Study On Numerical Calculation And Deformation Of Foundation Pit Based On Seepage-stress Coupling Analysis

As the scale of the construction enlarging,more and more deep foundation pit appears.With the maturity of technology,the depth of deep foundation pit engineering increases gradually,foundation pit deformation is regarded as the most important safety index in design and construction.This is the reason why more and more attention has been paid to the problem of foundation pit deformation.Meanwhile,in the construction of deep foundation pit in water-rich areas,the key problem to be solved first is the deformation of deep foundation pit under the influence of coupling effect,which is the interaction relations between seepage field and stress field.Deformation includes deformation of enclosure structure,heave of foundation pit bottom and settlement of surrounding surface,etc.Therefore,deformation analysis of deep foundation pit considering fluid-structure interaction is of great significance both in theoretical research and engineering practice.Based on the deep foundation pit engineering of Bozhou Jian'an tunnel,models are constructed by using the finite element program-Midas/GTS,the calculated data are compared with the monitoring data,on this account,the deformation law of foundation pit during excavation and the influence of seepage on the deformation of foundation pit are systematically studied.Then,the parameters are changed in the numerical model,so as to explore the influence of soil parameters,retaining structure parameters and construction factors on the deformation of foundation pit.The main research results of this paper are as follows.(1)The mechanism of deformation of foundation pit is analyzed theoretically,the seepage type and precipitation method in the process of foundation pit excavation are studied.At the same time,the theory of three-dimensional seepage-stress coupling analysis based on finite element method is studied,which provides theoretical basis for modeling and analysis.(2)Combining with engineering examples,two numerical models of foundation pit excavation without considering dewatering and with considering seepage-stress coupling are established.By comparing and analyzing three deformation indexes of foundation pit,i.e.surface settlement outside pit,basement uplift and diaphragm wall lateral displacement in monitoring data,it is concluded that seepage is an important factor affecting the deformation of deep foundation pit.(3)The finite element model considering seepage-stress coupling is used as the benchmark model.The cohesion,friction,stiffness,depth and overbreak depth of the diaphragm wall are changed respectively.A total of 28 calculation models are established.By comparing and analyzing the three deformation index data of foundation pit with the reference model,the influence of the above five factors on the deformation of foundation pit is explored.According to the analysis results,three measures to control the deformation of foundation pit are given according to the five factors mentioned above.