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Background: Embankment dams were built south of the Laizhou bay in China for controlling storm surge disasters, but they are not enough to replace coastal forests in protecting the land. This study was designed to evaluate the effects of embankment dams on natural forests dominated by Tamarix austromongolica and test whether the dam-shrub system is a preferable updated defense. Methods: Coastal forests on two typical flats, one before and one behind embankment dams, were investigated using quadrats and lines. Land bareness, vegetation composition and species co-occurrence were assessed; structures of T. austromongolica populations were evaluated; and spatial patterns of the populations were analyzed using Ripley's K and K1,2 functions. Results: In the area before embankment dams, 84.8% of T. austromongolica were juveniles (basal diameter ≤ 3 cm), and 15.2% were adults (basal diameter > 3 cm); behind the dams, 52.9% were juveniles, and 47.1 were adults. In the area before the dams, the land bareness was 13.7%, four species occurred, and they all were ready to co-occur with T. austromongolica; behind the dams, the land bareness was 0%, and 16 species occurred whereas they somewhat resisted co-occurrence with T. austromongolica. In the area before the dams, the T. austromongolica population was aggregated in heterogeneous patches, and the juveniles tended to co-occur with the adults; behind the dams, they were over-dispersed as nearly uniform distributions, while the juveniles could recruit and were primarily independent of the adults. These results indicate that the T. austromongolica species did not suffer from the unnatural dams, but benefited somehow in population expansion and development. Overall, the T. austromongolica species can adapt to artificial embankment dams to create a synthetic defense against storm surges. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering (17264073) is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Dolgu barajların uzun dönemli güvenliği, sızma akımının gerçekleştiği zeminlerin içsel stabilitesine bağlıdır. Sufüzyon/sufozyon, kohezyonsuz zeminlerde görece ince malzemelerin, iri malzemelerin arasındaki boşluklardan sızma akımıyla taşınması olarak tanımlanır. Sufüzyon/sufozyon mekanizmasına bağlı olarak gerçekleşen içsel stabilite bozulmasıyla, granüler filtrelerde geriye doğru erozyon(borulanma) veya boşluk suyu basıncındaki artışa bağlı olarak statik stabilite kaybı gözlemlenebilir. Sufüzyonun gerçekleşebilmesi için iki koşul vardır: Sızma akımının yeterli hidrolik eğime sahip olması ve malzemenin granülometrisinin danelerin taşınmasına elverişli olması. Granüler filtrelerin tasarım ve planlanmasında sufüzyon mekanizmasının önceden belirlenebilmesi için bazı yaklaşımlar geliştirilmiştir. Bu çalışmada, dane çapı dağılım eğrisini kullanarak içsel stabilite potansiyelini belirleyen Istomina, Kezdi, Kenney ve Lau ile Burenkova metotları karşılaştırılmıştır. Eskişehir ili sınırları içerisinde yer alan Gökpınar Barajı’nın yarı-geçirimli malzeme sahasındaki plastik olmayan zeminler üzerinde yapılan çalışmaya göre, yöntemlerin uygulama esasları birbirine benzedikçe aynı değerlendirme sonucunu bulma oranları artmaktadır.

Once a dam breaks, it will cause serious loss of life and property. The dam failure process shows typical chain characteristics, and identifying the typical patterns and evolutionary characteristics of dam failure accident chains is conducive to the development of engineering disaster prevention and mitigation work. Embankment dam is one of the main dam types of reservoir dams in China. Aiming at the problems of complex disaster-causing factors, strong uncertainty and single quantitative analysis method of dam failure events, the paper takes embankment dam as the research object, and establishes a complex network model of embankment dam failure accident chains by deeply exploring the potential risk events and dam failure patterns in historical dam failure data. Based on the differences in the chronological characteristics of embankment dam failures, it quantifies the correlation degree and influence degree among the risk events in typical dam failureaccident chains using a risk event co-occurrence matrix. The method of quantifying the probability of evolution of embankment dam failure accident chains is proposed, and the evolution results are compared with the existing research results, which verifies the effectiveness and feasibility of the proposed method to a certain extent. The research results provide important technical support for strengthening the risk prevention and control of reservoir dam. [ABSTRACT FROM AUTHOR]

