Research On Influence Of Deep Foundation Pit Excavation On Adjacent Bridge Pile Foundation In Subway Station

This paper takes the subway station of as the project background,and the thesis is studied in three aspects:theoretical analysis,numerical simulation and field monitoring.The main work is as follows:(1)On the basis of the original theory,the mechanism of stratum deformation caused by deep foundation pit excavation is analyzed,and the main factors affecting the deformation of foundation pit are summarized.The research shows that the excavation itself is a unloading process.In the process of excavation,the load decreases continuously,resulting in the rebound of the bottom of the pit.The soil on both sides of the foundation pit moves to the foundation pit under the effect of pressure difference and causes the formation deformation.There are many factors affecting the deformation of the foundation pit,including the inherent factors of engineering geology,hydrogeology,the design factors of the form of the foundation pit supporting structure and the stiffness of the supporting structure,and the construction factors,such as the construction method and the construction period.(2)Based on the reverse analysis principle,the nonlinear mapping relation between the horizontal displacement of the diaphragm wall and the elastic modulus of each soil layer is established,and the two function without cross term is used as the inversion function of the elastic modulus of each soil layer,and the elastic modulus of each soil layer is retrieved in two steps.The first step is to use the 11 parameters of the multiple response surface function as the variable target,and simulate the horizontal displacement of the diaphragm wall with flac3d software,and reproduce the parameters values.In the second step,the elastic modulus of each soil layer is variable.Based on the least square method,the nonlinear grg method is used to derive the elastic modulus of each soil layer.(3)The numerical simulation of the elastic modulus obtained by the inversion is used to analyze the displacement characteristics of the diaphragm wall and the bridge pile with different working conditions,different iterations and different distances.The results show that the simulated curve of the second inverse analysis is better to simulate the shape of the curve,including the peak value,the position and the turning point.With the increase of the number of iterations,the accuracy of the simulation is improved continuously,and the precision requirement has been satisfied to the third iteration.(4)Using flac3d software to compare and analyze the difference between sleeve valve pipe pre reinforcement and pre reinforcement measures.The study shows that the horizontal displacement of the bridge pile can be effectively reduced by the pre reinforcement grouting.The horizontal displacement curve of the bridge pile is reduced to zero at about 15m due to the pre grouting reinforcement.