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The ability of a filter to stop erosion through cracks in the core of a embankment dam requires that the filter be graded so that it will restrain movement of particles from the core, and that the filter be truly cohesionless, so that it will not crack even when subjected to the same types of deformations that cause cracks in the core. To achieve resistance to cracking, most current filter criteria require that the filter should contain no more than 5% of material finer than the #200 sieve, and that this fine material should be non-plastic. This research study was conducted to investigate whether there specifications do, in fact, result in filters that can be relied upon to slump, fill cracks, and prevent interval erosion in embankment dams. The research study involved filter erosion tests using a 4-inch diameter device and a 12-inch square device, and "sand castle" tests to investigate the tendency for candidate filters to slump when immersed in water. These tests showed that conventional filter criteria  no more than 5% fines, and fines that are non-plastic, are conservative. The research study showed that even filters with 5% of highly plastic fines are able to slump, fill cracks, and prevent erosion. / Ph. D.

The Lossen dam is an embankment dam in the Swedish river Ljusnan. The dam is founded on thick layers of stratified glaciofluvial sediments and till. Ever since construction, there have been problems with high pore pressures, large seepage flows and springs downstream of the right part of the dam. After the first filling of the reservoir, a large drainage trench was constructed downstream of the dam to lower pore pressures. Sinkholes and settlements downstream of the dam have occurred repeatedly over the lifetime of the dam, particularly in the area surrounding the large drainage trench. This study aims to investigate the causes of the sinkholes and assess the risks of internal erosion in the foundation and in the soil downstream of the dam. A model of the groundwater flow has been created in Visual MODFLOW. Calculations for assessing the soils susceptibility for contact erosion and suffusion have been performed, using soil gradation curves (both from the 1960s and from new samples). The results from the erosion calculations show that the probability of contact erosion being the sole cause of the internal erosion is minor. However, a majority of the soil samples tested are internally unstable (susceptible for suffusion). The possibility of backward erosion piping can not be dismissed but would need further investigation in order to be properly assessed. Due to the very heterogeneous structure of the soil in the area downstream of the dam, it is hard to predict the extent of the eroding soil layers and, thus, the future development of the erosion. A conclusion is that the soil downstream of the dam is subject to internal erosion, which is also the cause of the observed sinkholes and settlements. The internal erosion is probably not a threat to dam safety at the moment, but can possibly evolve as a problem in the future. Therefore close monitoring of the changes in seepage patterns and sediment transport is recommended. Possible solutions to stop the erosion include extending the drainage system with more pressure relief wells, and placing a filter blanket in the seepage exit area. / Lossendammen är en jorddamm i älven Ljusnan.  Dammen är byggd ovanpå tjocka lager av morän och isälvssediment. Sedan första dämningen 1962 har problem med höga portryck, stora läckageflöden och källsprång nedströms dammen uppkommit. Efter första dämningen grävdes ett stort dränagedike (kallat Slits 19) ut nedströms om dammen, för att sänka portrycken i området. Sjunkhål och sättningar har uppkommit återkommande under dammens livstid, speciellt i området kring slitsen. Målet med denna studie är att undersöka orsaken till de uppkomna sjunkhålen och sättningarna, samt att bedöma risken för fortsatt intern erosion i dammens undergrund och i jorden nedströms dammen. En modell över grundvattenflödet i området har skapats i Visual MODFLOW. Jordens fallenhet för kontakterosion och suffusion har beräknats med hjälp av kornfördelningskurvor från jordprover (majoriteten av vilka är från 60-talet, samt några nya). Resultaten från beräkningarna visar att risken för att kontakterosion initieras är liten. Däremot visar en majoritet av de testade kornfördelningskurvorna att jorden är internt instabil (har fallenhet för suffusion). Sannolikheten för att bakåtskridande erosion initieras kan inte uteslutas baserat på det underlag som förelegat, men en pålitlig bedömning skulle kräva ytterligare undersökningar. Eftersom jorden under och nedströms dammen är väldigt heterogen, och de olika lagrens storlek och utbredning är okänd, är det svårt att förutspå hur erosionen kommer att utvecklas i framtiden. Slutsatsen är att jorden nedströms dammen utsätts för fortlöpande inre erosion. Inre erosion är också orsaken till de uppkomna sjunkhålen och sättningarna. I nuläget är erosionen ingen risk för dammsäkerheten, men kan komma att bli det i framtiden. Noggrann övervakning av eventuella förändringar i läckagemönstren och sedimenttransport är viktig. Bland möjliga lösningar för att avstanna erosionen finns utökning av dränagesystemet med nya filterbrunnar, samt att lägga ett filtrerande skyddslager över området där källsprången sker.

