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The bearing capacity of large rectangular foundations on soil subjected to combined loading [simultaneously subjected to vertical load (V), overturning moment (M), and horizontal or lateral load (H)] is one of the central topics of interest to geotechnical engineers as it relates to the design of foundations such as ground anchorages of bridges, offshore structures, and gravity dams. To solve this problem, a combination of numerical simulation and theoretical research was used, and a stability evaluation model of large rectangular foundations on soil subjected to combined loading was established. First, an empirical equation for the failure envelope in the V‒M‒H loading space of rectangular foundations was developed. Second, the safety factor for load-path dependency (LPD) was established by considering the combined effects of V, M, and H, the stability evaluation model for large rectangular foundations on soil subjected to combined loading was constructed by proposing a method for calculating the LPD safety factor based on the V‒M‒H failure envelope. Last, the accuracy and effectiveness of the stability evaluation model proposed was verified. The proposed model provides a convenient means of calculating the stability of large rectangular foundations on soil under combined loading. The model was applied to the optimal design of a gravity anchorage project of a suspension bridge, which proves that the proposed model is rational and efficient. [ABSTRACT FROM AUTHOR]

Highlights: A block limit equilibrium analysis method is proposed based on the respective advantages of block theory and three-dimensional rigid limit equilibrium method. This method perfectly explains the continuous transformation from double-plane sliding to single-plane sliding. The proposed method was successfully applied in the anti-slip stability analysis of a gravity dam foundation optimal design. [ABSTRACT FROM AUTHOR]

Dams are among the most important civil engineering structures, but they are also susceptible to damage that can endanger their stability and functionality. It is therefore crucial to detect any damage in dams to ensure their long-term integrity and overall safety. In light of this, the present study proposes a new two-stage method for identifying damage in concrete gravity dams. In the first stage, a modal curvature-based damage index (MCBDI) is presented to detect the location of suspected damaged zones along the height of the dam. The mode shape data collected from some measurement points on the downstream side of the dam is used to accomplish this task. In the second stage, the pathfinder algorithm (PFA) as a powerful meta-heuristic optimization technique is applied to determine the severity of potentially damaged zones by minimizing an objective function specified in terms of natural frequencies and mode shapes. The capability and effectiveness of the proposed method are evaluated by implementing two numerical simulation examples of concrete gravity dams under both noise-free and noisy conditions. The results obtained suggest that the proposed two-stage method, comprising the MCBDI indicator and the PFA algorithm, represents an accurate and efficient approach for localizing and quantifying damage in concrete gravity dams. [ABSTRACT FROM AUTHOR]

Seismic assessment of plain concrete structures like gravity dams is generally conducted based on cracking. The responses of two types of gravity dams, i.e. the conventional and roller compacted concrete (RCC), were investigated in this study using a discrete element tool coupled with special reservoir elements. Using incremental dynamic analysis, the relationship between the seismic intensity measures and crack widths on the U/S face of the monolith was obtained. The damage accumulation on conventional and RCC dams was different: The cumulative cracking on the upstream face of the monolith correlated well to a seismic intensity measure representing base shear. [ABSTRACT FROM AUTHOR]

Investigating the dynamic response patterns and failure modes of concrete gravity dams subjected to strong earthquakes is a pivotal area of research for addressing seismic safety concerns associated with gravity dam structures. Dynamic shaking table testing has proven to be a robust methodology for exploring the dynamic characteristics and failure modes of gravity dams. This paper details the dynamic test conducted on a gravity dam model on a shaking table. The emulation concrete material, featuring high density, low dynamic elastic modulus, and appropriate strength, was meticulously designed and fabricated. Integrating the shaking table conditions with the model material, a comprehensive gravity dam shaking table model test was devised to capture the dynamic response of the model under various dynamic loads. Multiple operational conditions were carefully selected for in-depth analysis. Leveraging the dynamic strain responses, the progression of damage in the gravity dam model under these diverse conditions was thoroughly examined. Subsequently, the recorded acceleration responses were utilized for identifying dynamic characteristic parameters, including the acceleration amplification factor in the time domain, acceleration response spectrum characteristics in the frequency domain, and modal parameters reflecting the inherent characteristics of the structure. To gain a comprehensive understanding, a comparative analysis was performed by aligning the observed damage development with the identified dynamic characteristic parameters, and the sensitivity of these identified parameters to different levels of damage was discussed. The findings of this study not only offer valuable insights for conducting and scrutinizing shaking table experiments on gravity dams but also serve as crucial supporting material for identifying structural dynamic characteristic parameters and validating damage diagnosis methods for gravity dam structures. [ABSTRACT FROM AUTHOR]

A dam is a structure that aids the growth of a country in terms of infrastructure development. For such a magnificent structure design, its stability is vital. The Cheruthoni dam in Kerala, India (gravity dam) was selected for the present study. The reservoir-full condition, hydrostatic pressure, uplift pressure and earthquake pressure forces were chosen for failure analysis by considering seismic coefficient and downstream slope angle as critical parameters. The analysis was done regarding stress and displacement, and the results were interpreted using RS2 software. The results revealed that the downstream slope angle is more critical than the seismic coefficient. [ABSTRACT FROM AUTHOR]

Based on a previous experimental study that we conducted on granite joint replicas including thirty direct shear tests, this article proposes to integrate the joint roughness in the Mohr-Coulomb shear behaviour model (MC). The model integrates joint roughness into constitutive stress-displacement relationships describing mechanical behaviour of rock joint. The shear strength of rock joint is assessed by the MC shear criterion that takes into account the apparent cohesion. This MC model integrating rock joint roughness component is validated against other experimental results from the literature. It is able to accurately predict the peak shear strength of an unbounded rock joint with an average relative error of 7.9%. It is finally used to assess the role of joint roughness on the shear behaviour of a gravity dam foundation. [ABSTRACT FROM AUTHOR]

