Abstract: In view of the interfacial seepage between asphalt concrete facing and soil blanket of Baoquan Pumped Storage Project in China,experiments were made to investigate the interfacial seepage characteristics.The critical and the failure hydraulic gradients were obtained for different interfacial structures with and without sliding of the soil.Safety evaluations were made for the interfacial seepage of the project.For the interface structure strengthened by the fiberglass mesh,conclusions were drawn from the test results that the soil sliding relative to the mesh should be avoided,and the method of sticking the mesh directly up to the asphalt concrete surface was not suitable.