Numerical Simulation And Optimization Design Of Foundation Pit Support For A Subway Station In Wuhan

In recent years,due to the needs of Wuhan subway construction,the utilization rate of underground space is growing rapidly.The subway station is basically located in the prosperous area of urban construction.There are many restrictions,the surrounding environment is complex,and engineering accidents occur,causing economic losses and adverse social impacts.The design and construction of the deep foundation pit support of the subway station will affect the safety of the foundation pit.The construction of the subway station is in an extremely important position in the subway project.Therefore,studying the excavation process of the foundation pit of the metro station has important theoretical and practical significance for the design and construction of the foundation pit retaining structure and surrounding soil deformation.Based on the deep foundation pit engineering of a station in Wuhan Metro,the deformation of the foundation pit during the excavation process is studied through the combination of theoretical deformation analysis,actual monitoring data analysis and numerical simulation analysis.At the same time,the influence of the structural parameters of the internal support system on the excavation deformation of the foundation pit is analyzed by numerical analysis and theoretical verification,and the design parameters of the original supporting structure are optimized.The main research contents and conclusions are as follows:?1?To analyze and analyze the main supporting forms of subway foundation pit engineering in Wuhan area,to discuss the law of deformation characteristics,summarize the theoretical calculation formula,and summarize the factors affecting deformation.?2?Using the Qimstar deep foundation pit calculation software to theoretically calculate the project,obtain the envelope structure and the surrounding surface deformation curve,and compare with the actual monitoring deformation curve.It is concluded that the theoretically calculated deformation value is smaller than the actual monitoring value,and the enveloping structure and the surrounding surface deformation curve characteristics are basically the same.The deformation of the retaining structure presents a bow-shaped trend with two small middle and large,and the position of the maximum displacement gradually decreases with the excavation;the influence of the surface settlement around the foundation pit is about 1 times the depth of the excavation,and the deformation curve shows a concave parabola.?3?Using Midas GTS NX to carry out numerical analysis of foundation excavation of the project,firstly analyze and study the selection of constitutive model,and select the small strain constitutive model of hardened soil.Then,the grid is mixed and meshed,and the number of units is 205,843.The stress analysis is carried out according to the construction conditions of the foundation pit excavation.Comparing the simulation results with the actual monitoring results,it is concluded that the maximum settlement of the surrounding surface occurs at 8¹5m from the edge of the pit,and the deformation influence range is within the range of 1 to 1.2 times of the excavation depth of the foundation pit;the horizontal displacement curve of the wall is basically in the shape of a bow.?4?Using 36 different combinations,the value of the empirical coefficient of the stiffness parameter of the constitutive model is analyzed and studied.Determining the empirical coefficient relationship of soil stiffness parameters in the small strain model of hardened soil in Wuhan area,drawn for use in cohesive soilE_oed^ref=E_s^1-2?E_50f^ref=2E_oed^ref?E_ur^ref=6E₅₀^ref?G₀^ref=2E_ur^ref?for sandy soilE_oed^ref=E_s^1-2?E?50f?^ref=E_oed^ref?E_ur^ref=5E₅₀^ref?G₀^ref=2E_ur^ref?5?Using finite element analysis to analyze the influence of structural parameters of internal support system on the deformation of foundation pit in the foundation pit support engineering of a station in Wuhan Metro,and optimize the internal support system from two angles of vertical spacing and horizontal spacing,get an optimization plan.The horizontal spacing of concrete supports was changed to 8m,and the horizontal spacing of steel supports was changed to 4m.This project reduces the internal support cost of 5.5 million yuan on the basis of ensuring the safety and feasibility of the foundation pit.