Numerical Simulation Study On Deep Foundation Pit Excavation With Internal Support

Foundation pit engineering is one of the difficult and hot issue in the field of geotechnical engineering,the analysis of the domestic and foreign experts and scholars have done a lot of research work,has made some significant results.In this paper,two-dimensional plane strain and three-dimensional solid numerical analysis of the foundation pit excavation are carried out by means of PLAXIS 2D and MIDAS/GTS NX software.The influence of the model boundary size on the calculation results and the deformation of the deep foundation pit,the deformation of the supporting structure and the internal force change during the excavation of the foundation pit are studied.The influence of different supporting structure stiffness on the deformation and internal force of supporting structure is studied.The main research work of this paper is as follows:(1)The influence of the boundary size of the model on the deformation and internal force of the retaining structure is analyzed.The boundary dimension model a effective boundary size,when the size is smaller than the model boundary value,Boundary dimensions on the supporting structure deformation and internal force effect is obvious,and the boundary size is smaller,the impact is more obvious;when the model size is larger than the boundary value,the boundary size has little effect on the supporting structure deformation and internal node the negligible.(2)The deformation of deep foundation pit,the deformation of supporting structure and the change of internal force are analyzed.With the increase of excavation depth,the deformation of the foundation pit,the deformation and internal force of the retaining structure are gradually increased.(3)Tthe influence of supporting pile diameter on the deformation and internal force of support structure is analyzed.With the support of supporting pile diameter increases,retaining pile horizontal displacement decreases,retaining pile bending moment and shear force increases gradually;the retaining pile has a effective pile diameter,when the supporting pile diameter is less than the value,the supporting pile diameter of retaining pile deformation significantly,and the pile diameter is small,influence more significantly,when the pile diameter is greater than this value,the diameter of the pile on the ’supporting effect of the pile deformation is not obvious.(4)The influence of equivalent support stiffness on support pile is analyzed.The greater the equivalent support stiffness,the greater the horizontal displacement of the support pile,the smaller the ratio of the support axial force and the equivalent stiffness,the smaller the degree of support to the support pile.(5)When the axial force and the equivalent support stiffness ratio in 0.02～0.004,the support effect of the horizontal displacement of supporting pile capacity began to weaken,the ratio is less than 0.004,can be regarded as the change of support shaft stiffness of supporting pile has no effect,but when the ratio is greater than 0.02,supporting effect sensitive factors supporting pile displacement.