| With the wide use of shield tunneling method in the important underground engineering in our country,it has become a major method applied in tunnel construction.During the construction with shield machine,backfill grouting is a necessary and key procedure,which can actively control stratum displacement by filling the shield tail void,and thus reduce the disturbance of structures around it and maintain the stability of the tunnel.In this paper,the basic grout properties,viscosity degeneration,surface pattern and its influence on stratum deformation were studied,based on the cement-sodium silicate grout of shield grouting.And conclusions can be summarized as follows:(1)Cement-sodium silicate grouting material was researched by orthogonal experiment design,and the grout properties were tested.Water-cement ratio,Baume dosage,cement and sodium silicate volume ratio all have great influence on the grout engineering properties,experimental analysis results shows that water cement ratio is the main factor for the gel time and compressive strength,the Baume degree is major for the stone rate.According to range analysis method,the optimal ratio of slurry is A2B1C1—the water cement ratio is 1.0,Baume degree was 35 Be',the cement slurry and soluble silicate volume ratio is 1:0.3.(2)In order to improve the performance of cement-sodium silicate,contrast experiments were done when there were two kinds of admixtures.The experiments include gel time experiment,stone rate experiment,compressive strength experiment,and different water cement ratio.The test results show that the water cement ratio is not more than 1.0,the gel time increases and the stone rate first increases and then decreases with the increase of the concentration of aluminum chloride and sodium hydrogen phosphate;the compressive strength increases with the increase of the concentration of aluminum chloride,and first increases then decrease with the increase of sodium hydrogen phosphate.Overall,the effect of aluminum chloride solution was more significant than that of sodium hydrogen phosphate.(3)The test of the lurry viscosity denaturation was carried out,and the changing curves of the viscosity of the liquid slurry of different water cement ratio were obtained,the viscosity expression formula with time variable was reached by using Origin.The results show that the smaller the water cement ratio is,the larger the viscosity is.The viscosity of slurry with different water cement ratio increases with the increase of grouting time,and increases with the natural logarithm;it is proved that the cement-sodium silicate slurry in the range of water cement ratio is in accordance with Bingham fluid characteristics.(4)Using 3D laser scanning microscope to observe the surface topography of the the smooth slurry and the fraturing lurry and get the 3D laser image at different magnification.The fracture profile of fracturing fluid was measured,and the profile curve,depth,width,curvature and angle of slurry were obtained.(5)The indoor model test was carried out to study the effect of shield grouting on soil.On the basis of similarity ratio,the similar experimental soil materials developed,based on soil test basic parameters of artificial soil model obtained;compared the different ratio of grouting materials,grouting pressure,tunnel depth on the influence of surface subsidence effect.The results show that the optimal proportioning scheme has a more significant effect on reducing the surface settlement;within the reasonable range,the greater the grouting pressure,the smaller the settlement;the settlement of two times buried depth of the tunnel is smaller than that of one time. |
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