Research On The Influence Of Bias Load And Excavation Width On The Stability And Deformation Of Pit Foundation

For the excavation of foundation pits,many scholars have carried out related research on the internal force and deformation of the retaining structure,the deformation of surrounding soils and the stability safety factor of foundation pit during the excavation.However,the research on the influence of bias loads and pit width on the stability of pits in previous studies is still rare.In this paper,the foundation pit of Baijiayuan Station on Tianmushan Road of Hangzhou Metro Line 3 is used as the research background.Through theoretical analysis and numerical simulation,the effects of bias and width effects on the stability of foundation pit are studied.The main contents of this article are as follows:1.Aiming at the bias characteristic of the subway station foundation pit,a calculation method for the stability of the foundation pit against the uplift is proposed.The method takes into account the influence of the bias load range and the pit edge distance,and considers anisotropy of soils.The results of this method are compared with the finite element model of deep excavation of Boston blue clay proposed by Hashash and Whittle,and the validity of the method is verified.Analysis of the influence of the magnitude of the biased load,the pit edge distance,and the distribution area on the safety factor of the uplift through numerical examples.The influence of factors such as the depth of the retaining wall into the soil,the depth of the foundation pit,the anisotropy of the soil,the distance from the next support to the bottom of the pit on the uplift safety factor are discussed.Finally,the differences between this method and limit equilibrium method,limit analysis method and finite element strength reduction method in considering the biased load are compared and analyzed.2.Based on the Plaxis2 D finite element numerical simulation software and relying on the Baijiayuan Station engineering example,the horizontal displacement of the retaining structure,the internal force of the retaining wall(bending moment and shear force),the surrounding ground settlement,deformation of the pit bottom and other related deformation characteristics of the foundation pit are investigated.By comparing with the unbiased working condition,the influence of the biased load on the deformation behavior of the foundation pit under the two biased working conditions is analyzed.3.A series of two-dimensional finite element analysis models with different geometrical dimensions were established for the characteristics of the narrow foundation pit of the subway foundation pit in Hangzhou Metro Line 3 project.The finite element strength reduction method is used to calculate the bulge safety factor of the foundation pit,and the width and depth ratio limits ofthe wide and narrow foundation pits were obtained based on the safety factor of the bulge.Through numerical calculations,the variation rules of the foundation pit bottom bulge,the surrounding ground settlement,the displacement and deformation of the retaining wall,the internal force of the retaining wall(bending moment and shear force),and the supporting axial force are analyzed under different excavation widths.