Analysis Of Seismic Ground Motion Of Layered Unsaturated Soil Site

Most of the soil encountered in the construction is unsaturated soil.With the deepening of the seismic response of the site,the seismic ground motion of the unsaturated soil site has become the focus of research.At present,the study on the complex site ground motion of unsaturated soil is mainly about the quasi-saturated soil,which is far from the real saturation situation of unsaturated soil in the natural condition.In order to solve this problem,this paper deduces the analytic solution of the layered unsaturated site seismic ground motion with the theory of mixtures.And this paper analyses the influence of groundwater level rise on ground motion.The main work of this paper includes:(1)Based on the existing theories of wave motion of unsaturated porous media,this paper derived the stiffness transfer matrix of unsaturated soil layer,and established a bedrock-saturated soil-layered unsaturated soil complex site model.The analytical solution of complex layered unsaturated soil site seismic ground motion would be gained in the case of P wave and SV wave incidence by using the transfer matrix method.the analytic solution of saturated soil layer ground wave problem non plane wave,and it will be verified with the existing solution.(2)We have established a reasonable layered unsaturated soil site model with considering the change of groundwater level.By using analytical solutions and the cite model,we analyzed the influence of groundwater level changes on earthquake ground motion calculation,from the angles of incident angle,incident wave frequency,soil rigidity and the saturation of unsaturated soil.Analysis results show:With the rise of groundwater level,the peak value of the surface displacement amplification coefficient decreases,and the frequency response period becomes longer.When the soil water saturation gradient above the ground water level,the peak value of the displacement magnification coefficient decreases when the saturation is constant.