Interface strength parameters are the key technical indices of the design and stability analysis of reinforcement. The pullout test is widely used for its better simulating of the field reinforced behavior. Through pullout test and direct shear test

the research focuses on the law and mechanism of the pullout (shear) rate’s influence on reinforcement interface characteristics and hydraulic fill sand

and the reinforcement effect of different fillers and different geosynthetics are discussed. The results show that: with the increase of pullout (shear) rate

the shear strength of sand-geotextile-sand interface decreases greatly while clay-geotextile-sand and sand-sand interfaces change little. From the perspective of strength index

sand-geotextile shear strength decreases mainly caused by the decrease of cohesive force; clay-geotextile shear strength increases mainly caused by the increase of friction angle; shear rate has little influence on hydraulic fill sand. Friction angle of reinforced soil is less than that of the soil itself. The interface characteristics of reinforcement are influenced by both pullout rate and normal stress level

related with type of geosynthetics and characteristics of soil. The choice of friction parameter for design and evaluation of reinforced structure should accord to the size of cohesive force.