Embankment dams is the most common type of dams in operation inSweden today. Due to the nature of embankment dams, seepage throughthem will always occur. If the seepage velocity exceeds a critical velocity,internal erosion is initiated, which could lead to damage in form of pipingand sinkholes. To treat this problem, remedial grouting has beenperformed involving a combination of conventional grouts, i.e. cement andcement-bentonite as well as sodium silicate, which is a chemical grout thatalso known as water glass. Regarding the sodium silicate grout, there isconcern about the long-term permanence.The aim of this thesis has been to study the potential performance ofsodium silicate grouted in embankment dams. The first part of this thesisis a literature review of the general behavior of sodium silicate as a grout,its degradation processes and the factors that could induce degradation.The second part suggests monitoring methods to control and evaluate theperformance of the treated dam and the grout if degradation has occurred.Findings from literature generally indicates a high risk of instability andlow permanence of sodium silicate when grouted in an embankment dam.This type of grout will undergo degradation mainly in two forms: syneresisinduced shrinkage and leaching due to grout erosion or dissolution. As thedegradation has developed, an increase in permeability of the repaireddam core is a potential consequence.How the potential degradation of sodium silicate will affect the treateddams is suggested to be observed by monitoring the permeability of thegrouted core. Applicable monitoring methods for this purpose aremeasurements of pore pressure and temperature using piezometers. Thesecond direct method of monitoring a changed dam behavior is suggestedto be leakage analysis, in order to detect potentially increased leakagebecause of the grout degradation. An indirect way to investigate the damperformance is suggested to be monitoring of the grout state. Measurementof ion concentration of sodium and silicon respectively in leakage waterusing selective-ion electrodes will reveal any increase in ion concentrationdue to the potential grout dissolution or leaching.

<p>Dams that comprise broadly and widely graded glacial materials, such as moraines, have been found to be susceptible to internal erosion, perhaps more than dams of other soil types. Internal erosion washes out fine-grained particles from the filling material; the erosion occurs within the material itself or at an interface to another dam zone, depending on the mode of initiation. Whether or not internal erosion proceeds depend on the adequacy of the filter material. If internal erosion is allowed, it may manifest itself as sinkholes on the crest, increased leakage and muddy seepage once it surfaces, which here is called surfacing internal erosion (i.e. internal erosion in the excessive erosion or continuation phase). In spite of significant developments since the 1980s in the field of internal erosion assessment, the validity of methods developed by others on broadly graded materials are still less clear because most available criteria are based on tests of narrowly graded granular soils. This thesis specifically addresses dams that are composed of broadly graded glacial soils and investigates typical indicators, signs and behaviors of internal erosion prone dams. Based on a review of 90+ existing moraine core dams, which are located mainly in Scandinavia as well as North America and Australia/New Zealand, this thesis will show that not only the filter’s coarseness needs to be reviewed when assessing the potential for internal erosion to surface (i.e., erosion in the excessive or continuing phase); in addition, the grading stability of the filter and the core material as well as non-homogeneities that are caused by filter segregation need to be studied. Cross-referencing between these aspects improves the assessment of potential for internal erosion in dams of broadly graded soils and furthermore it provides aid-to-judgment.</p> / QC 20100715

In this study, dynamic response of Akk&ouml / pr&uuml / Dam under earthquake motions is analyzed and the permanent displacements are evaluated. Initially, the critical slip surface of the dam and the corresponding yield acceleration are determined by using the computer program SLOPE. Then, by employing the finite element program SAP2000, static analyses are performed to obtain the mean effective stresses which are used in the determination of dynamic material properties of the dam. Four different scenario earthquakes having a magnitude of 7 are used in the dynamic analyses. Two of those scenarios are taken from European Strong Motion Database and the others are generated by XS artificial earthquake generation program prepared by Erdik (1992). Dynamic analyses of the dam are carried out by the finite element program TELDYN. Permanent displacements of the critical slip surface are calculated by utilizing the Newmark method. Consequently, for an earthquake having a magnitude of M=7 and a peak ground acceleration of 0.20g, the maximum permanent displacement of the dam is found to be 15.90 cm. Furthermore, the permanent displacements of the dam are calculated under base motions having different peak ground acceleration values and it is observed that the rate of increase in the amount of permanent displacements is greater than the increase in the amount of peak ground accelerations.

