Earth-rockfill Dam Research Articles

Seismic reliability analysis of high earth-rockfill dams subjected to mainshock-aftershock sequences using a novel noninvasive stochastic finite element method

To eliminate the limitations of the deterministic analysis approach currently used for seismic safety evaluation of dams, this paper introduces a novel framework for analyzing the safety of high dams based on probability and reliability. This framework incorporates the randomness nature and impact of aftershocks in simulating main-aftershock sequences. Then, an improved generalized plastic model (GPM) is adopted to perform static-dynamic deformation analysis of the dam, which is achieved by only one set of parameters. Lastly, the non-invasive stochastic finite element method (SFEM), combined with the direct probability integral method (DPIM), is adopted. This method yields probability density functions (PDFs) for each seismic response moment, ensuring both efficient and accurate assessment of dynamic time-varying reliability. The new framework was employed to evaluate the deformation reliability and slope stability of Lianghekou dam. Results demonstrate its superior efficiency compared to conventional methods, verifying its suitability for stochastic dynamic analysis of large and complex nonlinear structures. The study suggests that the variable impact of aftershocks on dam stability depends on design requirements, emphasizing the necessity to consider such effects in dam safety assessments.

A novel method for settlement imputation and monitoring of earth-rockfill dams subjected to large-scale missing data

Various missing values inevitably exist in the settlement monitoring data of prolonged operation of earth-rockfill dams, which delays or even interrupts the dam structure analytical procedure. This study aims to develop a reliable method for addressing the missing data problem and monitoring earth-rockfill dam settlement behavior. First, an imputation model, support vector regression based on the finite element method and time input (FEMTSVR), is proposed and offers superior performance when capturing complex nonlinear mappings from environmental variables to settlement on small sample data. Herein, an improved particle swarm optimization algorithm (IPSO) is developed, realizing the nonlinear adjustment of weights and parameter reduction during hyperparameter optimization. Then, this study establishes a sequential prediction model based on gate recurrent unit (GRU) networks to monitor dam behavior on the imputed and complete dataset. Eventually, the proposed method is evaluated using real-world earth-rockfill dam monitoring data with the help of statistical indicators, demonstrating its efficiency in monitoring settlement data subjected to large-scale missingness. This study provides a robust database for dam structural health monitoring, while also providing a promising framework for the safety assessment of other civil or hydraulic engineering based on raw monitoring data.

A Data Assimilation Methodology to Analyze the Unsaturated Seepage of an Earth–Rockfill Dam Using Physics-Informed Neural Networks Based on Hybrid Constraints

Data assimilation for unconfined seepage analysis has faced significant challenges due to hybrid causes, such as sparse measurements, heterogeneity of porous media, and computationally expensive forward models. To address these bottlenecks, this paper introduces a physics-informed neural network (PINN) model to resolve the data assimilation problem for seepage analysis of unsaturated earth–rockfill dams. This strategy offers a solution that decreases the reliance on numerical models and enables an accurate and efficient prediction of seepage parameters for complex models in the case of sparse observational data. For the first attempt in this study, the observed values are obtained by random sampling of numerical solutions, which are then contributed to the synchronous constraints in the loss function by informing both the seepage control equations and boundary conditions. To minimize the effects of sharp gradient shifts in seepage parameters within the research domain, a residual adaptive refinement (RAR) constraint is introduced to strategically allocate training points around positions with significant residuals in partial differential equations (PDEs), which could facilitate enhancing the prediction accuracy. The model’s effectiveness and precision are evaluated by analyzing the proposed strategy against the numerical solutions. The results indicate that even with limited sparse data, the PINN model has great potential to predict seepage data and identify complex structures and anomalies inside the dam. By incorporating coupling constraints, the validity of our PINN model could lead to theoretically viable applications of hydrogeophysical inversion or multi-parameter seepage inversion. The results show that the proposed framework can predict the seepage parameters for the entire research domain with only a small amount of observation data. Furthermore, with a small amount of observation data, PINNs are able to obtain more accurate results than purely data-driven DNNs.

