Experimental Study On The Diffusion Law Of Silica-sol Grouting In Pore-fracture Dual Media Network

As a practical and wide application engineering technology,grouting technology has been widely used in foundation treatment,rock reinforcement and fracture sealing.The existing grouting theory mostly regards the injected media as porous media or fracture network media,which is different from the real situation of rock body,which is mostly in the state of coexistence of pore media and fracture media.Therefore,it is of great academic value and broad application prospect to carry out the study of grouting diffusion law under the condition of fracture-pore dual media,improve the theory of rock grouting,and lay the foundation for improving the design of grouting process.In this paper,the combination of indoor model test and numerical simulation is used to establish a visualized grouting test platform by using silica solute as the grouting slurry,and the experimental study of single plate fracture and porefracture dual media grouting is carried out to analyze the influence law of each test factor on the slurry diffusion.And use COMSOL numerical simulation software to carry out numerical simulation of pore-fracture dual media grouting,the main research results and contents are as follows:(1)The gelling time of silica sol was measured by the viscometer method to study the effects of different ratios,different catalyst(Na Cl solution)concentrations and different temperatures on the gelling time of silica sol.The results showed that the larger the volume ratio of silica sol to Na Cl solution,the shorter the gelling time;the larger the concentration of Na Cl solution,the shorter the gelling time;the lower the temperature,the longer the gelling time.And according to the test results,the ratio of silica sol to Na Cl solution required for the subsequent test was determined as 4:1,and the silica sol gelling time curve was fitted.(2)Under the condition of single plate fracture,the grouting results were classified into "completely sealed" and "not completely sealed" according to the slurry sealing results.The slurry diffusion pattern is divided into three categories: "symmetric diffusion","U-shaped diffusion" and "comet diffusion".It is found that the slurry diffusion distance along the Y-axis and X-axis negative direction is smaller as the fracture opening and inclination angle increase,and the slurry diffusion rate in a straight fracture is completely different from that in a fracture with inclination angle.When the fracture is straight,the diffusion distance of slurry along Xaxis negative direction and Y-axis direction increases linearly with time,and then the diffusion rate of slurry decreases slowly with time.When the fracture exists in inclination,the slurry diffusion rate first decreases,then increases,and finally decreases again.the nodes of change of slurry diffusion rate in X-axis negative direction and Y-axis direction are basically the same as the nodes of change of rapid growth of slurry viscosity.(3)Through the pore-fracture dual media network grouting test,it is found that the slurry diffusion in the pore-fracture dual media will occur with the bias flow effect,and the slurry diffuses farther in the fracture with larger width,indicating that the slurry enters the fracture with larger width preferentially.While the slurry flows along the fracture channel,it continuously penetrates and diffuses into the pore media,and strong material exchange occurs at the boundary of fracture flow and pore flow,and a solidified whole is formed after silica-sol gelation.The slurry diffusion distance along the negative direction of X-axis decreases with the increase of double media inclination,and decreases with the increase of media thickness.The diffusion rate of the slurry when the double media is flat is very different from that when the double media is inclined.When the double media is straight,the slurry diffusion rate in the negative direction of the X-axis increases first and then tends to level off with time.When the dual media exists at an angle of inclination,the slurry diffusion rate first decreases with time,and then increases after a period of time,and then decreases again.(4)According to the experimental results of pore-fracture dual media model,the numerical simulation software is used to further verify the partial flow effect of slurry diffusion in the pore-fracture dual media,the slurry diffusion rate in the fracture with large width is larger than that in the fracture with small width,and the presence of pore-fracture dual media slows down the flow rate of slurry in the fracture channel.The laws of grouting pressure and seepage pressure in the pore-fracture dual media were further studied,and the grouting pressure and seepage pressure increased with the decrease of void ratio in the pore-fracture dual media.