GEOSYNTHETIC SOIL INTERFACE FRICTION ANGLES USING A ROTATION SHEAR DEVICE

A modified rotation shear device was used for measuring interface fric tion angles between soils and geosynthetics. The device was modified s o that a geosynthetic specimen can be attached to the upper platen. A reliable method for cutting and attaching geosynthetic specimens to th e device is described. The geosynthetic mounting system is simple, str ong, and easy to remove. Interface friction angles and interface effic iencies for two ash samples and Boston Blue Clay with three geosynthet ics are reported and compared. A range of strength increase is reporte d for a given soil with change from a smooth geomembrane to a textured geomembrane or nonwoven geotextile. Shear displacements up to 300 mm are quantified in the paper, showing that large, unidirectional displa cements may accumulate in the rotation shear device.