Macroscopic And Mesoscopic Mechanism Of Interface Between Granular Material And Geogrid

Geotechnical engineering often uses reinforced materials to improve the strength and stability of the bulk material.The interaction mechanism between the granular material and the reinforced material is the focus of research.With the advancement of discrete element method and testing technology,the research on the mechanism of soil and soil is developing in a mesoscopic direction,but the mechanism of synergy between the reinforced materials and the granular materials is still unclear,so that the engineering application of geogrid is limited.Aiming at the problem that the interface mechanism between the reinforced materials and the granular materials is unclear,the geogrid reinforced sand is selected as the research object,and the two-dimensional particle flow model of the interaction between geogrid and sand is established.Combining laboratory experiments with numerical simulations,the reinforcement mechanism and reinforcement theory of the grid were analyzed from meso and macroscopic conditions,and the influence mechanism of particle motion on the reinforced-soil interface was revealed.The main work and results are as follows:（1）Based on the two-dimensional particle flow code,the interfacial shear tests were carried out on the different shapes of the clump.By comparing the results of the laboratory tests,the microscopic reflections of the macroscopic mechanical properties of the numerical samples were studied.The influence of the normal stress and the gravity of the particles makes the degree of occlusion and interlocking between the particles in the upper box larger than that of the particles in the lower box.The disturbance range of the soil on both sides of the soil-geogrid interface is not equal.（2）Using the discrete element software PFC^2D to carry out the numerical simulation of particle flow in the direct shear test of the slab soil,study the different shearing state under the same normal stress,and the deformation of the reinforced soil during the shearing process by the deformation of the square set in the sample.A comprehensive analysis of the macroscopic and mesoscopic properties of the force and deformation reveals the interaction mechanism of the interface between the soil and the earth.The results show that the contact force between the particles is related to the distance from the block to geogrid.The larger the distance between the block and the geogrid is,the smaller the contact force between the particles is.The movement state of the particles in the interface area of the soil determines the dilatancy of the sample.The particles near geogrid are mainly rotated,and the particles farther from geogrid are mainly translational.（3）In order to study influence of cyclic shear loading on soil-geogrid interface,a series of cyclic shear test simulations were carried out by using DEM.The motion information of internal particles of the sample under different compactness and cycle times was obtained,and the sample under horizontal cyclic loading was explored.The movement state of internal particles and the development of shear behavior of soil-geogrid interface.The results show that with the increase of cycle times,the cycle of the shear stress of the dense sand sample gradually develops inward,showing obvious softening characteristics.Meanwhile the area where the particle rotates does not increase significantly,and the thickness of the shear band is not obvious.