| With the gradual transfer of underground engineering construction such as mines and tunnels to dissolution rock areas with extremely complex hydrogeological conditions,the water inrush disaster encountered during construction is one of the most prominent problems that threaten the safety of engineering construction.Grouting technology is an effective method to manage water inrush disasters and has been vigorously promoted and applied.It has important theoretical and practical significance to study the grouting diffusion law and water plugging mechanism of rock fractures under flowing water conditions.By combining theoretical derivation,model test and numerical simulation,the diffusion law of slurry in inclined fracture under flowing water condition is studied.The process and mechanism of grouting water plugging were systematically analyzed.The findings were as follows:(1)According to the equilibrium conditions of the slurry micro element,the diffusion model of the slurry in inclined fracture with flowing water conditions is established,and the relationship between the fracture dip angle,the grouting pressure and the water velocity on the slurry diffusion distance is analyzed.Based on potential flow superposition principle,the flow network equation of the slurry in the inclined plane under flowing water conditions is deduced,and the characteristics of the slurry flow trace are obtained.The results show that with the increase of fracture dip angle,the self-weight effect of slurry is more obvious,which is beneficial to the retention of slurry in the fracture.There is a limit distance of slurry diffusion in the inverse water direction.(2)Taking the actual operation condition as the prototype,based on the similarity principle,a three-dimensional visual inclined fracture dynamic water injection grouting model test platform is independently designed and developed,which is mainly composed of variable inclination fracture simulation system,water source system,grouting system and data acquisition system.The grouting tests were carried out under the conditions of different fracture dip angle,water flow velocity and grouting rate,and the influence of various factors on slurry diffusion was obtained.(3)The test results show that the final slurry diffusion shape of the slurry in the inclined fracture is U-shaped under flowing water conditions,the final diffusion distance of the slurry along the slope direction is only related to the inclination angle of the fracture.After the slurry front moves toward the bottom of the slope to be stable,the slurry begins to gradually produce a slurry sedimentation zone downstream of the grouting hole.The pressure curve of seepage field is distributed hierarchically along the fracture slope direction,and the stepped seepage pressure field indicates good grouting effect.The grouting effect can be judged by monitoring the pressure field on site.(4)According to the prototype parameters of the test model,a numerical model of dynamic water injection grouting in inclined fractures is established based on the two-phase flow control equations,and the influence of various factors on the slurry diffusion form and fracture flow field is studied,the mechanism of slurry diffusion and water plugging is revealed.The research shows that the larger the inclination angle of the fracture,the easier it is for the slurry to diffuse and deposit to the bottom of the fracture slope,the larger the initial velocity of water,the longer the slurry diffusion distance along the water,and the higher the grouting rate,the shorter the time for the slurry to reach stable diffusion.The essence of grouting water plugging is the result of the slurry occupying the water passage and reducing the flow velocity of the flow field within the slurry diffusion range.The numerical simulation results of the slurry diffusion shape are in good agreement with the experimental results,which proves the reliability of the model test and the accuracy of the numerical simulation. |
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