Research On Ground Settlement Characteristics Of Foundation Pit Dewatering Project

On the one hand,the foundation pit dewatering can lower the groundwater level below the bottom of the pit,which is convenient for dry construction and can effectively improve the physical and mechanical properties of the soil;On the other hand,due to precipitation,the pore water pressure is reduced,and the effective stress is increased,which causes the ground subsidence to affect the safety of surrounding buildings and Underground pipeline.The surrounding ground subsidence caused by foundation pit dewatering has now attracted the attention of many scholars,but there is currently a lack of systematic research.Therefore,this topic will study the reliability of numerical simulation results of foundation pit deformation and the characteristics of foundation pit deformation under the joint influence of precipitation and excavation.Based on this,systematically study the factors affecting land subsidence in foundation pit dewatering engineering.And the characteristics of land subsidence under these factors,which provides a reference for the design and construction of foundation pit dewatering engineering.In order to study the effect of foundation pit precipitation on land subsidence,in this paper,the three-dimensional finite element model is established based on the engineering section of the tunnel foundation pit S4,S5 and S6 in Changchun South Fourth Ring under the Linhe Street Project.The characteristics of land subsidence under foundation pit dewatering conditions are analyzed by the seepage-stress analysis module of finite element software.Through the comparison between the simulated values of the four aspects of the deformation of the pier and the actual monitoring values from the ground settlement,lateral displacement,foundation pit uplift,It is concluded that the numerical simulation results can accurately reflect the real situation of the foundation pit dewatering project.It is concluded that the ground settlement deformation in the foundation pit excavation project is similar to the groove shape,the lateral displacement deformation is similar to the parabola shape,and the maximum lateral displacement is at the position of 5m above the bottom of the pit.When the excavation depth is small,the deformation of the bottom of the pit is generally a small elastic small bulge in the middle and large sides.With the increase of the excavation depth,the deformation of the bottom of the pit will be transformed from a small elastic small ridge on both sides to a large plastic ridge on both sides.In the analysis of the deformation of the pier,it is concluded that precipitation has a great influence on the surrounding building facilities,and certain measures should be taken in the actual project.This paper is based on the analysis of precipitation excavation,Simulate the impact of precipitation on land subsidence by assuming that precipitation is not considered in consideration of excavation,Precipitation is a non-negligible factor that causes land subsidence.In this paper,five different precipitation schemes,including the depth of the water curtain,the depth of the precipitation well,the spacing of the precipitation well,the distance from the edge of the foundation,and the presence or absence of recharge,are used to analyze the impact of the foundation pit dewatering project on the ground subsidence.It is concluded that the depth of the water curtain has a great influence on the ground settlement.However,when the depth reaches a certain value,the influence of increasing the depth of the curtain curtain on the ground settlement is obviously weakened.Moreover,the ground subsidence increases with the increase of the depth of the precipitation well and decreases with the increase of the well spacing of the precipitation well.In terms of recharge,recharge can play a good role in the control of land subsidence and the protection of groundwater,and rechargesignificantly reduces the scope of impact and the degree of impact.As for the study of the distance between the precipitation well and the edge of the foundation pit,it is found that the increase of the distance from the edge of the foundation pit to the foundation pit is not obvious to the ground subsidence and the influence range compared with the above factors.