Earthfill Dam Research Articles

Risk evaluation for earth-fill dams due to heavy rains by response surface method

ABSTRACT This paper discusses a risk evaluation for earth-fill dams due to heavy rains. The detailed method employs a flood analysis and land use data to calculate the costs of the inundation damage in the downstream areas of earth-fill dams. The procedure to calculate the damage costs requires a lot of labour. Since a huge number of earth-fill dams exist in Japan, a straightforward method is needed. The response surface method, one of the surrogate models, is proposed in this study to reduce the calculation effort. The optimum response surface is firstly evaluated by cross validation, and then the accuracy is verified by comparing the damage costs obtained by the response surface method with those obtained by the detailed method for the earth-fill dam sites. To calculate the risks, it is necessary to determine the probability of overflow failure due to heavy rains. The risk of breaching is calculated from the product of the probability of overflow failure and the estimated damage costs. The accuracy of the response surface method is assessed by comparing the risk rankings of the dams, which is the priority in dam renovations, between the detailed and the response surface methods.

Establishment of Readily Mathematical Formulation for the Evaluation of Slope Stability in Earth-Fill Dams

Establishment of Readily Mathematical Formulation for the Evaluation of Slope Stability in Earth-Fill Dams

Результаты натурных исследований осадок в теле земляной плотины

The purpose: to conduct field studies to determine the vertical settlement in the body and assess the safety of the earthfill dam of the Lyangar reservoir. One of the ways to ensure the safe condition of earthfill dams during operation is to conduct field studies in the facility. One of the factors leading to the overflow over the structure crest is the settlement of the earthfill dam body. Excessive settlement of the earthfill dams of reservoirs are assessed on the basis of observational data and design documentation. In practice, the settlement of earthfill dams during the operational period should not exceed the values specified in the project. The quantitative determination of the settlement of the earthfill dam body was carried out on the basis of the requirements specified in the regulatory documents. Materials and methods. In the process of research, theoretical and generally accepted detection methods of vertical deformations on the crest of an earthfill dam using geometric leveling were used. The research and verification of tools was carried out in accordance with regulatory documents before carrying out the work. Results. Geodetic measurements were carried out on the example of the earthfill dam of the Lyangar reservoir. Repeated geodetic measurements (the second cycle) for determining the settlement of the earth dam crest were carried out. The longitudinal profile of the crest of the object under consideration was constructed on the results of geodetic measurements. During the observation period, the settlement of the earthfill dam crest was 15 mm in the first cycle and 18 mm in the second cycle. Conclusions. The indicators obtained as a result of geodetic measurements, when compared with the indicators given in the regulatory documents, testify that the safe state of the structure is ensured, which does not lead to water overflowing over the earthfill dam crest.

Design of unsteady filtration in the upper water-resistant prism of earthfill dams given horizontal drainage layers in the base

The article presents the results of the study of unsteady filtration in the upper water-resistant prism of dams given horizontal drainage layers in the base. Design methods have been developed for unsteady filtration in the upper water-resistant prism of dams, given horizontal drainage layers in the base. Research main results have been presented for the number of schemes of drainage in the upper waterresistant prism of dams. Experimental research has been carried out to check the validity of accepted assumptions when deriving relationships for the filtration design of earthfill dams with horizontal drainage layers and assess the accuracy of the solutions obtained. Experimental research on processes under consideration for physical models has shown a good resemblance with the results obtained from numerical calculations. This makes it possible to confirm the validity of chosen design schemes and accepted initial assumptions in numerical studies.

The Impact of Dam Reservoir on Flood Reduction (Case Study Logung Reservoir, Kudus, Central Java)

