Behavior Of Dams Research Articles

Earthquake Behavior of Concrete Gravity Dams During Ground Motions

Abstract The stability evaluation of the dams subjected to seismic excitations is really very complex as the earthquake response of the concrete gravity dam depends upon its connection joints with foundation rock. This study presents the seismic response of concrete gravity dams considering welded contact and friction contact and along dam-foundation rock interface. Friction contact is provided using contact elements. Two-dimensional finite element model of Oued Fodda concrete gravity dam, located in Chlef at the northwestern part of Algeria, is used for this purpose. Nonlinear analyses of dam-foundation rock system are performed using ANSYS software. The reservoir water is modeled as added mass using the Westergaard approach. The Druker-Prager model is employed in the nonlinear analysis for dam concrete. The surface-to-surface contact elements based on the Coulomb's friction law are used to describe the friction. These contact elements use a target surface and a contact surface to form a contact pair. According to this study, when the friction contact is considered in joints, sliding displacement of dam base occurs along the dam-foundation rock interface. The dam sliding along its foundation decreases the deformation response; principal stresses in the dam body and shear force at both the heel and toe of the dam.

A multi-target prediction model for dam seepage field

Prediction of dam behavior based on monitoring data is important for dam safety and emergency management. It is crucial to analyze and predict the seepage field. Different from the mechanism-based physical models, machine learning models predict directly from data with high accuracy. However, current prediction models are generally based on environmental variables and single measurement point time series. Sometimes point-by-point modeling is used to obtain multi-point prediction values. In order to improve the prediction accuracy and efficiency of the seepage field, a novel multi-target prediction model (MPM) is proposed in which two deep learning methods are integrated into one frame. The MPM model can capture causal temporal features between environmental variables and target values, as well as latent correlation features between different measurement points at each moment. The features of these two parts are put into fully connected layers to establish the mapping relationship between the comprehensive feature vector and the multi-target outputs. Finally, the model is trained for prediction in the framework of a feed-forward neural network using standard back propagation. The MPM model can not only describe the variation pattern of measurement values with the change of load and time, but also reflect the spatial distribution relationship of measurement values. The effectiveness and accuracy of the MPM model are verified by two cases. The proposed MPM model is commonly applicable in prediction of other types of physical fields in dam safety besides the seepage field.

Poly(I:C)-induced maternal immune activation causes elevated self-grooming in male rat offspring: Involvement of abnormal postpartum static nursing in dam.

Introduction: Maternal immune activation (MIA) is closely related to the onset of autism-like behaviors in offspring, but the mechanism remains unclear. Maternal behaviors can influence offspring's development and behaviors, as indicated in both human and animal studies. We hypothesized that abnormal maternal behaviors in MIA dams might be other factors leading to delayed development and abnormal behaviors in offspring. Methods: To verify our hypothesis, we analyzed poly(I:C)-induced MIA dam's postpartum maternal behavior and serum levels of several hormones related to maternal behavior. Pup's developmental milestones and early social communication were recorded and evaluated in infancy. Other behavioral tests, including three-chamber test, self-grooming test, open field test, novel object recognition test, rotarod test and maximum grip test, were performed in adolescence of pups. Results: Our results showed that MIA dams exhibit abnormal static nursing behavior but normal basic care and dynamic nursing behavior. The serum levels of testosterone and arginine vasopressin in MIA dams were significantly reduced compared with control dams. The developmental milestones, including pinna detachment, incisor eruption and eye opening, were significantly delayed in MIA offspring compared with control offspring, while the weight and early social communication showed no significant differences between the two groups. Behavioral tests performed in adolescence showed that only male MIA offspring display elevated self-grooming behaviors and reduced maximum grip. Discussion: In conclusion, MIA dams display abnormal postpartum static nursing behavior concomitantly with reduced serum levels of testosterone and arginine vasopressin, possibly involving in the pathogenesis of delayed development and elevated self-grooming in male offspring. These findings hint that improving dam's postpartum maternal behavior might be a potential regime to counteract delayed development and elevated self-grooming in male MIA offspring.

