Interfacial Shear Behavior between Sand and Additive Manufactured Geogrid with a Re-entrant Structure

Conventional geogrids are often susceptible to brittle fracture. This study proposes a novel geogrid fabricated by additive manufacturing, having a re-entrant pattern with negative Poisson’s ratio (NPR) compared to a standard geogrid. This enhances the ductility and shear strength of the granular assembly, offering higher deformation tolerance with enhanced stability implications. A systematic investigation was conducted through a series of interface direct shear tests and transparent pullout tests to evaluate the influence of aperture size and particle size on reinforcement performance, employing three types of uniformly graded sand. Compared to a conventional geogrid, the NPR geogrid significantly enhances interfacial shear strength, controls dilation, and postpones pullout failure, leading to a progressive rather than abrupt failure of the reinforced specimen. Reducing aperture size of NPR geogrid increases interfacial shear strength. However, very small apertures may lead to reduced performance due to constrained soil-structure interaction. Transparent pullout tests further reveal that the NPR geogrid develops an extended plastic shear zone, enabling the reinforcement of a broader soil mass. Laboratory test results in this study highlight the NPR geogrid’s potential as a sustainable and effective solution for extending the service life of transport infrastructure through combined reinforcement and ductility of the granular assembly.