Experimental Study And Numerical Simulation On Stacking Of Binary Particle Mixtures

It is an inevitable trend for the development of ecological building materials to replace the increasingly shortage of natural sand with machine-made sand.In order to meet the practical requirements,it is necessary to detect the quality of machine-made sand.Gradation is one of the important parameters of quality management of machine-made sand,and currently there is no effective method to predict the overall gradation composition of sand pile.In addition,because mechanized sand is a kind of granular material,particle separation will occur in the stacking process.Relevant studies also show that the particle size composition,shape and other parameters are correlated with the degree of particle segregation,which provides the feasibility to determine the particle size composition and shape parameters of sand according to the particle segregation phenomenon.Therefore this study through from a simple binary particle mixture system of particles of the rules and irregular particles in 3D stacking test,studied the distribution of deposit and characteristics of segregation and the particle mixture deposit particle size composition and particle distribution of contact between particles on the surface for the next step through deposit deposit distribution to determine the overall grading research work provides experimental basis.The main conclusions and results are as follows:(1)For the nearly spherical particles and the irregular particles,the overall characteristic distribution of the two kinds of particles with different shapes is basically the same.The coarse particles are collected at the bottom of the heap,and the fine particles are collected at the top of the heap.In the middle region of the heap surface,the coarse particles and the fine particles are evenly mixed.With the increase of initial coarse particle content,the aggregate area of coarse particles increases and that of fine particles decreases.The accumulation diameter increases with the increase of coarse particle content,while the accumulation height decreases with the increase of coarse particle content.(2)The distribution rules of the near-spherical three-dimensional accumulation body and the irregular three-dimensional accumulation body are basically the same.After the accumulation,the mixtures with different coarse particle contents will produce the corresponding distribution patterns on the surface and inside of the accumulation body.The standard deviation of the near-spherical particles is smaller than that of the non-spherical particles.The content of coarse particles in the whole reactor is larger than that in the center of the reactor.On the surface of the accumulation body,the content of coarse particles presents a vertical distribution along the height of the accumulation body,and the content of coarse particles in the lower part of the accumulation body is larger than that in the upper part.The content of particles at the local position inside the particle is consistent with that at the beginning of mixing,and each position inside the particle has the rule of symmetry along the middle line of the reactor.(3)By using numerical image technology,the concentration of coarse particles on the surface of the reactor is identified and the segregation coefficient is defined to evaluate the degree of particle separation.The overall segregation coefficient of the reactor surface decreases with the increase of coarse particle content,and the lower part of the reactor surface changes the most with the initial coarse particle content.As for the internal segregation law of three-dimensional pile,the nearly spherical three-dimensional pile is basically the same as the irregular three-dimensional pile.In the interior of particle accumulation,the global and local segregation coefficients do not change with the change of initial coarse particles,and maintain a stable state.(4)The quasi-two-dimensional stacking test and numerical simulation were carried out for two-dimensional near-spherical particles.By comparing the overall particle distribution and segregation coefficient,the numerical simulation results were basically consistent with the experimental results.Then,the coordination number of the accumulation body was calculated by the numerical simulation results,and the coordination number decreased with the increase of coarse particle content.