Concrete Dams Research Articles

Study of Damage Mechanism and Evolution Model of Concrete under Freeze–Thaw Cycles

Researching the mechanical characteristics of concrete subjected to the freeze–thaw cycle is crucial for building engineering in cold climates. As a result, uniaxial compression tests were performed on concrete samples exposed to various freeze–thaw (F–T) cycles, and the measurements of the pore size distribution, porosity, and P-wave velocity of the saturated concrete samples were obtained, both before and after being exposed to the F–T cycles. Concrete’s F–T damage mechanism and damage evolution model were thoroughly examined. Using rock structure and moisture analysis test equipment to observe the T2 spectrum, the results showed that the F–T cycles can cause the internal structure of the samples to deteriorate. Porosity and F–T cycles have a positive correlation, although P-wave velocity has a negative correlation with the F–T cycles. As the F–T cycles increased, the specimens’ peak strength and elastic modulus steadily declined, while the peak strain clearly exhibited an increasing trend. A microscopic F–T damage model that takes into account the pore size distribution was developed, based on the relative changes in the pore structure distribution (PSD), before and after the F–T cycles. The concrete sample damage evolution law under various F–T cycles was examined using the following metrics: total energy, pore size distribution, static and dynamic elastic moduli, porosity, and P-wave velocity. Uniaxial compressive strength (UCS) and peak strain tests were used to evaluate the accuracy of the pore size distribution damage model, as well as that of five other widely used damage models.

Seismic evaluation of concrete gravity dam under the effect of far and near field earthquakes considering dam saturation

Seismic evaluation of concrete gravity dam under the effect of far and near field earthquakes considering dam saturation

A multipoint prediction model for the deformation of concrete dams considering climatic features of high-altitude regions

High-altitude regions are characterized by natural climatic features such as low temperatures and high radiation. Concrete dams built in these regions face more complex operating conditions. Traditional single-output deformation prediction models ignore the correlations between different monitoring points, making it difficult to assess the overall deformation behavior of concrete dams. The black-box nature of some machine learning models can lead to a lack of interpretability, affecting the practical application. Therefore, a multipoint prediction model (MPM) is proposed to analyze the deformation behavior of concrete dams in high-altitude regions. Firstly, the deformation monitoring points are divided based on the climatic features of high-altitude regions. Subsequently, the MPM is constructed using the multi-output CatBoost model and Quasi-Monte Carlo algorithm to achieve deformation prediction across different partitioned monitoring points. Finally, the elucidation of the MPM optimization procedure in a transparent manner alongside the quantification of the influence exerted by input variables on output outcomes notably augments the interpretive capacity of the MPM. The proposed model is validated using monitoring data from a concrete dam in a high-altitude region. The disparities in chaotic and entropy variation features among deformation monitoring points in different zones corroborate the appropriateness of the zoning in this study. Comparisons between the single-output CatBoost model and MPM verify the feasibility and efficiency of multipoint predictions. Comparisons with other multi-output prediction models validate the superior predictive performance of the MPM. Additionally, the proposed model's generalization performance is validated using data from another concrete arch dam in high-altitude regions.

Flexural behavior of high-strength steel-precast prestressed concrete composite beams with grouped demountable bolts under hogging moment

To study the bending behavior of high-strength steel (HSS)-precast reinforced concrete (PRC) slab composite beams with grouped demountable bolts under hogging moment, single-point loading tests were carried out to evaluate the bending behavior of the five prefabricated composite beams, and the key parameters are shear connection degree, shear pocket spacing in the PRC slab, and applying precompression to the concrete or not. The test results indicate that the HSS composite beams have good overall bending behavior, and two failure modes are recorded including the flexural failure, and the concrete damage in the shear pocket region. The prestressing force can effectively increase the anti-cracking performance of the slab and slightly improve the bending behavior, while increasing the shear connection degree from 1.80 to 3.61 or the shear pocket spacing from 360 mm to 800 mm (the limit value in the AASHTO LRFD Bridge Design Specifications is 610 mm) under the same shear connection degree has a limited influence on the bending behavior, and the composite beams still have the effective composite action. The existing formulas are conservative in calculating the bending capacity of HSS composite beams but have a high degree of consistency in stiffness.

