Mahmood Reza Abdi - Faculty of Civil Engineering, K.N. Toosi University of Technology, Tehran, Iran
Mahdi Safdari Seh Gonbad - Faculty of Civil Engineering, K.N. Toosi University of Technology, Tehran, Iran

Contact surface roughness and geogrid aperture size are among the factors affecting soil-geogrids interaction. In this study, to investigate the effects of these factors, large-scale direct shear tests have been conducted using a well graded sand at a relative density of 80% reinforced with three geogrids having different aperture size. Samples were subjected to normal pressures of 12.5, 25 and 50kPa and sheared at a rate of 1mm/min. Geogrid surface roughness was achieved by gluing single sized sand particles. Results show that increasing geogrid surface roughness increases shear strength at soil-geogrid interface and there is an optimal relation between geogrid aperture size and shear strength increase

Geogrid, Direct shear, Interaction, Roughness.