Geogrid-soil interaction: A new conceptual model and testing apparatus

Abstract

This paper provides a more realistic representation of the soil-geogrid interface in indirectly activated geogrids. A new testing apparatus is designed using transparent soil that allows an unobstructed observation of the interface to investigate the interaction occurring along the reinforcement. In this investigation, the reinforcement is indirectly activated by the deformations of the surrounding soil. Deformations were determined by digital image correlation (DIC) using a dot pattern attached to the geogrid and a laser speckle plane within the transparent soil. The interaction is derived from relative soil-geogrid displacements, deflections of geogrid transverse members, geogrid strain and force distributions as well as shear stresses acting at the interface. Three zones were identified corresponding to the distinct modes of interaction: pushout, pullout and interlocking, whereby a micro-mechanical conceptual model was validated. The geogrid force reaches its maximum at the intersection of the critical slip plane with the reinforcement. The results indicate that the pushout, pullout and interlocking areas cover 15%, 49% and 36% of the total geogrid length respectively. In this study, a transition area between the pushout and pullout zones was observed where the mobilised interface shear stress increases to a maximum value.