ASTM D7406-07

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.

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

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

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.

This creep data has is merit directly to the end user, because it can be easily interpreted to result into a reduction factor for creep . The Reduction factor can then be used to derive an allowable flow rate .

1.1 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).

Note 1—Results achieved from unconfined compressive performance creep may differ from testing performed under confined conditions.

1.3 Because of the changing nature of the geosynthetic industry, and the wide variety of products already available, this particular test method may have to be slightly modified for unconfined compression creep testing of some products..

1.4 The values given in SI units are to be considered as the standard. The values given in parentheses are for information only. This standard covers the specific procedures and test conditions that are applicable for exposure of unreinforced polyolefin geomembranes to fluorescent UV radiation and condensation.

1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.