Supporting Construction Monitoring And Deformation Control Study Of Large And Deep Foundation Pit

The deep foundation pit is mostly in the center of the city.In order to ensure the stability of the deep foundation pit and protect the surrounding environment,it is necessary to control the deformation of the supporting structure and surrounding soil.In this paper,based on the deep foundation pit engineering of Hechang Trading Center in Quanzhou,the deformation control of supporting structure and surrounding soil is studied.Based on the analysis of monitoring data,changing rules of horizontal displacement of the retaining piles,reinforcement stress of supporting beam,vertical displacement of column,deformation of top slope,subsidence of surface,subsidence of buildings,subsidence of underground pipeline,earth pressure and water level are summed up,and the stability and deformation of deep foundation pit are evaluated;After comparison of Logistic curve,Gompertz curve,Usher curve and piecewise aging curve,appropriate forecasting model is selected to predict the deformation of foundation pit,effectively guiding the construction,and the control measures of deformation of deep foundation pit are discussed;FLAC3D is used to simulate the excavation process on 3D,and deformation of the retaining piles soil deformation,soil deformation,axial force of supporting beam,subsidence of column are analyzed according to the calculation results,and stability and deformation of the deep foundation pit are evaluated;The calculated values are compared with the measured values to verify the feasibility of simulation calculation.The main conclusions of this paper are as follows:(1)The deformation rules of foundation pit were summarized based on on-site monitoring,and the results showed that the supporting structure could ensure the safety and stability of the foundation pit,the style that design and construction combined with on-site monitoring,through the information feedback and adjustment of construction,had good controlling effects on foundation pit deformation.(2)Four kinds of deformation prediction model were compared based on the monitoring data,and the results showed that prediction effect of piecewise aging curve considering the construction conditions(Usher curve with parabola)was best;the result of predicting subsidence of surface and underground pipeline by piecewise aging curve showed that deformation in the range of warning value,which had a good reference value for the follow-up construction.(3)FLAC3D was used to simulated the project on three-dimensional,and the results showed that the supporting structure could maintain the stability of foundation pit,and deformation of surrounding soil was controlled in a safe range,which could provide guidance for deformation controlling in construction process;comparing analysis of calculated results and measured results showed that they were roughly coincident,horizontal displacement of supporting pile was close to the measured value,surface subsidence was less than measured value,the column subsidence was greater than the measured value,which indicated that FLAC3D had good feasibility on simulating the excavation deformation of deep foundation pit.