Study On The Influence Of Foundation Pit Construction Of Metro Station On The Surrounding Surface In Deep Soft Soil Area

In recent years,the urbanization rate continues to increase,as a subway project which can effectively alleviate the pressure of urban traffic,the subway project has gradually transferred from first-tier cities to second-tier cities.Due to the complexity of the deep foundation pit engineering,the deformation of the foundation pit itself and the uneven settlement of the surrounding soil and buildings caused by construction may affect the normal use of the station and the surrounding buildings.Based on the geological conditions and monitoring data of the foundation pit of Kehua Road Station,this paper studies the surrounding environmental deformation caused by the construction of the foundation pit of the station in the deep soft soil area.The main research contents are as follows:(1)The deformation law and calculation of the foundation pit and its surrounding environment are studied and summarized,and the relationship between the maximum surface settlement,the maximum deep horizontal position of the retaining wall and the excavation depth of the foundation pit is studied and analyzed by the method of statistical analysis.and the relationship between the maximum surface settlement and the maximum deep horizontal level of the retaining wall.(2)The numerical simulation model of the foundation pit is established,and the surface settlement,the top deformation of the retaining wall,the deep horizontal displacement of the retaining wall and the supporting axial force of the foundation pit under different working conditions are simulated according to the construction and excavation scheme.On this basis,buildings in different positions are added to the numerical model,the effects of different building locations on foundation pit surface settlement and building settlement are compared and analyzed,and the influence law of foundation pit excavation on surrounding buildings is studied.It is found that the existence of buildings makes the cross-sectional map of surface settlement through buildings show an "inverted triangle" shape,and the surface settlement near buildings is generally larger than that without buildings.(3)Based on the measured data of the foundation pit of Kehua Road Station,the deformation of the foundation pit caused by the foundation pit construction and itsinfluence on the surrounding buildings are studied,and the measured data of the foundation pit are compared with the simulated data.It is found that the top of the retaining wall is uplifted in the process of foundation pit excavation,and the horizontal displacement of the top of the retaining wall points to the direction of the foundation pit.The cross section of surface settlement gradually changes from "triangle" settlement to "parabola" settlement with the increase of foundation pit excavation depth,the deep horizontal displacement of retaining wall gradually changes from "cantilever" deformation to "parabola" deformation with the increase of foundation pit excavation depth,and the axial force of the first support is about 1.5 ?2.0 times of that of the third support in the process of excavation.In the process of foundation pit excavation,the buildings near the side of the foundation pit will have larger deformation,and the deformation of the buildings far away from the side of the foundation pit is smaller,and the differential settlement of the surrounding buildings is caused by the uneven settlement of the surface.In addition,by using the eccentric distribution density function,the formula for calculating the surface settlement caused by the deep horizontal displacement of the retaining wall of the deep foundation pit in the soft soil area is deduced.the calculated maximum surface settlement is basically consistent with the measured value,which can better predict the surface subsidence.It has good application value.