Microscopic insight into the effect of particle gradation on the dynamic compaction of dry sand using DEM

Particle gradation is an important feature of granular materials, which has a significant influence on the mechanical properties of soil. Several dynamic compaction (DC) tests for mono-sized dry sand samples and a well-graded dry sand sample were modeled using discrete element method. The effect of particle gradation on crater depth was analyzed as well as coordination number, porosity and contact stress from a microscopic view. It is indicated that the change rates of dynamic stress, coordination number and porosity of the well-graded sample were greater than the results from the mono-sized samples. For the mono-sized samples and the well-graded sample, the differences in dynamic contact stress, coordination number and porosity became larger as the distance of measurement point from ground surface increased. The results also demonstrate from a microscopic view that the well-graded soil and the mono-sized soil with smaller particle size were more prone to become dense under DC. This study at a grain level is helpful to understand the microscopic mechanism of DC and has a certain guiding significance to the construction of DC.