Numerical Simulation Study On Stress And Deformation Of Diaphragm Wall Of Earth-rockfill Dam On Soil Foundation

Concrete diaphragm walls are often used as vertical anti-seepage structures for earth-rockfill dams built on deep soil foundation. During construction and impoundment of the dam, the stress of diaphragm walls has very complex distribution. To date, FEM method is one of the most commonly used methods for stress and deformation analysis of diaphragm walls. Unfortunately, the stress and deformation calculated by FEM method are greater than those observed. Larger tensile stresses are also got from this method compared with the real stresses; those differences are too large to accept. As a result, it is a problem needed earliest action to establish an accurate method to calculate the stress and deformation of earth-rockfill dam. According to these questions, some work has been done in this thesis.Firstly, by using nonlinear elastic model (Bathe Model) and tension Mohr-Coulomb failure criterion of concrete, the stress and deformation of diaphragm wall are analyzed. And the result calculated by nonlinear elastic model is compared to those calculated by linear elastic model.Secondly, the improved GA (genetic algorithm) method is introduced, together with direct back-analysis method, a back-analysis program GA-BACK is established. According to the back analysis of a simple earth-rockfill dam, the correct of the program and the feasibility of the method are guaranteed. By comparing of relative errors of five different objective functions back analysis, the equation with fastest calculation speed and best result of back analysis is selected as the objective function of GA-BACK program.Furthermore, the sensibility analysis method of systematology is used to study the influence to the stress of diaphragm walls. Some parameters such as Duncan-Chang E—u model for soil foundation and high-plastic soil, linear elastic model for residue and Goodman model for interface are analyzed using sensibility analysis method. Sensibility factor of each parameter is calculated. Parameters with large sensibility factors are selected for back analysis.Finally, combining the data of Yele earth-rockfill dam with asphalt concrete core, several parameters are back analyzed based on GA-back analysis and complex back analysis. According to compare the speed and result of GA-back analysis and complex back analysis, and the time-history curve of the deformation of dam and the stress of diaphragm wall, the superiority of GA-back analysis is analyzed. With these parameters that optimized, the stress and deformation of diaphragm wall are calculated and analyzed. Further, the effectivity of GA-back analysis is demonstrated.