Seismic Response Of Dam Research Articles

Seismic analysis of gravity dam-foundation systems using stochastic spectral finite element method

Seismic analysis of dam-foundation systems is inherently complex due to uncertainties in material properties. This study investigates the effects of material randomness and heterogeneity on the seismic response of gravity dam-foundation systems using the stochastic spectral finite element method (SSFEM) based on the Karhunen Loève expansion and the polynomial chaos expansion. The Pine Plane dam is taken as an analysis example. First, the appropriate Karhunen Loève expansion modes and polynomial chaos order are determined for SSFEM by comparing them with the Monte-Carlo simulations. Subsequently, the seismic response of the dam is analyzed in the stochastic and deterministic models, respectively. Results indicate that material randomness and heterogeneity may reduce the seismic response of gravity dams, and the deterministic model may overestimate dynamic responses. Subsequently, the parametric analysis of the correlation length, which measures the spatial correlation between variables in different positions and indicates the size of heterogeneity material patches, is conducted. It is demonstrated that the correlation length would not significantly affect the mean responses, but a larger correlation length leads to greater dispersions in responses. Finally, the effects of randomness in the foundation are investigated. The heterogeneities in the foundation affect the response of the dam in the high-frequency range. Therefore, the uncertainty in material properties should be fully considered in a structural assessment and risk analysis.

Study on seismic wave propagation regularity and dam-foundation interaction characteristics of earth-rock dam on deep overburden

Many dams have to be constructed on deep overburden in meizoseismal areas, so it is vital to understand the seismic performance of these dams. Current research primarily focuses on the whole seismic response of dams, in which the analysis can be relatively imprecise. Nevertheless, an in-depth understanding of the propagation regularity of seismic waves in earth-rock dams on deep overburden, as well as the interaction characteristics between the dam and overburden, is critical. In this paper, based on a planning soil core wall dam with over 500 m of overburden, the seismic wave input method is employed to conduct a detailed and in-depth study from the perspectives of the spatial distribution of seismic acceleration and the Fourier spectra of acceleration time history. The results indicate that the spatial distribution of the peak acceleration of the dam is significantly inconsistent. The horizontal peak acceleration of the upstream side of the dam is greater than that of the downstream side because the dynamic modulus of the dam is significantly inconsistently distributed. In addition, the amplification behaviours of the seismic wave are different in the overburden and dam body, and the low-frequency and high-frequency components are amplified. The dynamic interaction between the dam body and the overburden significantly reduces the acceleration response at the dam-foundation interface by 44 % and 50 % in horizontal and vertical accelerations, respectively, because of the absorption of seismic wave energy by the dam body and the inconsistency of the dynamic modulus distribution of the overburden. The findings of this study provide robust theoretical support for evaluating the seismic performance and designing measures for the seismic resistance of earth-rock dams on deep overburden.

Seismic Response of Earth-Rock Dams with Innovative Antiseepage Walls on the Effect of Microscopic Fluid-Solid Coupling

In dykes and dam projects, the microscopic fluid-solid coupling effect from the interaction between soil skeleton and pore water during an earthquake is crucial to consider, as it can lead to dam safety problems. To control seepage in medium- and small-sized dams, polymer antiseepage walls have emerged as effective measures. In recent years, this method has been increasingly utilized in projects worldwide as it is essential for preventing potential dam safety issues. To address concerns related to seismic safety, this study conducts theoretical analysis, model tests, and numerical simulations to investigate the seismic response of earth-rock dams with polymer antiseepage walls, with a specific focus on the microscopic fluid-solid coupling effect. The dynamic viscoelastic constitutive model used in this study incorporates Biot’s theory of dynamic consolidation and the results of dynamic mechanical analysis (DMA) of polymer materials. To validate the model, a centrifuge test is performed, and it is then utilized to study the seismic response of earth-rock dams with polymer antiseepage walls. Furthermore, the influence of factors such as fluid-solid coupling, water level, polymer material density, and wall thickness on the seismic response of dams with antiseepage walls is analyzed. Finally, the seismic safety of the earth-rock dam with the polymer antiseepage wall is thoroughly examined. The results emphasize the need to consider the fluid-solid coupling effect, as factors like water level and design parameters of the antiseepage wall significantly impact the seismic response of earth-rock dams with polymer antiseepage walls.

