ASTM D7178-22

1.1 This practice describes the procedure used along with existing test methods to determine the number of constrictions m of mechanically bonded non-woven geotextiles, based on thickness, mass per unit area, and fiber properties

1.2 The number of constrictions is a property of non-woven geotextiles, which is complementary to opening size to predict their filtration behavior. It can be used to differentiate non-woven geotextiles with similar opening sizes but different structures (thickness, weight, fiber diameter, etc.). However, more research is needed to assess its significance when comparing two products with different opening sizes.

1.3 Consideration of the number of constrictions is relevant in filtration applications where piping or clogging concerns are to be controlled with a high level of confidence, that is, for filter applications in critical soils.

1.4 This standard is for design purposes only and is not intended for quality control purposes.

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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.