Response Of Dams Research Articles

Dynamic response of Zelazny Most tailings dam to mining induced extreme seismic event occurred in 2016

The paper deals with the stability analysis of tailings dam subjected to dynamic loading induced by mining shocks which occurred in neighbouring copper mine. The main goal of the paper was to model the dynamic response of the dam during two extreme paraseismic events which occurred in 2016 based on accelerograms recorded at the dam toe. Dynamic response of the tailings dam was calculated using finite element method and the implicit time-integration method implemented in commercial codes. The boundary condition corresponding to dynamic loading was determined by deconvolution procedure. The error analysis showed that most precise signal reproduction is achieved while using target signal with peak value reduced by 40% as a test signal. Both acceleration and displacement time-series were successfully reproduced. Moreover, the stability analysis was conducted for five independent signals with design peak horizontal acceleration and showed that no permanent displacements should occur. The temporary horizontal displacement of the dam crest should not exceed 13 mm, assuming equivalent linear material model.

Influence of Joint Orientation on the Behavior of Dam Foundation Resting on Jointed Rock Mass Under Earthquake Loading Condition

In this article, the effect of an intact rock foundation and foundations with different single rock joint inclinations (0°, 30°, 60°, 90°) on the dynamic response of the concrete gravity dam under strong earthquake ground motion is investigated. Discrete element analyses are carried out using UDEC to study the stress-deformation behavior of dam for two specific dynamic load combinations (LC), i.e. considering the dead weight of the dam having an empty reservoir with earthquake loading (LC-D) and considering the dead weight of the dam along with hydro-dynamic force with earthquake load (LC-E) as per IS: 6512. From the results, the compressive stresses are found maximum at the heel of the dam for LC-D and maximum at the toe for LC-E. The dam foundation with 60° joint inclination was found most critical in terms of possessing maximum compressive stresses among all other cases. Dam foundation with a horizontal (0°) set of joints exhibits maximum crest displacement and base sliding. Foundations with 60° and 90° joint sets are found to undergo lower base sliding compared to other joint sets.

Geotechnical risk analyses and evaluation of design criteria of embankment dam systems

The integrity of the state and national system of embankment dams and levees is a crucial component in ensuring the safety of protected communities in any country. The failure of such systems due to natural or man-made hazards can have monumental repercussions, sometimes with dramatic and unanticipated consequences on human life, property and the economy of the states and the country. For highly seismic areas such as Southern California, it is critical to investigate and study the seismic response of embankment dams and levees for the afore mentioned reasons. While experimental studies of embankment dams under seismic loads is expensive, very time consuming, and limited, numerical studies usually suffer from lack of legitimate real data for verification of the developed models. However, organizations such as the California Strong Motion Instrumentation Program (CSMIP) instrument lifeline structures such as earth dams and levees with accelerometers and actively collect strong-motion data. The data obtained from CSMIP accelerometers is then processed by the Center for Engineering Strong Motion Data (CESMD) and made public for earthquake engineering applications. In this study, numerical models of existing earth embankment dams verified with site specific CESMD data are created in order to analyze their stability for a future earthquake, for post-earthquake response purposes. The seismic fragility of the modelled dams was assessed, providing insight for decision makers regarding priority areas important for matters such as maintenance, dam retrofit, or first-aid response locations for a hypothetical major earthquake. Society can benefit from increased awareness of the seismic response of the modelled structures and can be better prepared for a potential catastrophic seismic event.

A deformation separation method for gravity dam body and foundation based on the observed displacements

The displacement at arbitrary point in the dam is composed of two parts: One is the elastic deformation of dam body and the other that is due to the constrained deformation of foundation. The two parts should be separated to obtain reliable information reflecting the different characteristics of dam body and foundation. A simplified simulation method for gravity dam foundations is proposed that reflects the constrained deformation of foundation in a rational manner while taking into account the complex and diverse mechanical properties. Only the effects of the foundation on dam is investigated in the proposed model, and they are considered either centralized constraints or distributed constraints. The solution of the global foundation deformation is based on the monitoring displacements at measuring points in the gravity dam section using the hybrid partition finite element–interface boundary element approach. The reaction of the foundation on dam can be reflected by the global foundation deformation and the constrained force at dam bottom. On the basis, the whole dam response under a given load combination can be estimated using finite element theory. Three analyses have been performed on a typical gravity dam section to verify the feasibility of simplified simulations for different foundations as well as to allow for discussions regarding the differences among the simulations. An example analysis based on the proposed method is performed on a prototype gravity dam, and the results, which compared with actual measurements for discussions, show that the proposed method is reasonable and practical.

