Research On Reliability Of Foundation Pit Support Structure System Of Metro Station Based On Construction Steps

In recent years,with the rapid development of urbanization,the rapid increase of urban population,causing a series of problems such as urban traffic congestion,urban subway has been widely concerned because of its high efficiency and convenience.The metro construction of major and medium-sized cities in China has entered a period of rapid development.The Shenyang Metro Line 1 and Line 2 have been opened in Shenyang,and several lines are under construction.Foundation pit engineering is the key step of Metro construction.It is necessary to set up enclosure structure to ensure the stability of foundation pit during the construction of foundation pit.Whether the setting of the retaining structure actually plays a role in the stability of the foundation pit is worth discussing.Therefore,it is of great significance to carry out the reliability study of the construction steps of the foundation pit retaining structure system of the metro station.Based on the foundation pit engineering of the Olympic Sports Center Station of Metro Line 9,which is adjacent to the existing Metro Line 2 in Shenyang,this paper studies the stability and reliability of the foundation pit support structure with different construction steps through theoretical analysis.On this basis,the influence of the whole construction process of deep foundation pit on adjacent metro tunnels is measured and studied,and the influence mechanism of foundation pit excavation on the deformation of metro tunnels is analyzed.The research contents are as follows:(1)Based on the principle of structural reliability,the relationship and difference between the above-ground structure and the underground structure are analyzed,which mainly includes three aspects:load type,resistance type and structural system.(2)According to the actual situation of the project,the second-order moment method is used to study the anti-overturning and foundation pile uplift reliability of the foundation pit engineering.The results show that the foundation pit row support scheme based on single-support system is reliable.The degree coefficient is low,the additional constraint is added to increase the steel support;the anti-lifting reliability of the foundation pit meets the requirements,and the reliability of the project is not determined by the foundation pit bulge,so the foundation pit bottom is not reinforced.(3)The function function of the reliability analysis of the construction step of the foundation pit support structure is established,and the reliability of the mechanical performance of retaining piles in each supporting construction process is analyzed by JC method.(4)Deformation of foundation pit is analyzed based on field monitoring data.The monitoring results show that the maximum horizontal displacement of the supporting structure is located at the two corners of the foundation pit,and with the construction of the foundation pit,the displacement of each monitoring point is increasing.