Numerical Analysis Of Influence Of Shield Tunneling Excavation On Pile Foundations Of Adjacent Buildings

Due to the rapid and continuous development of China's economic construction,the transportation system has reached an unprecedentedly high degree of prosperity.In addition,in the urban environment,high-rise and super-high-rise buildings are densely populated,and even bridges,elevated railways,and other structures are numerous,and most of their basic forms are Pile foundations,due to the constraints of underground space and routes,most of the tunnel construction needs to pass from the side,bottom,or other locations of existing pile foundations.The construction process of the subway tunnel will cause the redistribution of surrounding soil stress caused by changes in the surrounding formation environment,which will affect the settlement deformation of nearby landmarks and the internal forces and deformations of the nearby existing structural pile foundations,as well as the bearing capacity of the pile foundation,and will directly threaten the use of the structure.Since the stability of the bearing capacity of the building foundation will determine the safe use of the superstructure,it is particularly important to study the effect of shield excavation on the deformation of the adjacent pile foundation and surrounding soil layers.After learning about the related mechanics of civil engineering during study,in this paper,the commonly used numerical software ABAQUS modeling is used to study the deformation mechanism of tunnel shield excavation in adjacent strata and piles.Considering the influence of different shield construction stages on the pile deformation and internal force changes,the influence of the isomorphic layer hardening on the adjacent pile body is analyzed by using the single-factor control method.On this basis,the influence of shield excavation on the deformation of the nearby twin piles was further studied.The main research is as follows:(1)Summarizes the impact of the current tunnel construction on the adjacent building piles and the corresponding protection and control measures,and briefly introduces the basic knowledge of ABAQUS software,unit life and death techniques,and the application of soil constitutive relations in ABAQUS.(2)This numerical simulation considers the construction parameters such as the pressure of the soil in the excavation surface,the friction between the grouting layer,the surface of the shield machine and the soil layer,the influence of the shield tail grouting layer on the land subsidence,and the disturbance of the excavation surface.It mainly studies the influence mechanism and laws of the settlement of the stratum above the axis caused by the construction of the subway tunnel near a single pile.(3)The numerical modeling calculation analyzes the influence of the shield construction of the subway on the deformation of the pile and the internal force of the single pile on the side of the building.It shows that the displacement and bending moment of the pile near the tunnel change greatly.(4)Using the single-factor control method,under the same conditions of other factors,when simulating the shield construction of subways,the elastic modulus of the equivalent layer was changed to explore the effect of hardening at different times to study the effect of calculation on the pile deformation of a single pile in an adjacent building,and to conduct a comparative analysis of the law.(5)In combination with the analysis of a single pile,a two-pile numerical model was established with the same parameters and the distance between piles was 4m.Further research was conducted to analyze the impact of shield tunnel construction on surrounding formation displacement.In addition,the effect of the deformation and internal force of the pile on the side of the twin piles was studied.At the same time,the effect of deformation on the No.1 pile and the single pile and the No.2 pile of the same location were compared.It is found that the changes in the lateral frictional resistance and the axial force of the pile are very small,and the bending moment of the single pile at the same position is larger than that of the No.1 pile.