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Internal geomembranes are alternatives to traditional clay cores and upstream geomembranes. In this research, numerical analysis is performed to assess the impact of leakage through 2-D geomembrane defects such as slits, tears and faulty stitches. Five possible applications of internal geomembranes and an upstream geomembrane were modelled to compare their performance with that of clayey cores. The results show that use of upstream or internal geomembranes significantly decreases the pore pressure developed at the downstream slope thus improving its stability. The effects of leakage through both internal and upstream geomembranes on the stability of embankment slopes under steady state and drawdown at a rate, conditions were analysed. Stability of the downstream slope reduces significantly due to defective geomembranes depending on the defective seam locations. Drawdown simulations show that internal geomembranes can cause instability in steep upstream slopes of dams. [ABSTRACT FROM AUTHOR]

The Danjiangkou hydropower station is a water source project for the middle line of the South-to-North Water Transfer Project in China. The dam is composed of riverbed concrete dam and earth rock dam on both banks, with a total length of 3442 m. Once the dam is wrecked, it will yield disastrous consequences. Therefore, it is very important to evaluate the dam safety behavior in time. Based on the long-term and short-term memory (LSTM) network, the deformation prediction models of the embankment dam of the Danjiangkou hydropower station are constructed. The models contain two LSTM layers, adopt the rectified linear unit function as the activation function and determine the super parameters of the models with Bayesian optimization algorithm. According to the settlement monitoring data of LD12ZT01 measuring point (dam crest 0 + 648) on the left bank of the embankment dam of the Danjiangkou hydropower station from July 2013 to March 2022, the LSTM and bidirectional LSTM models are constructed. In total, 80% of the monitoring data are taken as the training set data and 20% of the monitoring data are taken as the test set data. The mean absolute error, root mean square error and mean square error for the test set are 0.42978, 0.56456 and 0.31873 for partial least squares regression (PLSR), 0.35264, 0.47561 and 0.22621 for LSTM and 0.34418, 0.45400 and 0.20612 for bidirectional LSTM, respectively. The results show that the bidirectional LSTM model can obtain better deformation prediction value than the LSTM model and the PLSR. Then, the bidirectional LSTM model is used to predict the settlement value of LD16YT01 measuring point (dam crest 0 + 658) on the right bank, and the mean absolute error, root mean square error and mean square error for the test set are 0.5425, 0.66971 and 0.4520, respectively. This shows the bidirectional LSTM model can effectively predict the settlement value of the embankment dam of the Danjiangkou hydropower station. [ABSTRACT FROM AUTHOR]

Analyzing the seepage and stability analysis of embankment dams built on deep overburden layers is an essential aspect of dam design and operation and is of significance to ensure the safe and effective operation of geotechnical and hydraulic structures in reservoir sites. However, in most existing studies, the seepage and dam slope stability were analyzed separately without considering the interaction between the two fields; thus, the actual operating state of the dam could not be accurately reflected. In this paper, an embankment dam located in Yulin, Shaanxi Province, China, built on a deep overburden layer, was selected as a case study for illustration. Considering the hydrogeological and engineering design information of this project, a three-dimensional fine finite element model reflecting the main characteristics of the reservoir site was established. COMSOL Multiphysics software, which is particularly suitable for multifield coupling calculations, was used to conduct a multifield coupling analysis of the safety state of embankment dams on deep overburden layers by modifying and customizing the porous media and subsurface flow module and solid mechanics module. The method to solve the multifield coupling problem was clarified. Notably, the proposed coupling model involved many parameters, which might introduce uncertainties into the model, thereby requiring considerable work for calibration. Therefore, the Morris method was used to identify the sensitivity of the coupled model parameters to the output results. The results show that the established multifield coupling model can effectively address the seepage and stability problems of embankment dams on deep overburden layers, and the dam can safely operate under the existing design scheme. Even under the condition of a magnitude VIII earthquake at the check flood level, the dam does not experience seepage and slope failure. The safety factor of sliding failure of the dam slope is mainly influenced by the internal friction of saturated soil (φs), material cohesion (c), internal friction of unsaturated soil (φu), soil density (ρs) and Poisson's ratio (ν), while the influence of the seepage parameters is generally small. The methodology and results derived from this study can provide technical support and reference to evaluate the safety in terms of the seepage and anti-sliding stability of similar projects. [ABSTRACT FROM AUTHOR]

