarbonat, vatten, bentonit, mjukgöringsmedel och skumdämpare. Bruken är utvärderade genom deras odränerade skjuvhållfasthet, vattenkvot, skrym- och torrdensiteten som har tagits fram från fallkorns-test och enaxiella trycktest (UCS). För att utvärdera brukens friktionsvinkel och dilationsvinkel tillsammans med styvheten (initiella och 50 %) har konsoliderat, dränerat triaxiala tests utförts. Tre test med varierande konsolideringstryck (50, 150 och 300 kPa) har utförts för båda bruken. I och med att brukens hållfasthet kommer att öka med tiden, har testerna utförts efter ett visst antal dagar, för att se hur utvecklingen ser ut. Laborationerna har sträckt sig från 0 till 112 dagar sedan det att bruken har blandats, och utfördes vid Luleå Tekniska Universitet. Fallkornstesten visade att bruken bör med största sannolikhet blandas på arbetsplatsen och därefter förbli orörda. Kontinuerlig omrörning visade sig frånta brukens flytförmåga, vilket också är anledning till varför längre transporter bör undvikas. Samtidigt så är noggrannheten vid brukens blandning krävande vilket bör tas i beaktning. De triaxiala tester visade att bruk 0/2 visade ett dilatant beteende för både 50 och 150 kPa konsolideringstryck medan 300 kPa hade ett kontrakterande beteende. Bruket 0/4 hade dilatant beteende för 50 kPa konsolideringstryck medan 150 och 300 kPa visade kontrakterande beteende. En teori för att förklara detta beteende togs fram där bentoniten är den troliga orsaken. Bentonitblandningar (bentonite slurry) beter sig som en Bingham-vätska, där det krävs en viss mängd skjuvspänning för att få vätskan att börja flyta. Med samma resonemang applicerade på bruken innebar det att de låga konsolideringstrycken inte översteg tröskelvärdet, vilket resulterade i ett dilatant beteende. Däremot, när tröskelvärdet väl är överstiget börjar bruket att kontraktera istället. Det gjordes även flödestester på tillsatsmedlen, mjukgöringsmedel och skumdämpare. Testerna visade att båda medel betedde sig Newtoniskt, vilket lämnar bentoniten som det enda tillsatsmedlet med Bingham-beteende.
|
8 |
Resistivity and Seismic Characterization of an Embankment Dam. A Case Study in Northern Sweden / Resistivitet och seismisk karaktärisering av en jordfyllningsdamm. Ett fältarbete i norra SverigePolín-Tornero, Álvaro January 2018 (has links)
The main cause of failure in embankment dams - which represent 75% of all dams in the world (ICOLD, 2018) - is the internal erosion produced by excessive seepage not accounted for in their designs. This erosion can cause that a small anomalous structure, not likely to be considered as risky, turns rapidly into a significant structural damage if not recognized on time. This creates a necessity for methods that can detect these anomalies in a non-intrusive, cost-effective and sensitive way. The purpose of this work is to analyse the strength of three geophysical methods (ERT and Seismic Refraction and Reflection) in detecting and accurately localizing anomalous structures inside an embankment dam. This study has been successfully approached in two different ways: by synthetic modelling and by an experimental field work at an embankment dam in northern Sweden. The results show that these methods are capable of detecting different structures in the interior of the dam in an accurate and rapid manner. / Den främsta orsaken till brister i jordfyllningsdammar, som utgör 75% av alla dammar i världen (ICOLD, 2018) och är föremål för detta arbete, är inre erosion som orsakas av extrem läckage som togs inte med i beräkningar i deras konstruktioner. Denna erosion kan resultera i att en liten anomal struktur, som sannolikt inte anses vara riskabel, snabbt blir en betydande strukturell skada om den inte är uppmärksammas i tid. Därför krävs metoder som kan upptäcka dessa anomalier på ett icke-påträngande, kostnadseffektivt och känsligt sätt. Syftet med detta arbete är att analysera möjligheterna med tre geofysiska metoder (ERT, Seismisk Refraktion och Seismisk Reflektion) för att upptäcka och exakt lokalisera anomala strukturer inuti en jordfyllningsdamm. Denna studie har utförts på två fronter: genom (i) syntetisk modellering och (ii) ett experimentellt fältarbete vid en damm i norra Sverige. Resultaten visar att dessa metoder kan detektera olika strukturer inuti dammen på ett pålitligt och snabbt sätt.