Electrical resistivity tomography (ERT) is a potential-based method for detecting internal erosion in the core of embankment dams using the electrodes installed outside. This study aims at evaluating the practical capability of ERT monitoring for detecting internal defects in embankment dams. A test embankment dam with in-built well-defined defects was built in Älvkarleby, Sweden, to assess different monitoring systems including ERT and the defect locations were unknown to the monitoring teams. Between 7500 and 14,000 ERT data points were acquired daily, which were used to create the distribution of electrical resistivity models of the dam using 3D time-lapse inversion. The inversion models revealed a layered resistivity structure in the core that might be related to variations in water content or unintentional variations in material properties. Several anomalous zones that were not associated with the defects were detected, which might be caused by unintentional variations in material properties, temperature, water content, or other installations. The results located two out of five defects in the core, horizontal and vertical crushed rock zones, with a slight location shift for the horizontal zone. The concrete block defect in the core was indicated, although not as distinctly and with a lateral shift. The two remaining defects in the core, a crushed rock zone at the abutment and a wooden block and a crushed rock zone in the filter, were not discovered. The results cannot be used to fully evaluate the capability of ERT in detecting internal erosion under typical Swedish conditions due to limited seepage associated with the defects. Furthermore, scale effects need to be considered for larger dams. [ABSTRACT FROM AUTHOR]

The estimation of the flood area inaccuracies by the propagation of Manning's coefficient uncertainty is crucial for safety plans of dam-breaks. However, the probabilistic studies of fluvial inundation concentrate on the 1D models, and those that address to evaluate the variable floodplain roughness based on the land cover are deterministic approaches. Thus, this study proposed to analyze the propagation of Manning's coefficient uncertainty, whose variation was obtained by (1) floodplain land use; (2) Monte Carlo method considering different distributions, in a 2D model for Três Maria's dam (Brazil). The results indicated: (1) the distributed coefficient reduced by 9% the flood area from deterministic scenarios with the fixed coefficient; (2) the normal distribution created higher variability in analyzed parameters than a uniform distribution, although we found no significant difference between the distributions. The understanding of input variables in 2D models may contribute to the management of dam failure risk. [ABSTRACT FROM AUTHOR]

Background Embankment dams were built south of the Laizhou bay in China for controlling storm surge disasters, but they are not enough to replace coastal forests in protecting the land. This study was designed to evaluate the effects of embankment dams on natural forests dominated by Tamarix austromongolica and test whether the dam-shrub system is a preferable updated defense. Methods Coastal forests on two typical flats, one before and one behind embankment dams, were investigated using quadrats and lines. Land bareness, vegetation composition and species co-occurrence were assessed; structures of T. austromongolica populations were evaluated; and spatial patterns of the populations were analyzed using Ripley’s K and K1,2 functions. Results In the area before embankment dams, 84.8% of T. austromongolica were juveniles (basal diameter ≤ 3 cm), and 15.2% were adults (basal diameter > 3 cm); behind the dams, 52.9% were juveniles, and 47.1 were adults. In the area before the dams, the land bareness was 13.7%, four species occurred, and they all were ready to co-occur with T. austromongolica; behind the dams, the land bareness was 0%, and 16 species occurred whereas they somewhat resisted co-occurrence with T. austromongolica. In the area before the dams, the T. austromongolica population was aggregated in heterogeneous patches, and the juveniles tended to co-occur with the adults; behind the dams, they were over-dispersed as nearly uniform distributions, while the juveniles could recruit and were primarily independent of the adults. These results indicate that the T. austromongolica species did not suffer from the unnatural dams, but benefited somehow in population expansion and development. Overall, the T. austromongolica species can adapt to artificial embankment dams to create a synthetic defense against storm surges.

