Study On Deformation Monitoring And Deformation Law Of Urban Metro Tunnel Construction

The subway deep foundation pit is a dangerous systems engineering,especially in the process of excavation it will cause the deformation of the surrounding environment,so it is necessary to carry out close deformation monitoring,study its deformation law,and provide accurate prediction and early warning information for safe construction,to ensure safe and smooth construction.In this paper,based on the actual deep foundation pit project of the offshore World Station of the Nanhai Avenue Branch Project of Shenzhen Rail Transit Line 9 Phase II,this paper introduces the significance of the research,the general situation of the project,the deformation monitoring scheme,the deformation mechanism of the deep foundation pit,the construction of the finite element software simulation,the deformation monitoring data of the construction site,the deformation monitoring data and the numerical simulation,the main conclusions are as follows:(1)According to a large number of measured data of nearly two years,such as the enclosure structure of the subway foundation pit,the bottom uplift of the foundation pit,the ground settlement around the foundation pit,and the settlement of buildings around the foundation pit,the law of the change amount and rate of each period is analyzed.Using finite element software Midas GTS/NX simulated respectively,and simulated the change tendency,then comparing the two,as the foundation pit construction,pipeline to move,the construction,the wall of foundation pit excavation depth increase will lead to deformation gradually increase,the foundation pit excavation is larger,the influence of excavation,the greater the deformation caused by,the measured data and finite element simulation of the numerical change trend of the present law.(2)The deformation monitoring data and variation curve of subway deep foundation pit show that the displacement variation of the foundation pit enclosure structure first increases and then decreases with the deepening of foundation pit excavation,and finally tends to be stable.The variation and variation rate meet the specification and design requirements.The variation of uplift at the bottom of the foundation pit increases gradually as the foundation pit excavation deepens,reaches the peak value,and decreases gradually after stabilization.The variation and rate of variation meet the requirements of the code and design.As the foundation pit excavation deepens,the surface settlement variation around the foundation pit first increases and then decreases,and finally tends to be stable.The settlement value has a great relationship with the location of the foundation pit,and the variation amount and rate meet the requirements of the code and design.In the process of excavation,according to the construction progress,increase the deformation monitoring frequency,closely track whether the change quantity and change rate are within the safe range,timely forecast and warning,when the change quantity and change rate tend to be stable,the monitoring period and number can be appropriately optimized.(3)The finite element software Midas GTS was used to establish a THREE-DIMENSIONAL model reflecting the excavation process of deep foundation pit,and the cloud map of the displacement change of the foundation pit enclosure structure,the change of the foundation pit bottom heave,and the change of the ground settlement around the foundation pit was constructed to study the change rules.Analysis results show that the finite element numerical simulation software and the actual monitoring data of the deformation law of consistency,to show that the deformation monitoring data is reliable,the finite element simulation to construct reasonable analysis data,for future similar engineering construction pit deformation value of prediction and early warning to provide accurate information,to guide the construction and optimization of deformation monitoring scheme has certain model function.