Face Rockfill Dam Research Articles

Rheology Test and Finite Element Analysis: A Case Study of a Rockfill Dam in China

Rheology often occurs in the dam rockfill deformation. In this paper, we carried out a large-scale triaxial rheological test for the tuff rockfill materials of a concrete faced rockfill dam in China, and then obtained the parameters of the seven parameter rheology model. Finally, we analyzed the dam rheology using the three-dimensional finite element model. The results show that the dam settlement, horizontal displacement, face deflection and the displacement of the joints around the face slab are all obviously increased when considering the rheological behavior of the rockfill. We find that the calculated settlement of the dam body is in good agreement with the filed measured value when the dam is completed, and the maximum settlement during the impoundment period is within the normal range.

A Comprehensive Evaluation Method of Safety Behavior of Concrete Face Rockfill Dam Based on Regression Relationship Method and Fuzzy Recognition Model

The concrete face rockfill dam (CFRD) generally encounters structural health problems during long-term operation. Therefore, it is necessary to study the safety evaluation of CFRDs. This paper proposes a comprehensive evaluation method for the safety behavior of CFRDs on the basis of regression relationship method and fuzzy recognition model. The method of sub-index safety evaluation is established by using regression relationship method. The multiplication scale method was adopted to determine the sub-indexes weight. In combineing of sub-index safety evaluation value and sub-indexes comprehensive weight, the fuzzy recognition model is used to determine the comprehensive evaluation grade of dam safety. Safety evaluation of several CFRDs were evaluated by the method proposed in this paper and exisiting safety evaluated method to verify reasonable and rationality of the method.

Predicting Maximum Crest Settlement of Concrete Face Rockfill Dams Using a New Ensemble Learning Model

Deformation assessment and control are essential issues in the construction of concrete face rockfill dams (CFRDs). The design and construction of CFRDs require deformation behavior that can be estimated rapidly to support engineering optimization and safety assessment. Based on 87 case histories of in-service CFRDs, a new ensemble learning model has been developed to predict maximum crest settlement (CS) of CFRDs. The model is based on the support vector machine regression algorithm (SVR) combined with multiple variables, and then the foundation model is integrated by the weighted average integration method. It is demonstrated here that the new ensemble learning model weakens the nonlinear characteristics of case data, makes up for the instability of single regression algorithm, improves the generalization ability, and provides a new idea for predicting the CS of CFRDs.

Stress and Deformation Analysis of High Concrete Face Rockfill Dam Based on COMSOL Multiphysics

In order to study the stress and deformation characteristics of the high concrete face rockfill dam over 100 meters, in this paper, Duncan-Zhang E-B nonlinear elastic hyperbolic model is adopted, the finite element software COMSOL Multiphysics is used to establish the model and the MATLAB function is used for secondary development to analyze the stress and deformation of the concrete face rockfill dam of the Panshitou reservoir. The stress and deformation characteristics of the concrete face rockfill dam at the completion period, normal water storage condition, designed flood level condition and checked flood level condition are obtained through analysis, which provide theoretical guidance for the construction and operation of the high concrete face rockfill dam of more than 100 meters.

Multiple Nonlinear Regression Models for Predicting Deformation Behavior of Concrete-Face Rockfill Dams

Abstract Deformation assessment and control are important issues in the construction of concrete face rockfill dams (CFRDs). The design and construction of CFRDs require deformation behavior that c...

Study on seismic failure probability of high earth-rock dam considering dam body deformation and slope stability

The reliability analysis is one of the main methods for the quantitative analysis of the safety in the geotechnical engineering. This method can provide the failure probability with a clear physical meaning. Due to the complex structure of high earth-rock dams and the non-linear characteristics of the material properties, it is very difficult to perform the reliability analysis on such large nonlinear structures. Currently, there are few studies on the reliability analysis of high earth-rock dams that consider the earthquakes, the dam body deformation and the dam slope stability at the same time. In this paper, the dam cracks generated by the earthquakes are used as the criteria for the dam body seismic deformation evaluation, and the inclination method is adopted for the dam body seismic deformation analysis. The simplified Bishop method combined with the ratio of the safety margin method is used to analyze the dam slope stability. In order to consider the soil material properties, the thickness of the compressible soil layer and the uncertainty of the earthquakes, a seismic failure probability analysis method for evaluating the seismic danger of high earth-rock dams considering the dam body deformation and the dam slope stability is established based on the reliability theory. Taking a concrete face rockfill dam as an example, the method is used to analyze the seismic failure probability of the dam during the design reference period. It provides the reference for the seismic design and the risk analysis, and establishes the risk level of high earth-rock dams.

