Experimental Study On New Grouting Water-proof Material In Water-rich Sandy And Gravel Stratum

In urban underground engineering construction in China,water-rich sand and pebble strata are often encountered.This is a kind of loose coarse clastic accumulation stratum with large water content and often under pressure,uneven distribution of seepage voids,and easily distorted by disturbance,which brings great potential safety hazards to underground engineering construction.Grouting technology is an effective method to reinforce and stop water in strata.According to the past engineering experience,compared with single cement grouting material and cement-water glass double grouting material,sodium(calcium)bentonite grouting material has improved the water plugging effect and strength stability to a certain extent,but the excavation surface still has the problems of low seepage and early strength.Therefore,it is necessary to further improve the strength and impermeability of grout stone.In this paper,lithium-based bentonite is used instead of sodium-based bentonite,ordinary Portland cement and lithium-based bentonite are used as raw materials,and lithium-based bentonite grouting materials are prepared by mixing different ratios of sodium silicate and early strength agent.Specific research contents are as follows:(1)The single factor test was completed,and the performance parameters of sodium-based and lithium-based bentonite slurry were analyzed,and the performance advantages of lithium-based bentonite slurry were obtained.The stability of lithium-bentonite grout and the strength and impermeability of stone body are better than those of sodium-bentonite grouting material,and the greater the water-solid ratio,the more obvious the advantage is.(2)X-ray diffraction analysis was completed and the influence of early strength agent on the hydration products of slurry was obtained.Addition of early strength agent did not increase the types of hydration products of slurry.Addition of bauxite and sodium sulfate could increase the production of ettringite,and the effect of bauxite was better.Addition of triethanolamine and calcium chloride could increase the production of hydrated calcium silicate,and the effect of triethanolamine was better.(3)The modification experiments were completed,and the effects of early strength agent and compound early strength agent on slurry properties were obtained.Compared with other early strength agents,bauxite has the most obvious effect on increasing strength and decreasing permeability coefficient,and composite early strength agents can play a better early strength effect,especially the combination of bauxite and triethanolamine has the most obvious effect on increasing strength.(4)The orthogonal experiment was completed,and the influence of each factor on the performance index of slurry and its variation law were obtained.Each performance index of grouting is closely related to each other.When grouting to reinforce strata,the grouting formula with high strength of stone body should be selected as far as possible on the basis of meeting the requirements of impermeability.When grouting to prevent seepage and stop water,the grouting formula with high impermeability should be selected as far as possible on the basis of meeting the requirements of strength and so on.