A new procedure for measuring geosynthetic friction with an inclined plane

A method for the determination of the friction angle of geosynthetic interfaces (specifically those in contact with soils at very low normal stresses) using an inclined plane is described by the European Standard EN ISO 12957-2. Following this “Standard Displacement Procedure”, the friction angle of a geosynthetic interface is determined using a displacement criterion between the tested geosynthetics. However, the “Standard Displacement Procedure” seems to be poorly suited for many interfaces. Herein, a new procedure is proposed, called the “Force Procedure”, which consists of measuring the force required to restrain a box on top of the interface beyond a limiting value of sliding displacement. With the “Force Procedure”, the friction is determined from the curve of friction mobilization versus plane-inclination. The angle determined with the “Force Procedure” is not sensitive to the conditions of the test and is more representative of real-world conditions, as it takes into account displacements observed in the field. Based on the results of this study, it seems reasonable to suggest a revision of the EN ISO 12957-2 standard testing procedure.