Structural health monitoring of concrete dams using long-term air temperature for thermal effect simulation

Dam health monitoring is usually achieved by using the hydrostatic-season-time model that simulates the temperature effect through harmonic sinusoidal functions. The model is convenient, but does not take into account the effect of temperature variations in different years on dam response. This paper presents a dam health monitoring model using long-term air temperature for thermal effect simulation. In the model, harmonic sinusoidal functions are replaced by long-term air temperature to simulate the temperature effect on the dam response. The machine learning technique RBFNis adopted to mine the temperature effect from long-term air temperature series. The proposed dam health monitoring model was verified using monitoring data of a real concrete gravity dam. Results show that the nonlinear RBFN model utilizing long-term air temperature achieves better results than the model using harmonic sinusoidal functions.

Seismic response of Heitiejiao tailings dam by the finite element method

In this study, seismic response of a tailings dam is investigated by finite element method. The Heitiejiao dam constructed in She county, China is chosen as a numerical example. The interaction of the tailings dam with the reservoir is neglected, but not the foundation rock. The properties of the dam materials were taken from the dam project and assumed to be linearly elastic, homogenous and isotropic in the analysis. A stationary and ergodicity assumption is made for seismic analysis. The E–W component of the Tianjin Earthquake is chosen as a ground motion since it occurred nearby the dam site. The component considered is applied to the dam in the horizontal direction. The seismic response of the Heitiejiao dam subjected to the Tianjin Earthquake is also obtained by the deterministic method. The results obtained from stochastic and deterministic analysis are compared to each other. It is seen that the results obtained from the time-history analysis are smaller than those from the deterministic analysis.

Design, Manufacturing and Testing of Small Shaking Table

The seismic performance and the dynamic response of concrete gravity dams can be verified by several techniques. Both geotechnical centrifuge apparatus (under N-g values) and shaking table (under 1-g) are the commonly used techniques in the world. This paper deals with designing, manufacturing, and testing of small shaking table to investigate different geotechnical and engineering problems. The main body of the designed shaking table consists of steel frame (local iron) manufactured as a hollow box with steel plate, 6mm in thickness and one-direction movable platform (as a basket carrying the container of the model). Inside this main box, all the mechanical parts that work as one system to generate the motion of the seismic wave with an acceleration that needed to the test. The facilities of this shaking table, the movable base has a dimension of 0.8m x1.2m and the platform mass approximately 2 kN, the maximum allowable model weight of 10kN, the range of frequency from 0 to 20 Hz, the maximum acceleration amplitude of 1.2g and maximum displacement of 14mm. It can simulate only the single frequency motion (i.e. sinusoidal wave). The measured accelerations at different soil model level for the tested shaker under 0.6g sinusoidal waveform gave a reasonable prediction for the dynamic response and the amplification characteristics.

Seismic Analysis of Concrete Gravity Dams Considering Foundation Mass Effect

Incorporating the dam-reservoir-foundation interaction effects into the seismic analysis of a dam can lead to a more accurate evaluation of its behavior. This study proposes a method for modeling the dam-reservoir-foundation system by considering mass of the foundation. In order to validate the proposed numerical modeling approach, its results are compared with those of previous studies. The Koyna concrete gravity dam is used as the case study and to consider the nonlinear material behavior, the Concrete Damage Plasticity (CDP) model is applied. Four models are established and their results are compared and discussed through displacement, principal stresses, crack propagation, damage dissipation energy curves and damage indices. The results show that considering massed foundation trigger a profound impact on the seismic response of the gravity dams. The results of this study could be used as an approach for conducting nonlinear seismic evaluation of concrete gravity dams by considering mass of the foundation.

