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Detection of subcritical crack propagation for concrete dams

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Science china(Technological Sciences) 2009年第12期52卷 3654-3660页

作者： BAO TengFei1 ,2&YU Hong 1,2 1College of water Conservancy&Hydropower engineering,hohai university,nanjing 210098,china 2national engineering research center of water resources efficient utilization and engineering safety,nanjing 210098,china College of water Conservancy & Hydropower engineering Hohai University Nanjing China national engineering research center of water resources efficient utilization and engineering safety Nanjing China

Subcritical propagation of cracks is a warning sign of *** such propagation is detected at an early stage,timely maintenance measures can be taken to prevent the failure of *** detect the subcritical propagation of a crack,the crack needs to be monitored continuously in a long term, which is not realistic under certain ***,cracks in concrete dams can be monitored continuously by dam monitoring to offer possible detection for subcritical *** this paper, with measured crack openings from dam monitoring,a state equation for characterizing crack development is established based on the grey system *** relation between the stability of the equation and the subcritical crack propagation is investigated,then a criterion is proposed for detecting subcritical *** example demonstrates the validity of the criterion and its potential for practical application.

关键词： crack subcritical propagation criterion concrete

research on stability of the accumulated rock-soil body of reservoir bank under rainfall condition

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Science china(Technological Sciences) 2009年第9期52卷 2528-2535页

作者： GU ChongShi1,2,WU HaiZhen1,2 & SU HuaiZhi1,2 1 College of water resources and Hydropower engineering,hohai university,nanjing 210098,china 2 national engineering research center of water resources efficient utilization and engineering safety,hohai university,nanjing 210098,china 3 Jiangxi water Conservancy research Institute,Nanchang 330029,china College of water resources and Hydropower engineering Hohai University Nanjing China national engineering research center of water resources efficient utilization and engineering safety Hohai University Nanjing China Jiangxi water Conservancy research Institute Nanchang China

The shear strength parameters property of rock-soil aggregates in embankment slope of reservoir,that is,the relationship between cohesion and gravel content,between friction angle and gravel content,and the relationship between cohesion and water content,between friction angle and water content,is studied based on the direct shear test results,the shear strength change law of the rock-soil aggregates is given,and the unsaturated shear strength formulation of rock-soil aggregates that could consider suction and saturation degree influence is put forward in this paper,through which the sliding or failure physical mechanism of this type of slope under the condition of rainfall infiltration is studied. Also the 3D unsteady saturated-unsaturated seepage field and its FEM resolving mode are established based on the analysis of the slope rainfall infiltration process. Case study with this method indicates that the minimum safety factor of the accumulated rock-soil aggregates dose not arrive at the moment of rainfall cessation,but appears several hours after the rainfall cessation,this phenomenon is in accordance with the practical slope engineering's failure process and could explain appropriately the slope failure caused by rainfall infiltration. research results in this paper have an important reference value for the research on stability of the accumulated rock-soil aggregates in embankment slope of reservoir,and can enrich the stability analysis method and relevant theory of reservoir embankment slope.

关键词： reservoir bank slope rock-soil aggregates rainfall infiltration saturated/unsaturated seepage

Assessment model of dam operation risk based on monitoring data

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Science china(Technological Sciences) 2007年第Z1期50卷 144-152页

作者： WU ZhongRu1,2?, SU HuaiZhi1,2 & GUO HaiQing1 1 College of water Conservancy and Hydropower engineering, hohai university, nanjing 210098, china 2 national engineering research center of water resources efficient utilization and engineering safety, nanjing 210098, china College of water Conservancy and Hydropower engineering Hohai University Nanjing China national engineering research center of water resources efficient utilization and engineering safety Nanjing China

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.

关键词： dam monitoring data operation risk degree analysis model

Back analysis of mechanical parameters of roller compacted concrete dam

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Science china(Technological Sciences) 2010年第3期53卷 848-853页

作者： GU ChongShi 1,2,3,LI Bo 1,XU GuangLei 4 &YU Hong 1,2,3 1 State Key Laboratory of Hydrology-water resources and Hydraulic engineering,hohai university,nanjing 210098,china 2College of water Conservancy Hydropower,hohai university,nanjing 210098,china 3national engineering research center of water resources engineering safety,efficient utilization and nanjing 210098,china 4 nanjing Hydraulic research Institute,nanjing 210029,china State Key Laboratory of Hydrology-water resources and Hydraulic engineering Hohai University Nanjing China College of water Conservancy Hydropower Hohai University Nanjing China national engineering research center of water resources engineering safety Efficient Utilization and Nanjing Nanjing China nanjing Hydraulic research Institute Nanjing China

In view of the diversity and complexity of mechanical parameters of roller compacted concrete dam(RCCD),the uniform design method,partial least-squares regression(PLS)and least squares support vector machine(LSSVM)were applied to the back analysis of RCCD with the use of the complex nonlinear relationship between dam mechanical parameters and dam *** the process of back analysis,the initial samples of parameters were designed with uniform design ***,a transversely isotropic model of RCCD was established by *** *** this model,training samples of LSSVM model could be *** then,the complex nonlinear relationship between relative values of hydraulic components of dam displacements and mechanical parameters was ***,actual relative values of dam hydraulic components are isolated from the measured data of dam displacements by using *** inputting the isolated relative values into LSSVM model,the back analysis values of RCCD mechanical parameters can be *** example analysis showed that mechanical parameters obtained by the above-mentioned back analysis method are reasonable,and the back analysis method is feasible.

