| After water inrush and flooding in coal mine,it is one of the important methods to cut off the hydraulic connection between water source and tunnel system by pouring aggregate to build water-blocking wall.This technology has stayed at the state of experience for a long time,and its internal mechanism is lack of systematic research.This research work is of great significance to improve the technical level of mine water disaster prevention and control.By means of theoretical analysis,similar simulation test,indoor grouting test,numerical simulation calculation and field engineering application,this paper studied the mechanism of aggregate pouring and grouting reinforcement in dynamic water tunnel,analyzed the action law of water blocking wall and surrounding rock,and explored the key technology and optimization method of water blocking wall construction.The main research results are as follows:(1)Considering the flow velocity,aggregate size,pathway roughness,slope,aggregate pouring speed and other factors,a visual experimental simulation system for hydrodynamic water-blocking was developed,which provides a foundation for the study of dynamic process.(2)Through the similar simulation test,the rules of aggregate migration and accumulation were found,the influence mechanism of main control factors on aggregate pouring effect is evaluated,and the significance of pathway wall roughness to increase the probability of roof connection was pointed out.The influence factors of hole spacing and number of boreholes were analyzed,and the feeding principle was put forward,which is from fine to coarse in normal pouring,combination of thickness and fine and upstream and downstream in top connection.The concepts of stress arch and piping were used to explain the mechanism of accumulation failure.(3)The migration equation of cement slurry in aggregate was established,and it was concluded that the aggregate particle size,time-varying and viscosity of slurry are the main influencing factors.Combined with indoor test,it was found that there is partition effect of slurry with the change of aggregate particle size,and it was verified that the fluidity and water resistance of slurry with water cement ratio of 0.7:1 ? 1:1 are both suitable for long-time grouting.(4)Based on the CFD-DEM coupling calculation model,the general process of aggregate migration and accumulation under water was simulated,and the evolution rules of velocity field and pressure field were obtained.The model of two pathway closure was established,and it is more reasonable to block one pathway first.The influence of dip angle on the accumulation law was simulated,and the conclusion was consistent with the theoretical prediction.(5)Based on Mindlin model,the stress state equation of water blocking wall was established,and the influence of water pressure in upstream water inlet and elastic modulus ratio between surrounding rock and wall on stress distribution of wall was analyzed.Numerical simulation was carried out with Flac3D,and it was concluded that the key reinforcement range is the accumulation area near the upstream water inlet.(6)Based on the criteria of hydraulic stability,initial setting time and flow energy,the prediction method of aggregate accumulation length was proposed.According to the spatial distribution of the flow in the process of closure,the estimation method of the velocity in the non-topping area of the pathway was proposed.Based on the matching principle of single hole filling capacity,estimated closure time and accumulation length,the calculation method of boreholes number was proposed.(7)Taking Shibajing coal mine as an example,this paper analyzed the key parameters of the construction scheme,and verified the effectiveness of the water blocking wall construction technology system through field test and technical optimization. |
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