Zoned Earth Dam Research Articles

Seismic intensity measures and predictive equations for the evaluation of earthquake—induced crest settlements of earth dams

AbstractIn this paper the results of 2D dynamic finite element analyses of a zoned earth dam are presented and discussed with the aim of detecting proper intensity measures able to describe the variation of the crest permanent settlement with the characteristics of the input ground motion. A large set of horizontal components of earthquake records has been selected and used as input motion considering both upstream and downstream directions. This allowed to explore the activation of plastic mechanisms in the dam embankment and the amplification of the horizontal accelerations. Starting from the analysis results, two original intensity measures, related to the amplitude, energy and frequency content of the input motion, have been detected and original empirical predictive formulas have also been derived to estimate the permanent crest settlement of the dam. The effectiveness of the proposed intensity measures and the reliability of the novel relationships between these intensity measures and earthquake‐induced permanent crest settlements have been checked against (i) numerical results of further dynamic analyses carried out for the same dam using additional sets of input motions, (ii) numerical results available in the literature for two other earth dams and (iii) field data relative to the crest settlements induced in four earth dams by two recent large earthquakes. The whole set of analysis results allowed defining an empirical equation that appears as a promising general predictive tool for the earthquake‐induced crest settlement of earth dams.

Coupled hydro-mechanical modelling of the seismic response of a zoned earth dam

Coupled hydro-mechanical modelling of the seismic response of a zoned earth dam

Seismic response analysis of a zoned earth dam including vertical input motion

Seismic response analysis of a zoned earth dam including vertical input motion

Slopes Stability Simulation of the Proposed Makhool Dam Against Earthquake Action

This study was designed to analyze the stability of the slopes of the proposed Makhool dam under the influence of the highest seismic acceleration experienced by the dam area since (1997-2022), which is 0.29g with a degree of 7.3ML, due to the earthquake that struck most of the cities of Iraq in 2017. Makhool Dam is a zoned earth dam that is proposed to be built on the Tigris River in north Iraq with length of 3670 m. The study was carried out using Geoslope programs, which used the finite element method. The stability of the dam slopes were analyzed under the influence of the earthquake for three cases, the first at the end of construction (the reservoir is empty), and the second at the maximum level of the reservoir (152.15 m), As for the third, in the case of rapid emptying of the reservoir . The results indicate that the seismic safety factors for the upstream and downstream slopes of the dam are stable and correspond to the minimum acceptable safety factors for the Makhool Dam project. With the exception of the case of the earthquake coinciding with the case of the rapid emptying of the reservoir, where critical stability or collapse of some parts of the upstream slope of the dam may occur, and this case is rare.

Effect of zones' dimensions and geometry on seepage through zoned earth dams

The seepage study through earth dams is very essential for the design and construction processes of such dams to ensure the needed safety and efficient performance. The present study focuses on the seepage flow through zoned embankment dams by introducing a numerical analysis using the Seep/w numerical model. The main objective of the study is to investigate the different effects of the dam zones' thickness and side slopes on seepage through such dams to achieve the most suitable dimensions and geometry of the different zones. First, the Seep/w is used to analyze the problem of seepage through earth dams with an internal core. The present obtained results and the results of other previous experimental and analytical studies are almost close to each other. The present work proves that the best relative thickness of the inner, transition, and outer zones (t1:t2:t3) according to the minimum seepage and cost of the used materials is 2:1.5:1.5 respectively. At the same time, it is proven that the reasonable optimum side slopes (H:V) of the inner, transition, and outer zones are 1:1.75, 1.25:1, and 3.75:1 respectively.