Dams are mega structures that retain huge volumes of water and their safety is important to national security, economy, and public interest. In this study, the types of regular measurements with their recorded value for Haditha Dam were checked for compliance with the standard international surveillance and monitoring procedures such as the procedures of the International Commission on Large Dams (ICOLD), the United States Bureau of Reclamation (USBR)and other to ensure safe dam operation and to avoid the scenario of the Derna Dam break, in Libya that occurred in September 2023. The result shows that the highest recorded settlement was found at station 41 on the left side of the dam body exceeding the design criteria (219 mm) by about 51 %, the frequency of measurement does not comply with the required international standards. There are 7 cells of pore pressure that exceeded the design criteria and the greatest percentage of exceedance was 21.57 % was found at pore pressure number 995. For piezometer reading, the percentage exceedance was 9.1% and it was found on the left side at piezometers number 58-8. The highest percentage of movement 62 % was found at join meter device number D18. The recorded seepage rate through the dam was found within the permitted limits. The visual inspection followed at Haditha Dam was not according to the standard required inspection.

We suggest a new approach for evaluating the dynamic response of existing embankment dams as a guideline for national engineering regulations in Serbia. This novel concept is applied to the case study of the existing embankment dam "Zavoj" (Serbia), built at the place of the previously formed natural dam (due to large landslide activity), and exposed to Mw7.4 Vrančea earthquake and under double impact of Kresna earthquake (Mw6.8 and Mw7.1). Results of transient FEM and direct dynamical analysis of the three- dimensional FEM model of the "Zavoj" dam indicate that the existing dam is stable in dynamic conditions, while the surrounding terrain is either on the verge of stability or becomes unstable, depending on the assumed geotechnical conditions and a relevant earthquake analyzed. As a result, we construct a landslide hazard map in dynamic conditions and the dam damage map, which enables the identification of unstable, damaged, or weak parts of the dam, its immediate surroundings, and the accumulation zone in general. The results indicate that direct dynamical analysis is obligatory when two succeeding earthquakes occur and temporal evolution of displacements in the model is required. Additionally, the application of the remaining bearing capacity criterion indicates a much larger zone of potential instability compared to the extent of equivalent plastic strain and the location of the old sliding surface. By following the proposed guidelines, one secures the inclusion of all the relevant influential factors in the comprehensive dynamic analysis of existing embankment dams, leading eventually to reliable decisions on further design, (re)construction, and/or monitoring activities. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering & Architectural Faculty of Eskisehir Osmangazi University / Eskişehir Osmangazi Üniversitesi Mühendislik ve Mimarlık Fakültesi Dergisi is the property of Eskisehir Osmangazi University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The results of numerical modeling are presented for a complex cascade hydrodynamic breakdown (not based on an actual threat) caused by a dam break in the body of the Verkhneural'sk embankment dam. The studies were carried out by the methods of numerical hydrodynamic modeling using the Russian software package STREAM 2D CUDA. [ABSTRACT FROM AUTHOR]

We suggest a new approach for evaluating the dynamic response of existing embankment dams as a guideline for national engineering regulations in Serbia. This novel concept is applied to the case study of the existing embankment dam “Zavoj” (Serbia), built at the place of the previously formed natural dam (due to large landslide activity), and exposed to Mw7.4 Vrančea earthquake and under double impact of Kresna earthquake (Mw6.8 and Mw7.1). Results of transient FEM and direct dynamical analysis of the three-dimensional FEM model of the “Zavoj” dam indicate that the existing dam is stable in dynamic conditions, while the surrounding terrain is either on the verge of stability or becomes unstable, depending on the assumed geotechnical conditions and a relevant earthquake analyzed. As a result, we construct a landslide hazard map in dynamic conditions and the dam damage map, which enables the identification of unstable, damaged, or weak parts of the dam, its immediate surroundings, and the accumulation zone in general. The results indicate that direct dynamical analysis is obligatory when two succeeding earthquakes occur and temporal evolution of displacements in the model is required. Additionally, the application of the remaining bearing capacity criterion indicates a much larger zone of potential instability compared to the extent of equivalent plastic strain and the location of the old sliding surface. By following the proposed guidelines, one secures the inclusion of all the relevant influential factors in the comprehensive dynamic analysis of existing embankment dams, leading eventually to reliable decisions on further design, (re)construction, and/or monitoring activities.

