Elastic-Plastic Dynamic Analysis(EPDA)of Interaction Of Unsaturated Elastic Semi-space Soil Foundation And Structure

Along with the development of the human society and the centralizing of population, the damage caused by earthquake disaster to our society goes up greatly. So, the importance of performance based on seismic design has been more widely recognized. With the interaction of soil and structure, the characteristics and the influence of the soil is one part of the core. However, there are two errors in seismic design. One is to consider the soil foundation as saturated, which is not prudent. Most of the buildings are actually built on unsaturated soils, and the characteristics of soils will change intensely with the factors such as saturation degree. And the assumption of saturated soil foundation would ignore those factors. The other is to assume the soil as rigid medium, which is not scientific. To infinitely distant field it may be considered as rigid since the deformation of soil on the structure is very small. But to the nearby field, especially at the contact border between the soil and the structure, the elastic plastic property of the soil plays a prominent role on the seismic safety of the structure.This paper focuses on two problems such as the dynamic characteristics of unsaturated soil and the linear elastic aspect of unsaturated soil foundation. The main work and innovation are as following:1).Existed dynamic models for unsaturated porous media are analyzed and compared with each other. The improved wave equation presented by Prof. WeiDcMin is chosen to conduct numerical analysis, and the solution shows that there exist three kinds of compressive waves and one kind of shear wave in unsaturated soils, which agrees with the actual measurement. Also, study is performed on the propagation characteristic of the body waves in unsaturated soils under the influence of such factors as saturated degree and frequency.2).Based on widely reading of relevant literature, research methods about the soil and structure interaction(SSI) are summarized, and their respective advantages and disadvantages are assessed. Then a suitable method is selected for the paper research.3).A practical engineering model is established, and a proper constitutive model for unsaturated soil is chosen as boundary condition. Analysis on the system by dynamic time-history method is performed by Midas/Gen, and the calculation results show that it is necessary to consider the interaction. The integrity safety of the structure in earthquake is evaluated.