Earth-rock Dam Research Articles

Laboratory testing and numerical modeling of geomembrane electrical leak detection surveys

Laboratory tests were conducted to evaluate the influence of the positions of positive and negative electrodes on the electrical response of a leak in the geomembrane. A numerical evaluation was performed to model the laboratory conditions and to investigate the effect of dipole spacing, excitation voltage, and impoundment resistivity on the leak detection sensitivity. The results of laboratory tests show that leaks cannot be identified when the positive electrode is very close to the leak and the electrical response of a leak in the geomembrane is independent of the position of the negative electrode. The results from the 3D finite element model indicate that leak detection sensitivity improves nonlinearly as the dipole spacing increases, and it tends to be stable after the dipole spacing exceeds 5% of the length of the survey line. The results also indicate that there is an almost linear increase in the leak detection sensitivity with increasing excitation voltage. Substantial improvement was obtained in the leak detection sensitivity for a greater impoundment resistivity. The numerical results indicate that 90% of leaks in a geomembrane liner can be effectively detected and accurately located for the 3D finite element model of a geomembrane lined earth-rock dam.

Study on the Long-Term Reliability of the Tangshuiya Reservoir Dam

Du, P. and Wang, Y.Y., 2020. Study on the long-term reliability of the tangshuiya reservoir dam. In: Bai, X. and Zhou, H. (eds.), Advances in Water Resources, Environmental Protection, and Sustainable Development. Journal of Coastal Research, Special Issue No. 115, pp. 556-560. Coconut Creek (Florida), ISSN 0749-0208.Weifang section of the Yellow River Diversion Project is a comprehensive large-scale water conservancy project, which mainly solves the water supply of Weifang, and also uses farmland irrigation, flood control and hydropower generation. The tangshuiya reservoir dam is a gravity earth rock dam. The research on the rheological properties of rock mass in the project area is the basis of analyzing the long-term stability of slope and cavern. The creep pattern under different levels of tri-axial stress has been experimentally studied. A creep damage model is established. By comparing the fitting result with the experimental data, the model can accurately predict the creep characteristics of shale at different stress levels. Based on the research results of this paper, it can provide guidance for flood control and disaster reduction, improve the creep resistance performance of the reservoir dam and river embankment, and avoid major disasters due to creep.

Analysis of Social and Environmental Impact of Earth-Rock Dam Breaks Based on a Fuzzy Comprehensive Evaluation Method

A large proportion of the dams in China are earth-rock dams. Regarding the well-studied loss of life and economic consequences due to dam breaks, this paper introduces the causes and modes of earth-rock dam breaks and the corresponding dam-break losses in terms of the social and environmental aspects. This study formulates the evaluation index system and criteria of earth-rock dam breaks’ impact on society and the environment based on a fuzzy comprehensive evaluation method. The results show that the evaluation grade of the social and environmental impact of the dam break of the Liujiatai Reservoir was “serious”. Therefore, similar dams in China should take corresponding measures in advance to reduce the social and environmental impact of earth-rock dam breaks.

Grouting experiment in a completely weathered granite dam abutment: case study on grouting technique and test analysis

Anti-seepage grouting of earth-rock dams is an important aspect of dam construction projects. Completely weathered granite is a typical porous granular soil. Traditional grouting techniques cannot meet the requirements of completely weathered granite grouting. Therefore, pulsating grouting, which combines drilling and grouting, is proposed, and grouting experiments were performed on a completely weathered granite reservoir abutment in combination with traditional clay–cement slurry materials. The results show that single row, 1 m hole spacing of the permeability after grouting was less than 10 Lu. The acoustic wave velocity increased by 17.3–52.5%. Moreover, the core sample was relatively complete, and the compressive strength of the core reached 7.3 MPa on average. The proposed technique significantly reduces the unit cost is applicable to completely and strongly weathered granite and similar formations. Thus, this work provides an engineering reference for these formations.

