| Seismic design is a very important issue in the design of undergroundstructures of subway, but it was not well developed in China. This is partlybecause the dynamic response behaviors are not sufficiently understood, andthere are no simplified methods of analysis applicable to practical designing.Presented in this thesis are simplified methods of analysis for the evaluationof the deformation of subway tunnels under seismic loading, which are basedon analysis of dynamic soil-structure interaction. The curvature deformation along a subway tunnel is firstly investigated.Under the assumption of plane-strain, dynamic finite element analysis isconducted to examine the dynamic interaction between a subway tunnel andits surrounding soil medium subjected to longitudinally propagating shearwaves. Kinematical interaction is the dominant factor governing the tunneldeformation while inertial interaction plays an insignificant role. In somesituations, the deformation of the tunnel is overestimated by using theexisting conventional pseudo-static method. By introducing a dynamicreaction factor of soil medium to substitute the former static reaction factor,the conventional pseudo-static formulas are modified and they can providealmost the same results as dynamic FE analysis. Then the pseudo-staticmethods of dynamic analysis methods are extended to three-dimensionalformat by using elastic theory and FE analysis, so that the influence of thecross section height of the tunnel can be taken into account. Finally, acomparison is made between formulas in pseudo-static and dynamic formatsand also between two-dimensional and three-dimensional formats.Subsequently suggestions on seismic design are obtained. Racking deformation of the cross section of subway tunnel is also studied.Firstly, the racking deformation of a tunnel in infinite, homogeneous, - II -isotropic, elastic medium and the shear deformation of the soil medium areinvestigated using static FE method. Correspondingly, an empirical formulato determine the interaction factor of the deformation of structure to that ofsoil medium is derived. Then, dynamic interaction between tunnel andsurrounding soil medium is investigated with dynamic FE analysis, in whichthe influence of wavelength and inertial characteristics of the tunnel areinvestigated. Based on the above analyses, a simplified method of analysis toestimate deformation of structure is developed. In this new method, aninteraction factor is calculated with the empirical formula previously derived,then the racking deformation of the tunnel is determined thorough multiplyingthe interaction factor to the free field shear deformation of the surroundingsoil layers, which can be obtained by using equivalent-linear earthquake siteresponse analysis or empirical formulas. Finally, the new simplified methods of analysis are used as a typicalexample of application for the evaluation of curvature deformation andracking deformation of practical subway tunnels in Beijing Metro Line 5. Theanalysis process can serve as demonstrations on these simplified designmethods.
|
PDF Full Text Request