Rockfill Dam Research Articles

Modeling the Post-construction Deformation of Spillways over Concrete-Faced Rockfill Dams

Modeling the Post-construction Deformation of Spillways over Concrete-Faced Rockfill Dams

A theoretical model for evaluating the deterioration of mechanical properties of rockfill materials

The mechanical properties of rockfill materials deteriorate when subjected to different environmental factors. Accurately evaluating the deterioration effect on mechanical properties of rockfill materials is crucial for the lifecycle safety assessment of rockfill dams. In this study, we propose a theoretical model that can analyze the deterioration effect on stress and deformation characteristics of rockfill materials caused by weathering. Specifically, based on assumptions of geometric and breakage similarity, the stress and strain tensors of rockfill assemblies before and after deterioration can be derived from granular matter mechanics by introducing a deterioration coefficient. The deterioration coefficient defines the ratio between the grain crushing strength of deteriorated and undeteriorated rock grains, and can be obtained by single grain crushing tests. The deterioration coefficient is introduced into the Duncan-Chang EB model to quantitatively evaluate the deterioration effect on stress and deformation characteristics of rockfill materials. The triaxial test results of deteriorated and undeteriorated rockfill materials are used to verify the model. The results indicate a good agreement between the model predicted results and experimental results. Besides, the deteriorated stress and deformation characteristics of rockfill materials after cyclic wetting-drying are predicted by the theoretical model.

Soil and Rockfill Dams Safety Assessment for Henan Province: Monitoring, Analysis and Prediction

It is of great significance to explore the spatial and temporal evolution of soil and rockfill dam deformation, ensuring the safety of people’s lives and healthy economic development. The spatial and temporal evolution patterns of deformation of 17 large soil and rockfill dams in Henan Province were analyzed by using the PS-InSAR technique and 55 Sentinel-1A images from March 2017 to September 2021. Based on factors such as reservoir water level and rainfall, a series of analyses were conducted on the Xiaolangdi soil and rockfill dam, which has the highest dam height and the most prominent deformation problem. The monitoring results show that all the soil and rockfill dams in Henan Province have different degrees of deformation, and there is a close relationship between dam height and deformation. In addition, the deformation rate of the Xiaolangdi soil and rockfill dam in the past five years presents a “Stepped Shape” deformation trend from the top to the bottom of the dam. The deformation of the upper, middle, and lower parts of the dam body reaches 80 mm, 40 mm, and 20 mm, respectively, among which the middle part of the dam crest has the largest deformation. Furthermore, the time series prediction model for sparrow search algorithm Long Short-Term Memory considering the moving average filter (MAF-SSA-LSTM) is proposed to predict and accurately analyze the future deformation of Xiaolangdi soil and rockfill dam with RMSE of 1.526 mm, MAE of 1.447 mm, and MAPE of 2.22%, which proved that the model has high prediction accuracy. It can truly reflect the overall deformation trend of the dam body. The results provide a theoretical basis and decision basis for the census of reservoir safety conditions and deformation history retrieval in Henan Province.

Global sensitivity analysis of parameters based on sPCE: The case study of a concrete face rockfill dam in northwest China.

To effectively identify the key material parameters of different zones of concrete face rockfill dams and improve the efficiency of parameter optimization, a global sensitivity analysis method of parameters based on sparse polynomial chaotic expansion (sPCE) is proposed in this paper. The latin hypercube sampling method is used to select multiple groups of material parameters, and then finite element method is used to calculate the displacement of dam characteristic nodes in dam body. On this basis, the displacement is expanded by sPCE, and the polynomial basis function is reconstructed by orthogonal matching pursuit to improve the construction and analysis efficiency of the proxy model. According to the chaos coefficients, Sobol' indices are calculated to evaluate the influence of the material parameters and their interaction on different displacements of the dam. The results show that the sPCE model can accurately simulate dam displacement and its statistical characteristics with a relatively small sample size. The sensitivity of the same parameter has spatial variability, and under the influence of parameter levels and spatial distribution of different materials, the parameter sensitivity ranking of different zones has certain differences. The proposed method provides a new reference to sensitivity analysis and uncertainty analysis for practical engineering.

