Zipingpu Concrete Face Rockfill Dam Research Articles

Plasticity inverse analysis for Zipingpu concrete-faced rockfill dam based on advanced cloud surrogate model via improved Jaya optimization algorithm

A notable prerequisite for state assessments of earth-rockfill dams is a reasonable and accurate description of the deformation. However, due to the complexity of rockfill, its mechanical properties are often difficult to fully describe using the forward finite element method (FEM). The result of FEM depends on the constitutive model and its parameters’ selection usually obtained empirically or from indoor tests. In this paper, the improved Jaya optimization algorithm (iJaya) is combined with the advanced cloud surrogate model (ACSM) to perform inverse analysis, which has great advantages in computational speed and accuracy. The generalized plastic model (GPM) is chosen for simulation and its parameters are analyzed. Finally, the deformation field of the Zipingpu Dam is reconstructed. The results show that the ACSM can greatly replace the FEM even using GPM, achieving high prediction accuracy and reduced computation time. iJaya-ACSM can also identify the parameters of the GPM quickly and correctly. The deformation of ERDs can be well simulated based on the inverted parameters, which could help to know the state of the whole dam body. In conclusion, the proposed inverse method is promising in analyzing the deformation of ERDs.

A parabolic model and an iterative algorithm for the slab-cushion interface and the application in simulating the dynamic separation between the face slabs and cushion layer

The new damage phenomenon of the Zipingpu concrete-faced rock-fill dam (CFRD) in the 5.12 Wenchuan earthquake has introduced new topics to the study of seismic failure mechanisms and numerical simulation methods of high CFRDs. With respect to the large-scale contact separation between the face slabs and the cushion layer after the earthquake, the conventional method of directly assigning constant values ​​to the normal stiffness of the interface element can only qualitatively reflect the separated or closed state of the interface. In this article, a parabolic model for the normal stiffness of the interface is proposed, and an iterative algorithm for its optimal value is established based on the contact states. Combined with a generalised plasticity constitutive model, the 3 D finite element (FE) coupling analysis of the Zipingpu Dam is performed. The results show good agreements between the numerical calculations and field measurement conclusions. In addition, the opening and closing processes of the interface during the earthquake reproduce the dynamic face-slabs separation situation. It is indicated that the proposed constitutive model and the iterative algorithm can basically realise the quantitative estimation for the range and depth of the separation, providing a reliable method for the seismic analysis of high CFRDs.

Inversion of permanent deformation parameters of neural network based on bee colony optimization algorithm

In this research, a method of artificial bee colony algorithm was proposed to optimize BP neural network parameters and then introduced to parameter inversion of geotechnical engineering. The method is based on the research and analysis of permanent deformation of geotechnical earthquake engineering and aimed at addressing the shortages of BP neural network which is slow to converge and may easily get minimum value. This method not only strengthens the global optimization ability of bee colony optimization algorithm, but also reflects the high accuracy of predicting nonlinear problems of BP neural network and the strong generalization ability. The proposed method also improves the prediction accuracy This new proposed method was validated by using the earthquake data of Zipingpu concrete faced rockfill dam in WenChuan earthquack. The results showed that this method can better solve the problem of permanent deformation parameters and can be extended to inversion predict of the same kind.

State of Art of Seismic Design for CFRD From Earthquake-induced Damage of Zipingpu Dam

Based on the detailed in-situ investigations and analyses of earthquake-induced damage of Zipingpu CFRD (Concrete Faced Rock-fill Dam) after the ‘5.12’ Wenchuan earthquake in China, some available guidelines and experiences for seismic design of CFRD with the height above 200 m which will be built in high seismicity area can be obtained. As we know, the Zipingpu CFRD subjected to the strong earthquake with magnitude of IX suffers a little damage and operates well after repair, it is proved that reasonable seismic design can prevent the CFRD dams from severe damage or collapse during strong earthquake. The key parts of seismic design for CFRD located high seismic area mainly contain that: 1) protection of dam crest and slopes, 2) improving tensile and compressive strength of vertical joints, 3) seismic design of horizontal construction joint, 4) reducing earthquake-induced deformation, etc.

Seismic responses of high concrete face rockfill dams: A case study

Seismic responses of the Zipingpu concrete face rockfill dam were analyzed using the finite element method. The dynamic behavior of rockfill materials was modeled with a viscoelastic model and an empirical permanent strain model. The relevant parameters were obtained either by back analysis using the field observations or by reference to parameters of similar rockfill materials. The acceleration responses of the dam, the distribution of earthquake-induced settlement, and the gap propagation under the concrete slabs caused by the settlement of the dam were analyzed and compared with site investigations or relevant studies. The mechanism of failure of horizontal construction joints was also analyzed based on numerical results and site observations. Numerical results show that the input accelerations were considerably amplified near the top of the dam, and the strong shaking resulted in considerable settlement of the rockfill materials, with a maximum value exceeding 90 cm at the crest. As a result of the settlement of rockfill materials, the third-stage concrete slabs were separated from the cushion layer. The rotation of the cantilever slabs about the contacting regions, under the combined action of gravity and seismic inertial forces, led to the failure of the construction joints and tensile cracks appeared above the construction joints. The effectiveness and limitations of the so-called equivalent linear method are also discussed.

