Research On Seismic Design Of Underwater Large-diameter Shield Tunnel

In recent years,major cities have chosen the fast,clean and efficient underground rail transit to alleviate the pressure of the above-ground traffic.In China,more than 20 first-tier cities have basically completed the construction of underground rail transit.More than 40 other cities are planning to build subways.China will be in the wave of subway construction for a long time.China's research on seismic behavior of subway started late,and there's no complete theoretical system.In the case of structural seismic response analysis,the input of seismic waves usually adopts the uniform excitation method.For large-span structures,the seismic variability has obvious influence on the structure,thus the traveling wave excitation input method should be adopted.However,the research of tunnel ground motion law under the excitation of traveling wave is not deep enough.research is not deep enough.Therefore,it is necessary to further study the dynamic response of shield tunnel under traveling wave excitation.This paper relies on the shield tunnel engineering example--Jinan Yellow River tunnel project--to carry out research,including the analysis of shield tunnel seismic hazard form,one-dimensional soil seismic response analysis,tunnel dynamic time-history response analysis,and comparative analysis of dynamic response characteristics of shield tunnel under traveling wave excitation and consistent excitation.The specific contents include:(1)Domestic and foreign literatures were reviewed to collect the seismic damage accidents of shield tunnel at home and abroad,and the main earthquake damage forms and earthquake damage mechanism of shield tunnel were statistically analyzed.(2)The code for seismic design of urban rail transit structures GB50909-2014 stipulates that: "Seismic design of tunnel structures shall calculate the lateral seismic response according to the requirements of fortification".Based on the Jinan Yellow River tunnel project,a one-dimensional soil seismic response analysis model was established to analyze the most unfavorable section of the structure in the middle of the river under the action of fortification and rare earthquakes.(3)The seismic force and static load calculated by seismic response analysis ofone-dimensional soil layer are combined,and the plane analysis model is established by Sap84 finite element software.The results of this case show that: In rare earthquakes,the internal force is slightly increased and the axial force,shear force and bending moment are increased by 26%,24% and 11% respectively compared with the fortification earthquakes.The maximum axial force occurs at the waist of the arch,the maximum bending moment occurs at the top and bottom of the arch,and the maximum shear force occurs at the bottom of the arch.The maximum diameter deformation rate of tunnel structure under earthquake conditions is 1.68‰,within the limit of 4‰~6‰ stipulated in code for seismic design of urban rail transit structures(GB50909-2014).(4)Tunnel longitudinal structure seismic response calculation,using the finite element analysis software Midas GTS/NX 3D tunnel dynamic time history response analysis model is set up,using time domain analysis method to analyse fortify and rarely met(E2,E3)earthquake under the action of tunnel seismic dynamic response calculation,calculated the seismic response of the tunnel and comparative analysis is consistent with the response characteristics of traveling wave under the condition of the ground motion input and differences.(5)The three Angle(0 °,45 °,90 °)seismic waves,the characteristics and differences of the dynamic response of the tunnel are studied to find out the most adverse incident direction.The results of this case show that the displacement and internal force of the tunnel under the excitation of in-line waves are greater than those under the uniform excitation.When the transverse shear wave acts,the tunnel displacement is mainly dominated by the transverse displacement.The displacement at the waist of the arch is greater than that at the top and bottom of the arch.The maximum relative displacement at the arch waist is 55.21 mm.The maximum diameter deformation rate was 3.63‰;Under the action of longitudinal compression wave,the longitudinal displacement is mainly along the tunnel,while the transverse and vertical displacement is small.The displacement at the waist of the arch is greater than that at the top and bottom of the arch.The maximum relative displacement of the arched waist is 36.55 mm.The maximum diameter deformation rate was 2.4‰;The tunnel is subjected to a 45 degree compression wave excitation condition along the longitudinal direction.The maximum relative displacement of the top and bottom of the arch was30.97 mm,and the maximum diameter deformation rate was 2.04‰.Through the above research,the dynamic response of Jinan Yellow River tunnel under the action of uniform excitation and traveling wave excitation is deeply analyzed.Under the excitation of traveling wave,the amplitude of each point in the tunnel is not consistent at the same time,which reflects the variation of the seismic wave.Therefore,the traveling wave excitation should be used to analyze the underwater large shield tunnel.