The Indonesian government targeted building 65 reservoirs and dams in 2015-2022. The purpose is to maintain food security facing the long-term climate crisis, besides reducing the impact of a flood. Logung Reservoir is located on the Logung River, Kudus, Central Java. This earth-fill dam was built to solve the flood and drought problems in Kudus. However, the existence of the Logung Reservoir gives a risk to the downsteam area. The purpose of this research is to study flood reduction and the risk of overtopping, which can cause a dam break, and to calculate the Logung Reservoir spillway's performance in handling floods. This study is based on four main steps: the rainfal-runoff modelling, the extreme rainfall estimation, the hydrograph inflow of the dam estimation, and the evaluation of food reduction. The results of the 1000-year rainfall analysis and PMP for the Logung dam basin were 409 mm and 704 mm, respectively. Rainfall distribution is made using ABM, and effective rainfall is calculated by the SCS method. Land use analysis in the Logung dam watershed obtained a CN-II of 71.4 and a CN-III of 85.2. The rainfall-runoff transformation method used a unit hydrograph. The Nakayasu and Gama-I unit hydrographs show significant differences from the peak discharge, although not for the time base. The flood hydrograph design affects the reservoir performance. The reservoir flood routing results a dumping efficiency of 35% for the 1000-year and 21% for PMF. The 1000-year flood routing shows that there was no risk of overtopping. The highest water level on the PMF flood routing at +94.1. Several solutions can prevent overtopping by reducing inflow discharge through small dams upstream, increasing the green area, or modifying spillway structure.

The earth-fill dam state express investigation using mechanical vibrations produced by HPP

The usage of mechanical vibrations produced by the hydropower plant (HPP) turbine may be used for seismic sounding of large-scale constructions as the earth-fill dam and its abutment contacts. Such vibrations are monochromatic oscillations on main frequencies and their harmonics produced by turbine. Seismic sensors installed on the dam's crest and inside it, if it possible, and in the area of abutment contacts register microseisms include HPP turbine operation vibrations which may be extracted by seismic data processing, i.e., filtering. We discuss two data processing possibilities: symphonious filter as the hardware one and power spectrum calculation as digital one. We consider the two case of earth-fill dams state investigations. There are the Chiryurt HPP dam (Republic of Dagestan, Russia, 9.5 m high) and the Nurek HPP dam (Tajikistan, 300 m high). We show the possibilities of seismic express investigations using signals of main frequencies produced by HPP turbine for dam sounding. For Chiryurt dam the extra fluid filtering in the central part of the dam was revealed. Nurek dam abutment contact monitoring showed the temporal variation of its stress-strain state associated with deformation variation 10-5-10-6 presumably due to regional seismicity.

Spatially varying earthquake ground motion: artificial generation and effects on earth-fill dam behavior

ABSTRACT The observed amplitude and phase differences of seismic ground motions recorded at different locations over extended areas are termed as spatially varying earthquake ground motion (SVEGM). Earthquake-resistant design and seismic risk assessment of extended structures require three-dimensional dynamic analyses for which the excitation is needed in the form of three-directional SVEGM components, where each component needs to be consistent with the coherency model. In this paper, the principal features of the performed analyses are as follows: (1) discretisation of the spatial domain at the foundation base, (2) the selection of coherency model and (3) propagation angle of the seismic waves. In the first part of the paper, three cases for the generation of three-directional SVEGM are presented. First, the two-dimensional spatial domain, representing the foundation base of the extended structure, is discretised. Second, for case 1, the three-directional SVEGM is generated using the Liu and Hong coherency model at the cells of the grid. In this case, the loss of coherency is considered independent of the direction of the wave propagation (case general). Then, for the case 2, the two different propagation angles of 30 and 60 degrees of seismic waves and the Liu and Hong coherency model are considered. Finally, using the anisotropic coherency model of Hao et al. and the propagation angle 45 degree, the three-directional SVEGM is generated, in case 3. Results show that each component of the generated SVEGM records is affected by propagation angle and directional dependency of the coherency model. The second part of the paper is devoted to two-dimensional analyses of Marun earthfill dam and three-dimensional analyses of earthfill dams with different length-to-height ratios subjected to uniform input motion and artificially generated SVEGM.