A new approach for seepage parameter inversion of earth–rockfill dams based on an improved sparrow search algorithm

This paper introduces a novel seepage parameter inversion method for earth–rockfill dams. The method utilizes pore water pressure data and employs a radial basis function (RBF) neural network as a surrogate model, which is optimized with the improved chaos sparrow search algorithm (ICSSA) using a hybrid strategy. The improved surrogate model (ICSSA–RBF) establishes a nonlinear relationship between the seepage parameter and pore water pressure. Unlike the original algorithm, the algorithm proposed in this paper can avoid three principal problems: the optimization search falling into a local optimal value, the population diversity decreasing during the iteration process, and the RBF neural network being prone to overfitting. The ICSSA, which is proficient in recognizing an objective function's significant values, is also chosen for identifying the parameters. To validate the effectiveness of the proposed approach, four classical test functions, a numerical model, and an actual engineering project are considered for the comparative analysis. The study outcomes reveal that ICSSA–RBF exhibits an exceptional level of prediction accuracy, with a mean relative error of less than 5‰. The findings also affirm the potential of the proposed approach in parameter identification and its superiority in facilitating the evaluation of seepage parameters in earth–rockfill dams.

Seepage safety evaluation of high earth-rockfill dams considering spatial variability of hydraulic parameters via subset simulation

Seepage failure of high earth-rockfill dams have devastating consequences, and its safety analysis is of great importance in the design phase. However, the highest safety standards in high dams pose a challenge to the calculated efficiency of safety assessment. To address this problem, a random seepage safety assessment method which can consider the spatial variability of hydraulic parameters is proposed. Firstly, the spatial variability of the hydraulic parameters in the impervious materials is simulated using the covariance matrix decomposition under the framework of the non-intrusive finite element method. Then, according to the safety index of critical hydraulic gradient, the seepage stability formula is established to evaluate the safety state. Finally, considering that the highest safety standards in high dams make the probability of seepage hazard small (low failure probability event), it may require more than 10,000 deterministic calculations to complete the assessment process. Therefore, an efficient method based on subset simulation is proposed to optimize the computational efficiency. After the seepage safety evaluation of a 315 m high dam, the results show that the hydraulic conductivity of the core wall has the greatest influence on the seepage safety of the dam, and even under the influence of strong parameter spatial variability, its seepage failure probability is lower than 10-3. Compared with Monte Carlo simulation, the proposed method requires only 1/11 of the computation time at the 10-3 failure level. In addition, the results of grey relational analysis show that the coefficient of variation and correlation distance have obvious effects on seepage safety, and the autocorrelation distance has a greater effect.

Jaya-ICSM: A rapid inverse method driven by monitoring data for concrete-faced rockfill dams static displacement simulation

This paper presents a rapid static parameter inverse method for concrete-faced rockfill dams based on displacement data using an improved cloud surrogate model and the Jaya optimization algorithm. The improved cloud surrogate model (ICSM), which evolved from the uncertainty cloud theory, is used rapidly to establish a nonlinear relationship between static parameters and displacement. The Jaya optimization algorithm, which is proficient in recognizing the extreme value of the objective function, is selected for parameter identification. To verify the performance of the proposed method, an inverse analysis of two numerical models and a real engineering project is considered, and a comparative study with the BP neural network as the surrogate model is conducted. Study results demonstrate that ICSM has an extremely high prediction accuracy, with a mean relative error that is always under 1 %. The prediction accuracy does not increase too much even under complex nonlinear conditions or when dealing with sparse training data. Moreover, Jaya-ICSM maintains high computational efficiency throughout the entire inverse analysis, saving more than 98 % of the time compared to another inverse method and proving to be much better than direct inversion based on the finite element method. This enables real-time inverse analysis and state feedback of complex engineering. The results also illustrate that the Jaya-ICSM is promising in parameter recognition and superior in supporting the displacement evaluation of earth-rock dams. Therefore, the proposed method can be an effective tool for engineers to evaluate the safety of earth-rockfill dams and ensure their long-term stability.

