Analysis On The Effect Of Excavation Of Deep Foundation Pit And The Stiffness Of Retaining Structure

With the rapid development of our country’s economy,hefei has achieved unprecedented development results in recent years,and its urban scale has been constantly expanding.In this context,in order to ease the traffic congestion,hefei rail transit construction is in full swing.In the construction process of the subway station,the deep foundation pit of the subway station is the guarantee of the main project of the station.Only by doing well the foundation pit support,controlling the foundation pit deformation and understanding the foundation pit deformation law in hefei area can the construction of the main project of the subway station be carried out smoothly.Compared with other regions,hefei has its unique characteristics due to its complex geological environment.With the construction of hefei subway,it is necessary to study the deep foundation pit of the subway station in hefei.In hefei city rail transit line 4 tongcheng road station deep foundation pit as the background,combined with previous scholars research results and the measured data,starting from the theory of the engineering compared with finite element software MIDAS GTS NX numerical simulation analysis,are studied in the construction process of excavation and support system in the overall deformation trend and their force,and explore the palisade structure stiffness on the influence law of deep foundation pit deformation at the station.The study in this paper can provide valuable references for the following subway station projects in hefei region.The main work and conclusions of this paper are as follows:1.The research results of deep foundation pit engineering at home and abroad are introduced,the mechanism of soil deformation and the influencing factors of foundation pit deformation are analyzed,and the calculation method of retaining structure and the concept of formation loss method are summarized.The monitoring data are collated and the measured results of foundation pit deformation are analyzed to obtain the regularity of foundation pit deformation.2.The comparison between the simulated data and the monitoring data shows that the simulation results are close to the monitoring results.Although there is a deviation between the two numerical values,the foundation pit deformation law is consistent,indicating that the numerical simulation results are reliable.3.The deformation of the surrounding wall of deep foundation pit will develop with the development of foundation pit excavation,which presents the law of bulge out into the pit and the maximum displacement downward;After the completion of the excavation of the southern end head well and the adjacent section,the maximum horizontal displacement of the protective wall of the southern end head well is between 0.5 and 0.7times of the excavation depth.4.Both monitoring data and numerical simulation results show that the surface subsidence curve increases and then decreases with the deepening of foundation pit excavation.The location of the maximum subsidence is not the foundation pit edge,but a certain distance from the foundation pit edge,which should be paid attention to in the foundation pit construction process.5.The stiffness and deformation of deep foundation pit retaining structure between the inverse relationship,improve beneficial to control the deformation of deep foundation pit retaining structure stiffness but cannot rely on constantly increasing enclosure wall stiffness(pile)to enhance the ability of resistance to deformation of foundation pit,because the results show that foundation pit deformation under 2 EI is not compared to the original stiffness EI will reduce a lot.