The effect of vertical motions on damage accumulation on concrete gravity dams

AbstractThe effect of vertical ground motions on the seismic response of dams has long been a concern in the seismic design and evaluation of concrete gravity dams. The guidelines regarding the use of vertical motions in time history analysis (THA) are not clear due to the complexity of the effect as well as the large uncertainty in the motion selection process. The goal of this study is to assess the significance of vertical motions’ effects on concrete gravity dams considering the relevant variability due to ground motion, system frequency response as well as the shaking level. To this end, a carefully selected ground motion set providing realistic vertical(V)/horizontal(H) loading was used in nonlinear THAs of three different systems with different modal properties. In order to evaluate the intensity of shaking on the vertical motions’ effect, the responses were calculated at different seismic levels corresponding to operation, design, and maximum shaking levels. Along with traditional demand parameters commonly employed in assessing seismic response, cracking on the base and at the upstream face of the monolith was adopted as demand measures using a model capable of yielding discrete cracking on the system. The effect of vertical motions was quantified by comparing the response of H + V to H only shaking. The results show the vertical shaking can significantly affect upstream cracking for the operation or design level earthquakes, the effect increasing for larger dams.

Fluid-Structure Interaction: Impact of Reservoir Simulation Approach Considering Far-Field Boundary Condition in Dam Seismic Response

Fluid-Structure Interaction: Impact of Reservoir Simulation Approach Considering Far-Field Boundary Condition in Dam Seismic Response

On the seismic performance evaluation of dam-foundation-reservoir system for the effect of frequency content and foundation flexibility

The present paper investigates the effect of earthquake frequency content and foundation flexibility on the performance of the Koyna dam-foundation-reservoir system. Ground motions that match the conditional mean spectrum (CMS) are adopted for the seismic analysis. The concrete damaged plasticity model is used to represent the dam's nonlinear behavior; however, the foundation is assumed to be linear elastic. To study the foundation flexibility effect on the seismic performance of the dam, three different cases which comprise different elastic modulus of the foundation are considered. The damage indices, based on the crack length and dissipation energy, are evaluated for the performance assessment of the dam-foundation-reservoir system. The ground motion parameters such as predominant period, mean period, and effective ground period are chosen in order to explore the earthquake frequency content effect on the performance of dam-foundation-reservoir system. Results indicate that foundation flexibility has a significant effect on the dam. Further, the frequency content has a substantial impact on the dam's seismic response compared to the intensity and duration of ground motion. It can be concluded that the mean period is a good indicator of the earthquake frequency content and has a strong correlation with the damage parameters.

Prediction of permanent settlements of an upstream faced earth dam

In upstream faced earth dams all possible seismic-induced damages may be expressed using crest settlement as indicator, which may be predicted using complete dynamic analyses, or more traditional/simplified approaches such as sliding-block based methods and predictive formulas. The present paper compares results yielded by different analysis procedures applied to investigate the seismic response of an existing Italian earth dam. It shows how the use of both complete dynamic analyses and traditional simplified approaches, rather than resulting alternative each other, can be synergic in supporting the interpretation of the dam seismic response, somehow allowing a mutual check of result reliability. The paper also deal with a critical aspect in carrying out complete dynamic analyses of dam behavior, which is the calibration of model parameters. It shows how a back-analysis-based calibration procedure processing static observations may conveniently be implemented to set part of the high number of parameters characterizing complete dynamic approaches.

Influences on the Seismic Response of a Gravity Dam with Different Foundation and Reservoir Modeling Assumptions

The seismic design and dynamic analysis of high concrete gravity dams is a challenge due to the dams’ high levels of designed seismic intensity, dam height, and water pressure. In this study, the rigid, massless, and viscoelastic artificial boundary foundation models were established to consider the effect of dam–foundation dynamic interaction on the dynamic responses of the dam. Three reservoir water simulation methods, namely, the Westergaard added mass method, and incompressible and compressible potential fluid methods, were used to account for the effect of hydrodynamic pressure on the dynamic characteristics and seismic responses of the dam. The ranges of the truncation boundary of the foundation and reservoir in numerical analysis were further investigated. The research results showed that the viscoelastic artificial boundary foundation was more efficient than the massless foundation in the simulation of the radiation damping effect of the far-field foundation. It was found that a foundation size of 3 times the dam height was the most reasonable range of the truncation boundary of the foundation. The dynamic interaction of the reservoir foundation had a significant influence on the dam stress.

