Research On Seismic Three-dimensional Dynamic Response Of Single-arch And Long-span Mortise-groove Grouting Prefabricated Metro Station

As an innovative method of metro station construction,prefabricated technology is very effective to solve many problems brought by the construction process of traditional integral cast-in-place metro station.The typical earthquake damage phenomenon of underground structure shows that the conclusion which the seismic capacity of underground structure is superior to that of above ground structure remains to be discussed.Compared with the integral cast-in-place metro station,the prefabricated metro station reduces the integrity when it bears the load due to the discontinuity of the joint stiffness and the separation of the joint,which makes it show weak seismic capacity when it bears the ground motion.This paper takes the single-arch and long-span mortise-groove grouting prefabricated metro station project located in the high seismic fortification intensity area of Northeast China as the engineering background,and analyzes the anti-seismic safety of mortise-groove grouting prefabricated metro station and integral cast-in-place metro station with the aid of ABAQUS.To reveal the relationship between the prefabricated joint separation and the seismic characteristics of the station,the nonlinear stiffness calculation theory of the shield segment joint is introduced into the joint separation of the prefabricated station,and the seismic analysis is carried out in combination with the response results of the underground station under the different earthquake.The main contents and conclusions are as follows:(1)Based on the application of equivalent linear viscoelastic constitutive model,the problems of geostress balance under complex contact,static dynamic boundary transformation and ground motion input are well solved.From the dynamic response effect of the station under the action of three different seismic waves,the coupling earthquake has obvious superposition effect on the station structure compared with the single directional earthquake,resulting in the increase of the station structure damage.It is suggested to use the coupling seismic wave as the dynamic source of structural safety evaluation.(2)Although the two stations meet the seismic requirements,the seismic capacity of the prefabricated station is significantly weaker than that of the cast-in-place station.The influence of the single directional and coupling seismic waves on the upper structure of prefabricated station is obviously different,and the difference of inter-story displacement angle between the upper layers of two stations is more than 50%.The damping effect of prefabricated station is more obvious than that of cast-in-place station,which consumes more seismic energy,resulting in the effect of acceleration amplification is not obvious.The stress concentration of prefabricated station structure is obvious,and the maximum difference of seismic stress between prefabricated station and cast-in-place station observed by numerical simulation is 28%.(3)The seismic input direction and its superposition effect will not change the weak position of the station structure(the maximum separation angle is observed at the 4L-4R joint),but the disorder of its effect on the structure is obvious,which will aggravate the asymmetric change of the structure.The maximum deformation and stress of the station under single directional earthquake are consistent with the peak time of seismic acceleration,while the maximum deformation and stress of the structure under coupling earthquake are ahead of the peak time of acceleration.(4)Based on the nonlinear stiffness theory of shield tunnel,the nonlinear stiffness index affecting the separation of joints in prefabricated station is obtained.Before and after the joint separation,the nonlinear stiffness relationships of the three groups of joints are consistent.The flexural rigidity of the same joint under the action of positive moment before separation is 34.33% ～ 42.72% higher than that under the action of negative moment,but they are basically the same after separation.The main reasons for the difference of seismic response between the two stations are that the bending rigidity of the 3L-4L(3R-4R)joint of the assembled station is more than 14% lower than that of the 2L-3L(2R-3R)joint,and the 4L-4R joint located at the key position of the structure causes vibration separation.