Numerical simulation of the separation between concrete face slabs and cushion layer of Zipingpu dam during the Wenchuan earthquake

The Zipingpu concrete-faced rockfill dam (CFRD) experienced strong ground motion from the 2008 Wenchuan earthquake. Separation between concrete face slabs and the cushion layer was observed after the earthquake. The separation voids under the stage III slabs make up 55% of the total area of the stage III slabs. The observed maximum height of the separation voids was nearly 23 cm at the top of the stage III slabs. Separation voids were also observed locally below the top of stage II slabs near the left abutment, with a maximum height of 7 cm. In this study, a static and dynamic elasto-plastic finite element analysis on Zipingpu CFRD was conducted to capture the separation during the Wenchuan earthquake. The rockfill materials were described using a state-dependent elasto-plastic model that considered particle breakage. The model parameters of rockfill materials were obtained from feedback analysis. The numerical results were largely consistent with the field measurements during construction and after the Wenchuan earthquake. A three-dimensional state-dependent elasto-plastic model that can trace the separation and re-contact of a soil-structure interface was employed to investigate the interaction between concrete face slabs and a cushion layer. The analysis showed the distribution of separation voids observed in the Zipingpu CFRD has a close relationship to the water level and slab dislocations at the time of the earthquake. The phenomenon of the separation from the Wenchuan earthquake was successfully captured by the proposed numerical procedure.

Stress-dilatancy of Zipingpu gravel in triaxial compression tests

Experimental investigations of the dilatancy and particle breakage of gravelly material from the Zipingpu concrete-faced rockfill dam, which was subjected to high-intensity seismic load during the 2008 Wenchuan earthquake, were conducted through a series of large-scale drained triaxial compression tests. A hyperbolic relation between the input plastic work and the degree of particle breakage was found for Zipingpu gravel, independent of the initial void ratio and confining pressures. The stress-dilatancy for Zipingpu gravel was analyzed and compared with data from two rounded alluvial and three angular quarried gravelly and rockfill materials in the literature. A nearly linear relationship between the dilatancy D p and the stress ratio η was found at medium-to-large stress ratios before the peak stress ratio. The slope of the stress-dilatancy line before peak had slight dependence on the void ratio and confining pressure of the gravel. After peak, the stress-dilatancy relation shifts down compared with that before peak for the gravel specimen. The phase-transformation stress ratio decreased with increased confining pressure, with the exception of sub-rounded gravel with little particle breakage. A nearly linear relationship was found between the phase-transformation stress ratio M f and the state parameter ψ for the Zipingpu gravel, regardless of the void ratio and confining pressure of the specimens.

Geotechnical aspects and seismic damage of the 156-m-high Zipingpu concrete-faced rockfill dam following the Ms 8.0 Wenchuan earthquake

Damage to the Zipingpu concrete-faced rockfill dam (CFRD) with the maximum height of 156m was induced by the great May 12, 2008 Wenchuan earthquake with a magnitude of Ms 8.0. The dam is the first CFRD over 150m high experiencing the strong shallow earthquake of IX degree in the world. The seismic damage to the dam raised a number of questions concerning the safety of the dam as well as the adequacy of design criteria. Extensive investigation has been carried out accordingly and is summarized in this paper. The purpose of this paper is to document geotechnical aspects of the design and seismic damage during earthquake, and in particular to highlight key experiences and lessons learned. Analysis of the instrumental records during the earthquake and results of the subsequent surveys following the quake yield three key conclusions as follows. (1) The earthquake motion mainly caused significant seismic non-uniform deformation of the embankment and damage to the face slabs, structures on the crest and downstream stone masonry. The predominantly longitudinal seismic motion intensified the interaction between the embankment and the abutments. The seismic deformation of the embankment and the strong interaction between the abutments and embankment were believed to have been responsible for damage to face slabs. Seepage through the dam increased, but was not significant, due to water-seal damage in the concrete face and peripheral joints. In general, the damage to the dam, although serious in some parts, was minor as a whole and was reparable. (2) Several design considerations contributed to the safety of the Zipingpu dam. Shallow-angle slopes on the downstream dam face were used to enhance the stability of the dam. Most significantly, the adequate zoning and well-compacted rockfill enabled effective deformation control of the embankment, thus greatly reducing the seismic deformation during ground shaking and ensuring the safety of the seepage control system. The performance of the Zipingpu dam during the earthquake evidenced the success of the design. (3) Overall, the Zipingpu CFRD was structurally stable and safe even though it was subjected to seismic shaking at a greater magnitude than the design seismicity. High CFRDs are feasible in seismic regions of western China if adequate design considerations are implemented to alleviate as much damage as possible during major earthquakes.

