1.1 这些试验方法包括通过土工布（方法A1和A2）或使用毛细管孔隙率计（方法B）对玻璃珠进行干筛分来测定土工布的表观孔径（AOS）。 1.2 除非遵循本标准中规定的资格预审程序，否则不得使用方法B代替方法A。 1.3 这些测试方法以国际单位制和英寸-磅单位显示数值。国际单位制（SI units）是公制单位（即国际单位制）在技术上的正确名称。英寸磅单位是美国常用单位的技术正确名称。以英寸-磅为单位的数值仅供参考。 1.4 本标准并非旨在解决与其使用相关的所有安全问题（如有）。本标准的用户有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 1.5 本国际标准是根据世界贸易组织技术性贸易壁垒（TBT）委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认标准化原则制定的。 ====意义和用途====== 5.1 使用土工布作为介质来保留土壤颗粒需要土工布与相邻土壤之间的兼容性。该测试方法用于指示土工织物中的表观开口尺寸，其反映了土壤可通过的近似最大开口尺寸。 5.2 试验方法 D4751 对于土工织物开口尺寸的确定，可用于测试土工织物的商业装运。目前已经确定了实验室之间的精度估计。 5.3 使用方法A获得的表观开口试验结果可能不同于使用方法B获得的试验结果。本试验方法的目的是在允许使用该替代方法之前，确认方法B结果的等效性。选择使用方法B的实验室必须首先确定两种方法之间存在的任何偏差，并根据本试验方法记录可靠的相关性。 5.3.1 必须建立方法B结果和方法A结果之间的相关性，并满足本测试方法对使用方法B测试的每种不同土工布产品类型的要求。来自不同制造商或具有不同标称单位重量的土工布被视为不同的产品。必须将至少三个测试结果与所有三个满足既定相关性的结果进行比较。 注1: 当特定预合格土工布的制造发生变化时，应通过比较至少三个测试结果来确认特定产品的相关性。 5.4 如果因使用测试方法时报告的测试结果的差异而产生争议 D4751 对于商业装运的验收测试，买方和供应商应进行比较测试，以确定其实验室之间是否存在统计偏差。建议为调查偏差提供称职的统计协助。作为最低要求，双方应尽可能均匀地从大量相关类型的材料中选取一组试样。然后，应将试样以相同数量随机分配给每个实验室进行测试。两个实验室的平均结果应使用学生的 t -测试未配对数据和双方在测试开始前选择的可接受概率水平。如果发现偏差，必须找到并纠正其原因，或者买方和供应商必须同意根据已知偏差解释未来的测试结果。 5.4.1 如果争议涉及毛细管孔隙率计的测试结果，则方法A1被视为测试方法的仲裁方法 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. ====== Significance And Use ====== 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 .