This study investigated the potential influence of operating water levels and loading conditions on the slope stability of an embankment dam. Four different operating reservoir levels (normal, reduced, embankment height, and overflow) were considered in the study. Numerical modeling was used to investigate the problem in the case of the Chardara dam within the Syrdarya catchment in Kazakhstan. Based on the drawdown rates and operating conditions, minimum factor of safety values ranging from 0.56 (total failure) to 2.5 were retrieved. Furthermore, a very high correlation was observed between drawdown days, the minimum factor of safety values, the maximum factor of safety values, and pore-water pressures, with correlation coefficients ranging from 0.561 to 0.997 (strong to very strong correlation). On the other hand, the highest negative correlation of 0.997 was observed between the minimum factor of safety values and pore-water pressures. Additionally, based on the results from the analysis of variance, three reservoir operating levels (normal, embankment height, and overflow) resulted in p-values less than 0.05, indicating that the variations in the factor of safety values from the drawdown rates were statistically significant. The findings of this study demonstrated that, not only may the drawdown rate be detrimental to the embankments, but that different operating levels can also affect slope stability in different ways. [ABSTRACT FROM AUTHOR]

The rock and soil body composition of the dam abutment is complex, and the structures are quite different. Under the action of hydrodynamic and hydrostatic pressure, the safety problem of multiple leakage in the joint area, the seepage investigation of a reservoir dam is taken as the research object, the spatial location information and causes of dam hidden dangers are explored by means of measurement, geophysical exploration, drilling and hydrogeological test. The survey results show that the UAV photography technology clearly shows the location relationship between the leakage point, the collapse area and the landslide body, so as to guide the geophysical prospecting work. The focus is the left dam section of the dam. Parallel electrical method technology has the ability to quickly obtain the resistivity distribution of the whole dam. Combined with transient electromagnetic technology, the location and area of the verification borehole can be further determined. Drilling in the section of the pile number K0-000-0+040 m reveal that the dam foundation is mainly composed of block stones, and the electrical conductivity relationship between drilling, collapse area and leakage point water is established through tracer test. It is deduced that leakage is caused by the failure of the inclined wall impervious body in front of the original landslide and the formation of the dam leakage channel in the block stone layer. According to the detection research results, the path and distribution range of the dam leakage channel are determined, which provides a target area for the directional seepage control of the reservoir dam leakage. [ABSTRACT FROM AUTHOR]

Repeated rapid drawdown (RDD) and rapid rise in water level during extreme events lead to the progressive development of plastic strain zones within the earth embankments with subtle, rather than obvious, visible signs of distress. The traditional approach within the framework of limit equilibrium does not account for accumulated permanent deformation with repeated hydraulic loading. Work presented herein is focused on quantifying the level of deviatoric strain, in terms of key surface deformation and distress level of earth embankment slopes, with repeated hydraulic loading. A simple linear relationship between the deviatoric strain and surface deformation at the toe of the slip surface is proposed as a function of the geometry of the slope for rotational sliding. This relationship is applied using the stress-strain data obtained from conventional triaxial testing and provides a simple means to estimate the ultimate performance limit state that corresponds to the onset of embankment slope instability. Results from a parametric study show good agreement between the numerical results and proposed analytical criterion. The proposed criterion is also compared with data from field cases reported in literature by others, and reasonably good agreement with onset of failure is obtained. Results from applying the proposed model to the case studies indicate the applicability of the proposed approach as a framework for various loading conditions, slope geometries, and material properties. [ABSTRACT FROM AUTHOR]

