Deformation Monitoring And Deformation Of Deep Foundation Pit

In order to relieve the problem of land shortage and traffic congestion, the foundation pit engineering develops in the direction of deeper and more.Taking the underneath pass tunnel foundation pit involved in the overpass project of readers road, which is located in Tianshui road of Lanzhou as an example, the author introduces the supporting structure type selection of the narrow-long deep foundation pit and its design.At the same time, based on the bored piles and steel support supporting structure as the research object, adopting the method of combination of field monitoring and numerical simulation, the thesis mainly studies:(1)The division of deep foundation pit excavation process, construction process, and the calculation of the internal force displacement of retaining structure under each operating condition.(2) the deformation monitoring in construction field and study on the deformation rules of retaining structure, and using the data to guide field construction in order to make the whole construction project always in a safe state.(3) According to the different construction conditions, making use of finite element simulation software to simulate each working condition so as to conclude the pile body’s horizontal displacement and ground surface settlement of each working condition and make a comparative analysis with the measured results.The main research contents and conclusions are as follows:(1) A systematic summary is made on the common forms of supporting,supporting structure’s destruction forms of deep foundation pit and the influence factors and control measures of deep foundation pit deformation.(2) The author makes an in-depth introduction to the retaining pile design of tunnel excavation under readers road located in Tianshui avenue of Lanzhou, at the same time gives the diagram of supporting structure internal force and deformation results of various working conditions during the process of foundation pit excavation, which can provide design basis for similar projects.(3) The successful implementation of foundation bored + steel support support programs, the measured maximum horizontal displacement of pile top 13.8mm, is far less than warning value 30 mm regulatory requirements, proved that the support program can effectively limit the pit deformation.(4) With increasing depth of the excavation, the displacement of envelope pile increases, applied about each excavation stage horizontal displacement and depth variations and steel support, increases the depth of the excavation pit, horizontal displacement of the pile envelope the maximum horizontal displacement of the position gradually decreased from forward type to bow-type transition, the maximum horizontal displacement occurs in the excavation depth of 2/3, and also near the bottom of the pile with a small amount of displacement.(5) Through the finite element calculation, the author concludes the horizontal displacement and the surface subsidence of the pile body.Compared with the measured results, the two development trends are basically identical, which shows that the finite element calculation results can provide some reference for the design of foundation pit.