Comparative Analysis Of Excavation And Excavation Method And Cover Excavation Reverse Method Of Deep Foundation Pit Of A Metro Station In Hefei City

After the reform and opening up,China's urbanization level has been continuously improved.With the rapid increase of urban population,the pressure of urban ground transportation is increasing.Building a subway has become the only choice to ease the pressure of ground transportation.The first thing that needs to be solved when constructing the subway line is the excavation of the foundation pit.The cover excavation method is widely used in the subway construction projects of major cities because it can restore the ground traffic as soon as possible,but various excavations due to foundation pits The accidents are still endless.Therefore,It is essential to select a scientific and reasonable construction method in the foundation pit excavation project to reduce the occurrence of accidents and reduce the impact on the surrounding environment,However,the selection of construction methods for excavation of foundation pits should be analyzed according to specific objects.Considering the cost of construction,the construction period,and the impact on the surrounding environment.Taking the foundation pit project constructed by a cover excavation method in a subway in Hefei as an example,the author used MIDAS/GTS NX finite element numerical analysis software to carry out numerical simulation of the excavation method and the reverse method respectively.The field measured data demonstrates the accuracy of the numerical model of the smoothing method,and then the two methods are summarized and summarized for the settlement,horizontal displacement and horizontal displacement of the retaining pile around the foundation pi,and two methods are carried out.Horizontal comparison provides reference for the selection of similar foundation pit construction methods in the future.The main research contents are as follows:Firstly,the related theoretical research results of the foundation pit engineering and the engineering background of the foundation pit engineering are introduced.Then the MIDAS/GTS NX finite element numerical analysis software and the two model establishment processes used in this paper are described in detail.Under the two construction methods,the horizontal displacement of the soil surrounding the foundation pit,the settlement and the horizontal displacement of the retaining pile are summarized and compared horizontally.The research results are as follows: under thecover-excavation method,the top plate and the top plate which have been completed before the excavation of the soil have a great supporting effect on the foundation pit,which largely prevents the displacement of the surrounding soil and the supporting pile.Under the cover digging method,although the construction difficulty is small and the construction period is short,it can meet the specification requirements.However,the supporting effect of the lateral support on the foundation pit is not as great as that of the top plate and the bottom plate in the reverse method,and the displacement amount is larger;In the foundation pit excavation method,the excavation unloading of the soil in the foundation pit is the most important cause of the settlement and horizontal displacement of the surrounding soil.In summary,the cover digging method and the reverse method have their own characteristics,and the specific project should be analyzed to select the appropriate foundation pit excavation method.