Design and use of multi-linear drainage geocomposites for gas collection layers

Abstract

Pore pressures generated by gas underneath a geomembrane can affect its integrity and the entire lining system. It can create whales/hippos in a surface impoundment, significantly reduce normal stress on the lower interface and create a veneer instability on final landfill cover. The membrane is lifted by the pressure of the gas trapped beneath it. The solution to avoid such occurrences is to install a permeable material that collects and transmits the gas outside the lining system. It can be vented to the atmosphere in the case of impoundments or collected in a gas collection network for valorization in case of landfills, for example. A sand layer is certainly possible, but drainage geocomposites offer an efficient and economical alternative. Depending on the application, the drainage geocomposite is designed to act as a passive system (no mechanical vacuum applied) or active. This paper presents the use of multi-linear drainage geocomposite for gas collection and its hydraulic behavior to collect and evacuate the gas. A case study is also given with the use of geocomposite as venting layer under a lined pond.