Late-stage diversion risk assessment for high dams considering early initial impoundment: a case study of Lianghekou Station, China

Early initial impoundment can generate additional revenue but bring more flood risk in late-stage construction diversion. In view of the possible flood risk and catastrophic consequences caused by high dam failures induced by early impoundment, a comprehensive assessment is proposed. Taking the Lianghekou high rockfill dam on the Yalong River, southwest China, as an example, this study established the late-stage diversion risk model and predicted the failure probabilities for the original, 15 days ahead, and 30 days ahead schemes varied with the initial impoundment time using the Monte Carlo method. Then, considering overtopping-induced gradual breaking of rockfill dams, the NWS dam-break flood forecasting model (DAMBRK) was used to estimate the break development and the outflow hydrograph. Due to no significant differences being found in the outflow hydrographs of the three schemes, life loss was used an index for the consequences of inundation. Combining the failure probability, life loss, and early impoundment revenues brought by earlier power generation, a satisfied initial impoundment scheme was acquired using the multi-objective decision model. The results revealed this method can find a reasonable initial impoundment time in view of the late-stage diversion risk assessment.

Dynamic evaluation method for Time-variant reliability of structural safety of Concrete-faced rockfill dam

The evaluation of the structural safety risk for concrete-faced rockfill dams (CFRDs) is susceptible to the time-varying parameters and the environments of topography, geology, and operations. Traditional evaluation methods, due to their involvement in numerical simulation, cannot meet the current requirements for intelligent monitoring in terms of timeliness and practicality. Therefore, a dynamic evaluation method of reliability in CFRDs is proposed in this paper. Due to the nonlinear mapping relationship between the time-variant reliability and the monitoring characterizations of CFRDs, the long and short-term memory neural network (LSTM) and support vector machine (SVM) models are introduced to construct the potential functional relationships between the reliability sequences and the monitoring characterizations, and the matching between the accuracy of the two models and the frequency of monitoring characterizations has been fully studied, forming an adaptive evaluation model of safety risk for the CFRDs according to the different monitoring frequencies of different monitoring items. The application of Sanbanxi CFRD shows an average relative error of less than 1% and 5% for dam slope stability and slab cracking simulations, respectively. These results demonstrate that the LSTM and SVM models with adaptive monitoring frequency exhibit high fitting and prediction accuracy and applicability, and possess theoretical and engineering application value.

Relationship between Porosity and the Modified Constitutive Model Parameters of Asphalt Concrete Core Material

Porosity is a key control index for ensuring the compaction quality of rockfill dams with asphalt concrete cores. The porosity of the asphalt mixture is an important factor for an asphalt concrete core dam to obtain adequate strength and control the core deformation. However, the compaction quality (i.e., porosity) of the asphalt core wall inevitably exhibits spatial differences during actual construction process. To analyze the quantitative relationship between the porosity of the asphalt concrete core and the Duncan-Chang model parameters, triaxial tests under different confining pressures were carried out with asphalt concrete samples of different porosities. Based on the test results, the applicability of the Duncan-Chang model was assessed. Aiming at the limitation of the Duncan-Chang model, which is unable to characterize the strain softening and shear dilatancy of materials, a modified constitutive model of the asphalt concrete core was proposed. The determination method of the proposed model parameters was provided and verified by triaxial test results. A regression relationship was established between the porosity of the core material and the parameters of the modified constitutive model. This study provides a prerequisite for conducting refined finite element analysis on the mechanical performance of the asphalt core rockfill dams, taking into account the spatial differences in compaction quality of the asphalt concrete core.

Selection of efficient earthquake intensity measures for evaluating seismic fragility of concrete face rockfill dam

This study explores the crucial role of intensity measure (IM) selection for probabilistic seismic demand model development of concrete face rockfill dam (CFRD) subjected to earthquake ground motions. Nonlinear dynamic analyses are performed for CFRD with an advanced hysteretic soil model using a finite element analysis program to develop a database of earthquake-induced dam crest settlements. The numerical model is validated through centrifuge model test measurements. A selection process was carried out to evaluate the IMs based on the goodness of fit, as well as their efficiency, practicality, and proficiency. Eventually, a range of optimal IMs are selected. Conditional probability function is employed to develop fragility curves for CFRD employing both scalar and vector IMs. Five settlement ratio-based limit states are defined herein. The results show that vector fragility surfaces produce enhanced predictions of the dam damage compared with the scalar fragility curves that are most often employed.