Seismic analysis of reservoir-gravity dam-massed layered foundation system due to vertically propagating earthquake

Seismic analysis of complex structures such as concrete dams has been the subject of numerous studies. One of the challenges in seismic analysis of such systems is proper modelling of massed foundation. Since concrete dams’ foundations are usually layered, this makes the homogenous half-space assumption relatively unrealistic. In this paper, the effects of massed layered foundation on seismic response of concrete gravity dams in dam-reservoir-foundation systems are investigated. Seismic finite element analysis of the system carried out using domain reduction method. This approach is compared with another available method named, free-field column. First set of analysis considers the effect of modular ratio between layers on seismic response of the gravity dam. Second set of analyses investigate the effects of layers’ geometry, location and orientation on obtained responses. Results highlight the considerable effects of massed layer foundation assumption against its homogenous counterpart. Besides, results show that layer properties dictate how severely they can affect the dynamic responses of the dam.

Site amplification effects of a radially multi-layered semi-cylindrical canyon on seismic response of an earth and rockfill dam

An analytical treatment of an earth and rockfill dam in a radially inhomogeneous multi-layered semi-cylindrical canyon in a half-space under obliquely incident plane SH waves is presented. In terms of a radial wave function expansion and a transfer matrix approach, a rigorous approach is formulated to consider inhomogeneity of the deformable canyon and associated phenomena of wave redirection, reflection, transmission, scattering and concentration. Upon confirmation of its accuracy with a past exact solution for the degenerated case of a dam in a homogeneous canyon, the multi-layer solution is extended to the case of a dam in a canyon covered by a surficial zone with a power-law shear-wave velocity model as a generalized class of smooth in-situ variations. A comprehensive set of numerical examples are presented to illustrate the sensitivity of the dam response to the inhomogeneity profile of the top canyon zone, the frequency content and the angle of the seismic wave incidence. As illustrated in both frequency and time domains, wave concentration is found to be the main reason for the high amplifications of the displacement within the dam.

Dynamic responses of concrete-faced rockfill dam due to different seismic motion input methods

The concrete-faced rockfill dam valley foundation was considered as an open energy system and a reasonable non-uniform seismic motion input method was applied to the dynamic analysis of a concrete-faced rockfill dam based on the generalized plastic model. First, the corresponding program was validated by means of the scattering question of an idealized semicircle valley. Subsequently, the seismic elasto-plastic finite element analyses were performed to compare and investigate the performances of a concrete-faced rockfill dam under different seismic motion input methods. The results show that the dynamic responses of the concrete-faced rockfill dam are decreased by 10%–30% approximately with the use of non-uniform seismic motion input method. As a result, the traditional uniform seismic motion input method would overestimate the responses of the dam. From the perspective of seismic safety evaluation, the overestimations would disturb the reasonable assessment of the aseismic capacity of the dam. Moreover, the slope stability analysis results might be conservative and unreasonable due to overestimating the accelerations during the earthquake.

Seismic performance evaluation of high CFRD slopes subjected to near-fault ground motions based on generalized probability density evolution method

This research mainly addresses evaluating the seismic reliability and analyzing the random dynamic response of high concrete-faced rockfill dam (CFRD) slopes suffering from the near-fault earthquakes by establishing a novel method of generating the representative acceleration time histories coupled with the recently proposed generalized probability density evolution method (GPDEM). A probability evaluation is performed after generating two groups of near-fault ground motions, pulse-like and non-pulse-like earthquakes, coupling a series of statistical stochastic parameters with the spectral representation-random function method. A 242-m-high CFRD is selected as an example for finite element stochastic dynamic time series analysis, and second-order statistical values (including mean and standard deviation) and probability information of three indices the safety factor, the cumulative time of safety factor ≤ 1.0 (Fs ≤ 1.0) and the maximum cumulative slippage of the dam slopes are determined, respectively. The effective non-stationary near-fault earthquakes will be adopted to determine the stochastic earthquake loading for the dynamic response evaluation of dam slopes. The statistical and probabilistic results demonstrate that the seismic characteristics make a great difference to the seismic response of slope stability as well as the pulse properties. The stochastic near-fault earthquakes combined with the GPDEM can evaluate seismic performance and reliability effectively from the perspective of randomness, and the failure probability can be obtained directly.

