The sand-gravel mixture is a binary geotechnical material widely used in construction. Its shear behavior is a significant factor influencing the relevant structure safety or slope stability. In this study, a large-scale direct simple shear test was used to study the effect of gravel content on the shear behavior of the mixture. From the experimental results, macro-mechanical properties of the mixture were acquired with various gravel contents and compression stresses. However, the deeper understanding of the shear behavior of the mixture requires a profound microscopic investigation on the specimens. Based on the experimental tests, a series of three dimensional (3D) discrete element model (DEM) analyses of simple shear tests were carried out. The 3D DEM analysis results agree well with the experimental results. The particle generation process and shear stress calculation method have been improved in this model. Moreover, the gravel particle with authentic particle shape scanned by CT system was used in the simulation. The load transformation of the contact force and the evolution of the force network automatically recorded by the DEM program contribute to further understanding the significant role of the gravel content. In summary, both the micro- and macroscopic analyses were utilized to investigate the shear behavior of the sand-gravel mixture. The findings acquired from this study are expected to help researchers to better understand the role of the gravel content in the shear behavior of sand-gravel mixture and the particle-to-particle interaction mechanism.
Keywords: Discrete element method (DEM), Particle shape, Direct simple shear, Gravelly soils, Gravel content,