Impact of Gradation Change on Mechanical Behavior of Soil: DEM and Community Detection

A coarser soil structure resulted from fines loss may lead to change in hydraulic and mechanical properties which can cause significant settlement or failure of the levees, embankments and dams. This paper investigates mechanical consequence of gradation change induced by removal of finer particles in sand-gravel mixtures. Discrete Element Method (DEM) is used to conduct numerical triaxial tests of soils with prescribed loss of finer particles. A network-science based community detection method is used to characterize the force-chain networks of the soil samples under loading before and after loss of different amount of finer particles. A “community” refers to a set of particles which are closely connected with strong forces. The communities in a force-chain network can be detected by analyzing the inter-particle contact force data. Such communities can be quantified using intrinsic parameters such as community size (total number of particles in the community), strength (the total contact forces in the community), and morphology (the shape of the community). It is noticed that the effect of fines removal depends on the “size gap” between coarse particle and fines. Insights into the micro-mechanism can be gained from comparing the community parameters.