Thickness is one of the basic physical properties used to control the quality of many geosynthetics. Thickness values are required in calculation of some geotextile and geomembrane parameters such as permeability coefficients, tensile stress (index), and the like thickness is not indicative of field performance and therefore is not recommended for specifications.

The thickness of geotextiles and geomembranes may vary considerably depending on the pressure applied to the specimen during measurement. Where observed changes occur, thickness decreases when applied pressure is increased. To minimize variation, specific sample size and applied pressure are indicated in this method to ensure all results are comparable.

To determine the effect of difference pressure loadings on the measure thickness of geotextiles and geomembranes, use this test method.

This test method may be used for acceptance testing of commercial shipments of geotextiles and geomembranes, but caution is advised since information on between-laboratory precision is incomplete. Comparative tests, as directed in 5.4.1 may be advisable.

In case of a dispute arising from differences in reported test results when using this test method 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 formed from a lot of material of the type in question. The test specimens should 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 bias is found, either its cause must be found and corrected or the purchaser and supplier must agree to interpret future tests in the light of the known bias.

Note 1—The user should be aware that the compressibility of the materials, their rebound characteristics, and the like will also affect the thickness of the geotextiles and geomembranes following the time when they are rolled up on rolls shipped and stored.

1.1 This test method covers the measurement of the nominal thickness of geotextiles, smooth surfaced geomembranes, geonets, and geocomposite drainage products.

1.2 This test method does not provide thickness values for geosynthetics under variable normal compressive stresses. This test method determines nominal thickness, not necessarily minimum thickness.

1.3 The values stated in SI units are to be regarded as standard. The values given in parentheses are 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 and health practices and determine the applicability of regulatory limitations prior to use.