The effect of non-uniformity in ground motions on the seismic response of arch dams

Recorded ground accelerations at various locations of Karun III Dam during November 20, 2007, were recorded by an array of accelerometers located on the dam. In terms of amplitude and phase, these accelerations show non-uniformities in different elevations. In this paper, the effect of these non-uniform ground motions on the seismic response of the dam taking dam-reservoir-foundation interaction into account is investigated. The EACD-3D-2008 finite element program and ABAQUS Software are used for carrying out the seismic analyses. For this purpose, time histories of the earthquake accelerations are interpolated at nodal points located on the dam foundation interface. The analysis has been repeated, considering the common assumption of uniform ground motions. Comparing the results obtained from these two analyses reveals that the computed displacements in the crest due to the spatially varying excitations are in more conformity with the recorded information. Moreover, neglecting the non-uniform nature of ground motions in the model leads to underestimating the tensile stress values within the dam body.

Safety Evaluation of High Concrete-Faced Rockfill Dam Based on Site-Related Response Spectrum Using Scenario Earthquake

To clarify how to arrive at earthquake ground motion parameters for use in evaluating the high rockfill dams during seismic loading conditions, as well as to evaluate reasonably the seismic response of dams subjected to strong earthquake, the differences of design response spectra determined by scenario earthquake and uniform hazard spectra theory are investigated in detail. Coupled with the safety evaluation of the Houziyan concrete-faced rockfill dam (CFRD) with a height of 200 m located in meizoseismal regions, comprehensive comparisons of key safety evaluation indices are performed using input motions determined from the abovementioned two design response spectra. The key safety evaluation indices include dynamic response acceleration, permanent deformation, safety of the impervious body, safety factor, and sliding displacement of the potential failure sliding body. Additionally, the ultimate seismic capability of the high CFRD is discussed based on the two response spectra. More considerable results can be achieved and offered to the engineers for the seismic design. It is obvious that the uniform hazard spectra, which are used to adopt in the safety evaluation of high CFRD, typically result in conservative evaluations and unnecessary economic cost for seismic design and reinforcements.

Parametric Investigation of Canyon Shape Effects on the Seismic Response of 3D Concrete Gravity Dam Model

In this study, the three-dimensional seismic response of Pine Flat concrete gravity dam is investigated. For this purpose, two- and three-dimensional nonlinear analyses are carried out based on the finite element method. The effects of canyon shape variation on the seismic response of the dam are evaluated, and different components of a seismic record are considered to assess the dominance of each earthquake component on the structural behavior. Two sources of nonlinearity are taken into account including material and geometric nonlinearities. As geometric nonlinearity, vertical contraction joints are considered within the dam body, and the results are compared with integrated models. It is concluded that stream component of earthquake record plays an important role on the crest displacement. Assuming two- and three-dimensional dam-reservoir-foundation coupled system may lead to partly different results. It is finally observed that, although utilizing contraction joints increases the amount of compressive stresses in the allowable range, but the tensile damages imposed to the dam body may encounter a significant decrease.

Seismic analysis of damaged concrete gravity dams subjected to mainshock-aftershock sequences

The current study aims at seismic analysis of damaged concrete gravity dams subjected to aftershocks loading of earthquake. Dams’ sliding behaviour is also discussed to shed light on the issue. For the purpose of the study, a cracked concrete gravity dam was modelled, and zero thickness contact elements were used to model the contact between the main body and the separated damaged parts of the dam. The augmented Lagrangian method, considering frictional sliding and opening of contact joints, was used in non-linear analyses. Fluid-structure-interaction, considering fluid compressibility and absorptive boundary of reservoir, was also taken into account. The damage model of ‘Konya’ and ‘Manjil’ dams comprised our case study. Non-linear dynamic analyses were done based on both models. Stiffness and damping coefficients effect on the seismic response of dam were examined. Dam, foundation and reservoir interaction effects were also included. The results were compared to the results obtained from other methods, which showed adequate similarities. The differences between damages caused by aftershocks are discussed, and it is pinpointed that the stability of dam during aftershocks is not compromised. It is demonstrated that top block slides during each aftershock and finally incurs some permanent sliding which may destroy the dam.

