Seismic Response Analysis Study Of Transverse Section Of Excavated Tunnel Based On The Different Geological Conditions

Japanese highway two section of excavated tunnel section are taken by this paperas the research object: one is in the soil which has a large difference in stiffness and theother is in soft soil. Building up the finite element analysis models of tunnel crosssections by using the software of finite element called TDAP III and analyzing themodels which include soil (plane strain element) and structure (beam elements) underlarge earthquake by using response acceleration method and dynamic response historyanalysis method. To apply the rang of static analysis of underground tunnel section bycomparing the results of seismic response analysis and the soil equivalent stiffness andR-O nonlinear model was discussed in order to reveal the influence for structuralengineering seismic design. The main contents and results of research are as follows:Firstly, research on related theory and analysis method. Selecting the Pseudo-staticand dynamic response history analysis method as method for seismic analysis in thispaper by comparing the advantages and disadvantages of seismic analysis methodsincluding the static and dynamic analysis method.Secondly, set up two-dimensional fem model of tunnel cross section. To determinethe scope of soil and set up the soil (plane strain element)-structure (beam elements)integral model based on considering the material nonlinearity of structure by usingthe software of finite element called TDAP III. Introduce the characteristics of seismicwaves, the damping ratio setting and so on.Thirdly, Based on soil equivalent stiffness analyze the two-dimensional fem modelof closed double-deck tunnel by using Pseudo-static method and dynamic responsehistory analysis method. Through bending proofread, shear proofread, deformation,and the hysteresis curve of those key parts, it shows that: in the case of the soil whichhas a large difference in stiffness, the relative deformation and shear strain of soil areminimal. The static analysis method as the method for seismic analysis can meet thedesign requirements and safety guarantee of tunnel structure.Fourthly, Based on soil equivalent stiffness and R-O nonlinear model, analyze thetwo-dimensional fem model of opening double-deck tunnel by using Pseudo-staticmethod and dynamic response history analysis method. Through bending proofread,shear proofread, deformation, and the hysteresis curve of those key parts, it shows that:Dynamic analysis based on equivalent linear of soil use Rayleigh damping to evaluate the damping of the model, it can’t fully response the nonlinear energy dissipationcapacity of soil under strong earthquake. Soil stiffness is always the same when theshear strain is even large what make the structural response larger, in some times itcan’t meet the design requirements. But using the nonlinear model of soilcan directly consider the nonlinear energy dissipation capacity of soil under strongearthquake, the soil stiffness became smaller when the shear strain is large. The effectof soil for structure became smaller to reduce the seismic response of structure evenwhen the relative deformation and shear strain of soil are the same by using soilequivalent stiffness and R-O nonlinear model.