There are a large number of reservoir dams in China, of which embankment dams account for more than 90%, and public safety will be seriously endangered in case of dam failure. Overtopping is the leading cause of dam failure, and the existing research mainly focuses on the study of the failure process, with less research on the change in the deformation field during the failure process. In this study, the measured deformation field data of a modeled embankment dam during the whole process of impoundment, operation, and failure were obtained by carrying out indoor small-scale model experiments of overtopping failure, embedding inclinometers inside the dam body, and setting vertical displacement measurement markers on the surface. A refined analysis of the measured deformation data shows that the dam body displaces vertically downward during the impoundment stage and the vertical displacement at the dam crest has the largest amplitude; the internal horizontal displacement changes to the left bank and downstream side, and the amplitude of the internal horizontal displacement (upstream and downstream direction and dam axis direction) on the right dam sections is more significant than that in the middle of the dam; during the breaching stage, the time sequence of the sudden change in each internal horizontal displacement measuring point is from the downstream side to the upstream side and from the higher elevation to the lower elevation, which is basically consistent with the process of overtopping of embankment dams; and the overall sudden change in left and right bank horizontal displacements within the downstream side of the dam crest and the downstream side of the dam body gauges is significant, and the sudden change in upstream and downstream horizontal displacement (U&D HD) within the downstream side of the dam crest gauges is significant. The experimental analysis results can support the disaster mechanism of embankment dam failure and the theory of early warning of failure. [ABSTRACT FROM AUTHOR]

This study determines the reason for embankment leakages of a large dam and demonstrates the importance of site evaluations, aside from numerical seepage and slope stability analyses, to assess whether the leakage observed in the embankment dam is related to seepage from the reservoir or from the groundwater that flows into the embankment. Using the software SLIDE, numerical seepage analysis was performed to determine the seepage pattern and pore water pressures. Results revealed that the calculated seepage exit elevation at the embankment's downstream shoulder perfectly matched the measured elevation of the leak. Finite element method seepage analyses showed that reservoir water seeped beyond the dam's chimney filter layer and intersected the downstream slope, which further clarifies that the filter has not functioned well. This study finally puts forth that the leakages are mainly due to the use of a silty sandy soil band together with MH and CH soils compacted excessively on wet side of the optimum moisture content. In addition, through numerical seepage analyses, pore water pressures in the embankment were also calculated for slope stability computations of the embankment. Slope stability analyses showed that safety of the dam slopes is not adequately reliable for even the existing partial impoundment and static loading cases. Thus, this study also suggests that the reservoir water should be kept in an existing partial level and not increased to its designed level. Eventually, the study proposes two remedial measures alternatively and evaluates the best solution. [ABSTRACT FROM AUTHOR]

Experimental investigation of embankment dams due to overtopping breach is a remarkable subject because it is the most possible failure reason, and it includes a complicated process. The mentioned phenomenon physical modeling has performed at energy ministry water research institute, hydraulics laboratory, and its hydraulic outputs compared with a benchmark model outcome in three scenarios framework. The results reveal that the breach process of physical models comprises three stages: i.e., initiation, development, and the end. Also, the development time is longer than that of the other stages. In first scenario, when shell gradation d50 varied from 0.5mm to 1.7mm, 26 percent of peak discharge increased and 14 percent of breach time decreased. In second scenario in which lake water level maintained at overtopping threshold for two hours (for more saturation), 15 percent of peak discharge and 14 percent of breach time declined. In third scenario where the primary breach groove did not excavate, the highest difference in comparison with benchmark model results occurred, when 34 percent of peak discharge grew and 24 percent of breach time reduced. Moreover, asymmetrical sedimentation pattern happened in the last scenario. The Calculation of eroded material volume and mass was sedimentation pattern determination harvest. Herein, the simultaneous measurements of breach geometry, flow hydrograph, and final sedimentation pattern are the research unique achievements. However, further acquired analysis would be influential for the embankment dam's failure phenomenon management. [ABSTRACT FROM AUTHOR]

