Foundation Pit Supporting Design And Its Stability Study Of Changsha Metro Line 3 QiMao Avenue Station

Subway design and operation is an significant part of the rapid development of city construction, the importance and difficulty has been changed.The experts and scholars is not only puzzled by problems appeared in the operation of the subway, but also their enthusiasm for researching is stimulated. It is no exaggeration to say that construction of a station foundation pit is not only the result of the work of the contemporary people,but also the wisdom of the predecessors.Foundation pit engineering is a complicated engineering disciplines, and it is very important to study its relative laws. The paper study the project in Changsha subway No.3 line Qimao Avenue station foundation, analyzes change rules of retaining structure, the field measurement data is compared with the results calculated by the software and simulating results, the conclusions are as follows:1. Determine the relative parameters of the foundation design by the geotechnical investigation report and retaining structure design theory, employ the scheme of pile +inside support of foundation pit retaining structure,conduct design calculation for foundation pit by using F?SPW software, displacement and internal force diagram diagram in seven working conditions and the surface subsidence diagram of foundation pit is calculated. Check the relative stability parameter in foundation pit,results show that the surface subsidence and foundation pit stability coefficient meet the requirements of specification, foundation pit scheme is proved to be reasonable and the stability of foundation pit excavation is good.2. The monitoring scheme and field monitoring of foundation pit excavation is completed,and the horizontal displacement in the process of excavation retaining piles,steel support axial force, field monitoring data of the surface subsidence around the foundation pit is analysed,results indicate that the values change of monitoring data is very little,such as displacement of the retaining piles, the excavation of surface subsidence and so on.It not only meet the relevant specification requirements but also reflect the law.Monitoring data showed good stability of foundation pit.3. FLAC3 D simulation according to the filed condition of foundation pit excavation is carried on,and the change rule of displacement of foundation pit excavation and retaining piles,surface subsidence under various conditions is analysed.The displacement data of field monitoring and settlement data is comparied,consequence demonstrate that value of software simulation is larger than the monitoring value.It is because the software simulation can't fully reflect the complicated engineering situation,but both data can meet the specification requirements and guarantee the stability of foundation pit.