|
9 |
Utveckling av en generell metod för läckageövervakning vid fyllningsdammarGasim, Alia January 2020 (has links)
Fyllningsdammar har alltid ett naturligt läckage då jordmaterialet som används har en viss permeabilitet. Detta acceptabla naturliga läckage är viktigt att övervaka för att kontrollera att läckageflödet håller sig inom förväntade värden. Om läckaget blir för stort, kan det leda till felmoder som i sin tur leder till dammbrott. Damminstrumentering som möjliggör övervakning av läckage i fyllningsdammar är ett krav enligt RIDAS. På nedströmssidan av fyllningsdammar finns det dränagerör som samlar upp och leder läckagevatten till platser där läckaget mäts med något slags instrument. Detta mätinstrument mäter inte endast läckaget genom fyllningsdammar, utan påverkas även av yttre faktorer såsom nederbörd och evapotranspiration. Detta examensarbete syftar därför att utveckla en generell metod för läckageövervakning vid fyllningsdammar, för att erhålla det normala läckaget. Hur det normala läckaget kan erhållas allmängiltigt för fyllningsdammar har presenterats. Det normala läckaget genom dammkroppen kan antingen erhållas med hjälp av fysikalisk läckageberäkning (qD1,Fysikalisk) eller från läckagemätning (qD1,Läckagemätning). Fysikalisk läckageberäkning bygger på en genomströmningsmodell baserat på fysikaliska samband. Läckage från läckagemätning baseras på en vattenbalansekvation där läckageflödet är en term av flera, som uppmätt läckage nedströms dammen, nederbörd och avdunstning. En fallstudie har genomförts för en av Vattenfalls dammanläggningar för att testa den metodik som framtagits för erhållande av det normala läckaget. De fysikaliska läckageberäkningarna har modellerats fram med hjälp av COMSOL Multiphysics och läckaget från läckagemätningarna har beräknats fram med hjälp av vattenbalansekvationen och indata på hydrologi. Resultatet visar att det är viktigt att ta hänsyn till de yttre faktorerna från vattenbalansekvationen eftersom dessa kan ha en betydande påverkan på det läckageflöde som faktiskt mäts. Vidare bedöms det betydande att modellera läckage baserat på en fysikalisk baserad strömningsmodell eftersom detta värde sällan finns idag. Då kan en jämförelse av läckage från läckagemätningar jämföras med det fysikaliska läckaget. Det bedöms att beräkning av läckage från läckagemätningar med hjälp av vattenbalansekvationen är en bra metod för att beräkna läckaget genom dammar. Dock behöver den studerade dammanläggningen en djupare analys för att senare kunna tillsätta gränsvärden. Detta genom att även undersöka läckage under dammkroppen och magasinsförändringar vid beräkning av läckage från läckagemätningar. Det fysikaliska läckaget genom att modellera genomströmningen för hela geometrin och genom att utföra en tidsberoende modellering. / Embankment dams are not completely impervious as its core materials has a certain permeability. This seepage is important to monitor to follow-up to ascertain that it stays as expected. If the seepage increase above design, failure modes could occur and ultimately a dam failure. The Swedish dam safety guideline RIDAS deals with this safety aspect by requirements on instrumentation to measure seepage. Downstream embankment dams, drainage leads seepage water to an outflow point where seepage can be measured. However, at these points the measured flow also is impacted by external factors such as precipitation and evapotranspiration. The aim of this report is to propose a method where the measured flow by post-processing can exclude the impact of these external factors. The normal seepage through a dam can either be obtained by modelling (where the physical seepage has been obtained based on physical relationships) or by a water balance equation (where the seepage from measurement downstream a dam is a part of the water balance equation, including the impact by precipitation and evapotranspiration. A case study has been carried out on a dam operated by Vattenfall, as a means to assess the proposed methodology. The seepage has been modelled using the COMSOL Multiphysics software, and the seepage from measurements has been calculated by the water balance equation. The results show that it is important to take into account external factors as it clearly affects the measured seepage flow. Furthermore, it is of great importance to calculate the theoretical design seepage, which is a threshold value level that is rarely modelled today. If both the seepage from measurements and theoretical seepage is obtained, a comparison of these can be made. The seepage from measurements (with the help of the water balance equation) is a good method to obtain embankment dam seepages. However, the results from the case study implies that further work is needed to be able to set relevant limit values.
|
10 |
An Overview of State-of-the-art Hydraulic Conductivity Measurements in Coarse Grained Materials / En översikt över toppmoderna mätmetoder för hydraulisk konduktivitet i grovkorniga materialAndrén, Jakob January 2021 (has links)
Embankment dams are made from soil materials of varying sizes and widely used all over the world.When constructing these, knowing the hydraulic conductivity (K) of the soil materials is a keyparameter in order to construct safe embankment dams. A knowledge gap regarding K measurementsin coarse grained soils has been identified. This thesis aims to provide a theoretical overview ofpresent day state-of-the-art methods for measuring hydraulic conductivity and the controllingcharacteristics for K. Coarse grained soils refers to a soil with the coarsest grain fraction being > 20mm and/or have a K > 10-4m/s. It was found that the fixed wall permeameter is the most suitable laboratory method. In the field, itis possible to estimate K using tracer methods, these however show more potential for leakagepathway detection. Common for all K measurement methods are the controlling characteristics of K,grain size distribution, pore geometry, degree of compaction, particle movement and flow regime.These need to be considered when testing to produce useful measurements. If the relationshipbetween flow velocity and hydraulic head is non-linear, Darcy's law is not valid for calculating K. / Fyllnadsdammar är uppbyggda av jord och sprängsten av olika storlekar och finns över hela världen.Att känna till den hydrauliska konduktiviteten (K) av de olika lagren är viktigt för att kunna byggadessa på ett säkert och hållbart sätt. Det har identifierats en bristande kunskap angående K mätningar igrovkorniga jord- och stenmaterial. Målet med denna uppsats är att presentera en teoretisk översikt avden senaste kunskapen inom K mätningar i grovkorniga jord- och stenmaterial och vilka egenskapersom avgör ett materials K. Grovkorniga jord- och stenmaterial syftar till material där den grövstakornstorleken är > 20 mm och/eller har ett K > 10-4m/s. För laboratorie mätningar är en permeameter med en solid vägg den mest lämpliga metoden. Förfältmätningar är det möjligt att mäta K med hjälp av spårämnen, men dessa har mer potential för attupptäcka läckage vägar i fyllnadsdammar. De faktorer som avgör ett materials K ärkornstorleksfördelningen, geometrin av porerna, graden av kompaktering, partikelrörelse ochflödestyp. För att producera mätningar som är användbara behöver dessa faktorer kontrolleras. Omsambandet mellan hydrauliskt huvud och flödeshastighet är icke linjärt kan K inte beräknas genomDarcy´s lag.
|
Page generated in 0.0803 seconds