The study examined the intricate relationships between embankment slope configurations, toe drain designs, and drawdown scenarios. It utilized a unique combination of numerical, physical, and mathematical models. The investigation involved 16 numerical models and 8 physical models with distinct characteristics. The research explored the correlations of key parameters: matric suction, horizontal water conductivity, time, and factor of safety. The factor of safety values varied from 0.62 to 1.03 as a result of the different investigated combinations. For instance, a 1:2 embankment slope without a toe drain under instantaneous drawdown led to the factor of safety values ranging from 1.22 to 1.57. Additionally, incorporating elements like a 30 m toe drain and a 1 m per day drawdown rate influenced these values, with extremes recorded from 1.337 to 2.21, shedding light on embankment stability under diverse conditions and configurations. When subjected to a 1 m per day drawdown, water flow rates decreased significantly at the upstream face and increased downstream, accompanied by an increase in water mass flux at the upstream face and a decrease at the downstream toe, suggesting dynamic changes in water behavior in response to drawdown. Moreover, the findings unveiled significant correlations between matric suction and time (correlation coefficient of 0.950) and factor of safety and water conductivity (correlation coefficient of 0.750). Conversely, a distinct negative correlation emerged between matric suction and factor of safety (correlation coefficient of −0.864). The study's distinctive insights contribute to our understanding of seepage behavior and dam stability across varied scenarios, offering valuable input for resilient dam construction approaches that will ensure the longevity and effectiveness of these essential structures. [ABSTRACT FROM AUTHOR]

Leakage is one of the major problems facing the functionality and sustainability of dams. It occurs through the embankment body, reservoir, foundation, and abutments. This study was conducted to identify the main causes of the leakage problem at the Dora-1 dam, located in the northern part of Ethiopia. It is an earthfill dam with a height of 43.5 m, crest length of 454 m, and reservoir capacity of 4.67 million cubic meters. Part of the embankment body was wet and swampy up to 20 m high from the ground due to leaking water. Geological investigation, laboratory test of the construction materials (including grain size analysis, specific gravity and water absorption, Atterberg limit, free swell, dispersion, permeability, and shear strength), and electrical resistivity investigation were used to identify and pinpoint the possible causes of the leakage problem. Results of the study show that the favorable geological features responsible for the occurrence of leakage include: (a) geological contact between sandstone and moderately to highly weathered basalt unit at the left abutment, (b) the gravelly sand deposit at the central foundation and (c) dyke outcrop at the river course within the reservoir running in the upstream-downstream direction. Results of laboratory tests for clay core show medium to high compressibility, good to poor workability, and semi-pervious to impervious permeability when compacted. The water absorption and the percentage finer of the filter material don't satisfy the filter criteria and the shell material was found to be semi-previous. The anomalous in the resistivity survey result confirms the situation. Slope stability analysis of the embankment showed instability conditions at full reservoir level. Close follow-up and a downstream stabilization structure, including rock and gravel support, were recommended. [ABSTRACT FROM AUTHOR]

This article deals with the subject of monitoring the settlements of embankment dams, taking as an example Kerrada's dam, located in Algeria, and made of rockfill with a central clay core. To analyse the evolution of the deformations, it proposes a multidisciplinary approach which combines geotechnical measurements of settlements and geodetic measurements of levelling. These two types of measurements are diagnosed by the so-called multi-sensor data fusion (MDF) method. In this method, we use "a first level of fusion" which allows us to estimate the settlements on the surface of the dam. Then this estimation is improved during fusion at "a second level" by introducing an interpolation by artificial intelligence of the radial basis functions of neural networks (AI-RBFN), with three AI-RBFNs algorithms, which are the conventional (Newrb), the exact (Newrbe) and the generalized regression of neural networks (Grnn). To generate the settlements of the entire surface of the dam. The goals of MDF use aims to provide better accuracy, robustness against uncertainty and reliable spatiotemporal integration. However, the appropriate surface interpolation by AI-RBFNs aims to handle cases of insufficiency in observations (spatiotemporal) and low-number sensors. The MDF results obtained, in terms of average displacement value and value of the empirical settlement index (SI), were found to be satisfactory. In addition, the MDF-AI-RBFNs model has achieved an improvement rate in the accuracy of 81% compared to that obtained with the geotechnical data only. These results reinforce the need to continue in the study of the optimization of the MDF model by the heuristic algorithm of AI. [ABSTRACT FROM AUTHOR]

