Effect Of Particle Shape On Engineering Mechanical Properties And Micromechanical Properties Of Sandy Cobble Soil

Sandy pebble soil is a kind of special loose coarse-grained soil,which is widely used in various large-scale projects.The shape of sand and pebble formed naturally in nature is different.A lot of geotechnical engineering practice shows that sand and pebble soil has good shear performance.Because the shear performance of sand and pebble soil has a certain effect on its engineering mechanical properties,it is of great significance for practical engineering to study the influence factors of sand and pebble soil on shear performance.With the further study of geotechnical engineering,higher requirements are put forward for the study of sand pebbles.In this paper,direct shear test and numerical analysis are used to study the influence of particle shape on sand and pebble soil properties.The main research contents and conclusions are as follows:(1)Based on the observation of the shape and size of sand and pebble particles,the characteristic statistical analysis of the data was carried out to obtain the distribution characteristics of particle shape,and the distribution range of the particle shape parameters of random soil samples in the laboratory.By analyzing the parameters,it is found that the flatness of the particles has a great influence on the shape of the sand and pebble soil,and the flatness of most particles is concentrated between 1.2 and 2.2.(2)The influence of particle shape on its mechanical properties is analyzed through the direct shear test of sand and gravel soil.Three different shapes of particles are set according to different flatness to simulate the handling characteristics of particles under three different pressure states.According to the comparison between the shear stress curve and the peak graph,it is found that the increase of vertical pressure will increase the shear stress of particles,and the increase of flatness will enhance the shear performance of particles.(3)Based on particle flow discrete element method,direct shear test of sandy and cobble soil is simulated.Based on the shear stress curve,the numerical simulation was compared with the direct shear test to verify the feasibility of the numerical simulation.Using feasible numerical simulation technology,the macroscopic mechanical properties such as velocity field and displacement field were analyzed.Through analysis,with the increase of particle flatness,particle motion speed will decrease,particle displacement will also decrease.(4)Further excavate the mesoscopic parameters obtained by the discrete element software,and analyze the influence of particle shape on the rotation Angle,average coordination number and contact force chain of the sand and pebble soil from the mesoscopic level.The analysis shows that the rotation of particles is an alternate transformation,and with the increase of particle flatness,the more difficult it is for particles to rotate,and its average coordination number increases accordingly,and the particle force chain becomes sparse but more stable.