Numerical Simulation Study On Rapid Plugging Of Coarse Aggregate Grouting In Subway Water Inrush Rescue

Water hazards caused by groundwater surges frequently occur during subway construction,and grouting water blocking technology is an important way to control water hazards.With traditional grouting methods,in the case of large water influx,the grout is easily washed away by the water flow,resulting in poor curing effect of the grouting material and blocking in time,resulting in a waste of grout and increasing the time required for emergency construction.In this paper,through a combination of numerical simulation experiment and theory,the rapid plugging mechanism of coarse aggregate grouting in moving water pipelines is studied,and a surging pipe model of subway connecting channel is established,and the hydraulic pressure in the pipeline at each stage of aggregate grouting is established.Changes,movement trajectories of aggregate particles,changes in water pressure on both sides of the aggregate accumulation body after reaching a steady state,changes in grout pressure,and grout diffusion paths are analyzed to study the plugging mechanism of aggregate grouting.The main research contents and results are as follows:(1)Based on the data collected at the rescue site of the water inrush accident in the subway connecting channel,the dynamic water flow pipeline model was established according to the parameters of the actual project,and the relevant literature was consulted to establish the numerical simulation test of the two stages of aggregate infusion and grouting and plugging.The motion control equation of aggregate particles,the boundary condition equation of the effective water blocking section formed by the sedimentation and accumulation of aggregate particles,the mechanical model of the slurry diffusion in the flowing water pipeline,the two factors of the slurry in the porous medium(the pores between the particles in the aggregate accumulation)The phase flow permeation diffusion equation provides calculation basis for subsequent numerical simulation experiments.(2)Carry out the numerical simulation test of the aggregate pouring stage,analyze the movement trajectory and speed change of the aggregate particles,and the water pressure change in the pipeline,and find that the aggregate particles migrate under the combined action of gravity and hydraulic transport force.Settling and finally accumulating to form an effective water blocking section;after the aggregate accumulation is capped to form an effective water blocking section,there is an obvious water pressure difference on both sides of the aggregate accumulation,which is beneficial for the slurry to flow between the aggregate particles in the subsequent grouting stage the process of permeation and diffusion.(3)After the aggregate particles are piled up and capped and an effective water blocking section is formed,a numerical simulation test of grouting and plugging is performed on the aggregate accumulation body.The trajectory of the grout diffusion path,the change of grout pressure,the change of water flow through the internal pores of the aggregate accumulation body before and after grouting,the change of the porosity of the grout in the pores of consolidation and plugging,etc.were studied and analyzed,and the grouting seal was obtained.The plugging mainly includes two processes of mutual penetration of the two-phase flow of slurry and water,draining the water from the pores and plugging the pores under the action of the self-consolidation of the slurry.And the grouting pressure is an important factor affecting the plugging effect.(4)Combining actual engineering and comparing the actual use of chemical grouting water shutoff technology in the emergency treatment of water inrush accidents in subway connecting passages,the aggregate grouting water shutoff technology has natural advantages in terms of material cost,emergency construction preparations,and plugging effects.The change of the porosity of aggregate accumulation before and after grouting is put forward to judge the grouting effect.(5)In view of the advantages of aggregate grouting and plugging technology in the treatment of water hazards in moving water and combining with actual projects,this paper discusses whether aggregate grouting and water blocking technology can be used for water blocking and reinforcement in advance in areas where water hazards may occur.This paper contains 36 figures,8 tables,and 73 references.