AI-assisted ultrasonic wave analysis for automated classification of steel corrosion-induced concrete damage

Early detection of cracks in reinforced concrete caused by chloride intrusion is crucial for effective maintenance. This paper develops and compares AI-assisted models that use ultrasonic pulse waves to automatically assess early-stage concrete damage, particularly cracks caused by steel corrosion. Data were collected from 108 concrete cubes with various mixture designs, cover depths, and steel corrosion levels induced by the impressed current technique. The AI models, particularly convolutional neural networks (CNNs), outperformed traditional regression models, achieving up to 84% classification accuracy. The systematic and automated features of the AI-assisted algorithm enable reliable, consistent and rapid ultrasonic wave data analysis, which is especially beneficial for the condition assessment of large infrastructure systems. This advancement inspires further research into integrating automated IoT and robotics-assisted systems for comprehensive infrastructure monitoring.

Ultrasonic diagnostics of concrete destruction under the influence of corrosion environment

Introduction. Modern methods of studying the corrosion damage of concrete are quite lengthy and time-consuming, which makes their use difficult. This necessitates the search for new approaches to study the destruction of concrete under the influence of aggressive media. Currently, the ultrasound diagnostic method is effectively used to identify various structural defects, but the possibility of its use for concrete corrosion studies is poorly understood. This work is devoted to filling this gap.The methods of research. Concrete samples of 2.5x2.5x10 cm and 2.5x2.5x16 cm of various composition (cement: placeholder = 1:9, 1:7, 1:5). The control samples hardened under normal conditions, the test samples were stored in various aggressive environments. The samples of all storage media were subjected to periodic tests on the Pulsar-2.2 ultrasound diagnostic device. In parallel, the strength parameters obtained by the destructive method on the PGM-100MG4 hydraulic press, as well as the resistance coefficient, were determined.Results. The relationship between the growth periods, extremes and abrupt changes in the velocity of passage of ultrasonic waves and the stages of strength gain, the conditions of hardening of samples, and time factors has been established. It is shown that ultrasound diagnostics is quite sensitive to the processes caused by the corrosion destruction of concrete and allows us to obtain reliable data, while the strength and coefficient of resistance do not always adequately reflect the development of corrosion processes. It has been established that the use of ultrasound diagnostics makes it possible to increase the reliability of the results of concrete corrosion studies.Conclusion. The use of the ultrasound diagnostic method enables to obtain new data on the processes of concrete destruction under the influence of aggressive media, which makes it possible to increase the reliability of the results of concrete corrosion studies.

A portable real-time concrete bridge damage detection system

A drone detection system can achieve real-time inspection of concrete bridge damage. However, it is difficult to deploy existing detection algorithms on a portable system due to their high computational cost. Therefore, a portable damage detection algorithm called CD-YOLOv8 is designed. CD-YOLOv8 is operated on Jetson Xavier NX to detect drone-captured bridge images in real-time. The multi-scale feature adaptive fusion module is used to reduce model parameters and improve detection speed. The spatial context pyramid and deformable convolutional structure are introduced to improve the detection accuracy of tiny concrete bridge damage. Compared with the YOLOv8n, the mAP50 of CD-YOLOv8 is increased by 3.6 %, while the model parameters and FLOPs are decreased by 0.05 M and 0.7 G, respectively. CD-YOLOv8 is also tested on the Jetson Xavier NX with a detection speed of 44 FPS, which is 15.79 % faster than the YOLOv8n. Therefore, CD-YOLOv8 has high accuracy and excellent real-time performance.