A series of tests of wedge-shaped blocks intended for armoring embankment dams and levees was carried out in a new experimental facility ('Hydraulic Experimentation Facility—Luis Ruano') under quasi-prototype conditions. This unique facility is located in the canal leading to the Laverné reservoir (Zaragoza, Spain) with a maximum vertical drop of 7 m and discharge up to 9 m3 s−1. The aim was to conduct experimental research on technologies to protect embankment dams and dikes against overflowing erosion under quasi-prototype conditions. The results of the tests demonstrate the ability of the WSBs to withstand high unit discharges under extremely negative conditions at the upstream and downstream ends of the armoring. The tests also helped to identify potential failure modes for the armoring blocks. [ABSTRACT FROM AUTHOR]

Hydraulic asphalt concrete is virtually impervious. Hydraulic fracturing due to the generation of pore water pressure can be generally excluded for asphalt facings and asphalt cores in embankment dams. However, when some cracks and/or large voids exist in the asphalt core in dams, hydraulic fracturing could take place during reservoir impounding. Cracks and/or large voids may be caused by either earthquake shaking, large differential settlements during construction and operation, or poor construction quality. Therefore, asphalt specimens with either cracks of different depths or large air porosity were prepared, and a model test apparatus was developed to investigate the possibility of hydraulic fracturing. Model tests were conducted on cylindrical asphalt concrete specimens of 100 mm in diameter and 180 mm in height. The top boundary of the specimens was either prevented (restrained) from moving in the vertical direction or free to move (unrestrained). The model test results for asphalt concrete with cracks under unrestraint conditions were numerically back-analysed. The model test results indicated that the cracks in the asphalt concrete under the restraint conditions could experience an "open–close" progress with increasing water pressure. That suggested that if the asphalt concrete were long, low water pressure would trigger a fracturing through the cracks. Under the unrestraint conditions, low water pressure could cause the asphalt specimens with either cracks or large air porosity to fail. The extensional strains at failure were reduced, and the reductions depended on the magnitude of the crack depth or air porosity. Suggestions are given for designing the asphalt core dams to reduce the possibility of the occurrence of cracks and/or dilations in the core, especially for dams in unfavourable geological and topographical conditions. A specialty contractor is preferable to do the asphalt core job to rule out the possibility of a weak bond between the layers and an air porosity larger than 3.0% in the core. [ABSTRACT FROM AUTHOR]

Sonic drilling, auger drilling, and cable-tool drilling are the preferred methods utilized to drill through levees and embankment dams. Sonic drilling is the most recently developed of the three and has distinct advantages over the other methods. Notably, sonic drilling offers a high rate of advance through most materials while still protecting embankments from erosion and hydrofracturing. The method is not without limitations, as cost and space constraints prevent it from being the most effective choice in some circumstances. [ABSTRACT FROM AUTHOR]

