Transverse Seismic Response Of In-service Shield Tunnel Considering Influences Of Frame Structure

In the past decades,the seismic damage to underground structures has been frequently observed during recent strong earthquakes,so the seismic performance of subway tunnels which constitute critical component in infrastructure should be paid more attention.The surface building often exists near the tunnel,and the joint-bolt corrosion and other lining deterioration are common phenomenon during operation period.On the one hand,the presence of surface building alters the stress field and the propagation path of seismic waves,thus affecting the seismic response of shield tunnel.On the other hand,the joint-bolt linking two adjacent segments is an important component for shield tunnel,which deterioration performance level directly influences the service life of shield tunnel,while their effects on the seismic response mechanism of shield tunnel is not clarified.To this end,the nonlinear dynamic finite element method,random field theory and Monte Carlo simulation approach are employed to study the transverse dynamic response and influencing mechanism of in-service shield tunnel in consideration of raft foundation frame structure and joint-bolt corrosion.On this basis,the seismic fragility analysis is further carried out to assess seismic performance of in-service shield tunnel.Therefore,it is of great theoretical and engineering guiding significance to seismic design,operation as well as maintenance and disaster prevention for shield tunnel.The main research contents and results include:(1)By comparing numerical results with experimental results,including full-scale tests of reinforced concrete lining segment and segment joint,shaking table modet tests of soil-structure and tunnel-soil-surface building;the applicability of material constitutive models in terms of concrete,steel rebar,joint-bolt and soil are verified;and the reliability of simulation methods reffering to soil-structure interaction and segment joint are also validated employed in the numerical model.(2)The influencing mechanism of newly-built raft foundation frame structure on the transverse seismic response of shield tunnel is revealed,and the significance of segment joint on the seismic performance of shield tunnel is clarified based on the integral nonlinear dynamic analysis of tunnel-soil-surface building.The push as well as compression deformation and the considerable change of soil stress state as well as moving state around the tunnel lead to much higher dynamic responses of in-service shield tunnel,and the seismic effects of frame structure increase and then decrease with an increase in the distance between the frame structure and the tunnel,when the frame structure is located at one side of the tunnel structure.The effects of frame structure increase with a decrease in the burial depth of the tunnel.There is obvious stress concentration of compression to the lining concrete at segment joint.The mechanical behavior of joint-bolt is closely related to the dislocation and opening deformation of segment joint,and the plastic deformation of joint-bolt is mainly concentrated near the segment joint surface.(3)The corrosion effects of steel joint-bolt on the seismic response of in-service shield tunnel are clarfied combing with nonlinear dynamic analysis,random field theory and Monte Carlo simulation.The bolt deterioration decreases the tensile damage of the lining segment to some extent,while significantly increases the joint deformation and bolt plastic deformation,which increases with the increase of bolt deterioration degree.The sapatial variability of bolt corrosion marketly influences the distribution of joint deformation,and the discription and uncertainty of joint deformation increase with the increasing service life of shield tunnel.(4)The seismic performance levels of in-service shield tunnel are evaluated,and the effects of raft foundation frame structure as well as joint-bolt corrosion on seismic response of shield tunnel are calrified through developed seismic fragility curves based on incremental dynamic analysis(IDA),in which the tensile strength of lining concrete and joint deformation are adopted as damage index.The existence of raft foundation frame structure signifcantly enlarges the damage probabilities of shield tunnel.The influence of bolt corrosion on the seismic fragility of shield tunnel is very small at the primeval years during the service period(about the initial 30 or 40 years based on the assumed conditions in this study),and then the damage probabilities of tunnel obviously accelerate with the development of bolt deterioration.