When filling embankment dams in cold regions, engineers must solve two freeze—thaw cycle (FTC)-induced soil problems. First, compacted soil constituting the dam is subjected to the FTC during dam construction. Second, loose soil material (LSM), which is subjected to the FTC, fills the dam. To investigate the effects of the aforementioned two problems on the hydraulic conductivity of compacted clayey soil, a series of permeation tests on clayey soil compacted before and after FTC were conducted in this study. The results showed that for the first problem, the hydraulic conductivity of compacted clayey soil subjected to one FTC significantly increases by two to three orders of magnitude because FTC-induced cracks can cause preferential flow in the permeation process. For the second problem, when the FTC number is less than a critical number, the FTC of the LSM may result in the development of united soil particles, thereby increasing the effective porosity ratio and hydraulic conductivity of the compacted soil. It was discovered that the hydraulic conductivity of compacted soil can increase by one to three times when the LSM is subjected to 10 FTCs. When the FTC number exceeds a critical number, the effective porosity ratio and hydraulic conductivity of the compacted soil may decrease with the FTC of the LSM. This should be investigated in future studies, and the results can be used to improve engineering management processes when filling embankment dams during winter in cold regions. [ABSTRACT FROM AUTHOR]

Despite being potential historical sites, old embankment dams are subjected to many stability challenges due to many factors, including a lack of sufficient stability assessment tools by the time the dam was built and changes in embankment material properties induced by natural and human activities. Therefore, with the current advancement in technology is of great importance to investigate the state of old embankment dams under different potential loading conditions. The stability challenges become of more significant concern when the embankment is subjected to a rapid drawdown loading scenario. In this study, the Samarkand dam located in Karaganda province in Kazakhstan which was put into operation in 1941 is investigated in terms of seepage and slope stability with the help of numerical modelling. Both steady and transient (rapid drawdown) flow conditions are taken into consideration. e finite element method-based modelling is achieved using SEEP/W and SLOPE/W of the GeoStudio software. From the analysis results, it was observed that the old dam can be subjected to a potential failure under rapid drawdown conditions as the minimum factor of safety values were decreasing with the increase in the drawdown rates. For instance, the minimum factor of safety from the instantaneous drawdown rate was equivalent to 32.85% less than the factor of safety retrieved from the long-term steady-state conditions. Also, from Analysis of Variance (ANOVA), a p-value of 9.97× 10-29 was obtained after subjecting the factor of safety values from instantaneous, 5 days, 10 days, and 1 m per day drawdown rates to ANOVA, indicating that the factor of safety differences among the analyzed drawdown rates were statistically significant. [ABSTRACT FROM AUTHOR]

Copyright of SDU Journal of Engineering Sciences & Design / Mühendislik Bilimleri ve Tasarım Dergisi is the property of Journal of Engineering Sciences & Design 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.)

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.

Embankment dams are one of the most important geotechnical structures that their failures can lead to disastrous damages. One of the main causes of dam failure is its slope instability. Slope Stability analysis has traditionally been performed using the deterministic approaches. These approaches show the safety of slope only with factor of safety that this factor cannot take into account the uncertainty in soil parameters. Hence, to investigate the impact of uncertainties in soil parameters on slope stability, probabilistic analysis by Monte Carlo Simulation (MCS) method was used in this research. MCS method is a computational algorithm that uses random sampling to compute the results. This method studies the probability of slope failure using the distribution function of soil parameters. Stability analysis of upstream and downstream slopes of Alborz dam in all different design modes was done in both static and quasi-static condition. Probability of failure and reliability index were investigated for critical failure surfaces. Based on the reliability index obtained in different conditions, it can be said that the downstream and upstream slope of the Alborz dam is stable. The results show that although the factor of safety for upstream slope in the state of earthquake loading was enough, but the results derived from probabilistic analysis indicate that the factor of safety is not adequate. Also the upstream slope of the Alborz dam is unstable under high and uncontrolled explosions conditions in steady seepage from different levels under quasi-static terms. [ABSTRACT FROM AUTHOR]

Due to the observed improvement of machines and mechanisms and the process equipment thereof used during the construction of clay-cement concrete slurry walls by means of bored-secant piles, the author proposes to extend the range of considered designs of impervious elements of embankment dams by adding modifications with an arch diaphragm and an inclined diaphragm. Performed surveys and comparisons with the traditional design (vertical wall) allowed to identify the main trends of the influence of using the effect of clay-cement concrete diaphragms inclination and the arch effect on the change in the strain-stress state of the embankment dam — diaphragm system. Consideration of the clay-cement concrete diaphragm designs proposed by the author in designing embankment dams will allow extending the range of possible application of this technical solution. It was established that there is a possibility to optimize the existing technical solutions for the clay-cement concrete diaphragm embankment dams if they are designed with due consideration of not only the assignment of clay-cement concrete strength and strain-stress properties, but also taking into account the change in configuration of the diaphragm itself.

