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The failure mechanism of a gravity dam under blast loading is much more complex than failure under other dynamic loads such as earthquakes. It is therefore important to evaluate the safety performance of these structures under blast load. The structural dynamic behaviour of Koyna dam, India, subjected to underwater explosion (UndEx) was investigated. The Johnson–Holmquist 2 model was used to capture the non-linear response of concrete. The dam–reservoir interaction was modelled using the coupled acoustic–structural technique, which employs a total wave formulation to incorporate the propagation of spherical shock waves. Dynamic responses such as displacement, damage profiles and principal stresses under various detonation depths, weights and reservoir levels were examined. The findings indicated that areas facing the explosion experience the most damage, while local damage occurred at the dam's heel as the explosion depth increased. Additionally, displacement decreased notably as the TNT depth increased for a consistent explosive amount. The damage distribution in the dam was found to depend on both TNT depth and weight. Damage accumulation in the dam was substantially reduced by lowering the reservoir height (five different levels were assessed). The results provide valuable insights into the Koyna gravity dam's response to UndEx under varying conditions. [ABSTRACT FROM AUTHOR]

Integrating long-term observational data analysis with numerical simulations of dam operations provides an effective approach to dam safety evaluation. However, analytical results are often subject to errors due to challenges in accurately surveying and modeling the foundation, as well as temporal changes in foundation properties. This paper proposes a concrete dam displacement separation model that distinguishes between deformation caused by foundation restraint and that induced by external loads. By combining this model with intelligent optimization techniques and long-term observational data, we can identify the actual mechanical parameters of the dam and conduct structural health assessments. The proposed model accommodates multiple degrees of freedom and is applicable to both two- and three-dimensional dam modeling. Consequently, it is well-suited for parameter identification and health diagnosis of concrete gravity and arch dams with extensive observational data. The efficacy of this diagnostic model has been validated through computational case studies and practical engineering applications. [ABSTRACT FROM AUTHOR]

The safety condition of concrete gravity dams is influenced by multiple factors, and assessing their safety solely based on a single factor is difficult to comprehensively evaluate. Therefore, this paper proposes a comprehensive modeling and analysis approach to assess dam safety by considering long-term temperature, stress, and strain monitoring data of actual concrete gravity dams. Firstly, the K-means clustering algorithm is utilized to classify the data. Then, the study area of the dam is meshed and three indicator evaluation values for all the elements are calculated. The other elements' evaluation values can be obtained by the Inverse Distance Weighting (IDW) method. Finally, the analytic hierarchy process extended by the D numbers preference relation (D-AHP) method is applied to compute the weights of temperature, stress, and strain and evaluate the dam's safety comprehensively. The effectiveness of this method is validated through application to specific engineering cases. The results demonstrate that compared to assessing methods considering only single factors, the comprehensive evaluation method proposed in this paper can more comprehensively and accurately reflect the actual safety condition of concrete gravity dams, providing important references for engineering decision-making. [ABSTRACT FROM AUTHOR]

The parameters of gravity dams and foundation materials objectively exhibit spatial variability due to environmental and load influences, which significantly affect the safety status of dam structures. Therefore, a safety risk analysis method for a gravity dam–foundation system based on random field theory is proposed in this paper. Spatial variabilities in materials are particularly considered by using the finite element method. Then, composite response surface equations for the performance function (PF) of strength and stability failure are established, and then, the system failure risk is obtained using the Monte Carlo method. The proposed method solves the problem wherein the effect of spatial variability on failure risk cannot be reflected accurately by the performance function of multi-element sliding paths, and the difficulties in solving the failure risk of the series–parallel system due to multiple failure paths and their complex correlations. The application of a gravity dam shows that the developed method overcomes the disadvantages of the traditional method, such as the homogenization of the spatially random characteristics of parameters and the overestimation of failure risk in the system due to large variance estimation. [ABSTRACT FROM AUTHOR]

Assessment of flood damage caused by dam failures is typically performed deterministically on the basis of a single preselected scenario, neglecting uncertainties in dam-break parameters, exposure information, and vulnerability model. This paper proposes a probabilistic flood damage model for the estimation of life loss due to dam-break flooding with the aim of overcoming this limitation and performing a more comprehensive and informative evaluation of flood risk. The significant novelty lies in the fact that the model combines uncertainties associated with all three components of risk: hazard, exposure, and vulnerability. Uncertainty in flood hazard is introduced by considering a set of dam-break scenarios, each characterized by different breach widths and reservoir levels. Each scenario is linked to a probability, which is assumed conditional on the dam-break event. Uncertainty in exposure is accounted for using dasymetric maps of the population at risk for two socio-economic states (representing business and non-business hours of a typical week), along with associated likelihood. Vulnerability to flooding is described through a well-established empirical hazard-loss function relating the fatality rate of the population at risk to the flood hazard, the flood severity understanding, and the warning time; a confidence band provides quantitative information about the associated uncertainty. The probabilistic damage model was applied to the case study of the hypothetical collapse of Mignano concrete gravity dam (northern Italy). The main outcome is represented by probabilistic flood damage maps, which show the spatial distribution of selected percentiles of a loss-of-life risk index coupled with the corresponding uncertainty bounds. [ABSTRACT FROM AUTHOR]

Purpose: The effective numerical model that examines the seismic behavior of concrete gravity dams in the Laplace domain-Finite Element (FE) approach is presented. Further research on seismic performance of the dam body is done considering the simultaneous effect of horizontal (H) and vertical (V) components of six different earthquake loads. The time durations of the selected earthquakes vary from 10 to 80 s with the magnitude range from 6.5 to 7.62 Mw. Methods: The Lagrangian fluid finite elements are utilized to model the near-field water domain, while the fluid infinite elements are utilized to model the far-field water domain. The two-dimensional (2D) FE model is developed in FORTRAN 90 and MATLAB programming languages. Results: The obtained results revealed that the longer length of significant earthquake duration leads to the high deformations, high stress excursions and high probability of damages in the dam body. 20.9% and 18.8% of the selected dam cross section experienced overstress condition under the H and H + V components of the Chi-Chi earthquake loads, respectively; this indicate the severe damages and even the dam failure. Conclusion: This study concludes that the seismic behavior of concrete gravity dam affects not only with the seismic severity; the length and significant time duration of the earthquake are also important factors should be considered in the seismic analysis and design of dams. [ABSTRACT FROM AUTHOR]

