Hydraulic Concrete Structure Research Articles

Comparison between the Influence of Finely Ground Phosphorous Slag and Fly Ash on Frost Resistance, Pore Structures and Fractal Features of Hydraulic Concrete

Hydraulic concrete in cold regions is necessary for good frost resistance. The utilization of finely ground PS (FGPS) in the construction of hydropower projects could solve the pollution issue and the fly ash shortage problem. In this work, the influence of FGPS and fly ash on frost resistance, pore structure and fractal features of hydraulic concretes was investigated and compared. The main results are: (1) The inclusion of 15–45% FGPS reduced the compressive strength of plain cement concretes by about 21–52%, 7–23% and 0.4–8.2% at 3, 28 and 180 days, respectively. (2) The inclusion of FGPS less than 30% contributed to the enhancement of 180-day frost resistance. At the same dosage level, the FGPS concrete presented larger compressive strengths and better frost resistance than fly ash concrete at 28 and 180 days. (3) At 3 days, both the addition of FGPS and fly ash coarsened the pore structures. FGPS has a much stronger pore refinement effect than fly ash at 28 and 180 days. The correlation between frost resistance of hydraulic concrete and pore structure is weak. (4) At 28 days, the incorporation of FGPS and fly ash weakened the air void structure of hydraulic concrete. At 180 days, the presence of FGPS and fly ash was beneficial for refining the air void structure. The optimal dosage for FGPS and fly ash in terms of 180-day air void refinement was 30% and 15%, respectively. The frost resistance of hydraulic concretes is closely correlated with the air void structure. (5) The pore surface fractal dimension (Ds) could characterize and evaluate the pore structure of hydraulic concretes, but it was poorly correlated with the frost resistance.

Concrete life prediction model based on freeze-thaw damage theory and its application

For hydraulic concrete structure in cold and severe cold areas in northern China, its frost resistance directly restricts the life and safe and stable operation of the project. In this paper. Based on the freeze-thaw damage theory, this paper optimizes and improves the Weibull distribution model, and uses the 1:1:4 standard frost-resistant specimen of hydraulic concrete as the physical model to obtain a freeze-thaw damage model that is more in line with the standard specimens of the rapid freeze-thaw experiment. Based on this model, a concrete life prediction method is proposed. In order to solve the problem that the initial damage of coring concrete is not clear, an iterative approximation method is proposed. The life prediction method proposed was verified through actual engineering cases. The results show that the model can better describe the process of concrete freeze-thaw damage and destruction, and the life prediction results are more reliable.

Study on Structure Design of Generator of Flood Discharge Tunnel with Level Swirling Flow

Through the design of the Generator of the spillway tunnel, the safe operation efficiency of flood discharge tunnel with the level swirling flow is further improved. This paper takes the horizontal swirl spillway tunnel of Gongboxia Hydropower Station on the Yellow River as an example. First, the project hub facilities of the Gongboxia Hydropower Station are introduced. Moreover, the design of the gradient section and the spinning chamber section in the Generator is also studied. Based on the calculation scheme of structural mechanics, the internal force of the structure under various load combinations such as external water pressure and internal water pressure is calculated. According to Design Codes For Hydraulic Concrete Structure, the structural reinforcement is computed. These provide the basis for the design of the flood discharge tunnel with level swirling flow of large hydropower engineering facilities in Northwest China.

Research on Corrosion Detection and Assessment Method for Hydraulic Concrete Structures

In our country, hydraulic concrete structure construction technology is widely used. However, with the increase of time and the erosion of the environment, there will be aging and safety risks in this structure. This puts forward higher requirements for detection technology and safety assessment technology of hydraulic concrete structures. Therefore, in order to promote the innovation and progress of this engineering technology, we should carry out targeted strategy analysis based on the development and application status of related technologies and engineering practice. We should also actively introduce advanced detection technology and equipment to maintain the development of China’s hydraulic concrete structure construction technology. This is conducive to the vigorous and healthy development of China’s water conservancy projects.

Shear test of the rectangular beam on the new to old concrete interface based on Digital Image Correlation

The bond property of new to old concrete is the key to strengthen and reinforce the hydraulic concrete structure, and shear strength is an important index of its bond property. With the help of advanced Digital Image Correlation (DIC), the direct shear state, fracture surface displacement, deformation and crack location of the new to old concrete bonding interface are studied through the shear test of rectangular beam, the strain distribution pattern of the bonding interface is well obtained. The results show that the interfacial roughness of specimen has great influence on the shear strength of the repaired specimen. The greater the roughness is, the better the bond property is. Due to friction, the specimen itself will be subject to the combined action of bending and shearing, which leads to bending shear failure of specimen rather than pure shear failure.

