This document describes an index test method to determine the friction characteristics of geotextiles and geotextile-related products in contact with a standard sand, i.e. with a specified density and moisture content, under a normal stress and at a constant rate of displacement, using a direct shear apparatus.
The procedure can also be used for testing geosynthetic barriers.
When geogrids are tested with a rigid support, the results are dependent on the friction with the support and the results are not necessarily realistic. The accuracy of the test should be verified by calibration tests.