| At present,the mine filling mainly adopts the pipeline gravity transportation mode,and the filling pipeline is damaged due to the erosion wear of slurry and the sliding wear of solid particles on the pipe wall.In order to solve the technical problem that the serious wear of mine filling pipeline affects the stability of filling system,this paper firstly takes Canadian a mine,b mine and c mine as engineering background,and starts with the basic concept of slurry rheology and its influence mechanism,respectively through slump test,viscosity meter test and rheometer test three kinds of test,mastered its rheological characteristics under the influence of temperature;The thermodynamic characteristics of each ore filling slurry and its change law in the process of transportation are obtained by using the measured data,theoretical analysis and numerical simulation.Based on the wear and tear characteristics of filling pipeline in Canadian a mine,the influencing factors of pipeline wear and the wear mechanism of pipeline are analyzed,the wear test device of slurry roller is designed,and the wear law is obtained.The wear law of slurry to pipeline was quantitatively studied by numerical simulation.Finally,the risk assessment system of pipeline wear is established by mathematical method and applied.As follows:(1)Starting from the summary and combing of the basic concepts of slurry rheology,the mechanism of viscosity and yield stress,the influence mechanism of temperature on rheological properties and the development mechanism of rheological parameters are analyzed theoretically,which lays a foundation for the following research on the influence of temperature on rheological properties of filling slurry.The relationship between two types of slump(dimensionless)and yield stress(dimensionless)is revealed through cone and cylinder slump tests.Take Mine A,Mine B and Mine C in Canadian as the research project,The yield stress and consistency coefficient of slurry at different temperatures were obtained by internal rotary cylinder viscometer.The shear stressshear rate curves of a ore slurry at different temperatures were obtained by rotating rheometer.It can be seen that with the increase of shear rate,the shear stress will increase until the maximum value is reached.With the increase of the temperature of the filling slurry,the shear stress decreases at the same shear rate,which can be described by polynomial function.At the same shear rate,the shear stress increases with the increase of slurry mass fraction.(2)By introducing Arrhenius equation in thermodynamics,the relationship between temperature and viscosity of slurry was studied.on this basis,a new rheological model (?) was obtained by introducing temperature function,which laid a foundation for further study of thermodynamic characteristics such as activation energy of slurry and numerical simulation.Through the establishment of numerical simulation model,three simulation schemes were designed,and the effects of solid mass fraction,viscous heating,thermal conductivity,consistency coefficient,mass flow rate,specific heat capacity,yield stress and other variables on the temperature rise phenomenon during slurry transportation along the pipeline were analyzed respectively.the results show that the thermal conductivity has the most obvious effect on the temperature rise phenomenon.Taking mine A as the research object,the distribution law of temperature rise along the filling pipeline is obtained by numerical simulation method when slurry with different mass fraction is transported in pipe.The results show that with the increase of the mass fraction,the temperature rise of the slurry will increase when flowing through the unit distance,and the temperature rise will suddenly increase at the elbow at the bottom of the vertical pipe.the reason is that the potential energy is continuously converted into kinetic energy when the slurry falls from the vertical section,and the kinetic energy is converted into thermal energy when the slurry flow direction changes sharply at the elbow of the vertical section due to the dense collision between particles and the inner wall of the pipe and between particles,so the temperature rise curve has a small peak.(3)The roller with proper size and the matching test device are designed.the wear effect of the filling slurry and the pipe wall can be quantitatively studied by using the device.By designing four schemes,the wear effect of solid particles in slurry with different material ratios on the pipe wall was quantitatively studied,and the wear effect of slurry on the pipe wall was also studied when the mine water and ordinary water were used respectively.The test results show that the abrasion of the cylinder wall caused by tailings is relatively serious when the slurry concentration is 80 % and the rotating speed of the cylinder is kept at 1.5m / s;When 50 % of the solid phase is changed from sand to tailings,the class I wear rate will increase by 17 % and the class II wear rate will increase by 15.7 %.When 100 % tailings and 100 % sand were used respectively,the wear rate of the former was 11.1 % and 7 % higher than that of the latter.The results show that the wear rate of the former is 2.4 % higher than that of the latter,and the wear rate of the latter is 4.5 % higher than that of the latter.This shows that the wear of the cylinder wall is not obviously different when the other conditions are the same.(4)Field measurements show that the maximum wear occurs at the bottom of the pipe and decreases gradually along the circumference.The new wear model (?) is used to simulate this rule,which shows that slurry transport in pipeline is not homogeneous.Field measurements show that the maximum wear occurs at the bottom of the pipe and decreases gradually along the circumference.The new wear model is used to simulate this rule,which shows that slurry transport in pipeline is not homogeneous.There is a certain relative error between the numerical simulation and the field measured wear rate.the average relative error of the simulation results at 3800 level and 6400 level is 86.9 % and 36.9 % respectively,but the relative error at the bottom of the pipeline is 17.4 % and 4.3 %,respectively,which indicates that the prediction accuracy of the model is acceptable.Taguchi analysis shows that the flow rate has the greatest impact on the pipeline wear,followed by sand content and solid content.The influence of high solid phase and high sand content on wear is very small,because the gap between particles is small,which limits its lateral movement,and because the force between particles increases,so the viscosity also increases correspondingly;High viscosity fluids have less effect on wear than low viscosity fluids.When the particle concentration is high,the influence of drag force and other resistance on the particle trajectory will cause pipeline wear.(5)On the premise of mastering the factors and mechanism of wear,12 factors were selected as evaluation indexes,specifically: weighted average particle size of solid particles in slurry,solid particle shape,slurry density,slurry corrosion,slurry flow velocity,pipeline wear resistance,pipeline wall thickness,internal diameter of pipeline,borehole deviation rate,filling doubling line,pipeline installation quality,pipeline change degree.based on subjective and objective weight calculation method and variable fuzzy theory,a coupling model for comprehensive evaluation of pipeline wear risk was established.On the basis of field investigation and historical data analysis,the wear risk of filling pipelines in a,b and c mines in Canada is evaluated by using the established wear risk assessment model.the results show that the wear risk of a mine is grade ii,that of b mine and c mine is grade iii,but the wear risk of pipelines in c mine is higher.the conclusion can provide some guidance for the practice of mines.Through comprehensive comparison of extension wear risk assessment model,unascertained measure wear risk assessment model,fuzzy comprehensive risk assessment model,subjective and objective combination weight and variable fuzzy wear risk assessment model,we can see that this model has the same assessment results as other three types of models,which shows that using subjective and objective weight and variable fuzzy theory to establish the coupling model of pipeline wear risk comprehensive assessment is feasible,effective and scientific.compared with other models,this model has the following advantages The accuracy of the model can be verified by adjusting the parameters,which shows that the model can be changed according to the engineering practice,so that the evaluation results are more reliable. |
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