Effect of Soil Gradation on the Pullout Performance of a Uniaxial Geogrid

Abstract

Geogrids are widely used to reinforce soil in landfill, retaining wall, and paving projects due to their mechanical properties and cost-effectiveness. Their performance is directly related to the soil–geogrid interaction, facilitated by the openings in the material, which help increase strength and reduce deformation. This study investigates the effect of soil particle size distribution on the pull-out behavior of a uniaxial geogrid with a nominal strength of 60 kN/m. Monotonic pull-out tests were conducted using large-scale testing equipment (1.5 m × 0.7 m × 0.48 m). To isolate the effect of particle size distribution, the relative density was kept constant at 75% under confining pressures of 6.25, 12.5, and 25 kPa. The materials used consisted of sand and gravel, with average particle diameters of 0.83 mm and 6.48 mm, respectively. The results showed that the increase in grain size provided a minimum increase of 40% in the maximum pulling force, and this effect was more significant under higher confinement stresses. It was also observed the increase of resistance with the increase of normal stress, as well as greater mobilization of efforts when the ratio between the opening of the geogrid and the characteristic diameter of the grains approaches unity. It can be concluded that particle size plays a significant role in the pull-out behavior of geogrids and should be taken into account in the analysis of soil-reinforcement interaction and in the design of reinforced soil structures.