The study examined the intricate relationships between embankment slope configurations, toe drain designs, and drawdown scenarios. It utilized a unique combination of numerical, physical, and mathematical models. The investigation involved 16 numerical models and 8 physical models with distinct characteristics. The research explored the correlations of key parameters: matric suction, horizontal water conductivity, time, and factor of safety. The factor of safety values varied from 0.62 to 1.03 as a result of the different investigated combinations. For instance, a 1:2 embankment slope without a toe drain under instantaneous drawdown led to the factor of safety values ranging from 1.22 to 1.57. Additionally, incorporating elements like a 30 m toe drain and a 1 m per day drawdown rate influenced these values, with extremes recorded from 1.337 to 2.21, shedding light on embankment stability under diverse conditions and configurations. When subjected to a 1 m per day drawdown, water flow rates decreased significantly at the upstream face and increased downstream, accompanied by an increase in water mass flux at the upstream face and a decrease at the downstream toe, suggesting dynamic changes in water behavior in response to drawdown. Moreover, the findings unveiled significant correlations between matric suction and time (correlation coefficient of 0.950) and factor of safety and water conductivity (correlation coefficient of 0.750). Conversely, a distinct negative correlation emerged between matric suction and factor of safety (correlation coefficient of −0.864). The study’s distinctive insights contribute to our understanding of seepage behavior and dam stability across varied scenarios, offering valuable input for resilient dam construction approaches that will ensure the longevity and effectiveness of these essential structures.

A fast reduction of a reservoir level may result in instability of an earth dam caused by the high pore water pressures that remain relatively high in the embankment. Moreover, the dissipation of the accumulated pore water pressures is highly dependent on the permeability of the materials used for the embankment and the storage characteristics of the reservoir. Therefore, in the design of embankment dams, the stability analysis under rapid drawdown loading conditions is an important design case. In this study, the influence of different permeability rates on dam stability under different cases of rapid drawdownwas investigated using the finite element method in SEEP/W and SLOPE/W of the GeoStudio with a case of the Lugoda dam in Ndembera catchment, Tanzania. The modeling process considers the time-dependent hydraulic conditions and the transient flow conditions using different water levels during rapid drawdown for evaluation of the factor of safety. From the 1m per day drawdown rate; the lowest minimum factor of safety value (0.90) was obtained from the 10 -7 m/s material permeability of the upstream zone of the dam. It means that, at a drawdown rate of 1m per day, there is a potential for failure of the embankment if the hydraulic conductivity value will be somewhere below 10 -6 m/s.

Regular surveillance, data acquisition, and visual observation of high embankment dams are extremely important for the stability analysis of these structures. The stability issues that could occur during a dam's lifetime are mainly related to slope instability and internal erosion. The aim of continuous dam security monitoring and field measurement is to identify priority flow paths in the dam body, i.e. cracks and the erosion process. A key parameter for embankment dam stability assessment is the pore water pressure (PWP) response in the clay core. Increasing pore water pressure results in shear strength reduction and can cause dam instability. In this paper, four different models based on artificial neural networks will be developed for pore water pressure prediction in an embankment dam clay core, based on meteorological, hydrological, and geotechnical data. These models will be compared and the model that gives the smallest prediction error will be presented. In the light of climate change, the main objective of this paper is to find the model that can be used for embankment dam stability prediction in extreme weather events.

The maximum yield of 90,000 m3/day from the existing Gubi dam in Bauchi will barely meet the water demand beyond 2030 at an average water use of 100 litres per capita/day. For higher water demand of up to 250 litres per capita/day expected in an urban centre, the existing dam capacity is inadequate, and the demand should grow to 253,102 m3/day by 2037. This is the rationale for this study, which showed the feasibility of a new dam through technical reviews and analysis of topography, hydrology of the site, field and laboratory investigations, computer analyses and designs. Hydrologic simulation of rainfall-runoff processes for 57 years of rainfall data using the Soil Conservation Service (SCS) method gave an annual runoff volume of 59 Mm3 on a stream in Miri, which can be harnessed to assure adequate water supply in the metropolis. This will require the construction of a 25 m high embankment dam. Topographic survey and analysis indicated that the proposed site has good water retention capability. Although net flow adjustment analysis showed a high evaporation loss of up to 13.5 Mm3 annually, seepage loss is expected to be small in view of the underlying basement complex rock formation.

