| At this stage,the rapid development of urbanization in my country,the contradiction between the growing population and the scarcity of ground space has prompted people to point the finger at the development of underground space.The development of underground rail transportation has greatly solved the congestion of urban ground transportation.In recent years,various parts of my country have actively developed urban underground rail transportation,and the subway line network has become more and more dense.As of 2021,33 cities in my country have established 4600km subway transportation network.Subway lines generally run through the prosperous urban areas,covering a wide range,and there are many surrounding buildings,so there are not a few foundation pit projects adjacent to the subway tunnel construction.The unloading effect of foundation pit excavation must have a certain impact on the adjacent existing subway tunnels,and the subway in operation is very sensitive to the small deformation of the tunnel.With the development of foundation pit engineering,the excavation depth continues to increase.The impact of subway tunnels has also increased,and it may even lead to the destruction of the tunnel structure.Therefore,it is of practical engineering significance to study the tunnel deformation mechanism and the influence of foundation pit excavation on existing tunnels.This article mainly conducts the following research:(1)Comprehensively sorted out the foundation pit deformation theory and the influence mechanism of side excavation on the existing tunnel deformation,and summarized the influence factors of side excavation on the tunnel deformation,and sorted out the relevant specifications on the foundation pit deformation and tunnel deformation The control standard value.(2)Based on the theory of foundation pit deformation,numerical simulation was carried out based on the foundation pit project of a subway station in Hefei,and the elastic modulus that can reflect the soil stress path in Hefei was used to carry out two-dimensional modeling calculation,and the foundation pit excavation was studied.The deformation law and force characteristics of the foundation pit,the influence law of the lagging erection of the steel support for the deformation of the foundation pit is further discussed,and the sensitivity analysis of each influencing factor of the foundation pit deformation is made.(3)A three-dimensional numerical modeling calculation was carried out for an existing tunnel foundation pit project adjacent to the side of Guangzhou.The tunnel is a double-span rectangular frame structure.By changing the finite element model,the impact of horizontal clearance between the excavation pit and the tunnel and the relative buried depth of the tunnel on the deformation of the tunnel is studied and analyzed.At the present stage,most of the studies on the excavation of foundation pits on adjacent existing tunnels take shield tunnels as the research object,while the lack of other structural forms of subway tunnels is affected by foundation pit excavation,and the influence of foundation pits on the deformation of rectangular tunnels is studied.The law can provide a reference for similar projects in the future and effectively avoid the occurrence rate of engineering accidents.(4)On palisade structure rigidity and two built-in depth of retaining structures of side both the deformation of the tunnel control effect is analyzed from the level of the tunnel deformation and vertical deformation of tunnel adjacent foundation pit deformation analysis of two control degree,draw the conclusion:increase the palisade structure stiffness can reduce the deformation of tunnel,and horizontal deformation of the tunnel control effect is better than that of vertical deformation;Increasing the embedding depth of envelope structure can reduce tunnel deformation to a certain extent,but the reduction is not large.Figure[75]Table[16]Reference[76]... |
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