This study investigated the potential influence of operating water levels and loading conditions on the slope stability of an embankment dam. Four different operating reservoir levels (normal, reduced, embankment height, and overflow) were considered in the study. Numerical modeling was used to investigate the problem in the case of the Chardara dam within the Syrdarya catchment in Kazakhstan. Based on the drawdown rates and operating conditions, minimum factor of safety values ranging from 0.56 (total failure) to 2.5 were retrieved. Furthermore, a very high correlation was observed between drawdown days, the minimum factor of safety values, the maximum factor of safety values, and pore-water pressures, with correlation coefficients ranging from 0.561 to 0.997 (strong to very strong correlation). On the other hand, the highest negative correlation of 0.997 was observed between the minimum factor of safety values and pore-water pressures. Additionally, based on the results from the analysis of variance, three reservoir operating levels (normal, embankment height, and overflow) resulted in p-values less than 0.05, indicating that the variations in the factor of safety values from the drawdown rates were statistically significant. The findings of this study demonstrated that, not only may the drawdown rate be detrimental to the embankments, but that different operating levels can also affect slope stability in different ways.

Embankment rockfill dams are the most common dam construction types used in the world today. One third of all embankment dam failures are caused by dam slope instability. The dam is stable when the slopes are stable. Slope safety of the dam is assessed through pore and total pressure data analysis registered on pressure measurement cells installed in the dam. During the service life of a dam, one or more cells may malfunction after years of operation. Cell replacement implies economically unjustified high costs and is usually technically impossible and high risk. In this paper, the problem of a malfunctioning cell with a small available dataset is analysed. A new method for pore pressure prediction on malfunctioning cells has been developed using several successive artificial neural networks (ANNs) to obtain high accuracy of the predicted values. The results show that these predicted values are more precise than values we could have obtained using only one artificial neural network for prediction. [ABSTRACT FROM AUTHOR]

Traditional construction practices showed that asphalt core construction rate was commonly 2 layers/day (0.4 m/day) before the year 2000. More than 2 layers/day has been concerned as it would be difficult to compact the third layer to reach the required density (void content of maximum 3%) as the sublayers are soft. However, the Zhaobishan embankment dam was located at a very special dam site and high construction rate was required. Based on reviewing successfully high construction rates of asphalt core test section with 0.8 m/day (4 layers/day) and 0.9 m/day (3 layers/day) extensive laboratory tests and 4 trial test sections near the Zhaobishan dam site were carried out to gain asphalt mix parameters and construction techniques before constructing the asphalt core. The 63.6 m high asphalt core for the 71 m high dam was completed in 159 days with intensively quality control during construction. The maximum construction rate was 0.92 m/day (4 layers/day). The dam with asphalt core has performed well since the completion year 2005. The dam case study has documented that asphalt core dam can be constructed in a high rate without compromising core quality. Based on practical experience, field observations, and investigations in recent years, one can now build asphalt core dams faster and more economically than before. The fact that one can significantly reduce the probability of overtopping during construction by increasing the construction rate, may be an important point in many situations.

In recent years, as the number of reservoir embankments constructed has increased, embankment failures due to cracks in aging conduits have also increased. In this study, a crack in a conduit was modeled based on the current conduit design model, and the risk of internal erosion was analyzed using a large-scale model test and three-dimensional deformation–seepage analysis. The results show that when cracks existed in the conduit, soil erosion and cavitation occurred near the crack area, which made the conduit extremely vulnerable to internal erosion. Herein, a model is proposed that can reduce internal erosion by applying a layer of sand and geotextiles on the upper part of the conduit located close to the downstream slope. In the proposed model, only partial erosion occurred inside the conduit, and no cavitation appeared near the crack in the conduit. The results suggest that internal erosion can be suppressed when the water pressure acting intensively on the crack in the conduit is dispersed by the drainage layer. To validate these results, the pore water pressure, seepage line, and hydraulic gradient were investigated to confirm the erosion phenomenon and reinforcement effect.