Effect of Core Geometry on Earth Dam Slope Stability

Embankment dams are widely constructed due to their suitability with different types of foundation, and it is constructed from the available material at the site. A zoned earth dam consists of a clay core at the center to control seepage supported by a shell. This paper investigated the impacts of side slopes, top width, and shape on upstream and downstream slope stability during different cases. Slide 6.0 software was used to evaluate the factor of safety of side slopes of an earth dam, and its result was validated. Different side slopes range from 0H:1V to 2 H:1V, and crest widths from 3m to 10 m were examined. In addition, for the slanting core case, several cases with varying angles of inclination were provided. The results indicated that by increasing the side slopes of the core, the factor of safety was reduced, especially in the steady state and rapid drawdown conditions. Increasing the top width also reduced the safety factor in the steady state condition. This reduction was because the core material had lower shear strength than the shell material. In addition, in a steady state and rapid drawdown conditions, the cohesion of core material sharply reduced. Compared with the vertical case, increasing the slanting core slopes influenced the slope stability insignificantly during the steady state. The slanting core had benefits in the steady state when the reservoir was full since, in this case, increasing core side slopes affected the slope stability insignificantly. The maximum core side slope in the earth dam and maximum top width, which insignificantly affected the dam’s slope stability, were 0.8:1 and 5 m, respectively.

Effect of Core Shape and its Side Slopes on Seepage Quantity of Zoned Earth Dam

Seepage is the main problem of earth dams; most failures are occurred due to excessive amount ofseepage. In zoned earth dams clay core is provided to minimize seepage quantity and its dimensions andshape has great influence on seepage quantity. In this study seepage through earth dam with vertical andslanting core case were analyzed for different side slopes and top width. For vertical core cases differentside slopes ranges from 0H:1V to 2H:1V and different top width from (3-10) m were analyzed. Due to lowerpermeability coefficient of core material seepage discharge reduced as side slopes and top width increase.The seepage discharge for slanting core cases are more than vertical cases with similar area of core. Theresults obtained in this study are agreed with the results of the other investigators However, in slanting corecases the downstream part dry during steady state condition; this is helpful in improving downstreamstability.

Analysis of Slope Stability and Soil Liquefaction of Zoned Earth Dams Using Numerical Modeling

The design of dams requires comprehensive studies to ensure the safety and feasibility of these important engineering projects, as any possible failure case may lead to considerable losses in human life and properties. Specifically, analyses should be performed to evaluate seepage, slope stability, and soil liquefaction of large earth dams. In this study, numerical modeling, based on finite element methods, was used to analyze seepage, slope stability, and liquefaction of Makhoul Dam which is a large zoned dam, currently under construction on Tigris River in the north of Iraq. Earthquake shakings impose additional hysteric and short-term loads that may lead to dam failure due to high pore water pressure, piping, and soil liquefaction. Therefore, the dynamic stability of the dam and soil liquefaction were also evaluated, as a result of applying an earthquake shaking to the dam. For the static condition, the dam was safe against internal erosion and slope failure, as the calculated value of the safety factor was greater than the allowable value. However, the results obtained from the dynamic analysis indicated that a possible earthquake, with an acceleration of 0.38g and 10 seconds period, led to upstream slope failure, a relative displacement as high as 2 meters at the dam crest, and soil liquefaction at the upstream slope. As discussed herein, dam redesign or geotextile reinforcement may be considered to reduce the effects of earthquakes on the dam.

Comparison of Seepage Trough Zoned Earth dam Using Improved Light-Textured Soils

Seepage through earth dams is one of the most popular causes for earth dam collapse due to internal granule movement and seepage transfer. In earthen dams, the core plays a vital function in decreasing seepage through the dam body and lowering the phreatic line. In this research, an alternative soil to the clay soil used in the dam core has been proposed by conducting multiple experiments to test the permeability of silty and sandy soil with different additives materials. Then the selected sandy soil model was used to represent the dam experimentally, employing a permeability device to measure the amount of water that seeps through the dam's body and to represent the seepage line. A numerical model was adopted using Geo-Studio software in the branch (SEEP/W) to simulate the experimental model, examined soils with different percentages of additives, and compared the numerical and experimental results to predict the innovation model of soil. It was found that the sandy type (C) soil model has a permeability very close to that of clay soil when using 10% cement kiln dust (CKD) and 5% cement as additives. Furthermore, soil type (C) was calibrated with the core soil of HIMREEN Earth dam, which is clay soil, as well as with the core soil of HADITHA Earth dam, which is composed of dolomite. The comparison between the results of the hypothetical simulated cases and the real cases were revealed a high agreement between the two cases according to the resulted of identical phreatic (seepage) lines and the calculated amount of seepages water from these cases.

