Study On Seismic Performance Limitation Of Diameter Deformation Rate Of Shield Tunnel

A large number of urban rail transit structure have been constructed in China.However,due to functional limitation of rail transit structure and lag in survey of urban active faults,more and more shield tunnels cannot avoid or move away from seismic faults effectively,so that shield tunnels will be affected by strong earthquakes.Subway plays a role of lifeline engineering in urban transportation field.Every day,a large number of passenger were transported by subway.If subway stops due to an earthquake,it will bring some serious negative impact on society inevitably.In addition,shield tunnel is expensive to bulid,once it destroy,apart from damage concealment and repair difficulty and bring more serious direct and indirect losses else.Therefore,there are important significance for economic and society to ensure the seismic safety of shield tunnels.Base on model test of segment ring of shield tunnel,limit value of diameter deformation rate of seismic performance is studied.The main research contents are as follows:(1)Summarized earthquake damage record of shield tunnel,obtain main types and characteristics of shield tunnel damage.Summarized and analyzed the research status of the seismic performance index system and performance indicators of the engineering structure to select the diameter deformation rate as an index of shield tunnel seismic performance.(2)Shield tunnel segment structure model testTest was carried out on shield tunnel segment structure model with geometric similarity ratio of 1:20 and weight similarity ratio of 1:1 to control similarity of various physical and mechanical parameters.According to test results,influence rule of structural deformation,internal force,buried depth and assembling methods of segment ring under seismic load are analyzed.(3)Base on the experimental data,influence of buried depth and assembling methods on diameter deformation rate are analyzed.Analysis result of internal force-loading step,displacement-loading step change curve of the segment ring shows elastic-plastic demarcation point and the instability critical point of the segmental ring of the shield tunnel and gave suggested,diameter deformation limit values corresponding to the elastic plastic demarcation point and the instability critical point.