Although the failure of a concrete dam is a complex and highly dynamic process, the current safety assessments of concrete gravity and buttress dams rely on a simplified 2D stability analysis, which neglects the load redistribution due to 3D monolith interactions and the valley shape. In addition, the estimation of breach parameters in concrete dams is based on assumptions rather than analyses, and better prediction methods are needed. Model tests have been conducted to increase the understanding of the failure behavior of concrete dams. A scale model buttress dam, with a scale of 1:15, consisting of 5 monoliths that were 1.2 m in height and 4 m in width, was constructed and loaded to failure using water pressure. The model dam had detachable abutment supports and shear keys to permit variations in the 3D behavior. The results showed that the shear transfer was large between the monoliths and that the failure of a single dam monolith is unlikely. A greater lateral restraint gives not only a higher failure load but also a better indication of impending failure. These findings suggest that the entire dam, including its boundary conditions, should be considered during a stability assessment. The results also suggest that the common assumption in dam safety codes that a single monolith fails during flooding analysis is not conservative. The dataset obtained provides a foundation for the future development of dam-monitoring alarm limits and for predictive models of dam-breaching processes. [ABSTRACT FROM AUTHOR]

The displacement of concrete dams effectively reflects their structural integrity and operational status. Therefore, establishing a model for predicting the displacement of concrete dams and studying the evolution mechanism of dam displacement is essential for monitoring the structural safety of dams. Current data-driven models utilize artificial data that cannot reflect the actual status of dams for network training. They also have difficulty extracting the temporal patterns from long-term dependencies and obtaining the interactions between the targets and variables. To address such problems, we propose a novel model for predicting the displacement of dams based on the temporal convolutional network (TCN) with the attention mechanism and multioutput regression branches, named MLA-TCN (where MLA is multioutput model with attention mechanism). The attention mechanism implements information screening and weight distribution based on the importance of the input variables. The TCN extracts long-term temporal information using the dilated causal convolutional network and residual connection, and the multioutput regression branch achieves simultaneous multitarget prediction by establishing multiple regression tasks. Finally, the applicability of the proposed model is demonstrated using data on a concrete gravity dam within 14 years, and its accuracy is validated by comparing it with seven state-of-the-art benchmarks. The results show that the MLA-TCN model, with a mean absolute error (MAE) of 0.05 mm, a root-mean-square error (RMSE) of 0.07 mm, and a coefficient of determination (R2) of 0.99, has a comparably high predictive capability and outperforms the benchmarks, providing an accurate and effective method to estimate the displacement of dams. [ABSTRACT FROM AUTHOR]

A gravity dam monolith bounded by the transverse contraction joints on both sides is usually recognized as an independent element in various dynamic analyses. However, in most cases a gravity dam monolith is actually subdivided by longitudinal joints for mass concrete construction requirements. Previous studies of gravity dams subjected to underwater explosion (UNDEX) shock loadings have not dealt with the longitudinal-joint issue in much detail. In this work, a numerical simulation of the dynamic response of an old gravity dam without good longitudinal-joint connection integrity in an UNDEX event is performed. The coupled acoustic-structural analysis procedure with ABAQUS/Explicit is employed. The reliability of the procedure is validated by numerical simulations of two UNDEX impact tests in the literature. Nine calculation cases are considered to compare different responses of the dam with different connection states between monolith sections and underwater detonation depths. The results of this numerical investigation show that the longitudinal joints play an important role in the UNDEX response of the dam. The longitudinal joints greatly weaken the flexural rigidity of the dam and make the dam damaged in a piecemeal manner. This study adds to the rapidly expanding field of the UNDEX resistance performance evaluation of gravity dams by accounting more for the longitudinal-joint issue. The antiterrorism situation worldwide is experiencing constant changes, making the world continually face multiple unstable factors. Dams are easy attack targets for their enormous social and economic values. Among various dam types, gravity dams are commonly recognized to have the best blast resistance performance owing to their monumental body sizes. A gravity dam is routinely divided into several monoliths by transverse joints. Each monolith is then subdivided by longitudinal joints for mass concrete construction requirements. After the completion of a dam monolith, the longitudinal joints should be grouted to ensure the integrity of the monolith. For some dams serving several decades, their longitudinal-joint connection integrity might deteriorate. Such structural integrity losses should lead to blast resistance performance degradation. With this in mind, the authors carried out a series of numerical simulations of an old gravity dam when it is experiencing underwater explosion (UNDEX) shock loadings. Nine cases are considered concerning different longitudinal-joint connection states and UNDEX scenarios. This work clarifies the mechanism that the longitudinal-joint connection failure deteriorates the UNDEX resistance performance of the dam. Great efforts on reinforcing old dams through enhancing their longitudinal-joint connection integrity are thus needed to ensure their adequate blast resistance performance. [ABSTRACT FROM AUTHOR]

Deformation can directly reflect the working behavior of the dam, so determining the deformation monitoring control value can effectively monitor the safety of dam operation. The traditional dam deformation monitoring control value only considers the single measuring point. In order to overcome the limitation, this paper presents a new method to determine the monitoring control value for concrete gravity dam based on the deformations of multi-measuring points. A dam’s comprehensive deformation displacement is determined by the measured values at different measuring points on the positive inverted vertical line and the corresponding weight of each measuring point. The projection pursuit method (PPM) combined with the grey wolf optimization (GWO) algorithm is used to determine the weight of each measuring point according to the spatial correlation distribution characteristics of dam deformation. The peaks over threshold (POT) model based on the extreme value theory is adopted to determine the monitoring control value with the obtained dam comprehensive deformation displacement. In addition, the POT model is improved with the automatic threshold determination method based on the 3σ criterion in probability theory and the GWO algorithm, which can avoid subjectivity and randomness in determining the threshold. The results of the engineering application show the feasibility and applicability of the proposed method. [ABSTRACT FROM AUTHOR]

Earth dams remain the most used means of water mobilization in Algeria, due to their lower cost compared to concrete gravity dams and their capacity to resist better to seismic excitations. A study of the hydraulic structure was carried out in this paper, according to simple rules and empirical approaches. During the last decade, several high earth dams have suffered significant failures of the upstream or downstream slopes at the end of construction, after the initial impoundment, and under seismic loads. To prevent this occurrence or to minimize the damage in these hydraulic structures, a reexamination of the earth dams' behavior using more elaborate calculation methods is necessary. The purpose of the current study is to numerically model the behavior and analyze the stability of earth dams in terms of displacements at the end of construction, after the initial impoundment, during an earthquake, and compare these displacements with those measured in situ. A case study was conducted for the Taksebt - Tizi Ouzou dam by using the Plaxis 2D calculation code and the finite element method. The comparison of the obtained results shows a close concordance with the monitoring results of the dam carried out by various specialized organizations. [ABSTRACT FROM AUTHOR]

