Excavation Monitoring And FLAC3D Simulation Analysis Of A Railway Station In Lanzhou

With the rapid development of the country,every province and city is vigorously developing the construction of subway projects,and the theory and technology involved in the subway deep foundation pit engineering are very complex,there are a wide range of disciplines,and the geological conditions at the construction site are often very complex.Because the periphery of the foundation pit is often located in the center of the downtown area,once the safety accident occurs in the foundation pit,it will often cause adverse social impact and significant economic losses.Therefore,it is necessary to monitor the whole process of foundation pit excavation in order to avoid the accident of foundation pit.Based on the monitoring data obtained from the foundation pit monitoring project of Lanzhou West Station North Square Station Phase I project of Lanzhou Rail Transit Line 1 Phase 1,this paper analyzes the monitoring data collected from the site excavation,and draws the curves graph of each data to reflect the deformation law of the pile displacement,the axial force of steel support and the ground settlement in the horizontal direction of the foundation pit.It has accumulated certain experience for other subway projects in the region to be constructed by the unit by studying the deformation method of the station.The finite difference method software FLAC3 D 6.0 is used to establish a three-dimensional model through the existing foundation pit size,geological conditions,maintenance structure,etc,and simulate the deformation of the foundation pit during the actual working conditions in the excavation phase,and the simulation results and the measured results are carried out Through comparative analysis.Finally,discusses the influence of the internal support system on the deformation of the foundation pit in the process offoundation pit excavation.the conclusions of this paper are as follows:(1)Through the analysis of the monitoring data,the surface settlement deformation around the foundation pit presents a "groove" distribution;the displacement curve of the pile shows the shape of the largest and then the smallest with the increase of the depth,and the overall shows the "bow" deformation curve;The axial force of steel support fluctuates up and down within the range of 800 k N~1200k N;The foundation pit of the North Square Station of Lanzhou West Railway Station is in a controllable state by analyzing the monitoring results of each monitoring project.The surface subsidence the horizontal displacement of retaining pile and accumulated deformation value of supporting axial force are all within the control value,which proves that the design of supporting system is safe and reliable,and the monitoring scheme is arranged reasonably and effectively.(2)The data obtained are basically similar to the actual deformation situation of the monitoring position compared in this paper through numerical analyses of the FLAC3 D.It shows that the selection of simulation parameters is reasonable and reliable.It can be concluded that the simulation has a certain reference and significance for the excavation of foundation pit in the construction site.(3)Based on the verification that FLAC3 D software can simulate the foundation pit deformation intuitively and accurately,the influence of different forms of internal support system on the foundation pit deformation is analyzed after modifying the parameter modeling again.It is concluded that the use of internal bracing with large stiffness,reducing the spacing between internal bracing and increasing the number of internal bracing will play an important role in restraining the deformation of foundation pit and ensuring the safety of foundation pit excavation.