Numerical simulation on slabs dislocation of Zipingpu concrete faced rockfill dam during the Wenchuan earthquake based on a generalized plasticity model.

After the Wenchuan earthquake in 2008, the Zipingpu concrete faced rockfill dam (CFRD) was found slabs dislocation between different stages slabs and the maximum value reached 17 cm. This is a new damage pattern and did not occur in previous seismic damage investigation. Slabs dislocation will affect the seepage control system of the CFRD gravely and even the safety of the dam. Therefore, investigations of the slabs dislocation's mechanism and development might be meaningful to the engineering design of the CFRD. In this study, based on the previous studies by the authors, the slabs dislocation phenomenon of the Zipingpu CFRD was investigated. The procedure and constitutive model of materials used for finite element analysis are consistent. The water elevation, the angel, and the strength of the construction joints were among major variables of investigation. The results indicated that the finite element procedure based on a modified generalized plasticity model and a perfect elastoplastic interface model can be used to evaluate the dislocation damage of face slabs of concrete faced rockfill dam during earthquake. The effects of the water elevation, the angel, and the strength of the construction joints are issues of major design concern under seismic loading.

Seismic Analysis of the Zipingpu Concrete-Faced Rockfill Dam Response to the 2008 Wenchuan, China, Earthquake

AbstractThis paper presents the findings from both the detailed site investigations and the computational analyses on the Zipingpu concrete-faced rockfill dam (CFRD), a 156-m high dam in which 100-cm permanent settlement and 60-cm horizontal displacement occurred during the 2008 Wenchuan, China, earthquake. The Zipingpu CFRD was 17 km away from the epicenter and was considerably damaged by the Wenchuan earthquake. It was estimated that the peak acceleration in the top of the dam along the axial and vertical direction was about 20.0 m/s2, and the peak acceleration at the river level was about 16.0 m/s2. It was calculated that peak acceleration of dam bedrock was more than 5.0 m/s2, and the intensity (Chinese scale) was more than IX. Based on an in-situ investigation, the peak value of settlement of the dam crest reached 744.3 mm, and the peak value of horizontal displacement toward the right and left abutment are 226.1 mm and 106.8 mm, respectively. The actual experience of the peak acceleration and sei...

Analysis on residual strain of Zipingpu Concrete Faced Rockfill Dam after Wenchuan earthquake

The Zipingpu Concrete Faced Rockfill Dam (CFRD) was subjected to significant local damage in the “5.12” Wenchuan earthquake. It is the first rockfill dam of more than one hundred meters high to encounter a strong earthquake anywhere in the world. Based on the finite element smoothing method, the residual strains at a typical cross-section and a downstream slope of the dam were obtained by processing the dam monitored displacement data. The position of and reason for the dam settlement and deformation of rockfill dilatancy in the earthquake were analyzed according to the section residual strain. The results show that the maximum settlement ratio on the dam body approximately occurs at 2/3 of the dam height; dilatancy occurs from the dam crest to 25–30 m in the upstream and downstream slope; the immediate cause of the face slabs horizontal construction joint dislocation is excessive residual shear strain. Meanwhile, the position of and reason for the dam fissure in the earthquake were analyzed according to the dam slope residual strain.

Numerical simulation of the seismic response of the Zipingpu concrete face rockfill dam during the Wenchuan earthquake based on a generalized plasticity model

The strong ground motion of the 2008 Wenchuan earthquake in China caused considerable damage to the Zipingpu concrete face rockfill dam (CFRD). The maximum crest settlement was approximately 1.0m, and compressive failure and joint dislocations were observed in the face slabs. This damage has made it necessary to understand the damage pattern and safety of high CFRDs subjected to strong earthquake shaking, and the response of the Zipingpu CFRD during the Wenchuan earthquake can be used as a benchmark for this purpose. In this study, a 3D dynamic procedure was employed to simulate the dynamic responses of the Zipingpu CFRD. The rockfill materials were described using a generalized plasticity model, while the interfaces between the face slabs and cushions were modeled using zero-thickness interface elements that follow a perfect elasto-plastic stress–strain model in the tangential direction using Coulomb’s friction law. Dam deformation, face-slab stress, and face joint dislocations were simulated, and the results were compared with the field measurements. Using the generalized plastic model, the residual deformation of the dam during the earthquake could be directly obtained without being complemented by separate, semi-empirical procedures. The rockfill materials shrank to the center of the valley due to the strong shaking, causing crushing damage in the zone of the slabs. The dislocation of construction joints was also duplicated by the numerical procedure. The results of this study indicate that a 3D finite element procedure based on a generalized plasticity model can be used to evaluate the dynamic responses of CFRDs during strong earthquakes.