Back analysis of permeability coefficient of earth-rock dam based on EMD-RVM

Since contemporary information-retrieval systems rely heavily on the content of titles and abstracts to identify relevant articles in literature searches, great care should be taken in constructing both. Since the permeability coefficient of the dam material of the earth-rock dam directly affects the seepage flow of the dam, in order to improve the accuracy of retrieving the permeability coefficient from the measured value of the seepage flow, the empirical mode decomposition method (EMD) is used to monitor the actual seepage flow of the weir. After decomposition, multiple sets of intrinsic modal functions (IMF) were generated to fit the relationship between water level and seepage flow; then the finite element software was used to calculate the seepage flow corresponding to the randomly distributed infiltration parameters at different water levels in order to the RVM model performs inverse analysis on the permeability coefficient. The training sample group is constructed by finite element calculation, the calculated seepage volume of the sample group is used as the input value, and the corresponding permeability coefficient is used as the output value. Based on EMD-RVM, a nonlinear mapping relationship between the permeability coefficient and seepage volume of each section of the face rockfill dam is established. Using the model inversion, the results show that the EMD-RVM model has high inversion accuracy and is significantly higher than the conventional RVM model and GA-BP model. The infiltration pressure of the face rockfill dam can be calculated from the inversion result of the permeability coefficient, and the error with the measured value is small, which verifies the feasibility of the model.

Infrared image-based identification method for the gradation of rock grains using heating characteristics

In earth-rock dam engineering, the gradation characteristics of filling materials have an important influence on the compactability, impermeability, and stress–strain characteristics of dams. A sound gradation is the key to guaranteeing dam safety and stability. Based on the principles of the heat conduction and heating characteristic tests on rocks, the power function equation between volume and temperature increase for pebble and gravel grains in a heating environment is established with correlation coefficients of 0.98. Aiming at the low span of gray-scale change of digital infrared images, the linear gray-scale transformation method with a Gamma factor of 1 to enhancing the digital infrared images, and the maximum between-cluster variance method (OSTU method) is adopted to perform binary grain target-context segmentation on enhanced images. With regard to the phenomenon of grain adhesion, it subjects flattened images after binary segmentation to peak processing using Dis operation, and introduces an improved watershed algorithm (i.e., local minimum with threshold) for image reconstruction, effectively segmenting adhesive grains while avoiding over-segmentation. According to maximum stability theory, the shortest side of the minimum enclosing rectangle (MER) of the grains in images is proposed as the judgment index for grain sieving. Five gradation detections were carried out on pebbles and gravels, respectively. For grain mass fraction identification results for various grain size intervals, the maximum absolute errors for pebbles and gravels do not exceed 6% and 7%, and the average absolute errors do not exceed 4% and 5%, respectively. Thus, the identified gradation curve fits well with the mechanical sieving gradation curve, and can meet engineering application requirements. This new method overcomes several deficiencies of traditional methods for gradation image detection, such as the susceptibility of image sampling to various interfering factors and difficulties in controlling errors in calculating grain mass, and therefore, provides a novel conceptual technology for particle grading image recognition.

Discussion on deformation monitoring method of asphalt concrete core wall of high earth-rock dam

The deformation of asphalt concrete core wall of earth rock dam is an important monitoring item of safety management in the construction and operation period of the project. This paper summarizes the conventional monitoring methods and principles of the deformation of asphalt concrete core wall, analyzes the application scope and existing problems of the conventional monitoring methods, and introduces a new method and principle of the deformation monitoring of asphalt concrete core wall of high earth rock dam, which effectively solves the problems The problems of conventional monitoring methods are solved, and the three-dimensional deformation monitoring of asphalt concrete core wall is realized.

