Study On The Displacement Method And Failure Mode Of Underground Structure Considering The Interaction Between Soil And Structure

Urban rail transit has become an important way of public transportation in every major city in the world.It is generally believed that the underground structure is more earthquake-resistant than the ground structure.However,many underground works,such as the subway station and underground tunnel,were seriously damaged in 1995 during the Kobe earthquake in Japan.There were also cases of tunnel destruction in WenChuan earthquake in 2008.Therefore,it is very important to study the seismic characteristics of underground structures.In this paper,Abaqus is used to develop the Umat interface to write the equivalent linear viscoelastic soil model,and the equivalent linear analysis is realized in finite element software.Based on the equivalent linear analysis method,considering the flexibility ratio,structure size,structure,buried depth,soil structure,the characteristics,the ground motion characteristics,the influence of such factors as underground structure under the action of the earthquake in the systematic were investigated.Based on the law of interaction between soil and structure,the error source of traditional reaction displacement method is analyzed,and the influence of structure on soil is explored.By analyzing the error of the result,summarizing the flexibility than the response displacement method to calculate the influence law,traditional response displacement method for stiffness are given,and put forward underground structure response displacement method considering the interaction between soil and structure,and verified by a practical engineering example.Finally,considering the influence of the factors of strata and depth,using the pushover method,the failure mode of different forms of underground station structure and current specification used in the seismic design of indexes are analyzed and summarized,and the design process is given rationalization proposals.The main achievements of this paper are as follows:(1)The response law of soil-structure interaction is summarized.In this paper,the definition method of the rotation coefficient of underground structure under earthquake action is given,and the influence of different factors is taken into consideration,and the law of soil-structure interaction is studied.It shows that under the earthquake action,the stiffness difference between soil and structure has significant influence on its response law.The flexibility ratio,as the index of relative stiffness of soil and structure,can reasonably reflect the law of difference between soil and structure,and the farther the degree of flexibility ratio is,the more obvious the deformation and rotation effect of the structure is.The ratio of flexibility ratio,poisson's ratio and burial depth are the three main factors affecting the interaction coefficient curve and rotation coefficient curve.Theinfluence of the rest factors can be ignored.(2)An underground structure reaction displacement method considering the interaction between soil and structure is proposed.In this paper,the error sources and error results of the reaction displacement method are analyzed,and the new seismic design method is given.It shows that The structure of different flexibility ratio is different,and the soil deformation is no longer affected by the structure at about 3 times the width of the lateral structure.The more the flexibility ratio is,the greater the error of the traditional reaction displacement method is,and the application range of the traditional reaction displacement method is roughly between 0.5 and 2.In this paper,the calculation method of underground structure reaction displacement is simple,and the calculation accuracy is improved obviously,which can be used as a reference method for seismic design of underground structure.(3)The failure modes of underground stations with different structures are summarized and the rationality of seismic design index is given.It shows that the failure modes of different structures are generally similar in different depth and stratigraphic conditions.The plastic hinge first appears on the middle plate,and with the yield on the bottom of the side wall,the top and bottom of the side wall also enter the plastic zone,and the structure tends to be damaged.The larger the depth,the smaller the displacement Angle between the elastic layer and the plastic layer.The better the formation conditions,the smaller the displacement Angle between the elastic interlayer and the plastic layer.The limit value of inter-storey displacement Angle is used to determine the elastic limit state of the underground structure may not be applicable,and the determination of the plastic limit state can be considered as the basic application for practical engineering design reference.