In this study, interface direct shear tests were undertaken to investigate improvement in the mechanical behaviour of granular soils when reinforced with geotextile inclusions. Unlike past studies, various different parameters were investigated in the same study to uncover more assuring results. As expected, the interface friction angle of the reinforced sand was found to be lower than that of the unreinforced sand. No remarkable difference was seen in the shear strength of reinforced and unreinforced sands, but in reinforced sand, there was no post-peak loss of strength, as seen in unreinforced sand. Unexpectedly, geotextile inclusions did not restrict the soil from dilating. If the geotextile content was increased in the test specimen, only then did the dilation of the sand decrease. At the end of the results, it was concluded that the interface behaviour depends on the combined effects of the surface properties and deformability of the geotextiles, and also on the index properties of the soil. (C) 2012 Sharif University of Technology. Production and hosting by Elsevier B.V. All rights reserved.