| With the intensification of the underground railway network,new subway stations or tunnels inevitably need to pass through the side or below the foundation of urban bridges.The deformation and movement of the ground caused by subway construction may cause the settlement of adjacent bridge foundations and bear additional stress.If the settlement or additional stress of the bridge foundation exceeds a certain level,it may cause damage to the bridge,or aggravate the existing damage,affect the normal use of the bridge and even cause safety problems.Therefore,in order to ensure the safety of adjacent bridges and subway engineering For construction safety,it is necessary to study the impact of subway construction on adjacent bridges and take corresponding construction countermeasures.The engineering background of this paper is the Anzhenqiao Station of Beijing Metro Line 12.Anzhenqiao Station is a subsurface excavated and separated island subway station.It is constructed by the PBA construction method.The station area is mainly composed of water-rich clay soil.The station is arranged in Beisan.The bridge area around Anzhen Bridge,which consists of Anzhen East Bridge,Anzhen West Bridge and the retaining wall between the two bridges,has the following characteristics:(1)The main structure of the station crosses Anzhen East Bridge and Anzhen West Bridge at a close distance,and the horizontal distance between the pilot tunnel of the station and the piles of Anzhen West Bridge and the enlarged foundation of Anzhen East Bridge is less than 2m;(2)Anzhen East Bridge and Anzhen West Bridge have very special structures and foundation types,both of which are inclined-leg steel bridges.The west bridge adopts precast pile foundation and cap,and the east bridge adopts cast-in-place expanded foundation;(3)The main structure of the station within the scope of the Anzhen East Bridge and the No.2 and 4 construction cross passages on the north and south sides of the station will form a spatial cross structure.The superimposed effect of the two constructions will cause the expansion of the Anzhen East Bridge to be affected.The impact of excavation disturbance has increased;(4)The connecting passage between the left and right lines of the main body of the station has repeatedly passed through the Anzhen Bridge area,which has a significant impact on the retaining wall between the two bridges.This article uses FLAC3 D software to carry out modeling calculations,combined with relevant literature and theories,and analyzes on-site monitoring data to ensure the safety of Anzhen East Bridge,Anzhen West Bridge and the retaining wall between the two bridges.A systematic and in-depth study was conducted on the impact of the construction of a dig-separate metro station on the adjacent special structure bridges and retaining walls.The study showed that:(1)By analyzing the relative positional relationship between the station and the Anzhen East Bridge and Anzhen West Bridge and the scope of the excavation,the risk level of crossing the two bridges at the side of the station is determined to be very risky,and the relevant design materials are consulted to determine The deformation control indicators of the two bridges are discussed,and the construction principle of“reinforcing the bridge foundation first and then crossing the subway station” must be adopted for the adjacent Anzhen East Bridge and Anzhen West Bridge.(2)Anzhen West Bridge is a special structure bridge with oblique leg steel structure with pile foundation.Through the study of station construction procedures and arch buckle scheme,the failure characteristics of surrounding rock,the stress of station structure,the characteristics of stratum deformation and the settlement of bridge foundation have been studied.Comparative analysis,the construction process of the main structure of the station using the top-down method and the construction of the second lining of the station using the "continuous buckle arch,buckle arch length of5m" buckle arch plan,and calculate and analyze the protection effect of the isolation pile on the Anzhen West Bridge,The calculation results show that the installation of isolation piles can reduce the settlement of the foundation of Anzhen West Bridge.(3)Anzhen East Bridge is a special structure bridge with oblique-leg steel structure.The main structure of the station and the No.2 and No.4 construction cross passages on the north and south sides of the station will form a spatial cross structure.The superimposition effect of the two constructions will affect To the safety of the Anzhen East Bridge,in order to reduce this impact,the FLAC3 D numerical simulation software was used to calculate and compare the "advanced deep hole grouting only in the cave" and "advanced deep hole grouting in the cave and the installation of isolation piles." The effects of the two bridge protection measures show that the use of the "advanced deep hole grouting in the cave and the installation of isolation piles" protection measures can effectively reduce the settlement of the bridge foundation.(4)Aiming at the characteristic that the connecting passage between the left and right lines of the main body of the station has crossed the Anzhen Bridge area many times and has a significant impact on the retaining wall between the two bridges,in order to study the influence mechanism of the construction of the station and the connecting passage on the deformation of the retaining wall,it is proposed Effective protection measures,using numerical simulation methods to study the changing laws of deformation indexes such as absolute settlement,differential settlement and inclination rate of retaining walls under the influence of station and connecting passage construction,and to reinforce retaining walls and retaining wall foundations with anchor cables.The protective effects of grouting,setting up isolated piles and advanced deep hole grouting in the cave were analyzed.According to the calculation results,the final protection measures are determined as anchor cable + isolation piles + advanced deep hole grouting in the cave. |
PDF Full Text Request