Concrete Face Rockfill Research Articles

Large-Scale Test Study on the Three-Dimensional Behavior of the Gravel–Concrete Interface of a CFR Dam

Abstract The mechanics of the interface between a concrete-face slab and cushion layer gravels plays an essential role in the stability of the concrete face of a concrete-face rockfill (CFR) dam, w...

Modeling of Seepage Flow Through Concrete Face Rockfill and Embankment Dams Using Three Heuristic Artificial Intelligence Approaches: a Comparative Study

The goal was to predict seepage flow (Q) through concrete face rockfill and embankment dams, using three artificial intelligence models, i.e., multivariate adaptive regression splines (MARS), least squares support vector machine (LSSVM), and M5 model tree (M5Tree). The three models were constructed exclusively using in situ measured data from two dams: El Agrem dam located at Jijel province, and Fontaine Gazelles dam located at Biskra province. The obtained results using artificial intelligence models were compared to those obtained using the multiple linear regression (MLR) models. We used two different input variables for developing the models: (i) the daily reservoir water level (WL) and the piezometer elevation (PL) measured at seven different piezometers (PZ1 to PZ7). The results show that the estimation accuracy for Fontaine Gazelles dam is much better than those obtained for El Agrem. All the models performed reasonably well, but the LSSVM was the most consistent predictor of seepage flow for the two data sets. The validation results showed that the LSSVM model has showed significantly better accuracy of seepage flow prediction with root mean square error (RMSE) of 0.432 L/s, mean absolute error (MAE) of 0.302 L/s and correlation coefficient R of 0.952 for Fontaine Gazelles, and RMSE of 0.544 L/s, MAE of 0.344 L/s and correlation coefficient R of 0.731 for El Agrem dam. From this study we conclude that, seepage flow is likely to vary considerably, depending on the reservoir water level, and that the proposed model can be very helpful in estimation of seepage flow, while limitations of the prediction using a standard regression model are illustrated.

Cause and Stability Analysis of Cracks in Concrete Slab of Rockfill Dam under High Temperature Difference Condition

The causes of cracks in concrete slab from the aspects of structural stress and nonstructural stress are summarized firstly. And then, based on the relationship between the stress intensity factor and the fracture toughness, a 3D finite element model of a concrete face rock fill dam, with concrete slab under partial cracking, is established to study effects of rockfill body deformation, water level and temperature change on the stress distribution. On the basis, the stability and expansion trend of a typical crack are evaluated by numerical simulation of different sizes in depth, especially the influence of the cold-air outbreak.

Evaluate the Possibility of Infrared Heat Method to Detect "Air Escape" under Concrete Roof Slabs on the Dyke and Dam by Studying Models

In irrigation works in general, concrete face rock fill and concrete roofslabs layer dams in particular, after extended use, "air escape" appears. These "air escape" (hollow layer), if not found and dealt with in time, will greatly affect the upper layer of the dam, causing soakage and leakageand shortening the life span of structures. The paper introduces several new results obtainedwhen Infrared Heat method is applied to assess the ability to detect "air escape" under concrete roof slabs on the dyke and damby studying models (convenient time to identify "air escape"; Minimum temperature gap to identify "air escape"; Minimum size of "air escape" identifiable using Infrared Heat method.
 Keywords
 Concrete roof slabs, irrigation work, "air escape", Infrared Heat method
 References
 [1] Floyd F.Sabin,Remote Sensing: Principles and Applications, Third Edition, 2007, Waveland Press, Inc.[2] Tiêu chuẩn Việt nam TCVN 8419:2010 về công trình thủy lợi - thiết kế công trình bảo vệ bờ sông để chống lũ.[3] User’s manual FLIR Ex series, Copyright 2017, FLIR Systems, Inc. All rights reserved worldwide.[4] User’s manual FLIR T4xx series, Copyright 2014, FLIR Systems, Inc. All rights reserved worldwide

Effect of Normal and Shear Interaction Stiffnesses on Three‐Dimensional Viscoplastic Creep Behaviour of a CFR Dam

