Investigation on the shear behavior of negative Poission's ratio geocell-sand interface

This study designed and fabricated a honeycomb-structured auxetic (Negative Poisson's Ratio, NPR) geocell using 3D printing technology. The stress-displacement behavior at the interface between the NPR geocell and sand was investigated using a direct shear apparatus, with comparisons made to the interfacial shear characteristics of unreinforced sand and traditional (PPR) geocells. The research demonstrates that under low normal stress, the interface between NPR geocells and loose sand exhibits higher peak stress and pronounced dilatancy, whereas under higher normal stress, the stress-displacement behavior aligns with that of unreinforced sand and PPR geocell reinforced sand interfaces. For loose specimens, the interfacial strength of PPR geocells with sand is higher, while for dense specimens, the NPR geocell-sand interface shows greater strength. The type of geocell has limited influence on the residual state line, whereas the relative density significantly affects it, with loose specimens exhibiting lower residual strength compared to dense ones. The residual state line of loose specimens in the void ratio-normal stress plane presents a higher intercept.