Study On Soil Pressure And Support Structure Stress And Deformation Of Deep Foundation Pit In Soft Soil

The determination of the earth pressure of diaphragm wall in foundation pit is a key problem in the design and construction of foundation pit.Therefore,how to determine the earth pressure of diaphragm wall in foundation pit to make it possible to approach the engineering practice is the focus of attention in the field of foundation pit engineering.Based on the foundation pit engineering of Daliang Station of Foshan Metro Line 3,this paper studies the earth pressure and deformation of the retaining structure of Daliang Station soft soil foundation pit by means of theoretical analysis and numerical simulation,based on the field monitoring data.The main contents are as follows:(1)The monitoring data of diaphragm wall deformation,groundwater level change and surface subsidence deformation are analyzed.(2)Based on the horizontal displacement monitoring data of the foundation pit wall of Daliang Station,the bending moment and earth pressure on the diaphragm wall when the foundation pit of Daliang Station is excavated to the bottom of the pit are inverted by using the cubic spline interpolation method.The inversion earth pressure value is between the calculating static soil pressure by soil with water and soil and water separation for static soil pressure.(3)The ratio of measured pore water pressure to hydrostatic pressure in Daliang Station foundation pit is less than 1,and the ratio decreases with the construction of foundation pit.Based on Bernoulli equation,the calculation method of pore water pressure considering seepage force is obtained,and the calculation value of pore water pressure is obtained.Combined with the calculation result,the method of calculating soil and water pressure is revised.Comparing the calculated results of earth pressure correction with those of theoretical calculation,it is found that the calculated values of earth pressure under the influence of seepage are basically between the static earth pressure and the active earth pressure separated by water and soil,and are close to the active earth pressure separated by water and soil.(4)Two-dimensional contrast model for simulating foundation pit construction under consideration of seepage and no consideration of seepage is established by ABAQUS finite element software.Through the analysis of the calculation results,it is found that the law of stress and deformation of the foundation pit is the same in the two cases,but there are great differences in the amount of deformation and the magnitude of stress.The reason is that the earth pressure decreases and the seepage force increases when seepage occurs.Seepage has an important influence on the wall deformation,surface settlement and settlement range.