3D Finite Element Seismic Analyses For Yellow-River-Crossing-Tunnel Based On Overal Model

South-to-North water diversion is a major strategic measure for the fundamentalsolution of the problem of critical shortage of water resources in North China. TheYellow-River-Crossing Project is a key project in the central line of theSouth-to-North Water Diversion Projects and its main purpose is to effectivelytransfer the water from the south bank to the north bank of the Yellow River. Theseismic fortification intensity along the water-transferring line reaches as high as8degrees, so seismic analysis should be done to assure the seismic safety of thoseunderground tunnels and shafts. The real noncontinuous deflections of the tunnels aswell as the effects of different geological conditions on the dynamic response of theoverall tunnel cannot be obtained from the current seismic analyses, which are allbased on local models of the tunnels or assume that the material properties areuniform because of the huge scale of the overall tunnel model, hugetime-consumption and the complicated dynamic nonlinearity of the materials andcontacts.In the thesis numeric seismic analyses for the3D finite element overall model ofthe Yellow-River-Crossing Tunnel were done based on the central difference methodand the fundamental theories of the dynamic interaction between the earth and thestructures. Artificial boundaries, dynamic contacting as well as parallel algorithemwere applied in the simulation performed on a high performance workstation. Themain contents and conclusions include：1. Made dynamic time-history analysis for the3D finite element overall modelof the tunnel, employing the homemade parallel computation software package basedon the explicit central-difference algorithm and considering the nonlinearities of thematerial properties and contact properties.2. Studied the effects of different boundary conditions and different correctionfactors of the artificial boundaries on the numerical results based on the overall3DFE model and the local3D FE model.3. Found the locations of the weakest links in the tunnels by comparing and analyzing the dynamic responses of the3D FE model under different loading pattern,different combinations of seismic loading and different construction stages. Resultsshowed that,1) correction factor of the viscoelastic artificial boundary had little effecton the numerical results, and overall3D FE models were suggested for seismicanalysis of the key important projects to eliminate the errors introduced by artificialboundaries.2) the relative displacements and torsion deflections between the shieldblades and the surrounding earth were small when the inner and outer linings wereboth under stress, for the pipes and the shield blades were bearing the loadings as awhole, and the torsional deflection between the shield blades and the surroundingearth under individual loading pattern was greater than that of the combined loadingspattern.3) the effect of the vertical earthquake input pattern on the displacementalong the river under combined loading pattern or individual loading pattern is smalland the major displacement resulted from the loading patterns was horizontal sheardisplacement along the river.