Study On The Influence Of Asymmetric Excavation On The Structure Of The Existing Station By Kuiqi Road Station Of Foshan Metro Line 2

In the planning stage of urban rail transit network,there are fewer factors to consider the feasibility of the project,which is relatively rough.In order to avoid the waste of the project caused by the later adjustment of the network,Metro transfer stations often choose to construct by stages.The interruption of subway operation has a great impact on society.Therefore,in the later construction process,how to ensure the operation safety of existing subway stations has become an important issue that needs to be solved in design and construction.Based on the Kuiqi Road Station of Line 2 of Foshan Metro,this paper collects and sorts out related survey and design data,and through finite element numerical simulation calculation analysis,the existing pits on both sides of Kuiqi Road Station under different excavation conditions are studied.The deformation law of the station structure.combined with on-site monitoring data to analyze the rationality of the selection of stratum parameters,sum up experience and put forward protective measures to ensure the safety of foundation pits and existing structures,to provide reference for subsequent similar projects.the main conclusions are as follows:1,Through numerical analysis,the deformation law of subway station structure in the process of foundation pit excavation is found out,the main factors affecting the structural deformation are found,and the reasonable excavation scheme is selected to ensure the safety of subway structure and operation.2.When the asymmetric range of foundation pit on both sides is less than I times of the structural width,the shear deformation is the main deformation of the station structure under the condition of symmetrical excavation,and the deform,ation can be almost ignored.The South-North width of the east side foundation pit is 73.8m(asymmetric width is 17.6m,the width of the existing structure is 21.0m),and the South-North width of the west side foundation pit is 56.2m.Although the width of the west side foundation pit increases nearly 30%compared with the east side,the horizontal deformation of the existing station structure to the west side is only 0.16mm.3.Under the condition of unsymmetrical excavation of the foundation pit on both sides of the existing station,the geological difference on both sides of the existing station has a great influence on the structure of the existing station.The compression modulus(3.5Mpa)of muddy soil on the east side is 25%of that of strongly weathered mudstone on the west side.The horizontal deformation(3.5mm)of the station structure on the east side can be reduced by about 20%compared with that on the west side(4.2mm).4.Under the condition of asymmetric excavation,the axial force of the support changes greatly.Under different construction conditions,the axial force of the support can be changed from compression to tension,especially when the shape of the foundation pit is irregular,which is more likely to occur.Therefore,the safety of the foundation pit construction can be greatly improved by using the concrete support for the irregular foundation pit with large geological difference.5.Under the condition of symmetrical excavation,the ground settlement value can be reduced by about 20%without considering the space-time effect.Therefore,symmetrical excavation of foundation pit is more beneficial to protect the surrounding buildings.