Loading conditions are among the significant determinants of the stability of embankment dams: they need to be carefully investigated during the design phase of the dam construction. Unfortunately, it is almost impossible to investigate the combination of these parameters in-situ. In the current work, the influence of rapid drawdown loading conditions on the stability of the embankment dam was investigated with the help of numerical modeling for a case of the Aktobe dam in Kazakhstan. The seepage analyses were carried out concurrently with slope stability analyses. Mainly, five different drawdown cases were investigated, which are: steady-state, instantaneous drawdown, 5-days drawdown, 10-days drawdown, and 1m per day drawdown rate. In terms of flow type, both steady-state and transient flow conditions were investigated. In general, when the embankment was subjected to the 1 m per day drawdown rate a minimum factor of safety value of 1.486 was retrieved from computations. The factor of safety value is equivalent to a 3.7 % increase from the 10 days drawdown rate, 8.3 % from the 5 days drawdown rate and 48.6 % from the instantaneous drawdown.

An uncontrolled leakage and piping in embankment dams may cause breaching and slope slides. Clarification of the cause of an embankment leakage is also crucial to determine the effective and economical treatment method. However, identification of the source of a leakage in embankment dams is a difficult task since site investigations and computation methods may vary significantly depending on the site geology, topography, and embankment material properties. This paper presents an exemplary distinctive study and treatment methods of a leakage problem of an embankment dam located on seismically active region wherein the site is under the risk of 89 active faults capable of producing magnitudes over 6.0. Calculated slope failure probability of the dam due to the leakage-related saturation of the downstream zone is significantly high as 0.89. Numerical seepage analyses were also performed to determine whether the leakage was related to a piping incident or a filter deficiency. Particularly, bottom outlet valve on/off operations and satellite image approaches and their interpretations enabled the finding that the leakage on the dam occurred due to the bottom outlet deterioration. The deterioration of the bottom outlet resulted in high water uplift pressure into and saturation of the downstream sandyfill beyond the chimney filter. Finally, the study discusses two different treatment techniques: (1) the application of a geomembrane on the upstream face that did not prevent the leakage, and (2) driving an HDPE pipe into the existing steel bottom outlet pipe, a rapid, economical, and effective solution that prevented the leakage. This study provides different evaluations of the reason of the leakage problem and effective treatment process of a bottom outlet which can be useful for other embankment dams having such leakage problems. [ABSTRACT FROM AUTHOR]

Overtopping erosion is one of the main causes of catastrophic failure of earth dam. One of the common preventive methods is to grout or add chemicals to the embankment soil. In this study, nanoclay which is devoid of any environmental detrimental effects was utilized. Erodibility of samples contained nanoclay with 0, 1, and 1.5 weight percent of dry soil and curing time of 0, 7, 14, 28 days were investigated using an image processing technique. To make a comparison between traditional and modern additives, a sample containing bentonite clay with 5 weight percent of dried soil was considered. The results showed positive effect of nanoclay on erodibility reduction of the soil. The sample with 1 percent nanoclay with 14 days curing time showed the highest improvement of the soil erodibility characteristic. Increasing the curing time to 14 days reduced the erodibility of all samples, thereafter it had no significant effect. Comparison of traditional and modern additives reveals that the erodibility of the sample containing 5 percent bentonite clay was about 10 times lower than that of the 1 percent nanoclay. [ABSTRACT FROM AUTHOR]

When dispersive soils are used in the core structure of embankment dams, due to their high erosion sensitivity, they cause internal erosion and cause such dams to collapse. Such soils should be determined at the design stage and not used in the construction of fill dams. Dispersive soils can be determined by physical (Crumb test, double hydrometer test and pinhole test) and chemical (chemical content of the pore fluid) experiments. In this study, as an alternative method, computer models have been developed to predict the dispersibility class of soils with the help of genetic programming (GP) using XRF (X-Ray Fluorescence) analysis results. 66.9% of the 181 data used in prediction models created with Genetic Expression Programming (GEP) are training data; the remainder was used as test data. In computer models where major (SiO2, Al2O3) and minor (MgO, CaO, Na2O, K2O) oxides are used as input data, soils are successfully predicted as dispersive (D) and nondispersive soils (ND) at high rates. The most successful forecasting model is the one that consists of SiO2, Al2O3, MgO, CaO and Na2O input data in the entire data set. [ABSTRACT FROM AUTHOR]