【国外标准】 Standard Test Method for Determining the Pore Size Characteristics of Geotextiles Using an Optical Method

5.1 The significant opening size of geotextiles is usually determined using Test Method D4751, which involves sieving calibrated beads through specimens of the geotextile being evaluated. However, Test Method D4751 includes many risks of errors due to static electricity, precision of the glass beads, among other issues.5 This risk of error is even higher with knitted geotextiles which exhibit a very low tensile modulus. This test method is proposed as an alternate to Test Method D4751 using a nondestructive technique, where the stress conditions are controlled without manipulation of the specimen.5.2 This test method has been found to provide representative results for products exhibiting a planar structure, such as two-dimensional knits.5.3 In case of a dispute arising from differences in reported test results when using ASTM D4751 Method A and this method, ASTM D4751 Method A shall be considered the referee method. However, data obtained using ASTM D4751 Method A should be reviewed considering the high risk of human error associated with the control of the stress condition of the geotextile.5.4 Equivalency with the other pore opening size determined using other standards (for example, ISO 12956 and CGSB 148.1 No. 10) can also be considered using adequate correlations with test results obtained with these standards.1.1 This test method covers the determination of the pore size characteristics of geotextiles using an optical method and image analysis.1.2 This method has been developed for determination of the Image Opening Size (IOS) of knitted geotextiles by image analysis. Other properties may be obtained based on the pore size distribution.1.3 The applicability of this test method must be assessed on a product-by-product basis, as it requires light to pass through its thickness to provide a useful observation. As a general rule, the tested product must be thin. Example of products which cannot be tested using this test method is thick needle-punched nonwoven and woven with a complex three-dimensional structure.1.4 This test method shows 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.1.5 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.