The safety in operation of the hydrotechnical constructions, in the case of the retention ones from local materials, is a particularly important issue, involving numerous technical, economic and social implications. The phenomenon of failure, an event of utmost importance, is particularly complex both in terms of genesis and development. Leaving aside the exceeding of the resistance capacity of the materials, the partial or total failures of the earth dams and / or boulders, the most numerous due to the accessible materials, can be due to infiltrations through the construction body, generating suffusions and leaks. The paper presents a 2D numerical modeling of the liquid flow transit on the Gladna River, Timiș County, Romania, in the Surduc accumulation section, at the appearance of an accidental flood wave. The reservoir has a maximum volume of over 51 million cubic meters and is created by an embankment dam with a concrete mask with a maximum height of 35 m. The peak flow hydrograph used is similar with the peak flow hydrograph of April 2012 flood event. The discrete numerical modeling of the transition of flood event is made with the help of the HEC-RAS 5.0.7 software package, assuming a fictitious scenario of accidental overtopping of the embankment dam, which determines a possible failure of this hydraulic structure. The geometric development of the dam breach is estimated with the help of a specific additional facility from the employed software. Apart from the position of the yield section and its final geometric shape, the numerical simulation estimates the development over time of specific phenomenon’s hydraulic parameters - flows, levels, velocities - in all points of the modelled domain. [ABSTRACT FROM AUTHOR]

Water seepage affects dam stability and loss of water from reservoirs. Consequently, seepage is an important problem in the design, implementation, and operation of embankment dams. One type of embankment dam is a non-homogeneous (zoned) dam with a clay core. Water passes through the core of the dam and loses much of its energy due to friction. Zoned embankment dams can be designed and implemented with inclined or vertical cores. In this study, the performance of inclined and vertical cores are compared using numerical models to simulate the seepage and hydraulic gradients. Also, the Limit of Equilibrium Method is used to calculate slope stability. The permeability ratio of the dam shell to the clay core is a variable. The result of this study shows that seepage with a vertical core is less than that with an inclined core. Meanwhile, the factor of safety for upstream slope failure is higher (about 55.5%) for the embankment with an inclined core compared to the vertical core case. Also, comparisons were made using different methods to calculate the stability of the slope. The Bishop's method showed the highest safety factor and the Fellenius' method predicts the lowest safety factor. [ABSTRACT FROM AUTHOR]

It is of great significance to study the process and cause of embankment dam breach in order to ensure the dam safety. In this paper, the overtopping failure mode of embankment dam is selected as the research object, and the cellular automata (CA) method is introduced to explore the development law and influencing factors of the overtopping failure mode. Based on the physical and mechanical characteristics of embankment dam and the energy evolution law of the dam soil failure process, this paper discusses the realization method of CA for simulations of dam body heterogeneity, soil anisotropy, stress environment, etc., and proposes the determination method of cellular failure threshold, energy dissipation rate and energy transfer coefficient. Afterward, the loading mode of the CA model is determined based on the relationship between generalized energy and force deformation of the dam soil. Then, energy criterion for dam erosion failure and mechanical criterion of breach slope failure are put forward. Finally, the CA model is applied to a practical project so as to analyze the development and cause for scour depth and width of the overtopping failure breach, and the influence of overtopping water level and downstream slope ratio on the development of breach. [ABSTRACT FROM AUTHOR]

The asphalt core itself is a no-joint water barrier in embankment dams and is connected to the concrete plinth on the bottom of the core. A reliable asphalt core-plinth connection is crucial and must remain watertight when the core deforms due to deformations in the embankment and foundation and due to reservoir water pressure. A large number of tension tests were conducted to determine the best ratios, joint thickness and suitable additives for the sandy asphalt mastic (SAM) mix used for the connection. With the ratios of bitumen to filler to sand of 20%:35%:45% and by adding 4% SBS in the bitumen, one got a very suitable composition for the asphalt core-plinth connection in tensile conditions. Model tests were conducted to study the connection behavior when subjected to large shear displacements and high water pressure. The joint model test results indicate that the plane-surface plinth, curved-surface plinth, and plinth with or without copper water-stop showed no significant difference for the connection in the joint shear behavior. However, plinth with copper water-stop is suggested to enhance its tensile and shear behavior.

