A validated discrete element modeling approach for studying geogrid-aggregate reinforcement mechanisms

Geogrids are commonly used in transportation applications for stabilization and reinforcement purposes. Factors affecting the interactions or interlock mechanisms between geogrids and aggregates may include but not limited to aggregate size and shape properties, geogrid types and properties, compactive efforts during installation, and loading conditions. To better quantify these effects, our recent research efforts at the University of Illinois have introduced the use of an image-aided Discrete Element Modeling (DEM) approach for studying the interactions of such local effects, i.e., aggregate particles and geogrid properties interacting at the micro-level to produce a "stiffened or reinforced" zone. A recent experimental study was utilized to model and demonstrate the effectiveness of different aperture-sized biaxial geogrids in the reinforcement of ballast aggregates to reduce settlement under cyclic loading. The image-aided 3-D DEM methodology successfully modeled the interactions between the ballast aggregate size and shape properties and the different aperture sized biaxial geogrids. Similar to the experimental study, only certain biaxial geogrid aperture sizes improved the performance of the reinforced ballast when compared to the larger settlement accumulated in the unreinforced ballast. The methodology has the potential for quantifying individual effects of various geogrid products on aggregates with different size and shape properties.