The Analysis Of Site Seismic Response Based On The Principle Of Effective Stress

The fluid saturated porous media widely exist in the natural world;they are generally composed by solid skeleton and pore fluid composition.The significant nonlinear property of soil and solid-liquid two-phase property will lead to coupling deformation between soil pore water pressure and soil skeleton under strong ground motion.On the other hand,studies have shown that soil showed obvious different mechanical properties under static or dynamic loads.It is difficult to exactly express the deformation mechanical property of soil during the process of the static and dynamic coupling analysis only using a single soil constitutive material.Therefore,based on the effective stress method,taken soil materials as solid-liquid two-phase medium,elastic constitutive of soil was used in the process of initial stress field balance,while elastoplastic constitutive model under the earthquake action,and a freefield static and dynamic coupling seismic response analysis model was established,the specific content are listed as follows:Firstly,based on the study of nonlinear elastic constitutive model and elastoplastic constitutive model,the basic principles of Duncan-Chang model and Davidenkov model were briefly described.And then user material subroutine of these two constitutive models were compiled and verified theoretically on the platform of ABAQUS software.The results show that the two soil constitutive models can simulate the nonlinear dynamic properties of soil very well which lay the foundation for the joint application of subsequent models.Secondly,based on conventional triaxial tests and dynamic triaxial test,Duncan-Chang and Davidenkov model parameters of several soil materials were tested,and the influence of the physical properties of the soil on the parameters of the constitutive model was compared.The results show that the basic parameters of soil material have certain influence on the parameters of Duncan-Chang model,and there are some variation rules between Duncan-Chang model and Davidenkov model.Finally,based on the effective stress method,taking soil as a solid-liquid two-phase medium,and considering viscoelastic artificial boundary condition and ground wave motion input method,free field static and dynamic coupling seismic response analysis models were established.In the model,Duncan-Chang elastic constitutive of soil was used under the balance of the initial stress,while Davidenkov elastic-plastic constitutive under earthquake excitation.At last the effects of soil constitutive model,different soil materials,different earthquake wave and peak ground acceleration,total stress method and effective stress method on the seismic response of the site are investigated.