Creep behavior and permeability evolution of coal pillar dam for underground water reservoir

Using goof as water storage space plays a vital role in the ecological environment and economic development of arid mining areas, while the rock strength and the stability of coal pillars in underground water reservoirs are closely related to creep process. In this work, triaxial creep-seepage tests were conducted for coal samples to develop new insights into the creep behavior and permeability evolution. The results showed that the creep deformation and permeability evolution of coal samples exhibit three stages, namely, the compaction hardening stage before the stress threshold, volumetric compaction stage, and volumetric dilatancy stage. The coal permeability decreases first and then increases with the creep strain and it is well correlated with the variation of volumetric strain.

Ordinary Kriging Interpolation Method Combined with FEM for Arch Dam Deformation Field Estimation

The deformation characteristic of the arch dam can directly reflect its service performance, which can be analyzed on the basis of the dam deformation field. However, restricted by the limited number of dam monitoring points and the inhomogeneity of materials, an accurate measurement of arch dam deformation field is difficult to estimate by using the existing common methods, such as the spatial interpolation methods and the finite element method (FEM). With the aim of ensuring arch dam structure safety, the ordinary kriging interpolation method, combined with FEM, is proposed for arch dam deformation field estimation, in this study. Given the inversion of the computation parameters of the arch dam, FEM is used to calculate the basic arch dam deformation. Subsequently, the ordinary kriging interpolation method is introduced to estimate the spatial variance deformation at each point of the arch dam. One superhigh arch dam in China is selected as a case study; two additional methods are introduced as comparisons that are based on a numerical experiment and the actual monitoring data. The experimental results show that the proposed method considerably improves the accuracy and computational efficiency of the arch dam deformation field estimation and that it is of great practical importance for characterizing the deformation behavior of arch dams.

Analysis of the behavior of a high earth-core rockfill dam considering particle breakage

This paper presents a finite element analysis for the behavior of the Lianghekou high earth-core rockfill dam, which was just completed in construction in China. An elastoplastic constitutive model that can account for the degradation of rockfills due to particle breakage (hhu-SH-breakage model) was applied to simulate the mechanical behavior of the rockfills. The earth-core wall was analyzed by using the modified Cam-clay model combined with the Biot’s consolidation theory. Numerical results are in good agreement with in-situ measurements during construction, indicating the reasonability of the numerical analysis. Based on the breakage-packing concept, which is able to extract the breakage-induced deformation from the total deformation, numerical analysis showed that the breakage-induced settlement for the extra high rockfill dam is not negligible. Inspired by the sensitivity analysis using the hhu-SH-breakage model, engineering advices were proposed to reduce the settlement of high rockfill dams.

Evaluating the Relationship between Reservoir Level Changes and Earthquake Damage Responses of High Arch Dams: A 3D Numerical Study of Ermenek Arch Dam (220 m) in Turkey

Examining the earthquake behaviors of important water structures such as arch dams is of great importance for the future and safety of these structures. Besides, different reservoir heights, which occur as a result of different seasonal precipitation, can cause great losses in the structural behavior of arch dams. For this reason, in this study, the effects of various reservoir water heights on the earthquake behavior of arch dams are evaluated by considering a creep material model. Ermenek dam, one of the highest dams in Turkey, is chosen for the 3D (3D) numerical analyses. This dam has 4 different gallery spaces in its body and it has a body height of 220 m. While creating a 3D finite-different model of the dam, the creep material models are utilized for the concrete and foundation sections. For the 3D earthquake analyses, free-field and quiet nonreflecting boundary conditions (BCs) are defined to the boundaries of the model. Besides, fix BCs are added to the base of the dam. While creating the gallery spaces of the dam, the original dam project is taken into consideration, and attention is paid to creating the oval geometry of the gallery spaces following the project. For earthquake analyses, 4 different water levels (25 m, 85 m, 150 m, and 200 m) are considered, and hydrostatic forces and water table are used while generating the reservoir water. Furthermore, a total of 18 different strong ground motions are used in the earthquake analyses to examine the earthquake behavior of the dam. According to the earthquake analyses, it is concluded that different reservoir heights have great effects on the earthquake behavior of the Ermenek dam. Moreover, it has been observed that the height of the reservoir water causes significant earthquake stress and displacement differences around the gallery spaces of the dam.

