The Floating Response Of Subway Station In Liquefied Field Due To Seismic Vibration

With the development of economy in our country,the subway,as a new type of transportation tool,plays an important role in the transportation industry.In China,such as Beijing,Shanghai,Guangzhou and other big cities,the development of the subway station is fast.Subway can not only improve the phenomenon of urban traffic congestion,but also reduce environmental pollution,which has a positive effect on city development.However,any building has to be vulnerable and the subway station is greatly affected by the earthquake disaster,which is likely to cause huge economic losses.Therefore,it is very meaningful to study the seismic response of subway station:(1)In this paper,a FEM-FDM coupled method is proposed for numerical calculation.To deal with the material and geometrical nonlinearity of liquefied soil,the cyclic elasto-plastic constitutive model and the updated lagrangian formulation is applied.(2)The influence of seismic acceleration on liquefaction of subway station is studied in this paper.The peak value of seismic acceleration0.05 g,0.1g,0.2g,and 0.3g wereacted on the subway station respectively.Then the excess pore water pressure ratio curve and displacement curve,the excess pore pressure ratio and displacement nephogram were analyzed to indicate the liquefaction degree of soil around the subway station and its final floatation displacement.The sdudy on final floatation displacement show that with the increase of ground motion load,the liquefaction area around the subway stationand the floating displacement increase d.(3)The influence of buried depth on seismic liquefaction of subway station is studied.The subway station models with different depth,that are d=3m,d= 5m,d=7m and d=9m,are set up respectively,which are studied for the performance under different ground motion load.And the excess pore water pressure ratio curve and displacement curve,the excess pore pressure ratio and displacement nephogram were analyzed for liquefaction degree of soil around the subway station,and the comparison of final floatation displacement shows that with the increase of depth of subway station,the floating displacement decreased.(4)Research on anti-uplift measures of anti-uplift piles(LP=25m)and barrier walls(LW=1m from subway station)for subway station are carried out for displacement time history curve and the displacement nephogram,which are compared with that without measures,and the reduction degree of the floating displacement is analyzed.The displacement time history curve and the displacement nephogram are compared with that of the no measures.And by changing the length of the uplift piles(LP=10m,LP=15m and LP=16m)and changing the distance between the barrier walls(LW=0m,LW=2m and LW=14m)and subway station,the optimal anti-floating measures are obtained.The anti-uplift piles and the barrier walls block the flow of the liquefied soil,so the displacement of the subway station is decreased.Based on the numerical simulation of the floating response of subway station in liquefied field due to seismic vibration,it is of great significance to the construction of underground structures such as subway stations and the promotion in project.