Su Huaizhi

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.

Study on coupling model of seepage-field and stress-field for rolled control concrete dam

Based on the construction interfaces in rolled control concrete dam(RCCD), the methods were proposed to calculate the influence thickness of construction interfaces and the corresponding physical mechanics parameters. The principle on establishing the coupling model of seepage-field and stress-field for RCCD was presented. A 3-D Finite Element Method(FEM) program was developed. Study shows that such parameters as the thickness of construction interfaces, the elastic ratio and the Poissons ratio obtained by tests and theoretical analysis are more reasonable, the coupling model of seepage-field and stress-field for RCCD may indicate the coupling effect between the two fields scientifically, and the developed 3-D FEM program can reflect the effect of the construction interfaces more adequately. According to the study, many scientific opinions are given both to analyze the influence of the construction interfaces to the dams characteristics and to reveal the interaction between the stress-field and the seepage-field.Based on the construction interfaces in rolled control concrete dam(RCCD),the methods were proposed to calculate the influence thickness of construction interfaces and the corresponding physical mechanics parameters.The principle on establishing the coupling model of seepage-field and stress-field for RCCd was presented.A 3-D Finite Element Method(FEM)program was developed.Study shows that such parameters as the thickness of construction interfaces ,the elastic ration and the Poissons ratio obtained by tests and theoretical analysis are more resasonable ,the coupling model of seepage-field and stress-field for RCCD may indicate the coupling effect between the two fields scientifically,and the develpped 3-D FEM program can feflect the effect of the construction interfaces more adequately.According to the stydy,many scientific opinions are given both to analyze the influence of the construction interfaces to the dams characteristic,and to reveal the interaction between the stress-field and the seepage-field.

Assessment model of dam operation risk based on monitoring data

Although the dams produce remarkable social and economic benefits, the threat made by unsafe dams to the life and property of people who live in the lower river area is un-negligible. Based on the monitoring data which reflect the safety condition of dams, the risk degree concept is proposed and the analysis system and model for evaluating risk degree (rate) are established in this paper by combining the reliability theory and field monitoring data. The analysis method for risk degree is presented based on Bayesian approach. A five-grade risk degree system for dam operation risk and corresponding risk degree is put forward according to the safety condition of dams. The operation risks of four cascade dams on some river are analyzed by the model and approach presented here and the result is adopted by the owner.

A new method of estimating the equivalent elastic modulus of RCCD

Based on the composite material mechanic theory, the analysis method for the equivalent elastic moduli which are parallel and vertical to the construction interface of RCCD is studied in this paper. The differences between the equivalent elastic moduli which are vertical to the construction interface of RCCD gotten from different methods are discussed in detail. The variation range of the equivalent elastic modulus which is vertical to the construction interface of RCCD is studied based on the principle of minimum complementary energy and the principle of minimum potential energy. The effect of the related influential factors on the equivalent elastic modulus is analyzed. The estimation formula of the equivalent modulus which is vertical to the construction interface of RCCD is proposed. The feasibility of the approach proposed in this paper is analyzed through an example.

Crack status analysis for concrete dams based on measured entropy

The integrity and safety of concrete dams are seriously affected by the existing cracks in dam bodies, and some serious cracks may cause dam failure or disaster. The propagation of cracks in concrete dams is accompanied by changes in energy distribution, which can be represented by changes in the structure’s system entropy. Therefore, the entropy theory can be used in analyzing the behavior of dam cracks. Due to the randomness and locality of crack propagation, it is difficult to predict the location of cracks by traditional monitoring methods. To solve this problem, the influence of spatial positions of monitoring points on inspection zones is represented by a weight index, and the weight index is determined by the distance measure method proposed in this paper. Through the weighted linear fusion method, the entropy of multiple monitoring points is obtained for analyzing the behavior of dam cracks in the selected zones. Meanwhile, the catastrophe theory is used as the variation criterion of an entropy sequence in order to predict the instability time of dam cracks. Case studies are put forward on a high arch dam, and the fusion entropy is calculated according to the monitoring data from strain gauges. Results show that the proposed method can effectively predict the occurrence time and location of dam cracks regardless of the layout of monitoring instruments, and it is a new way to analyze the occurrence and propagation of dam cracks.