Intelligent rolling compaction system for earth-rock dams

The compaction quality of earth-rock dams primarily depends on manual control of the compaction parameters during construction and random spot tests after construction. However, manual control of the compaction parameters can result in more control errors and quality defects and cannot satisfy the requirements of construction operations under all weather and extreme conditions. Additionally, spot tests with characteristics such as random and destructive detection, low efficiency, and high costs cannot adequately reflect the compaction status of an entire area or satisfy the requirements of rapid mechanised construction. This paper presents an intelligent rolling compaction method based on a new framework of material-machine-information-machine intelligent decision-making for earth-rock dams. Using the proposed system integration method based on three-layer structure, IRC system can be obtained by integrating the continuous compaction control acoustic wave detection (CAWD) system combined with real-time kinematic global positioning system (RTK-GPS), intelligent decision-making (IDM) system based on the global compaction process-dynamic optimisation method (GCPDOM), unmanned rolling compaction (URC) system based on automatic driving technology, and real-time remote monitoring centre based on the triangle architecture. The implementation of the proposed system in the Qianping Reservoir construction site has shown that its operation is stable and reliable, and it can effectively eliminate the impact of human factors on compaction quality control, thereby significantly improving the compaction quality and construction efficiency of earth-rock dams.

Seismic dynamic responses of earth-rock dam considering wave and seepage

Earth-rock dam plays an important role in water conservancy project, but there were many damage cases caused by earthquakes, so it is necessary to investigate dynamic responses of earth-rock dams under combined action of earthquake and wave. Considering material nonlinearity, seepage, wave action, fluid-solid interaction, liquid sloshing, a numerical calculation model is established, and Arbitrary Lagrange Eulerian method is used to solve the nonlinear dynamic coupling problem. Dynamic responses under wave, earthquake and wave+earthquake are studied comparatively, and influences of near and far field earthquakes and PGA on dynamic responses are investigated. Results show that values and distributions of dynamic responses under wave and earthquake are quite different, and dynamic responses were further increased considering combination of earthquake and wave. Dynamic responses under far field long period earthquake is significantly larger than that under near field earthquake. With the increase of PGA, increase trends of horizontal displacement, vertical displacement and plastic strain are increased, while increase trend of maximum shear stress is slowed down. It can be obtained that when earthquake intensity is large, earth-rock dam will be easily damaged due to excessive deformation.

Cellular automata‐based analysis for seepage failure process of earth‐rock dam

Research on the process and its mechanism of dam failure is a long-term focus in dam engineering field. The reasonable analysis and prediction of dam failure are of great significance to improve the level of dam emergency management and reduce the risk of dam break. A cellular automata (CA)-based approach is introduced to implement the simulation analysis for the process of piping failure and its induced break in earth-rock dam. According to the energy conversation mechanism during the dam body failure, the local effect rule of earth-rock dam failure is presented. Based on the physical and mechanical properties of earth-rock dam, a CA model of earth-rock dam break is built. Some key implementation technologies, which are used to simulate the break process of earth-rock dam, are developed by analyzing the relationship between the generalized energy and the deformation of soil particles. The method simulating the seepage channel formation by the CA model is proposed, and the mechanical criterion on the seepage channel development is given. Lastly, the piping breach of one actual earth-rock dam is taken as an example. Its CA model simulating the process of piping failure is built. The development of breach width, which is induced by the piping failure, is analyzed. The influence of the height of initial seepage channel on the breach width development is estimated.

Calculation and Analysis of Earth-rock Dam Seepage Flow Based on FEM

Earth-rock dam is the oldest dam type and is the most widely used type of dam in the world. Because earth-rock dams have the superiority that other dam types do not have, earth-rock dams have a large proportion in China. After the earth-rock dam is built to retain water, it sees a seepage in the dam body. The earth and rock material in the saturated zone is subjected to buoyancy, which reduces the effective weight against sliding. After the dam is immersed in water, the shear strength index of the earth and stone will be reduced, and the seepage force may have an adverse effect on the dam slope. When the seepage flows out of the dam slope, dam foundation or river bank, the dam body may cause piping, fluid and other seepage damage. Therefore, we must carry out the seepage analysis of the dam body, and the finite element method is mainly applied to the seepage analysis of the dam body. This paper uses the APDL language programming of ANSYS software to complete the seepage calculation and analysis of earth-rock dams. This paper uses the post-processing module of ANSYS to view the seepage path, seepage results and wetting line of the earth-rock dam.

