Study On The Influence Of Finite Soil Width On The Deformation Characteristics Of Supporting Structure

With the continuous advancement ofmy country’s urbanization process,the construction of urban rail transit is also in full swing.The foundation pit engineering of subway stations often encounters finite soil conditions.Under finite soil conditions,the previous research on the force and deformation characteristics of the retaining structure is not in-depth and unsystematic with imperfect design calculationsmethod.In this paper,four groups ofmodel tests with different widths and eight groups of numerical simulations with different widths are carried out by combiningmodel test and numerical simulation,and the systematic study is operated for the deformation law of retaining structure,internal force and surface settlement under finite soil with different widths.The preliminary conclusions are as follows.(1)Variation rule of deep horizontal displacement of finite soil piles with different widthscan be showed as below: In the case of the same excavation depth,the semi-infinite soil side is less affected by the width as the width of finite soil increases,and themaximum horizontal displacement of the retaining pile at the finite soil side increases linearly and gradually approaches themaximum horizontal displacement at the semi-infinite soil side.In the case of the same finite soil width,themaximum horizontal displacement of piles on both sides of the foundation pit increases nearly linearly with the increase of excavation depth,but the increase amplitude of the finite soil side is less than that of the semi-infinite soil side.According to the linear fitting principle ofmaximum horizontal displacement of lateral pile of finite soilmass inmodel test,the critical width of finite soilmass obtained by fitting is smaller than the theoretical calculation of the critical width of finite soilmass.Therefore,it can be deduced that the soil pressure of retaining pile calculated according to the existing theoretical calculationmethod is too large.(2)Variation rule of surface settlement on both sides of foundation pit with finite soil with different widths can be illustrated as follows.In the case of the same excavation depth,themaximum surface settlement of finite soil increases linearly with the increasing width of finite soil,and gradually approaches themaximum surface settlement of semi-infinite soil.In the case of the same finite soil width,themaximum surface settlement on both sides of the foundation pit increases gradually with the increase of excavation depth,but themaximum surface settlement on the semi-infinite soil side increases faster than that on the finite soil side.According to the linear fitting results of themaximum value of surface settlement in themodel test,the critical width of the finite soilmass is smaller than that of the existing theoretical calculation.(3)Variation rule of pile bendingmoment on both sides of foundation pit with finite soil with different widths can be displayed like the following.In the case of the same excavation depth,with the increasing of the width of finite soil,themaximum negative bendingmoment at the side of finite soil does not changemuch,but themaximum positive bendingmoment increases nearly linearly,and gradually approaches themaximum positive bendingmoment at the side of semi-infinite soil.In the case of the same finite soil width,themaximum negative bendingmoment of the pile increases gradually but not greatly with the increase of excavation depth,and themaximum positive bendingmoment of the pile on both sides of the foundation pit increases gradually,and the increase range of themaximum positive bendingmoment of the semi-infinite soil side is greater than that of the finite soil side.According to the linear fitting results of themaximum positive bendingmoment of the pile in themodel test,it is known that the critical width of the finite soil is all smaller than that of the existing theoretical calculation.The conclusion can enrich the related theory of finite soil foundation pit engineering design and calculation,and also has a certain guiding effect on similar engineering design and calculation.