Concrete piezoceramic smart module pairs-based damage diagnosis of hydraulic structure

As a main reaction on the ageing behavior of hydraulic concrete structure, the structural damage is harm to structural safety. With the dynamic damage experiment of concrete gravity dam model under ambient excitation, a concrete piezoceramic smart module (CPSM) pairs-based approach is studied to implement the dynamic characteristics identification and damage diagnosis of hydraulic structure. Based on the piezoelectric coupling property and elastic-plastic contact property of CPSM, which are analyzed by use of numerical simulation software, the optimal shape of CPSM is given. A self-made CPSM-based monitoring platform is developed to obtain the information on structural damage. A wavelet packet decomposition method of CPSM signal is introduced. By analyzing the relation between CPSM signal amplitude and wavelet packet node energy, an index, which is defined with wavelet packet node energy, is proposed to describe the structural damage. The dynamic experimental result shows that above defined index changes obviously with the structural developing damage, and can well reflect the structural damage status. The feasibility and effectiveness of self-made CPSM-based approach are verified to identify the dynamic characteristics and diagnose the hidden damage for hydraulic structure.

New insights into the spatial variability of biofilm communities and potentially negative bacterial groups in hydraulic concrete structures

The composition and distribution characteristics of bacterial communities in biofilms attached to hydraulic concrete structure (HCS) surfaces were investigated for the first time in four reservoirs in the middle and lower reaches of the Yangtze River Basin using 16S rRNA Miseq sequencing. High microbial diversity was found in HCS biofilms, and notable differences were observed in different types of HCS. Proteobacteria, Cyanobacteria and Chloroflexi were the predominant phyla, with respective relative abundances of 35.3%, 25.4% and 13.0%. The three most abundant genera were Leptolyngbya, Anaerolineaceae and Polynucleobacter. The phyla Beta-proteobacteria and Firmicutes and genus Lyngbya were predominant in CGP, whereas the phyla Cyanobacteria and Chloroflexi and genera Leptolyngbya, Anaerolinea and Polynucleobacter survived better in land walls and bank slopes. Dissolved oxygen, ammonia nitrogen and temperature were characterized as the main factors driving the bacterial community composition. The most abundant groups of metabolic functions were also identified as ammonia oxidizers, sulphate reducers, and dehalogenators. Additionally, functional groups related to biocorrosion were found to account for the largest proportion (14.0% of total sequences) in gate piers, followed by those in land walls (11.5%) and bank slopes (10.2%). Concrete gate piers were at the greatest risk of biocorrosion with the most abundant negative bacterial groups, especially for sulphate reducers. Thus, it should be paid high attention to the biocorrosion prevention of concrete gate piers. Overall, this study contributed to the optimization of microbial control and the improvement of the safety management for water conservation structures.

Study on the Aging and Pore Structure of Hydraulic Concrete

The aging of hydraulic concrete structure is a highly complicated problem. To reasonably evaluate the aging situation of a long-term operating concrete sluice, the core samples are obtained by field sampling from the sluice piers and the mercury injection experiment is carried out in this paper. The main objectives of this experimental investigation are to analyze the pore structure characteristics of the different parts in core samples and discuss the concrete aging rule of hydraulic concrete structure. The experimental results show that the aging of the hydraulic concrete has a certain relationship with the evolution of the concrete pore structure. It is feasible to use the pore structure of concrete to express the concrete aging of the hydraulic structure. The research in this paper will provide a basis for further study on the aging mechanism of the hydraulic concrete structure.

Influence of polyacrylic ester and silica fume on the mechanical properties of mortar for repair application

Experimental investigations on the influence of different amounts of polyacrylic ester and silica fumes on the mechanical properties of mortar such as the compressive strength, splitting tensile strength, bonding strength, and abrasion resistance are presented in this article. The results show that the compressive and splitting tensile strength of mortar can be improved with the addition of polyacrylic ester and silica fumes. Results obtained from both the direct tensile bond test and flexural bond test indicate that the addition of polyacrylic ester and silica fumes improves the bond strength significantly, and the enhancement is more obvious with polyacrylic ester paste as interfacial adhesives. Furthermore, mortar incorporation of polyacrylic ester and silica fumes shows superior abrasion resistance compared to the control mortar. Therefore, the correct combination of polyacrylic ester and silica fumes to produce mortars has been shown to have synergistic effects, which results in excellent properties including high bond strength and superior abrasion resistance. Mortars containing polyacrylic ester and silica fumes are ideal for repairing concrete especially for hydraulic concrete structure.

