Field Test And The Surrounding Environment Of The Deep Pit Of City Subway Security Control

Deep foundation pit has been wide-spread applying in high-rise buildings,subway project and municipal engineering. This paper, based on the analysis of many relevant research at home and abroad, using the methods of on-site monitoring,theoretical analysis and numerical simulation, explores the law of force and deformation in the deep foundation pit retaining structure. At the same time, combined with engineering practice, absorption the advantages of strength reduction theory, discusses a method to calculate the safty factor of environments around deep pits. This method takes the horizontal deformation of retaining structure reached the control value in design as the critical ailture of surrounding environment. The major works and conclusions are as follows:(1) Based on the summarizing and analyzing of the development of deep foundation pit and research status at home and abroad, combined the complexity and shortcomings in design and construction, introduces the necessity of carrying out on-site monitoring;(2) Describes the deformation behavior of the foundation pit in the envelope structure and surrounding soil strata. Then analysis the deformation mechanism and summarizes the common method of calculating deformation of foundation pit;(3) Based on the deep foundation pit of line 3 in Shenzhen metro, formulates a practical monitoring program. By analyzing the on-site monitoring data, comes to the internal forces and deformation characteristics in envelope structure and the deformation about the surrounding environment. And through comparison with the control values to guide the smooth progress of construction; Research results provide references for similar project about design and construction experience;(4) Based on the deep foundation pit of line 3 in Shenzhen metro, using the method of finite difference, established FLAC3D numerical model. The calculated results with field measured results of the comparative analysis shows that the selected parameters can be well reflected in engineering practice. Using the above model, the pile-anchor retaining structure design parameters of its force and deformation to study the impact of the law;(5) Based on strength reduction, assuming the horizontal displacement of supporting structure to meet the control design value as the criterion of the structure around the foundation damaging, researched the safty margin of the surrounding environment, proposed a method to calculate the safety factor of the structure in foundation pit excavation.