Three-dimensional Numerical Analysis Of Strong Seismic Responses Of Dyke On Liquefiable Soils Foundation

According to seismic surveys at home and abroad, liquefaction is one of an important reasons leading to the dyke damage. Research on the seismic behaviors and failure mechanism of liquefiable dyke is of great significance for the prevention of disaster and anti-seismic design of dykes.Based on the method of effective stress analysis method using strain space multiple mechanism model, the seismic responses of dyke on liquefiable soils are discussed in this dissertation. The dissertation firstly illustrated the basic principles and procedures of three-dimensional nonlinear effective stress analysis method. Based conditions of the dynamic geotechnical centrifuge tests, the three types of numerical models used to conduct simulation were constructed. Moreover, the distribution law of the deformation, the horizontal and vertical acceleration, ratio of excess pore water pressure stress and effective stress path during shaking and after shaking were investigated. The failure mechanism of dyke and liquefaction mechanism were discussed. Finally, the three dimension computed results were compared with the results from the two dimension simulation and dynamic geotechnical centrifuge test Some main achievements of this dissertation are reached as follows:(1) The results from three-dimensional numerical simulation do good agreement with those form the dynamic geotechnical centrifuge tests results and two dimension simulation. It shows that the proposed simulation mode is effective and reliable.(2) Settlement would occur along the axis of the dyke, and the settlement of the upper part is greater than that of the lower part. That is also observed for the lateral displacement of the central line, but the left and right dyke toe either uplift or lateral displacement are asymmetric, and the right is bigger than the left.(3) The lower part of the dyke foundation soil compared with the upper soil layer is more susceptible to liquefaction. Shear stress and shear strain caused by the shear power maybe lead to soil liquefaction at the bottom dyke. However, for the free site soil, J₂^1/2(Stress) and J₂^1/2(Strain) caused by the shear power is due to the main reasons.(4) The greater the earthquake intensity the more serious destruction of the dyke is. It is also found that liquefaction and lateral spread of dyke during strong motions would cause a larger deformation and collapse. Seismic design should be given more attention and make the corresponding measures.These results will provide for a certain theoretical and practical significance, basis for engineering and technical support for seismic design and liquefaction evaluation of dyke found on liquefiable soils.