Effects of rotational components of earthquake on seismic response of arch concrete dams

The present study deals with dynamic analysis of arch concrete dams, taking rotational components of earthquakes into account. A modified methodology was used to evaluate the rotational components of the earthquake. The translational components of the earthquake have been used in to obtain the rotational components of the earthquake, based on the intersecting isotropic elastic wave propagation. Two rotational components of Taft, Tabas and San-Fernando earthquakes are evaluated based on the translational components of the earthquakes and considering frequency dependencies of incident angle and wave velocity. Finally, dynamic analyses of Morrow Point Dam are presented to evaluate the effects of combined translational and rotational components on the seismic response of the dam. Various conditions of reservoirs, including full and empty state, are considered in the analyses. Fluid-structure interaction was completely taken into account. It was realized that incorporating rotational components increased the maximum compressive and tensile stresses in both empty and full reservoir analyses. Distribution of maximum tensile stresses is very sensitive to the rotational components of the earthquake. Also, it can be concluded that the segregated effect of the rocking component on the response of concrete dams is more effective than the sole effect of the torsional component.

Influence on Seismic Response of Dam by Different Dynamic Boundaries

The dam will interact with the foundation during earthquakes. The numerical seismic response of dam by FEM will be significantly influenced by the reasonable computational domain and dynamic boundary. Viscous-spring boundary, viscous boundary, fixed boundary, fixed boundary with massless foundation were compared one another on the dam's seismic response. Due to the radiation damping of foundation reflected by viscous-spring boundary, the peak value of dynamic response can be reduced 50% approximately at most compared with the traditional fixed boundary of massless foundation.

Influence of Sediments Characteristics on Seismic Response of Concrete Dams

To solve the problem of sediments on seismic response of concrete dams, pressure wave formula of saturated porous fluid-solid two-phase medium was derived from the Biots consolidation theory, and was determined the seismic response magnitude of sediment on concrete dam. Sediment was regarded as elastic-plasticity. And the method was applied to analyze the influence of sediments density, cohesion and friction angle on dam seismic response. Finally, a typical example is analyzed. The result shows sediments plasticity is relatively obvious on dam seismic response.

Seismic Response of Dam-Sediment-Water on Fluid-Solid Coupling

Studying the important effects of sediments on the seismic response of dams ,This paper established the calculation model based on regarding the water reservoir as compressible fluid ,the dam and the foundation as an elastic solid, the sediment as Liquid-Solid two-phase porous medium. The results showed that the sediment thickness and properties have important effects on the dam seismic. Increasing the thickness of sediment ,the seismic response of acceleration significantly decreased, the hydrodynamic pressure significantly reduced , which is benefited to the safety of the dam.

3-D Seismic Response Analysis Methods of High Core Rockfill Dams

Based on dynamic triaxial test data of dam materials, a dynamic constitutive model is suggested. Combining with construction of a high core rock-fill dam, several key issues, such as dam seismic response, seismic slope stability, dam permanent deformation, filter layer anti-liquefaction, and dynamic strength of the core wall are analyzed using 3-D dynamic effective stress analysis method. Some useful conclusions and regularity are obtained in aspects of seismic response and anti-seismic properties. The analysis method and conclusions could be referred to the analogous engineering.

Study of Elastic-Plastic Sediments on Seismic Response of Concrete Dams

To solve the problem of sediments on seismic response of concrete dams, pressure wave formula of saturated porous fluid-solid two-phase medium was derived from the Biot’s consolidation theory, and was determined the seismic response magnitude of sediment on concrete dam. Sediment was regarded as elastic-plasticity. And the method was applied to analyze the influence of sediments density, cohesion and friction angle on dam seismic response. Finally, a typical example is analyzed. The result shows sediments are significant on dam seismic response.

Research on Influence of Sediments Mechanical Parameters of Seismic Arch Dams

The problem of sediments on seismic response of arch dams was not solved. Thus pressure wave formula of saturated porous fluid-solid two-phase medium was applied from the Bait’s consolidation theory, and was determined the seismic response magnitude of sediment on arch dam. And the method was applied to analyze the influence of sediments thickness, cohesion and friction angle on dam seismic response. The result shows sediments is relatively obvious on arch dam seismic response.

Back Analysis of Dam Parameter under Seismic Action

Reasonable parameters are the premise of correct analysis of dam. The method of mechanical parameter determination is studied based on seismic response of dam using back-analysis theory. Firstly, a displacement statistical model under seismic load response is built, and a modified objective function is deduced. Then, finite element model of a built dam and genetic algorithm based calculation program are developed. Finally, the mechanical parameters of the system are inversed, optimized and verified. The results show that the inversed parameters are reasonably accurate, and the inversion method based on seismic response of dam is reasonable and feasible, which may provide significant reference for analyzing the behavior of dam.