Experimental investigation on the pullout behaviour of geosynthetics embedded in a granite residual soil

Geosynthetics, including geogrids and geotextiles, have been extensively used for stabilisation and soil reinforcement in several geotechnical structures, such as foundations, abutments, walls and slopes. In these applications, soil-geosynthetic interaction plays a determinant role. This paper describes an experimental study carried out using a large-scale pullout test apparatus, aiming to investigate the pullout behaviour of different geosynthetics embedded in a granite residual soil. The study involved two geogrids (one biaxial and the other uniaxial), one geocomposite reinforcement (high-strength geotextile) and one geotextile. The soil was compacted to different relative densities. Test results have revealed that soil-geosynthetic interaction under pullout loading conditions is highly influenced by the geosynthetic properties and soil density. Regardless of soil density, the biaxial geogrid exhibited higher pullout resistance than the other geosynthetics. At maximum pullout force, the deformation along the length of the geotextiles was considerably more pronounced than that along the geogrids. For the conditions adopted in this study, the soil-geosynthetic pullout interaction coefficients ranged from .25 to .52. In general, the values of the scale effect correction factor obtained for the geotextiles were slightly lower than the value recommended by the Federal Highway Administration in the absence of test data.