| When the shield tunnel crosses the high permeability watery stratum,the shield tail gap is easily filled by groundwater,which causes the common grouting material to be separated and the gelling material to be lost during the simultaneous grouting operation,so that the original water-to-gel ratio and other parameters occur.Great changes have a serious impact on the physical and mechanical properties and durability of the grouting ring after hardening.Therefore,the performance of the existing cement-based ordinary grouting slurry needs to be improved,and the water-resistant dispersibility is improved under the premise of ensuring the original performance,so as to obtain a cement-based anti-water dispersion synchronous injection with excellent work performance and low cost.Slurry.In view of the research and development status of synchronous grouting and water-resistance performance of shield tunnels,this paper intends to systematically study the anti-water-soil slurry in water-rich stratum of high-permeability in the groundwater environment through comprehensive research methods such as data investigation,theoretical analysis and laboratory test.The mechanism of water dispersibility is established,and the evaluation system of water-resistance dispersibility of slurry is established.The influence of different admixtures and their combinations on the water-resistance dispersibility of the slurry is revealed by laboratory tests,and the simultaneous grouting and water-resistance of shield tunnel in high-permeability and water-rich stratum is proposed.Sexual slurry ratio scheme.The main research results of this paper are as follows:1.Based on the research on the characteristics of synchronous grouting construction,a test device for testing the water-resistant dispersion performance of synchronous grouting slurry of shield is developed;2.HEMC(10W)can be used as an excellent anti-water dispersibility improving material for slurry,which can resist the dilution and erosion of water by increasing the shear stress and plastic viscosity of the slurry;3.With the increase of the dosage,the sodium bentonite after puffing for 24 h will weaken the flowability and late strength of the slurry,but it can improve the anti-dispersion performance and accelerate the gelation of the slurry;4.Hydroxyethyl methyl cellulose has a positive effect on improving the stability and water dispersibility of cement-based slurry,but it hinders the dissolution of gelled particles and the formation of hydration products,which delays the gelation time of the slurry;The bleed air effect causes the gel porosity to increase and the internal structure to be loose,thereby reducing the late strength value;5.Calcium formate has a certain weakening effect on the plastic viscosity and shear stress of the hydroxyethyl methyl cellulose modified slurry,but it can effectively reduce the initial setting time of the slurry and increase the compressive strength,which can be used as hydroxyethyl methyl group.Auxiliary agent for cellulose;6.The change of turbidity increment has obvious response with the dosage of flocculant,which can be roughly divided into four sections: insensitive zone,abrupt zone,gradual zone and gentle zone.Based on this,the water-dispersion performance requirements of synchronous grouting slurry were determined: turbidity<100NTU,PH<10,water-intensity ratio at different ages: 3d>80%,7d>80%,28d>80%;7.Based on the consideration of slurry fluidity and water dispersion resistance,the combination range of hydroxyethyl methylcellulose and calcium formate was determined,and the mixing ratio of hydroxyethyl methylcellulose modified water-resistant dispersion slurry was further proposed.Design method and test evaluation system. |
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