Finite Element Simulation Analysis Of An Underground Space Structure Across A Subway Tunnel

In recent years,with the vigorous development of urban underground space,a large number of underground space constructions have been inevitably occurring across subway tunnels.The construction of these underground spaces can easily cause disturbances to the surrounding strata of soil and create the existing subway tunnels influences.In order to ensure the normal operation of the subway,the strict control of the construction process on the stress and strain increments of subway tunnels has become the focus of underground space development across metro tunnels.Therefore,it is necessary to study the mechanism of the surrounding soil in the construction process of the underground structure,and to obtain the changes in the stress and strain of the tunnel and the surrounding rock under this influence.Based on the underground space structure project of a subway tunnel in Guangzhou,this paper analyzes the influence of various construction conditions on the existing subway tunnel during the construction of the underground structure,and draws the conclusion that the perimeter of the foundation pit,the tunnel lining and the surrounding rock around the tunnel are Stress and strain laws in various operating conditions.Finally,analyze the dynamic load of the subways that have been operated in this project and discuss the impact of the dynamic load on the new underground structures.The main work and conclusions drawn from this study are as follows:(1)The finite element software of geotechnical engineering is used to give relevant basic assumptions to the research object.Assuming stratified horizontal stratigraphic distribution,linear elastic constitutive model for structural materials and Mohr-Coulomb model for soil,a spatial finite element model is established.Analyze the stress and strain laws of the surface,surrounding rock and tunnel lining.(2)Discuss the self-safety of the foundation pit in the process of open excavation,including the surrounding ground surface settlement and the horizontal displacement of the supporting structure under various construction conditions.It is concluded that the settlement of the ground surface outside the foundation pit is concave and the maintenance structure displacement increases mainly in the six working conditions before excavation of the foundation pit.The results showed that surrounding rock was distributed in layers during the construction process,and the normal stress increased from top to bottom,while the shear stress was relatively small,and the impact was negligible.(3)Analyze the influence of the construction process on the stress,strain and displacement of the tunnel lining,and the change rule of stress and strain of the tunnel lining under various working conditions.It is concluded that the vertical displacement is mainly concentrated on the top of the arch,and the horizontal displacement is mainly concentrated on the left and right arched parts.Displacement changes dynamically with the progress of the construction.During the first six excavation stages,the displacement continues to increase.During the construction of the main structure,the displacement rebounds;the maximum axial,radial,and hoop stress values appear in the vaults.In the position,the stress is in a strip distribution,and the arch is used as the boundary.The axial and radial stress values above the arch waist are generally larger than those below the arch waist.(4)The dynamic time history method was used to analyze the influence of train load on the initial ground stress state,the first excavation,the sixth excavation,and the backfilling of the earth filling.The maximum train load caused the displacement around the tunnel.The maximum value is small,the impact on the new structure is smaller and can be ignored.