Effect Of Particle Axis Eccentricity On Fabric Of Granular Materials

Geotechnical mechanics is actually the mechanics of granular materials,and the difficulties in the development of geotechnical mechanics are mainly due to the complex discrete characteristics of geotechnical materials.After a long journey of finite element method,discrete element method(DEM)has become the main way for the development of geotechnical mechanics in the past two decades.According to the existing consensus,the macroscopic mechanical properties of granular materials are closely related to the mesoscopic fabric,and particle morphology has an important influence on the formation and evolution of the mesoscopic fabric.In addition to sphericity,angularity and roughness of particles,we focus on the axis eccentricity in the particle morphology,which is also an important factor,and there were few studies on it so far.Based on this,this paper focus on the particle axis eccentricity and carry out some simulations using the open source aspheric discrete element program Sudo DEM compiled by our team.By observing the formation and evolution of fabric during random packing and true triaxial shearing,the effect of axis eccentricity on the initial fabric and induced fabric of granular materials was explored.The main research contents and results of the paper are as follows:(1)An axis eccentricity was proposed to quantitatively characterize the degree of asymmetry of particle axis,and the quantitative indicators system of particle morphology was improved.A DEM model of asymmetric poly-superellipsoid was used to describe the change of axis eccentricity.A series of packing experiments were carried out using 3D printing eccentric particles.By comparing the experimental results with the simulation results,the rationality of the contact detection algorithm for poly-superellipsoid was verified.(2)The effect of axis eccentricity on the fabric of granular random packing was investigated.A series of random packing were simulated.The study of macroscopic phenomena such as angle of repose and packing flow state were carried out.Combined with stress distribution,coordination number,contact force network,friction mobilization index,etc.,a comprehensive microscopic analysis has been carried out.Then,the effect of axis eccentricity on the fabric of granular random packing was revealed,and some new insights were obtained.(3)The effect of axis eccentricity on induced fabric was investigated.A series of true triaxial shearing simulations were carried out.Mesoscopic quantities such as contact normal,contact force,branch vector were analyzed.The fabric anisotropy was characterized based on the fabric tensor and cross-scale relationship was established using the SFF theory(Stress-Force-Fabric),for discussing the effect of axis eccentricity on induced fabric,and then analyzing the mesomechanism of macroscopic shear strength improvement.