This paper presents simulations of water seepage within and under the embankment dam of Lake Kowalskie reservoir. The aim of the study was to compare seepage calculation results obtained using analytical and numerical methods. In April 1985, after the first filling of the reservoir to normal storage levels, water leaks was observed at the base of the escarpment, on the air side of the dam. In order to control seepage flow, drainage was performed and additional piezometers installed. To explain the causes of increased pressure in the aquifer under the dam in May 1985 a simplified calculation of filtration was performed. Now, on the basis of archived data from the Department of Hydraulic and Sanitary Engineering using 3D HYDRUS STANDARD software, the conditions of seepage under the dam have been recreated and re-calculated. Piezometric pressure was investigated in three variants of drainage, including drainage before and after modernization.

This paper presents a stability parametric analysis of a 59m high embankment dam. The analysis was performed in order to evaluate the minimum values of strength parameters that satisfy the stability requirements of the dam. The parametric analysis was conducted for three main zones of the dam: upstream shell, core, and downstream shell, which consisted of sandy gravel, clay, and random fill respectively. The friction angles of these materials were gradually decreased in order to represent different soil conditions. It was observed that stability requirements for the end of construction and after the filling of the reservoir could be satisfied if friction angle values of the sandy gravel and the random fill are 34° and 32°, instead of 37° and 34°. However, the value of the core's cohesion could be utilized as 30° without any reduction so that the dam could be safe after the filling of the reservoir. The results of this study could be beneficial to practicing engineers for the design of safe and economical embankment dams. [ABSTRACT FROM AUTHOR]

For the settlement computation of an embankment dam, the soil stiffness is of great importance. Unfortunately, due to the lack of funds allocated for geotechnical investigation, stiffness parameters are commonly not evaluated as compared to strength properties. As a result, this may create hindrance in the use of advanced constitutive models such as Hardening Soil Model (HSM). In this study, the settlement with respect to depth and long term settlement of an embankment dam computed with Mohr-Coulomb Model (MCM) is compared with that of HSM applied to foundation soil only with limited data on stiffness. The results show that the MCM overestimated settlement in comparison with HSM. The settlement increment of MCM, in comparison with HSM, at the crest and at the depth of 120m was 53% and 82% respectively after the filling of the reservoir. The settlement computed with MCM and HSM were 2.9% and 1.35% of the dam height. It can be interpreted that the settlement predicted with MCM is unrealistically high due to the single constant value of modulus of elasticity (MOE), while the predictions of HSM are in agreement with the literature. In addition, the long term settlement computed using MCM is about 59% higher than that of HSM for the condition after the filling of the reservoir. This paper shows that the settlement of an embankment dam could be predicted reliably by using HSM even when a limited number of stiffness data is available. [ABSTRACT FROM AUTHOR]

In this study, numerical analysis of an embankment dam was carried out to predict settlement behavior with the use of the Mohr-Coulomb Model (MCM) and of the Hardening Soil Model (HSM). The MCM was applied to all material zones of the dam and the HSM was used for four major material zones that occupied significant volume. The settlement response of the dam was similar for MCM and HSM for three material zones (clay core, sandy gravel and random fill), each having a modulus of elasticity (MOE) in the range of 25000 to 50000kPa. However, it was found that after the end of the construction, the MCM showed about 57% and 50% more settlement as compared to HSM when MOE of sandy siltstone varied from 70000 to 125000kPa respectively. The results regarding the dam settlement predicted with the HSM are in agreement with the findings in previous studies. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering Geology / Gongcheng Dizhi Xuebao is the property of Journal of Engineering Geology 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.)

