Stress-Strain Response and Dilation of Geogrid-Reinforced Coarse-Grained Soils in Large-Scale Direct Shear Tests

Although the dilatancy of uniform sands or gravelly soil has been studied extensively in geotechnical engineering, studies on dilatancy of geogrid-reinforced coarse-grained soils are remarkably scarce in the literature. This paper presents an experimental investigation of the effects of geogrid and gravel content on the dilative behaviors of geogrid-reinforced sand-gravel mixtures. For this purpose, a series of large-scale direct shear tests were conducted on unreinforced and geogrid-reinforced sand-gravel mixtures with varying gravel content. It was found that the inclusion of geogrids results in higher ductility and friction angles of the specimens tested. Dilation was enhanced by an increase in gravel content but suppressed by the inclusion of geogrids. A hyperbolic model is developed to fit the stress-dilation relationship for the geogrid-reinforced specimens tested. The findings of this study may lead to a better understanding of the dilative behaviors of geogrid-reinforced coarse-grained soils.