Study On Tunnel Floating And Segment Dislocation Due To Synchronous Grouting In Shield Tunnel Construction

In shield tunnel construction,because the diameter of the shield shell is larger than the diameter of the segment,the gap between the pipe and the stratum will form,which will cause the displacement of the stratum and cause the surface subsidence.The back-filled grouting can effectively fill the gap of shield tail.However,when the grouting pressure is too high,it will cause the whole tunnel to float up or the partial dislocation of the segment.In this paper,the influence of synchronous grouting on the floating of tunnel and the dislocation of the pipe is the main frame.The distribution law of the filling pressure,the law of the permeation and diffusion of the slurry,the effect of the buoyancy produced by the grouting on the partial dislocation of the segment and the overall floating of the tunnel,and the law of the Dislocation of segment in shield tunnel construction are systematically studied.(1)It is assumed that the grouting slurry is Newton fluid and Bingham fluid,and the shield tail gap is simplified as a uniform ring column shape.The Filling diffusion model of synchronous grouting in shield tunnel is established.The pressure expression of the slurry filling diffusion is derived.The influence of the number and position of the grouting hole,the radius of the tunnel and the size of the shield tail gap on the pressure distribution is studied.(2)It is assumed that the grouting slurry is a power-law fluid.Based on the theory of hemispherical surface diffusion,the model of the grouting permeation diffusion is established.The spatial distribution equation of the slurry consistency is derived.Combined with the time variability of slurry consistency,the effect of the time and space distribution of the slurry consistency on the infiltration and diffusion of the slurry is analyzed.The pressure expression of slurry to segment under the premise of considering the temporal and spatial distribution of slurry consistency is derived.(3)Considering the anti floating effect of the overlying soil and the segment joint of the tunnel,the local anti floating calculation of the shield tunnel is carried out with the single block and the whole ring(number ring)segment as the research object,and the anti buoyancy of the single block is mainly provided by the shear strength of the bolt.The anti buoyancy of the whole ring piece is mainly carried out by the overlying soil and the shear strength of the joint.In addition,taking the bolt shear failure as the control standard,the maximum grouting pressure can be obtained.(4)Based on the Kerr elastic foundation beam principle,the shield tunnel is assumed to be a homogeneous infinite beam,and the longitudinal overall floating model of the shield tunnel is established.The displacement expression of the shield tunnel under the action of the upper buoyancy is deduced.The maximum floating amount of the tunnel is taken as the control standard,and the maximum grouting pressure of the tunnel is obtained.In addition,the sensitivity of the parameters such as the upper buoyancy(grouting pressure),the formation parameters(elastic modulus),the length of the slurry not solidified zone and the longitudinal effective stiffness of the tunnel are analyzed,and the sensitivity of the influencing factors is obtained.(5)Based on the load-structure model,the finite element software ANSYS is used to analyze the influence of the size of the grouting slurry pressure,the difference of slurry pressure,the local gap of the shield tail and the post wall grouting to the displacement and Dislocation of segment.The optimal slurry pressure difference is obtained by calculation.The maximum grouting pressure difference and the maximum back-filled grouting pressure of the grouting are obtained according to the control standard of the segment dislocation.