This paper presents selected issues on compatibility and integrity of geomembranes and geosynthetic clay liners (GCLs) among the recent challenges related to developments and applications of geosynthetics for environmental protection such as landfill engineering. They include (1) chemical compatibility of GCLs against waste leachate, (2) compatibility of geomembrane above clay-based landfill covers subjected to differential settlements, (3) influence of geogrid as a reinforcement layer within clay-based landfill covers, (4) application of geosynthetic materials applied to coastal waste landfills, and (5) possible application of geosynthetic barriers for environmental protection due to catastrophic disasters. First, we discuss the results of GCLs, of either natural or chemical resistant bentonites, that were subjected to hydraulic conductivity tests under non-prehydrated and prehydrated conditions using various types of chemical solutions and waste leachate. Heterogeneity is an important aspect that should be taken into account to discuss the hydraulic barrier performance, particularly when prehydration prior to the permeation of waste leachate is expected. Secondly, influence of geomembrane and geogrid reinforcement layer on the deformation behaviour clay-based landfill covers studied through centrifuge model tests is discussed. Thirdly, application of geomembranes in coastal landfills is reviewed. Design considerations include actions of wave and tide and stability of base ground. Several case histories implemented in Japan are introduced. Lastly, the current situation regarding the geo-environmental issues caused by the 2011 East Japan Earthquake and Tsunami, including environmental contamination by nuclides, is briefly described to mention the possibility of application of geosynthetic barriers for recovery works against catastrophic disasters.
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