Monitoring And Numerical Simulation Study Of A Metro Section Cut-and-Cover’ Deformation

Study of deep foundation pit deformation is one of the important subjects in the construction of the metro station, and it is an important part of information construction. There are two ways to study metro foundation pit deformation:first, the monitoring data obtained by metro foundation pit deformation monitoring analyze the characteristics of deformation of the foundation pit; Second, through the numerical simulation methods to analyze the deformation characteristics of foundation pit under various working condition of excavation. Both mutual authentication and realizing information construction. There are too much items and monitoring number in metro foundation pit deformation monitoring. Managing and analyzing of data is very tedious and error-prone. Develop a data management system that suitable for metro foundation pit deformation monitoring is of great value for improving the efficiency of monitoring. On the basis of consulting a large number of literature, the main studies is as following:(1) Designing a deformation field monitoring scheme, determine the accuracy, frequency, data analysis and report production of monitoring. Designing the arrange regular of monitoring sites, the way of observation and data calculation for the earth’s surface and stake Sedimentation, stake displacement, support axial force, underground water level, foundation pit convergence and the displacement of the continuous wall.(2) Analyzing the basic requirements, technical and economic feasibility of subway foundation pit deformation monitoring data management system. Based on SQL Server database, under Visual C++ environment, combining with Microsoft Word and Excel software, developing the subway foundation pit deformation monitoring data management system. The system realized the following functions:import and export monitoring raw data in an integrated way; generate the total variation, variation and change rate of the monitoring data; generate monitoring daily report, weekly report and monthly report; check the history monitoring data according to user needs; generate time-deformation curve of all monitoring pots and continuous wall sloping curve; search for emergency and alarm pots of all monitoring pots.(3) Using finite difference software FLAC-3D, simulating excavation and supporting process of a metro section cut-and-cover, study the deformation characteristics of deep foundation pit. Analyzing horizontal and vertical displacement, and stress distribution of foundation pit under four conditions. Comparing it with monitoring results, obtained that the simulation results and monitoring results is very close, the change trend is consistent. Stress concentration near the corner of the foundation pit is obvious, spatial effect is stronger. The stress increases with the increase of excavation depth at the bottom of the angle of foundation pit. Deformation of retaining structure presents a strong spatial effects:horizontal displacement of the retaining structures of foundation pit is the biggest; the corner near the foundation pit, the smaller the horizontal displacement of retaining structure.Applied the system to the management of deformation monitoring of a metro section cut-and-cover, greatly reduced the workload of construction monitoring. It is played a good supporting role in the management and analyzation for monitoring information. through the deformation monitoring contrastive analysis of the measured data with FLAC simulation data, confirmed that the FLAC numerical method suitable for subway interval Ming dig engineering deformation characteristics research.