Experimental investigation of sediment movement as a result of homogeneous earth-fill dam overtopping break over a simplified urban area

When an earth-fill dam breaks, dam body sediment and water flow simultaneously move to downstream area causing devastation. Dam break studies in the literature have concentrated mostly on the water flow part while ignoring the sediment movement by designing the dam body as a movable metal gate. This study, however, is the first one experimentally investigating flow and sediment transport due to an earth-fill dam break by constructing the dam body from sediment. Sediment propagation as a result of homogenous earth-fill dam overtopping break was experimentally studied in a laboratory flume of 18.4 m long and 2.0 m wide, and 0.88 m in height in the Hydraulics Laboratory of Izmir Katip Celebi University, Izmir, Turkey. Downstream section right after the dam body was designed as a smooth bed and rough bed. The rough bed, resembling a simplified urban area, was created by using thirteen 10 × 10 × 10 cm sized concrete blocks. The dam body was constructed as homogenous with uniform material having D50 = 0.441 mm. The earth-fill dam body was built using the standard compression methods; each layer of sediment with a thickness of 10 cm was laid in layers, and the body was prepared with a crest width of 10 cm, a transverse base width of 200 cm, a longitudinal base width of 202 cm and height of 60 cm with upstream and downstream slopes of 1:1.6. The water level behind the dam was gradually raised until it overtopped the crest level. A pre-breach was formed at the top of the dam to trigger the break. During each dam break event, water depths were measured by three ULS-40D level meter sensors at different locations, and the final sediment bathymetry map was generated using the ULS-40D Probes at 10 × 10 cm grids. The results showed that, in both smooth and rough downstream bed cases, the dam body eventually collapsed while a great portion of it was carried away by the flood flow. The sediment spreading occurred all over the downstream area, showing significant non-uniform variation in thickness both longitudinally and transversely, especially in the simulated urban area. All the residential areas, while breaking in motion, were submerged under the muddy flow. Some blocks were almost submerged while sediment heights reached half level of some blocks at the end of the experiment. Sediment heights were higher in the urban area.

Prediction of the Amount of Sediment Deposition in Tarbela Reservoir Using Machine Learning Approaches

Tarbela is the largest earth-filled dam in Pakistan, used for both irrigation and power production. Tarbela has already lost around 41.2% of its water storage capacity through 2019, and WAPDA predicts that it will continue to lose storage capacity. If this issue is ignored for an extended period of time, which is not far away, a huge disaster will occur. Sedimentation is one of the significant elements that impact the Tarbela reservoir’s storage capacity. Therefore, it is crucial to accurately predict the sedimentation inside the Tarbela reservoir. In this paper, an Artificial Neural Network (ANN) architecture and multivariate regression technique are proposed to validate and predict the amount of sediment deposition inside the Tarbela reservoir. Four input parameters on yearly basis including rainfall (Ra), water inflow (Iw), minimum water reservoir level (Lr), and storage capacity of the reservoir (Cr) are used to evaluate the proposed machine learning models. Multivariate regression analysis is performed to undertake a parametric study for various combinations of influencing parameters. It was concluded that the proposed neural network model estimated the amount of sediment deposited inside the Tarbela reservoir more accurately as compared to the multivariate regression model because the maximum error in the case of the proposed neural network model was observed to be 4.01% whereas in the case of the multivariate regression model was observed to be 60.7%. Then, the validated neural network model was used for the prediction of the amount of sediment deposition inside the Tarbela reservoir for the next 20 years based on the time series univariate forecasting model ETS forecasted values of Ra, Iw, Lr, and Cr. It was also observed that the storage capacity of the Tarbela reservoir is the most influencing parameter in predicting the amount of sediment.

Behaviour of Earth Fill Dam under Earthquake Load Using Finite Element Method: A Case Study of Semenyih Dam

In this project, an earth-fill dam in Selangor which is Semenyih Dam, a major dam in the Klang Valley with a capacity of 60.6 million cubic metres, a height of 49 metres, and a crest length of reservoir embankment of 830 metres, is being used as a study subject. The Finite Element Method was used in this work to assess the stress and deformation of Semenyih Dam, an earth dam in Selangor that was resting under hydrostatic pressure. The second objective is to study the Semenyih dam’s seismic response due to the Ranau Earthquake loading. The analysis of the Semenyih Dam’s structural performance under historical seismic loading from the Ranau Earthquake with a peak ground acceleration of 0.013g was done using the LUSAS Modeller 14.3 software. As a result, it was discovered that the dam’s deformation and displacement caused by the Ranau earthquake with hydrostatic pressure was larger, at 5.33 mm, as opposed to 1.822 mm when there was no hydrostatic pressure. The dam’s deformation is different in the two scenarios. When the Ranau earthquake combined with hydrostatic pressure, the dam deformed significantly. From the bottom of the dam to the top, there was an increase in stress distribution. Both hydrostatic pressure and an earthquake would put further strain on the dam. Semenyih Dam’s maximum stress is 189.152 N/m2 (with hydrostatic pressure), 27.4948 N/m2 (without hydrostatic pressure), which are less than the silty clay’s 290 kN/m2 allowable stress capacity. According to the investigation, when a dam is subjected to a variety of loads and forces, the stress distribution within it increases.