关键词： roller compacted concrete dam mechanical parameters back analysis

Multivariate analysis in dam monitoring data with PCA

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Science china(Technological Sciences) 2010年第4期53卷 1088-1097页

作者： YU Hong1,2,WU ZhongRu1,2,BAO TengFei1,2 & ZHANG Lan1,2 1 State Key Laboratory of Hydrology-water resources and Hydraulic engineering,hohai university,nanjing 210098,china 2 national engineering research center of water resources efficient utilization and engineering safety,hohai university,nanjing 210098,china State Key Laboratory of Hydrology-water resources and Hydraulic engineering Hohai University Nanjing China national engineering research center of water resources efficient utilization and engineering safety Hohai University Nanjing China

Given the limitation of traditional univariate analysis method in processing the multicollinearity of dam monitoring data,this paper reconstructs the multivariate response variables by introducing principal component analysis(PCA) method,explores the ways of determining principal components(PCs),and extracts a few PCs that have major influence on data *** steady observation series,a control field for the whole observation values has been established based upon PCA;for unsteady observation series that have significant tendency,a control field for the future observation values has been constructed according to PC statistical predication *** methods have already been applied to an actual project and the results showed that data interpretation method with PCA can not only realize data reduction,lower data redundancy,and reduce noise and false alarm rate,but also be effective to data analysis,having a broad application prospect.

关键词： dam safety monitoring multivariate response variables principal component analysis data reduction

Analysis of crack propagation in concrete structures with structural information entropy

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Science china(Technological Sciences) 2010年第7期53卷 1943-1948页

作者： BAO TengFei1’2, PENG Yan1’2, CONG PeiJiang1’2 & WANG JiaLin1’2 1 State Key Laboratory of Hydrology-water resources and Hydraulic engineering, hohai university, nanjing 210024, china 2 national engineering research center ofwater resources efficient utilization and engineering safety, hohai university, nanjing 210024, china State Key Laboratory of Hydrology-water resources and Hydraulic engineering Hohai University Nanjing China national engineering research center of water resources efficient utilization and engineering safety Hohai University Nanjing China

The propagation of cracks in concrete structures causes energy dissipation and release, and also causes energy redistribution in the structures. Entropy can characterize the energy redistribution. To investigate the relation between the propagation of cracks and the entropy in concrete structures, cracked concrete structures are treated as dissipative structures. Structural information entropy is defined for concrete structures. A compact tension test is conducted. Meanwhile, numerical simulations are also carried out. Both the test and numerical simulation results show that the structural information entropy in the structures can characterize the propagation of cracks in concrete structures.

关键词： crack entropy concrete sun

A new method of estimating the equivalent elastic modulus of RCCD

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Science china(Technological Sciences) 2007年第Z1期50卷 136-143页

作者： GU ChongShi1,2?, WU Yuan1, SU HuaiZhi1,2 & TANG LiHui1 1 College of water Conservancy and Hydropower engineering, hohai university, nanjing 210098, china 2 national engineering research center of water resources efficient utilization and engineering safety, nanjing 210098, china College of water Conservancy and Hydropower engineering Hohai University Nanjing China national engineering research center of water resources efficient utilization and engineering safety Nanjing China

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.

关键词： RCCD equivalent elastic modulus variation range estimation method

Hybrid method of limit equilibrium and finite element internal force for analysis of arch dam stability against sliding

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Science china(Technological Sciences) 2011年第4期54卷 793-798页

作者： BAO TengFei1,2,3,XU BaoSong1,2,3 & ZHENG XueQing1,2,3 1State Key Laboratory of Hydrology-water resources and Hydraulic engineering,hohai university,nanjing 210098,china 2national engineering research center of water resources efficient utilization and engineering safety,nanjing 210098,china 3College of water Conservancy and Hydropower engineering,hohai university,nanjing 210098,china State Key Laboratory of Hydrology-water resources and Hydraulic engineering Hohai University Nanjing China national engineering research center of water resources efficient utilization and engineering safety Nanjing China College of water Conservancy and Hydropower engineering Hohai University Nanjing China

A hybrid method of limit equilibrium and finite element internal force for analysis of arch dam stability against sliding is *** finite element internal force method(FEIFM) is used to provide more accurate thrust forces acting on the faces of a slip body,and the limit equilibrium method(LEM) is employed to evaluate the factor of safety of the slip *** method presented can deal with a slip body with large amount of geometrically complex slip *** addition,compared with the traditional LEM,it can meet the balance condition of the forces in the slip *** example shows that the factor of safety obtained by the method presented agrees well with the theoretical solution.A practical example is also presented to demonstrate the application of the method in the stability analysis of an arch dam *** results from the examples show that the method is promising in analysis of arch dam stability against sliding.

关键词： arch dam stability against sliding limit equilibrium method finite element internal force method

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

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Science china(Technological Sciences) 2007年第Z1期50卷 34-50页

作者： WU ZhongRu1,2?, LI Ji1, GU ChongShi1,2 & SU HuaiZhi1,2 1 College of water Conservancy and Hydropower engineering, hohai university, nanjing 210098, china 2 national engineering research center of water resources efficient utilization and engineering safety, nanjing 210098, china College of water Conservancy and Hydropower engineering Hohai University Nanjing China national engineering research center of water resources efficient utilization and engineering safety Nanjing China

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.

关键词： hydraulic concrete structure hidden trouble detection health diagnosis