Experimental and theoretical investigations of seepage reduction through zoned earth dam material with special core

Seepage through earth dams is one of the main causes of failure of earth dams through the internal movement of granules and their transport by seepage. The core in earthen dams has an important role in reducing leakage through the dam body and lowering the phreatic line. In this research, an alternative to the clay soil used in the core of the dam was innovated by conducting multi experiments for testing the permeability of the light-textured, sandy soil which is more available, with additives and it proposed as a suitable alternative. Then the innovative soil model was then used to represent the dam experimentally by means of a permeability device to measure the amount of seepage through the dam body and represent the seepage line. A finite element numerical model using Geo-Studio SEEP/W software was adopted to simulate and investigate soil with different percentages of additives and comparing the numerical and experimental results to predict the innovation model of soil. It was found that the type C sandy soil model has permeability very close to the permeability of clay soils, by using 10% Cement kiln dust (CKD) and 5% cement as additives. Moreover, soil type C was hypothetically tested as a core soil for HIMREEN earthdam of clay core soil. The result of the comparison between seepage for the hypothesis case and the real case was acceptable and they were very close.

Numerical analysis of a zoned earth dam considering hydrodynamic force during the earthquake excitation

This paper presents finite element analysis of a zoned earth dam considering hydrodynamic force during the earthquake. Geostudio software using the sub-program SEEP/W and QUAKE/W was used. The earthquake that is used in this analysis are Iraqi earthquake that happened in Ali Al-Garbi within Missan governorate and El-Centro earthquake. Haditha dam section was used for the hypothetical dam. The maximum height of the dam is 57 m. The shell was constructed from the mix of sand-gravel with the average particles diameter range from (0.24 to 16.7 mm). Three different properties were used for core material, each one of these properties was analyzed under three different heads of water in the upstream side. The main parameters that have the influence on the analysis results are; water level in the upstream side of the dam, intensity of the earthquake, properties of the core material, and the value of hydrodynamic force. The hydraulic flux and peak displacement increase with increasing these parameters.

Finite element analysis of a zoned earth dam under earthquake excitation

This paper presents a finite element analysis of a zoned earth dam under the effects of earthquake conditions. GeoStudio software, and in particular the sub-programs SEEP/W and QUAKE/W were used, and the earthquake used in the analysis was an Iraqi earthquake that occurred in Ali Al-Garbi, within the Missan governorate. The Haditha dam section data was used for the hypothetical dam construction. The total length of length of this dam is 9,064 metres, which includes 8,875 metres of earth fill, and the maximum height of the dam is 57 m. The shell is constructed from a mix of sand and gravel, with an average particle diameter ranging from 0.24 to 16.7 mm. Three different properties were used to represent the core material, and each of these properties was analysed under three different heads of water on the upstream side. The results showed that high water levels at the upstream side of the dam heavily influenced the analysis results. The water flux, water conductivity, and peak displacement all increased with the increase in the water level upstream of the dam. For a water level equal to 152 m, the maximum values of water flux, water conductivity, and maximum displacement were 3.951 × 10-3 m2/sec, 6.654 × 10-3, and 2.03 m, respectively, while where the water level was 143 m, these values were equal to 2.023 × 10-3 m2/sec, 3.995 × 10-3, and 1.85 m, respectively. Further analysis showed that the water flux, water conductivity, and peak displacement increased with increases in the void ratio and degree of saturation of the clay core material, moving from 2.023 × 10-3 to 3.951 × 10-3 m2/sec for water flux, from 3.995 × 10-3 to 6.654 × 10-3 for water conductivity, and from 1.85 to 2.03 m for peak displacement.

Stability Assessment of Zoned Earth Dam under Water Particles Fluidity Effect: Hemren Dam as Case Study

