Research On Mechanical Behavior Of Asphalt-concrete And Safety Analysis To Maopingxi Rockfill Dam In TGP

It was found that the modulus K of asphaltic concrete exterminated by triaxial test is under the normal level during the constructing of Maopingxi rockfill dam in TGP. In consequence, the security of dam, especially whether hydraulic fracture will occur in the core wall was worried about. This brings great difficulties for State Department expert group to check and accept the Three-Gorges Project as usual. In this paper, to resolve such a problem, a new stress-strain constitutive model based on the increment plastic theory is given, by studying the mechanical characteristic of asphaltic concrete deeply. This helps to accomplish the dam's safety checking successfully through making use of archetypal monitoring information from construction locale. Furthermore, the possible hidden trouble in dam body is analyzed and the operating principle of high Rock Fill Dam with Asphalt Concrete Core Wall is revealed, which provide scientific principle for the judgment of MAOPINGXI Dam's operating security. Meanwhile, shortcomings of current design criterion and regulation for core wall of asphaltic concrete are also analyzed in here.The main contents of this paper are as follows: firstly, both the design and construction status of dam at present are synthetically introduced under the subject matter of Rock Fill Dam with impervious core wall of asphaltic concrete; secondly, the development status in theory aspect of hydraulic asphaltic concrete are discussed.Focused on the property that hydraulic asphaltic concrete shows in plastic and creep deformation, combined with the experimental results of triaxial tests, a stress stain constitutive model considering elastic-plastic coupling and the modified Singh-Mitchell creep model are respectively put forward. Further, these models are applied in the safety analysis for MAOPINGXI Dam. It is indicated: for one thing, the calculated results are quite agreement with the monitoring data through examination of suggested models by archetypal monitoring information of dam at Water Storage Level 135 m; for another, neither shear failure nor hydraulic fracture will happen in core wall of asphaltic concrete based on the analysis of Viscous-elastic-plasticity for simulated dam construction at Water Storage Level 175m.Since the mechanical properties of asphaltic concrete are very sensitive to the influence of temperature, the loading rate in testing, specimen shaping methods, and so on, the safety analysis and evaluation on dam are performed using the back analysis method in this paper. In respect thatConsidering the clear randomicity of model parameters of asphaltic concrete determined by experimental dates from triaxial tests and the conspicuous dispersion of archetypal monitoring information of dam, back analysis on the mechanical parameters of core wall of bitumen concrete is make, by means of Bayes stochastic inversion theory, so that the work of the MAOPINGXI dam's safety checking can be carried out successfully. The results indicated that the dam is safe. Additionally, sensitivity analysis on the modulus K of asphaltic concrete, which determine the judgment of dam' safety, is studied. The conclusion is that the modulus K is not necessary and sufficient conditions for safety of dam.Finally, the defects and flaws of current design criterion and regulation, and the standard of testing method for core wall of asphaltic concrete are also analyzed in this paper. Some suggestions are given on the basis of the practice of MAOPINGXI dam and the research work of this dissertation.