Crack detection in hydraulic concrete structures using bending loss data of optical fiber

Due to low tensile strength of concrete, seasonal temperature, shrinkage of concrete, and so on, many of hydraulic concrete structures experience cracking. An optical fiber–based approach is introduced to implement the crack detection in hydraulic concrete structures. The experimental and theoretical investigations on bending loss and time-domain reflection behaviors of optical fiber are performed. According to the bending loss mechanism of optical fiber, the monitoring method of hydraulic concrete crack is presented. First, the effect of optical fiber bending radius on optical loss is analyzed. The mathematical model between bending radius and optical loss is established. Then, the identification principle of concrete crack using bending loss data of optical fiber is studied. Considering the crack characteristics of hydraulic concrete structure, the arrangement forms of optical fiber, which are used to monitor the tension crack and hybrid crack in hydraulic concrete structure, are proposed. Finally, the relationship between crack development and optical loss is investigated using laboratory experiments with optical fiber.

Experimental study on obtaining hydraulic concrete strength by use of concrete piezoelectric ceramic smart module pairs

The concrete strength has the strong influence on service safety of mass hydraulic concrete structures. The real-time identification of concrete strength is very important to ensure the pouring quality during the construction and find timely the hidden troubles in service. Based on the analysis for the mapping relationship between concrete strength and stress wave amplitude, the method is proposed to obtain indirectly the concrete strength with self-made concrete piezoelectric ceramic smart module pairs. First, according to the service condition of hydraulic concrete structure, the concrete piezoelectric ceramic smart module is designed and the process manufacturing concrete piezoelectric ceramic smart module is presented. The protecting measures of piezoelectric ceramic piece, the peripheral material constituent, and the pouring links are introduced. Second, an integrated system, which is composed of self-made concrete piezoelectric ceramic smart modules in pair as sensor and actuator, fuzzy inference system, and other auxiliary equipments, is developed to monitor indirectly concrete strength. Its working principle is studied. Finally, an experiment of hydraulic concrete strength is implemented to demonstrate the feasibility and validity of the proposed method and developed system. The concrete piezoelectric ceramic smart modules in pair are taken as sensor and actuator embedded in hydraulic concrete specimens. The wave-based analysis method is adopted to collect the stress wave amplitude data during the pouring process of concrete specimens. The fuzzy inference approach is utilized to build the mathematical model describing the relationship between concrete strength and stress wave amplitude. Based on the above mathematical model, the concrete strength can be identified indirectly.

Disease Analysis on Hydraulic Concrete Structure of Reservoir Works in Jiangxi Province

In recent years, a large proportion of reservoir works in Jiangxi province have emerged different kinds of new diseases, which not only hold back the benefit but also affect the safety of these projects, to some extent. Based on investigating the present situation of dams in Jiangxi province and analyzing the reasons for deterioration condition in reservoir works, the main disease for hydraulic concrete structure of ill-dangerous dams is divided into several typical types and the characteristics of the existing problems are given as well as some control measures.

Application Progress of Nondestructive Testing Technique of Hydraulic Concrete Based on Steady Rayleigh Wave Method

In the large hydraulic concrete structure that conventional nondestructive testing technique can’t implement quantitative detection, using steady Rayleigh wave technique can acquire various characteristic parameters of concrete. The paper introduces the principle and detection system of steady Rayleigh wave technique systematically, and makes detection experiments to introduce steady Rayleigh wave e technique and application progress of it in quality of large hydraulic concrete and nondestructive detection of crack depth. The practice proves that steady Rayleigh wave detection technique has the characteristics of strong antijamming capability and higher detection precision.

Monitoring Methods of Crack Behavior in Hydraulic Concrete Structure Based on Crack Mouth Opening Displacement (CMOD)

For the difficulty of applying classical fracture criteria to the actual hydraulic engineering and silulating the process of cracking by conditional FEM, in this paper, a new method of analyzing and monitoring crack behavior in hydraulic structures under the effect of Hydro-Mechanical (HM) interaction is studied by using the XFEM, in which crack mouth opening displacement (CMOD) is adopted as monitoring index. The core innovation done in this study is that a method of determining macro crack tip is proposed based on cohesive force for the first time, and the critical value of CTOD is investigated and proved to be a material parameter. it is verified by comparing with the concrete tests and numerical calculations of former related literatures. All of the above shows that the present monitoring method based on CMOD provides a practical way to simulate cracking in hydraulic concrete structures.

The Cracking Mechanism and Anti-Cracking Measures for Hydraulic Mass Concrete

The article describes and analyzes the process of mass concrete casting and crack problems during the period of construction. The article illustrates the necessity of crack control for mass concrete structures and introduces the present application situation of commercial software used to analyse the temperature field and stress field. Combining the engineering practice, the article sums up the measures to deal with hydraulic mass concrete structure cracks and the application situation of various methods. Then the article puts forward the future research direction to solve the problem of hydraulic mass concrete crack.