Static and Pseudo Static Analysis of Embankment Slope Stability of Bener Dam, Purworejo Regency, Central Java

The Bener Dam is considered as one of the largest rock-fill dams in Indonesia. This dam will impact the inundation area of three main villages in the Wonosobo and Purworejo regency. Since this zoned embankment dam consists of rock-fill and the core material, the stability of the dam slope has to be done to ensure that the dam is stable against any failures including the seismic effects. Moreover, the seismic coefficient in the study area in the seismic analysis of the large dam slope is needed to be used in the analysis which is not yet done from the previous studies. This paper presents the analysis of the embankment slope stability of the Bener dam under static condition and pseudo static condition. The analysis takes into account the end stage of construction, the steady-state stage, and rapid drawdown stage. The results of utilizing the Finite Element Method to analyse the slope stability demonstrates that the dam embankment slopes are stable under static and seismic stress conditions in all the reservoir condition stages. After applying the seismic loading, the result of safety factor of slope stability is reduced while the rapid drawdown stage has the lowest safety factor.

The Use of Shape Accel Array for Deformation Monitoring and Parameter Inversion of a 300 m Ultrahigh Rockfill Dam

The global construction of rockfill dams has now surpassed the 300 m height level. Despite great achievements in dam design and construction, monitoring techniques have lagged behind the development of high rockfill dams. Existing deformation monitoring techniques are ill-suited to the high earth and water pressures, and extended monitoring periods are required for ultrahigh rockfill dams. This study introduces, for the first time, the use of a shape accel array (SAA) to monitor internal displacement in a 300 m high earth core rockfill dam. The SAA employs a rope-like array of capacitive MEMS accelerometers for deformation measurement. Compared to conventional monitoring techniques, SAA is a data-intensive monitoring technique. Based on the intensive data obtained from SAA, we employed a parameter inversion method, utilizing multiobjective optimization algorithm, the nondominated sorting genetic algorithm-III (NSGA-III), to inverse the constitutive model parameters of the rockfill dam. The multiobjective parameter inversion method maximizes the use of multisource monitoring data for predicting rockfill dam deformation.

Improved measuring plate solution method of density for rockfill dam based on the additional -mass model

Density control is the key index of quality control during the rockfill-construction period. Normally, traditional pits method used in rockfill-construction has several disadvantages, such as long test time, high manpower consumption, etc. Therefore, it will bring great interference to the construction progress. The new additional mass method has been widely used with advantages, such as fast test speed, no damage to dam body, etc. However, there are some shortcomings in the solution of added-mass method at present, such as limited test range, unclear theoretical basis and so on. In this paper, a new method of digital measurement plate construction is proposed. Firstly, the process of solving the density of prototype rockfill materials(PRFM) was described based on the equation-equivalence method. Then, two kinds of measurement plates were made by constructing parameter-equivalence diagrams. The validity of the method is verified by comparing test results and pit-test results in several different parts of the Shuangjiangkou dam. The new method is easy to calculate and the parameters could be equaled flexibly. Moreover, comparing with the previous digital measurement plate method, the new one has advantages, such as easier to be expanded and having a wider test range.

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.

Predicting the deformation behaviour of concrete face rockfill dams by combining support vector machine and AdaBoost ensemble algorithm

The accurate evaluation of deformation behaviour is very important to the optimal design and safety evaluation of concrete face rockfill dams (CFRDs). Deformation prediction is a key problem in the CFRD construction. Based on statistical review of typical deformation behaviour of 94 CFRD cases, the relationship amongst three typical deformation indexes and six influencing factors of CFRDs is analysed using multiple linear regression method. The main influencing factors of the dam behaviour are discussed. An improved support vector machine (SVM) dam deformation prediction model is proposed based on the construction of an adaptive hybrid kernel function. The particle swarm intelligent optimisation algorithm is used to determine the main parameters. To solve the problem of nonlinear mutation and discreteness of case data, the SVM-AdaBoost prediction model of typical deformation indexes is established by iterative optimisation of the basic learner composed of the improved SVM model through the AdaBoost strategy. The comparative analysis of the proposed model and existing models shows that the proposed model has good prediction accuracy and can be used to predict the typical deformation behaviour of CFRDs accurately.

