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New Test Method Reveals Geotextile-Filter Performance in Minutes

Designers of drains for roads, walls, landfills, and other structures use geotextile filters to keep soil out of drains. Since drain performance is directly related to openings in geotextile filtration products, it is important to test their pore size.

A new ASTM International test for geotextile filters, D 6767 Standard Test Method for Pore Size Characteristics of Geotextiles by Capillary Flow Test (2002), delivers real-time evaluation of pore-size in less than five minutes.

The PSD (pore-size distribution) test in D 6767 is much quicker than the commonly used AOS (apparent opening size) test, says civil engineer Barry R. Christopher, Ph.D., PE, of Roswell, Ga. “The AOS procedure can take upwards of four hours while the PSD procedure can be performed in a few minutes,” he says, “plus it gives a complete pore-size distribution where the AOS test only gives a single apparent pore size.” Using the standard can improve the ectiveness of geotextile filters in drainage designs, says Christopher, a geotechnical engineering consultant who designs drainage systems for roads, retaining walls, dams, and landfills.

Christopher led a task group of ASTM Committee D35 on Geosynthetics to develop the standard. “The intent of D 6767 is for manufacturers to run this test in the factory as a quality control test,” he explains. “Manufacturers can also use the test results to modify and improve their products for geotechnical applications. The rapid speed at which the test can be performed allows real-time evaluation and modification of products. The test can also be performed by users for acceptance of product and for design.”

The ASTM task group gathered input for the standard from the Syracuse University Geotechnical-Engineering Department, the University of Washington, Auburn University, from other civil engineers, independent laboratories, and manufacturers of geosynthetics and test equipment.

Christopher says ASTM D 6767 has the potential to eventually replace the AOS test as well as permeability/permittivity, and percent-open area tests. “The next effort of the task group [will be] to relate the pore-size distribution to filtration performance,” he concludes.

ASTM standards are available from Customer Service (phone: 610/832-9585; or go to For further information on the PSD standard, contact Christopher in Roswell, Ga. (phone: 770/641-8696). ASTM Committee D35 welcomes individuals to its June 16-19 meetings in Denver, Colo. For meeting or membership details, contact Maxine Topping, manager, Technical Committee Operations, ASTM International (phone: 610/832-9737). //

Copyright 2003, ASTM