A simple method to evaluate the pullout resistance of extruded geogrids embedded in granular soil

Pullout tests are necessary in order to study the interaction behaviour between soil and geosynthetics in the anchorage zone; hence these properties have direct implications in the design of reinforced soil structures. Several experimental studies showed the influence of different parameters (reinforcement stiffness, geometry and length, applied vertical effective stress, and geotechnical properties of soil) on the peak and on residual pullout resistance . On the basis of the tests results carried out by the authors, a new theoretical method to determine the peak and the residual pullout resistance of extruded geogrids embedded in a compacted granular soil was developed. The method is capable to evaluate both the bearing and the frictional components of pullout resistance, taking into account the geometry and the extensibility of the reinforcement and the curvature of the failure envelope. The comparison between theoretical and experimental results showed a good agreement, thus confirming the suitability of the proposed approach.