Evaluation of two-layered soils reinforced with 3D printed geogrid models under axisymmetric loading conditions

A series of drained triaxial tests was carried out on homogeneous and two-layered soil (TLS) samples under low confining pressure. A granite aggregate was selected as the base layer, and sand was used to simulate the subgrade. Geogrids with varying aperture sizes and stiffness values were designed using CAD software and manufactured using 3D printing technology. A method for correcting the cross-sectional area during triaxial TLS testing was developed. The load transfer at the aggregate-geogrid interface was also evaluated. The strength of the TLS samples increased as the relation between the aperture size of the geogrid and the median particle diameter was closer to unity. Consistent results were found for the polylactic acid (PLA), photopolymer (RGD 8560), and polypropylene (PP) geogrids, but better mechanical behavior was observed for the RGD 8560 geogrid. Higher tensile forces at the interface were mobilized in geogrids with greater stiffness. However, the best interface behavior is not solely governed by the geogrid stiffness. • Reinforced two-layered soils show interface confinement, with weak layer shear/bulging and aggregate layer lower strains. • 3D-printed geogrids optimized: best aggregate-geogrid interaction when aperture size matches particle diameter. • Geogrid stiffness isn't the only factor affecting reinforced two-layered soil behavior under load. • Instrumented strip reveals non-linear tensile force-strain relationship, highlighting boundary condition impacts on load transfer. • Optimal particle interaction achieved with RGD 8560 geogrid due to its geometry enhancing aggregate interlocking.