Multifractal of acoustic emission for the multi-scale fracture behavior of diatomite modified concrete

It has been attempted to determine how supplemental cementitious materials (SCMs) affects concrete's resistance to fracture. Nevertheless, acoustic emission (AE) has not been used to investigate the impact of diatomite, an SCMs, on the fracture characteristics of concrete. In this investigation, the aim was to assess the fracture behavior of concrete with variable loadings of diatomite (0 %, 1 %, 2 %, 3 %). Three-point bending is performed along with continuous AE monitoring for concrete with various contents of diatomite to obtain AE information. The fracture behavior (fracture parameters, fracture mode, multi-scale fracture and damage) is determined by analyzing AE parameters and corresponding statistical indicators such as Multifractal Detrended Fluctuation Analysis(MF-DFA) and Weibull theory. The results show that the addition of diatomite enhances the fracture property of concrete especially the optimal 2 % content. Then, the high RA value and tensile crack ratio suggest the improvement of the tensile resistance of diatomite. Moreover, a novel quantitative index called multifractal parameter is proposed to evaluate the multi-scale fracture. The finding contributes to a novel method for quantifying multi-scale cracking. The low multifractal parameter in diatomite modified concrete implies a small cracking scale in comparison with the ordinary concrete. Finally, the presence of diatomite slowed down the development of fracture damage in concrete.

Study on fragmentation characteristics of carbon nanotube-enhanced concrete and a comparative evaluation of the ZWT and ottosen constitutive model

In order to study the difference between the crushing characteristics of carbon nanotubes (CNTs) concrete and ordinary concrete, this paper conducts a test between ordinary concrete and CNTs concrete with a volume content of 0.3 % at different impact speeds through the Hopkinson test, using fragmentation and particle size distribution as evaluation indexes. Crushed fragments are analyzed from the perspective of concrete pores. Finally, the nonlinear viscoelastic constitutive model and the nonlinear elastic constitutive model of CNTs concrete are then developed and compared. Based on the results, the average pores of the CNTs concrete decreased from 42.0 nm to 38.0 nm, but the pore area increased from 5.743 m2/g to 6.305 m2/g, indicating that CNTs can fill the internal pores. Meanwhile, the average particle size of broken CNTs concrete is significantly larger than that of ordinary concrete. However, the relationship between the crushing particle size and impact velocity is approximately y=A-Bln(x+C) for both concretes. According to the study of concrete constitutive models, compared to the Loand damage model, the combination of Loand model and Mazars model is more accurate in describing concrete damage characteristics, and the average correlation coefficient increases from 0.84 to 0.92. Meanwhile, compared to the Zhu-Wang-Tang (ZWT) model, Ottosen model can better capture the dynamic mechanical properties of CNT concrete, with a correlation coefficient over 0.98.

Electrical characterization of freeze-thaw damage in saturated concrete and its interfacial transition zones

Determining the freeze-thaw (F-T) damage of the interfacial transition zone (ITZ) is crucial to understanding the mechanism of F-T in concrete and improving its frost resistance. In this paper, the F-T damage of saturated concrete/mortar and ITZ is characterized using AC impedance spectroscopy, and the micro-mechanisms of F-T damage in cement-based materials (CBMs) are summarized. Firstly, the damage factor was defined by the effective resistivity of the CBMs, and a correlation between the damage factor and the compressive strength loss was established. The F-T damage process was divided into a damage development stage and a damage stabilization stage based on the damage factor and fractal dimension. Then, the effective resistivity separation formula was proposed to calculate the ITZ effective resistivity, and the ITZ damage factor was calculated for non-destructive quantitative characterization of the F-T damage in the ITZ. Finally, the microscopic mechanism of F-T damage in CBMs and their ITZs was summarized based on damage factor, fractal dimension, super depth of field microscopy, and nanoindentation. The results showed a linear relationship between the damage factor and compressive strength loss (Lc = 0.176Er+0.030); the ITZ had damage factors of 80 % and 70 %, which were 1.6 and 1.4 times higher than those of the matrix, respectively; F-T cycles produce micro-damage, part of which connects with the disconnected pores to form connected pores, the micro-damage extends and accumulates along the surface of the aggregates, leading to ITZ debonding from aggregate and deterioration of the mechanical properties.