This study numerically predicts the failure scenario of a cracked concrete gravity dam caused by water–crack interaction when an overflow occurs due to a reservoir inflow flood. The mixed-mode linear elastic fracture mechanic (LEFM), utilizing the extended finite-element method (XFEM), is employed to simulate the structure. The modified J-integral is used to consider the body forces and water pressure inside the crack. Hydraulic fracture (HF) is effectively modeled using the cubic law and the continuity equation. It is understood that water–crack interaction magnifies the share of mode-I and consequently changes the failure scenario from a ductile mixed-mode manner to a brittle mode-I or a mixed-mode depending on the initial crack level in the case of Koyna Dam with a full fixed base. It is shown that the catastrophic static failure risk of the Koyna Dam increases significantly when the initial crack level moves from 15 to 0 m above the dam base, which leads to a minimum safety freeboard requirement when the crack level is below a critical value. It indicates that an initial crack with a length between 1 and 1.9 m at lower submerged levels might trigger instability for the whole dam body even when the reservoir level is below the dam crest. When the initial crack length increases from 1 to 1.9 m, this critical value, which occurs at low-level cracks, and the maximum overflow, which occurs at intermediate-level cracks, varies from about 4.8–8.6 m and 27.5–30.5 m above the dam base, respectively. [ABSTRACT FROM AUTHOR]

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Deformation monitoring is an important aspect of safety control for concrete dams. Deformation monitoring models (such as statistical models and hybrid models) are extensively applied to predict concrete dam deformation and derive confidence interval of normal deformation for anomaly detection. Deformation monitoring models for concrete dams mainly consist of hydrostatic component, temperature component, and aging component. The optimum parameters of individual components are simultaneously determined by least square method for monitoring data fitting. Thus, significant over-fitting of deformation monitoring models may be induced by mutual compensation among the parameters of model components. In this paper, the Separate Modeling Technique (SMT) is proposed for mitigating the over-fitting problem of deformation monitoring models for concrete dams. Firstly, the Empirical Mode Decomposition (EMD) is adopted to extract and visualize the aging component of displacement sequence. Proper mathematical formulation of the aging component can be established, and the problem of improperly presupposing the mathematical form of aging component in the process of constructing traditional deformation monitoring models is well addressed. In this study, the hydrostatic component is represented by the Hybrid Response Surface (HRS), which is formulated using numerical simulation with varying water levels and material parameters. The displacement variation caused by water level fluctuation is identified in terms of isothermal conditions and is used to calibrate the material parameters in the HRS. The temperature component is separated through subtracting the hydrostatic and aging components from displacement time series and then is expressed with proper mathematical formulations. Finally, hybrid models for displacement monitoring of concrete dams are established by combining the separately formulated components. The Separate modeling technique is applied to formulate crest displacement of the YL concrete gravity dam. The false alarm rate of displacement monitoring and a new model selection criterion (namely over-fitting coefficient) are adopted to compare various deformation monitoring models. It is shown that the over-fitting levels of deformation monitoring models can be effectively reduced using the SMT. The deformation monitoring models constructed with the SMT are of better accuracy in displacement prediction and present no false alarm of displacement monitoring for the tested period. [ABSTRACT FROM AUTHOR]

Purpose: For gravity dams built on foundations with directional joint sets, the seepage in the foundation possesses anisotropic characteristics and may have adverse effects on the foundation stability. A methodology for system reliability analysis of gravity dam foundations considering anisotropic seepage and multiple sliding surfaces is proposed in this paper. Design/methodology/approach: Anisotropic seepages in dam foundations are simulated using finite element method (FEM) with the equivalent continuum model (ECM), and their effect on dam foundation stability is involved by uplift pressures acting on the potential sliding surfaces. The system failure probability of the dam foundation is efficiently estimated using Monte Carlo method (MCM) combined with response surface method (RSM). Findings: The case study shows that it is necessary to consider the possibly adverse effect of anisotropic seepage on foundation stability of gravity dams and the deterministic analysis of the foundation stability may be misleading. The system reliability analysis of the dam foundation is justified, as the uncertainties in shear strength parameters of the foundation rocks and joint sets as well as aperture, connectivity and spacing of the joint sets are quantified and the system effect of the multiple potential sliding surfaces on the foundation reliability is reasonably considered. Originality/value: (1) A methodology is proposed for efficient system reliability analysis of foundation stability of gravity dams considering anisotropic seepage and multiple sliding surfaces (2) The influence of anisotropic seepage on the stability of gravity dam foundation is revealed (3) The influence of estimation errors of RSMs on the system reliability assessment of dam foundation is investigated. [ABSTRACT FROM AUTHOR]

• Combined damage effects of shock wave and bubble on a concrete gravity dam are studied. • The shock wave causes a first attack, inducing tensile cracks in the vulnerable part of the dam. • The bubble pulse generates a secondary attack, facilitating the development of the tensile crack. • The bubble jet and bubble collapse, united with the upstream reservoir water, accelerate the failure of the cracked dam, forming a breach in the dam's upper part. • The shock wave is the key trigger for dam failure, while the bubble accelerates the process of failure. The underwater explosion bubble accounts for half of the total explosive energy and has been found to induce serious structural damage to ship structures. However, the existing research has commonly ignored the damage effect of an underwater explosion bubble on a concrete gravity dam. The current study aims to narrow this gap through high-fidelity numerical simulations and scale model tests. A fully-coupled numerical model is established first and is validated by small-scale centrifugal model tests. The bubble dynamics of underwater explosions near the perpendicular dam structure have been explored. The main focus is then on the sequential damage effects of the underwater explosion shock wave, bubble pulse, bubble jet, and bubble collapse on a concrete gravity dam. It is found that the shock wave causes a first attack, inducing tensile cracks in the vulnerable part of the dam. Subsequently, the bubble pulse generates a secondary attack, facilitating the penetration of the tensile crack throughout the entire dam structure. Additionally, the bubble jet driving the high-speed fluid flow and the bubble collapse causing the uplifted free water surface, united with the upstream reservoir water with huge hydrostatic pressure, largely accelerate the fracture of the dam, then facilitate the fractured dam to fall downstream leaving a breach with certain widths in the dam's upper part, and finally speed up the discharge of the upstream reservoir water through the breach. It also finds that the underwater explosion bubble can generate no new cracks in the gravity dam, even in the pre-damaged area as long as there are no obvious pre-cracks by the shock wave. That is, the shock wave is the key trigger for dam failure, without which the dam failure will not happen, while the bubble, united with the upstream reservoir water, accelerates the process of dam failure. [ABSTRACT FROM AUTHOR]

This paper proposes a progressive approach to assess the properties of large-scale roughness at dam–rock interfaces and the implementation of their effects into practical dam stability analyses. The analysis steps, ranked per increasing degree of complexity, consist of studying a gravity dam monolith using, first, the gravity method (GM), second, the finite element (FE) method (FEM) with a simplified horizontal planar dam–rock interface, and, third, the FEM with a detailed irregular geometry of the dam–rock interface. In the first two steps, the simplification of the rock foundation geometry is paired with the implementation of apparent cohesion and friction angle into the models. These apparent parameters are evaluated based on nonlinear shear strength criteria combined with an interface roughness coefficient (IRC) introduced to characterize the roughness of a dam–rock joint extending along the whole dam footprint. This coefficient is approximated herein numerically based on FE models. The inputs and steps of the progressive approach are illustrated through several examples of typical dam–rock systems and rock profiles based on bathymetric and LiDAR surveys. The results mainly show that the effects of rock foundation roughness on dam sliding stability can be efficiently represented with apparent cohesion and friction angles. The effectiveness of the simplified models coupled with the conservatism of the results they provide are likely to favor their adoption by practicing engineers. [ABSTRACT FROM AUTHOR]

