Gas permeability of hybrid geosynthetics for landfill cap cover

Landfill cap covers that suppress water infiltration to the waste and promote rapidly gas permeation at the same time are demanded. We have developed hybrid geosynthetics that consist of porous sheet and nonwoven geotextiles as landfill cap covers and their basic performances have been investigated by laboratory and field tests. In this study, gas permeability of porous sheets was evaluated by laboratory test. Field test was also conducted to examine gas permeability of the hybrid geosynthetics installed in the underground. In both tests, variation of substitution rate of nitrogen gas with time at both spaces divided by the sample was investigated, while nitrogen gas was introduced to one side of the spaces. As the results, it was clarified that porous sheets themselves are suggested to have sufficient fundamental characteristics on permeability of gases with chemically-inactive and sufficiently small in molecular size. It was also demonstrated that hybrid geosynthetics exhibits gas permeability even when installed in the underground.