Towards a Better Understanding of Concrete Arch Dam Behavior during the First Filling of the Reservoir

During the first filling, the reservoir is gradually raised in multiple stages. At each stage, the filling is paused to allow adequate time for monitoring and evaluating the performance of the dam and its foundation. The analysis of the monitored behavior and assessment of security conditions is performed by comparing the values measured by the monitoring system installed in the dam with the values predicted by numerical models representing the structural behavior, the material properties, and the loads. This article addresses the main aspects related to the safety control of concrete arch dams during the first filling of the reservoir. Special attention is given to the nonlinear behavior induced by the opening/closing of the contraction joints. An example of numerical simulation of the behavior of an arch dam during the first filling of the reservoir is also presented. The validation of the computed temperatures, the induced displacements and the induced stresses was performed by comparison with the values measured with the monitoring system installed in the dam.

Displacement prediction model for high arch dams using long short-term memory based encoder-decoder with dual-stage attention considering measured dam temperature

Structural health monitoring method can provide important information to evaluate operational status of concrete dams, by establishing accurate models to predict concrete dam behavior with monitored data. This study proposed a model using encoder-decoder based on long short-term memory network with dual-stage attention mechanism (DALSTM) to predict the displacement of concrete arch dams. Encoder-decoder based on long short-term memory network is a deep learning technique that can perform time series prediction, and dual-stage attention mechanism focuses on the key information in the dam displacement series to improve the performance. The effectiveness and accuracy of the proposed prediction model are analyzed on a high arch dam using measured temperature in the dam body instead of the seasonal functions to represent the thermal effect. Compared with traditional stepwise regression, multiple linear regression models, radial basis function networks, and other deep learning models, results show that the proposed approach performance is more accurate and robust for dam health monitoring.

Risk Evaluation of the Sanalona Earthfill Dam Located in Mexico Using Satellite Geodesy Monitoring and Numerical Modeling

Dams are essential structures in the growth of a region due to their ability to store large amounts of water and manage it for different social activities, mainly for human consumption. The study of the structural behavior of dams during their useful life is a fundamental factor for their safety. In terms of structural monitoring, classic terrestrial techniques are usually costly and require much time. Interferometric synthetic aperture radar (InSAR) technology through the persistent scatterer interferometry (PSI) technique has been widely applied to measure millimeter displacements of a dam crest. In this context, this paper presents an investigation about the structural monitoring of the crest of the Sanalona dam in Mexico, applying two geodetic satellite techniques and mathematical modeling to extract the risk of the dam–reservoir system. The applicability of the InSAR technique for monitoring radial displacements in dams is evaluated and compared with both GPS systems and an analytical model based on the finite element method (FEM). The radial displacements of the Sanalona dam follow a seasonal pattern derived from the reservoir level, reaching maximum radial magnitudes close to 13 mm in November when the rainy season ends. GPS recorded and FEM simulated maximum displacements of 7.3 and 6.7 mm, respectively. InSAR derived radial displacements, and the reservoir water level presented a high similarity with a correlation index equal to 0.8. In addition, it was found that the Sanalona dam presents the greatest deformation in the central zone of the crest. On the other hand, based on the reliability analysis, the probability of failure values lower than 8.3 × 10−2 was obtained when the reservoir level was maximum, which means that the radial displacements did not exceed the limit states of the dam–reservoir system in the evaluated period. Finally, the extracted values of the probability of failure demonstrated that the Sanalona dam does not represent a considerable risk to society.

Multi-source data-driven unsaturated seepage parameter inversion: Application to a high core rockfill dam

The inverse parameter’s estimation of unsaturated seepage models is important to ensure the safety of earth dams, while most existing studies determine the hydraulic characteristics only based on seepage pressure monitoring data, which may lead to inversion results deviating from the intrinsic properties of dam materials. This study proposed an advanced methodology for unsaturated seepage parameter inversion of earth dams driven by multi-source data. The transient unsaturated seepage behavior of earth dams is simulated using the Van Genuchten (VG) model, and the extreme learning machine (ELM) is adopted as the surrogate model to estimate the approximate simulation results. Then the multi-objective function for parameter inversion is constructed by combining the observed transient pressure data and ELM models, and the Pareto-optimal solutions are generated using the elitist non-dominated sorting genetic algorithm (NSGA-II). Multi-source information, including parameter design values, in-situ testing results, and monitoring data, are fused to construct a comprehensive index to drive the parameter decision. The proposed method is applied to the PB core rockfill dam, which has a well-established seepage pressure monitoring system. In addition, the design values and in-situ testing results of the hydraulic conductivity of the dam material are also available. The results showed that the inversion parameters of the proposed method are closer to the physical characteristics of materials and have advantages in prediction accuracy.

