Soil-Reinforcement Interaction of a Geogrid–Geotextile Composite

The use of geosynthetic reinforcement in roadways can provide improved performance as demonstrated in numerous field tests and studies. It is common practice in many regions to install a reinforcement layer (e.g., geogrid) between the subgrade and base course to provide stiffening, reinforcing, and volumetric control, along with a filtration layer (e.g., non-woven geotextile). Alternatively, composite products can combine the functions of geogrids and non-woven geotextiles by bonding two products together into one composite product. There is limited testing information comparing geogrid reinforcement overlying non-woven textiles versus geogrid–geotextile composites. The purpose of the study was to compare the interface performance between separating subgrade and base materials with an assembly of a non-woven geotextile overlaid with a geogrid versus a geogrid–geotextile composite. Large-scale pullout tests were performed to measure the geosynthetic–geosynthetic interaction between a geogrid and non-woven geotextile. Large-scale direct shear tests were performed to measure the soil–geosynthetic interaction of the geogrid–geotextile composite and representative subgrade and base course soil. It was found that the geosynthetic–geosynthetic interface had lower shear strength than the soil–geosynthetic interface. This suggests that the use of a geogrid–geotextile composite can potentially improve soil reinforcement compared to layering a geogrid on a separate non-woven geotextile by eliminating the critical geosynthetic–geosynthetic shear plane.