Elasto-plastic Fluid-solid Coupling Analysis Of Seismic Response Of High Core-wall Rockfill Dam

Elasto-plastic analysis of the seismic response of high core-wall rockfill dams considering fluid-solid coupling is one of the most challenging and hot topics in the field of seismic assessment of soil structures. Constitutive models of soils, numerical simulation and engineering application about high core-wall rockfill dams were studied in this dissertation. Based on an elasto-plastic model proposed for granular soils and numerical algorithma, a set of efficient and practical analysis methods and a finite element code for seismic analysis of high core-wall rockfill dams was developed. The main novel achievements obtained in the dissertation are as follows:1. An elasto-plastic model which can describes the static and dynamic behavior of granular soils was developed based on the Pastor-Zienkiewicz III model. Critical state theory and state parameter were introduced into the model to modify the dilatation equation, plastic moduli and so on, thus granular soils with different densities could be described with only one set of model parameters. The proposed model was then validated by simulating the results of static and dynamic triaxial tests of Toyoura sands and Nuozhadu dam rockfill materials, which were conducted under drained or undrained conditions. Comparison with the experimental data shows that the developed model can make a good description of the static and dynamic behavior of granular soils.2. The developed model was incorporated into a finite element code used to analyze the elasto-plastic seismic response of earth-rockfill dams, which could now be applied in practical engineering problems. The centrifuge shaking table program VELACS was used to verify the improved FE code. Comparison between the experimental and simulating results shows that the FE code with the proposed constitutive model can be used well to simulate seismic response problems considering fluid-solid coupling.3. Efficient solvers of linear systems of equations were developed in the FE code, which could now solve large-scale three-dimensional nonlinear analysis of high earth-rockfill dam. The incorporation of three-dimensional transitional isoparametric elements improves the computational accuracy, which enhances obviously the calculation stability. Efficient solvers of linear systems, such as Krylov subspace preconditioned iterative methods and sparse direct methods, were combined with FE analyses of earth-rockfill dams.4. The FE code was applied to analyze two typical core-wall rockfill dams to verify the feasibility and effectivity of the code and the soil model. Memory requirement and computation time are significantly reduced, which indicates that the code can be used in large-scale practical problems as many as 300 thousands DOFs. Comparison with results of viscoelastic model and equivalent linearity method shows that the developed code and model can describe well the seismic response of high core-wall rockfill dams.