Study On The Effect Of Metro Station Constructed By PBA Method On The Structural Deformation And Driving Performance Of Adjacent Existing Station

Over the past two decades,China’s urban rail transit has developed rapidly.Up to now,the construction mileage and operation mileage are the first in the world,and the rail transit in many cities has realized network operation.The large-scale construction of rail transit and the limited urban underground space lead to more and more adjacent or crossing construction between rail transit lines and lines,lines and stations,and stations and stations,and the impact of new rail transit projects on the operation safety of adjacent existing rail transit lines becomes more and more prominent.The PBA method is commonly used in the underground construction of metro stations in urban centers,which can effectively reduce the ground subsidence during the construction process and ensure the construction safety,but there is a lack of study on the deformation effect of metro station constructed by PBA method on the adjacent existing operational station structure.This paper is based on the Wangfujing Station of Beijing Metro Line 8 adjacent to the existing Wangfujing Station of Line 1 project,and adopts numerical simulation to analyze the effect laws of the new station on the ground and operational station structures during the construction process,summarizes the coordination relationship between structural deformation of the existing station and track irregularities,determines the step-by-step control index of structural deformation of this project;makes a parametric analysis on the structural deformation of the existing station caused by the main effect factors,calculates the reliability of the existing metro station structure under the coupling effect of multiple factors;and studies the effect of track irregularities caused by construction on the dynamic performance of train operation,the main study contents are as follows:(1)The unified 3D finite element model of the new station and adjacent existing station is established by MIDAS GTS NX to simulate the ground deformation caused by the construction process of the PBA method in the new station,and the results are compared with the measured values,which shows that the finite element calculation results are in good agreement with the site measured values so that the accuracy of the model is verified.(2)The deformation law of ground and existing station structures caused by the four main stages of PBA method: pilot tunnel excavation,pile-column-beam construction,arch buckle excavation and station excavation,and the coordination relationship of the existing structures are analyzed: the structural deformation of the ground and existing station all show the change trend of “large in the middle and small on both sides”,and the main effect area is within 50 m on both sides of the center line of the new station.The stages of pilot tunnel excavation and arch buckle excavation are the main influence stage of structural deformation.The existing station structure deformation and the track irregularities basically show linear coordination relationship,and with the increase of structure deformation,the track irregularities also increase.Based on the principle of displacement distribution control,the step-by-step control index of structural deformation of this project is determined,and the control values of vertical deformation are 1.43 mm,1.97 mm,2.82 mm and 3.00 mm,and the control values of horizontal deformation are1.12 mm,1.17 mm,1.28 mm and 1.30 mm,in which the alarm value is taken as 80% and the warning value is taken as 70%.(3)On the basis of the finite element model,the deformation law of the existing station under the single factor changes(pilot tunnel excavation sequences and lining structure parameters and so on)is analyzed.Based on the reliability theory of the displacement criterion,the Kriging-IS method is used to establish the proxy model of the existing station structure deformation under the coupling effect of multiple factors,and the reliability and failure probability of the existing station structure under different pilot tunnel excavation sequences are calculated: when single factor changes,the structural deformation of the existing station decreases with the increase of the initial support thickness,the concrete grade of the initial support and secondary lining respectively,in which the effect of the concrete grade of the secondary lining on the structural deformation of existing station is smaller.When multiple factors are coupled,the difference between the predicted values of the Kriging proxy model and the finite element simulation values is small,so that the effect law of the random variables on the structural deformation of the existing station can be better fitted.The reliabilities of the existing station are 7.4573 and 7.4258 respectively when adopting the pilot tunnel excavation sequences of “top then bottom,side then middle” and “top then bottom,middle then side”,which have better structural stability and reliability.While the reliabilities of the existing station are only 4.0070 and 3.9204 when the bottom pilot tunnels are excavated in priority.The result shows that the priority excavation of the top pilot tunnels can effectively control the structural deformation of the existing station and increase the reliability of the structure.(4)The coupled vehicle-track dynamics model is established by SIMPACK.Combined with the derailment coefficient,wheel load reduction rate and train running stability indexes,the effect law of the new station construction process on the train running dynamics performance of the existing station is analyzed: the values of the indexes increase as the construction stage progresses.Before and after the construction,the derailment coefficient,wheel load reduction rate and train running stability indexes are increased respectively from 0.053,0.088,1.185 and 1.176 to 0.174,0.184,1.561 and1.554.The dynamics performance of the train after construction are calculated at 40km/h,60km/h and 80km/h,and the result shows that all the indexes of the dynamics performance increase with the growth of the running speed,and when the running speed is 80km/h,the horizontal stability index increases to 2.236,which is close to the limit value of excellent grade.