Rockfill materials and foundation continuously interact with each other during lifetime of the rockfill dams. This interaction condition alters the viscoplastic behaviour of these dams in time. For this reason, examination of the time‐dependent viscoplastic interaction analyses is vital important for monitoring and evaluating of the future and safety of the rockfill dams. In this study, it is observed how the time‐dependent displacement and stress behaviour of a concrete‐faced rockfill (CFR) dam change by the effect of the normal and shear interaction spring stiffness parameters. Ilısu Dam that is the longest concrete‐faced rockfill dam in the world now and has been completed in the year 2017 is selected for the three‐dimensional (3D) creep analyses. The 3D finite difference model of this dam is modelled using FLAC3D software that is based on the finite difference method. The concrete slab, rockfill materials, foundation, and reservoir water are separately created for the 3D interaction analyses. A WIPP‐creep viscoplastic material model and a burger‐creep viscoplastic material model that are special material models for the creep analyses of rockfill dams are used for concrete slab and for rockfill materials and foundation, respectively. Totally 20 different interaction parameters (normal and shear stiffnesses) are separately defined between the rockfill materials and the foundation to represent the interaction condition. According to numerical analyses, the effect of these various interaction parameters on the viscoplastic behaviour of the Ilısu Dam is evaluated for the empty and full reservoir conditions. As a consequence, the most critical normal and shear stiffnesses’ range for creep analyses of the rockfill dams is determined. Afterwards, the long‐term viscoplastic interaction behaviour of Ilısu Dam is examined during 35 years considering this important stiffness values. Settlements, horizontal displacements, and principal stresses are evaluated for both reservoir conditions, and these results are compared with each other in detail.

高坝坝基防渗帷幕结构优化研究 Study on Optimization of Anti-Seepage Curtain Structure for High Dam Foundation

针对实际工程坝基防渗处理措施中灌浆帷幕的结构设计，既满足安全性又满足经济性问题，本文基于粒子群算法与有限元方法相结合计算满足约束条件下防渗帷幕的平均深度与等效厚度。以某高坝深厚覆盖层上的混凝土面板堆石坝为案例，首先分析二维模型中无防渗帷幕时坝基渗流场情况，得出无防渗帷幕时坝基透水率相对较高，容易产生渗透破环，因此必须在基岩中进行灌浆以降低坝基渗流量。研究发现：粒子群算法在帷幕结构优化中的可行性和适用性，得出随着迭代次数的增加，粒子不断向最优解靠近，目标函数(工程造价)随着迭代次数的增大逐渐减小并趋于平缓，该研究成果可用于对工程中帷幕灌浆的结构设计提供参考。 The design of grouting curtain in seepage control measures of the dam foundation of the actual project not only meets the safety, but also meets the economic problems. In this paper, based on the combination of particle swarm optimization and finite element method, the average depth and equivalent thickness of impervious curtain under the constraint condition were calculated for concrete face rock fill dam on deep overburden. Firstly, the seepage field of the dam foundation in the 2D model was analyzed, and the permeability of the dam foundation is relatively high when it has no curtain, and it is easy to produce osmotic rupture. It is therefore necessary to perform grouting in the bedrock to reduce dam foundation seepage. The particle swarm optimization (PSO) is feasible and applicable in the optimization of curtain structures. It is concluded that as the number of iterations increases, the particles are close to the optimal solution, and the objective function (engineering cost) is gradually reduced and tends to be gentle as the number of iterations increases. The research results can be used to provide reference for the structural design of curtain grouting in engineering.

FEASIBILITY, VALUE ENGINEERING, AND ROCK FILL DAMS CONSTRUCTION: A CASE STUDY

In this study details of structure of Shahr-e-Bijar concrete-faced rock-fill (CFRD) in Guilan (a province in the north of Iran) and the reasons to select CFRD are presented. To select CFRD first by investigation of 18 different types of dam based on local availability of materials and the ability of constructing by available technology (both Iranian and foreign available technology) six types of them were selected for value engineering. By attention to construction costs, execution time, durability, reliability and performance and ease of construction and operation; and also, the importance coefficient for local government were selected for value engineering. After that 3 types of dam structure (vertical clay core dam, asphalt core dam, and CFRD) had maximum scores. Finally, rock fill dam with concrete surface is selected because despite being more expensive in some cases than other options, it could be considered as a successful dam construction option in Iran because the construction needs no foreign technology and its technology of construction and materials are available. On the other hand, the necessary time for the project is 24 months. The main objective of this project is to avoid time loosing because of materials availability and local technology that needs no finance transferring and no foreign contract that may not be affected by some political condition that delays the project.

Seepage Control in a High Concrete Face-Rock Fill Dam Based on the Node Virtual Flow Method

The seepage control system of a high Concrete Face Rock-Fill Dam (CFRD) may have anti-seepage deficiencies during both construction and operation. In order to solve these, the three-dimensional Finite Element Method (FEM) model was built based on dam body filling, anti-seepage system, defect location and bedrock distribution. The seepage field simulation and computation were carried out using an improved node virtual flux method and the zero-thickness crack model theory. The water head distribution, seepage lines and dam leakage field were obtained by simulation under different conditions, and the seepage characteristics during construction and operation were analyzed systematically. Taking a high CFRD as an example, the results showed that during the flood-control construction period, the incomplete nature of the dam face slab can lead to seepage damage near the second seepage control line. Moreover, during operation period; the seepage control system was still effective when the dam face slab was incomplete.