The current paper's goal is to investigate how dynamic interaction phenomena and material nonlinearities affect the dynamic behavior of a concrete gravity multi-arch dam in terms of maximum displacements, natural stresses, principal stresses, and Von Mises stresses when subjected to seismic excitation. Utilizing ANSYS APDL software, linear and nonlinear transient analysis using the finite element method was employed to analyze the interaction between the dam and its rock foundation. As a case study for this work, the multiarch Beni-Bahdel dam was selected, and the seismic excitation used data from a simulated earthquake. The direct method is employed to model the interaction between the multi arch dam and the rock foundation using two approaches; the fixed base approach and the mass foundation approach. Six finite element models were performed using ANSYS code, "linear dam-fixed support", "nonlinear dam- fixed support", "linear dam-linear rock foundation" "nonlinear dam-linear rock foundation", "nonlinear dam-nonlinear rock foundation" and "linear dam-nonlinear rock foundation". The bilinear kinematic hardening model is employed to represent the nonlinearity of both dam body and rock foundation. The results obtained are compared to understand the effect of both material nonlinearities and interaction phenomenon on the dynamic behavior of the studied dam. In contrast to the nonlinearity of the rock foundation material, it is concluded that the nonlinearity of the concrete dam material has a significant impact on the behavior of the system. [ABSTRACT FROM AUTHOR]

The control of thermal cracks induced by the effect of early age are the main concerns in concrete dam during the construction stage. Despite its importance, detailed thermal analysis of concrete gravity dams during the construction period is relatively rarely in the literature, eventually because prediction the behavior of concrete gravity dam on early stage requires taking into account the several phenomena and interaction, demands a considerable computational effort. To overcome this drawback, the present paper proposes a numerical modeling strategy to predict the thermo-mechanical behavior of concrete gravity dams during construction periods considering the effect of early age and the construction schedule. The proposed strategy is also used to study the effect of precooling methods on the thermal-mechanical fields on concrete gravity dam during construction process. For this purpose, a Chemo- Thermo-Mechanical model is developed for predicting the behavior of a gravity dam at early stages. Firstly, temperature field model was established and verified with the results reported in the literature. Furthermore, the thermo-mechanical behavior of a concrete gravity dam is performed for two configurations: Early age state with pre-cooling and early age without pre-cooling. Thermal stress analysis was also conducted and results showed that the greatest tensile stresses after construction are developed at the heel of dams and resumption of concreting interface due to the internal restraint imposed by the concrete. The numerical results showed that the pre-cooling methods is an effective way to reduce both the hydration temperature and tensile stress induced by the effect of early age. [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]

Analyzing the working conditions of a dam using safety monitoring indices (SMIs) is a relatively intuitive and effective method for dam safety evaluation. Therefore, a reasonable and accurate method for determining the SMIs of a dam is of vital importance for dam safety assessment. However, the current methods for determining the SMIs of dams, especially roller-compacted concrete (RCC) dams, have many shortcomings, such as ignoring the construction process of the dam, the coupling effect among multiple physical fields, etc. In this paper, a novel SMI determination method considering the seepage–stress coupling effects was proposed for RCC dams with the assistance of a constructed seepage and stress coupling model so as to address the deficiency of existing RCC dams in determining SMIs. The coupled mathematical model was developed in COMSOL Multiphysics to establish a finite element analysis model of an RCC gravity dam in Henan Province, China. Moreover, the seepage anisotropy of the RCC construction layers was also considered in the model. Finally, the seepage, stress, and deformation characteristics of the RCC dam were analyzed based on the model, and the seepage and deformation SMIs of the dam were determined and compared with traditional methods. The results show that seepage, stress, and displacement fields are distributed similarly for both coupled and uncoupled models. However, in contrast to the uncoupled model, the hydraulic head contour distribution is more dispersed in the coupled model. Additionally, the stress and displacement simulated by the coupled model increase at different rates, with a more pronounced stress concentration near the dam heel. Comparing the seepage and stress SMIs of RCC dam obtained from different methods, it was found that the indices of dam seepage discharge and crest displacement that are calculated by considering the seepage–stress coupling effect and anisotropic characteristics of RCC construction layers are 34.78% and 31.98% lower than results obtained by ignoring these two effects, respectively. Therefore, it is crucial to consider the seepage–stress coupling effect and the anisotropic characteristics of RCC when determining the SMIs for RCC dams. [ABSTRACT FROM AUTHOR]

