Analysis On Nonlinear Seismic Response Of Dynamic Interaction Between Saturated Soil And Underground Structure

During dynamic response analysis of the soil-structure problems, the emission impact of wave energy to infinite foundation is important. The saturated soil, which is made up of solid skeleton and pore liquid fluid medium exists generally in the natural earth. Under the dynamic loading, dynamic interacting between soil and structure is concerned, so using the saturated soil theory analyzing is more appropriate and scientific than using the single-phase medium to analyze. Since the complexity of the saturated porous media theory and difficulties in the mathematical processing, the analytic solution of saturated porous medium dynamic response is usually used with the simple boundary condition. However, numerical method is effective when comes to complicated conditions such as the complex geometry, the heterogeneous problem of near field and nonlinear problem. In the dynamic finite element analysis of saturated porous media in the whole space or half-space, the finite element method is usually selected for computing. And to reflect the radiation energy effect of unrestricted region, it is necessary to input the supposed artificial boundary and its computing method. The artificial boundary disposing methods and computing methods will largely influence computing accuracy. In this thesis, the finite element analysis method is adopted to simulate the seismic response of underground structures. During the numerical simulation analysis of earthquake response, the soil around underground structure is seen as a fluid-saturated porous media. Finally, the seismic response regulations of underground structure are concluded, and the main contents are listed as below:(1) The visco-elastic boundary of saturated soil foundation is studied, the model of free field is built, and the numerical results are compared with generalized analytic solution, the boundary conditions include the fixed boundary condition, the viscous boundary condition, and the visco-elastic boundary condition, and finally to verify the accuracy of the visco-elastic boundary condition.(2) The input seismic wave can be transformed into equivalent load loaded on the artificial boundary nodes. The auxiliary calculation procedure is programmed to realize calculating the nodal loads for applying in the finite element software, and the two-dimension free field finite element model is built, and the free field seismic response is analyzed under some different seismic waves, and finally compare the different computing results between using single-pharse media and two-pharse media.(3) The finite element model of two-dimension subway station structure is built by the practical subway station engineering. Under the consideration of saturate soil and assumption of single medium, the subway station structure’s seismic responses under horizontal seismic wave are analyzed. Compared with the shaking table test, the corresponding regulations of internal force distribution are obtained. Finally, discuss the most unfavorable position under the horizontal earthquake action, and put forward some suggestion on aseismatic construction.