Response Of Dams Research Articles

Computation of amplification functions of earth dam‐flexible canyon systems by the hybrid FEM‐SBFEM technique

AbstractA dam's responses can be amplified by the geometry and flexibility of its surrounding canyon. To modeling a canyon as an elastic unbounded domain, the radiation damping condition should be satisfied, and in this regard, the Scaled Boundary Finite Element Method (SBFEM) is a powerful tool. In this article, a substructure method was used to combine the standard Finite Element Method (FEM) with the SBFEM, resulting in the hybrid FEM‐SBFEM technique. This hybrid technique treats an earth dam by using FEM and a corresponding elastic unbounded canyon by SBFEM. The proposed approach was verified by data available in the literature. The seismic response of an earth dam‐flexible canyon system was investigated by employing a 3D FEM‐SBFEM method. Several amplification functions corresponding to different canyon conditions were obtained by applying a uniform displacement for the canyon boundary, and a comprehensive study was performed to examine the effects of canyon geometry and flexibility on the steady‐state response of the dam, as these two effects influenced the amplification functions. While the flexibility of the canyon significantly affects the maximum amplification function value for a dam, this value does not change for earth dams in canyons with different shapes but the same length. In addition, the lateral response of earth dams in the time domain was computed in order to analyze the aforementioned effects under an actual earthquake. The proposed amplification functions were used to compare the recorded response spectra of the El Infiernillo dam under the two earthquakes in 1966 with the calculated amplification function, and a reasonable agreement was observed between them.

Estimation of seismic wave incident angle using vibration response data and stacking ensemble algorithm

The determination of the incident angle of an earthquake is one of the critical research issues in modeling the seismic input mechanism at a dam site and it is also for geological exploration. At present, the incident angle calculation methods mostly rely on accurate geological models, complex theoretical formulations, and complicated procedures. To this end, an incident angle estimation method using dam vibration response data and a machine learning algorithm is presented in this study. First, a three-dimensional finite element gravity dam-foundation system model is constructed. A wave input method based on the viscous-spring artificial boundary is used to simulate the multi-angle incidence of P and SV waves. The vibration responses of key dam points are obtained. Nine features that have geometric interpretation are constructed by the response data and the new data are substituted into a stacking ensemble algorithm for training. Finally, the angles of obliquely incident P and SV waves are estimated using the trained stacking ensemble estimation model. The results reveal correlation between dam responses and the incident angle with the average R2 values of the estimation model of 0.996 (P waves) and 0.996 (SV waves), and the average root mean square errors of 1.765° (P waves) and 0.546° (SV waves). It is thus confirmed that the estimation model integrated multiple features from several measurement points with high accuracy and stability. In addition, the proposed method can be extended to other types of large structures because of its universality.

Evaluation of Hydrodynamic Pressure Distribution in Reservoir of Concrete Gravity Dam under Vertical Vibration Using an Analytical Solution

Fluid-structure interaction causes a hydrodynamic force, which can be exerted to the dam and affects its response. The effect of vertical excitation of ground motion on dynamic behavior of concrete gravity dam is the most important because of the interaction between foundation and reservoir. So, the foundation-reservoir interaction should be taken into account in designing concrete dams. In most studies, the effects of the vertical component of vibration have been ignored. While in vertical vibration, due to the interaction of the reservoir and the foundation, a significant hydrodynamic pressure is produced in the tank, which increases the dam response. In this study, the hydrodynamic pressure wave propagation in the reservoir of a concrete gravity dam caused by interaction with the foundation under vertical vibration is investigated using an analytical method. To achieve an analytical solution, the reservoir is assumed to be rectangular, and a harmonic load is vertically applied on the system from the foundation. Considering the acoustic nature of the reservoir fluid under harmonic vibration, a new method using the separation of variables method has been used for solution of hydrodynamic wave equation. The results show a significant effect of the vertical component of earthquake on the amount of induced pressure distributed in the reservoir, which has been omitted in most previous studies. Obtained results of the proposed model can be extended to more complicated models in terms of different loading and geometrical conditions.

