Back-analysis For Model Parameters And Stress Displacement Analysis Of High CFRD

Concrete faced rockfill dams (CFRD) have good adaptability with landform, physiognomy and climate, so they have gained broad application and in-depth research on design and construction. Recently, high CFRDs especially win the designer's favor. But due to the limit of test conditions in laboratory and the effect of contractible dimension, it's difficult to describe the accurate mechanical characteristic of rockfill materials. Then the theory of displacement back-analysis has great sense to get the parameters of rockfill constitutive model and rheology model.Firstly the method of displacement back-analysis based on neural network and evolutionary algorithm is introduced and summarized. The neural network is used to substitute the time-consuming finite element analysis and the evolutionary algorithm that is proved efficient and convergent in global range is employed to optimize the neural network and back-analysis the rockfill parameters.This thesis processes systemic analysis and summary according to the in-situ observation data of Tianshengqiao-I CFRD. The study makes detailed research on the difference between observation and calculation results. Then the three factors (reliability of laboratory parameters, wetting deformation, rheology deformation) are discussed and it demonstrates the importance of displacement back-analysis.This thesis mainly discusses and investigates the method of displacement back-analysis. The method of displacement back-analysis based on neural network and evolutionaty algorithm is used to calculate the parameters of CFRD. Based on the project of Tianshengqiao-I CFRD, the study expounds and demonstrates the existing traditional methods, and proposes a new coupling method which can calculates the deformation caused by load and rheology separately. So it can roundly show the process of displacement development. Based on this method, it is convenient to research the impact caused by rheology to the stress and deformation of dam body or concrete slab.The rockfill constitutive model parameters, such as Duncan and Chang's E-B model and the Shen's Elliptic-Parabolic Yield surface model, are also back-analysed and calculated. Then the study compares the results between the two familiar rockfill constitutive models, and concludes the essential characteristic. Three (or four) parameters rheology model and Shen's model are also applied to estimate the mechanism and expansion laws of rheology deformation.Three-dimensional calculation of the CFRD is carried out with the simulatation of the observed filling step and the material distributions. Using the parameters data obtained by back-analysis, the study researches the impact of rheology deformation caused to the concrete slab, joints and dam body. The generic project problems, such as separation between concrete slab and cushion layer, crack of slab, are also described and explained in detail.