Seismic behavior and reinforcement mechanisms of earth dam and liquefiable foundation system by shaking table tests and numerical simulation

Earth-rockfill dams suffer from various geotechnical disasters during seismic hazards, and liquefiable foundation will aggravate these damages by reducing the foundation bearing capacity. In this research, a quasi-three-dimensional earth dam and liquefiable foundation model was designed to study the seismic behavior, liquefaction process and reinforcement mechanism. Three typical models, including unreinforced (UR), raft reinforced (RR), and gravel pile reinforced (GPR) models, have been investigated by 1-G shaking table test and numerical simulation. The experiment of model UR was utilized for calibrating the numerical parameters via the inverted method, and two other experiments were set as the simulation targets using the above-mentioned parameters. The experiment and simulation results have shown that uneven settlement and cracks appeared in model UR are mainly caused by foundation liquefaction rather than seismic residual deformation. The raft slab and gravel piles mitigate the uneven settlement and cracking potential significantly by multiple reinforcement mechanisms including the supporting effect, drainage effect, and stiffness improvement effect.

Plasticity inverse analysis for Zipingpu concrete-faced rockfill dam based on advanced cloud surrogate model via improved Jaya optimization algorithm

A notable prerequisite for state assessments of earth-rockfill dams is a reasonable and accurate description of the deformation. However, due to the complexity of rockfill, its mechanical properties are often difficult to fully describe using the forward finite element method (FEM). The result of FEM depends on the constitutive model and its parameters’ selection usually obtained empirically or from indoor tests. In this paper, the improved Jaya optimization algorithm (iJaya) is combined with the advanced cloud surrogate model (ACSM) to perform inverse analysis, which has great advantages in computational speed and accuracy. The generalized plastic model (GPM) is chosen for simulation and its parameters are analyzed. Finally, the deformation field of the Zipingpu Dam is reconstructed. The results show that the ACSM can greatly replace the FEM even using GPM, achieving high prediction accuracy and reduced computation time. iJaya-ACSM can also identify the parameters of the GPM quickly and correctly. The deformation of ERDs can be well simulated based on the inverted parameters, which could help to know the state of the whole dam body. In conclusion, the proposed inverse method is promising in analyzing the deformation of ERDs.

Study on Influence of Numerical Simulation Accuracy on High Core Wall Rockfill Dam Deformation and Crack Analysis

With the increasing height of rockfill dams, detailed and effective numerical simulation for the dam design and construction has become increasingly important. This paper develops a detailed and effective finite element simulation program for the construction and impoundment process of high large-scale earth rockfill dams and studies the influence of numerical simulation accuracy on dam deformation and crack analysis. By establishing the subdivision mode of conventional elements, the mesh generation of detailed finite element simulation is realized. Using the row compression storage method and the MPI parallel method, the calculation program of the total stiffness matrix is developed on the Linux operating system. On the basis of the detailed simulation program above, the filling and impoundment process of Pubugou high core wall rockfill dam is simulated, and it is found that the influence of simulation accuracy on the core wall zone is greater than that on the rockfill zone. Compared with the dam construction process, the detailed simulation of the impoundment process is more necessary. When simulating the impoundment process, there is a significant effect of simulation accuracy on the simulation result of the upstream side of the core wall and the upstream filtration zone. So, it is necessary to simulate the impoundment process of the earth rockfill dam in detail. Moreover, using the detailed method to simulate the impoundment process of earth rockfill dams can more accurately predict dam cracks.

An innovation gain-adaptive Kalman filter for unmanned vibratory roller positioning

The precise positioning of an unmanned vibratory roller is the key to the compaction quality. Currently, many earth-rockfill dams are constructed in deep narrow valleys. Ultra-wide band (UWB) is widely used to overcome the partially denied problem of the global navigation satellite system. However, due to the complex noisy interference on construction sites, the accuracy of UWB is insufficient. To ensure the precise positioning of the unmanned vibratory roller, we propose an innovation gain-adaptive Kalman filter (IG-AKF) algorithm. The IG-AKF can adjust the noise covariance based on the relationship between the historical state statistics and positioning deviation. In addition, an attention decay mechanism that associates more attention to recent states is employed. Moreover, a diversity Harris hawks optimisation is proposed to optimise hyper-parameters in the IG-AKF. The proposed method was applied in Lianghekou project. Compared with UWB and the standard KF, the positioning accuracy of the IG-AKF was significantly improved.

