Experimental methods for interface behaviors of geosynthetics in landfills

The pull-out tests,direct shear tests and simple shear tests are often used to investigate the interface behaviors of landfill liner systems.Pull-out tests for the interfaces of geomembrane-sand,geomembrane-clay,geotextile-sand and geotextile-clay,direct shear tests for the interfaces of geotextile-sand and geomembrane-clay,and simple shear tests for the composite liner interfaces of geonet-geomembrane-clay are presented.The test results show that the interface behaviors of geosynthetics and soil mainly depend on the surface characteristics of geosynthetics.The initial slope of stress-displacement curve from the direct tests and simple shear tests is steeper than that from the pull-out tests.The results from the simple shear tests show that the critical interface with the largest displacement in the composite liner is not fixed at a single interface.It can shift from one to another with changing normal stress.The strength envelop is the steepest for the pull-out tests,middle for the simple shear tests,and the lowest for the direct shear tests.The condition of composite liner in landfills can be reasonably simulated by the simple shear tests.The simple shear tests are suggested to investigate the interface strength of liner systems in landfills.