Seismic Response Analysis Of Subway Station In Weak Interlayer

With the popularization and construction of underground engineering in the large and medium-sized cities of China,the seismic safety of underground buildings has attracted more and more attention.The research on the anti-seismic field of underground structures in China is still in its infancy,and the relevant knowledge and research are still not thorough and exhaustive.The underground structures are more likely to be damaged when they are in complex geological environment,such as nonuniform stratum,soft soil,soft interlayer nearby and so on.At present,the studies on the seismic response of underground structures with weak interlayer are relatively few,but the adverse effects of weak interlayer on the anti-seismic performance of structures cannot be neglected.Therefore,it is of great significance to study the seismic response of subway station structures in such complex sites.In this paper,a practical subway project is taken as the research background.A three-dimensional(3D)finite element model of soil-station structure interaction system is built on the platform of ABAQUS software.The automatic application of the viscoelastic boundary and the effective fluctuation input of motion are realizedis realized by using the Python secondary development program.Considering such factors as seismic loading waveform and the relative position of the station to the weak interlayer,the dynamic response of the typical double-layer three-straddle subway station in weak interlayer is studied,and the measures to reduce the earthquake damage of the weak interlayer are put forward.Through the analysis and comparison of the calculation results,some rules are found to provide references and suggestions for the anti-seismic design of subway stations in similar soft soil areas.The main research results are as follows:(1)The calculation model of subway station structure is established through the studies of such key questions as dynamic equilibrium equation solution,damping coefficient determination,boundary conditions,seismic wave selection and input,and the constitutive model selection of materials.(2)Take the Tianjin Wave and the Northridge Wave as the input ground motion and simulate the seismic response of free and station field sites in different earthquakes,the influences of the station structure on the nearby soil movement state are studied,and thedifferences of seismic waves with different spectrum characteristics on the structure acceleration,displacement and internal force variation laws are compared.(3)Without considering the effect of groundwater,it is assumed that no liquefaction occurs.According to different position relationships between the station and the weak interlayer,the internal force and the deformation laws of the station structure's key parts are analyzed,and special attention is paid to the relative horizontal displacement of the lateral station structure,the biggest displacement angle across layers of central column and the changes of the internal force.The results show that the structure's seismic response is minimal when the station is located above the weak interlayer.When the middle part of the station is located in the weak interlayer,the structure's seismic response is the largest,and its anti-seismic performance is the poorest.For a typical frame underground station,the central column with the largest internal force response is the most unfavorable force component,which should be specially considered in its design.(4)Based on the above research results,the effect of reducing the earthquake damage to the soft interlayer is studied from the aspects of structural stress and displacement by improving the stiffness of the station structure,changing the properties of the weak interlayer and piling under the station.The results show that the distribution of soil layer and the nature of soil layer have a significant difference on the dynamic response of the structure.In practice,it is more effective to use the short and dense piles found in the foundation or to increase the rigidity of the station structure.