Trends and opportunities for greener and more efficient microbially induced calcite precipitation pathways: a strategic review

Microbially induced carbonate precipitation (MICP) is extensively used for soil stabilisation, sand erosion control, bioremediation and concrete repair. However, detailed bibliometric studies on MICP are scarce, particularly regarding industrial feedstocks, such as urea for ureolytic bacteria and calcium chloride, and the associated ammonia gas production, which poses challenges for large-scale applications. This study reviews 857 articles from the Scopus database (2000–2024), using the VOSviewer software to visualise data on publications, citations, authors, countries, journals, trending keywords and research topics. Significant global collaboration is evident, led by China and the USA. The most cited papers discuss ureolytic microorganisms enhancing soil properties, the basic MICP process, reducing concrete damage, improving soil and groundwater systems and the impacts of MICP on urea hydrolysis and ammonia production. Key terms such as ‘calcium carbonate’, ‘ammonia’ and ‘Sporosarcina pasteurii’ are central to MICP research. Co-occurrence analysis highlights thematic clusters such as microbial cementation and geological features, emphasising the multidisciplinary role of MICP in tackling environmental problems. This review highlights the need to mitigate environmental impacts, particularly those of ammonia production and energy use, in ureolytic MICP. Life-cycle assessments reveal that while ureolytic MICP reduces carbon dioxide emissions, it often consumes more energy, necessitating alternative nutrient sources and cost-effective practices for large-scale applications.

Evaluation of compressive damage in concrete using ultrasonic nonlinear coda wave interferometry

This study investigates the feasibility of nonlinear coda wave interferometry (NCWI) for evaluating compressive damage in concrete, with a particular focus on the interference caused by the compressive stress-induced slow dynamics. Slow dynamics refers to a phenomenon in which the stiffness of concrete immediately decreases after moderate mechanical conditioning and then logarithmically evolves back to its initial value over time. A series of experiments were conducted to validate this concept. The experimental findings indicate that slow dynamics following the unloading of concrete specimen significantly interfere with NCWI testing. The changes in dv/v caused by the slow dynamics are opposite to those induced by the pump wave in NCWI. After the slow dynamics have been eliminated, an evaluation indicator, defined as the efficient nonlinear level αdv/v, demonstrates an excellent correlation with compressive damage. The value of the indicator decreases with increasing compressive stress. Furthermore, the coda wave interferometry (CWI) and direct wave interferometry (DWI) are performed as comparisons. In summary, the feasibility and superiority of NCWI are demonstrated in concrete compressive damage evaluation.

Experimental investigation on dynamic response of concrete gravity dam under shock wave and bubble pulsation

The main components of underwater explosion loads are the shock wave and bubble pulsation. However, there are few studies on the combined effects of shock wave and bubble pulsation on the dynamic response of concrete gravity dams (CGDs). In this study, a 1:100 scaled-down model of a CGD was designed, and ten tests were conducted. The load characteristics of the shock wave and bubble pulsation, and the acceleration and velocity time histories of the CGD caused by underwater explosions were recorded. The distribution laws of peak acceleration and velocity in the CGD due to shock wave and bubble pulsation were analyzed. Additionally, the influence of standoff distance, explosive weight, and detonation depth on the dynamic response of the CGD was systematically discussed. The study also explored the mitigation effects of bubble curtain on the CGD’s response to underwater explosion. Findings reveal that the peak pressure generated by bubble pulsation represents approximately 10.41–15.03 % of that by the shock wave, and the impulse from the bubble pulsation is nearly equivalent to that of shock wave. Contact or near-field explosion shock wave induces a strong local response in the dam, with maximum acceleration occurring directly opposite the detonation. In contrast, the shock wave causes the overall response of the dam during far-field explosion, with maximum acceleration at the junction between the dam head and body. Bubble pulsation predominantly affects the dam’s overall response. The average ratio of peak acceleration induced by bubble pulsation to that induced by shock wave is 4.69–17.11 %, and the average ratio of peak velocity ranges from 13.08 to 36.27 %. The response of the CGD caused by the explosion suspended in water is notably greater than that caused by a bottom explosion. Bubble curtains can reduce peak acceleration due to shock wave by 93.8–97.26 %, and almost completely shield against bubble pulsation.