In the context of verification of civil engineering structures stability and determination of sliding surface and safety factor, a careful analysis of several parameters was carried out to guarantee their safety against failure. To quantitatively forecast failure scope, the embankment dam located on Oued Rhiss in the province of Hocemia is chosen as the model of this study. A static stability analysis is performed by using the Slope/W software. A parametric study performed to evaluate the influence of dam's height, the height of water in the reservoir and the length of drains on the safety coefficient and pore pressures. Reliability analysis elaborated by using the Comrel application, and it allows to statistically quantifying the probability of failure by employing the Monte Carlo distribution. Results show that the dam structure has some weak zones and not strong enough as the safety factor is less than one, it is related to structure's parameters and the drainage system. [ABSTRACT FROM AUTHOR]

Torrential rainfall has a detrimental impact on the stability of soil-based agricultural embankments due to seepage and slope failure. The impact on the stability of an embankment due to rainfall patterns is specific to the geography, topography, and geometry of the embankment. However, this stability has not been widely assessed and updated with respect to new climate regimes. In this study, the slope stability of an agricultural embankment was evaluated based on five synthetic rainfall patterns derived from actual heavy rainfall events. The rainfall patterns were generated based on common patterns of rainfall hyetographs used in hydrological design and practice. The stability of the embankment was computed using the limit equilibrium method. Results of the stability analyses revealed time-series slope instability under rainfall patterns, and particularly the rainfall pattern that caused the most instability to the embankment was identified. Therefore, reassessment of the stability of the embankment in potential areas prone to heavy rainfall and flooding is beneficial to the preparation of early warning and emergency planning and preparedness as countermeasures for mitigating sediment-related hazards and disasters. [ABSTRACT FROM AUTHOR]

A provision of impervious blanket is investigated aiming to reduce seepage and to increase embankment dam's stability. The investigation generates sufficient data for typical 2D embankment dam cross-sections by numerically solving a wide range of configurations of a provision of upstream blanket. The generated data comprise the correlation between seepage and the various configuration parameters in terms of upstream blanket thickness and length, effects of anisotropy of bed material, foundation depth, and permeability. These data-sets were used to develop design charts, regression, and ANN models. Results showed that application of impervious of blanket in upstream of the earthen dam at appropriate length and thickness is effective in reducing seepage and thereby increasing dam stability. Performance of ANN was excellent in prediction of seepage. [ABSTRACT FROM AUTHOR]

Suffusion, as one of the main internal erosion processes in earth structures and their foundations, may increase their failure risks. The paper aims at presenting a general method to assess the suffusion susceptibility of core soil samples belonging to zoned hydraulic embankment dams. On one hand, the suffusion susceptibility of the soil samples is evaluated by an erosion resistance index. Thanks to existing statistical analyses, the erosion resistance index is estimated from several soil parameters that can be easily measured in situ or in laboratory during the construction of a dam. On the other hand, the saturated hydraulic conductivity of the soil samples is evaluated based on the amount of fines content and on available construction data. Moreover, the power dissipated by the flow is inferred based on the saturated hydraulic conductivity and simplified fluid boundary conditions. The combined consideration of the erosion-resistant index and of the power dissipated by the flow permits to identify zones characterised with a relatively larger suffusion potential (lower erosion resistance index and larger power than their respective average). Throughout, the method is applied to a particular zoned dam with a till core, from Northern Quebec, as a proof of concept. [ABSTRACT FROM AUTHOR]

Seismic design of an embankment dam is a vital step in the design procedure of this important infrastructure. Deterministic approaches such as quasi-static and Newmark method have been employed to evaluate slope stability of embankment dams. However, the variables required for a slope stability analysis, e.g. soil strength, pore pressure and loading parameters involve uncertainties which cannot be handled in the traditional deterministic methods. As an alternative, reliability analysis might be conducted to assess reliability indexes and the related failure probability of embankment dams. In this study, based on probability theories, a reliability analysis is performed to evaluate the seismic stability of an embankment dam (i.e., Gotvand dam) constructed in Iran. The probability of failure under seismic loading is considered for different sources of uncertainties involved in the problem, including uncertainty of loading, and the friction angle of core material as a strength parameter. Employing some statistical parameters, dynamic analysis is performed to determine the influence of friction angle variation on seismic slope stability. Significant pore pressure may build-up during cyclic loading, especially, when mixed clay (mixed clay and gravel) constitutes the dam core. Also, an undrained behavior of core materials has a great importance. Therefore, to estimate the effect of pore pressure build-up during seismic loading, two types of core materials (pure clay and mixed clay) are considered in this research. The results of dynamic analysis by finite element method are used to obtain the critical surface and acceleration in the embankment. Then, Newmark approach is employed to calculate the permanent displacement of the dam. Finally, reliability analysis is conducted and seismic performance of Gotvand dam during the earthquakes is investigated. [ABSTRACT FROM AUTHOR]