Seismic performance of Al-wand earth dam: numerical analysis

The seismic can be threatened the stability of the flexible body of the earth dam and can cause completely damaged or deformation on their embankment. Therefore, a geotechnical engineer needs to know the effect of earthquakes on earth structures. The change in the seismic zone that recently Iraq affected is the reason for this research, in general, in 2017, the whole of Iraq, and in particular the region, where the Al-Wand earth dam (the subject of the study) is located, was exposed to several earthquakes. This research project mainly aims to study the behavior of Al-Wand earth dam under seismic load in different conditions by simulating Al-Wand earth dam through numerical modeling and study the influence of water reservoir level, earthquake peak acceleration, and duration. This paper includes an analytical study of the effect of this earthquake on Al-wand earth dam, using the quake/w program, which is a sub-program of geo-studio, also the stability of the dam was studied under the influence of earthquakes of different intensity, and a review of the impact of different water levels on the stability of the body dam. Where the response of the Al-wand dam was analyzed to earthquakes at the normal and the maximum water level, and by using a quake that may have been exposed to Iraq in 2017 and used the time of 100 seconds and using an acceleration of 0.02g, 0.03g, 0.05g measured by units of ground acceleration to identify the behavior of displacements, effective stress and pore water pressure during the earthquake.

Physical Modeling on Dynamic Responses of Gravity Dams by Underwater Explosion in a Centrifuge

AbstractGravity dams are important infrastructures, and their failure can affect public security. In this work, physical modeling was conducted to determine the dynamic responses and types of damag...

Nonlinear seismic response of arch dams considering joint opening effects and boundary conditions of discontinuous foundation

Nonlinear seismic response of arch dams considering joint opening effects and boundary conditions of discontinuous foundation

Three-Dimensional Non-Linear Analysis based on the Temporal Evolution of an RCC Dam Including the Alluvium Effect

This article discusses the seismic response of roller-compacted concrete dams by interpreting their behaviour under the effect of static and dynamic loads applied to a real case study: the Boussiaba dam. A three-dimensional finite element numerical modelling was undertaken using the Midas GTS- NX 2017 calculation code. The geometric model was established in Autocad taking into account the actual geomorphology of the terrain and the existing dam and then exported to GTS-NX. The dynamic solicitation, i. e. the earthquake, was generated from two accelerograms 0.25 g and 0.35 g amplitude respectively recorded in the Mila region located less than 20 km from the dam site. The initial static load being constituted by the dead weight, the water thrust and the sludge thrust at the bottom of the dam. Several reference points were chosen on the dam body to study the different parameters adopted. The results obtained during the dynamic numerical analysis show that the overall behaviour of the dam during earthquakes was satisfactory, without endangering the structural integrity of the structure. Keywords: Dynamic; Finite elements; Midas GTSnx; RCC dam; Three-dimensional. DOI 10.35180/gse-2021-0047

Study on the dynamic interaction between an arch dam and its appurtenant structures

This paper aims to analyze the effect of appurtenant structures on the seismic response of arch dams. For this purpose, a fine-grade finite element model is developed for the Sanhekou dam in China as a case study, which includes the discharge structure, the intake tower, the elevator shaft, and the viewing platform. The results indicate that different appurtenant structures have different influences on the seismic response of the dam. The crest spillways and the low-level outlets perforated in the dam body, significantly affect the seismic response of the local region of the arch dam body, while the appurtenant structures extending from the dam body, such as the intake tower, the elevator shaft, and the sightseeing buildings, have little influence on the seismic response of the dam body. In addition, the local vibration amplitudes of the high cantilever water inlet and the high-rise elevator shaft are significant, and thus they may be damaged under seismic loads.

A System Identification-Based Damage-Detection Method for Gravity Dams

Dams are essential infrastructures as they provide a range of economic, environmental, and social benefits to the local populations. Damage in the body of these structures may lead to an irreparable disaster. This paper presents a cost-effective vibration-based framework to identify the dynamic properties and damage of the dams. To this end, four commonly occurred damage scenarios, including (1) damage in the neck of the dam, (2) damage in the toe of the structure, (3) simultaneous damage in the neck and the toe of the dam, and (4) damage in the lifting joints of the dam, are considered. The proposed method is based on processing the acceleration response of a gravity dam under ambient excitations. First, the random decrement technique (RDT) is applied to determine the free-vibration of the structure using the structural response. Then, a combined method based on Hilbert–Huang Transform (HHT) and Wavelet Transform (WT) is presented to obtain the dynamic properties of the structure. Next, the cubic-spline technique is used to make the mode shapes differentiable. Finally, Continuous Wavelet Transform (CWT) is applied to the residual values of mode shape curvatures between intact and damaged structures to estimate the damage location. In order to evaluate the efficiency of the proposed method in field condition, 10% noise is added to the structural response. Results show promising accuracy in estimating the location of damage even when the structure is subjected to simultaneous damage in different locations.

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.

