Abstract: In the rockfill dam’s united anti-seepage system, the mechanical properties of the interface between geomembrane and cushion material have important influence on the stability of the dam. Firstly,we introduce the test equipment, test principle and method of geomembrane’s interface mechanical properties, and point out the deficiency in the process of calculating the real stress of its contact friction at the interface. Then, the traditional test equipment is modified, and a comparative analysis of results by the two test equipments was conducted under different working conditions. Finally, the real shear stress of geomembrane in the traditional test method is modified through the theoretical derivation, which has been verified by the test experiment. The verification result shows that the shear stress formula can really describe the mechanical properties of the interface between geomembrane and cushion material under shear force.

Key words: rockfill dam, geomembrane, mechanical properties of the interface, direct shear test, shear stress