| With the continuous development of underground engineering construction in recent years,the leakage problem has become the main problem that restricts the construction of underground engineering,especially in water-rich and geologically complex areas.Grouting method is commonly used in engineering to seal the water flow and strengthen the rock body.Rock fractures are concealed,and grouting in engineering is mostly empirical,making the theory of grouting slow to develop,especially in flowing water.In this paper,we study the process of diffusion of dynamic water grouting in rough fissures by combining model tests and numerical studies,and systematically analyze the diffusion law of slurry from the sealing mechanism of slurry,the numerical calculation method of diffusion and the change of fine observation parameters during diffusion.The main findings and results are as follows:(1)Based on the Barton curve,an indoor test model of the rough fracture below the top was established,and 16 sets of orthogonal tests were conducted to study the diffusion pattern of slurry in dynamic water for factors such as aperture width,water flow rate,grouting pressure and gelling time.The tests show that the diffusion patterns of slurry are mainly:near cross-shaped diffusion,near U-shaped diffusion,and near T-shaped diffusion.The degree of influence on the effect of slurry plugging is in descending order of dynamic water flow rate,fracture opening,gelling time and slurry pressure.As the values of dynamic water flow rate,fracture opening and gelling time increase,the plugging efficiency is gradually reduced.With the increase of grouting pressure,the water plugging efficiency increases,then decreases and then increates.The effect of dynamic water flow rate on the slurry diffusion distance is significant.At the end of grouting,there are four main final distribution states of slurry:successful plugging by dynamic water flow;partial plugging by boundary flushing;failed plugging by violent flushing;and ineffective plugging.And according to the above research results,the sealing mechanism of dynamic water injection slurry diffusion in rough cracks is obtained as follows:the slurry diffuses to the lateral boundary of the fissure in irregular shape;the slurry continues to diffuse to complete the filling of the rough bottom layer;the slurry diffuses and solidifies in the upper layer of the filling layer.(2)A numerical algorithm to describe the slurry diffusion process in moving water is proposed.Based on the existing experimental and theoretical research results,combined with the time stepping method,the calculation method of the diffusion distance and pressure spatial distribution of the slurry under two injection methods of grouting rate and grouting pressure is proposed,mainly considering the fracture opening,slurry viscosity,fracture width and dynamic water flow rate.The applicability of the algorithm was proven by the available data.The algorithm considers the scouring effect of water flow on slurry for the first time.This can provide improved accuracy of numerical calculations.(3)Numerical simulation is used to study the changes of fine observation parameters during slurry diffusion.The slurry diffusion pattern,slurry pressure,flow rate variation,and flow rate variation at the outlet section are studied for dynamic water flow rate,slurry injection pressure,fracture opening and slurry viscosity.When the water flow rate is large,the slurry is more volatile at the junction with both sides of the water flow.When the opening degree is larger,the slurry diffuses in a semicircle in the direction of downstream flow at the beginning and tends to a stable rectangle at the end.The slurry pressure is maximum at the grouting hole and decays in all directions,and decays more rapidly in the downstream direction.With the increase of grouting time,the pressure of slurry is gradually increasing.Under the same conditions,the higher the flow rate of water,the higher the pressure of slurry;the size of fracture opening and viscosity are inversely proportional to the size of slurry pressure.With the increase of time,the flow velocity of fluid is decreasing in the downstream direction.The fluid velocity at the lateral boundary increases gradually with time.The fluid flow velocity is proportional to both the grout pressure and the fracture opening,and inversely proportional to the viscosity of the slurry.After the shear slip of fracture occurs,the distribution of fracture opening will change and more throat areas will be produced.The pressure of the slurry will drop rapidly when passing through the throat area,which is more obvious near the grouting hole.The presence of the throat area will hinder the slurry diffusion in the later stage,especially in the reverse flow direction.The overall increase of water scour on both sides of the boundary after shear slip occurs. |