In this paper, a seismic-resistant method for reinforced concrete structures in agricultural water engineering is proposed by analyzing reinforced concrete structures. The dynamic response of the simplified high concrete gravity dam model under earthquake, the damage mechanism, and the comparison of the seismic effect based on the two reinforced concrete finite element models under various reinforcement schemes are studied and discussed, the seismic weak parts of the dam are clarified, and the preferential conditions and reasonable reinforcement schemes for the reinforcement of the two reinforced concrete finite element models are proposed, which provide a reference for the design of seismic reinforcement of 200 m class high dams. This paper presents the optimal conditions and reasonable reinforcement solutions for the seismic reinforcement design of a 200-meter-high dam. In this paper, the three-dimensional consistent viscoelastic artificial boundary is applied to the structural foundation interaction problem as a local artificial boundary. Three seismic time-dependent acceleration curves are generated according to the seismic design code spectrum of hydraulic buildings, and then the seismic time-dependent acceleration curves are converted into equivalent loads applied to the three-dimensional consistent viscoelastic artificial boundary to analyze the response characteristics of the picket structure under seismic action. The interaction between reinforcement and concrete is considered, and the tensile stiffening effect of reinforced concrete is simulated by modifying the softening section curve of the concrete. Based on the separated reinforced concrete model, the seismic analysis of the picket structure with different reinforcement ratios is carried out. The effects of reinforcement rate on stress, displacement, damage extension, energy dissipation, and other indicators are investigated. The results show that the reinforcement measures help to slow down the damage development and improve the stress state, but have little effect on the displacement and acceleration. According to the analysis results, the design of the frame structure opening and closing machine beam was improved, the beam system arrangement was optimized, and the dynamic response analysis of the structure under rare earthquakes was carried out again. The analysis results showed that the problem of excessive vertical deformation of the girder where the opening/closing machine is located under rare earthquakes was solved by improving the girder arrangement of the opening/closing beam system. [ABSTRACT FROM AUTHOR]

The overall mechanical behavior of the structure of a gravity dam is comprehensively reflected by modal information included in the measured vibration response. In this study, the dynamic elastic modulus of the dam body and foundation materials were inverted via an underwater explosion, and analyzed. First, the first three main frequencies and basic mode shapes of the dam were obtained based on the acceleration response induced by the explosion. Then, the support vector regression model optimized with the particle swarm optimization algorithm was used to invert the mechanical parameters. The results indicate that the objective function that considers dominant frequency and mode shape has a greater advantage in terms of anti-noise compared to when only the dominant frequency is considered. The inverted dynamic elastic modulus is about 1.5 times that of the static elastic modulus of the corresponding material, and the calculated modal values using the inversion parameters are basically consistent with the measured values. This method provides a new way of determining the dynamic parameters of gravity dams. [ABSTRACT FROM AUTHOR]

Due to the construction technology of roller compacted concrete (RCC) gravity dams, there are many weak layers that have the potential to affect the seismic performance of dams. However, research on the seismic response and failure characteristics of RCC dams considering their layered characteristic is still lacking. In this paper, the zero-thickness cohesive element is presented to model the mechanical behavior of the RCC layers. An impacted concrete beam is selected to verify its effects on simulating crack propagation. Subsequently, the concrete damaged plasticity model is utilized to model concrete under seismic loading. The dynamic interaction in the gravity dam-reservoir-foundation system is considered by coupled acoustic-structural method, whose rationality is validated by seismic failure mode analysis of the Koyna dam under the 1967 Koyna earthquake. The validated algorithms are applied to investigate the influence of the weak layer at different elevations on the seismic response and the failure process of the Guandi RCC gravity dam. On this basis, the effects of well-bonded RCC layers set at intervals along the dam on the nonlinear response and failure modes under strong earthquakes are further investigated. The results reveal that the weak layer will influence the anti-seismic capacity of RCC gravity dams, and the damage characteristics of the dam are significantly changed. In addition, well-bonded RCC layers still affect the seismic response of RCC gravity dams. Increasing displacement response and energy dissipation can be observed. Meanwhile, RCC layers lead to more severe damage to the dam under the same seismic input. [ABSTRACT FROM AUTHOR]

Featured with the harmonic sinusoidal function to reflect temperature effects, the hydrostatic-season-time (HST) model is often used to monitor the concrete gravity dam health, but it does not take account of the effects of environment temperatures in real-term and has flaws especially when applied in conditions of significant temperature variations. A model of Sparrow Search Algorithm optimized error Back Propagation neural network (SSA-BP) based on the hydrostatic-temperature-time (HTT) model is proposed in this paper for predicting the concrete gravity dam displacement using the long-term environment temperature variable sets to reflect temperature effects. Successive Projections Algorithm (SPA) is used for the first time for feature selection on long-term temperature variables to further optimize the model (as SPA-SSA-BP). Through a case study with the practical observed data from a reality high concrete gravity dam, the effectiveness of the new model is verified, suggesting that HTT-based SSA-BP models have better performance than HST with the best result obtained when using the 2-year long variable sets. The SSA-BP model has much lower error in predicting the concrete dam displacement than Multiple Linear Regression (MLR). The arithmetic speed and prediction accuracy of the SPA-SSA-BP model is optimized as it can minimize the collinearity among feature variables in the long-term HTT variable sets, bring down the input variable dimension close to the level of HST, and diminish the redundant data information. [ABSTRACT FROM AUTHOR]

Purpose: The response of an idealized triangular concrete gravity dam is studied due to horizontal and vertical ground motions for both fully reflective and absorptive reservoir bottom conditions. For each combination, in this paper different orders of Givoli-Neta (G-N) high-order truncation condition are aimed to be evaluated from accuracy point of view by comparing the results against corresponding exact solutions which relies on utilizing a two-dimensional fluid hyper-element. Design/methodology/approach: In present study, the dynamic analysis of concrete gravity dam-reservoir systems is formulated by Finite Element (FE)-(FE-TE) approach. In this technique, dam and reservoir are discretized by plane solid and fluid finite elements. Moreover, the G-N high-order condition imposed at the reservoir truncation boundary. This task is formulated by employing a truncation element at that boundary. It is emphasized that reservoir far-field is excluded from the discretized model. Findings: It was observed that trend in gaining accuracy with increase in the order of G-N condition were basically the same for both horizontal and vertical ground motions under full reflective reservoir bottom condition. Moreover, convergence rate increases for absorptive reservoir bottom condition cases in comparison with fully reflective cases. It is also noticed that in certain cases, the responses are hardly distinguishable from corresponding exact responses. This reveals that proposed FE-(FE-TE) analysis technique based on G-N condition is quite successful, and one may fully rely on that for accurate and efficient analysis of concrete gravity dam-reservoir systems. Originality/value: Dynamic analysis of concrete gravity dam-reservoir systems are formulated by a new method. The salient aspect of the technique is that it utilizes G-N high-order condition at the truncation boundary. This is achieved by developing a special truncation element which its generalized matrices are derived for Finite Element Method (FEM) programmers. The method is discussed for all types of excitation and reservoir bottom conditions. It must be emphasized that although time harmonic analysis is considered in the present study, the main part of formulation is explained in the context of time domain. Therefore, the approach can easily be extended for transient type of analysis. [ABSTRACT FROM AUTHOR]

