Monitoring And Numerical Analysis Of Deep Foundation Pit Of Yungu Road Station In Hefei Subway

Based on the deep foundation pit engineering of Yungu Road Station of Hefei Metro Line 5,this paper uses theoretical analysis and numerical simulation to simulate the whole process of foundation pit excavation,and compares the simulation results with the on-site monitoring data.The main research contents and conclusions are as follows:(1)Based on the example of the deep foundation pit project of Hefei Metro,the monitoring contents of the deep foundation pit,the layout and monitoring plan of the monitoring points were determined,the monitoring data of the deep foundation pits were sorted,and the deep foundation pit and support were analyzed.The deformation of the structure,the support axial force,the surrounding surface settlement and other changes.(2)The three-dimensional model of deep foundation pit is established by using finite element software MIDAS/GTS.The deformation law of the retaining structure,the bottom of the pit and the deformation of the ground settlement are analyzed.The results show that with the increase of the excavation depth of the foundation pit,The horizontal displacement of the retaining structure shows a trend of increasing first and then decreasing.When the foundation pit is excavated to the bottom,the horizontal displacement of the retaining structure reaches the maximum;the curve of surface settlement changes first and then decreases,and finally gradually In the form of"parabolic" which tends to be stable,when the foundation pit is excavated to the bottom,the surface settlement reaches the maximum;the law of the change of the amount of the bottom of the pit shows the trend of "large in the middle and small in the ends",when the foundation pit is excavated to the bottom.The amount of bulge at the bottom of the pit reaches a maximum near the center of the bottom of the pit.(3)Using numerical simulation,the finite element model which does not consider the foundation pit dewatering and considering the foundation pit dewatering is further analyzed.Under the condition of foundation pit dewatering,the horizontal displacement of the foundation pit retaining structure and the surrounding surface settlement value are overall.Too big.The actual process of foundation pit excavation is a complex process of seepage field and stress field.The analysis of groundwater excavation is a single stress analysis.It is unsafe to analyze the excavation deformation of foundation pit.Moreover,the increase of the stiffness of the steel support itself and the decrease of the steel support spacing are studied,and the normal use stability of the foundation pit is increasing.However,when the steel support is dense and the rigidity reaches a certain level,the deformation of the foundation pit hardly changes.Therefore,under the premise of satisfying the stability of the foundation pit,the excavation and support design of the foundation pit should select a suitable steel support.(4)On-site monitoring of the deep foundation pit of the metro station is mainly carried out from three aspects:the deep horizontal displacement of the retaining structure,the supporting axial force and the surface settlement around the foundation pit.The monitoring data meets the specifications and design requirements,indicating that the design of the enclosure structure of the project is reasonable and effective.The numerical simulation results are in good agreement with the measured results,indicating that the calculation model used is reasonable.The numerical simulation results can provide reference for the design of the surrounding excavation structure and the foundation pit monitoring scheme.