Effects of Pore Fluid and Surface Roughness on Geomembrane - Soil Interface Behavior

In this study, direct shear tests were conducted on soil - geomembrane interfaces. Sand/bentonite mixture and crushed sand were tested in contact with two geomembranes of the same type. To examine the effect of leachate on the mechanical properties of the geomembrane, acidic mine drainage, coal combustion product, and municipal solid waste leachates were prepared in the laboratory. The initial void ratio and internal friction angles of sand/bentonite and crushed sand were 0.34, 0.52, and 23⁰, 35⁰, respectively. In the smooth geomembrane - soil interface, the minimum interface friction angle (18⁰) was obtained on acidic mine drainage cured geomembrane – sand/bentonite, while the maximum (31⁰) interface friction angle was obtained on uncured geomembrane - crushed sand. In the textured geomembrane - soil interface, the minimum interface friction angle (17⁰) was obtained on acidic mine drainage cured geomembrane – sand/bentonite, while the maximum (43⁰) interface friction angle was obtained on uncured geomembrane - crushed sand. The friction angle of the crushed sand - geomembrane surface is higher than the friction angle of the sand/bentonite - geomembrane surface. While acidic mine drainage is the leachate that affects the shearing behavior of the geomembrane in the most negative way, coal combustion product is the leachate that has the least negative impact.