A Study On The Monitoring And Numerical Simulation For Foundation Pit Excavating Engineering Of Subway Station

Based on the foundation pit engineering of guangxi university station of Nanning city rail transit line 1 , the deformation of underground continuous wall and the change rules of strut axial forces were analyzed and studied by the combined method of theoretical research, in-situ monitoring and numerical simulation, The main contents and conclusions are :(1)Discusses the research status of the deep foundation pit engineering and its executing monitoring, analyzes the deformation mechanism and influencing factors of its stability of deep foundation pit. And points out the specific problems still exist in metro station in deep foundation pit for survey, design, construction and monitoring.(2)According to the engineering practice of deep foundation pit, the site monitoring plan is given. Through analysis of the site monitoring data, the ragulation of the deformation of underground continuous wall,strut axial forces, etc in the construction process were summed up, and the results showed that the range of the wall deformation and steel strut axial forces were safe, but the reinforced concrete strut axial forces were beyond the design value. The following conclusion were yielded by careful analysis: due to the influence of the shrinkage and creep existing in concrete, the monioring results of reinforced concrete strut axial forces are often too big .(3)Usingthe finite element analysis software "MIDAS" / GTS ,the excavation process on the middle place of the metro station were analyzed by numerical simulation.Compared the calculated results with the measured, showing that the deformation of continuous wall in each construction stage matched well , the correctness of the simulation were proved. By comparing the strut axial forces with the measured ,result were obtained: no difference in steel strut axial forces, but the measured axial forces of reinforced concrete strut were still far above the simulation value, than the reason why the monitoring value is too big for reinforced concrete strut axial forces is analyse. Moreover through adjusting the vertical position of steel struct by simulation, it's safer before the adjusting in steel struct position (4)Through the simulation on the shield well part of the foundation pit in axial force and displacement , the different deformation distribution from the main part and the change rule of strut axial forces in the three rows were analyzed, and provide a reference for the similar projects in the future.