Seismic Dynamic Analysis Of Underground Structure Based On Finite Element Method

With the continuous development of economy and the acceleration of urban construction process,the development of underground space and the construction of underground transportation have become one of the effective ways to alleviate and solve the huge pressure of urbanization problems on human living space.However,With the frequent earthquake disaster occurrence in the underground structure such as subway,the seismic dynamic analysis of underground space structure has been paid more and more attention by seismologists around the world.In this paper,some problems related to the seismic dynamic analysis of underground structures by using the finite element method are studied,including artificial boundary and ground motion input,factors affecting the accuracy of finite element calculation and factors affecting the seismic dynamic of underground structures.In view of the above problems,this paper mainly completes the following work:(1)This paper introduces two kinds of commonly used artificial boundary,namely,free field boundary and viscoelastic artificial boundary.According to the theory of viscoelastic artificial boundary and its input mode of ground motion,the program of viscoelastic artificial boundary is written in FORTRAN,and the addition of viscoelastic artificial boundary is realized in ABAQUS software.Finally,the correctness of the program of viscoelastic artificial boundary is verified by a classical example.(2)In the finite element analysis of underground structures,the accuracy and convergence of the calculation results are largely affected by the finite element mesh size.In order to analyze the influencing factors of the accuracy,ABAQUS is used to establish a three-dimensional free field finite element model,and analyze the influence of the mesh size,element type and element order on the surface and bottom boundary displacement stress response of the free field soil.(3)A three-dimensional finite element model of soil underground structure is established.The boundary of the model adopts the viscoelastic artificial boundary realized in ABAQUS.According to the results of the previous discussion,the grid size and element types are selected.The displacement response,acceleration response and stress response and other dynamic response are analysed.