Calculation and Improvement of Complex Mechanical Properties of the Mega Arch Dam under Multiple Loads Based on Finite Element Methods

Researches on dynamic responses of the arch dam under seismic waves were not systematic and perfect enough in published papers. They rarely proposed measures to improve the antiseismic performance of the arch dam under seismic waves. Based on the finite element method, this paper completed a systematic and perfect research on stress and damage of the arch dam under seismic waves and proposed an effective measure to improve the antiseismic performance. The computed results of the improved arch dam were compared with the original one. Results proved that improved effects are obvious. In addition, damage stabilization value of the improved arch dam was 0.47, while the original one was 0.13. Obviously, the safety of the improved arch dam under the same loads was higher. Damage of the improved arch dam was increased by stages. It took about 3 s from zero damage to the complete damage, while the time was about only 1.3 s for the original one. Obviously, the antidamage capability of the improved arch dam was better. The improved measure proposed in this paper is very effective. This paper provides one reference for studying and improving the antiseismic performance of the arch dam.

A Ritz Procedure for Transient Analysis of Dam–Reservoir Interaction

A simple and accurate variational formulation is proposed to study the transient dynamic responses of two-dimensional dam–reservoir system. The proposed methodology uses a simple weak formulation with Ritz procedure to reduce the governing partial differential equations of the fluid and structure to a set of ordinary differential equations. An analog procedure is then presented to exactly implement the natural boundary condition of the problem at fluid–structure interface. The Newmark time integration scheme is used to solve the resulting system of ordinary differential equations. To demonstrate the accuracy and efficiency of the proposed formulation, the problem is also solved using the finite element method (FEM). It is found that the proposed method can produce better accuracy than the FEM using less computational time. The technique presented in this investigation is general and can be used to solve various fluid–structure interaction problems.

Performance Evaluation of Gravity Dams Subjected to Near- and Far-Fault Ground Motion Using Euler Approaches

Ground motions in near source region of large crustal earthquakes are significantly affected by rupture directivity and tectonic fling. These effects are the strongest at longer periods, and they can have a significant impact on engineering structure. This paper focuses on the effects of long-period pulse of near-fault ground motions on the structural performance of concrete gravity dams. Three sets of near- and far-fault ground motion records, which have approximately the same peak ground acceleration, are selected from 1987 Superstitn Hills (B), 1989 Loma Prieta and 1994 Northridge earthquakes. As a case study, Sariyar concrete gravity dam located on the Sakarya River, which is 120 km to the northeast of Ankara, is selected to investigate the near-fault ground motion effects on dam responses. The finite element models of the dam are constituted considering dam-reservoir-foundation interaction using ANSYS software. The behavior of reservoir is taken into account by using Euler approach. To determine the structural response of the dam, the linear transient analyses are performed using above-mentioned ground motion records. In the analyses, element matrices are computed using the Gauss numerical integration technique. The Newmark method is used in the solution of the equation of motions. Rayleigh damping is considered. At the end of the analyses, dynamic characteristics, maximum displacements, maximum and minimum principal stresses and maximum and minimum principal strains are attained and compared with values obtained from analyses under far-fault ground motions recorded far away from the same sites at above-mentioned earthquakes with approximately same peak ground acceleration.

A three-dimensional elasto-plastic dynamic response procedure for concrete-faced rockfill dams

Equivalent linear dynamic analysis is the primary method of analysis for concrete-faced rockfill dams during earthquake. However, this method cannot be directly used to estimate permanent deformation during earthquake, which is important to evaluate the dynamic safety of concrete-faced rockfill dams. To bridge this gap, an elasto-plastic dynamic response procedure based on finite element method is presented to estimate the construction, impoundment, and dynamic characteristics of concrete-faced rockfill dams. This procedure involves a generalized plasticity model for rockfill materials and an ideal elasto-plastic model for interface between concrete face slab and rockfill material. The construction, impounding process, and seismic behavior of a 150-m-tall concrete-faced rockfill dam were simulated using seismic motion based on Chinese code for seismic design of hydraulic structures of hydropower project with the peak ground acceleration of 0.3 g as an excitation to validate the procedure. On the basis of the numerical simulation results of the step-by-step construction, reservoir impoundment and seismic response of a concrete-faced rockfill dam, dam settlement, joint deformation, stress, and deformation of slab were analyzed. The results indicate that the dam settlement and deformation of joint can be directly obtained by the procedure during earthquake. The construction, impoundment, and seismic analysis could be considered in one procedure.

