Numerical Simulation of Mechanical Behavior of Unsaturated Granular Soil with Polygonal Particles Using Discrete Element Method

Numerical modeling of unsaturated soils has become increasingly popular in recent years. The Discrete Element Method (DEM) is a powerful tool for modeling granular materials by focusing on particle interactions. In this study, the behavior of unsaturated granular soil was investigated using two-dimensional DEM by considering meniscus formation among particles. Unlike previous studies that simply considered particle shapes as circular or spherical, this study used more realistic polygonal particles shape that forming meniscus can be examined in different pores with respect to the geometry and arrangement of the particles. However, because of symmetry in circular and spherical particles, the shape of the meniscus among these particles depends only to the size of the particles. To this end, using a program based on the DEM was developed and a soil sample were simulated under different suction values and confining pressures. The results showed that the shear strength of the sample augments by increasing suction until a specific value and then, decreased with further suction increases. It was also observed that the effect of meniscus force on increasing shear strength decreased with increasing confining pressures. Modeling particles of different sizes also showed that the effect of meniscus force is greater for smaller particles and decreases with particle size.