Study On The Deformation Law Of Pile-anchor Support In The Spring Water Bearing Area Of Jinan City

There are still many difficulties in foundation pit excavation and support.Based on the Jiali foundation pit project in Jinan confined water area,this paper systematically analyzes the deformation of pile anchor support in the whole excavation process,using FLAC-3D The finite difference software analyzes the horizontal displacement of the foudation pit in each stage of the layered excavation construction,the settlement of the surface soil around the foundation pit,the uplift of the bottom of the pit and the stress of the anchor rod.It focuses on the adverse impact of the change of the confined water head on the deformation of the foundation pit.The conclusions are as follows(1)The hydrogeology and engineering geological conditions of the project are analyzed,and the pile anchor support scheme is selected to ensure the safety of foundation pit excavation.In order to control the deformation of foundation pit effectively,measures such as pipe well dewatering,layered excavation and application of water curtain are adopted.And according to the relevant specifications,the site monitoring scheme of the foundation pit is formulated.Through the analysis of the monitoring data,the rationality of the support scheme is verified.(2)FLAC-3D software was used to simulate the whole excavation process of the foundation pit,and the deformation law of the pile anchor supporting structure was obtained:with the increase of the excavation depth of the foundation pit,the horizontal displacement of the retaining structure increased.When the excavation reached the bottom of the foundation pit,the maximum horizontal displacement of the retaining structure was about 6m away from the top of the foundation pit When the excavation reaches the bottom of the pit,the maximum uplift is 1.64 cm,which occurs in the range of 3M ～ 5m away from the retaining structure.With the increase of the excavation depth of the foundation pit,the surrounding rock and soil mass around the foundation pit will be subject to certain settlement,and the settlement will increase continuously.When the excavation reaches the bottom of the pit,it will be 4m ～ 5m away from the edge of the foundation pit The maximum land subsidence is 1.85 cm.(3)Comparing the numerical results with the field monitoring data,it is found that the two have a good agreement.Although the calculation results of numerical simulation are larger than the measured results,it is conducive to the safety of foundation pit design.(4)It is found that: with the increase of confined water head,the horizontal displacement of pile body,the horizontal displacement of soil around the pit,the uplift of pit bottom and the ground settlement around the foundation pit increase with the increase of confined water head.The influence of confined water on the stress of anchor cable is more complex.With the increase of confined water head,the tensile stress of anchor cable is affected It increases first,then decreases and then increases.