Study On The Influence Of Subway Shield Construction On Soil And Adjacent Existing Buildings

With the development of urbanization in China,the contradiction between the increasing population and the scarcity of surface space urges people to focus on the utilization of underground space.The emergence of subway has solved this problem to a great extent.Subway lines generally run through downtown areas,covering a wide range and many surrounding buildings,so there are not a few existing buildings adjacent to subway tunnel construction.Metro shield construction must have a certain impact on adjacent existing buildings,and even lead to the destruction of these buildings.Based on the excavation project of a subway section in Hefei,the specific research contents and conclusions are as follows:（1）The deformation theory of the tunnel on the surrounding soil and the influence mechanism of the tunnel on the deformation of existing buildings are comprehensively sorted out,and the influencing factors of tunnel excavation on the deformation of existing buildings are summarized,and the control standard values of relevant codes on the deformation of existing buildings are sorted out.（2）PLAXIS 3D is used to simulate and calculate the tunnel shield section.After comparing with the monitoring data recorded on site,it is found that the deformation value is close,which verifies the rationality of modeling and calculation.Further analyze the influence of formation loss rate C_ref,the ratio of soil unloading modulus E_urand secant modulus E₅₀,soil buried depth d and tunnel spacing L on soil deformation:among them,formation loss rate C_refhas the greatest influence and tunnel spacing L has the least influence on soil deformation.At the same time,give suggestions.When similar projects are carried out in Hefei,formation loss rate C_refThe ratio of unloading modulus E_urand secant modulus E₅₀of soil can be taken as 0.4%and 4.0 times of the empirical value.（3）This paper introduces the influence of the buried depth of the tunnel d and the distance L from the center line of the tunnel to the existing building on the deformation of the existing building.The modeling calculation shows that the equivalent differential settlement of the adjacent column foundation of the existing building is 0.000308l and less than 0.002l,indicating that the deformation is in the requirements of the control code and can be calculated later,At the same time,the influence of buried depth d and distance L on the deformation of existing buildings is analyzed:with the increase of these two variables,the deformation of existing buildings decreases,and the influence of distance L on existing buildings is relatively greater than that of buried depth d.（4）Soil excavation after adding isolation piles has an obvious control effect on the column foundation deformation of existing buildings,and the influence on the vertical settlement deformation of buildings is greater than that on the lateral deformation.At the same time,by changing the buried depth D of the isolation wall and the distance H from the isolation pile to the existing building,it is found that with the increase of both,the deformation indexes of the existing building are relatively reduced.In general,the influence of the buried depth D of the separation wall on the existing buildings is greater than that of the distance H.Figure[142]Table[30]Reference[84]...