Calculation Model And Dynamic Characteristics Of Embedded Foundation In Layered Soil

Because of the reduction of well-suited nuclear power plant sites such as rock foundations,and the need for nuclear power to develop inland,The seismic analysis of nuclear power plants under non-lithologic complex sites has important engineering value.The dynamic stiffness of foundation is the core of the substructure method to solve the problem of dynamic interaction between structure and foundation.In the current nuclear seismic code,solving the dynamic stiffness of the foundation,the homogeneous half space assumption is still used,that is,the dynamic stiffness of the embedded foundation is obtained by modifying the dynamic stiffness of surface foundation on the homogeneous foundation.However,in practical projects,many sites are characterized by horizontal stratified distribution.Therefore,the study on dynamic stiffness characteristics of embedded foundation in layered foundation is of great significance to the seismic design of nuclear power structures.The finite element calculation model of nuclear power plant,which contains layered foundation with Non-bedrock overburden,is large.Existing commercial finite element software,such as ANSYS,is prone to the shortcomings of insufficient memory and low efficiency in large-scale calculation,so a calculation method that can be solved on a large scale is required.Radiation damping,which is at infinite distance in the infinite domain of the foundation,is simulated by viscoelastic artificial boundary finite element model.And dynamic stiffness of foundation is solved by harmonic response analysis.The large-scale sparse matrix advanced solver is used in the solution process to improve the large-scale solution ability and computational performance of the calculation program.In order to verify the accuracy and engineering applicability of dynamic stiffness of the foundation calculated by the analytical method in this paper,first,the dynamic stiffness of the embedded foundation in the homogeneous foundation and layered foundation was calculated,next,the calculation results were compared with the numerical integration and the calculation results of ASCE4-98 code,and then,the influence of the supporting degree of the lateral wall around the foundation on the calculation results of the dynamic stiffness of the embedded foundation was discussed.First,designs different working conditions,and then,discusses the dynamic characteristics of layered foundation,after that,studies the influence of soil depth near the surface of site on the dynamic stiffness of embedded foundation and the influence of foundation elasticity on dynamic stiffness of embedded foundation in far and near field regions,moreover,refers to the revised coefficient of dynamic stiffness of embedded foundation of ASCE4-98 homogeneous foundation and discusses the influence of embedding depth of layered foundation on dynamic stiffness of foundation,finally,describes the dynamic stiffness correction factor of embedded foundation in layered foundation.The results show that considering the different support degree of the foundation sidewall around the foundation in the calculation process of the dynamic stiffness of embedded foundation has a great influence on the calculation accuracy.In the project,the depth of the layered foundation close to the surface of the site,the elasticity of the soil near the surface of the site,the relative position of the soil interface and the bottom surface of the foundation should be taken as important considerations for the analysis of the layered foundation structure-foundation interaction.