Seismic Improvement of Gravity Dams Using Isolation Layer in Contact Area of Dam–Reservoir in Smeared Crack Approach

This study has been conducted to evaluate the effect of the isolation layer on the seismic improvement of concrete gravity dams considering dam–reservoir interaction. Koyna dam in India, due to both horizontal and vertical components of Koyna earthquake, is modeled as a case study to show the effect of the upstream isolation layer on the seismic response of concrete gravity dams, and also the interaction effect is considered in models. The water is taken as a compressible, inviscid fluid and the foundation as rigid. Gravity dams are considered as 2D structures due to long dimension in cross-stream direction and plane strain assumptions. ANSYS software was used for analysis so that the fixed smeared crack model is used to consider the nonlinear behavior of mass concrete. A flexible layer which is attached to the upstream face of the dam under different thickness and material properties is considered. The response of unisolated and isolated dams is compared under various conditions. Finally, the effect of unisolated and isolated layers in the reduction of the seismic response of the concrete is evaluated under various thicknesses comparatively. Considering obtained results revealed that the layer can have the reducing effect on responses and crack propagation process of dam model because of damping the induced hydrodynamic pressure due to the earthquake.

Reliability and variance-based sensitivity analysis of arch dams during construction and reservoir impoundment

The static performance of arch dams during construction and reservoir impoundment is assessed taking into account the effects of uncertainties presented in the model properties as well as the loading conditions. Dez arch dam is chosen as the case study; it is modeled along with its rock foundation using the finite element method considering the stage construction. Since previous studies concentrated on simplified models and approaches, comprehensive study of the arch dam model along with efficient and state-of-the-art uncertainty methods are incorporated in this investigation. The reliability method is performed to assess the safety level and the sensitivity analyses for identifying critical input factors and their interaction effects on the response of the dam. Global sensitivity analysis based on improved Latin hypercube sampling is employed in this study to indicate the influence of each random variable and their interaction on variance of the responses. Four levels of model advancement are considered for the dam-foundation system: 1) Monolithic dam without any joint founded on the homogeneous rock foundation, 2) monolithic dam founded on the inhomogeneous foundation including soft rock layers, 3) jointed dam including the peripheral and contraction joints founded on the homogeneous foundation, and 4) jointed dam founded on the inhomogeneous foundation. For each model, proper performance indices are defined through limit-state functions. In this manner, the effects of input parameters in each performance level of the dam are investigated. The outcome of this study is defining the importance of input factors in each stage and model based on the variance of the dam response. Moreover, the results of sampling are computed in order to assess the safety level of the dam in miscellaneous loading and modeling conditions.

Effects of close proximity underwater explosion on the nonlinear dynamic response of concrete gravity dams with orifices

Abstract In order to meet the demand for power, irrigation, flood control, drinking water, etc., many orifices are usually designed on the dam body. This paper is aimed to evaluate the close proximity underwater explosion effects on the nonlinear dynamic response of concrete gravity dams with orifices. The accuracy and reliability of the coupled model is calibrated against a previous experimental test. The effects of the existing orifice on the damage processes of concrete gravity dams to close proximity underwater explosion are investigated. Damage characteristics of gravity dams with the orifice under close-in, inlet and internal underwater explosions are compared. The influence of the reinforcement and the water inside the existing orifice on the nonlinear dynamic response of concrete gravity dams is also discussed. The results show that the dam with orifice suffers more serious damage subjected to close proximity underwater explosion than the dam without orifice. Closing the gate of the orifice will significantly reduce the damage level of the dam.

Detection capabilities of alpha particles and gamma rays using DAM–ADC scintillator

DAM–ADC scintillator is optically characterized for both alpha particles using 241Am source and gamma radiation using 1.25 MeV 60Co. The Radioluminescence (RL) response of DAM–ADC scintillator to alpha particle has been investigated. The DAM–ADC sample was attached to the surface of the 241Am source, and the photons generated from the sample were detected by the PMT. For alpha particles, the integrated PMT counts output of the local system exhibit linear correlation with the irradiation time. In addition to RL detection of alpha particles, the results of exposing DAM–ADC scintillator to gamma rays with high doses has been performed. Linear relationship between Raman spectral peak intensity and gamma dose is investigated. Induced modifications in terms of structural and optical characteristics of the irradiated DAM–ADC scintillators with gamma rays were investigated. In addition to these properties, pulse height spectra (PHS) under 137Cs γ-ray and 241Am (alpha particles and gamma-ray (60 keV) irradiation have been measured.