Evaluation of Seepage on the Right Side of Haditha Dam, West of Iraq

The study aims to assess the water seepage through the right side of Haditha dam structures in western Iraq, using the finite elements method by an advanced computer software (SEEP/ W, 2012), the earth fill dam is 9 km long on the Euphrates River. Many attempts were done to ascertain the results of the program on a supposed earth dam and compare the results with the other analytical methods. The comparison reveal to very close results, and this indicate the suitability of the software for Haditha dam structures seepage analysis. After the verification of the results, then the real design information of the dam was input to analyse the dam, the input data are the height of the dam, width, slope of upstream and downstream, dimensions of the core, hydraulic conductivity of the different materials of the dam and the foundations. The results obtained from the SEEP/W2012 software were compared with the actual field data of the seepage amount for years (1989 - 2017) and with the water level in the dam reservoir for different periods. The result of comparison gave an idea to the efficiency of the dam protection against the seepage.Through the SEEP/ W data, which simulates the dam sections, levels and discharges that calculated by the software, which is compatible with the field monitoring data, it can be said that the software was able to simulate the actual conditions of the dam and identify the weakness zones. Where the results displayed that the asphaltic diaphragm in good condition and efficient on the right side of the dam. The grouting curtain in the right side is efficient, except for the area between the two stations 15 and 25, the zone between two stations need a continuous monitoring. The results also reflect that earth fill materials and the central core of the dam are efficient, and seepage within permissible design values.

Delayed instabilities of water-retaining earth structures

Aging earth fill dams that were constructed in the mid-1950’s are beginning to show signs of instability associated with time-dependent degradation of shear strength. The strength degradation can be attributed to fissures, leaching of cementation, and creep in highly plastic clays, among other issues. The time-dependent processes are being examined in an earth fill dam that experienced slope instability but did not result in a loss of water. This paper discusses research findings on the mechanisms of delayed slope instability of an earth fill dam. Identifying the operating mechanisms of instability is useful in developing sound and practical remedial measures. It is also a useful way of being more proactive on the part of engineers in assessing the stability of dams at other generating stations that may not satisfy modern dam safety standards.

Understanding the Effect of Hydro-Climatological Parameters on Dam Seepage Using Shapley Additive Explanation (SHAP): A Case Study of Earth-Fill Tarbela Dam, Pakistan

For better stability, safety and water resource management in a dam, it is important to evaluate the amount of seepage from the dam body. This research is focused on machine learning approach to predict the amount of seepage from Pakistan’s Earth and rock fill Tarbela Dam during 2003 to 2015. The data of temperature, rainfall, water inflow, sediment inflow, reservoir level collected during 2003 to 2015 served as input while the seepage from dam during this period was the output. Artificial Neural Network (ANN), Random Forest (RF), Support Vector Machine (SVM), and CatBoost (CB), have been used to model the input-output relationship. The algorithms used to predict the dam seepage reported a high R2 scores between actual and predicted values of average seepage, suggesting their reliability in predicting the seepage in the Tarbela Dam. Moreover, the CatBoost algorithm outperformed, by achieving an R2 score of 0.978 in training, 0.805 in validation, and 0.773 in testing phase. Similarly, RMSE was 0.025 in training, 0.076 in validation, and 0.111 in testing phase. Furthermore, to understand the sensitivity of each parameter on the output (average seepage), Shapley Additive Explanations (SHAP), a model explanation algorithm, was used to understand the affect of each parameter on the output. A comparison of SHAP used for all the machine learning models is also presented. According to SHAP summary plots, reservoir level was reported as the most significant parameter, affecting the average seepage in Tarbela Dam. Moreover, a direct relationship was observed between reservoir level and average seepage. It was concluded that the machine learning models are reliable in predicting and understanding the dam seepage in the Tarbela Dam. These Machine Learning models address the limitations of humans in data collecting and analysis which is highly prone to errors, hence arriving at misleading information that can lead to dam failure.

