| In recent years,with the development of the urban economy and the expansion of the scale,the rapid development of urban rail transit,the construction difficulty of deep foundation pits of subway stations is also increasing.Safety accidents caused by the instability of deep foundation pits due to improper design or construction have occurred from time to time.Based on the research background of the deep foundation pit engineering of Hongtang Road Station of the "L" type transfer station of Line 4 and Line 5 of Fuzhou Metro,this paper studies the stress in the construction process of deep foundation pit engineering of Hongtang Road Station through numerical simulation and field monitoring deformation law,analyze its stability in the construction process.The main research content and results are as follows(1)The MIDAS GTS software was used to conduct a three-dimensional finite element simulation of the excavation process of deep foundation pits,and the changes of the horizontal displacement of the ground connection wall,the ground settlement around the foundation pit and the internal forces of the supporting structure during the excavation were analyzed;according to the construction plan of the foundation pit,on-site monitoring was conducted on the displacement of the underground continuous wall,the axial force of the concrete and steel structure support structure,the ground settlement,and the groundwater level;the numerical analysis results are verified by on-site monitoring data.(2)The numerical simulation results show that the excavation of foundation pits at the same time reserves soil at the outside of the blocking wall of the transfer node to provide lateral pressure,which has a certain inhibitory effect on the deformation of the retaining structure of the transfer pit and ground settlement;under the design conditions,the deformation of the supporting structure and the surrounding surface settlement of the foundation pit during the entire excavation process did not exceed the allowable design value,and the overall stability was good.(3)The top of the ground connection wall of the foundation pit is limited by the crown beam and the first support.At the bottom,due to the vertical embedding of the wall,the displacement is small.The maximum deformation occurs in the middle of the ground connection wall,and the horizontal deformation curve is arched.As the soil inside the foundation pit is excavated and unloaded,the envelope structure is affected by the pressure difference between the inside and outside of the foundation pit,and the horizontal displacement gradually increases.The position of the maximum displacement moves downward with the soil excavation.The soil settlement curve around the foundation pit generally shows a "groove shape".In the range of 5-15m from the edge of the foundation pit,the surface settlement is large.(4)With the gradual excavation of the foundation pits,the axial forces of the supports in the foundation pits show a trend of increasing to varying degrees.The maximum supporting axial force at the transfer node is at the third and fourth supporting positions,and the maximum supporting axial force at the foundation pit of Line 5 is at the third supporting position.The supporting force in the foundation pit is mainly concentrated in the middle and lower part of the foundation pit.The erection and removal of the lower support have a certain impact on the stress of the upper support structure,and the monitoring of adjacent supports should be strengthened.Figure 72 table 9 reference 59... |