Prediction and interpretation of the deformation behaviour of high arch dams based on a measured temperature field

Prediction and interpretation of the deformation behaviour of high arch dams based on a measured temperature field

Characterization of Relative Movements between Blocks Observed in a Concrete Dam and Definition of Thresholds for Novelty Identification Based on Machine Learning Models

Dam surveillance activities are based on observing the structural behaviour and interpreting the past behaviour supported by the knowledge of the main loads. For day-to-day activities, data-driven models are usually adopted. Most applications consider regression models for the analysis of horizontal displacements recorded in pendulums. Traditional regression models are not commonly applied to the analysis of relative movements between blocks due to the non-linearities related to the simultaneity of hydrostatic and thermal effects. A new application of a multilayer perceptron neural network model is proposed to interpret the relative movements between blocks measured hourly in a concrete dam under exploitation. A new methodology is proposed for threshold definition related to novelty identification, taking into account the evolution of the records over time and the simultaneity of the structural responses measured in the dam under study. The results obtained through the case study showed the ability of the methodology presented in this work to characterize the relative movement between blocks and for the identification of novelties in the dam behaviour.

Dynamics of earth dams under shock impacts

The article provides a detailed analysis of well-known studies, which allow considering the work of the structure together with the base under dynamic influences, adequate replacement of an infinite base with a finite one using non-reflecting conditions on the boundary of the finite region, well-known methods for assessing the behavior of a structure under impact. A mathematical model, method, and algorithm were developed to evaluate the dynamic behavior of earth dams together with the base under shock impact using non-reflective conditions based on Rayleigh waves on the boundaries of the finite area of the base. To simulate a dynamic process, the principle of virtual displacements is used, taking into account the viscoelastic properties of the material. The solution to the problem is conducted by the finite element method and the Newmark method. The dynamic behavior of earth dams, together with the base, is studied, considering non-reflecting conditions under explosive impacts that arise not far from the structure. It was established that during the period of wave travel, a non-synchronous movement of individual parts of the dam occurs, damped due to the wave entrainment of energy and the viscoelastic properties of the material. It was revealed that the maximum principal stresses σ1 occur in the lower part of the upper slope of the dam and gradually spread along the entire dam; the maximum principal stresses σ2 are reached near the foot of the dam and, as the wave propagates, they move along the base directly behind the wavefront; the maximum values of shear stress σ12 are reached on the surface of the upper slope, first at the foot of the dam, then over the entire surface of the slope.

Investigation of dynamic behavior and stress-strain state of soil dams taking into account physically Non-linear properties of soils

The article presents the results of a study of the dynamic behavior and stress-strain state of the Rezaksay soil dam taking into account the physically nonlinear properties of soils, in a flat setting. A mathematical model developed for the study of earth dams is presented. based on the Lagrange variational equation using the d'Alembert principle. As a computing device, the finite element method is used in the work. At the same time, it was determined that the stress-strain state and dynamic behavior of a soil dam significantly depend on the physical and mechanical properties of soils, the commensurability of the geometric dimensions, and theslope coefficients of the dam thrust prisms.

Dynamic behavior of earth dams under different kinematic impacts

The paper provides a detailed analysis of the current state of the problem. A mathematical model is presented to determine the dynamic behavior of earth dams, considering the viscoelastic properties of soil, using the hereditary Boltzmann-Volterra theory with the A.R. Rzhanitsyn kernel under periodic kinematic impacts. To solve the problems considered, the finite element method and complex arithmetics were used to reduce integrodifferential equations to a high-order complex algebraic equation. The accuracy of the methods was verified by solving test problems. Steadystate forced vibrations of the Pskem earth dam 195 m high are studied considering the real geometry and soil properties under resonant vibration modes. It was stated that the largest stress amplitudes in the body of the dam occur not only under the first resonance, but they can occur under other dense spectra of the eigenfrequencies of the dam, due to the interaction between close natural modes of vibration. The strength of various sections of the dam body was tested under kinematic impact using the Coulomb- Mohr theory of strength; the most dangerous sections of the dam were identified in terms of the highest stress.

