5.1 Using a geotextile as a medium to retain soil particles necessitates compatibility between it and the adjacent soil. This test method is used to indicate the apparent opening size in a geotextile, which reflects the approximate largest opening dimension available for soil to pass through.

5.2 Test Methods D4751 for the determination of opening size of geotextiles is acceptable for testing of commercial shipments of geotextiles. Current estimates of precision, between laboratories, have been established.

5.3 Apparent opening test results obtained using Method A may differ from test results obtained with Method B. It is the intent of this test method to confirm the equivalency of the Method B results before permitting the use of this alternative. Laboratories electing the use of Method B must first determine any bias that exists between the two methods and document a reliable correlation in accordance with this test method.

5.3.1 The correlation between the Method B results and the Method A results must be established and meet the requirements of this test method for every different geotextile product type tested with Method B. Geotextiles from different manufacturers or with different nominal unit weights are considered different products. A minimum of three test results must be compared with all three satisfying the established correlation.

Note 1: The correlation should be confirmed for a particular product by comparing a minimum of three test results when there are changes in the manufacturing of a specific pre-qualified geotextile.

5.4 In case of a dispute arising from differences in reported test results when using Test Methods D4751 for acceptance testing of commercial shipments, the purchaser and the supplier should conduct comparative tests to determine if there is a statistical bias between their laboratories. Competent statistical assistance is recommended for the investigation of bias. As a minimum, the two parties should take a group of test specimens that are as homogeneous as possible and that are from a lot of material of the type in question. The test specimens should then be randomly assigned in equal numbers to each laboratory for testing. The average results from the two laboratories should be compared using Student’s t-test for unpaired data and an acceptable probability level chosen by the two parties before the testing is begun. If a bias is found, either its cause must be found and corrected or the purchaser and the supplier must agree to interpret future test results in the light of the known bias.

5.4.1 In the event that the dispute involves test results produced with the capillary porometer, Method A1 is considered the referee method for Test Methods D4751.

1.1 These test methods cover the determination of the apparent opening size (AOS) of a geotextile either by dry-sieving glass beads through a geotextile (Methods A1 and A2) or by using a capillary porometer (Method B).

1.2 Method B will not be used in lieu of Method A unless the pre-qualification procedure specified in this standard is followed.

1.3 These test methods show the values in both SI units and inch-pound units. SI units is the technically correct name for the system of metric units known as the International System of Units. Inch-pound units is the technically correct name for the customary units used in the United States. The values in inch-pound units are provided for information only.

1.4 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.

1.5 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.