Numerical analysis of pore water pressure changes and the evolution of vertical deformations are the main aspects of the behaviour monitoring of an earth dam. This study analyzed the main aspects of the behaviour monitoring of the Plopi Dam, built on the Gurguiata River, in the northwest of Ia Şi County, Romania. The main data taken into consideration are the dam body's type and material, the foundation's soils, and the dam's monitoring equipment. For tracking the evolution of the pore water pressure, 12 piezometers are used. The Plopi Dam is equipped with 19 piezometers, of which 9 piezometers (marked with B) show the route of the infiltration curve through the dam body and 10 piezometers (marked with F) have the bottom level in the base of the foundation and record the variation of groundwater levels in the aquifer. The paper presents the pore-pressure ratios in embankment material throughout its existence, mainly in the last 12 years, and the influence of external stresses on the hydrostatic levels. Data obtained for a period of 45 years (1978-2023) from 11 landmarks, placed on the dam canopy, were used in the settlement analysis of the embankment The filling in the dam body is still being consolidated, the settlements are significant, the pore pressures are high, so the monitoring of the dam's behaviour is done continuously so that the dam is safely exploited. [ABSTRACT FROM AUTHOR]

This study aims to propose a seismic performance analysis framework based on the oblique incidence theory, estimate a normalized damage response (RDVR) through seismic parameters and incident angles, and explore the variation in dynamic responses of concrete dams with arbitrary incident angles under near-fault vertically polarized shear (SV) waves. Several near-fault pulse-like records were selected, and their decomposed nonpulse (residual) components were used to guarantee the similarity of the response spectra. Furthermore, a seismic input model of the SV wave oblique incidence was developed based on the viscous-spring artificial boundary method, and its accuracy was verified using a numerical application. The effects of the incident angles of SV waves (−30° to 30° at 5° intervals), seismic intensity, and polarity on the damage and displacement responses of a gravity dam–reservoir–foundation system under pulse-like and nonpulse motions were studied. Additionally, the relationships between the incident angle, seismic characteristics [including the peak ground velocity to peak ground acceleration (PGV/PGA) ratio and spectral acceleration Sa(T1)], and the proposed RDVR were established. The most unfavorable incidence angles for different cases were derived. The numerical results showed that the negative direction (from downstream to upstream) has a significant effect on the nonlinear responses of a dam. The seismic features of PGV/PGA exhibited a better correlation with RDVR than Sa(T1). Subsequently, the damage to the gravity dam was estimated using the multivariate fitted method according to the proposed prediction model. The results showed that the proposed prediction model with arbitrary incident angles provides a good estimation of the real results. Thus, it is important to consider the coupled effect of incident angles and seismological characteristics in the seismic assessment of concrete dams located in near-fault regions. [ABSTRACT FROM AUTHOR]

• VMD can separate signals with different variation features from dam displacement. • TSVR and GRU have outstanding nonlinear processing capabilities. • The proposed decomposition-ensemble model has excellent predictive performance. Considering the strong nonstationarity and nonlinearity of the measured displacement, a displacement prediction model of concrete dams is proposed using variational mode decomposition (VMD), twin support vector regression (TSVR) and gated recurrent unit (GRU). Firstly, VMD is adopted to decompose the measured displacement into several signals according to the time series features, and sample entropy (SE) method is used to avoid over-decomposition. Secondly, K -means clustering algorithm is utilized to categorize the decomposed signals into trend, periodic, semi-periodic and stochastic signals, and the trend, periodic and semi-periodic signals are utilized to reconstruct the displacement. Thirdly, the reconstructed displacement is predicted with TSVR-based hydrostatic-seasonal-time (HST) model, and the stochastic signals are predicted with GRU network-based model. Considering the influence of parameters on modelling performance, seagull optimization algorithm (SOA) is employed to determine the optimal parameters of TSVR and GRU. Finally, a displacement prediction model is established by superimposing the predicted values of TSVR-based and GRU-based models. The measured displacement of a gravity dam is utilized to elaborate the implementation process and to test the validity of the proposed model. Results show that the model has excellent predictive performance, which demonstrates that the model is feasible and powerful for precisely predicting dam displacement. [ABSTRACT FROM AUTHOR]

