Study On The Influence Of Shield Driving Thrust On Foundation Pit Deformation

A large number of people gather in the city,making the city more crowded,space becomes scarce resources,and the city’s demand for three-dimensional space utilization is getting higher and higher.Subway has gradually become the main means of transportation in major cities.With the increase of deep foundation pit and shield engineering,the support engineering of foundation pit has also received a lot of attention.Compared with the development of superstructure,the application of deep foundation pit support is relatively late.In the process of shield driving into the foundation pit,the influence of shield on the stability of deep foundation pit is rarely studied.In practical engineering,shield parameters of shield machine,such as the selection of total thrust of shield machine,are generally based on the analysis and experience of the results obtained from the test tunneling,and lack of relevant theoretical reference.Generally based on the result analysis and experience of trial excavation,there is a lack of relevant theoretical reference.The project selected in this paper is the No.1 air shaft in the middle of Caoqiao Station,the new site of Beijing Metro Line 19.Based on the actual supporting scheme,design report and survey report,the FLAC3 D finite element numerical model is established to simulate the excavation of foundation pit after completion of excavation.The stability of foundation pit caused by shield driving is studied.The influence of different shield thrust on the stability of foundation pit is also studied.Specific research contents are as follows:Firstly,according to the measured data,the deformation characteristics and laws of existing supporting piles and ground settlement are analyzed.Secondly,the FLAC3 D model is established according to the engineering data,and the reliability of the model is verified by calculating and restoring the actual working conditions of the site.Thirdly,adjust the thrust of shield,and compare the deformation of foundation pit pile and ground settlement under different thrust schemes.The results are as follows:The maximum horizontal displacement is 9 meters away from the surface,and the displacement is 17.4 mm,showing a shift to the pit.Surface subsidence appears near the foundation pit,and the maximum settlement is 5.38 mm,which is within the control value range.Horizontal displacement of retaining pile increases with the increase of shield thrust,and the deformation trend tends to be consistent,all of which migrate to the pit.The surrounding soil heaves up with the increase of shield thrust,and the deformation trend tends to be consistent.Through multi-group model analysis,when the shield thrust is added to the maximum value,the horizontal displacement of the foundation pit pile and the ground settlement are within the control value,and the shield thrust has little effect on the deformation of the foundation pit in this project.