Recently the numerical modeling using finite element method is take into account as a very effective tool to investigate the desired behavior of structures in geotechnical engineering. Earth dams are a water retention structures that are normally wide constructed around the world due to its significant features. These structures may be failed due to exposure to an earthquake and this will result in disaster. The main objective of this study is to assess the slope stability and the seismic response of an earthen dam. Since the matter of seismic response is still have a considerable lack of information for earth dams as a unique structure. Hemren zoned earth dam that is located in Diyala governorate, northeast of Iraq that considered as an active seismic zone has been considered as case study. Numerical modeling has been done in this study using Geo studio software. Factor of safety was calculated with different water levels in order to evaluate the dam safety with different operation water level. The excited earthquake is Elcentro while three values of peak ground acceleration were used which are 0.2, 0.25 and 0.3 g and the duration time is scaled to 10 seconds. In addition, three key points (at the core, the shell and the foundation) that represent the dam construction material are used to evaluate the dynamic response within the dam body. The results revealed that the factor of safety is increased when the water level is increase, but in the increasing in the magnitude of factor of safety with water depths of (10 and 15) m was more than the other depth. The zone of the dam core shows a negative pore water pressure value. That leads to an increasing in effective stress at the core of the dam.

Effect of vertical input motion and excess pore pressures on the seismic performance of a zoned dam

This paper investigates the combined effect of the vertical component of the input motion and of the weakening effect associated to pore-pressure build-up with reference to a zoned earth dam for which the most recent probabilistic seismic hazard analyses promoted the need of evaluating its seismic performance.The two effects were studied through advanced plane-strain non-linear dynamic analyses using a finite-difference numerical model calibrated on an accurate geotechnical characterisation. The occurrence of ultimate limit states in the dam embankment is checked using sets of horizontal and vertical input motions properly selected to account for possible frequency coupling with the dam.The analysis results are presented and discussed in the paper focusing on (i) the main features of the plastic mechanisms temporarily induced by the seismic actions, (ii) the amplification of the horizontal and vertical accelerations acting in the dam body, (iii) the role of the energy and frequency content of the input motion on the magnitude of earthquake-induced permanent displacements, (iv) the combined effect of frequency coupling and non-linear soil behaviour on the overall dam response.

Screening-level analyses for the evaluation of the seismic performance of a zoned earth dam

Many existing earth dams have been designed and built worldwide before the establishment of a seismic code, so that it is of relevant interest to evaluate their seismic performance and post-seismic operational conditions. This requires an accurate geotechnical characterisation of the dam and foundation soils, a proper definition of the seismic scenarios at the site of the dam, the use of simplified procedures for screening-level seismic analyses and advanced non-linear dynamic analyses to study the most critical seismic scenarios.This process has been used for the evaluation of the seismic performance of a zoned earth dam located in a high seismic hazard area of Southern Italy.In this paper the available data of historical seismicity at the site of the dam and the results of a probabilistic seismic hazard analysis are first discussed and input ground motions are selected using compatibility criteria with the energy and frequency content of the expected target motion in a range of vibration period relevant for the non-linear response of the dam. Seismic performance of the dam is then evaluated through procedures based on Newmark-type computations, in which permanent displacements are related to ground motion characteristics and to the seismic resistance of the dam, the latter evaluated detecting the earthquake-induced plastic mechanisms and the corresponding critical accelerations. Also, an original improvement of the well-known Makdisi & Seed procedure, was proposed to better capture the actual influence of non-linear soil behaviour in the evaluation of horizontal acceleration and permanent displacements of the crest of the dam. The analysis results pointed out the relevant role of the earthquake-induced shear strength reduction on the dam permanent displacements.

Numerical Analysis of Seepage in Earth-Fill Dams

In an earth-fill dam, the effect of seepage has been studied by applying a finite element method using the SEEP2D program. This is in order to determine the quantity of seepage through the dam. The total head measurements, core permeability, and anisotropy ratio (kx/ky) (Case study: Khassa Chai Dam, Iraq) are taken as the main parameters. The effect of the different water heads of the reservoir were tested on the seepage. The results showed that any increase in the water heads caused an increase in seepage quantity. Also, it was found that the seepage rate decreases by about 8.7%, 13.2%, and 15.3% at levels of water 454, 471, and 485 m.a.s.l, respectively by changing the core permeability from 10-6 m/s to 10-7 m/s. It has been concluded that the clay core plays a significant role in decreasing the seepage quantity and existing gradient. The results of testing the effect of anisotropy ratio on seepage showed that an increase in (kx/ky) ratio leads to an increase in seepage quantity. Output variables and input variables have been linked by the ANN model that governs seepage quantity through zoned earth dams and existed gradients. The results showed that both models present a good estimation for the determination of coefficient R2 (0.9003, 0.933).