An Analysis of Optimum Thickness of Inverted Filter Layer Made by Manufactured Sand

The soil stability problem caused by seepage is a hot issue in geotechnical engineering, which is widely existed in natural and artificial slope, embankment, earth-rock dam and other projects. The traditional seepage calculation only considers the saturated seepage, ignoring the unsaturated seepage, and in the design of the filter layer, the thickness of the filter layer is mainly determined by experience. This study, for above problems, finite element numerical simulation method was used to simulate different thickness of filter layer, and seepage analysis in the unsaturated zone was carried out and obtained that 0.8m was the optimal thickness of filter layer in the calculation example; due to the siphon effect of matric suction, water flow also exists in the unsaturated area, and the infiltration line is not the uppermost line in the flow network; when the free water is a little lower than the height of the corewall, it will increase the seepage flow on the corewall of the dam, intensify the seepage contact and erosion, cause damage to the dam body.

New Empirical Model for Breaching of Earth-Rock Dams

AbstractEmpirical models are widely used in dam risk analysis because they can estimate the dam breach parameters easily, which enables a quantitative analysis of the breach process to be conducted...

Assessment of geomaterial compaction using the pressure-wave fundamental frequency

Abstract Assessment of geomaterials compaction during layered filling is required for quality control of earthworks such as transportation infrastructure and earth-rock dam construction. This paper presents a new method for non-destructive assessment of geomaterial compaction based on the velocity of vertically propagating pressure- or P-wave evaluated by the detected fundamental frequency and a correlation between the P-wave velocity and the dry density. Field experiments were performed on six types of geomaterials at two dam construction sites. Vertical acceleration data were recorded by piezoelectric accelerometers installed on the drum frame during compaction. The vibration data were processed to identify the fundamental frequency for the evaluation of the P-wave velocity. The P-wave velocity was then correlated to the dry density by linear regression analysis. Results including the fundamental frequency, the P-wave velocity, and the correlations are presented. It was found that the fundamental frequency of the geomaterials can be reliably identified from the vertical acceleration signal, provided a properly configured filter is applied. The P-wave velocity values evaluated based on the fundamental frequency agree well with those assessed based on Young’s modulus, empirical relationships, or field measurement at similar conditions. The fundamental frequency was found to increase consistently with an increasing number of compaction passes, indicating that it can be an excellent indicator of compaction quality. The linear relationships established between the dry density and the P-wave velocity for the six types of geomaterials exhibit higher values of coefficient of determination than existing models based on the peak acceleration, Fourier amplitude, or acoustic wave, indicating that the fundamental frequency-based method can be a more reliable method for assessing geomaterial compaction. The proposed method has the potential to be applied for automatic assessment of geomaterial compaction in the transportation engineering field.

Slope Stability Analysis Using Genetic Simulated Annealing Algorithm in Conjunction with Finite Element Method

The calculation of factor of safety and the determination of the critical slip surface (a slip surface with the minimal factor of safety) are essential steps in stability analysis of soil slopes. In this study, a genetic simulated annealing algorithm (GSA), which combines the genetic algorithm and the simulated annealing algorithm, is proposed to quickly and accurately locate the critical slip surface of soil slopes. The corresponding factors of safety of slip surfaces are calculated based on the stress field of soil slopes that are computed by finite element method (FEM). The search ability of GSA for the critical slip surface of an earth-rock dam slope is proved to be more accurate and efficient compared with the golden-section method based on the same stress field calculated by FEM. In addition, a practical slope with complex soil layering is presented to further illustrate the reasonability of the calculation results of GSA in conjunction with FEM. The numerical simulations shows that the factor of safety and the critical slip surface determined using GSA with FEM is in good agreement with that using the shear strength reduction method.

