5.1 Installed geomembranes are subjected to forces from more than one direction, including forces perpendicular to the surfaces of the geomembrane. Out-of-plane deformation of a geomembrane may be useful in evaluating materials for caps where subsidence of the subsoil may be problematic.

5.2 Failure mechanisms on this test may be different compared to other relatively small-scale index tests and may be beneficial for design purposes.

5.3 In applications where local subsidence is expected, this test can be considered a performance test.

5.4 For applications where geomembranes cannot be deformed in the fashion this test method prescribes, this test method should be considered an index test.

5.5 Due to the time involved to perform this test, it is not considered practical as a quality control test.

1.1 This test method covers the measurement of the out-of-plane response of a geomembrane to a force that is applied perpendicular to the initial plane of the sample.

1.2 When the geomembrane deforms to a prescribed geometric shape (arc of a sphere or ellipsoid), formulations are provided to convert the test data to biaxial tensile stress-strain values. These formulations cannot be used for other geometric shapes. With other geometric shapes, comparative data on deformation versus pressure is obtained.

1.3 This test method requires a large-diameter pressure vessel (610 mm). Information obtained from this test method may be more appropriate for design purposes than many small-scale index tests.

1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

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.