Large-scale shaking table model tests and numerical simulation for composite reinforcement aseismic measure of high earth rockfill dam

<p indent="0mm">The aseismic safety of high earth rockfill dams is an important problem in engineering construction in the intensive earthquake area of West China. A composite reinforcement aseismic measure (CRAM) for high earth rockfill dams was developed. The CRAM’s effectiveness and reliability were validated using comparative model tests on a large-scale shaking table. Numerical simulation was used to examine the CRAM’s reinforcement mechanism. The results demonstrated that the CRAM had an inhibiting effect on the acceleration response; the CRAM can effectively inhibit the loosening and slipping of rockfill at the crest and reduce earthquake-induced permanent deformation. The numerical simulation also revealed that the shear strain amplitude and distribution were significantly altered. A slightly larger shear strain appeared at the front of the CRAM’s internal reinforcement materials, and the dam slope’s potential sliding surface was transformed from shallow sliding to deep sliding. As a result, the CRAM can improve the high earth rockfill dam’s seismic safety. The research results can provide a reference for the seismic design of the high rockfill dam in the intensive earthquake area.

Rockfill material segmentation and gradation calculation based on deep learning

The gradation of rockfill materials affected the rolling quality and body strength of earth-rockfill dam. To address the limitations of manual screening and traditional computer vision methods, a gradation detection method suitable for rockfill dam construction sites was proposed based on deep learning, which can output the detection results end-to-end. The method utilized the modified MASK R-CNN model to locate and segment rockfill materials. Specifically, the model used ResNeXt101 as the backbone network and adds the squeeze-and-excitation block to enhance the feature extraction capability of the model. The detection results of 500 test images showed that proposed method had high accuracy, the average precision and intersection over union value of the model reach 0.934 and 0.879. The morphological characteristics of rockfill particles were extracted by rotating calipers algorithm and used for grading calculation. Comparing this calculation method with manual screening, the results indicated that the overall fitting effect of the gradation detected by proposed method was in accord with the actual gradation parameters. The gradation of rockfill materials can be obtained within 60 s. This paper provided a new method for rapid analysis of particle size distribution, which can be used for auxiliary construction.

Time History Method of Three-Dimensional Dynamic Stability Analysis for High Earth-Rockfill Dam and Its Application

Accurately grasping the stability characteristics of high earth-rockfill dam slopes is the key to the seismic safety evaluation of dams. In this research, the development and application of the common methods for slope stability analysis are reviewed firstly. Then, a three-dimensional dynamic time history stability analysis method is presented, and corresponding software is developed based on the sliding surface finite element stress method combined with the three-dimensional finite element dynamic response. This method makes the three-dimensional dynamic stability analysis efficient, and the effectiveness of this software is verified. Finally, the two-dimensional (2D) and three-dimensional (3D) dynamic stability analyses of a high concrete face dam are carried out, and the stability of the dam’s downstream slope under seismic load is studied. The results indicate that there are many differences between the results of the traditional 2D and 3D stability analyses. The time history of the safety factor, local safety behavior, overall shape and spatial position of the potential sliding body, and even the sliding process of failure can be captured with 3D stability analysis.

The Inversion Analysis and Material Parameter Optimization of a High Earth-Rockfill Dam during Construction Periods

Inversion analysis is usually an efficient solution to process the monitoring data of earth-rockfill dams. However, it is still difficult to obtain calculation results that are consistent with monitoring data due to different construction statuses. To deal with this situation and to introduce a new solution to improve calculation accuracy, the general method of inversion analysis based on back-propagation neural networks and the original step-by-step inversion method assuming that the parameters of the constitutive model vary with construction periods are introduced and verified in this work. Then, both methods are applied in the inversion analysis of a high gravelly soil core rock-fill dam during construction periods. Moreover, the relationship between the inversed material parameters and the stress values of the core wall is discussed. The material parameters are further optimized to obtain more accurate displacement values. The results show that the step-by-step inversion method has a higher accuracy in vertical compression values compared with the conventional inversion method, the trend of material parameter K is more significant than other parameters, and the proposed variable parameter constitutive model has an accuracy between the step-by-step and conventional inversion methods. Conclusions can be drawn that the original step-by-step inversion method has more advantages than the conventional method and the variable parameter constitutive model proposed in this paper might be more suitable for the analysis of a high earth-rockfill dam during construction periods.

