DEM Research Of The Effects Of Non-Spherical Particles On The Collapse Characteristics Of Binary Granular Column

Movement of granular matter are widely exsit in nature,industry,and our daily life.Common geological hazard such as landslide,mud-rock flow,avalanche usually involves different shapes of particle,and these particles usually have different size and volume fraction.In the existing research involving this field,the simulation generally assumed that the particles are spherical particles with uniform particle size.However,particle size,shape and volume fraction,especially that of larger particles,obviously have an important influence on the motion rule of particles.Therefore,considering the volume fraction and shape of large particle in polydisperse granular column to investigate their impact on the movement characteristics of granular material have important theoretical and practical significance.Based on this,this paper adopts the typical collapse experiment of granular column on the plane,to explore the influence of the volume fraction of large particles and their shape parameters on the collapse characteristics of binary granular column respectively through laboratory experiment method and discrete element method.The main research contents and conclusions include:1.We select polyhedral particles as spherical large particles and glass beads as small particles in this paper,the even mixing between them and the different volume fractions of large particles is achieved by adding the mixtures into the container layer by layer according to their mass ratio,then,eleven groups of granular column collapse experiments with different volume fraction of large particle and same initial aspect ratio were carried out in laboratory,and the collapse process and final deposit geometry of granular columns was compared.2.Based on the experimental method and the empirical parameters used in relevant literatures,the parameters required for discrete element method were calibrated,large particles of the same shape as laboratory experiments are generated by multi-sphere method.Then,discrete element model of sphere-aspheric binary granular column was established.Through this model,the effects of the volume fraction of large particles on the average coordination number of large particles and the energy change during the collapse process were investigated.3.The results of the study on the content of non-spherical particles show that:(1)In the binary granular column mixtures of aspheric particles,the higher the volume fraction of non-spherical large particles,the longer the collapse duration of the granular column and the smaller the morphological change rate of the particle column(2)In the binary granular column mixtures of aspheric particles,when the volume fraction of spherical particle is low,there is almost no contact between large particles and effective interlock can not formed between them due to the small initial average coordination number of large particles,which lead to the change of volume fraction of large particle have a neglect effect on the final deposit geometry and the enengy change of granular column.When the volume fration of non-spherical large particle get higher,with the increase of large particles volume fraction,the interlock between large particles enhanced and the mobility of granular column decrease with the increase of average coordination number of large particles,which lead to higher final deposit height,shorter final run out distance,Lower peak normalized kinetic energy,smaller total normalized dissipation energy and longer collapse duration during granular column collapse.(3)When the volume fraction of large particles is above a certain value,the average coordination number of large particles basically does not change.However,due to the lubrication effect of small particles,the mobility of binary granular column is higher than that of pure nonspherical granular column.4.We adopts the random polyhedron generation method to generate a more real large particle shape that can control the aspect ratio in this paper.Then,the discrete element method was applied to investigated the effects of the change of particle aspect ratio under different large particle volume fraction on the collapse duration,collapse process,coordination number of large particles,final deposit geometry and energy dissipation of the granular column.The results prove that:(1)When the volume fraction of large particles is high,the longer the aspect ratio of large particles is,the longer the collapse duration of particle column is.(2)When the volume fraction of large particles is high,larger aspect ratio of large particles will increase the initial average coordination number of large particles and reduce particle moving ability,generate enhanced interlock between them,results in the decrease of particle column's mobility,lead to higher final deposit,shorter ran out distance and smaller normalized peak kinetic energy and normalized total dissipated energy.(3)Increasing the volume fraction of small particles can minimize the effect of the aspect ratio of large particle on the collapse property of the granular column.The conclusion of this paper can provide some references for studying the the movement process and the risk assessment of landslide and debris flow.