Development of a Unique Test Apparatus to Conduct Axial and Transverse Pullout Testing on Geogrid Reinforcements

Abstract

In the design of reinforced soil structures, the pullout resistance of reinforcement embedded in the fill material is an important input parameter. Different pullout test setups have been proposed previously to determine the axial pullout resistances of reinforcements. In the present study, the details of a unique test apparatus with the ability to conduct both axial and transverse pullout testing of different types of reinforcement was highlighted. The pullout resistances of different geogrids embedded in uniform dense sand beds were presented. Based on extensive axial pullout testing on five different geogrids of varying tensile strengths and aperture sizes under three different normal stresses, empirical equations were proposed to estimate the axial pullout resistances of geogrids at two front-end pullout displacements. The estimated pullout resistances from the proposed equations were found to be in close agreement with the pullout resistances of a sixth geogrid considered in the present study and with the two other studies reported in the literature. A sensitivity analysis was carried out to determine the key parameters influencing the pullout resistance of the geogrid. For the different geogrids tested in dense sand, the axial pullout resistance factors were found to range from 0.34 to 1.97 and 0.52 to 2.05, corresponding to the reinforcement front-end displacements of 30 and 50 mm.