Risk Analysis of Earth-Rock Dam Breach Based on Dynamic Bayesian Network

Despite the fact that the Bayesian network has great advantages in logical reasoning and calculation compared with the other traditional risk analysis methods, there are still obvious shortcomings in the study of dynamic risk. The risk factors of the earth-rock dam breach are complex, which vary with time during the operation period. Static risk analysis, limited to a specific period of time, cannot meet the needs of comprehensive assessment and early warning. By introducing time factors, a dynamic Bayesian network model was established to study the dynamic characteristics of dam-breach probability. Combined with the calculation of the conditional probability of nodes based on the Leaky Noisy-Or gate extended model, the reasoning results of Bayesian networks were modified by updating the data of different time nodes. Taking an earth-rock dam as an example, the results show that it has less possibility to breach and keep stable along the time axis. Moreover, the factors with vulnerability and instability were found effective, which could provide guidance for dam risk management.

Seepage analysis of clay core wall dam based on ABAQUS

The seepage analysis of earth-rock dams is required to define the seepage field as a community of saturated and unsaturated regions. The two complement each other. The motion characteristics of unsaturated seepage are relatively complex, and the influence factors are more than saturated seepage. In this paper, combined with engineering examples, the finite element numerical simulation is used to simulate the variation of the seepage field of the earth-rock dam in saturated and unsaturated seepage, and the wetting line, seepage flow and stress and strain inside the dam are obtained. The data results are reasonable and correct. It has certain reference value in the construction of anti-seepage system of earth-rock dam.

Impact of double defects on seepage behavior of geomembrane lined earth-rock dams

In this study, the unsaturated seepage theory was employed to analyze the effect of different elevations and separations of double defects in geomembrane barrier on the seepage behavior of geomembrane lined earth-rock dams. The results indicated that the separation between the defects has a significant influence on the defect-induced leakage. The increasing separation results in the increase of defect-induced leakage. When the separation reaches 3 m, the defect-induced leakage tends to decrease. The defect-induced leakage increases again when the separation is greater than 3.5 m. And defect-induced leakage increases gradually with decreasing elevation of defect, but is still in the same order of magnitude. In addition, the wetted area near the defects expands with the increasing separation between double defects. The wetted areas can be delineated by a circle, by an ellipse or by two discrete circles depending on the separation and elevation of double defects.

Finite element analysis of seepage of earth-rock dams in dry and rainy seasons

The earth-rock dams in Southeast Asia will be in long-term rainfall during the rainy season, and long-term rainfall infiltration will affect the seepage field of earth-rock dams. In this paper, COMSOL software is used to analyze the seepage field of earth-rock dam. Based on the basic differential equations such as Darcy’s law and Rechards’ equation built in software, the numerical simulation of seepage analysis is carried out. On the other hand, taking the stable seepage field as the initial condition and considering the rainfall conditions, further analysis and research on the unsteady seepage field will yield better results.

Study on quantification method for aggregate gradation of discrete Cemented Sand Gravel and Rock

As a new damming technique, Cemented sand gravel and rock damming technique could fill the gap between the earth-rock dam and the concrete dam in material and improve the construction system. The largest characteristic of this material is that it directly adopts the aggregates in the engineering field and only aggregates with a particle size above 150 mm are screened. The aggregate gradation is discrete and fluctuating, so it is significant to study the methods of quantization and characterization of aggregate grading. Based on Fuller curve, this paper quantified the variation and dispersion of aggregate gradation via using similarity coefficient of aggregate gradation, average similarity coefficient, mean average similarity coefficient and standard deviation of similarity coefficient, which has provided significant guidance for the real practice. Relevant quantization methods not only assist to differentiate the grading boundary including the thinnest and roughest graded aggregate, but also master the grading changes and predict the dispersion degree of strength of Cemented sand gravel and rock from the dispersion degree of aggregate, which could provide a scientific reference for the mixing design of Cemented sand gravel and rock