Surface Thermal Insulation and Pipe Cooling of Spillways during Concrete Construction Period

Given that spillways adopt a hydraulic thin concrete plate structure, this structure is difficult to protect from cracks. The mechanism of the cracks in spillways shows that temperature stress is the major reason for cracks. Therefore, an effective way of preventing cracks is a timely and reasonable temperature-control program. Studies show that one effective prevention method is surface thermal insulation combined with internal pipe cooling. The major factors influencing temperature control effects are the time of performing thermal insulation and the ways of internal pipe cooling. To solve this problem, a spillway is taken as an example and a three-dimensional finite element program and pipe cooling calculation method are adopted to conduct simulation calculation and analysis on the temperature fields and stress fields of concretes subject to different temperature-control programs. The temperature-control effects are then compared. Optimization results show that timely and reasonable surface thermal insulation and water-flowing mode can ensure good temperature-control and anticrack effects. The method has reference value for similar projects.

Two-Dimensional Shear Stress on Bonding Interface of FRP Plate Reinforced Hydraulic Concrete

The bonded interface between FRP plate and the hydraulic concrete is a key part while reinforcing the hydraulic concrete structure with FRP plate. The bond property of the interface directly decides the results of structural reinforcement. In most of the external loading conditions, this interface is under the shear stress state. Therefore, accurate measurement and analysis of interfacial shear stress distribution is the guarantee of FRP reinforced hydraulic concrete structure the premise of success. Focusing on the shear-resisting bonding strength of FRP-concrete interface, this paper improved the ASTM D905 standard shear sample and carried out numerical simulation of shear test to the bonded interface of FRP-reinforced hydraulic concrete structure by adopting the bi-dimensional finite element method, and conducted parameter analysis of the influence factors (elasticity modulus of FRP and concrete, shear modulus and thickness, etc) of shear stress on the FRP-concrete bonded interface and finally the distribution characteristics of shear stress on the bonded interface were obtained. This paper mainly discussed the influence rules of stress concentration to the distribution of shear stress on the bonded interface, which provides theoretical guidance and direction to the shear-resisting bonding strength test in the next step as well as technical support to the processing of FRP-strengthened hydraulic concrete bonded interface.

Tomographic diagnosis of defects in hydraulic concrete structure

The ultrasonic tomographic technology is applied to diagnose the defects in hydraulic concrete structure. In order to improve the precision of diagnoses, the wavelet transformation is used in the processing of ultrasonic signals. The influences of water, scale and orientation of defect, processing methods and theoretical model on image resolution are investigated. The experimental results indicate that the result of the tomographic diagnosis of a single defect is sensitive and the boundary can be clearly determined. However, the image resolution of multiple defects is not satisfactory. The water content and scale of a defect may significantly affect the imaging resolution. Defects with the orientation perpendicular to the direction of the diagnosis may have higher precision in diagnosing. The wavelet transformation technology can elevate the imaging resolution. The applied calculation model plays a very important role in improving the accuracy of detection.

Review on hidden trouble detection and health diagnosis of hydraulic concrete structures

A large number of hydraulic concrete structures have hidden defects such as cracks, erosion, freeze and thaw, thermal fatigue, carbonization. These hidden defects seriously affect the strength, stability and durability of structures. These problems are studied mainly by single monitoring or diagnosis methods at present. The integration of multiple monitoring and diagnosis methods is not applied widely. Besides, the analysis theory on these problems is not developed very well. The systemic study on the aging mechanism of hydraulic concrete structures, time-variation model and health diagnosis is still not enough. The support for engineering practice is limited. Aimed at these major scientific and technological problems and combined with specific projects, study on detection of hidden defects and health diagnosis of hydraulic concrete structure has been carried out. This study includes the following content: field non-destructive examination of hidden defects of hydraulic concrete structures, seepage detection, the construction of in-situ sensing system, the combination of field detection and in-situ monitoring, the mechanism of crack, freeze and thaw, erosion and carbonization of hydraulic concrete structure, mechanism of combination aging; time-variation model of hydraulic concrete structure, theories and methods for health diagnosis of hydraulic concrete structures.

Biological studies on a concrete dam

La Cruz dam is a hydraulic concrete structure placed in a hilly rural area near to the city of Azul (Buenos Aires Province, Argentina). Lichen colonization was detected in the dam so the aim of this paper is to study the characteristics of the cementitious substrate, to identify the lichen species and to assess their potential negative action. Cementitious mortar samples were brought to the laboratory in order to study their water absorption rate, density, pH and alkali concentration. Lichens have been sampled by scraping them out of the substrate. The dam wall is colonized mainly byCaloplaca citrina, which is different from the situation observed in nearby rocks and the Tandil dam, where other species were also found. The lichen and the superficial layer were analyzed with infrared spectrometry and oxalic acid was detected indicating a chemical degradation of the surface. Except for this negative action due to the lichen, the cementitious mortar samples have good pH, density and porosity characteristics, and no external evidence of sulphation or alkalisilica reaction were observed. In conclusion, the lichen acts superficially and causes only an aesthetical problem with no structural risk to the dam, but only an aesthetical problem, therefore no actions are recommended.