A Study of Soil-Reinforcement Interface Friction

An important design parameter of reinforced soil structures is the friction mobilized between the soil and reinforcement elements, i.e., the pullout friction. The most commonly adopted method to identify this friction is a special test setup, i.e., the pullout test. Compared to the results of the pullout test, the direct shear test gives much smaller values. In this paper the mechanism of interaction between a soil and rigid planar as well as nail reinforcement is investigated. It is found that the mobilized friction between soil and reinforcement is influenced by the elastic parameters of the soil and its dilatancy angle. A simple approach is proposed from which the pullout friction can be estimated from the direct shear coefficient of friction between soil and reinforcement and the friction angle and dilatancy angle of the soil, all of which can be determined by direct shear tests. The results of the proposed model are in good agreement with results of pullout tests from the literature.