The function of the protective liner is to protect the liner from stresses, puncture and penetration from the overlying drainage media and waste: both short term dynamic loadings and long term static loadings. A protective material must protect the geomembrane through the permanent distribution of concentrated stresses on the geomembrane.
Geosynthetic protection layers have been in use since the late 1980s and now form the majority off liner protection methods. The driving forces behind the movement from mineral protection were lower costs due to void space savings and speed of installation, with a much lower risk of installation damage.
Once installed, a protective geotextile or goecomposite layer is placed before a stone leachate drainage blanket on the surface. It is important that the stone drainage blanket is free draining and has sufficient hydraulic conductivity to drain leachate over a large, relatively flat area. The secondary function of the drainage blanket is to provide a level of protection against the placement of the first layer of waste.
The selection of an appropriate geosynthetic protection layer is now made using the cylinder test. The cylinder test is recognised as an effective method for determining the effectiveness of a material in protecting a geomembrane against the long term effects of static point loads, it is designed to simulate as close as possible the conditions expected in the base of a landfill.