Stabilization of sandy soil with high content of asphalt emulsion

Abstract The purpose of this article is to evaluate the shear strength parameters of mixtures of sandy soil with high asphalt emulsion contents for their use in geotechnical structures, such as zoned earth dams, embankments, etc. The methodology adopted consisted of: collecting and characterizing samples of sandy soil to be laboratory tested; compacting the mixtures between soils and asphalt emulsion with contents varying between 13% and 28% in weight by using different compaction methodologies; and performing direct shear tests to evaluate the parameters governing the shear strength behavior of the manufactured mixtures. Results showed that the use of a high asphalt emulsion content contributed to greater homogeneity of the mixtures. It was also found that the presence of residual asphalt gave a bilinear behavior to the sandy soil for the failure envelopes obtained from direct shear tests. At normal stresses usually less than 100 kPa, the mixtures present a cohesive intercept due the existing residual binder, while for normal stresses higher than 200 kPa, the mixtures presented a friction angle equal to the matrix of sandy soil used.

Assessment of a dam vulnerability to internal erosion due to climate change in Morocco

This research aims to investigate the susceptibility to internal erosion of Mazer earthen dam in Morocco under the drying effect causing desiccation due to the threats posed by the drought in North Africa. For this purpose, many erosion–filtration tests have been conducted on samples collected from core soil and downstream filter of the zoned earth dam. Materials have been analyzed with respect to the particle size distribution, plasticity index, permeability and their suitability for dam construction was assessed by using usual engineering guidelines. The investigation involved combined hole erosion and filtration experiments for testing internal erosion of the base soil and the downward granular filter efficiency. The results show a high resistance of the base soil against erosion and provide a method on quantitative measurement of the filtration efficiency and particle size selection. Erosion tests on a previously dried core soil reveal that the desiccation effect makes the soil more susceptible to erosion, indicating that a drought phase may threat strongly the core resistance against erosion in Mazer dam.

Rapid drawdown on earth dam stability after a strong earthquake

The paper focuses on the rapid drawdown of earth dams in the hypothesis that a prompt reservoir lowering is needed soon after a strong earthquake. The interest on such a topic comes from the fact that in Italy and worldwide there are many large dams placed very close to active faults. In this case, the dam may be asked to face the earthquake first and the rapid drawdown later to face an emergency state. The problem has been numerically investigated with reference to a zoned earth dam (Campolattaro Dam) placed in a highly seismic area of Southern Italy. To solve the overall boundary value problem, encompassing several stages of the dam lifetime, a 2D finite difference model has been solved through the FLAC2D code, implementing a coupled transient seepage formulation, which accounts for partial saturation of the soil during the drawdown stage. Unlike past literature studies, in which the drawdown stage was modelled without accounting for the past loading history of the dam, in the performed simulation the drawdown stage was placed at the end of a quite real sequence of events, encompassing the embankment construction, the reservoir impounding, and earthquake scenarios compatible with the dam site seismic hazard. The performed analyses pointed out that a seismic stage previously experienced by the dam could further contribute to decreasing dam stability during the drawdown especially during the first stages of reservoir lowering. In addition, the faster the drawdown, the smaller the dam safety factor against stability (FOS) with more prominent effects of the initial (pre-drawdown) soil conditions.

Failure of Zoned Earth Dam (An analysis of earth dam break)

One of the most common type of embankment dam failure is the dam-break due to overtopping. In this study, the finite elements method has been used to analyze seepage and limit equilibrium method to study stability of the body of an earthfill dam during the flood condition. For this purpose, the software Geostudio 2012 is used through its subprograms SEEP/W and SLOPE/W. Al-Adhaim dam in Iraq has been chosen to analysis the 5 days of flood. It was found that the water flux of seepage during the flood reaches about 8.772*10-5. m3/sec when the water level 146.5 m at 2nd day. Seepage through the embankment at maximum water level increased by 55.1 % from maximum water level. It was concluded that the factor of safety against sliding in downstream side decrease with increasing water level and vice versa. It was also concluded that the deposits are getting more critical stability during the conditions of flood when the factor of safety value reaches 1.219 at 2nd day.