Assessment of Foundation Rocks of the Proposed Makhol Dam in the Northern Salah- Alddin, Iraq

This study was done as an assessment of the foundation rocks of the proposed Makhol dam in the northern Salah- Aiddin Governorate, Iraq. This study consists of field, laboratory, and office work. It was noticed in the field that the thirteen (13) different rock mass units comprised along the dam axis. Three rock mass classification systems were adopted (used) in the evaluation: Rock Mass Rating, Dam Mass Rating, and Geological Strength Index. The DMRSTA (RMR related to dam stability) values for the right bank range between 36.97- 73.8. These values indicate good stability of foundation rocks of the right part with the presence of some instability of primary effect (not serious effect) in unit no.3 (Fatha Formation), and the DMRSTA values of the left bank range between 44.97– 61.7 These values indicate no instability for the foundation rocks on the left bank for all rock mass units. The RMRBD89 values range between 37– 73.3. These values reveal that the foundation rocks are desirable and can be excavated for rockfill and earth fill dams, but for the gravity dam, the rock mass unit 3, must be excavated to the desirable RMRBD89 value in the case of a gravity dam, and indicate that the foundation rocks do not require grouting when the type of dam is earth fill. Some rock mass units require grouting (spot grouting), especially for the rock mass unit 3 when the type of dam is Rockfill, and require systematic grouting, especially when the type of dam is Gravity. The Roc Lab software was used for the purpose of determining the mechanical properties of all rock units through the Hook-Brown failure criterion.

Numerical simulation of the anti-freezing performance of a phase change clay core-wall with loose covering

Clay core-wall of rockfill dam may endure short-term freezing or freeze–thaw cycles owing to negative temperature conditions during winter construction in cold regions, resulting in the degradation of the clay compaction, frost swelling, and cracking performance. The most commonly used insulation cover measures interfere with the continuous construction of clay core-walls, which may shorten the effective time available for construction and delay the dam construction progress. To address this problem, we proposed using the upper layer of the loose-covering clay and the latent heat of phase change materials (PCMs) to control the core-wall temperature. We implemented a numerical model for simulating the anti-freezing performance of the PCM mixed clay (PCM-clay) with loose covering. First, a heat transfer model was established using the finite element software COMSOL, and the effectiveness of the model was verified by comparing it with indoor temperature control test results. Subsequently, numerical models including different construction conditions were established, and the temperature control effect was analyzed under different loose-covering thicknesses, initial soil temperatures, and PCM contents. The results showed that at the design ambient temperature and a 2% PCM content, an effective construction time availability of two consecutive days was maintained under a 20-cm-thick loose covering. In contrast, under the same temperature conditions, but for a 4% PCM content, the effective construction time available under a 5-cm-thick loose covering was 43.1 h. Thus, the use of PCM-clay combined with the upper layer loose covering for temperature control proved feasible and effective. Additionally, by increasing the thickness of the loose covering and the initial temperature of the PCM-clay, the PCM content can be reduced. This provides a theoretical basis and a potential technical solution to maximize the time available for construction and accelerate the construction progress of core-wall rockfill dams.

High-Precision Measuring System for Internal Deformation Monitoring Pipeline of Rockfill Dams: Design and Validation