Reservoir water effects on earthquake performance evaluation of Torul Concrete-Faced Rockfill Dam

This study presents earthquake performance analysis of the Torul Concrete-Faced Rockfill (CFR) Dam with two-dimensional dam-soil and dam-soil-reservoir finite element models. The Lagrangian approach was used with fluid elements to model impounded water. The interface elements were used to simulate the slippage between the concrete face slab and the rockfill. The horizontal component of the 1992 Erzincan earthquake, with a peak ground acceleration of 0.515g, was considered in time-history analysis. The Drucker-Prager model was preferred in nonlinear analysis of the concrete slab, rockfill and foundation soil. The maximum principal stresses and the maximum displacements in two opposite directions were compared by the height of the concrete slab according to linear time-history analysis to reveal the effect of reservoir water. The changes of critical displacements and principal stresses with time are also shown in this paper. According to linear and nonlinear time-history analysis, the effect of the reservoir water on the earthquake performance of the Torul CFR Dam was investigated and the possible damage situation was examined. The results show that the hydrodynamic pressure of reservoir water leads to an increase in the maximum displacements and principal stresses of the dam and reduces the earthquake performance of the dam. Although the linear time-history analysis demonstrates that the earthquake causes a momentous damage to the concrete slab of the Torul CFR Dam, the nonlinear time-history analysis shows that no evident damage occurs in either reservoir case.

Hazard and seismic reinforcement analysis for typical large dams following the Wenchuan earthquake

The primary aim of this research is to analyze the hazards and seismic performance of reservoirs and typical large dams based on a field investigation following the Wenchuan 8.0 earthquake. The current seismic performance standards being achieved are discussed and further suggestions are given for super high dams. Based on field investigations, statistics are also given on damaged small reservoirs and damage severities, due to the many various types of earthquake threat. It is of interest to note that the major structures of the medium-sized hydropower stations on the Minjiang river did withstand the Wenchuan earthquake, despite earthquake intensity exceeding engineering design expectations. All the dams remained overall stable. The Shapai roller-compacted concrete (RCC) arch dam and the Zipingpu concrete-faced rockfill (CFR) dam suffered damage. The main earthquake-induced hazards to the dam structures and to both abutments are detailed. Case study analyses of the hazards and reinforcement provision revealed that: 1) The Wenchuan earthquake proved very dangerous for small reservoirs, with destroyed reservoirs widely distributed. The risk of failure of small dams can be classified into three levels based on field investigation. 2) The damage to and behavior of the large dams in the area affected by the earthquake prove that the Chinese codes relating to the seismic design of large dams are appropriate. 3) Appropriate reinforcement can increase the overall stiffness of abutments, riverbed foundation and the adjacent slopes, further improving the seismic performance of dams. 4) The design and management of emergency responses, to cope with extreme conditions, should be improved, and a unified response platform, covering all hydropower engineering projects in each valley should be established. The effects to be expected and the seismic design measures to be taken still pose great challenges for engineers in respect of large dams.

Non-linear earthquake response of CFR DAM–reservoir–foundation systems

The aim of this article is to clearly show linear and non-linear earthquake behaviour of a concrete-faced rockfill (CFR) dam. For this purpose, a typical CFR dam model is considered with its reservoir water. Reservoir water is modelled by using fluid finite elements based on the Lagrangian approach. Free-field surface motions recorded during earthquakes are deconvolved to the base of the foundation from the soil layers for earthquake analysis. Geometrically and materially non-linear behaviours of the dam are considered in the finite element analysis. The Drucker–Prager model is used for concrete slab, and the multi-linear kinematic hardening model is used for rockfill and foundation rock in the materially non-linear analysis. Non-linear behaviour of the rockfill is obtained by the uniaxial stress–strain relation. Stress–strain curve of the rockfill is obtained using the shear modulus–shear strain relation produced for the gravels. Various joints in the CFR dam are modelled considering welded and friction contacts. In this study, one-dimensional surface-to-surface contact–target element pair based on the Coulomb's friction law provides friction. According to this study, maximum displacements appear when the friction is considered in the joints. In addition, hydrodynamic pressure increases the horizontal displacements of the dam. The horizontal displacements also increase by the effect of the non-linear behaviour of the rockfill and concrete slab.