Experimental study on overtopping failure of concrete face rockfill dam

With the frequent occurrence of natural disasters, the problem of dam failure with low probability and high risk has gradually attracted people's attention. This paper uses flume model tests to systematically analyze the overtopping failure mechanisms of concrete face rockfill dam (CFRD) and identify its failure modes. The tests reveal that the longitudinal erosion of the CFRD breach progress through stages of soil erosion, panel failures, and water flow stabilization. Meanwhile, the cross-section breach process involves the evolution of breach size in rockfill materials, including traceable erosion, lateral broadening, and breach morphology stabilization. The fracture characteristics of the water-blocking panel are primarily evident in the flow-time curve. By analyzing the breach morphology evolution processes in longitudinal and cross sections, the flow-time curve can be subdivided into stages of burst flow formation, breach expansion with flow increase, rapid increase of breach flow discharge due to panel failures, and stabilization of breach flow and size. The primary damage process of the CFRD occurs in a cyclical stage of breach expansion, flow increase, panel failure, and rapid discharge. The rigid face plate and granular body structure contribute to partial dam failure, showing a tendency for gradual expansion of the breach. The longitudinal section illustrates dam failure resulting from panel fracture and rockfill erosion interaction, while downstream slopes exhibit failure due to lateral intrusion of rockfill and cyclic instability. These research results can serve as a reference for constructing a concrete CFRD failure prediction model and conducting disaster risk assessments.

Temperature Control and Crack Prevention of High RCC Dam in Cold and Drought Area

A development process is introduced for a computation program to calculate the temperature and stress field of mass concrete based on the ANSYS® platform. The temperature control scheme of a high roller compacted concrete (RCC) dam in northern Xinjiang is optimized by using the simulation program. It is suggested that the concrete pouring temperature of the dam should not exceed 16°C and that water-pipe cooling should be adopted. The dam should be permanently heat preserved by 10 cm thick extruded polystyrene (XPS) extruded panels, and the top surface of the overwintering layer should be covered with an at least 14 cm thick thermal insulation quilt. During construction, the warehouse surface should be temporarily insulated with a 2 cm thick thermal insulation quilt. The causes of cracks in a particular dam section are simulated and analysed, and it is concluded that the cracks are mainly caused by the lack of thermal insulation of the warehouse surface during cold spells.

Deep learning model for the deformation prediction of concrete dams under multistep and multifeature inputs based on an improved autoformer

The long-term prediction of deformation in concrete dams is a critical requirement for maintaining their structural integrity over time in practical management scenarios. While most existing models predominantly address short-term and medium-term predictions, there remains a significant challenge in establishing reliable correlations within complex long-term temporal patterns and varying environmental factors. Consequently, there is limited research on multistep prediction. To solve these problems, an Autoformer-based model for multistep and multifeature dam deformation prediction is proposed. In the proposed model, the sequence decomposition of dam monitoring data is used as the basic construction module inside the depth model. Then, Deep Automatic Correlation (Deep-AutoCorrelation) mechanism is employed to obtain the long-term dependence between dam deformation and environmental load. The encoder-decoder structure integrates time series decomposition and the Deep-AutoCorrelation to predict the multistep deformation of the dam. In the multistep deformation prediction of the dam, the improved Autoformer model demonstrates state-of-the-art performance, resulting in a 48% increase in prediction accuracy across five monitoring point datasets when compared to six benchmark models. Experimental results indicate that this method effectively addresses the challenge of predicting long-term deformation of dams subjected to complex environmental loads. It demonstrates robust capabilities in extracting long-term temporal features and avoids the increase of computational complexity caused by deeper time extraction.

Effects of Macro Fibers on Crack Opening Reduction in Fiber Reinforced Concrete Overlays.

