Development of Tensile Strain in a Geomembrane from a Small-to-Medium-Width Subgrade Rut

The tensile strain in a geomembrane developed from bridging a small-to-medium-width subgrade rut (i.e., linear indentation 50–200 mm wide) is examined. The effect of overlying stress, geomembrane thickness, indentation dimension (width B and depth D), and underlying geosynthetic clay liner (GCL) are investigated. Test results show that the largest geomembrane strain typically arises around the edge of the indentation and becomes greater with the increasing overlying stress until reaching a maximum value ε. The maximum strain (ε) at an indentation is proportional to D*B−0.3565. The depth D inducing 3% strain varied from 3 mm to 5 mm when B was between 50 mm and 200 mm. The development of tensile strain is not notably affected by the geomembrane thickness, and ε is not significantly affected by the aging of geomembrane. ε is reduced when a GCL is placed beneath the geomembrane, and the effectiveness of the GCL in reducing the tensile strain is not significantly affected by its water content. No crack is induced within the bentonite gel around the edge of the indentation, and the encapsulating geotextiles remain intact for tensile strains up to 12%. Finally, general installation guidelines on the subgrade preparation for GCLs and geomembranes are discussed.