Study On Deep Foundation Pit Secant Pile Supporting Structure Construction Monitoring And Numerical Simulation

With the development of China's urbanization process,a large number of high-rise buildings,subway stations,underground markets,underground municipal facilities and other underground projects have emerged,which also brought massive deep and large foundation pits.The secant pile has many advantages such as rapid construction speed,high safety,low cost and so on.The foundation pit excavation supporting system made up of anchor and secant pile can provide more construction space,and has the function of sealing,so its application prospect is very broad.Urban deep foundation pit engineering has higher requirements for excavation deformation control,because the surrounding buildings are dense and important.If the construction method is unreasonable,it may bring serious problems like foundation pit unsteadiness.Therefore,it has great significance to study the deformation characteristics of deep foundation pit on the safety control of construction.Based on the deep foundation pit engineering of a water purification plant in Tianshui City,this paper explained the various forms of deformation of foundation pit by means of theoretical analysis.The numerical simulation carried out the deformation law of foundation pit in each construction stage.The deformation law of foundation pit and retaining structure was analyzed and the numerical result was verified through field monitoring.In this paper,the main research results are as follows:(1)The monitoring scheme was designed based on the relevant norms and the actual characteristics of the foundation pit.According to this scheme,monitoring indicators were measured in the process of excavation and support.Through the analysis of the monitoring data of different excavation stages,the change law of foundation pit deformation was summarized.There is obvious variation in monitoring data especially in the late period of excavation because of overexcavation.(2)The process of excavation and support was simulated.The overexcavation model corresponding to the actual construction was compared with the normal construction.The simulation results in the condition of overexcavation were consistent with the monitoring datas,which verified that the numerical model was reasonable.And overexcavation had an obvious effect on the deformation of foundation pit and support structure.(3)Based on the principle of fiber brag grating sensing,a clinometer and an earth pressure sensor were designed.Through flexible application of the principle of fiber brag grating sensing,a real-time on-line monitoring system for the foundation pit was established based on common software platform of the existing monitoring.This monitoring system was suitable for pile-anchor support foundation pit.