Measuring dam induced alteration in water richness and eco-hydrological deficit in flood plain wetland

Along with wetland loss, the damming effect on hydrological modification in wetland is another less debated and challenging topic, which needs to have urgent attention. The present work intended to investigate the damming effect on the water richness and eco-hydrological condition of the floodplain wetland and its consequent ecological responses in Punarbhaba River Basin of India and Bangladesh. Satellite images derived hydro-period, water presence frequency (WPF), and water depth were generated for developing water richness model in pre (up to 1992) and post dam conditions (1993–2019). The range of variability (RVA) was modelled using time series satellite images based water index or normalized difference water index (NDWI). Based on RVA model, the hydrological failure rate was developed. Depth of water was used for preparing the flow duration curve (FDC) to estimate the eco-hydro-deficit and surplus condition in wetland at spatial scale for pre and post-dam periods. Satellite image based trophic state index models for pre and post dam conditions were constructed to investigate the ecological response of dam on floodplain wetlands. Results of water richness model showed that wetlands area under high wetland water richness zone decreased from 71.83% to 7.65% in the post-dam conditions. Results of hydrological failure rate showed that high failure rate captured 45% of total wetland area in the post-dam period. Results of eco-hydro-deficit exhibited that eco-hydro-deficit areas increased from 11.22% to 52.19% and 35.03%–52.67% respectively in post-dam conditions indicating growing ecological stress. The TSI models showed that most parts of the wetlands were converted from oligotrophic to meso-eutrophic state signifying the qualitative degradation of water and potential ecosystem health. The area under high TSI was observed in the wetland area having eco-hydro-deficit and high hydrological failure rate zones. These characteristics of wetland areas were found at the fringe of wetlands and fragmented smaller wetland units. The study concluded that damming over the Punarbhaba River adversely affected the water security of the floodplain wetlands in terms of modifying the hydrological richness, ecological condition of the wetland habitat, and ecological systems. The findings of the present study could provide a comprehensive research on the monitoring of surface water crisis in the wetlands, which will be the basic foundation to formulate water resource management plans for conservation, management and restoration of wetlands.

Influence of Dry Beach on the Dynamic Stability of Ash Storage Field: A Numerical Analysis

Ash storage sites are a commonly used method of disposing fly ash, a byproduct of coal combustion, in China today, and when it accumulates to a certain height, serious geological hazards may occur as a result of seismic activity. In this study, an in situ standard penetration test was carried out on a constructed ash storage site in Northwest China to evaluate the potential for liquefaction of alluvial fly ash within the site, and the results show that dynamic liquefaction can occur within a newly constructed three-stage subdam. A numerical analysis of the influence of dry beach length on the dynamic response of the primary dams and subdams and an assessment of the extent of dynamic liquefaction in the ash storage field were carried out using the Wenchuan seismic waves as input ground motion. Numerical results prove that the acceleration within the ash storage field is relatively low in the original breccias layer and gradually increases with height, with the peak acceleration occurring in the vicinity of the third subdam and a decreasing trend from the subdams towards the ash storage field. As the length of the dry beach increases, the Peak accelerations in the ash storage area occur near the third subdams at larger dry beach length. Meanwhile, the acceleration in the ash storage area close to the surface gradually increases, and, significantly, the range where higher accelerations occur also becomes larger. The maximum horizontal displacements at different dry beach lengths occur at the crest of the third subdam and in the adjacent ash storage area. As the length of the dry beach increases, the maximum horizontal displacements show a certain decrease, but they occur progressively further away from the third subdam, so that, under dynamic action, the dams become safer. The extent of liquefaction decreases at larger dry beach length and extends further away from the third subdam into the ash storage area. It is, therefore, recommended that the length of the dry beach should not be less than 150 m for this ash storage site.

Seismic response of large earth dams in near-source areas

The paper focuses on the seismic response of earth dams close to active faults. The engineering implications of such an issue may be crucial since many existing dams, which have been in operation for several years, are located nearby or even on seismogenic faults. Owing to their size, large earth dams could dramatically be compromised by near-source ground motion. The spatial variability of the incoming seismic wave could promote differential settlements in the dam body and consequently fractures in the watertightness elements with an overall decrease of dam safety. The paper refers to the iconic case of Conza Dam in Italy. During its construction, it was seriously damaged by the catastrophic 1980 Irpinia earthquake (M = 6.9), whose epicenter was very close to the dam site. To model the seismic wave propagation from the causative fault to the dam site, a physics-based approach has been adopted by implementing the domain reduction method to simulate the whole boundary value problem. Two models were hence considered: a regional model, containing the source and the propagation medium of the Campania region basin, and a site model containing the upper foundation soils and the dam body.The paper compares the different response of the dam in the hypothesis of contemplating or disregarding near-source effects. Finally, the dam performance to seismic scenarios resembling the source mechanism of the 1980 Irpinia earthquake was analysed to ascertain the resilience of the dam to future earthquake scenarios having source characteristics similar to those of the 1980 event.