The mathematical formulation of the problem describing the interaction between a dam and the reservoir during earthquakes is complex, and the solution requires the implementation of sophisticated numerical tools. The discussers claim that the transient FE analysis of a dam-reservoir system may not lead to a unique solution depending on the time integration method and the user-defined solution parameters. Impact of Dam Shape In the original paper, the authors only used a single dam shape (including five different heights) with the downstream slope of approximately 0.75 and the chimney width equal to 10% of the dam height. In the original paper, the authors incorporated three additional factors into the approximate Westergaard formulation through a set of multipliers: (1) the dam height, (2) the concrete elasticity, and (3) the reservoir bottom wave absorption. [Extracted from the article]

The concrete dam displacement monitoring model is an essential part of dam health. Due to the complicated nonlinear mapping relationship between concrete dam displacement and various environmental quantities, as well as conventional statistical models, neural networks, and machine learning methods fail to consider each input's fuzzy uncertainty factors. Therefore, the model's prediction accuracy is usually affected by selecting impact factors and modeling methods. This paper uses the Copula theory to perform nonlinear correlation tests on displacement influencing factors for the above problems. Furthermore, on this basis, this paper proposes a hybrid model, which uses an adaptive neuro-fuzzy inference system (ANFIS) to establish a regression model and uses the particle swarm optimization (PSO) algorithm to find the optimal parameters of the model. This paper takes a roller-compacted concrete gravity dam as an example. It explores the effect of two clustering methods (subtractive clustering and fuzzy C-means clustering) on the ANFIS model's performance based on the dam's measured data. The results show that the MAPE in the subtractive clustering is about 26% less than the fuzzy C-means clustering in the test stage. Finally, this paper compares the prediction results of the Copula-ANFIS-PSO model with the other five conventional methods. The analysis of the results of six models with four error indicators shows that the error in the Copula-ANFIS-PSO model is about 46% less than other models. It provides a new method for concrete dam displacement monitoring. [ABSTRACT FROM AUTHOR]

The stability with enough safety margin is one of basic requirements for design and operation of gravity dam engineering. The pre-stressed cable reinforcement is an effective way to enhance and ensure the sliding stability of gravity dam. In this paper, the sliding failure process of gravity dam before and after the pre-stressed cable-based reinforcement practice is simulated and analyzed based on the finite element method (FEM), and two criteria on strength and energy are investigated and integrated to evaluate the improvement effect of reinforcement measures on the stability of gravity dams. Considering the relationship between the strength loss and the overall failure of gravity dam system, a new strength reduction method is investigated to formulate the reduction coefficient for the stability of gravity dams. According to the energy evolution process of the dam system, an energy catastrophe model is built to determine the strength loss coefficient and the strain energy for of gravity dams. Based on the catastrophe theory, the strength loss coefficient as the control criterion and the strain energy as the state criterion are combined to evaluate the stability improvement of gravity dams undergoing pre-stressed cable reinforcement. A gravity dam taken as an example, the proposed bi-criteria approach for stability evaluation of gravity dams with pre-stressed cable reinforcement is verified. [ABSTRACT FROM AUTHOR]

As an important long-term task in the field of dam engineering, the maintenance and reinforcement (MAR) are of great significance for ensuring the safety of the project and prolonging the service period of the project. The MAR of large-scale and long-term projects also requires high costs. In order to reduce the consumption of funds and improve the utilisation of resources, the whole life cycle cost (LCC) method is introduced. Aiming at the lowest total cost in the whole life cycle, the optimisation of dam engineering planning, design and MAR is carried out. Taking gravity dam as an example, this article establishes a time-varying model of structural resistance and load effect, and the deterioration process of the gravity dam has been analysed and predicted. A decision model for design and reinforcement of gravity dams considering operational risk and LCC is established. Through the optimisation algorithm, the optimal initial design of the gravity dam and its optimal MAR plan is obtained. [ABSTRACT FROM AUTHOR]

Debris flows endanger humans living and property in mountainous regions all over the world, so it must be prevented and controlled by engineering. It is one of the quick and effective measures to build gravity check dam in the gorge from the formation area to the circulation area. Check dam often plays a controlling role in debris flow control. Check dam controls the development of debris flow, reduce the scale and frequency of debris flow. The consequences of the instability and destruction of check dam are extremely serious. However, debris flow hazard poses a great threat to check dam, especially the impact of debris flow on check dam is often the important cause of its stability damage. Accurately calculating the impact pressure and impact velocity of debris flow on check dam is a key scientific problem to be solved in the field of debris flow engineering prevention. Taking the drainage channel slope, the check dam slope ratio and the debris flow density (the clear water impact as the comparison experiment) as the experimental variables, eight pressure sensors are arranged at different positions on the upstream surface of the check dam to receive the debris flow impact signal, and the high-speed continuous data acquisition is adopted. The impact signal is collected and transformed by the instrument and the acquisition system. The time history curve of the impact pressure of the debris flow on the upstream surface of the check dam is obtained. The distribution of average velocity of debris flow along the vertical and lateral directions of the check dam is studied under different drainage channel slopes, different debris flow densities, and different check dam slope ratios. The results show that (1) at the same position on the upstream surface of the check dam, the average value of the debris flow velocity nonlinearly increases with the slope of the drainage channel, the slope ratio of the check dam, and the debris flow density increasing. (2) The average flow velocity of the debris flow decreases along the lateral direction of the check dam from the overflow section to the dam shoulder. (3)The debris flow average velocity directly affected is greater than the top position along the height direction of the check dam. The study results are of great significance for providing data and technical support for the structural design of the check dam. [ABSTRACT FROM AUTHOR]

Dam concrete exhibits inhomogeneity due to its inherent material characteristic, construction-induced cracks/defects, and aging deterioration. The inhomogeneity may affect earthquake performance and seismic safety of concrete dams. In this work, a gravity dam-reservoir-foundation model, involving radiation damping, compressibility of reservoir water, and damage/cracking of concrete, is presented to investigate the influence of concrete inhomogeneity on seismic behavior of dams. The Weibull probabilistic distribution assumption is employed in the model to describe the heterogeneity of the dam concrete. A series of numerical analyses of the Koyna gravity dam, which is assigned with different heterogeneity indexes, is performed. The result demonstrates that the heterogeneity of concrete has significant influence on the seismic damage behavior of concrete gravity dams. A more heterogeneous material generally results in a larger dynamic displacement, a more severe damage pattern, and a greater damage level of the dam, indicating that an increase in homogeneity of concrete would be of benefit to seismic capability of concrete gravity dams. [ABSTRACT FROM AUTHOR]