Design and Application of Concrete Faced Rock-Fill Dam Numerical Simulation Analysis Program

Reviewed the various constitutive mode of concrete faced rock-fill dam. Basis on the complex physical characteristic of filled the material and the framework of dam, a method of computer is given, introduced into the program of the concrete face rock-fill dam calculation with FORTRAN language on the ANSYS software. It is used to simulate two and three-dimensional nonlinear computation and compute figure simulation in the construction procedure and operation period for the concrete face rock fill dam, the result was intuitionist clarity.

Prediction of Concrete Faced Rock Fill Dams Settlements Using Genetic Programming Algorithm

In the present study a Genetic Programing model (GP) proposed for the prediction of relative crest settlement of concrete faced rock fill dams. To this end information of 30 large dams constructed in seven countries across the world is gathered with their reported settlements. The results showed that the GP model is able to estimate the dam settlement properly based on four properties, void ratio of dam’s body (e), height (H), vertical deformation modulus (Ev) and shape factor (Sc) of the dam. For verification of the model applicability, obtained results compared with other research methods such as Clements’s formula and the finite element model. The comparison showed that in all cases the GP model led to be more accurate than those of performed in literature. Also a proper compatibility between the GP model and the finite element model was perceived.

Nonlinear finite element reliability analysis of Concrete-Faced Rockfill (CFR) dams under static effects

The response of concrete slab on Concrete-Faced Rockfill (CFR) dams is very important. This study investigates the reliability of the concrete slab on a CFR dam by the improved Rackwitz–Fiessler method under static loads. For this purpose, ANSYS finite element analysis software and FERUM reliability analysis program are combined with direct coupled method and response surface method. Reliability index and probability of failure of the concrete are computed in the all critical points of the concrete slab by dam height. This study is also expanded for the reliability of CFR dams including different concrete slab thickness. In addition to the linear behavior, geometrically and materially non-linear responses of the dam are considered in the finite element analysis which is performed with reliability analysis. The Drucker–Prager method and the multi linear kinematic hardening method are, respectively, used for concrete slab and for rockfill and foundation rock. Finite element model used in the analyses includes dam–reservoir–foundation interaction. Reservoir water is modeled by the Lagrangian approach. Welded and friction contact based on the Coulomb’s friction law are considered in the joints of the dam. One-dimensional two noded contact elements are used to define friction. The self-weight of the dam and the hydrostatic pressure of the reservoir water are considered in the numerical solutions. According to this study, hydrostatic pressure, nonlinear response of the rockfill and the decrease in the concrete slab thickness reduce the reliability of the concrete slab of the CFR dam. Besides, the CFR dam models including friction are safer than the models including welded contact in the joints.

Primary Engineering Geological for Shuibuya Underground Power Station and their Treatment

The Shuibuya hydropower station is located in Badong County in the middle reach of Qingjiang River. It is the first cascaded project in Qingjiang mainstream. The Project consists of a concrete faced rock fill dam (CFRD), underground power house, chute spillway on the left bank, and the sluice tunnel on the right bank. The dam is 233m high, which is the highest of its kind in the world at present. The installed capacity and annual output of Shuibuya Power Plant are 4×460MW and 3.92 GWh respectively. The rock mass of foundation of Shuibuya project is a type of stratified sedimentation rock mass is composed of interbedded stratum by weak layers and hard layers. To solve engineering geological problem is difficult and challenging. For example, the intake slope of Shuibuya hydropower diversion tunnel was a landslide, and diversion tunnel outlet is located at the toe of Maya slope with 360m high, rock mass of the underground powerhouse caverns are soft and hard rock inter-layered, with multi-structural planes, multi-shear zones, and the lithology of rock is highly krast. Some researchs and geological treatments were performed during the geological exploitation and construction, which is fundamental and primary.

Study on Application of Extrusion Concrete Side Wall in Concrete Face Rock Fill Dam

Compared with the traditional upstream dam slope construction method, the extrusion side wall technology has many advantages. such as less process steps, little interference, quick construction speed etc ,So it arouse more and more attention in the engineer design and construction fields . The technology of extrusion concrete side wall applied to the construction of concrete face rockfill dam in the Bailian river storage power station, machinery and equipment were used on the cushion material to form a concrete wall extrusion , which avoid the traditional process of Ultra-filled cushion material, rolling slopes, cut slopes and other complicated process, not only ensure the quality, but also improve the stress state of the panel.