Role of negative pressure in structural responses of gravity dams to underwater explosion loadings: The need to consider local cavitation

Negative pressure tends to occur at a fluid–structure interface (FSI) in an underwater explosion (UNDEX) event. When the pressure drops to a value of vapor pressure, distributed cavities will form and maintain the pressure acting on the FSI during expansion, i.e. the local cavitation phenomenon. The local cavitation phenomenon is likely to occur at a dam-water interface when the dam is undergoing an UNDEX impact. It should significantly change the hydrodynamic-pressure distribution on the dam face and thus have an important influence on the response of the dam. Unfortunately, far too little attention has been paid to local cavitation in the current UNDEX resistant design and evaluation of dams. In this work, a dynamic analysis of a 72.12-m-high gravity dam (non-overflow monolith) undergoing an UNDEX impact is carried out with ABAQUS/Explicit. The ability of the employed software to capture the negative pressure at a FSI in an UNDEX event is validated by comparing the simulated pressure history at a water-plate interface with the analytical solution and experimental data reported in the literature. The simulation shows that significant negative pressure would arise at the dam-water interface without a zero-value cavitation limit considered. The negative pressure would produce overestimated tensile damage to the dam face but underestimated one to the dam base. A more reasonable prediction of the hydrodynamic-pressure distribution on the dam face should be obtained when the local cavitation effect is considered, which prevents the dam face from undergoing exaggerated negative pressure. It is therefore suggested that the local cavitation effect should be considered in future UNDEX resistant design and evaluation of dams, however, with cautious use of the cavitation threshold.

Stability Assessment of Zoned Earth Dam under Water Particles Fluidity Effect: Hemren Dam as Case Study

Recently the numerical modeling using finite element method is take into account as a very effective tool to investigate the desired behavior of structures in geotechnical engineering. Earth dams are a water retention structures that are normally wide constructed around the world due to its significant features. These structures may be failed due to exposure to an earthquake and this will result in disaster. The main objective of this study is to assess the slope stability and the seismic response of an earthen dam. Since the matter of seismic response is still have a considerable lack of information for earth dams as a unique structure. Hemren zoned earth dam that is located in Diyala governorate, northeast of Iraq that considered as an active seismic zone has been considered as case study. Numerical modeling has been done in this study using Geo studio software. Factor of safety was calculated with different water levels in order to evaluate the dam safety with different operation water level. The excited earthquake is Elcentro while three values of peak ground acceleration were used which are 0.2, 0.25 and 0.3 g and the duration time is scaled to 10 seconds. In addition, three key points (at the core, the shell and the foundation) that represent the dam construction material are used to evaluate the dynamic response within the dam body. The results revealed that the factor of safety is increased when the water level is increase, but in the increasing in the magnitude of factor of safety with water depths of (10 and 15) m was more than the other depth. The zone of the dam core shows a negative pore water pressure value. That leads to an increasing in effective stress at the core of the dam.

Effect of vertical input motion and excess pore pressures on the seismic performance of a zoned dam

This paper investigates the combined effect of the vertical component of the input motion and of the weakening effect associated to pore-pressure build-up with reference to a zoned earth dam for which the most recent probabilistic seismic hazard analyses promoted the need of evaluating its seismic performance.The two effects were studied through advanced plane-strain non-linear dynamic analyses using a finite-difference numerical model calibrated on an accurate geotechnical characterisation. The occurrence of ultimate limit states in the dam embankment is checked using sets of horizontal and vertical input motions properly selected to account for possible frequency coupling with the dam.The analysis results are presented and discussed in the paper focusing on (i) the main features of the plastic mechanisms temporarily induced by the seismic actions, (ii) the amplification of the horizontal and vertical accelerations acting in the dam body, (iii) the role of the energy and frequency content of the input motion on the magnitude of earthquake-induced permanent displacements, (iv) the combined effect of frequency coupling and non-linear soil behaviour on the overall dam response.

