Seismic Analyses For Expansion Of Metro Stations Under Shield Running Tunnel

The seismic research of underground structures of urban subways is an important research topic in the engineering field in recent years.Constructing Metro Stations using shield tunneling is an important construction method for urban metro stations under special conditions.The structure of the station formed by this method is complicated in force and special in section type.The research on the seismic performance of this type of station structure,on the one hand,can improve the design and construction system of the subway station construction by the shield expansion method,on the other hand,can serve as a reference for the seismic research of complex cross-section structures in the future,which is important to research.Based on the research of the research group about this topic,the numerical calculation software such as MIDAS_GTS and ABAQUST is used to establish the reaction displacement model,the dynamic time history analysis model of horizontal and vertical simultaneous input ground motion and the static elastoplastic Pushover analysis model.These models were used to analyze the seismic performance of three different types of metro stations expanded used shield tunnels.The main work and conclusions are described as follows.1.The MIDAS_GTS software was used to establish the load-structure model of the reaction displacement method.The lateral change of the structure and the internal force of the structure were analyzed.The seismic performance of the structure was evaluated preliminarily.The inter-layer drift angle at the transverse channel of the scheme of expanding metro station with inner diameter 7m shield tunnel and the scheme of expanding metro station with inner diameter 8.1m shield tunnel exceeded the value specified by the specification.In addition,all interlayer displacement angles meet the requirements of the specification;2.The MIDAS_GTS software is used to establish a three-dimensional dynamic time-history analysis model.For each station structure expanded through tunnel,the horizontal single ground motion input and the horizontal and vertical ground motion simultaneously input were inputted to research the structural seismic response.It is found that the input of vertical ground motion has little effect on the deformation and internal force response of the structure(increased by 20%?30%),while the influence of the structural axial force of the column is significant(about 200%increase).Therefore,the effect of vertical ground motion should be fully considered when seismic analysis of the shield tunnel is extended.3.Using the ABAQUS finite element analysis software,the Pushover analysis model was established to perform static elastoplastic analysis of the metro station structure expanding from shield tunnel.The plastic behavior of the concrete structure was simulated by the concrete damage plastic constitutive model.The Mohr-Coulomb constitutive model was used to simulate the plastic behavior of the formation.The analyses showed that as the seismic input increased,the relative deformation of the structure also increased.When the peak ground relative displacement(PGRD)is greater than 5cm,the structure enters the elastoplastic working state,when the peak ground relative displacement(PGRD)Above 15 cm,the structure tends to break.