Les fuites au travers des ouvrages hydrauliques en remblai sont les signes précurseurs d'un dysfonctionnementdu dispositif d'étanchéité de l'ouvrage pouvant entraîner leur rupture. La détectionprécoce des fuites et leur quanti_cation est donc primordiale.Les méthodes géophysiques et thermométriques à grand rendement apportent des éléments deréponse pour la détection des fuites, le long des ouvrages à long linéaire, mais l'estimation de leurvitesse, nécessaire à l'évaluation de la dangerosité des fuites, n'est pas encore satisfaisante.Cette étude porte sur la détection et quanti_cation des fuites à travers les ouvrages hydrauliquesen remblai soumis à une charge d'eau permanente. Les méthodes proposées exploitent des mesures detempératures naturelles du sol à l'aide de _bres optiques placées sous le talus amont ou aval.Deux modèles de quanti_cation ont été développés et testés sur les données d'un site expérimentalcontrôlé et d'un site réel. Les résultats obtenus concordent avec les mesures de vitesse e_ectuées surles deux sites. / Leakages through embankment dams are early warning signs of a sealing malfunction and couldlead to its breakdown. Early detection of leakages and their quanti_cation is essential.High output geophysical and thermometric methods provide some answers for leakage detectionalong long linear embankment dams, but their velocity estimations necessary to assess the danger ofleakages, is not yet satisfactory.This study focuses on the detection and the quanti_cation of leakages through embankment damsunder hydraulic head. The proposed method use natural temperature measurements from the groundusing optical _ber buried under the upstream or downstream face.Two models of quanti_cation were developed and tested on data from an experimental site and a realsite. Results are consistent with velocity measurements made at both side.

Dams that comprise broadly and widely graded glacial materials, such as moraines, have been found to be susceptible to internal erosion, perhaps more than dams of other soil types. Internal erosion washes out fine-grained particles from the filling material; the erosion occurs within the material itself or at an interface to another dam zone, depending on the mode of initiation. Whether or not internal erosion proceeds depend on the adequacy of the filter material. If internal erosion is allowed, it may manifest itself as sinkholes on the crest, increased leakage and muddy seepage once it surfaces, which here is called surfacing internal erosion (i.e. internal erosion in the excessive erosion or continuation phase). In spite of significant developments since the 1980s in the field of internal erosion assessment, the validity of methods developed by others on broadly graded materials are still less clear because most available criteria are based on tests of narrowly graded granular soils. This thesis specifically addresses dams that are composed of broadly graded glacial soils and investigates typical indicators, signs and behaviors of internal erosion prone dams. Based on a review of 90+ existing moraine core dams, which are located mainly in Scandinavia as well as North America and Australia/New Zealand, this thesis will show that not only the filter’s coarseness needs to be reviewed when assessing the potential for internal erosion to surface (i.e., erosion in the excessive or continuing phase); in addition, the grading stability of the filter and the core material as well as non-homogeneities that are caused by filter segregation need to be studied. Cross-referencing between these aspects improves the assessment of potential for internal erosion in dams of broadly graded soils and furthermore it provides aid-to-judgment. / QC 20100715

Energy harvesting can be used to consume the potential power of the surrounding environment. This harvesting can be done in different ways, some common energy harvesting modalities are vibrations, heat differences, solar power, and RF energy. In this Master Thesis, these different methods for harvesting energy are studied and the one that is the most suitable for an environment inside an embankment dam is further explored. If some energy harvesting modalities can operate well in that environment then it might be possible to monitor the embankment dam from the inside. The hope is to create an energy harvesting platform equipped with some suitable sensors which can be placed inside an embankment dam and collect data for a longer duration of time. Considering how an embankment dam is structured, it was concluded that the best possible energy harvesting method is wireless ultra-high frequency radio signals. An RF energy harvesting platform was created and tested, both in a laboratory and buried underground, mimicking the environment inside an embankment dam. These tests were measured and the results showed some promise that it is possible to use this energy harvesting method to power a sensor platform underground.

This study is an evaluation on the seismic behavior of the Nahrain Dam, which is located in Khorasan province in the central part of Iran. The finite element method is used for the dynamic analysis of the dam. Using a slope stability computer program, the critical slip surface near the crest of the dam and the yield acceleration corresponding to this slip surface are determined. Static analysis was completed by using the finite element computer program SAP90 and SAP2000 in order to determine the stress conditions within the body of the dam prior to earthquake. The stresses obtained from this analysis were used in the assessment of the dynamic material properties of the dam. Two near by actual earthquakes were modified and used as input motions of different magnitudes. At the next step, the harvested data was used as input data for the program TELDYN to perform dynamic analysis. Permanent displacements under the scenario base motions were calculated by using the Newmark&rsquo / s method.