Reinforced concrete core dams can be an alternative solution to conventional dam designs either for permanent impounded reservoirs or flood protection and flood-retaining dams. Dams of this type have been constructed in Austria for various reasons and have shown good behavior during operation. For a better understanding of the load-deformation behavior of this type of dams during construction and impounding, numerical simulations were carried out. The interaction between the thin reinforced concrete core and the dam fill material as well as the influence of fill material properties and other main parameters, such as the roughness of the concrete surface and bedding conditions of the concrete core, on the deformation behavior of dams were examined. The results show that high compressive stress is mainly induced by arching effects in the dam body during construction. During the reservoir impounding, the compressive stresses in the core are reduced significantly while the bending moment in the core footing increases. The results also show that the maximum bending moments occur at the core footing and can be significantly reduced by design improvements. The findings in this study can provide general design recommendations for small dams with a central concrete core as a sealing blanket.

Dam-break due to overtopping is one of the most common types of embankment dam failures. During the floods in August 2002 in the Czech Republic, several small dams collapsed due to overtopping. In this paper, an analysis of the dam break process at the Luh, Velký Bělčický, Melín, and Metelský dams breached during the 2002 flood is presented. Comprehensive identification and analysis of the dam shape, properties of dam material and failure scenarios were carried out after the flood event to assemble data for the calibration of a numerical dam break model. A simple one-dimensional mathematical model was proposed for use in dam breach simulation, and a computer code was compiled. The model was calibrated using the field data mentioned above. Comparison of the erodibility parameters gained from the model showed reasonable agreement with the results of other authors.

The asphalt core is located between the upstream and downstream transition zones that are simultaneously placed and compacted in the central part of the embankment dam to form a strong interlocking asphalt core–gravel transition zone (AC-GTZ) interface. The asphalt core usually settles a little more than the transition zones during dam construction, and AC-GTZ interface shear displacements develop. Shear tests were conducted in the laboratory to investigate the interface behavior. Test results show that the AC-GTZ interface was gradually deformed up to a shear displacement of 60 mm, but the properties of the asphalt surface layer did not deteriorate. The integrity of the asphalt core would be better maintained if a sliding layer is placed between the core and the transition zone. [ABSTRACT FROM AUTHOR]

The paper presents a way of studying the water infiltration at the Motru embankment Dam (river ballast fill, clay core sealing) by a 3D numerical model covering the deficient right supporting bank. Since due to sealing imperfections the reservoir runs under level restrictions, the calculations were performed in two stages. First, the model was set up and checked for the existing running situation and then it was endowed with a proposed supplementary ground sealing element that would allow the reservoir running at its designed full capacity. The final goal of the study would be to estimate the maximum appropriate value of the water exfiltration discharge for a dam safety operation under the load given by the originally designed water level. This parameter may than be considered as representative for the expected deep sealing quality, under the required condition of accepting an exfiltrated water turbidity below the value pointed out by stored water. [ABSTRACT FROM AUTHOR]

This paper evaluated the risk of reservoirs collapse caused by nature-flood-based dam overtopping using a Bayesian network. Probabilities of single and cascade reservoirs collapse were calculated for reservoirs in Sichuan Province. The analysis demonstrates that Bayesian network is intuitive and user-friendly to investigate the risk of reservoirs collapse under multiple risk sources. A same conditional dam overtopping probability magnitude of 10-6 is derived, indicating a low risk of single reservoir dam overtopping. However, the conditional probability of dam overtopping is over 0. 8 when the water storage level is higher than normal, meaning there is a high probability of dam overtopping under this condition. [ABSTRACT FROM AUTHOR]