Engineering geological and geotechnical assessment of the dam foundation are essential for the design of the dam to ensure safety. At the southeastern part of Karnataka, Yaragol gravity dam is being constructed, which is designed based on site geomorphological and geological conditions and economic reasons. This paper discusses the results of the engineering geological and geotechnical investigations that have been carried out at the foundation levels of the dam. The dam foundation is composed of foliated gneiss and granite gneiss belonging to Archean to Paleoproterozoic age with intrusive dykes. This study is based on field and laboratory investigations, surface discontinuity mapping, drilled borehole data and in-situ shear testing. In-situ shear parameters of rock-rock interfaces and concrete-rock interfaces were conducted for the evaluation of dam stability against sliding. The classification and rock mass quality of the dam site is assigned using the rock mass rating (RMR) for all the 19 blocks and allowable bearing pressure (qallow) is assessed based on rock types and RMR. At all the blocks foundation, geological defects were mapped and analyzed and treated with suitable engineering measures. Based on structural features mapped, curtain grouting and consolidation grouting is recommended. [ABSTRACT FROM AUTHOR]

The use of non-invasive investigation methods is becoming frequent as a support for the monitoring of water reservoirs and for the management of dam safety. In this context, geophysical techniques are much less invasive than geotechnical tests and allow to obtain two-dimensional or three-dimensional representations of the mechanical parameters of an engineering structure. A case of application of constrained inversion and joint interpretations of non-invasive seismic techniques is discussed, in order to monitor the Dirillo gravity concrete dam, in Sicily. To investigate the foundation soil, a stratigraphic borehole and a vertical seismic profile, carried out in the same hole, were used to constrain the inversion of a MASW. This latter allowed to generate the starting model for a seismic refraction tomography. The results of the seismic surveys on the ground surrounding the dam allowed a detailed seismic characterisation the foundation soil. Furthermore, for the characterisation of the concrete of the dam, a vertical seismic profile was acquired, using a vertical inspection duct in the dam body, and three seismic refraction tomographies were performed placing sources and receivers on the two opposite walls of the dam. Also in this case the tomographic inversions were constrained by the P wave velocity values obtained from the vertical seismic profile. 2D representations of P wave velocity and the trend with depth of S wave velocity and Poisson ratio allowed an accurate reconstruction of the state of the concrete conservation of the dam. The high velocity values of the P and S waves, together with normal values of the Poisson ratio, suggest that the concrete is still of good quality and local decreases in the P wave velocity are due to moisture and infiltrations. The results obtained confirm the efficacy of seismic refraction tomography, if appropriately constrained, for the characterisation and validation of concrete in large-scale infrastructures that are difficultly investigable using direct methods. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Dams are generally designed and built to resist the most severe destabilizing conditions. Their failures have caused severe damages and loss of lives through history. The investigations carried out on failed dams have, in most cases, unveiled that foundation problems are usually the cause. These problems are very often related to the condition of discontinuities dissecting the rock foundations. Being weak, they are the preferred planes for deformation and rupture causing the collapse of the whole structure. This study deals with the rock mass properties and their suitability as rock foundation for Beni Haroun dam, the largest dam in Algeria. The dam is located in the north-eastern part of Algeria on Wadi El-Kebeir, approximately 40 km from its outfall in the Mediterranean Sea. The dam is a roller-compacted concrete type with a height of 120 m, a crest length of 710 m, and a water storage capacity of approximately 1 billion m3. The dam is founded on Ypresian limestone rock mass. The present study was carried out both in the field and in a laboratory. The field study included geological mapping of the engineering, an intensive discontinuity survey, and sampling. Laboratory tests were conducted to determine shear strength, uniaxial compressive strength, tensile strengths, and Young's modulus of rock samples. The shear strength of discontinuity was evaluated according to the criterion developed by Barton and Choubey. The joint roughness coefficient was calculated through a statistical approach using the parameter Z2, and an empirical approach based on a visual comparison with standard profiles of the Barton–Choubey roughness. The quality of the rock mass was estimated using Rock Mass Rating (RMR) and Geological Strength Index (GSI) systems. The stability of the dam foundation was assessed using the DMR system and the Hoek and Brown failure criteria. The rock mass of the dam foundation is the Ypresian limestone formation and is of fair quality. This study has shown that this rock mass is adequate as foundation for Beni Haroun RCC dam. [ABSTRACT FROM AUTHOR]

To study the uniqueness of a multi-parameter inverse analysis of a concrete gravity dam, the present method establishes herein an objective function based on a theoretical solution of the displacement of a gravity dam on a homogeneous foundation, with the dam subjected to water pressure. From this objective function and a non-empty convex set, a convex-programming problem is constructed. To determine whether the objective function is a strictly convex function, whether or not the Hesse matrix of the objective function is positive definite is considered, which could determine whether the constructed convex-programming problem has a unique global minimum. An analysis of various combinations of elastic constants for the dam and rock foundation shows that when the l1 norm of the difference between the theoretical value and the measured value is used as the objective function, the Hesse matrix is not guaranteed to be positive definite, so the multi-parameter elastic-displacement inverse analysis of the concrete gravity dam gives no unique global minimum. [ABSTRACT FROM AUTHOR]

The durability of dam concrete is considerably affected by environmental effects. Although great progress was achieved on environment-induced deterioration mechanism of concrete, there still seems that a gap exists between researches of the concrete durability in natural and standardised laboratory conditions. This article is concerned with carbonisation and calcium leaching-induced deterioration of concrete in dams in service. Field inspections and analyses of dozens of investigated dams in China are presented. The results show that the carbonation speed is closely related to the age of construction and its location. The carbonisation depth of the upstream surface is generally smaller than that of the downstream surface for the same dam. The calcium leaching degree of dam concrete is affected by several factors, such as reservoir water chemistry, type, height, construction age and quality of the dam. Calcium leaching of dam concrete is common in China because the reservoir water is usually soft and has medium soluble corrosivity. These deteriorating processes and characteristics are consistent with the previous laboratory results. A masonry gravity dam due to 17 years of exposure to natural environment was taken as a case study on concrete alteration mechanisms. Concrete cylinders drilled out at four vertically different locations on the upstream concrete-faced slab were analysed by compressive strength test and mercury intrusion porosimetry test. The deterioration process controlling the concrete near the waterline varies according to its location, resulting in the variation of micropore structures at various depths from the upstream surface. Long-term exposure to natural environment has led to chemical and mineralogical zonation of the concrete. The results of this study can be used to compare the similar results from the short-term laboratory investigations. [ABSTRACT FROM AUTHOR]

