The friction characteristics of interfaces that include geosynthetics are necessary to design such systems on slopes. Nevertheless, the design methods assume that these characteristics are constant for a given geosynthetic interface. From a series of friction tests carried out by an inclined plane device on a geotextile-related product/structured geomembrane interface, this paper shows that the friction properties are modified following successive slidings. Electronic microscope images reveal that the spikes of the structured geomembrane were altered due to sliding.