Research On The Impact Of Newly Built Pile Foundations On Adjacent Metro Tunnels And Old Bridge Pile Foundations

In order to solve the problem of urban traffic congestion,things have been done in expanding the scale of metro construction and increasing the approaching projects linking bridges and tunnels,and new constructions started between excited tunnels and bridges are common to be seen.To improve the traffic condition in Shenyang,the capital of Liaoning Province,the local government has done the work of the extension of the Changqing Bridge since 2018.The original four-lane bridge now has been extended to eight lanes.Based on the data from the construction of the Changqing Bridge,this paper analyzes the key points of the potential construction risks through the Midas GTS finite element analysis combined with the method of construction monitoring.This paper also creates numerical simulation built on various working conditions by applying the construction deployment from the finite element software of laying the bridge foundation and arranging the high-level decks.Moreover,it has done the research of the effects that the new approaching construction of pile foundation has made on the nearby metros,tunnels and foundations of the old bridges.The main works and the result of the paper are as follows:(1)Analyze the influential range of the pile foundation construction on the approaching construction according to the practical working conditions of the Hunhe Changqing Bridge and the characteristics of the impact of different construction conditions on the interval tunnels and the existing old bridges;confirm the key points of the potential construction risks;carry out the theoretical research on the pile group effect of the bridge pile foundation and the deformation mechanism of the tunnel.(2)Formulate the monitoring plan for the subway tunnel and the old bridge pier through the analysis of the positional relationship between the pile foundation of the new bridge and the approaching project combined with the construction organization design and related engineering specifications;set a warning value according to the standard of deformation control;put most focus on monitoring the tunnel structure displacement at the risk source,tunnel headroom convergence,and displacement of the old bridge pier and abutment;compare the monitoring results of several months with the warning value of the control plan based on the IT-applicated construction to ensure safety of the construction in each process.(3)Establish a three-dimensional finite element model by using the Midas GTS software;create a numerical simulation built on the impact of the construction of the approaching pile foundations No.72 and No.75 on the excited metros,tunnels and the old bridges;compare the initial data of construction monitoring with the results of the numerical simulation at the early stage to verify the accuracy of the finite element model;then use the numerical simulation to anticipate the impact of the construction at the post stage so as to reach the goal of guaranteeing the quality of the project in advance.(4)Carry out simulation researches built on various working conditions according to different drilling sequences and different pile layout schemes;analyze the influence of the new pile foundation construction on the mechanical properties and deformation laws of the site soil,subway,tunnel and old bridge substructure;select the best drilling construction sequence and the optimal platform design scheme for the bridge foundation in the end.In this paper,the research of the effects that the new approaching construction of pile foundation has made on the nearby metros,tunnels and foundations of the old bridges will provide a reference for improving the multi-story construction of urban traffic engineering and ensuring the safety of the approaching construction in bridge and tunnel engineering especially.