Study On Floating Mechanism And Control Technology Of Shield Tunnel Segment

In the process of shield tunnel construction,the slurry is not solidified in time,which leads to the floating of the segment,which will lead to the deviation of the tunnel axis,the dislocation or damage between the adjacent segments,the bolt between the segment structures will also be damaged and cut off,and the safety accidents such as seepage and water leakage in the tunnel will lead to the damage of the ground buildings and the safety problems of the subway in the later operation.Therefore,it is very important to study the floating problem of the segment in the process of shield tunnel construction.Through the analysis of the floating mechanism of the segment,the analysis model is established,and the theoretical calculation formula of the floating amount of the segment is derived.Based on ABAQUS numerical simulation software,a three-dimensional numerical analysis model during shield tunnel construction is established.The effects of slurry solidification time,grouting pressure,elastic modulus of slurry,soil pressure,thickness of grouting layer and groundwater on the floating amount of segments are analyzed.The control measures of segment floating are proposed.The main conclusions of this paper are as follows :(1)Through the analysis of the influence factors of segment floating,the buoyancy of the segment is divided into ’ static buoyancy ’ caused by the buoyancy of the slurry itself and ’dynamic buoyancy ’ caused by grouting pressure.Through the analysis of the segment force,the theoretical calculation formula of the segment floating amount is derived.(2)The numerical analysis shows that the longer the solidification time of the slurry is,the longer the buoyancy action time of the segment is,which leads to the increase of the floating amount of the segment.When the grouting pressure is uniformly distributed around the segment,the floating amount of the segment increases with the increase of the grouting pressure.The elastic modulus of the slurry increases,the compressibility of the slurry itself decreases,and the floating space of the segment decreases,so the floating amount of the segment decreases.The greater the pressure of the soil bin,the soil in front of the soil is prone to uplift,and the floating amount of the segment increases.The thickness of the grouting layer increases,the grouting amount increases,and the floating amount of the segment decreases.The volume of groundwater in the shield tail gap decreases,and the floating amount of the segment decreases.(3)Combined with the engineering geological conditions of a shield section of Hefei Rail Transit Line 7,the influencing factors of segment floating are analyzed,and the relevant measures to control segment floating are put forward,which provides some reference for similar projects in the future.Figure [63] table [10] reference [50]...