Modelling interference between the geogrid bearing members under pullout loading conditions

The main interaction mechanisms affecting the pullout resistance of geogrids embedded in soils are the skin friction between soil and reinforcement solid surface and the bearing resistance which develops against transversal elements. As regards bearing resistance the interference mechanism plays an important role: this can occur when the spacing between transversal members is lower than a threshold value, depending on the extensions of active and passive surfaces mobilized on bearing members. Based on the result of several large-scale pullout tests, a theoretical method to determine the peak pullout resistance of extruded geogrids embedded in a compacted granular soil is proposed. The method takes into account the interference mechanism due to the proximity of the transversal bearing members and works well for soil-geogrid interfaces in which scale effect is negligible.