In order to reduce the damage of ordinary gravity dam impacted by boulders in debris flow, a blocks-combined dam based practical project is proposed. The dynamic response of the proposed dam under impact load is investigated by using ABAQUS finite element software. Considering the impact velocity and impact height, the anti-impact performance of blocks-combined dam is discussed in terms of deformation, displacement, impact force, acceleration, and energy, and is compared with that of ordinary dam. Results show that the displacement, impact force and acceleration of dam increase with the increase of impact velocity and height. The impact energy of blocks-combined dam is mainly absorbed and consumed by the friction between the component interfaces, which is related to the location of impact point. Compared with the ordinary gravity dam, the blocks-combined dam has better impact resistance to boulders in debris flow. [ABSTRACT FROM AUTHOR]

It is important to determine the warning value of structural behavior for evaluating the service safety, identifying the potential risk and preventing the failure of dam engineering. However, more attention was paid to determining the security warning value of a single observation point on deformation, seepage or stress. And the correlation between the adjacent points or among all points in one dam section is usually lack of consideration. In this paper, the monitoring data of multi-points are taken to determine the spatial warning domain of dam safety. The warning mode of abnormal structural behavior is changed from the single point into the linked multi-points. First, the kernel principal component analysis method is adopted to identify the inherent characteristics among observation points in a dam section. Second, considering the correlation among observation points, the implementation process is proposed to determine the spatial warning domain of dam safety. Finally, an actual concrete gravity dam is taken as an example. The proposed approach is used to determine the spatial warning domains of deformation and seepage. The results, which are obtained by the proposed approach, the traditional method and the qualitative analysis for monitoring data, are compared. It is indicated that the proposed multi-points correlation-based approach is feasible and superior to determine the spatial warning domain of dam safety. [ABSTRACT FROM AUTHOR]

Statistical models have been used for dam health monitoring for many years and have achieved some successful applications. In the statistical model, dam structural response is related to external environmental factors such as reservoir water level, temperature, and irreversible time deformation. For concrete dams, the structural response is affected greatly by the ambient temperature. Therefore, in order to establish a more reliable dam health monitoring model, the temperature effect and modeling method should be further studied. This article presents a dam health monitoring model using measured air temperature for temperature effect simulation based on kernel extreme learning machines. The temperature effect is simulated by long-term air temperature data, and the nonlinear relationship is modeled by kernel extreme learning machines, which is an intelligent machine learning technique with high learning speed and good generalization performance. The proposed dam health monitoring model is verified on a real concrete gravity dam with efficient safety monitoring data. Results show that the proposed approach with a variable set recommended for concrete dam behavior prediction is feasible. [ABSTRACT FROM AUTHOR]

Seismic damages that occurred by the effects of epicenter distance of the earthquake are one of the most important problems for the earthquake engineering. In this study, it is aimed to examine the nonlinear seismic behaviors of concrete gravity (CG) dams considering various epicenter distances. For this purpose, Boyabat CG dam that is one of the biggest concrete gravity dams in Turkey is selected as a numerical application. FLAC3D software based on finite difference method is used for modelling and analyzing of the dam. Drucker-Prager nonlinear material model is used for the concrete body and Mohr-Coulomb nonlinear material model is taken into account for the foundation. Special interface elements are used between dam body and foundation to represent interaction condition. Free-field and quiet non-reflecting boundary conditions are utilized for the main surfaces of 3D model. Total 5 various epicenter distances of 1989 Loma Prieta earthquake are considered in 3D earthquake analyses and these distances are 5 km, 11 km, 24 km, 85 km and 93 km, respectively. According to 3D seismic results, x-y-z displacements, principal stresses and shear strain failures of the dam are evaluated in detail. It is clearly seen from this study that the nonlinear seismic behaviors of the CG dams change depending to epicenter distance of the earthquake. Thus, it is clearly recommended in this study that when a CG dam is modelled or analyzed, distance of the earthquake fault to the dam should be strongly examined in detail. Otherwise, earthquake damages can be occurred in the concrete dam body by the effects of seismic loads. [ABSTRACT FROM AUTHOR]

Crest length is an important parameter in influencing the discharge handling capacity of a weir. Nonlinear weirs with longer crests are cost effective alternatives for those existing dam structures which are more susceptible to failure due to loss of storage capacity by reservoir silting problem, and insufficiency of the structure in evacuating the updated flow due to the limited space. Piano key weir is a type of nonlinear weir designed in the form of piano keys, over-hanged from both the upstream and the downstream with sloping floors founded on a base or footprint. These weirs can be easily placed over gravity dams due to smaller footprint than labyrinth weirs. The present study's focus is on the comparative analysis of identical configurations of trapezoidal and rectangular piano key (PK) weirs. The importance of (crest length to width) L/W ratio and weir height (P) in affecting the discharge efficiency of both types of PK weirs is investigated in the experimental study. Furthermore, soft computing approaches are applied to the current data set obtained from both types of weirs by considering discharge coefficient ( C d ) as a function of dimensionless geometric variables of PK weirs. The modelling performance of random forest regression and M5 tree approach is tested in order to estimate the values of discharge coefficient. The results conclude higher predictive accuracy of random forest model over M5 tree model. [ABSTRACT FROM AUTHOR]

This paper presents a dam health monitoring model using long-term air temperature based on multivariate adaptive regression splines (MARS). MARS is an intelligent machine learning technique that has been successfully applied to deal with nonlinear function approximation and complex regression problems. The proposed long-term air temperature-based dam health monitoring model was verified on a real concrete gravity dam with efficient safety monitoring data. Results show that the proposed approach is promising for concrete dam behavior modeling considering the prediction error is much reduced. [ABSTRACT FROM AUTHOR]

• Seismic damage degree of concrete gravity dam is evaluated by damage volume ratio. • The feasibility of PZT sensors in monitoring the dam damage degree is investigated. • Normalized RMSD index is proposed to quantify the severity of dam damage. • Two kinds of damage indices are discussed to evaluate the dam safety. A rare but remarkable accident is the dam failure due to earthquake that can trigger catastrophes on economic and life losses. It is essential to monitor the presence and development of seismic damage of dam structures in the early stage of emergence of damage and take steps to prevent the full structural failure. In this research, only seismic damage and dynamic performances of a roller compacted concrete (RCC) dam were investigated using an electromechanical impedance (EMI)–based structural health monitoring (SHM) technique enabled by lead-zirconate-titanate (PZT) ceramic sensors network. The finite element model of the PZT sensor and damage monitoring method were verified by comparing the scanning conductance signals obtained from the experimental tests. A quasi 3D finite element model of the RCC dam using concrete damaged plasticity (CDP) constitutive model was built and assumed to be subjected to different degrees of earthquake excitations to initiate the dam damage due to tension. The conductance signals were measured by the PZT sensors network which are excited by inputting unit harmonic voltage. In addition, the normalized root-mean-square deviation (RMSD) was used as a damage index to quantify and evaluate the variations in conductance signals measured at the PZT sensors. Furthermore, two damage indices, namely the RMSD based damage volume ratio (DVR) and RMSD based displacement, were proposed to predict the damage levels and maximum horizontal displacement at the crest of dam under seismic loading. It is clearly demonstrated that the EMI technique based PZT sensors network can keenly detect the seismic damage of dam and the proposed damage indices can effectively quantify the damage levels and predict the dynamic response performances. [ABSTRACT FROM AUTHOR]

