Mesoscopic View Of The Effect Of Particle Shape On The Shear Properties Of Coarse-grained Soilsnumerical Experimental Research

Coarse-grained soil is a complex non-viscous discrete granular material,and its shear strength is mainly composed of inter-particle sliding friction strength and occlusal friction strength,and the degree of occlusion is mainly determined by the particle shape,so the particle shape affects the coarse grain.It is an important factor of soil mechanical properties,and it is crucial to the study of particle shape.In this paper,with the aid of the particle flow program PFC^3D based on DEM principle,numerical models of triaxial drained shear and triaxial undrained shear of coarse-grained soil are established,and a series of triaxial shears are carried out on coarse-grained soil samples with different particle shapes.The numerical simulation of the experiment was carried out to explore the influence of particle shape on the macroscopic and mesoscopic mechanical properties of coarse-grained soil samples under different drainage conditions,confining pressure and mesoscopic parameters.The main research results are as follows:（1）The research background and significance are systematically introduced,and the research on the parametric characterization methods of particle shape at home and abroad,the influence of particle shape on the macro-mechanical properties of coarse-grained soil,and the influence of particle shape on the critical state characteristics of coarse-grained soil are reviewed.status quo.In this paper,based on two types of regular and complex coarse-grained soil particles with eight different shapes,the concept of particle sphericity is introduced to characterize different particle shapes by parameter,and regular particle samples and complex particle samples are established respectively.Numerical simulation program for triaxial drained shear,undrained shear tests of shapes.（2）Numerical simulations of triaxial drainage shear tests of two types（regular grains and complex grains）of coarse-grained soil samples were carried out.Macroscopically,the effects of particle sphericity,confining pressure and two types of meso-parameters（interparticle friction coefficient,effective contact modulus）on the stress-strain characteristics and dilatancy of the sample,and the interparticle friction coefficient on the peak value of the sample were analyzed.The influence of deviatoric stress,deformation modulus and internal friction angle was analyzed,and the influence law was analyzed;in the microscopic view,the influence of the above parameters on the texture tensor modulus,particle displacement and contact force chain of the coarse-grained soil sample was analyzed.（3）Numerical simulation of triaxial undrained shear test of complex-grained coarse-grained soil samples was carried out.Macroscopically,the effects of particle sphericity,confining pressure and inter-particle friction coefficient on the stress-strain characteristics and stress paths of coarse-grained soils are analyzed;at the microscopic level,the influences of the above parameters on the fabric tensor modulus of coarse-grained soil samples,The influence of particle displacement and contact force chain.（4）Based on the numerical simulation results of the triaxial shear test,combined with the classical macroscopic critical state theory and the critical state theory of mesoscopic fabric tensor,the influence of particle sphericity on the mechanical properties of the critical state was analyzed,and verified from the perspective of numerical simulation The uniqueness of the critical state line is discussed.In the microscopic view,the variation of the fabric tensor with the void ratio of the samples with different sphericity before and after normalization is discussed.