Study On Settlement Deformation Analysis And Protection Technology Of Metro Shield Tunneling Through Existing Structures

As social economy constantly evolves,more and more cities are building subways to ease traffic pressure.Shield construction has been widely used in urban subway construction,digitization,mechanization,and less impact on ground transportation.It will inevitably have a certain impact on existing structures when we use shield method for subway construction.Therefore,how to predict the trend of settlement and deformation in advance and take targeted protective measures in time have become an urgently key technical issues for subway shield construction.Therefore,on the basis of risk identification,this paper used means such as adopts numerical simulation and on-site settlement monitoring.Through settlement deformation analysis to put forward the protective technical measures of subway shield tunneling under the existing structures.At the same time,some conclusions useful for engineering application were obtained.Based on the shield construction in the interval between Datieguan Station and Baoshanqiao Station of Hangzhou Metro Line 5,this paper has determined the high risk source of the interval shield construction when crossing through the reference documents and related metro construction specifications.It used MIDAS/GTS and PLAXIS FEM to simulate the construction process of shield tunneling through existing structures,and focused on the analysis of influence rules on existing structures during the crossing process.Its also deployed a monitoring network for risk sources.Through the comparison of finite element simulation results and measured data to make a comprehensive analysis for settlement rules during shield construction,to put forward the protective technical measures for the risk source in the shield construction proces.It used the monitoring network data,protective technical measures and existing construction experience to continuously adjust the parameters of the shield construction.The goal is to minimize the impact of existing structures and to provide a certain reference for the construction in the future.The main researchunderstanding is as follows:(1)When determining the risk source,this paper mainly investigates the influence of the Engineering survey of the existing structures on the construction safety and stability,according to the factors such as the construction age of each building,the distance from the foundation pit,the foundation form,etc.,the safety assessment of the structure identified the first-level risk sources around the north road tunnel,the construction of the North Bridge,the Grand Canal According to the different risk source structures,three-dimensional and two-dimensional models of the project risk source were established by using finite element MIDAS/GTS and PLAXIS software.And it calculated and analyzed the maximum settlement of the shield through the existing structures.Shield crossing construction will affect the normal use of existing structures.The settlement reaches the maximum value when the shield construction crosses the existing structures.According to the study,it can be concluded that the ground parameters and construction disturbances during shield construction are the most influential factors for crossing.Failure to take protective technical measures may affect the safety and normal use of existing structures.(2)Based on the results of numerical simulation,the monitoring network was deployed for risk sources.After analyzed the monitoring data of several special points in the test section,The results showed that the settlement deformation will increase when the shield construction excavation surface approaches the monitoring point under actual conditions.The monitoring data at special points in the test section were compared with the numerical simulation.The deformation trend was roughly the same,and the actual monitoring value had a tendency to increase.which verified the reliability of the finite element model prediction and the rationality of the parameters.Using the monitoring data of the monitoring network will make up for the lack of numerical simulation theoretical analysis.Finally,by contrasting the data,it will promote the shield construction to pass through existing structures.(3)Under the theoretical guidance of FEM simulation results and actual monitoring data,the paper combined with relevant literature,rules and actual construction experience.In order to make the settlement of the shield construction within the control value and without affecting the safety performance and normal use of existing structures.It is concluded that the main technical measures for shield construction protection.At the same time,the effectiveness of protective measures is verified by real-time monitoring of the settlement of shield tunneling through existingstructures using a well-arranged monitoring network.