Abstract: The interaction between soil and reinforcement is the fundamental cause of the strengthening of reinforced soil. It is also a key issue in the application of geosynthetic reinforced soils. In this article, the effects of normal stress, sand cushion thickness and spacing between transverse ribs on ultimate pullout resistance of reinforced body were analyzed through pullout test. The mechanical properties of reinforcement-soil interface were also revealed in a macro-sense. Results suggest that sand cushion of 5 cm thickness could remarkably enhance the ultimate pullout resistance of geogrid. The influence of sand cushion thickness on test result is more obvious under large normal stress. Moreover, the frictional angle of geogrid-soil interface decreases with the increasing of the spacing between transverse ribs; but the cohesion stays stable. The shape of geogrid is also an important factor affecting the properties of interface between reinforcement and soils.

Key words: geogrid, pullout test, reinforced sand cushion, spacing between transverse ribs, parameters of geogrid-soil interface