By rapidly increasing the production of energy and widely extending the usage of electricity in the 20th century, hydroelectric plants and dams have radically affected the social, technological and industrial aspects of the period. Therefore, as an integral part of industrial heritage, the cultural assets of these energy facilities are required to be preserved. As a requirement of this hypothesis, it is necessary: to develop management strategies for these assets; to provide scientific data and information on these buildings / facilities; to define criteria of 'planned conservation' with long-term preventive measures in order to provide the continuation of the original function as long as possible. Hydroelectric plants are a common subject of interest for several disciplines, such as: engineering, hydrology, ecology, geo-sciences and remote sensing. Therefore, the conservation of the plants also requires the interdisciplinary study and collaboration of these disciplines.Within the study, the considerations of an interdisciplinary approach – such as dam safety, ecological concerns and energy requirements – are presented, and examples from different countries are examined through the framework of architectural conservation, considering cases of dam failures, intended removal of dams and upgrading of facilities. Preventive measures for the planned conservation of hydro electrical facilities such as: constant maintenance of technical components; management of the sediment accumulated in the reservoirs; methods of analysis for the structure of the embankment are introduced briefly, concentrating on gravity dams, in order to provide conclusions for the conservation of Sarıyar Dam and Hydroelectric Plant (1956) in Turkey. [ABSTRACT FROM AUTHOR]

The effects of geometric configuration on the seismic vulnerability of concrete gravity dam are discussed in the present study. The seismic vulnerability of concrete gravity dams has been represented through fragility curves obtained through incremental dynamic analyses by considering their nonlinear dynamic behavior. Five different geometries of concrete gravity dams are considered and fragility analyses are carried out on the basis of Incremental Dynamic Analyses. The effect of smoothening of re-entrant corners in the geometry of high concrete gravity dam is also presented as a possible solution. [ABSTRACT FROM AUTHOR]

Concrete structures with varying sections are widely used in the fields of ocean engineering, hydraulic engineering and civil engineering. And the damage mechanism of variable-section structures to underwater contact explosion, which involves localized damage by explosion impact and instability by overall structural vibration, is very complex. The gravity dam is taken as an example, the coupled analysis model for gravity dams under underwater contact blast is established, a prototype test on the dynamic response of a gravity dam under underwater explosion is conducted to verify the reliability of the fluid-solid interaction method, and the reliability of the concrete dynamic damage model adopted in this paper is validated by a small-scale field test on the internal blast damage of a gravity dam. The damage mechanism of gravity dams subjected to underwater contact explosion is analyzed. A stability analysis method for gravity dams to underwater contact explosion is proposed, which allows simultaneous consideration of the dam stability in the blast-induced vibration phase and the static phase after damage. The dynamic stability performance of gravity dams to underwater contact explosion is analyzed. And a stability assessment criterion that could be used to assess the safety level of dams at various stages is presented. • Prototype test and small-scale test on blast-induced response of dam are conducted. • Validation of fluid-solid coupled method based on prototype and small-scale tests. • Dynamic stability analysis method for concrete structures to underwater explosion. • Dynamic stability performance of concrete structures to underwater explosion. [ABSTRACT FROM AUTHOR]

Uplift forces along foundation joints or improperly bonded concrete joints are a widely recognized contributor to failure modes for concrete gravity dams. The industry-wide inclusion of uplift forces in the design and evaluation of concrete dams was predated by several dam failures (e.g., Bouzey Dam, Austin Dam, St. Francis Dam) that can be at least partially attributed to a lack of understanding of these forces. This paper provides a summary of the current state-of-the-practice in application of uplift forces on concrete dams and a summary of a panel discussion held at the 2016 national conference of the Association of State Dam Safety Officials (ASDSO). The summary includes the most recent federal guidelines and standards used in design and evaluation of concrete dams, including Federal Energy Regulatory Commission (FERC), Bureau of Reclamation (Reclamation), and U.S. Army Corps of Engineers (USACE) guidelines. The panel discussion section summarizes the discussions at the ASDSO conference including audience questions and the panelists' responses. Particular attention is given to clarifying application of uplift pressures for concrete dams with foundation and body drains, and to methods for adjusting uplift pressures for flood, earthquake, and post-earthquake loading, as well as cracked base analysis. [ABSTRACT FROM AUTHOR]

Part I of this work indicates that the dimensional analysis-based scaling law fails to scale the dynamic tensile responses and failures of concrete gravity dams subjected to underwater explosions owning to the dissimilar strain-rate effects between small-scale dam models and prototypes. In Part II of this work, a correction method is proposed to address this challenge based on a dimensionless damage number D ni suggested in Part I of this work. The core idea is to keep D ni equal for small-scale dam models and prototypes by adjusting the other terms of D ni according to the differences in the strain-rate effects between small-scale dam models and prototypes. Detailed scaling procedure with the correction method using a small-scale dam model as a reference is given, where both the explosive weight and the static tensile strength of the concrete gravity dam of the prototype need to be corrected. For validation purposes, the fully-coupled numerical model established based on centrifuge tests in Part I of this work is still employed. Geometrically similar dam models with geometrical scaling factors β = 1, 1/2, 1/5, 1/10, 1/20, 1/30, 1/40, 1/50, 1/60, 1/70, 1/80, and 1/100 are used. Results demonstrate that the proposed correction method can well address the non-scalability of the strain-rate effect between small-scale dam models and prototypes. With the correction method, the failures of geometrically similar dam models with β = 1–1/100 are almost identical, and D ni exhibits a uniformly linear relation with the dimensionless displacement δ / H of geometrically similar dam models with β = 1–1/100. Besides, the proposed correction method makes it possible to apply the well-known concept of "modeling of models" to verify the scaling relations of concrete gravity dams subjected to underwater explosions in a centrifuge. • Scaling of failure of concrete gravity dam against underwater explosion is studied. • Due to the dissimilar strain-rate effects, failures of small-scale dam model and prototype are disparate. • A correction method is proposed that can address the non-scalability of the strain-rate effect. • The correction method is theoretically derived based on a dimensionless damage number D ni. • With the correction method, failures of β = 1–1/100 dam models are almost identical. [ABSTRACT FROM AUTHOR]

