Research On Diffusion Law Of Grouting With Flowing Groundwater In Rough Fracture

Under the influence of complex hydrogeological conditions,water disasters have become one of the geological disasters in underground engineering such as mines and tunnels,which seriously restricts the safety construction and development of underground engineering.As an effective reinforcement and sealing technology,grouting has been widely applied in the enhancement of rock mass and prevent the groundwater inrush.The study of grouting diffusion under flowing water has important theoretical significance and engineering application value for perfecting the grouting theory and improving the sealing efficiency.In this paper,analytical and numerical modeling are combined to study the diffusion of grout in fracture and sealing efficiency at different roughness under flowing water.The coupling effect of grout and rock is systematically analyzed.(1)The process of grout diffusion under flowing water is analyzed according to the flow state of groundwater and the flow pattern of grout.According to the equilibrium condition of the micro-unit of the grout,the diffusion equation of grout under flowing water was established.The formulas for calculating the diffusion distance from the direction of upstream and downstream were obtained,which were consistent with the experimental results.The evolution curve of the grout diffusion distance from time was obtained based on the grout diffusion equation,and the grout diffusion distance was analyzed in different directions.(2)Based on the fractional Brownian motion and midpoint displacement method,a model of the rough fracture was established.The fractal theory was used to quantitatively characterize the roughness of the fracture.According to the governing equation of fluid dynamics and the constitutive equation of grout,a 3D numerical model of grouting under flowing water considering fracture roughness was established by using the level set method.According to the roughness of fracture,viscosity of grout,grouting pressure and water flow speed,the orthogonal test scheme was designed.(3)Based on the orthogonal test results,the formula for sealing efficiency was established according to the diffusion area of grout,and the area ratio of each group was calculated.The sealing efficiency and influencing factors were analyzed by range analysis and variance analysis.The results show that the water flow speed has the greatest influence on the sealing efficiency,followed by the grouting velocity,and the roughness and slurry viscosity have less influence.(4)By using the control variables,the influencing factors of the grout diffusion are analyzed,and the shape and pressure distribution are obtained.The results show that the grout diffusion shape is round in hydrostatic,and the grout pressure distribute symmetrically and uniformly along the grouting holes.However,under dynamic water grouting,the grout diffusion is round in the initial stage,elliptical in the middle stage,and U-shaped in the late stage.The distribution of grout pressure is asymmetric under flowing water.(5)Based on ALE method,a numerical model of grouting with grout-rock coupling effect was established.The distribution of the grout flow field and the stress field of the surrounding rock mass and their coupling effect in the roughness fracture are studied.The results show that the flow characteristics of grout and the distribution of rock mass stress field depend on the morphology of fracture.The grouting velocity and the viscosity of grout are the key factors affecting the distribution of the rock mass stress field.