Abstract: To investigate the interaction characteristics between geotextile membranes and fill materials, direct shear friction tests were conducted with two types of fill materials: dry standard sand and wet expansive clay. The test results showed that as the normal stress increased, the interfacial shear stress between the membrane and fill materials gradually rose. The peak and residual shear stresses of the membrane-dry standard sand interface were higher than those of the membrane-wet expansive clay interface. The peak interfacial cohesion and friction angle of the geotextile membrane in dry standard sand were 9.28% and 43.37% higher, respectively, than those in wet expansive clay, while the residual interfacial cohesion and friction angle were 39.17% and 26.60% higher, respectively. During the direct shear tests, both fill materials exhibited significant shear contraction. The vertical displacement of dry standard sand showed an up-and-down fluctuation, whereas wet expansive clay remained continuously compressed. The apparent friction coefficient at the membrane-dry standard sand interface was greater than that at the membrane-wet expansive clay interface, but both were less than 1. These findings provide important technical support for the engineering application and design of geotextile membranes.

Key words: Geomembrane, Interface Friction Characteristics, Shear Contraction, Packing material, Apparent friction coefficient, Intensity index