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Numerical modeling of aggregate-geogrid composite behavior for pavement applications using Discrete Element Method

The use of geogrids in road construction has been shown to augment service life and reduce aggregate consumption in pavement base layers (Montanelli et al., 1997). The enhanced performance arises from the lateral confinement of aggregates within geogrid apertures and improved granular interlocking (Giroud et al., 1985). The properties of aggregate-geogrid composite systems are influenced by gradation, aggregate morphology, geogrid stiffness, aperture shape and size, among others (Giroud and Han, 2004). The present study examines effects of such factors on the cyclic-loading behavior of geogrid-stabilized base layers using the discrete element method. Three-dimensional models simulated 3 stabilization conditions (non-stabilized, triaxial geogrid and full lateral confinement) for 3 diameter-to-rib length ratios. Aggregates were modeled as mono-sized spheres interacting via an elasto-plastic frictional contact law (Cundall and Strack., 1979), and geogrids followed a deformable element formulation (Effeindzourou et al., 2016). Stabilization cases proposed in this study offer a new and improved framework for assessing aggregate-geogrid systems based on rutting performance as follows. The upper and lower bounds are established by the non-stabilized and the full lateral confinement cases, respectively. In the latter, horizontal motion is fully constrained within a thin layer of aggregate elements while maintaining free vertical movement. This represents an idealized system where particles near the geogrid are completely laterally restrained. Results show an evolution of the composite response according to different diameter-to-rib-length size ratios in relation to the upper and lower bound cases.