| At present,tailings and mined-out areas are potential safety hazards that exist in metal mines in China.How to deal with them safely and effectively is an urgent matter at present.However,when filling the tailings cement slurry into the goaf through the pipeline,the transport characteristics of the slurry in the pipeline are directly related to the design and construction of the entire filling system.Therefore,it is especially important to study the pipeline transportation characteristics of full tailings cement slurry.Based on this paper,taking the two-phase flow theory and the pipeline transportation theory as the starting point,combined with the slurry rheology test and the loop tube test,the numerical simulation and analysis of the pipeline transportation are carried out using numerical software.Finally,the slurry movement in the pipe is studied and analyzed.And calculation of flow resistance.The main research contents of the paper are as follows:(1)Based on the complexity of the full tailings cement slurry pipeline transportation and the limitations of theoretical research,from the basic parameters of the slurry,the rheological model and its properties,the two-phase flow slurry flow characteristics,The theory of pipeline resistance calculation is expounded and analyzed,which provides technical parameters for the numerical simulation of the full tailings cement slurry pipeline transportation,and provides theoretical support and technical basis for the subsequent related work of this paper.(2)In order to study the rheological properties of the full tailings cement slurry,a series of physical and chemical properties tests(including density,natural angle of repose,water content,XRD diffraction,tailings grading,etc.)of filling materials were carried out in the laboratory The rheological test results show that the full tailings have stable physicochemical properties,good tailings gradation,and uneven coefficient C_u=23.54>5.As the main filling material,it can meet the mechanical strength requirements and transport performance requirements of cemented filling;use MCR102.Advanced rheometer for different ratios(grit ratio:1:4,1:6,1:10,1:20,mass concentration:73%,74%,75%,76%,77%,78%).The full tailings cemented slurry was subjected to rheological tests.During the experiment,the slurry showed shear thinning characteristics.By analyzing the complete rheological curve,the rheological process can be divided into three stages;and the slurry is more in line with.The rheological model of yielding pseudoplastic body,on the basis of which,the influence of rheological parameters was further studied,that is,the yield stress and viscosity both showed a composite exponential function with the increase of volume concentration and the decrease of lime-sand ratio.(3)In order to explore the transportation status and transportation law of cement slurry in the transportation pipeline,through the different ratios(lime-sand ratio:1:4,1:6,1:10,mass concentration:71%,73%,75%)of the cement slurry was subjected to the loop test.It was calculated that the system flow rate in the test was 44～46m~3/h,the flow rate was 1.6m/s,and the temperature would rise by 1～2℃;the resistance loss of the horizontal straight pipe along the way was 1840.14～8015.14Pa/m,the bend is 2024.62～10118.00Pa/m,showing that with the increase of the cement slurry mass concentration and the decrease of the lime-sand ratio,the resistance loss along the path will gradually increase.According to rheology,theoretically reconstruct the formula for calculating the resistance along the pipeline for the cement slurry,and compare this formula with the Jinchuan formula,the Soviet formula and the resistance along the loop.The derivation formula calculated in this paper is closer to the actual measured value of the loop.The difference between the Jinchuan formula and the Soviet formula and the actual measured value is large.(4)In order to accurately describe the flow field velocity distribution characteristics and pressure distribution characteristics of cement slurry in the pipeline,the numerical simulation analysis of the lime-sand ratio of 1:4 and the mass concentration of 73%was carried out using COMSOL Multiphysics numerical software,and the straight pipe.There is a gradient change in the flow rate and pressure of the elbow,where the maximum flow rate is located at the center of the axis,the closer to the pipe wall,the smaller the flow rate;and the gradient of the flow rate outside the bend is more obvious than the inside;and the pressure and flow rate have the same characteristics;straight.The difference in resistance loss between the pipe and the bent pipe is small,and the resistance loss of the bent pipe is 1.06 times that of the straight pipe section,which is in accordance with the laws of fluid mechanics.Compared with the resistance along the loop test,the error between the two is small,and the numerical simulation results have a certain guiding significance. |
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