Saturated and unsaturated seepage analysis of earth-fill dams using fractal hydraulic conductivity function and its verification

One of the most important factors concerning the design of earth-fill dams is the accurate seepage estimation, which is highly correlated to the permeability and hydraulic conductivity of the core material. With the geographic coordinates of 37°31′35.9,“ North and 46°07′55.6″ East, Gale chay dam is located in the northwest of Iran in East Azerbaijan province. The dam is highly important regarding the provided economic benefits for the region. In this research, the steady-state seepage analysis of the Gale Chay dam was conducted via the finite element model (FEM) using a novel saturated fractal hydraulic conductivity model, and the results were compared with those obtained from the conventional and fractal models in the unsaturated condition. For estimating the saturated hydraulic conductivity of the core material, the fractal theory was employed using the image processing technique, the Scanning Electron Microscope (SEM) images, and a new fractal permeability model. The estimated saturated hydraulic conductivities were in good accordance with the measured values. Furthermore, since the fractal theory considers the distribution of the pores, the estimated upper and lower bounds of the saturated hydraulic conductivity resulted in better seepage estimations. Using the estimated maximum, minimum, and average fractal hydraulic conductivities, the results of the saturated seepage analysis indicated relative errors of 15.6%, 8%, and 10.8% compared to the observed seepage. The results were acceptable in terms of safety and economic aspects. Conducting the unsaturated seepage analysis, it was observed that the estimated seepage was highly influenced by the saturated hydraulic conductivity value. Hence, the estimated average fractal hydraulic conductivity by the image processing technique affected the unsaturated fractal and conventional models in a way that the unsaturated seepage analysis was improved by an average of 80%. Moreover, the unsaturated fractal model revealed reliable estimations compared to the conventional models and was considered a feasible alternative for estimating the unsaturated hydraulic conductivity.

Seepage detection in earth-filled dam from self-potential and electrical resistivity tomography

Earth-filled dams are prone to serious erosion and seepage by water flow. Anomalous seepage is a threat to the stability of dam structures and is a common hydrogeological hazard in engineering. It is of great significance to clarify seepage paths for targeted remediation. In this paper, we present the joint use of self-potential (SP) and electrical resistivity tomography (ERT) methods to characterize the seepage paths in an earth-filled dam, where there is already evidence of abnormal seepage. The ERT provides effective information on the resistivity structure of the dam. The SP data aims to invert electrokinetic current sources generated by the seepage. The results reveal that the seepage of the dam generates streaming potentials, which result in a negative SP anomaly with an amplitude of 50–80 mV at the surface. Based on electrokinetic current sources from SP data and resistivity structures, we reconstruct three seepage paths, which coincide well with field borehole information. This case demonstrates the effectiveness of combining SP and ERT for characterizing the seepage path of dams.

Precursory motion and deformation mechanism of the 2018 Xe Pian-Xe Namnoy dam Collapse, Laos: Insights from satellite radar interferometry

The sudden failure of hydraulic dams poses catastrophic hydrological risks to local communities and environments. The 2018 Xe Pian-Xe Namnoy Dam collapse in Southern Laos unleashed a flood wall that resulted in more than 70 deaths and left thousands homeless. While the causes of this event were clearly known as geological and engineering issues, the detailed process of dam degradation and potential hazards of other dams in the area remain unclear. In this study, we use radar satellites to investigate the precursory deformation of major dams in the Xe Pian-Xe Namnoy hydropower project. By combining independent component analysis and an Earth loading model to decompose the observed deformation into various time-dependent components, we study the possible deformation mechanism. We identify a precursory vertical deformation acceleration on the collapsed Saddle Dam D reaching up to 13 cm/yr two months before the failure. Two earth-fill saddle dams (E and F) also experienced accelerating subsidence of ∼ 9 cm/yr two months before the dam failure. The deformation pattern of these saddle dams resembles that of the collapsed Saddle Dam D, indicating a critical need for reinforcement interventions before being returned to service. In comparison, the rock-fill Xe Pian and Xe Namnoy Dams were relatively stable before the 2018 failure event. We show that water pressure, consolidation, thermal expansion, and precursory acceleration are the major mechanisms controlling dam deformation. Our results provide additional details for understanding the cause of the dam-break, and also to warn that other saddle dams associated with the project may also break if no further treatment is done. In addition, this study demonstrates the importance of space-borne radar interferometry and hybrid data analysis for early warning and hydrological safety management of small-to-medium-size dams, where in situ monitoring systems are often unavailable.