Behavior of rockfill dam under complex terrain condition

The behavior of concrete face rockfill dam (CFRD) is more dependent on valley terrain than rockfill deformation. The objectives of this study are to research the influence of valley topography condition on the deformation and stress of a CFRD, especially with relevance to the behavior of face slab under complex terrain conditions. First, the research on the effect of valley shape factor on perimeter joint deformation used monitoring data with a combined total of 22 CFRDs from 8 countries. The results show that the perimeter joint deformation decreases nonlinearly with increasing valley shape factor A/H2. A/H2 = 2 ~ 4 or L/H = 2 ~ 5 can be considered an intervenient valley which contains both characteristics of the narrow and wide valley. Then, numerical analysis is applied to predict the behavior of Nam Ngum 2, a 182-m-high concrete face rockfill dam, during initial impoundment via a three-dimensional finite element analysis. A series of finite element analyses aimed at investigating the influence of the intervenient valley and complex topography condition which in turn depends on slope angle and angle mutant of the abutment on stress and deformation of concrete face slab on CFRD. All results indicate that the arch effect is crucial to deformation and stress of the CFRD in the intervenient scale of valley shape factor. Steeper slope and convex catastrophe point in abutment rapidly aggravate the tensile stress of the face slab and the deformation of the joints, which threaten the safety of the impervious system of CFRD. The hardening soil model is used in the nonlinear analysis for rockfill, and the results show that a good agreement between computed results and dam field monitoring data can be achieved.

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.

Prediction, monitoring, and interpretation of dam leakage flow via adaptative kernel extreme learning machine

The magnitude of leakage in the dam body and its foundation can be used as an important indicator in dam risk management. This study presents a data mining and monitoring framework for safety control of the dam leakage flow. First, the influencing factors in dam leakage flow are investigated. Second, a kernel extreme learning machine (KELM) is trained to predict dam leakage, where the parameters are optimized adaptively by parallel multi-population Jaya algorithm. Finally, a novel global sensitivity analysis is proposed to evaluate the relative importance of each input variable based on the KELM. Monitoring data of leakage flow from the concrete face rockfill dam in a pumped-storage power station is used for modeling and verification. The simulated results of the case study reveal that KELM achieves a satisfactory prediction of the leakage flow. It is also found that the water level fluctuation and rainfall have a significant impact on leakage magnitude. The sensitivity analysis provides a useful qualitative metric of dam leakage, which is of great value for dam safety monitoring and operation.

Seepage control effect of a concrete face rockfill dam on a deep overburden foundation

This study addresses the seepage field characteristics of a concrete face rockfill dam (CFRD) built on a deep overburden foundation. The seepage barriers and anti-seepage effect for the dam and foundation are analysed using the finite element method (FEM). Based on the numerical analysis, it is concluded that the anti-seepage wall in the overburden foundation can achieve good anti-seepage effect. A relative depth ratio of 0.7 between the wall and overburden is suggested when a suspended cut-off wall is used. The permeability of the overburden has a significant effect on the foundation seepage field.

