ASTM D7406-07(2012)

5.1 The performance characteristics of a drainage geosynthetic are directly related to the integrity under compressive loading. If the product is sensitive to compressive creep, its flow capacity could be greatly reduced or even shut off completely.

5.2 The creep sensitivity of a candidate geosynthetic can be tested at field-simulated normal stress and potentially shear stresses.

5.3 This test method does not evaluate the effect of creep of a geotextile filter or adjacent membrane.

5.4 Compression creep as it relates to reduction in flow capacity of a geosynthetic drainage product is manufacturer and product specific. For example, a 10% reduction in original thickness of a geonet made by manufacturer A does not necessarily equal the same reduction in flow capacity as a 10% reduction in thickness of the same or another type of geonet made by manufacturer B.

5.5 This creep data has is merit directly to the end user, because it can be easily interpreted to result into a reduction factor for creep³ . The Reduction factor can then be used to derive an allowable flow rate1.1 This test method is used to determine the unconfined compressive creep characteristics of drainage geotextiles, geocomposites, geonets, or any other geosynthetic associated with drainage at a constant temperature, when subjected to a constant compressive stress.

1.2 This test method is intended for use as an unconfined compressive performance creep test only. For a detailed procedure on how to establish an index test see the EN standard 1897. For performance tests, the specimen shall be subjected to the site-specific liquid and/or the site-specific stress (normal and potentially shear stress).