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

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

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

Note 1—Although, this test specifies a vessel size of 600 mm, larger diameter vessels will better approximate field performance. However, the user is cautioned that different size vessels may yield different results and hence may not be comparable.

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

Due to the time involved to perform this test method, 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 geosynthetics to a force that is applied perpendicular to the initial plane of the sample.

1.2 When the geosynthetic 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 is more commonly used to test geomembranes. Permeable materials may also be tested in conjunction with an impermeable material.

1.4 This test method requires a large diameter pressure vessel (600 mm). Information obtained from this test method may be more appropriate for design purposes than many small scale index tests such as Test Method D6693 or Test Method D7003.

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

1.6 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 and health practices and determine the applicability of regulatory limitations prior to use.