The mechanical parameter inversion model is an essential part of ensuring dam health; it provides a parametric basis for assessing the safe operational behavior of dams using numerical simulation techniques. Due to the complicated nonlinear mapping relationship between the roller compacted concrete (RCC) dam's mechanical parameters and various environmental quantities, as well as conventional statistical models, machine learning methods, and neural networks fail to consider the inputs of fuzzy uncertainty factors. Therefore, the accuracy, efficiency, and stability of inversion models are usually affected by their modeling methods. In this paper, a novel hybrid model for mechanical parameter inversion of an RCC dam is proposed, which uses a radial basis function neural network (RBFNN) to establish the nonlinear mapping relationship between the dam mechanical parameters and the environmental quantities, and the modified particle swarm optimization (PSO) algorithm is used to find the optimal parameters of the model. The modified PSO algorithm makes the inertia weight ω dynamically adjust with the number of iterations to improve the randomness and diversity of the particle population, and population crossover and mutation are introduced to improve the global search ability and convergence speed of the algorithm. The proposed hybrid model is verified and comparatively analyzed by four typical mathematical test functions, and the results show that the proposed model exhibits good performance in parameter inversion accuracy, convergence speed, stability and robustness. Finally, the model is applied to the mechanical parameter inversion analysis of an RCC gravity dam in Henan Province in China. The results show that the proposed model is feasible and reasonable for practical engineering applications, and the relative error between the results obtained by inputting the inverted parameters into the numerical model and monitoring data was within 10%. The methodology derived from this study can provide technical support and a reference for the mechanical parameter inversion analysis of similar dam projects. [ABSTRACT FROM AUTHOR]

In this paper, a comparative study between the smeared crack and extended finite element method (XFEM) is performed. Also, the effective parameters for predicting crack profiles are investigated. The results show that the crack profile in the two models is partially different. Also, the important difference between the two models is computational efficiency. In addition to analysis time, complexity algorithm of XFEM is noticeable. Update assembling matrices, determine interaction integral and control of crack mouth opening at each loading step require enough space of memory which with increasing number of elements, ordinary computers run out of memory during solving. [ABSTRACT FROM AUTHOR]

Data-based dam monitoring model can predict dam behavior and provide scientific basis for risk assessment and decision-making of dam engineering. Traditional dam safety monitoring models established by multiple regression, stepwise regression, gray theory, and other statistics-based methods have poor robustness and generalization. For this reason, an optimized support-vector machine (SVM) whose novelty lies in simple implementation, self-adaptive hyperparameter selection with aid of adaptive position particle swarm optimization (APPSO), and retention of influence factor combination is presented for constructing the dam safety monitoring model. A real-world concrete gravity dam engineering is used to verify the presented approach, and the results indicate the monitoring model built by APPSO–SVM outperforms benchmark models in terms of fitting and prediction accuracy. [ABSTRACT FROM AUTHOR]

In the deformation monitoring data of gravity dams, a few outliers are often found, which will have adverse effects on the monitoring of model building and other data analysis work. In this study, the multiple local outlier coefficient method was proposed to quickly detect the outlier data in real time and to provide high-quality data for subsequent data analysis. This method was based on the idea of distance in the outlier detection algorithm, aiming at laws and characteristics of gravity dam deformation monitoring data. First, the basic principle, calculation steps, and basic features of the multiple local outlier coefficient method were studied. Then, for the two important parameters of the algorithm, the appropriate window length was selected using autocorrelation and partial autocorrelation analysis, and the appropriate threshold values were selected using the 3σ criterion, maximum method, and empirical method. Finally, an engineering example was used to verify that the algorithm could accurately detect the outliers in the gravity dam deformation monitoring data, and the deviation degree and meaning of the outliers were understood according to the calculated outlier coefficient. The multiple local outlier coefficient method has the advantages of a simple calculation principle, fast calculation speed, real-time detection, and a clear meaning of calculation results. By selecting the appropriate parameters, the method could satisfy the outlier detection of different types of data, offering an advantage in adapting to the computing demand of massive monitoring data and improving the intelligence and real-time monitoring of dam safety. [ABSTRACT FROM AUTHOR]

Considering that ANSYS software will automatically quit or the computer will freeze when generating random aggregate models of concrete by using some existing methods that are based on the ANSYS parametric design language (APDL), a new method of random aggregate placement using the ESEL command in APDL and the rotation of the local coordinate system is proposed in this paper. According to this method, a multiscale macroscopic and mesoscopic finite element model of the No. 9 non-overflow dam section of Shimantan dam is constructed. In addition, considering that most of the damage models adopted by the existing mesoscale simulation of concrete damage and fracture cannot take into account the interaction between aggregates, interfacial transition zone (ITZ), and mortar, an improved anisotropic temperature damage model is proposed in this paper. The aggregate placement simulation results show that the method presented in this paper can quickly generate two-dimensional (2D) random concrete aggregates, and the generation of three-dimensional (3D) aggregates can also be completed in a very short time, which can greatly improve the aggregate generation efficiency. Moreover, the aggregate shape generated by this method is very close to the real concrete aggregate shape. The crack propagation simulation results show that the sudden rise and fall of temperature can cause damage in the mortar and ITZ of concrete inside the dam body, which is the main reason for the generation of macroscopic through-cracks in the No. 9 non-overflow dam section of Shimantan dam during the operation period. Finally, it can be learned from the results that the method presented in this paper is reasonable and feasible, and can be extended to the crack propagation simulation of some other concrete gravity and arch dams. [ABSTRACT FROM AUTHOR]

