Study On The Effect Of The Particle Shape On Sand Critical State Behavior By Discrete Element Method

As a typical granular material,sand has complex mechanical behavior.The research on the mechanical behavior of the critical state of sand materials is the most fundamental aspect of the mechanics of granular materials.In critical state soil mechanics,the critical state parameters should be regarded as intrinsic properties that do not vary with the state or the boundary conditions under which a soil exists.but is affected by its own form.This article combines interpretation and analysis under the framework of critical state soil mechanics,the relationship between particle shape and critical state mechanical behavior is studied.The object of the study was an offshore quartz sand(LBS).Firstly,106 LBS particles were selected and the three-dimensional shape of the sample was obtained using high-precision X-ray CT scanning and image processing techniques.In order to obtain different particle shape,different spherical resonance orders were used in the process of spherical harmonic reconstitution of sand grains,and particles with the same particle size distribution but different shapes were randomly generated.The shape parameters of sphericity,convexity and roundness were used to quantitatively characterize the particle shape.The results show that the degree of smoothness of the particle surface is different from that of the spherical harmonic number n.The larger n is,the more obvious the meso-particle characteristics of the particle.At the same time,the difference in the degree of spherical harmonics has a greater influence on the sphericity,convexity,and roundness of the morphological parameters,but less on the aspect ratio.With the increase of the degree of spherical harmonics,the sphericity,convexity and roundness of the morphological parameters decreased,while the aspect ratio did not change significantly.On the macro-scale,the randomly generated virtual particles were introduced using the discrete element softwarePFC~3 ~D,and drained triaxial tests were carried out.Through the experiments of particles of different morphologies,it was proved that the shape of the particles has an influence on macroscopic mechanical behavior.As the irregulartiy of the particle shape increase,the critical state line in the q-p plane tends to rotate counterclockwise,and the slope and intercept values of the critical state line in the e-p plane increase.At the same time,the new shape parameters are defined as the overall regularity(OR),which is the average of sphericity,convexity and roundness.Analysis shows that the more uniform the overall shape,the smaller the slope and intercept values of the critical state line.Based on the analysis results,the relationship between critical state parameters and particle shape was established,providing a theoretical reference between the microscopic intrinsic properties of the particles and the macroscopic constitutive model.