Unified modeling behavior of rockfill materials along different loading stress paths

Rockfill materials used for dam construction show obvious stress path dependency during construction process. The constitutive model for rockfill materials are mainly established based on conventional triaxial test. This brings some deviation to the numerical calculation for earth rockfill dam engineering, and it is necessary to develop a constitutive model considering stress paths effect. In the framework of generalized plasticity, plastic modulus can be expressed as the function of dilatancy equation and tangent modulus, hence the influence of stress paths on model can be transfer to the dilatancy equation and tangent modulus. This leads to a new method to describe stress-strain response of rockfill under various loading stress paths. Based on the analysis of large-scale triaxial experiments of rockfill materials with various stress paths, we proposed new dilatancy equation and tangent modulus to better describe stress paths effect and corresponding modified generalized plasticity model is established. Through the prediction and comparison of three groups of rockfill materials triaxial tests, the model established in this paper can simulate behaviors of rockfill materials under various stress paths, using only a set of parameters.

Dynamic response analysis of high earth-rockfill dam subjected to P wave with arbitrary incoming angles

The dynamic response analysis of high earth-rockfill dams mostly only considers the vertical incidence of seismic waves. However, due to the randomness and uncertainty of earthquakes, for near-field earthquakes, oblique incident waves generally dominate. Therefore, understanding the nonlinear dynamic response of high earth-rockfill dams under the oblique incident seismic wave is of great significance to the seismic safety evaluation of the dams. For this purpose, the seismic wave input method of P wave with arbitrary angle that considers near-field oblique incidence is proposed, which is realized through the Fortran program, and the validity and accuracy of the method and the program are verified by two examples. The proposed method is applied to study the dynamic response analysis of the Nuozhadu earth core rockfill dam under oblique incident P wave. In addition, the three-dimensional interaction system of the dam-foundation-canyon is considered based on the viscous-spring boundary model, which reflects as much as possible the environmental conditions of the high earth-rockfill dam when the actual earthquake occurs. The numerical results reveal that the incident angle of P wave significantly affects the dynamic response of the dam. For acceleration amplification factor and residual deformation, the most damaging incident angle is the incident angle α = 60°, rather than in the vertical direction. Besides, when the seismic wave is incident obliquely, the value of residual deformation along the transverse direction is greater than that along the stream direction. It is recommended that the influence of oblique incident P wave should be considered in the seismic design of high earth-rockfill dams.

A New Apparatus for Shear-Seepage Testing at the Clayey Soil-Structure Interface

Abstract In high earth-rockfill dams, large shear displacement exists in the contact area between the earth core and the concrete cushion at the bottom and on both sides of the banks of a river valley. Exposed to a high hydraulic gradient, seepage erosion is likely to occur in this area. A practical measure is to compact a thin layer of clayey soil with high plasticity such that it lies between the earth core and the concrete cushion. It is crucial to evaluate the capabilities of a clayey soil for this thin layer. A new apparatus modified from a conventional triaxial apparatus is developed to test the seepage characteristics of the clayey soil-structure interface under large relative shear conditions. Compared to the previous device, the new device can achieve a larger relative shear displacement that is closer to the actual condition while providing stress and a seepage state with a simple testing procedure. This apparatus consists of a soil-structure model, a vertical loading system, two back-pressure systems, and a monitoring system. The vertical loading system allows the soil-structure displacement to develop at a constant speed. Two back-pressure systems can simulate the high hydraulic gradient and the consolidation state of the specimen. The monitoring system automatically records the force load, the volume of water outflow, and the volume change in the pressure chamber. Basic tests and shear-seepage tests were conducted using this device to validate its efficiency and reliability. The results indicate that the permeability of the soil-structure interface decreases with the shear displacement over a large range. A finite element (FE) analysis was carried out to reveal the strain-stress and seepage state inside the specimen to explain the seepage mechanism.

