Clayey Sand Soil Interactions with Geogrids and Geotextiles Using Large-Scale Direct Shear Tests

Access to suitable materials for the construction of reinforced earth structures in some areas may challenge the profitable feasibility of the project. In such areas, replacing the common embankment materials with materials containing numerous fine grains available on-site can lead to significant cost savings. Providing solutions for the use of this type of material has always been the focus of researchers. Finding suitable reinforcement and correct evaluation of shear strength parameters of the soil-reinforcement interface are among these solutions. To investigate the effects of geosynthetics, soils fine grains, and water content, the shear strengths of the clayey sand soils-reinforcements interface were compared, using large-scale direct shear tests. The results revealed that the strength curve of the interface was near to the soil strength curve in soil with 5% fine grains; however, the reinforcement in the saturated state for large shearing displacements led to a higher shear strength than the soil strength. For the soil containing 20% and 40% fine grains with optimum water content, the use of geogrids and geotextiles dropped the shear strengths of the interfaces to values lower than the soil strength for small shearing displacements. In the saturated state, the shear strengths of both reinforcement interfaces with soil were vastly higher than the internal soil strength. The results revealed that soils containing fine grains could be perfectly reinforced using geogrids and geotextiles. However, the effect of using geogrids in sandy soils with lower fine grain contents was greater than the geotextile. Conversely, in soils containing a high percentage of fine grains, especially those that have high water content, the geotextile as reinforcement was more efficient than the geogrid.