A Biological Immune Mechanism-Based Quantum PSO Algorithm and Its Application in Back Analysis for Seepage Parameters

Back analysis for seepage parameters is a classic issue in hydraulic engineering seepage calculations. Considering the characteristics of inversion problems, including high dimensionality, numerous local optimal values, poor convergence performance, and excessive calculation time, a biological immune mechanism-based quantum particle swarm optimization (IQPSO) algorithm was proposed to solve the inversion problem. By introducing a concentration regulation strategy to improve the population diversity and a vaccination strategy to accelerate the convergence rate, the modified algorithm overcame the shortcomings of traditional PSO which can easily fall into a local optimum. Furthermore, a simple multicore parallel computation strategy was applied to reduce computation time. The effectiveness and practicability of IQPSO were evaluated by numerical experiments. In this paper, taking one concrete face rock-fill dam (CFRD) as a case, a back analysis for seepage parameters was accomplished by utilizing the proposed optimization algorithm and the steady seepage field of the dam was analysed by the finite element method (FEM). Compared with immune PSO and quantum PSO, the proposed algorithm had better global search ability, convergence performance, and calculation rate. The optimized back analysis could obtain the permeability coefficient of CFRD with high accuracy.

Monitoring and analysis of external deformation of face rock-fill dam during initial storage period

During the initial storage period of the face rock-fill dam, its physical and mechanical properties will not be in a fully controlled state when it is subjected to the test of water loads, which may cause certain safety risks. The stability of the dam body and slope can be analyzed by studying the external deformation changes of the face rock-fill dam after water storage. This article analyzes the external deformation monitoring data of the Hekou Village Reservoir’s face rock-fill dam during the initial storage period, and it reveals the general rule of the external deformation of the face rock-fill dam after water storage. The results also show that the dam is safe after storing water and have certain reference significance for other similar projects.

Theory of stress-strain state of concrete faced rockfill dams

In spite of the fact that concrete faced rockfill dams began to be used long ago; their designing is based on empirical approaches and there is still no common theoretical concept about peculiarities of their operation. With the aid of numerical modeling the author studied conditions of forming stress-strain state (SSS) of a concrete face with consideration of impact of various factors. The used methodology of analysis took into account operation of the face not as that of the plate but as a 3D structure interacting with the dam body in a complicated way. This permitted obtaining new knowledge about the face operation. It was revealed that friction farces at the contact of the face with the dam body play the main role in SSS formation. Due to friction the concrete face perceives not only deformations of cross bending but also longitudinal forces and deformations of longitudinal bending. The most dangerous is the face lower section where the face is subject to tensile longitudinal force and longitudinal bending, which may result in appearance of transversal cracks in the face. Considerable compressive forces perceive the face in the direction from the bank to the bank. The new theoretical concept about the concrete face SSS dictates reconsideration of approaches to designing of concrete face rockfill dams. For decrease of tensile longitudinal force, the pattern of rockfill zoning in the dam body should not allow considerable difference in deformation of the dam zones; also it is necessary to decrease friction on the contact of the face with the under-face zone. “Soft” vertical joints should be arranged to decrease compression in the face in the direction from one side to the other side.

Leakage Detection of CFRDs Based on a Multi-source Information Fusion Method

Dam leakage is one of the most important failure causes of concrete face rockfill dams (CFRDs). Causes of dam leakage problems are various and hard to target due to the non-homogeneity of dam materials and the multi-dimensional deformation of CFRDs. This paper effectively performs multi-source information fusion of the safety monitoring, underwater sonar scanning, underwater high-definition cameras, and connection tests to propose a method for seepage detections of concrete face rockfill dams. The proposed method has been successfully applied in the seepage detection of a CFRD.

Research on dam leakage detection based on visual and acoustic integration: a case study of CFRD

Many safety issues can arise during the long operation time of dams because of various internal and external factors, among which dam leakage problems happen frequently. Dam leakage not only affects the normal functions of a dam, such as power generation, water supply, and irrigation, but also weakens the flood control ability of the structure and increases the risk of dam failure. According to the existing problems in concrete face rockfill dam(CFRD) leakage detection, an integrated leakage detection technology is proposed in this paper. The proposed technology can analyze the dam safety monitoring data and then combine the high-precision sonar and underwater robot detection to provide solutions for dam leakage problems.