DISLOCATION OF FACE-SLABS OF ZIPINGPU CONCRETE FACE ROCKFILL DAM DURING WENCHUAN EARTHQUAKE

Zipingpu concrete face rockfill dam (CFRD) is one of the tallest dams that have ever been subjected to strong earthquake shaking and recorded damages. In this paper, finite element method and limit equilibrium method are used to determine the most critical failure surface for Zipingpu CFRD during the 2008 Wenchuan earthquake in China. The dislocation damage of the face-slab joint was then obtained from the sliding block analysis. The major factors affecting dislocation displacement of face-slabs were analyzed. The results showed that the rigid sliding block method is relevant for analyzing the damage of face-slabs of CFRD during earthquake. The peak ground acceleration had a significant influence on the dislocation. As the acceleration of the dam increases with the height while the strength of face-slab joints reduces, the dislocation could easily occur when the upstream slope of the dam started to slide. The water elevation had considerable impact on the dislocation of face-slabs during strong shaking. There might be no dislocation of face-slabs at full reservoir, and the water elevation just above construction joints would induce larger damage.

Three-dimensional simulation of the construction process of the Zipingpu concrete face rockfill dam based on a generalized plasticity model

Concrete face rockfill dams (CFRDs) are becoming a widely used type of rockfill dam in China. In many cases, the design and construction of CFRDs are based primarily on precedent and engineering judgments. Few numerical or analytical methods have been developed to properly evaluate the deformation of CFRDs, which is important for dam safety and for subsequent evaluation of seismic performance. In this study, a finite element procedure was developed to simulate the construction process of a CFRD, using the Zipingpu CFRD in China as an illustrative example. The Zipingpu dam was subjected to a strong earthquake in 2008, and can be used as a benchmark problem to assess the safety of CFRD. It is thus important to the engineering community to establish the state of stress–strain in the dam prior to the earthquake. A generalized plasticity model was modified to better model the rockfill materials, and the interfaces between face slabs and cushions are modeled using zero-thickness interface elements that follow a hyperbolic stress–strain model in the tangential direction. The model parameters were calibrated by large-scale triaxial tests and direct shear tests performed on materials used in the dam. The step-by-step construction followed by subsequent impounding of the reservoir was simulated in the numerical procedure. The numerical results agree well with in situ monitoring records of dam settlements, indicating that a three-dimensional finite element procedure based on a modified generalized plasticity model and a hyperbolic interface model can be used to evaluate the deformation of CFRDs.

Features of seismic hazard in large dam projects and strong motion monitoring of large dams

Earthquakes can affect large dam projects in many different ways. Usually, design engineers are focussing on ground shaking and neglect the other aspects. The May 12, 2008 Wenchuan earthquake has damaged 1803 dams and reservoirs, and 403 hydropower plants with an installed capacity of 3.3GW. Among these dams were the 132-m-high Shapai RCC arch dam and the 156-m-high Zipingpu concrete face rockfill dam. These recently completed dams are dam types which, up to now, have not experienced strong ground shaking. The widespread mass movements have caused substantial damage to dams and surface powerhouses in Sichuan. The different features of earthquake hazard are presented, i.e., ground shaking, faulting and mass movements. It is proposed to prepare project-specific safety plans for all dams, which consist of a matrix where the possible hazards and the corresponding countermeasures are listed. The earthquake behaviors of the Sefid Rud, Zipingpu and Shapai dams, which, in the past, have experienced strong ground shaking from nearby earthquakes, are discussed. Finally, the need for strong motion instrumentation of large dams is discussed. It is proposed that major dams with large damage potential, dams located in areas of high seismicity, and dams showing signs of abnormal behavior be equipped with strong motion instruments.

Impact of the ‘5.12’ Wenchuan earthquake on Zipingpu concrete face rock-fill dam and its analysis

The ‘5.12’ Wenchuan Earthquake hit Zipingpu concrete rock-fill dam hard and rendered a maximum permanent settlement of 100 cm and a horizontal displacement of 60 cm to the dam. Such a large permanent deformation due to earthquake has brought about a large area of separation between the concrete face and the cushion layer plane, resulting in an obvious dislocation of the construction joints of the concrete face above the reservoir water level and a crushed damage of the vertical joints of the concrete face. The damage mechanism has been analysed according to the field investigation. Proposals are also put forward for the future analytical computation of the earthquake impact on the concrete face rock-fill dam, anti-seism design and the principle of rehabilitation of the Zipingpu concrete rock-fill dam after the quake as well.