The monitoring of internal deformation in rockfill dams using pre-buried flexible pipelines is a promising technique; however, achieving precise measurements over a long-range pipeline is crucial and challenging. In this paper, we present a high-precision pipeline measuring system for monitoring internal deformation in rockfill dams, which can simultaneously measure the pipeline centerline and cross-section geometry. The system leverages the inertial measurement principle to perform positioning by fusing an inertial measurement unit (IMU) with odometers. It utilizes a Kalman filter and Rauch-Tung-Striebel (RTS) smoothing to estimate the optimal 3D curves of the pipeline. The pipeline’s inner diameter is measured using three wheel swing arms and a set of load-bearing wheels, and the pipeline cross-section geometry is fitted using a direct least-square ellipse fitting approach. Finally, we validated the measuring system through both model and on-site experiments and compared the measurements with the Leica AT-960LR absolute tracker and hydraulic overflow settlement gauge. The results indicate that the measuring system has excellent accuracy for measuring pipeline curves and deformation, and the settlement trend is consistent with the hydraulic overflow settlement gauge. We also assessed the cross-section deformation of the deformation monitoring pipeline in the Lianghekou dam for six months, and the results showed that if deployed in strict accordance with the design requirements, the monitoring pipeline buried inside the rockfill dam would not deform significantly. These findings provide a tremendous incentive for the continued development of rockfill dam internal deformation monitoring.

Seismic Response of a Rockfill Dam with an Asphalt–Concrete Core under P Waves with Arbitrary Incident Angles

The incident angles of seismic waves have a significant influence on the seismic response of asphalt–concrete core rockfill dams. This paper constructs the free field of elastic semispace under P waves with arbitrary incident angles and clarifies the variation law of the seismic intensity on the ground surface with incident angles γ and α. The free field on the foundation boundary under arbitrary combinations of angles γ and α are derived according to the wave-field superposition principle. Combined with the viscoelastic artificial boundary, the free field is transformed into the equivalent load on the boundary node, and the input method of the P wave with arbitrary incident angles is established. Finally, the seismic response of the asphalt–concrete core dam under P waves with arbitrary incident angles is studied. The results show that when the incident direction is perpendicular to the dam axis, the dynamic shear stress is the highest, and the local seismic safety factor of the dam is the largest. When the incident direction is parallel to the dam axis, the tensile stress of the asphalt core is the highest, there is a possibility of cracking at the contact part of the lower part of the asphalt core with the canyon, and the seismic subsidence rate of the dam crest is the highest. For the tensile stress of the asphalt core and the dam-crest subsidence rate, the most unfavorable incident angle α is 75° when the incident angle γ is the same.

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.

Temperature tracing test and numerical simulation study during leakage of earth-rock dam

The leakage of earth rock dams exhibits characteristics of space-time randomness, concealment, and significant destructiveness. Prompt detection and identification of dam leakage are critical to ensuring the structural safety of these constructions. The distributed optical fiber temperature measurement method, which is based on optical frequency domain reflection (OFDR) technology, possesses attributes such as high spatial resolution, minimal temperature error, short response time, and real-time monitoring. As a result, it is an ideal technique for experimental research on leakage monitoring of earth rock dams. In this study, a model test was conducted on a clay core rockfill dam to investigate the feasibility of utilizing distributed optical fiber for identifying dam leakage. The variation pattern of partial distributed optical fiber temperature measurements in the dam body under the leakage state was compared and analyzed using the gradient method and the thermal pulse method. Furthermore, the heat flow coupled numerical simulation method was employed to verify and expand the findings of the indoor tests. The results of this study indicate that the OFDR distributed optical fiber leakage monitoring method using the thermal pulse approach can entirely reflect the temperature changes that occur during leakage, thereby providing strong reliability and exhibiting considerable potential for leakage location. The study offers valuable insights and a reference for the practical use of distributed optical fiber to monitor earth rock dam leakage.

Study on stress-deformation mechanism of concrete face rockfill dam based on centrifugal model test

The traditional method of tracking the deformation of centrifugal dam model involves burying marker points on the sidewalls, which is commonly used. However, the method is inaccurate in monitoring the deformation of the model since the constraining effect of boundary effect on the model. In this study, a quasi-distributed fiber optic monitoring system was constructed using fixed-point distributed fiber Bragg grating. Particle image velocimetry, earth pressure cell, and other electromagnetic sensors were combined to examine the rationality of the face rockfill dams centrifugal model tests. Through comparative analysis, the applicability and stability of the fixed-point distributed FBG technique in the centrifugal model test were demonstrated. It is also demonstrated that traditional monitoring methods will underestimate the deformation of face rockfill dams by 2.32 % ∼ 13.55 %. This study addresses the shortcomings of existing monitoring methods with excessive measurement errors and provides a more applicable monitoring tool for developing related experimental studies.