Macro fibers have been extensively used in the construction of various concrete structures, including bridges, dams, tunnels, industrial floors, and pavements. However, their effectiveness in reducing crack opening widths in concrete pavements has not been fully explored. This study aims to delineate the role of fibers by identifying the optimal types and volumes for effectively controlling cracks in concrete pavement structures, particularly in thin overlays. The research investigates how different fiber types, such as synthetic and steel, and their respective volumes can mitigate crack propagation in concrete overlays. Additionally, it evaluates the performance of fiber-reinforced concrete overlays compared to conventional dowel bar systems in terms of crack width reduction and overall pavement durability. The findings aim to provide specific design criteria for incorporating macro fibers in concrete overlays to enhance structural integrity and longevity.

Automated ultrasonic scattering energy method for evaluation of small-sized cracking damage in concrete

The aim of this study was to develop an automatic ultrasonic scattering energy method (USEM) to evaluate small-scale damage to concrete. The automated system measured Leaky Rayleigh waves from the specimens. Herein, the energy of the scattering portion of waves caused by cracks was extracted using a 2D Fourier transform. USEM has the advantage of detecting cracking damage smaller than the applied ultrasonic wavelength, which is problematic when conventional ultrasonic methods are applied to concrete. The proposed methodology was evaluated using laboratory-scale specimens and a concrete bridge exposed to freeze–thaw cycles in the field. The results of the extracted scattering energy demonstrated that the USEM is sufficiently sensitive to detect and localize subwavelength damages of 0.05 mm in concrete. Furthermore, the proposed USEM was compared with conventional ultrasonic pulse velocity with respect to the accuracy of damage detection.

Experimental and numerical study on damage behavior of air-backed steel-concrete-steel composite panels subjected to underwater contact explosion

The damage behavior and explosion resistance of air-backed steel-concrete-steel (SCS) composite panels subjected to underwater contact explosions were investigated experimentally and numerically. Firstly, the underwater explosion experiments of the SCS panels were conducted using the novel test setup, and the final damage morphology and residual deflection of these panels were obtained. Secondly, the corresponding finite element model was established in LS-DYNA and validated against the test results, based on the refined numerical modelling, the damage process of the SCS composite panel under 200 g underwater contact explosion was reproduced. After that, the damage mechanism of the SCS panels was revealed through the analysis of internal energy absorption and stress wave propagation inside the SCS panels. Subsequently, the damage behavior of the SCS panels when subjected to underwater and air contact explosions was compared. Finally, a series of parametric analysis were performed to explore the effects of the material strength and structural form on the explosion resistance of SCS panels. Both the experimental and numerical results indicate that the SCS panels suffered global damage. The core concrete absorbed more than 80 % of the explosion energy and the restraint of the steel plates effectively reduced the spalling damage of the core concrete. The SCS composite panel makes full use of the advantages of concrete and steel panels, resulting in superior underwater explosion resistance.

Influence Analysis of Material Parameter Uncertainties on the Stability Safety Factor of Concrete Gravity Dams: A Probabilistic Method

Anti-sliding stability safety is a critical issue that must be given sufficient and widespread attention during the entire lifecycle of gravity dams. The calculated anti-sliding stability safety factor (ASS-SF) is usually compared with the allowable value required by the standards in the traditional method, which ignores the influence of material parameter uncertainties and leads to unreasonable safety evaluation results. Therefore, the nonlinear functional relationship between the stability safety factor (SF) and the random variable parameters is constructed based on the response surface equations, and the distribution types of SF sequences calculated by the Monte Carlo sampling are determined, then a probabilistic stability evaluation method for concrete gravity dams is proposed. Engineering application shows that the calculated SF obeys the normal distribution; the minimum guaranteed rate of different sliding paths in a gravity dam is 86.66%, and the guaranteed rate for the overload safety factor (OSF) is 36.00%. The results imply that a guaranteed rate for the allowable value of the ASS-SF should be provided when making the stability safety evaluation of the dams, especially the OSF. The outcome of this research will advance the understanding of stability evaluation of concrete dams, and reduce the potential risk of sliding instability of concrete dams.