| The initial shield tunnel lining is made up by a plurality of prefabricated arcurate segment through the connecting bolt, due to the presence of the bolt and dynamic response characteristics of the initial shield tunnel lining are different from overall cast-in-place tunnel structure and the vulnerability is its greatest feature. In recent years, many big cities are in use of the shield method in construction of metro, and those cities located in the high intensity area is not in a few, therefore, the seismic performance of the shield tunnel has aroused widespread concern of scholars.This paper carries out research based on a shield tunnel as an example, Kunming City Stadium station to liangjiahe interval, including form analysis of seismic disasters in shield tunnel, seismic wave selection and correction, the establishment of the equivalent model of shield tunnel, the comparative analysis of the dynamic response in traveling of the seismic wave under uniform excitation and traveling wave excitation shield tunnel response under, the influencing factors analysis of response of the shield tunnel in traveling wave excitation, etc. The specific content of this paper is:(1) by consulting the domestic and foreign document materials, the damage accident of metro shield tunnels at home and abroad was collected, and the main damage forms and disaster causing mechanism of the shield tunnel were analyzed.(2) The research work such as seismic wave filtering, spectrum analysis, filtering, baseline correction, model establishment, determination of calculation parameters and boundary conditions, etc were carried out based on the free field boundary, viscous boundary, separation technology of the wave field, applied method of damping system in FLAC3D software and a series of theory such as Fourier transform, power spectrum and least square method in seismic wave analysis software Seismosignal, according to the geological survey data of the city stadium station to liangjiahe interval in Kunming City metro 3 lines.(3) the comparative analysis of different response of consistent input and travelling input of the seismic wave by time-domain method with FLAC3D, response characteristics of shield tunnel under the travelling wave excitation were analyzed from the four factors influencing response of shield tunnel:waveform, apparent velocity, structural style and different surrounding soil strength.(4) some constructive suggestions about the earthquake resistance of shield tunnel were put forward.The results of the study show that:(1) disaster forms as bolts loose, cracking of shoulder and foot in cave and serpentine bend are prone to happen in shield tunnel in the earthquake. Among them, feature of the serpentine bend obviously show the traveling wave effect of ground motion in earthquake.(2) by comparative analysis of dynamic response of shield tunnel with uniform input and traveling wave input, the results show that displacement response under the traveling wave effect lag behind of that is under the uniform incentive and the peak lateral displacement, the relative peak lateral displacement traveling wave effect of the structure under, the peak absolute value of the maximum (minimum) principal stress and opening amount of the bolt are greater than those in uniform excitation. The response of shield tunnel under traveling wave effect is more in line with the characteristics of the earthquake disaster and serpentine bend will appear in the traveling wave effect and it is difficult to embody the characteristics in uniform excitation. Therefore, it is necessary to use traveling wave excitation in seismic analysis of shallow-buried shield tunnel in large span.(3) the seismic waveform, the structural form, the strength of the surrounding soil and the apparent wave velocity are the factors that affect the structural response in the traveling wave effect. The calculation results show that the greater seismic wave acceleration is, the greater the trend of the response of the structure will be; changes in the strength of shield tunnel segment and bolts have little effect on the displacement of the structure, if the strength of the segment increase, the internal force in the earthquake also increases. But if the bolt strength increase, the internal force of the segment will reduce; changes in the strength of the surrounding soil will have a greater impact on the response of shield tunnel, with the increase of soil strength, the lateral displacement of the structure show a decreasing trend, but the structure internal show an increasing trend, and stress concentration appear in place where structural section form change; apparent wave velocity is also the key factor that influences the structural response; the larger apparent velocity is, the smaller the displacement and internal force of the structure will be.The innovation of this paper include:(1) many scholars are less likely to consider the traveling wave effect in the analysis of seismic response of shield tunnel, but the paper carry out seismic response of shield tunnel analysis and research by the 3D finite difference method, and adopt traveling wave input method more in line with reality combined with engineering example mode; (2) the paper adopt the Shell - spring model and soil structure coupling model, which not only reflect the interaction between the segment and the bolt under the earthquake, but also reflect the interaction between soil and structure. (3) the propagation of the shear wave and the compression wave could be simulated at the same time by using the fully nonlinear time history analysis, and the permanent deformation of the soil and the structure in the earthquake could be calculated by large-deforming calculating method. |
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