Interaction between geomembranes and granular materials

The interface frictional resistance developed between two commercially available geomembranes and granular materials with different particle sizes was measured in the laboratory using a large direct shear apparatus. The surface of one of the geomembranes was smooth, while the surface of the other was rough (textured geomembrane). The interface friction angle between the rough geomembrane and the granular material generally increased with the size of the particles. However, the interface friction angle reached a maximum value when the particle sizes ranged between 0.64 and 3.38 mm. Thus for the rough geomembrane there was an optimum particle size range for which a maximum interface resistance developed. From the direct shear experiments between the smooth geomembrane and the the granular material of different sizes it was determined that the interface friction angle decreased as the size of the particles increased. The maximum interface friction angle was measured when the particle size was equal to 0.18 mm. An explanation for the frictional resitance that develops between a granular material and geomembranes is presented using a theoretical model. This model employs three cylinders under stress conditions similar to those experienced by a granular material-geomembrane interface system.