Study On Slurry Diffusion Law Of Grouting And Its Lifting Effect On Shield Tunnels

Uneven settlement of shield tunnels may occur under long-term load during operation.Grouting into stratum is one of the effective measures to restore tunnel settlement.However,the theory of grouting lifting lags far behind the engineering practice,which limits the application and development of grouting lifting technology.Therefore,this paper studies the diffusion of cement slurry and the grouting lifting of shield tunnels by means of theoretical research,indoor model test and numerical simulation.The main research contents and results are as follows:(1)Based on the spherical diffusion theory,the theoretical formulas of percolation diffusion of Power-law,Bingham and Newton slurry with consideration of the self-weight effect were established,and the distribution law of grouting pressure was discussed.(2)Through the rheological test,the influence of water cement ratio on the rheological properties of cement slurry was analyzed,and both the relationship between yield stress and water cement ratio of cement slurry and the relationship between viscosity and water cement ratio of cement slurry were established,which can be used to predict yield stress and viscosity of cement slurry under different water cement ratio(0.6~2.0).Based on screening test,permeability test and GDS triaxial test,the relevant physical and mechanical indexes of sand were obtained,which layed a foundation for numerical simulation analysis of grouting lifting in shield tunnel.(3)A set of grouting model test system was developed independently,and the diffusion model test of grouting was carried out.The influence of grouting direction,water cement ratio and grouting pressure on grouting slurry quality and the size of grouting stone was analyzed.Based on the permeation diffusion model of Bingham slurry considering the self-weight effect,prediction model of the average size of grouting stone was established and then verified with the test results.It is found that the theoretical value of the average size of grouting stone is 1.5~3 times that of horizontal grouting test and 1.5~2.5 times that of vertical grouting test.In addition,the distribution law of cement particle content in grouting stone was studied.It is acknowleged that the cement particle content decreases nonlinearly along the radius direction of grouting stone,and the cement particle content at the edge is between 4% and 12%.(4)The model test of shield tunnel grouting lifting was carried out,and the variation of tunnel and ground displacement under different buried depth was analyzed.The results show that the lifting displacement curve of the soil surface presents an inverted "bell" shape,which distributes symmetrically along the central axis of the shield tunnel.(5)Based on the mechanical parameters measured in indoor tests,the lifting effects of soil and tunnel under different burial depth and grouting pressure were simulated by finite element method.The results show that the model test and numerical simulation results are in good agreement.