Experimental Investigation of Deformation and Geogrid-Soil Interface Behavior of Triaxial Geogrid

In order to investigate the behavior of geogrid-soil interface of traxial geogrid, a series of laboratory pullout tests focusing on triaxial geogrid were conducted considering the effect of two kinds of pullout directions, referred to as TX_0 case and TX_90 case, respectively. The geogrid displacements were measured at four sections along the geogrid specimens. Based on the measurements, the relation between pullout force and pullout displacement and the deformation of each geogrid segment were studied. Furthermore, the dilatancy/shrinkage behavior, the relation between the average friction and relative displacement, and the effect of pullout directions on the interface strength were also analyzed. The experimental results demonstrate that the degree of compaction has a great influence on the pullout force and shear dilatancy/shrinkage behavior of the geogrid-soil interface. As the normal stress increases, the shear shrinkage increases while the shear dilatancy decreases. The shear displacements corresponding to the maximum shear dilatancy/shrinkage also increase with the increase of normal stress. The interface friction develops in a progressive mode and an elasto-plastic softening characteristic is observed of the interface behavior. The geogrid-soil interface strength of the TX_0 case is higher than that of the TX_90 case when the normal stress is higher than 20 kPa.