A Novel Seepage Safety Monitoring Model of CFRD with Slab Cracks Using Monitoring Data

The traditional regression model usually simulates the influence of water pressure and rainfall in the early stage based on experience, but it is not suitable. To solve this problem, the normal distribution curve is used to simulate the lagging effect of water pressure and rainfall on dam seepage. In view of problem of slab cracks, the influence of cracks on seepage is analyzed. In this paper, a safety monitoring model for concrete face rockfill dam (CFRD) seepage with cracks considering the lagging effect is proposed, in which slab cracks are considered as an influencing factor. The radial basis function neural network (RBFNN) optimized by genetic algorithm (GA) is used to establish a safety monitoring model for a CFRD seepage. Seepage of the dam is predicted by this model, whose results are similar to the monitoring data, which indicates that the method has certain applicability. Through the analysis of the proportion of factors affecting CFRD seepage, it is found that the rainfall component has the greatest impact on the total seepage, accounting for more than 50%, and the crack component accounts for about 10%. Finally, through the cloud model, the monitoring index of CFRD seepage is worked out, which has certain guiding significance for the treatment of abnormal seepage monitoring data.

A new method for dynamically estimating long-term seepage failure frequency for high concrete faced rockfill dams

Failure frequency of a dam varies greatly with reservoir water level and time. It is important but difficult to dynamically estimate failure frequency of high concrete faced rockfill dams (CFRDs) merely based on the probabilistic approach due to limited failure cases of high CFRDs. In this study, a new method is developed for dynamically estimating the long-term revolution of seepage failure frequency of high CFRDs by combining an analogical approach with the Bayesian approach. A simple and precise seepage generalized method and a parameter named defect parameter are introduced to provide the basis of comparison between the dam of interest and the accumulated database of high CFRDs. Using the cumulative probability distribution from the database, the correlation between annual seepage failure frequency and defect parameter is established. A high CFRD case in China with an operation history of slab breakage and reinforcement is selected as an example to illustrate the applicability of the new method. It is verified that the variation tendency of safety level of high CFRD is well simulated through the annual seepage failure frequency calculated by the newly proposed method.

Distribution and Variation of Earth Pressure Applied on Submerged Toe-Retaining Walls in Rockfill Dam Engineering

AbstractA high concrete gravity retaining wall is usually built at the toe of concrete face rockfill dams to accommodate the toe plinth, to avoid adverse natural conditions or excessive excavation....

Safety evaluation with observational data and numerical analysis of Langyashan reinforced concrete face rockfill dam

Deformation characteristics of rockfill and stress condition of slabs play important roles in the safety of concrete face rockfill dam (CFRD). In this study, an analysis based on monitored data and numerical simulation is conducted to evaluate the performance condition of Langyashan CFRD, which is built on a wide valley and has a mansard dam axis. The observational rockfill settlement is analyzed firstly, then a numerical model is established in accordance with the practical engineering. The numerical results of the rockfill settlement exhibit favorable consistency with similar projects or measured data in both construction and operation stages. Furthermore, the deflections and stress states of the face slabs are analyzed, and the effect of rockfill deformation and temperature variations are recognized as the main influence factors. The potential area of the face slabs vulnerable to cracks is predicted based on the stress state. The numerical results provide a reference for safety monitoring and inspection in the future operation.

Plastic-damage analysis of concrete cutoff wall for a concrete face rockfill dam

Through in situ measurement records and numerical analysis, this work investigated the behaviour of a concrete cutoff wall for a concrete face rockfill dam built on an alluvium foundation. Monitoring records were obtained from a detailed monitoring system. A three-dimensional numerical model that uses a plastic-damage model for the stress–strain relationship of concrete was developed to predict the behaviour of the concrete cutoff wall. A coupled hydro-mechanical (HM) method was adopted to characterise the HM coupling effect of the dam and the alluvium foundation. The dam construction and the subsequent reservoir-filling processes were simulated in the numerical model. The results were compared with in situ measurements to validate the numerical model. The loading mechanism, stress and deformation behaviour, damage distribution and cracking of the cutoff wall were analysed. The wall behaviour, especially with relevance to the walls for dams with corewalls or inclined corewalls, and the effects of several factors on wall behaviour were investigated.