Summary: Dam monitoring model is a contentious and complicated topic in dam safety monitoring research. The single measuring point model and the multidimensional and multi‐measuring point models are the most common dam monitoring models. The single measuring point model has higher accuracy and is widely used, but the rate of utilization of all the monitoring data is limited, making it difficult to reflect the full characteristics of the dam. However, the construction and solution of multidimensional and multipoint models, as well as the analysis of their results, are relatively complicated, and this is still a topic that needs to be explored and researched on a regular basis. The deflection model is a special form of multipoint model, which is rarely studied at present. Therefore, this paper takes concrete gravity dam as the research object, constructs the general form of its deflection statistical monitoring model, and proposes the corresponding identification method based on the uncertainty analysis. The numerical simulation results show that the optimal order of the deflection statistical monitoring model is mainly affected by the upstream water and temperature, showing a strong seasonal pattern. The deflection caused by the upstream water is nearly linear, while that caused by temperature is almost parabolic. The nonlinear degree of deflection will be enhanced when the deformation caused by the upstream water and temperature are superimposed in the same direction. Big measuring errors will "drown" the nonlinear characteristics of the dam's deflection, while a few measuring points will "exaggerate" the nonlinear characteristics. [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]

In order to comprehensively grasp the dynamics of karst collapse, promote the comprehensive prevention and control level of karst collapse, and prevent secondary disasters caused by lava collapse, this study presents a method of karst collapse early warning based on the BP neural network. This method does not need to set the sliding surface in the finite element calculation model. The stress of the sliding surface is fitted according to the spatial stress relationship of the deep karst layer through the improved BP neural network PID control algorithm and BP neural network algorithm, which avoids the modeling and mesh generation of the complex sliding block and has good accuracy and ease of use. According to the basic theory of the BP neural network, the calculation formulas of multilayer feedforward and error back propagation processes are derived, and the two-dimensional and three-dimensional finite element models of gravity dams without and with sliding blocks are established, respectively. Finally, according to the common formulas of viscoelastic artificial boundary and equivalent load, the two-dimensional and three-dimensional input programs of the karst fluid state are compiled, and a neural network early warning model is obtained. The experimental results show that the process karst state simulated by the algorithm is very close to the actual situation, and the minimum value of antisliding coefficient and its occurrence time can be accurately predicted, with an error range of less than 3%. Conclusion. BP neural network prediction can effectively predict karst collapse, with higher prediction accuracy, and can effectively simulate the actual collapse risk. [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 error of the formula caused by those assumptions may have little effect on low gravity dams but can cause significant deviations for high dams from the nature of dam-reservoir interaction during earthquakes. It is well known that dam-reservoir interaction under earthquake forces is very complicated due to various influencing factors. Although the proposed Westergaard correction formula cannot give the exact solution of the hydrodynamic pressure on a gravity dam, the main affecting factors (e.g., dam body's elasticity, dam height) have been considered. Conclusions There are many complicated affecting factors to be considered in the analysis of gravity dam-reservoir water interaction problems. [Extracted from the article]

A novel damage model for concrete has been developed, which can reflect the complex hysteresis phenomena of concrete under cyclic loading, as well as other nonlinear behaviors such as stress softening, stiffness degradation, and irreversible deformation. The model cleverly transforms the complex multiaxial stress state into a uniaxial state by equivalent strain, with few computational parameters and simple mathematical expression. The uniaxial tensile and compressive stress–strain curves matching the actual characteristics are used to accommodate the high asymmetry of concrete in tension and compression, respectively. Meanwhile, an unloading path and a reloading path that can reflect the hysteresis effect under cyclic loading of concrete are established, in which the adopted expressions for the loading and unloading characteristic points do not depend on the shape of the curve. The proposed model has a concise form that can be easily implemented and also shows strong generality and flexibility. Finally, the reliability and correctness of the model are verified by comparing the numerical results with the three-point bending beam test, cyclic loading test, and a seismic damage simulation of the Koyna gravity dam. [ABSTRACT FROM AUTHOR]

With the change of the seismic parameter zoning map of China (GB 18306-2015), the seismic grade of reservoir dams in some areas had changed. At the same time, the standard for seismic design of hydraulic structures (GB 51247-2018) also put forward new requirements for the seismic calculation of reservoir dams. In order to ensure the safe operation of reservoir dams, it is necessary to review the seismic safety based on the finite element numerical simulation technology. Taking the retaining dam section of a gravity dam as an example, a finite element model of the retaining dam section was established, the corresponding calculation and analysis of ground motion were carried out using the mode decomposition response spectrum method, and the seismic safety evaluation of the retaining dam section was carried out according to the calculation results. The results show the following: (1) after considering the effect of hydrodynamic pressure, the natural frequency of the dam body has been significantly reduced, and the first-order natural frequency has been reduced by about 10%; (2) in addition to the local tensile stress at the dam heel, the rest of the vertical stress on the foundation surface of the retaining dam section is compressive stress, and the length of the tensile stress is less than the distance from the dam heel to the curtain center line, which met the requirements; (3) the antisliding stability safety factor of the retaining dam section is greater than the design value in the specification and meets the safety requirements; and (4) the seismic safety of the retaining dam section meets the standard requirements, and the seismic grade is evaluated as grade A. [ABSTRACT FROM AUTHOR]

Dam safety is a priority at the international level, it requires a large amount of data that allows analysts to make optimization on its structural stability, the latter is based on the estimation of the probability of failure from the effects of stress and resistance acting on the dam-reservoir system. This investigation is to establish a methodology in order to optimize the safety of a concrete gravity dam in operation by carrying out a risk analysis which includes the identification of the sources of danger in terms of scenarios that can occur due to a failure on the dam-reservoir system on an implication of natural hazards (floods, earthquakes) and technical accidents such as malfunction of a spillway gate, drain valve, drainage system or important silting. Reliability methods provide a basis for the probabilistic assessment of the structural safety of a dam. They make it possible to take into account in a probabilistic context, the uncertainties in the data associated with the calculation parameters used in the justifications of structural stability and make it possible to assess as closely as possible the intrinsic safety of a concrete gravity dam. [ABSTRACT FROM AUTHOR]

