| The formation of water containing fine sand is one of the geological conditions which is difficult to be controlled in the construction of underground engineering.It has abundant water content,poor self-stability and low cement strength.If it is not handled properly during the construction,it is very easy to cause serious safety accidents such as water gushing and sand break.The pore of fine sand stratum is small.When grouting is used to reinforce it,the slurry used is required to have strong permeability.The common chemical slurry such as water glass is not ideal for the reinforcement effect of the stratum.In order to strengthen such stratum effectively,it is urgent to develop high permeability slurry and study its grouting reinforcement mechanism.Based on this,this paper took the silty sand stratum of the Nanzhonghuanjie Station of Taiyuan Metro Line 2 as the research object,and used acrylate slurry for grouting reinforcement of the stratum.Aiming at its applicability,reinforcement mechanism and other problems,this paper comprehensively used theoretical analysis and numerical simulation calculation,combined with large-scale simulation test,optimizes the acrylate material,and analyzed the grouting reinforcement mechanism of the silty sand stratum Research.The main research contents and conclusions were as follows:(1)Through laboratory tests,the influence of different curing agent ratio on the diffusion range of acrylate slurry in fine sand was analyzed.The experimental results showed that the higher proportion of curing agent in the slurry is,the shorter gel time is,the smaller diffusion range of the slurry is,and the higher strength of the stone body.Under the condition of meeting the engineering reinforcement requirement,the maximum penetration of the gel in the fine sand stratum is 25 min.(2)A comprehensive test with 2 factors and 5 levels was carried out to study the influence of sand moisture content and mortar ratio on compressive and tensile strength of samples.The results show that when the moisture content of sand is less than 8% and the mortar ratio exceeds 6:1,the slurry is basically unable to gel in the soil;when the mortar ratio is in the range of 4:1 to 6:1,the compressive strength and tensile strength of the sample decrease with the increase of soil moisture content.By fitting the test data,the quantitative relationship between the compressive and tensile strength of samples and the moisture content of sand and mortar ratio was obtained.(3)The microscopic structure of samples with different moisture content was observed by microscope.The influence of water on the strength of samples was analyzed.The results showed that: 1)Combined with the lubrication effect of water film.2)Free water was involved in the polymerization of slurry,so that the strength of gel decreased.3)The vapor-liquid two phase transformation of residual water resulted in pore structure in the structure,and the strength of samples decreased accordingly.(4)Taking the silty fine sand stratum of Nanzhonghuanjie station as the research object,the finite difference software was used for grouting numerical simulation calculation,and the dynamic change characteristics of seepage velocity at different nodes were obtained.By comparing with the splitting grouting theory,the diffusion reinforcement mechanism of acrylic ester slurry in silty fine sand stratum was further revealed.(5)Through the simulated grouting test,the strength of the grouting stone body was tested,and the distribution law of the grouting stone body strength was obtained as follows:the strength of the stone body at the boundary of the model box is high,and the strength of the stone body in other areas is relatively low.The relationship between the strength of grouting stone body and the diffusion range and depth of slurry along the splitting channel is fitted,which conforms to parabolic equation.Combined with the characteristics of acrylate slurry,the strength distribution of grouting stones is mainly affected by the impermeable boundary and gravity. |
PDF Full Text Request