Grouting Diffusion And Numerical Simulation Of Electrolytic Manganese Slag-acrylate Solid-liquid Couplin

The electrolytic manganese slag library left over from history and the failure of anti-seepage in China have generally caused the pollution of adjacent water bodies.In-situ reconstruction of anti-seepage system is an efficient and economical way to prevent and reduce pollution.The development of new grouting anti-seepage materials and grouting control is the key to reconstruct the anti-seepage system.In this study,acrylate grouting materials were prepared by two-step method.The impermeability,compressive properties and aging resistance of electrolytic manganese slag-based cementitious materials were investigated to reveal the anti-seepage mechanism of cementitious materials.The mechanical properties of electrolytic manganese slag soil were studied by discrete element model test.The solid-liquid coupling grouting model of electrolytic manganese slag-acrylate was established to explore the influence of grouting process on grouting diffusion.The model was solved by discrete element（EDEM）combined with finite element（FLUENT）coupling calculation method to obtain the best grouting nozzle flow channel structure to grouting pressure.The reliability of the numerical simulation model of grouting diffusion is verified and the model is optimized on the self-built visual three-dimensional grouting test platform.The specific research content is as follows:（1）Using sodium acrylate,sodium hydroxide,crosslinking agent N,N,-methylene diacrylamide,triethanolamine,potassium persulfate,silicon powder as raw materials,electrolytic manganese slag-based adhesive solidified body with multi-crosslinked network structure was prepared by two-step method.The results of compressive test,impermeability test and anti-aging test show that when the content of acrylate salt is40%,the solidified body of electrolytic manganese slag-based adhesive has the best compressive performance（strength 2.78 MPa）,which is 12.3 times and 2.5 times higher than the compressive strength of electrolytic manganese slag and sodium polyacrylate solidified body.It has good impermeability(impermeability coefficient 1.318×10^-8cm/s),which is 7.6 times higher than that of type I impermeability coefficient 1×10^-7cm/s in JCT 2037-2010 standard of acrylate grouting material.It has good anti-aging performance（corrosion resistance coefficient 0.85）,which is equivalent to the corrosion resistance coefficient 0.80 of concrete.The microscopic analysis results show that the positively charged cations such as Mn²⁺,Fe³⁺and Al³⁺in the electrolytic manganese slag are combined with the anionic group-COO-in the acrylic acid through the coordination bond to form a multi-crosslinked structure.The binding force between the molecular chains is enhanced to make the surface of the solidified body more dense and thick,and the impermeability and anti-aging properties are better.At the same time,the rod-like substance Ca SO₄ in the electrolytic manganese slag is used as the skeleton support to make the solidified body of the composite adhesive have better mechanical properties.（2）Based on the Hertz-Mindlin with JKR contact model,the discrete element simulation model of electrolytic manganese slag was constructed.Firstly,the basic physical parameters such as density,water content and particle size distribution of electrolytic manganese slag were obtained by measuring method.The stacking angle of electrolytic manganese slag was 36.72°measured by self-made stacking angle test device.Secondly,according to the basic physical parameters and the results of Box-Behnken test,the second-order linear regression equation of stacking angle and variable contact mechanical parameters（static friction coefficient（A）,dynamic friction coefficient（B）,surface energy JKR（C）,recovery coefficient（D））was established by Design Expert software.The significance order of the influence of various mechanical parameters on the stacking angle was obtained by the variance analysis of the quadratic equation model of the stacking angle Box-Behnken test,which was surface energy JKR（C）>recovery coefficient（D）>dynamic friction coefficient（B）>static friction coefficient（A）.By solving the inequality group composed of objective function and constraint conditions,the optimal solution of mechanical parameters is obtained when the stacking angle is 36.72°.The recovery coefficient is 0.6,the JKR surface energy is0.169 J/m²,the dynamic friction coefficient is 0.165,and the static friction coefficient is 0.745.Finally,the discrete element mechanical model of electrolytic manganese slag was constructed by basic physical parameters and mechanical parameters.（3）The numerical simulation model of grouting diffusion under the solid-liquid coupling of new grouting material and electrolytic manganese slag soil is established.The EDEM-FLUENT two-way coupling method is used to calculate and explore the influence of grouting process on grouting diffusion.The numerical results show that the nozzle and grouting pressure have significant influence on grouting diffusion.Among them,the curved nozzle has a farther diffusion distance than the countersunk nozzle and the inverted cone nozzle.This is because the curved nozzle structure has a smoother flow channel structure and the slurry has the least energy loss in the diffusion process;when the injection pressure is too small（20MPa）,the range of slurry action is large,the pressure dissipates slowly in the electrolytic manganese slag medium,and the macroscopic performance is that the injection distance is large,as the pressure gradually increases,the spraying distance gradually shows a gentle trend.（4）The test results and numerical simulation results on the indoor three-dimensional visual grouting test platform show that the error fluctuation range of the grouting test results and the numerical simulation results is in the range of1.1%to7.7%,less than±10%,indicating that the numerical simulation results are reliable.The reason for the error:First,the particle model of the electrolytic manganese slag soil is simplified during the simulation grouting process,which is different from the actual soil particles;second,the numerical simulation process of grouting does not consider the influence of viscosity and chemical adsorption of grouting slurry in electrolytic manganese slag soil on slurry diffusion.