Phase-field models have become a powerful tool to simulate crack propagation. They regularize the fracture discontinuity and smooth the transition between the intact and the damaged regions. Based on the thermodynamic function and a diffusive field, they regularize the variational approach to fracture that generalizes Griffith's theory for brittle fracture. Phase-field models are capable to simulate complex fracture patterns efficiently and straightforwardly. In this paper, we introduce a hybrid phasefield approach to simulate the crack propagation in laboratory-scale and lifescale structures. First, we apply our methodology to the three-point bending test on notched laboratory beams. Second, we simulate the fracture propagation in a life-size structure: the Koyna gravity dam. We account for the pressure load inside the fracture, and we study the effect of the position and number of initial fractures in the upstream face and the value of the Griffith critical energy release, on the fracture propagation under a flood event. The position of the fracture plays an important role in the final fracture pattern and crest displacements, whereas the value of the Griffith critical energy release alters the onset of the fracture propagation. We conclude that phase-field models are a promising computational tool that may be applied to real engineering problems. [ABSTRACT FROM AUTHOR]

Underwater explosion process mainly includes the preceding blast wave and the succeeding bubble pulsation, while the effect of bubble pulsation on hydraulic structures is always neglected. This paper aims to numerically study the dynamic behaviors of prototype concrete gravity dam against underwater explosion, considering the combined effects of blast wave and bubble pulsation. Firstly, a finite element analysis (FEA) approach for predicting the underwater explosion loadings, as well as the damage evolution and dynamic responses of dam against underwater explosions was proposed, in which the hydrostatic pressure of reservoir and the dead load of dam were considered. Based on Cole's formula and the existing underwater explosion tests, the reliability of FEA approach, including the mesh sizes, material models and the corresponding parameters, as well as the mapping, Fluid-Structure Interaction and contact algorithms, was comprehensively validated. Secondly, to realize the simulation of the prototype gravity dam impeded by the validated small Lagrange mesh size, a mesh transition strategy was proposed based on the equivalence of dam damage modes and total eroded element mass. Finally, the dynamic behaviors of a typical 120 m-height concrete gravity dam against underwater explosion, i.e., 1 t of TNT equivalence detonated at a depth of 35 m and standoff distances of 4–16 m, were examined. The dimensionless distance λ R , i.e., the ratio of the standoff distance to the maximum bubble radius, was introduced to quantitatively evaluate the underwater explosion loadings and dynamic behaviors of the dam. It indicates that, the blast wave firstly leads to the local compressive damage on the upstream surface, as well as the tensile damage on the downstream folded slope and dam heel. The succeeding free vibration and bubble pulsation will further aggravate the damage degree, resulting in the cracking of dam neck and heel. Especially for the scenarios when λ R ≤ 1.22, the overall sliding of dam is highly prone to occur. • FEA approach for hydraulic structures against underwater explosions is proposed. • Accurate simulation for prototype dam is realized using mesh transition strategy. • Dynamic behaviors of dam against combined blast wave and bubble pulsation are studied. • Effect of standoff distance on blast resistance of concrete gravity dam is discussed. [ABSTRACT FROM AUTHOR]

The stable reliability analysis of dams is a challenging topic in geotechnical engineering safety. Because there are more complex system failure modes and high-dimensional parameters in large solid structures, it is difficult to calculate failure probability efficiently and accurately using general reliability analysis methods. Most methods suffer from complex iterative processes and the curse of dimensionality. In this study, an improved importance sampling method based on multi-objective optimization is proposed and applied to reliability analysis for dam sliding. The optimization function is constructed from the limit state surface and the original probability density. The optimal sampling center is selected from the optimization results by considering the dominant performance function as well as the coefficient of variation of the weight function. Four numerical examples and a case study of the sliding stability of a gravity dam demonstrate the accuracy and efficiency of the proposed method. The results show that the proposed method is not sensitive to the specific multi-objective optimization algorithm used. Simulations using multiple sampling centers perform better overall than simulations using a single sampling center. In particular, the proposed method remains applicable to parallel systems with 20 high-dimensional parameters that are virtually immune to the curse of dimensionality. [ABSTRACT FROM AUTHOR]

Concrete gravity dams are a common form of dams. The dynamic response analysis of concrete gravity dams under the action of underwater explosions is indispensable for survivability assessments. Due to the constraints of the environment and other conditions, an underwater explosion test of a prototype concrete gravity dam is difficult to achieve. The centrifuge scaled-down test that satisfies similarity theory provides a new way to study the dynamic response of underwater explosions on concrete gravity dams. In a near-field explosion, the shock wave of an underwater explosion will cause direct damage to the gravity dam, and the detonation products after the shock wave will aggravate the damage. Under the premise of verifying the concrete dynamic response material parameters and the fluid–solid coupling model of the underwater explosion, numerical calculations of the scaled underwater explosion model of the centrifuge and the prototype underwater explosion were carried out, and the similarity between the scaled dam response model of the underwater explosion centrifuge and the prototype was discussed. The analysis shows that the scaled-down centrifuge model can better reflect the local damage of the prototype dam subjected to shock waves. The difference between the scaled centrifuge model and the prototype model of underwater explosion damage to the dam is concentrated on the overall damage. The damage effect of detonation products on the prototype dam body is mainly concentrated in the middle and lower parts of the dam body, while the damage effect of detonation products on the dam body in the scaled-down model is mainly concentrated in the middle and upper parts of the dam body. [ABSTRACT FROM AUTHOR]