Effect of correlated random fields on nonlinear dynamic responses of gravity dam

Uncertainty will inevitably be introduced into the structural analysis, while randomness is an important manifestation of uncertainty. Based on the random field theory, the correlated random fields of the Koyna gravity dam were realized, and the influence of the randomness of material parameters on the nonlinear responses of the gravity dam was investigated. A concrete continuum crack model was employed to describe the nonlinear mechanical behavior of gravity dams under static and dynamic loads. To avoid the contingency caused by the initial random samples, the comparisons of the nonlinear dynamic responses of the dam are based on the statistical analysis of a large number of random fields. The parameter sensitivity analysis is first implemented, and then, the nonlinear responses of the proposed correlated random field model and the conventional random variable-based model are comprehensively compared. The analysis showed that the randomness and spatial correlation of materials would affect the seismic performance of gravity dams, which should be considered in structural design and seismic risk analysis.

Effect of Halabjah Earthquake on Al-Wand Earth Dam: Numerical Analysis

The Halabja earthquake occurred on 12/11/2017 in Iraq, with a magnitude of 7.3 Mw, which happened in the Iraqi-Iranian borders. This earthquake killed and injured many people in the Kurdish region in the north of the country. There is no natural disaster more dangerous than earthquake, especially it occurs without warning, great attention must be paid to the impact of earthquakes on the soil and preparing for a wave of earthquakes. Numerical modeling using specific elements is considered a powerful tool to investigate the required behavior of structures in Geotechnical engineering, and the main objective of this is to assess the response of the Al-Wand dam to the Halabja earthquake, as this dam is located in an area that has been subjected to seismic activity recently. The modeling was done through the Geo-studio program, where the seepage was analyzed during the Al-wand dam using the Seep/w program. It was verified that the dam was safe against seepage failure and then moved to the QUAKE/W (a subprogram of GEOSTUDIO, which is used for liquefaction modeling of earthquakes and dynamic loading and determines the movement and increased pressures of pore water that arise due to earthquake vibration or sudden shock loads). The program was used to analyze the effect of the earthquake on the porewater pressure, effective stresses, and displacements. Also, it is not clear that the significant impact the earthquake has on these values. Finally, the Slope/w program was used to analyze the stability of the dam and to calculate the safety factor of the dam in two ways, and the results of the analysis show that the dam is considered safe under the influence of the tremor.

Dynamic analysis of earth dam using numerical method – a case study: Doyraj earth dam

The precise study of the response of earth dams to earthquakes is one of the most complex issues in the field of soil structures. In this research, dynamic analysis of earth dam structures (a case study: Doyraj dam in the west of Iran) have been performed using 2D Finite Difference Method (2D F.D.M.). The aim of this study is to investigate accelerations, lateral (horizontal) and vertical displacements (i.e. settlements) due to earthquake occurrence. The results of dynamic analysis indicate that the performance of the dam is satisfactory for each one of the seismic scenarios considered in this investigation. The maximum settlements at the dam crest is considerably smaller than that of the dam freeboard, with maximum value of 540 mm, which is comparable to recommendation of the Department of Safety of Dams (DSOD). Depth of sliding surfaces is better shown in the Finn model, and the settlements based on the Finn model is about 2.5 times higher than that of Mohr model. In contrast to what is commonly accepted about earthquake acceleration (the increase in earthquake acceleration from the base to the top of the dam), it cannot generalize to all cases, and it can be limited to very strong dams or can be related to poor earthquakes.

Transient response of “Brezina concrete arch dam”–“Reservoir water”–“Rock foundation” system

Abstract In this paper, transient responses of the Brezina concrete arch dam, located in the west of Algeria, are determined using the finite elements commercial package, Ansys. A 3D model has been created to study the rock–fluid–structure interaction phenomenon. The foundation rock is modeled as a mass rock using solid finite elements, and the reservoir water is modeled using fluid finite element for the 3D model; the length and width of the foundation rock and water reservoir, along the global X and Y axes, are taken to be 150 m and 300 m, respectively, while its depth (or height), along the Z direction, is taken to be 100 m (the total height of the model is thus 160 m considering that the reservoir water height is taken to be 50 m). Coupling equations available in the Ansys code library are used to represent the dam–water and dam–foundation interfaces. It is found that the role of the reservoir water is mixed. In some cases, its presence is like a damper, which means it decreases the range of displacement or stresses, whereas in other cases, it increases or has a negligible effect on these quantities. A notable finding is the magnitude of the calculated stresses, which stands at a very low level, either with or without water. An in-depth review of the literature reveals that the study carried out in this research encompasses several elements of originality, as only very few similar works have been undertaken.