• The zero-thickness cohesive element model is used to simulate the RCC layers. • Failure modes of a RCC dam subjected to underwater contact explosion are obtained. • Effects of the properties of RCC layers on the dam's blast responses are studied. Considering the construction technology of roller compacted concrete (RCC) gravity dams, there are layers in dams inevitably, which may affect the blast responses of dams. This paper is aimed to investigate the effects of RCC layers on the failure modes and dynamic responses of RCC gravity dams bearing underwater contact explosion loading. Initially, the zero-thickness cohesive element model is presented to simulate the crack behavior of the RCC layers. An impact test of a concrete beam is selected to verify its reliability. The concrete damage plasticity model considering strain rate effects is utilized to simulate the various responses of concrete under blast load. The dam–reservoir–foundation interactions are described using the coupled Eulerian-Lagrangian method. The numerical methods are validated by a field blast test of a concrete structure. Subsequently, numerical models were established for gravity dam-reservoir-foundation systems, with and without considering RCC layers respectively. Based on validated algorithms, these models were utilized to explore the effects of RCC layers on the blast performance of the dam. Finally, the influence of the parameters of RCC layers on the nonlinear responses and failure modes of the dam is further investigated, including the maximum traction, the fracture energy, and the layer thickness. The results reveal that the layers significantly change the failure modes. The RCC layers are the weak link of the dam and they will lower the anti-explosion performance of the dam. Therefore, it is crucial to take the layers into account when conducting anti-explosion research, and RCC dams cannot be simply simplified as normal concrete dams. To guarantee the safety of the dam, it is important to ensure the layers with sufficient strength and fracture energy, as well as an appropriate thickness. [ABSTRACT FROM AUTHOR]

The small-scale model test is the major feasible approach to experimentally investigate concrete gravity dams subjected to underwater explosions. However, speculating results of the dam prototype requires knowledge of scaling law. Our previous research finds that the dimensional analysis-based scaling law is violated since the strain-rate effects between small-scale dam models and prototypes are dissimilar, resulting in distinct tensile failures between them. The non-scalability of the strain-rate effect is one of the most troublesome issues in similarity analysis, plaguing the research community for years. This two-part paper attempts to address this challenge by proposing a correction method to the dimensional analysis-based scaling law for scaling the failure of concrete gravity dams subjected to underwater explosions. The strategy contains two steps. The first step is to derive dimensionless damage numbers through the dimensional analysis method. The second step is then to propose the correction method based on the verified dimensionless damage number. Part I of this work deals with the first step, while Part II addresses the second step. In Part I of this work, a dimensionless damage number is suggested to reflect the dynamic bending-induced tensile response mechanism of concrete gravity dams against underwater explosions. Three aspects can be reflected in this dimensionless damage number: the inertia force of the loading, the resistance ability of the material to deformation, and the resistance ability of the dam structure to deformation. For validation, a numerical scheme comprising 12 geometrically similar dam models with geometrical scaling factors β = 1, 1/2, 1/5, 1/10, 1/20, 1/30, 1/40, 1/50, 1/60, 1/70, 1/80, and 1/100 is devised based on small-scale centrifuge tests. Results have demonstrated that when strain-rate effects are close, such as for β = 1/40–1/100 dam models, the suggested dimensionless damage number can well predict the dam dynamic responses and failures, and shows an excellent linear relation with the dam dimensionless displacement. However, when strain-rate effects are dissimilar, such as for β = 1–1/30 dam models, the suggested dimensionless damage number fails, and correction methods are required that will be proposed in Part II of this work. • Scaling of failure of concrete gravity dam against underwater explosion is studied. • Due to the dissimilar strain-rate effects, failures of small-scale dam model and prototype are disparate. • A correction method is proposed that can address the non-scalability of the strain-rate effect. • The correction method is theoretically derived based on a dimensionless damage number D ni. • With the correction method, failures of β = 1–1/100 dam models are almost identical. [ABSTRACT FROM AUTHOR]

The article presents the discussion on St. Francis Dam failing catastrophically on March 13, 1928. Topics include Mulholland having considerable experience in designing and constructing embankment dams designing one other concrete dam; and California enacted a law requiring professional registration for civil engineers.

This study has presented a method to estimate the damage location in the concrete gravity dam monolith. The first four vibration mode of the highest monolith of the Koyna dam was estimated and analyzed by the combined discrete and continuous wavelet transform. The position of the damage scenarios was identified by using bior 3.9 wavelet in the spatial variation of the data response. The sensitivity of wavelet to random signal noise was investigated by using noise to displacement response of cracked monolith. Three noise levels were introduced in the model and the capacity of this method to detect damage from noisy data was discussed. [ABSTRACT FROM AUTHOR]

A newly built roller-compacted concrete gravity dam is located on the Yalongjiang River in southwest China. Complex geological conditions greatly puzzled the designers of the project. There are abundant joints within the riverbed that form the double- inclined wedge foundation. This is a typical mode of instability of concrete gravity dams. The equal-K method, which falls into the category of conventional limit-equilibrium methods, is provided in the design codes of gravity dams to evaluate the stability of a dam against sliding along deep failure surfaces. The factor of safety calculated by the equal-K method is determined by the angle of the force acting on the interface of the two inclined wedges, denoted by φ, which is unspecified in the design codes. On the basis of Sarma's assumption, this study proposes an algorithm for the determination of ∅, which needs only slight improvement of the algorithm in the existing codes. The justification of the proposed procedure is demonstrated by showing that the results from the proposed procedure are very close to those from a rigorous limit-equilibrium method in which all equilibrium conditions are satisfied. [ABSTRACT FROM AUTHOR]

• Blast tests are conducted to obtain damage mechanisms and failure modes of the dam. • A CEL method is adopted to describe the dam to penetration explosion. • The effects of main influential factors on the damage ranges are discussed. • A damage prediction method for concrete gravity dams is put forward. The dynamic responses and damage mechanisms of high dams that are subjected to blast loads have become important in recent years. A series of analytical, experimental, and numerical approaches are used to investigate the mechanisms and characteristics of composite damage to concrete gravity dams subjected to penetration explosion. The potential failure modes of the dam resulting from penetration explosion are first analyzed and categorized. Field blast tests are performed to gain the possible damage mechanisms and modes of a small-scale dam model to internal explosion. A fully coupled Eulerian–Lagrangian approach is then adopted and verified through comparisons between the experimental and the numerical results. Following this, detailed numerical simulations and analyses of a typical concrete gravity dam to penetration explosion are presented by using the validated numerical method to examine its dynamic responses and the development of damage in it. Furthermore, the results of damage to the dam in case of different attack locations, explosive equivalents, penetration depths, and critical interfaces are compared. Similarity theory and blasting theory are used to provide a theoretical analysis, and its results are used along with those of numerical simulations to obtain a formula to predict the damage range of the dam. The work here focuses on the dynamic responses and damage mechanisms of dams subjected to penetration explosion, and the authors propose a quantitative and effective method to predict this damage. [ABSTRACT FROM AUTHOR]