Modeling coupled processes of non-steady seepage flow and non-linear deformation for a concrete-faced rockfill dam

A coupled non-linear elastic deformation and non-steady seepage flow model was established for performance assessment of the concrete-faced rockfill (CFR) dams. The deformation behaviors of the rockfills and the soil–structure interfaces were modeled with the Duncan–Chang model and Desai’s thin-layer elements, respectively. The seepage flow process was characterized with a newly-developed parabolic variational inequality formulation of the Signorini’s condition. The deformation-dependent permeability of the rockfills was characterized by a calibrated Kozeny–Carman model that considered the influence of confining pressure on porosity. The proposed model was applied to capture the seepage flow and deformation behaviors of the Shuibuya CFR dam in China.

Probabilistic nonlinear analysis of CFR dams by MCS using Response Surface Method

This paper presents the probabilistic analysis of concrete-faced rockfill (CFR) dams according to the Monte Carlo Simulation (MCS) results which are obtained through the Response Surface Method (RSM). ANSYS finite element program is used to get displacement and principal stress components. First of all, some parametric studies are performed according to the simple and representative finite element model of dam body to obtain the optimum approximate model. Secondly, a sensitivity analysis is performed to get the most effective parameters on dam response. Then, RSM is used to obtain the approximate function through the selected parameters. After the performed analyses, star experimental design with quadratic function without mixed terms according to the k = 1 is determined as the most appropriate model. Finally, dam-foundation-reservoir interaction finite element model is constituted and probabilistic analyses are performed with MCS using the selected parameters, sampling method, function and arbitrary factor under gravity load for empty and full reservoir conditions. Geometrically and materially nonlinearity are considered in the analysis of dam-foundation-reservoir interaction system. Reservoir water is modeled by fluid finite elements based on the Lagrangian approach. Structural connections are modeled as welded contact and friction contact based on Coulomb’s friction law. Probabilistic displacements and stresses are presented and compared with deterministic results.

Evaluation of the dynamic response of the Damlapinar CFR dam

Concrete faced rock-fill (CFR) dams are now very popular. The structural complexity of these dams and the high risk associated with the social and environmental consequences of failures require very reliable analyses of their performance, especially as regards seismic loading. In this paper, a dynamic analysis procedure for CFR dams is proposed and described, using the Damlapinar CFR dam as a case study. The acceleration time history and maximum horizontal peak ground acceleration values were developed based on maximum credible earthquakes over 50 years from nearby seismic sources. Numerical studies showed that the Damlapinar CFR dam will remain stable under the maximum credible earthquake with a peak ground acceleration of 0.15 g. According to the numerical results, earthquake-induced deformations of the dam are expected to be within the safety margins determined by the Ministry of Public Works and Settlement, Turkey. The results also indicate that a non-linear analysis capable of capturing dominant non-linear mechanisms can be used to assess the stability of CFR dams.

Seismic failure probability of concrete slab on CFR dams with welded and friction contacts by response surface method

In this study, failure probability of the concrete slab on concrete-faced rockfill (CFR) dams with welded and friction contact is investigated under earthquake effects by reliability analysis. For this purpose, Torul CFR dam is selected as an example and numerical solutions are performed by considering combination of reliability analysis–finite element method. 1992 Erzincan earthquake acceleration record is used in the finite element analysis considering deconvolved-base rock input model. In this model, the ground motion to be applied to the foundation base rock is obtained by deconvolution of the free-field surface record. In the materially nonlinear analysis, Drucker–Prager model is used for concrete slab and multi-linear kinematic hardening model is utilized for rockfill. Geometrically nonlinearity is also taken into account. Viscous boundary conditions are defined in the finite element model for both foundation soil and reservoir water. The hydrodynamic pressure of the reservoir water is considered using 2D fluid finite elements based on the Lagrangian approach. Both welded contact and friction contact based on the Coulomb’s friction law are defined in the structural connections. Improved Rackwitz–Fiessler method is used with response surface method in the reliability analysis. The tensile and compression strengths of the concrete slab are utilized in the implicit limit state functions considering various thicknesses. The probability of failure of the most critical points in the concrete slab is obtained. According to this study, the probabilities of failure obtained from the CFR dam including friction contact are lower. When the welded contact is considered in joints, the probability of failure of the concrete slab is 1 due to tensile stress limit state and compression stress limit state only if concrete slab is linear. The most critical probability of failure of the concrete slab appears in the case that the concrete slab is linear and rockfill is materially nonlinear. The probability of failure of the concrete slab decreases if the nonlinearity of the concrete is considered. Also, hydrodynamic pressure decreases the reliability of the concrete slab.