Coupled Numerical and Analytical Stability Analysis Charts for an Earth-Fill Dam under Rapid Drawdown Conditions

The presented article provides a comprehensive study on the stability analysis of earth-fill dams under rapid drawdown and transient flow conditions used to prepare stability analysis charts by conducting coupled finite-element numerical and analytical limit equilibrium procedures. In this regard, the impacts of different rapid drawdown conditions on the safety factor of the Alavian earth-fill dam are determined. The slope stability charts present for both shallow and deep slip surfaces with various permeabilities are verified by ground information obtained with extensive instrumentation on the dam’s site. The results showed that by decreasing the permeability of the core’s material, despite preventing seepage, the instability risk of the upstream slope as a result of rapid drawdown intensifies. Also, as stability charts can be stated, with increasing the slip surface’s depth and decreasing the hydraulic hydration, the reliability decreases, and the sliding surfaces’ sensitivity increases based on the drawdown rates, which have been revealed to be from 0.2 to 0.6, the most critical state for safety factors, showing significant declines.

The Effect of Horizontal Drainage Lengths on the Stability of a Homogeneous Earth-Fill Dam Under Seepage Conditions

Failures can occur from seepage failure in the downstream slope of an earth-fill dam. The excessive pore pressures and seepages must be controlled to achieve the desired safety level in such dams. This safety can be provided with a horizontal drainage cover design. The essential goal of drainage system design is to increase system efficiency in reducing pore water pressures and seepage. Several calculations were made with a downstream slope cover design and downstream horizontal drainage length for homogeneous earth-fill dams. The minimum and maximum effective length of the filtered drainage system was obtained after the analyses. Moreover, the factor of safety regarding the downstream slope was calculated for the drainage system with different geometries. The results showed that the horizontal drainage length affects system performance and the seepage behavior of the dam.

Determination of 3D near fault seismic behaviour of Oroville earth fill dam using burger material model and free field-quiet boundary conditions

ABSTRACT In this study, the three-dimensional (3D) near-fault earthquake performance of the Oroville dam is examined considering a special material model and various seismic boundary conditions. The 3D finite-difference model of the Oroville EF dam is modeled using the finite difference method. Burger Creep (BC) material model is utilized for the foundation and dam body materials. Special interface elements are taken into account between the dam body and foundation. Fix, free field, and quiet seismic boundary conditions are considered for 3D nonlinear earthquake analyses. Total six various strong near-fault earthquakes are used in the 3D analyses. According to the non-linear earthquake analyses, principal stresses, horizontal and vertical displacements for three nodal points are assessed in detail and numerical results are compared for reflecting and non-reflecting seismic boundary conditions. It is clearly understood that seismic boundary conditions should not be utilized randomly for 3D modeling and analysis of EF dams.

Understanding the Seepage Behavior of Nai Gaj Dam through Numerical Analysis

This study presents the seepage patterns of earth-fill dams, using critical situations by employing the finite element approach. The Nai Gaj dam is 65km northwest of Dadu city in Sindh Province, Pakistan. In this study, the seepage through the main dam body and foundation is computed and simulated for different scenarios, i.e. maximum, normal, and minimum reservoir level. Seepage analysis was conducted by using the SEEP/W sub-program of GEO-SLOPE software. Dam design parameters and dam geometry data were used as input data to compute the unknown seepage. The seepage behavior of the Nai Gaj dam is shown in terms of net flow which consists of equipotential lines, streamlines, velocity vectors, and phreatic lines. The results show the seepage flux, maximum seepage, and exit gradient at different reservoir levels. The results show that the average flow rate at normal, maximum, and minimum reservoir levels are 1.49×10-7cumec/m, 3.38×10-7cumec/m, and 2.108×10-8cumec/m respectively. In addition, the overall stability of the side slope of the dam is discussed.