Prolactin and glucocorticoid receptors in the prefrontal cortex are associated with anxiety‐like behavior in prenatally stressed adolescent offspring rats

Prenatal stress (PS) causes anxiety in mothers and their offspring and chewing is a commonly observed behavior during maternal stress. Prolactin (PRL) is an anti-anxiety factor that suppresses the hypothalamic-pituitary-adrenal axis. Here, we studied the roles of PRL, corticosterone (CORT), and their receptors in PS-induced anxiety-like behavior in dams and their offspring. We further investigated whether chewing during maternal stress could prevent PS-induced harmful consequences. Pregnant rats were randomly divided into PS, PS + chewing, and control groups. Anxiety-like behaviors of dams and their adolescent offspring were assessed using the open field test and elevated plus maze. Serum levels of PRL and CORT were measured by ELISA. Expression of mRNA and protein of PRLR and glucocorticoid receptor (GR) in the prefrontal cortex (PFC) were evaluated by qRT-PCR and western blotting, respectively. Compared to the control rats, dams and their female offspring, but not male offspring, in the PS group showed increased anxiety-like behaviors. The PS-affected rats had a lower serum PRL level and increased PRLR expression in the PFC. In contrast, these rats had a higher serum CORT level and decreased GR expression in the PFC. Chewing ameliorated anxiety-like behaviors and counteracted stress-induced changes in serum PRL and CORT, as well as the expression of their receptors in the PFC. Conclusion: PS-induced anxiety-like behavior is associated with changes in the serum levels of PRL and CORT and expression of their receptors in the PFC. Moreover, chewing blunts the hormonal and receptor changes and may serve as an effective stress-coping method for preventing PS-induced anxiety-like behavior.

Strength of earth dams considering the elastic-plastic properties of soils

The article provides a detailed review of well-known publications devoted to studying the stress state and dynamic behavior of earth dams, taking into account the elastic and elastic-plastic properties of soil. To assess the stress-strain state of earth dams, considering the elastic-plastic properties of soil under the action of static loads, a mathematical model was developed using the principle of virtual displacements. A technique, algorithm, and computer programs were developed for estimating the stress state of dams using the finite element method and the method of variable elasticity parameters. A test problem was solved to assess the adequacy of the developed models and the reliability of the technique, algorithms, and computer programs. The stress-strain state of the Pskem earth dam, 195 m high, was studied using the developed models and calculation methods, taking into account the elastic-plastic properties of soil under the action of body forces and various levels of filling the reservoir with water. It was established that an account for the elastic-plastic properties of soil leads to a sharp change in the stress state of the dam, especially in the upper prism and in the core of the dam, and changes the intensity of normal stresses, which can lead to a violation of the integrity of the dam.

Dynamic behavior of earth dams under short-term semi-harmonic loads

The article is devoted to the dynamic problems of studying the strain state of earth dams under dynamic impacts. A method is developed for solving wave problems to determine the stress-strain state of earth structures, in particular, earth dams. Based on the use of the finite difference method, an algorithm for solving problems and calculation formulas were developed that have second-order accuracy in time and coordinates. The advantage of the developed method is the implementation of complex nonlinear deformation models, taking into account structural changes and moisture content of soil. In the example of the Charvak dam, the distribution of the stress state over the cross-section of the dam under the action of its own weight is determined and the problem of the dynamic behavior of an earth dam under the influence of short-term harmonic loads is numerically solved. The change in intense stresses at some points of the earth dam over time is determined.

Evaluating dynamic behaviour of a concrete dam using modal analysis

Modal Analysis is the most fundamental aspect of the dynamic study of structures. It is used to determine the vibrational characteristics of linear elastic structures. It suggests the natural frequencies and mode shapes, which are essential to understand the dynamic behaviour of that structure. In this study, Shahpurkandi Dam, a concrete gravity dam of height 55.5 m is considered in order to investigate its dynamic properties using the finite element package ‘ANSYS’. Furthermore, structure-acoustic interaction is explicitly modelled, and a case of the full reservoir is taken into account to analyze the modal response of the dam. The first 6 mode shapes are extracted, and the total displacement is recorded through the numerical simulation of the direct solver including the block Lanczos method. This study shows the maximum deformation is recorded for the first fundamental natural frequency, which is 0.0039 mm at the crest of the dam. Henceforth, it is essential to monitor the mode shape and natural frequency of initial modes. The comparison of natural frequency is also demonstrated for full reservoir and empty reservoir cases.