| The influence of dewatering on the stability of deep foundation pit mainly includes the stability of seepage in the pit caused by dewatering,the stability of sudden surge at the bottom of the pit and the safety of retaining structure.In the existing specifications,it is given that open drainage is suitable for foundation pit dewatering with drawdown less than 2m,and well point dewatering method is recommended for deep foundation pit dewatering with high water level.But in the actual foundation pit engineering,due to the influence of geological conditions and construction quality,the well point dewatering may not achieve the expected dewatering effect.Taking the foundation pit of the West anchorage of Lingdingyang bridge in Shenzhong corridor as an example,this paper theoretically analyzes the influence of dewatering on the stability of the foundation pit,and comes to the conclusion that under the condition that the diaphragm wall is embedded in the rock,there is no confined aquifer at the bottom of the foundation pit,and the construction quality of the diaphragm wall can be guaranteed,the well point dewatering can be cancelled,and the open ditch drainage can be used as the groundwater control method of the deep foundation pit.Furthermore,through Midas GTS,three-dimensional finite element models of foundation pit under two working conditions of pipe well dewatering excavation and open ditch drainage excavation are established to study the influence of different dewatering methods on the retaining structure of foundation pit.It is found that for two different ways of precipitation,the stress and deformation of the retaining structure of foundation pit are very small when the groundwater level is the same,and the larger the groundwater level is,the greater the stress and deformation of the retaining structure of foundation pit will be.Finally,the real-time monitoring of the foundation pit retaining structure and surrounding environment is carried out,and the internal force and deformation data of the foundation pit retaining structure in the excavation process are collected and sorted out.The actual monitoring data and the calculation data of the open ditch drainage excavation model are compared and analyzed,which provides effective support for the reliability of the foundation pit model established in this paper.The main work of this paper is as follows(1)Consult the relevant literature to understand the research status of dewatering methods used in foundation pit excavation and the influence of dewatering on the stability of foundation pit.The failure mode of foundation pit instability is sorted out,and the stability problem of foundation pit caused by dewatering is analyzed theoretically.The conditions of canceling well point dewatering for deep foundation pit with high water level are obtained.(2)Midas GTS is used to carry out numerical calculation for the dewatering excavation of the foundation pit project,and the stress and deformation of the foundation pit retaining structure under two different groundwater control methods of pipe well dewatering and open ditch drainage are simulated.By comparing and analyzing the numerical results of the two cases,the stress and deformation laws of the retaining structure of foundation pit under different working conditions are found.(3)Participated in the formulation of the Lingdingyang Bridge West Anchor Foundation pit monitoring plan and precipitation plan,and monitored the foundation pit enclosure structure,the surrounding environment of the foundation pit and artificial islands,and sorted out the monitoring data of various working conditions.Comparing the results of the numerical simulation with the actual monitoring data,it is found that the simulation can effectively reflect the actual engineering situation.(4)This paper analyzes the influence of dewatering on the stability of foundation pit in practical engineering,and provides reference for the implementation of dewatering measures in similar foundation pit engineering. |
PDF Full Text Request