The sliding of dam base along dam-foundation rock interface during earthquake excitation can decrease the earthquake response of the dam. The present study reveals a numerical simulation of the seismic failure response for Oued Fodda concrete gravity dam, located in northwest of Algeria, considering base sliding. Nonlinear finite element analyses are performed for Oued Fodda damfoundation rock system. The Smeared crack approach is used to present cracking of dam concrete under the 1980 El Asnam earthquake (M7) using Willam and Warnke failure criterion. The hydrodynamic pressure of the reservoir water is modeled as added mass using the Westergaard approach. The sliding behavior of contractions joints is modeled by surface-surface contact elements that provide the friction contact at dam-foundation interface. Drucker-Prager model is considered for dam concrete in nonlinear analysis. According to numerical analyses, several cracks may appear due to tension particularly at middle upper parts located along the symmetry central axis of the dam in both upstream and downstream faces. Although the dam sliding on its foundation reduces the magnitude of principal tensile stresses in dam body; however, the reduction magnitude is generally not large enough to preclude the cracks propagation in dam body. [ABSTRACT FROM AUTHOR]

The bearing capacity of large strip foundations under combined loading is an important issue in geotechnical engineering, which is related to the design and stability analysis of foundations such as gravity dams, retaining walls, and ground anchorages of bridges. Herein, a new model for predicting the bearing capacity of large strip foundations under combined loading was proposed. First, a series of numerical simulation analyses of a large strip foundation resting on the surface of the soil were conducted to investigate the shape of the failure envelope in the V–M–H (vertical load, overturning moment, and horizontal load) loading space, and an improved form of failure equation was proposed. Second, the main factors influencing Vmax (the vertical ultimate bearing capacity) and the shape of the failure envelope were determined. Last, an applicable empirical equation of the failure envelope in the V–M–H loading space was presented. The results show that the deflection angle of the ellipse (θ), which is considered as a certain constant by previous studies, varies with the vertical load (V); the width of the foundation (B), the depth of the foundation (D), the cohesion of the soil (c), and the internal friction angle of the soil (φ) are the main factors influencing Vmax and the shape of the failure envelope; only parameters B, D, c, φ, and γ are needed to determine, in a unique way, the empirical equation of the failure envelope in the V–M–H loading space. The proposed model provides a convenient means of calculating the bearing capacity of large strip foundations on soil under combined loading. [ABSTRACT FROM AUTHOR]

Finite element method (FEM) is usually used in dam and large underground cavern engineering to evaluate complex anti-seepage and drainage systems. In general, the substructure method is used to simulate the drainage hole array, but it becomes cumbersome when the number of drainage holes is large and the model is more complicated. In this study, the drainage holes were simplified and simulated as a line. The calculation results of the proposed method were then compared with those of the substructure simulation method and the well flow formula. This method has approximate accuracy, and it is easier to model with fewer nodes and elements compared with the substructure method. Based on the data of Heihe Reservoir, a three-dimensional equivalent continuum seepage FEM, reflecting the topography and geology of the dam area, was established, along with engineering layout and anti-seepage drainage system. The seepage field of nine different anti-seepage and drainage facilities were studied. The effects of drainage hole spacing and impervious curtain on seepage field were investigated. When the drainage holes were working normally and the drainage hole spacing was 2 m, the phreatic line in the dam body was the lowest and the drainage effect was the best. The analysis results showed that the failure of drainage holes on the left and right banks significantly influenced the seepage discharge of dam body and impervious curtain. According to the distribution of seepage field, a reasonable spacing of drainage holes is selected, and reasonable suggestions are put forward for anti-seepage and drainage in different parts. [ABSTRACT FROM AUTHOR]

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

This study investigates the use of a modified statistical model to quantitatively analyze and assess the current operation status of an RCC (Roller Compacted Concrete) gravity dam in an alpine region. Initially, combined with the measured temperature analysis and temperature field simulation results of a typical dam block, it is demonstrated that frost heaving data are essential to monitor dam crest deformation. The frost heaving factor is introduced using an engineering analogy method, and a modified statistical model considering frost heaving based on the Heaviside step function adaptive model is established. The analysis shows that (a) in the low-temperature season, the deformation near the dam crest is affected due to a wide range of negative-temperature zones; (b) the frost heaving component identified using the novel statistical model shows that the dam crest frost heaving deformation presents a variation law of periodic pulsed fluctuation and a ten-day cycle of hysteresis. The safety assessment of concrete dams crest without any insulation measures in alpine regions should thoroughly consider the displacement caused by frost heaving, which is highly relevant to improving the accuracy of dam safety evaluations over long-term service periods. [ABSTRACT FROM AUTHOR]

Water‐driven fracture propagation is a fundamental issue in the failure analysis of cracked concrete gravity dams. In the present paper, a poromechanical‐damage–based model is proposed to study the water‐fracture interaction in saturated porous media in order to highlight the importance of considering the presence of the pressurized water in propagating fractures. The solid behavior is described by a plastic damage model. The crack openings computation is performed using a post‐processing method combined with the fracture energy regularization concept. The hydraulic behavior is governed by Darcy's law for the un‐cracked material. After cracking, the flow through fracture is driven by the cubic law and the material permeability is increased as the crack propagates. The validations are performed on a wedge splitting test. The failure analysis of a concrete gravity dam under hydraulic fracturing shows that considering the water pressure in cracks leads to deeper and larger fracture propagation. [ABSTRACT FROM AUTHOR]