Experimental Study On Macro And Micro Mechanical Properties Of Spherical Particulate Materials

The experiment and analysis of artificially prepared cemented soil close to loess particle size can provide reference for the general law of loess cementation characteristics.Based on the structural characteristics of loess,the macro triaxial test and micro nanoindentation test were carried out by using glass beads of 100 mesh,200 mesh and 325 mesh as skeleton particles and paraffin and polyethylene glycol as cementing materials.In the macroscopic test,skeleton particles and cementing materials were mixed with 60%,75% and 90% pore filling ratio to make triaxial specimens.The influences of confining pressure,pore filling ratio,particle size and cementing materials on the stress-strain relationship of specimens were investigated,and the following rules were obtained: the stress-strain curves of all specimens were softened,and their peak strength increased with the increase of confining pressure.The shear strength of polyethylene glycol samples is greater than that of paraffin samples.The shear strength of polyethylene glycol samples and paraffin samples with particle size of 200 mesh and 325 mesh increases with the increase of pore filling rate,while the shear strength of paraffin samples with particle size of 100 mesh increases first and then decreases with the increase of pore filling rate.The larger the particle size,the greater the shear strength of the sample.The cohesion of polyethylene glycol samples is significantly greater than that of paraffin samples.The larger the particle size,the greater the cohesion of the sample.The internal friction angle of each sample has little difference.The initial tangent elastic modulus of polyethylene glycol samples is larger than that of paraffin samples.Micro-test is to prepare samples with glass beads and cementing materials in a single layer,and carry out nano-indentation test on the "cementing units" in the samples.The influences of particle size,cementing materials and indentation depth on the elastic modulus and load-displacement curve of the samples are explored,in order to study the stress of eachskeleton particle in the macro samples,and the following rules are obtained: the elastic modulus of the samples decreases with the increase of indentation depth.The elastic modulus of polyethylene glycol samples is greater than that of paraffin samples.The smaller the particle size,the smaller the elastic modulus of the sample.The peak load of each sample varies greatly,ranging from 0.6 Mn to 64.2 Mn.The smaller the indentation depth,the smaller the peak load of the specimen.The larger the particle size,the greater the load required when pressed into the same depth.The peak load of polyethylene glycol samples is greater than that of paraffin samples.Some samples have creep phenomenon,and the relative rebound rate of most samples decreases with the increase of indentation depth.The micro-test results provide the following supplementary explanations for the macro-test phenomenon: first,apart from the cementing force,the strength of the cement itself also contributes to the shear strength of the triaxial specimen;Secondly,the larger the particle size,the greater the proportion of skeleton particles resisting pressure;Finally,the greater the extrusion force of skeleton particles,the greater the resistance and shear strength of samples.