Micro-disturbance Control And Monitoring Visualization Of Subway Tunnel Influenced By Foundation Pit Excavation

As an important form of public transportation in large and medium-sized cities,rail transit is becoming increasingly popular,and the safety of subway tunnel structure is the basic premise for ensuring the normal operation of rail transit.On the one hand,the foundation pit project next to the subway tunnel needs to be optimized in the design stage to determine the excavation plan with relatively small impact on the adjacent tunnel.On the other hand,due to the complexity of the response of the shield tunnel structure,the actual response of the adjacent tunnel needs to be fully presented in conjunction with a refined on-site monitoring and data presentation platform.Therefore,decision makers can easily find problems and provide more effective support for solutions.This thesis focuses on the two things,the small disturbance and it’s control measures of the adjacent shield tunnel caused by the excavation of the foundation pit and the visualization of the shield tunnel monitoring data.The main research contents are as follows:1.The deformation mechanism and deformation characteristics of the immediate environment under the influence of deep foundation pit construction are systematically described.And the microdisturbance control measures,specific methods and related characteristics of the deep foundation pit immediately adjacent to the construction link are analyzed.2.Based on a large-scale foundation pit group project in Shanghai Xuhui Center,PLAXIS3 D software is used to conduct simulation analysis on the response state of the adjacent tunnel under the influence of foundation pit group excavation from the aspects of optimizing the excavation method and improving the deformation resistance of the enclosure system.This can be taken as a experience reference of qualitative and quantitative evaluation for similar actual project in the future.Studies have shown that in similar projects,the disturbance deformation of the adjacent tunnel caused by pit excavation can be effectively controlled or mitigated by measures such as reasonable arrangement of excavation sequence of foundation pit group,single pit excavation and immediate underground structure construction before next pit excavation,improve the rigidity of the enclosure system and the thickness of the underground continuous wall.3.Based on the BIM software REVIT and DYNAMO visual programming plug-in,a threedimensional visualization system of shield tunnel based on distributed monitoring data set was developed.The visualization system organically integrates the parametric modeling of the tunnel structure and the visualization of the monitoring data.The research contents include: 1)The visualization of the real position and posture change of shield tunnel segments driven by monitoring data,2)Visualization of planar distributed monitoring data,and 3)Visualization of linear distributed monitoring data.Based a the subway shield tunnel adjacent to the excavated foundation pit of Nanjing Metro Line2 as an example,combined with the distributed data collected by the optical fiber monitoring system,a comprehensive visualization model of the tunnel in the monitored section was established,and the three-dimensional visualization of the monitoring data of the tunnel in the monitoring section was realized.By comparing with the traditional two-dimensional chart presentation method,it shows the effectiveness and superiority of the visualization system.