Study On Relationship Between Particle Size Density And Mixing Rate Of Overlaying Rock Layer

The non-pillar sublevel caving method is widely used in underground mining because of its simplestructure,safety and easy mechanization.Drawing under the overburden is the main cause of the big ore loss and dilution of this mining method.The particle size and density of the rock particles in the overburden are the main factors affecting the degree of rock incorporation.The reasonable size of the overlying rock and its density can reduce the rock mixing rate and improve the recovery of mineral resources.Therefore,it is of great practical significance to study the relationship between the particle size density of the overburden rock and the rock mixing rate.On the basis of summarizing the previous studies,the effect of particle size and density on mixing rate of rock was studied via the laboratory physical simulation experiment by selecting the overlying rock of different particle sizes and densities;based on the analysis of the response surface of the central composite experimental design,the influence of the interaction between the particle size and density of the rock particles on the rock mixing rate was studied,and combined with the theory of particle mechanics,the rule of intergranular force chain changing at the beginning and end of ore drawin was studied by using PFC numerical simulation experiment.The results show that the particle size and density of overburden have a significant effect on the mixing rate.The main results are as follows:1.Combining the actual parameters of the mine,the single-drift end drawing model was conducted and the physical simulation experiment was carried out.Twofactor and three-level orthogonal experiments were designed and completed.The orthogonal test table analysis of variance was used to analyze the test results It finds that the particle size of rock particles has a significant effect on the rock mixing rate.The relationship between particle size density and mixing rate of overburden rocks was found2.Based on the design of the central composite test,the response surface of the particle size and density of the overburden rock to the mixing rate of the rock is constructed.The interaction of the particle size and density of the rock and the relationship of the mixing rate of the rock are found to be nonlinear.3.The effect of particle size and density on the mixing rate of overburden rock was found based on the established response surface model.When the density value is in a certain range,increasing the particle size of the rock is beneficial to reduce the mixing rate of the rock.4.Based on the linear anti-rotational contact model,the PFC numerical simulation experiment was carried out.Using the released body obtained by the physical model experiment,the discrete element numerical simulation is performed on the mesoscopic parameter calibration.The Hertz contact theory was used to calculate the normal contact force between particles and the Mindlin-Deresiewicz contact theory to calculate the tangential contact force between particles.The change of the force chain between the particles before and after the ore mining was compared to obtain the particle size of the cover rock particles.And mechanical models of density changes.