Study On Slurry Diffusion Law And Grouting Plugging Mechanism Based On Turbulent Dilution

In recent years,China’s infrastructure construction has been vigorously promoted,and underground engineering has developed rapidly.However,China’s geological conditions are complex and changeable.In the process of underground engineering construction,geological disasters such as water inrush and collapse will inevitably occur.Among them,the water inrush disaster is particularly prominent,which can easily cause construction stagnation,property damage and even casualties.Grouting is the main method for prevention and control of water inrush disaster in underground engineering,which has significant advantages such as strong practicability and small environmental interference.However,in the face of large flow and high velocity water inrush,the grouting slurry is seriously diluted by water flow,the diffusion range and retention area are reduced,and the plugging mechanism is unknown,which makes it difficult for conventional grouting methods to meet the needs of dynamic water plugging.Therefore,the research on the grouting diffusion law and plugging mechanism under the conditions of large flow,high flow rate and turbulent flow water is the key scientific problem to be solved urgently in the treatment and safety construction of underground engineering water inrush.In this paper,aiming at the problem that the diffusion and migration mechanism of cement slurry under turbulent conditions is unknown,combined with numerical simulation,laboratory test and theoretical analysis,the influence of turbulent factors and grouting factors on the slurry diffusion dilution mode is studied.Based on this,a grouting plugging method under turbulent conditions is established,in order to provide guidance for the prevention and control of water inrush in underground engineering.The main research results are as follows:(1)The diffusion model of cement slurry under the condition of reverse turbulent flow is established:The difference of slurry diffusion under laminar flow and turbulent flow is compared and analyzed.Considering the mixing and dilution effect of slurry and environmental water flow under turbulent flow,a cement slurry diffusion model under reverse turbulent flow is proposed based on jet mechanics theory.(2)The law of grouting diffusion under the condition of reverse turbulent flow is studied by numerical simulation:For the reverse turbulent flow grouting model,COMSOL Multiphysics numerical software and large eddy simulation method are used to establish a three-dimensional grouting model.The difference of slurry diffusion effect between laminar flow model and turbulent flow model under the same working condition is compared and analyzed.The variation characteristics of slurry diffusion under different slurry velocity,turbulent flow velocity and grouting pipe diameter were studied.The diffusion morphology,distance,velocity distribution and concentration change of cement slurry under turbulent flow conditions are systematically analyzed.(3)The experiment of slurry diffusion law under visual turbulent flow conditions was carried out.The grouting simulation test system under visual turbulent flow was designed and developed independently.The system can meet the study of slurry diffusion mechanism under different test conditions such as grouting rate,turbulent flow velocity and slurry water cement ratio.The primary and secondary relationships among the influencing factors were analyzed by indoor simulation tests.The particle image velocimetry(PIV)is used to study the variation of the flow field in the channel during the grouting process and the mixing and dilution process of the slurry.(4)The grouting plugging mechanism under the condition of reverse turbulent flow is revealed.According to the action law of various influencing factors in numerical simulation and laboratory test,the empirical formula for calculating the slurry diffusion distance considering the influence of turbulent flow is established.Considering the wall effect,the empirical formula is modified,and the final slurry diffusion formula is obtained.The corresponding engineering plugging method is proposed,and the plugging method is verified by numerical simulation,which provides guidance for engineering practice.