Internal deformation monitoring for earth-rockfill dam via high-precision flexible pipeline measurements

The internal deformation of high earth-rockfill dam is an important parameter that reflects its safety. There is an urgent need to have a precise and reliable internal deformation monitoring technology due to the limitation of traditional sensors. We propose a novel method to monitor internal deformation of dam through continuous measurement of flexible pipelines that embedded in the dam. A pipeline robot is invented, with one inertial measurement unit and multiple odometers, to measure the deformation of the customized pipeline system. The proposed method is verified through filed tests and real dam in suit experiments. The results show that the relative deformation measurement precision is approximately 1/100,000 the length of the pipeline and millimeter-level deformation measurement over 300 m can be realized. This technology is promising for internal deformation monitoring of high-rockfill dams. Further research will focus on the miniaturization of measurement system and reliability improvement of this technology.

ГИДРАВЛИЧЕСКИЙ РАСЧЕТ РЕЗЕРВНОГО ВОДОСБРОСА (ВОДОСЛИВА С ШИРОКИМ ПОРОГОМ)

Purpose: to carry out hydraulic studies and calculations of a reserve spillway structure (broad-crested weir) of a rockfill dam. Materials and methods. Current studies show that in open channels the regime of fluid movement can be different, and the boundary surfaces of the channel in some cases should be considered as hydraulically smooth, in others – as hydraulically rough. The broad-crested weir of rectangular and trapezoidal section is considered. To determine the experimental discharge coefficient of the reserve spillway of an earth rockfill dam, the known dependences for unflooded broad-crested obtained by A. R. Berezinsky and D. I. Kumin were used. Results. Based on the results of comparing the calculated flow coefficients with the experimental data of other authors, close values with the data of A. R. Berezinsky and D. N. Kumin were obtained. At the same time, the values of the discharge coefficients of the water discharge according to Berezinsky and Kumin are in the range of 0.339 and 0.324, which confirms their compliance and high accuracy. The results of the calculation of the filtration flow rate through the rockfill of the dam with a reserve spillway are the filtration flow rates in the range of 726.81–2260.76 m³/s. Conclusions. The performed calculations showed that the values of the discharge coefficients of the weir of a trapezoidal section correspond to the data obtained by A. R. Berezinsky and D. I. Kumin. At the same time, the values of the spillway discharge coefficients by Berezinsky and Kumin are within acceptable limits, which confirms their compliance. The average flow velocities passing through the broad-crested weir were: for profile 1 – 3.76 m/s, for profile 2 – 0.612 m/s, for profile 3 – 2.13 m/s.

Research on Flood Discharge and Energy Dissipation of a Tunnel Group Layout for a Super-High Rockfill Dam in a High-Altitude Region

Under the condition of a large dip angle between the flood discharging structure axis and the downstream cushion pool centerline, the downstream flow connection for the discharging tunnel group is poor, and the lower air pressure in high-altitude areas increases its influence on the trajectory distance of the nappe, further increasing the difficulty of predicting the flood discharge and energy dissipation layout. Based on the RM hydropower project with the world’s highest earth-rockfill dam, this paper studies the problem of a large included angle flip energy dissipation layout of a tunnel group flood discharge using the method of the overall hydraulic physical model test. The test results show that the conventional flip outlet mode has a long nappe falling point, a serious shortage of effective energy dissipation space, a large dynamic hydraulic pressure impact peak value on the bottom slab and side wall of the plunge pool, a poor flow connection between the outlet of the plunge pool and the downstream river channel, and a low energy dissipation rate. Considering the influence of a low-pressure environment, when the “transverse diffusion and downward incidence” outflow is adopted, the nappe falling point shrinks by 11 m, the energy dissipation form of the plunge pool is greatly improved, the effective energy dissipation space is increased by 159%, the RMS of the maximum fluctuating pressure is reduced by 74%, the outflow is smoothly connected with the downstream river, the energy dissipation rate is increased by 0.8%, and the protection range of flood discharge atomization is significantly reduced. This effectively solves the safety problems of large included angle discharge return channels and the energy dissipation and erosion prevention of super-high rockfill dams.