ASTM D4632/D4632M-15 pdf free.Standard Test Method for Grab Breaking Load and Elongation of Geotextiles.
ASTM D4632/D4632M is an index test which provides a procedure for determining the breaking load (grab strength) and elongation (grab elongation) of geotextiles using the grab method. This test method is not suitable for knitted fabrics and alternate test methods should be used. While useful for quality control and acceptance testing for a specific fabric structure, the results can only be used comparatively between fabrics with very similar structures, because each different fabric structure performs in a unique and characteristic manner in this test. The grab test methods does not provide all the information needed for all design applications and other test methods should be used.
1.2 Procedures for measuring the breaking load and elongation by the grab method in both the dry and wet state are included; however, testing is normally done in the dry condition unless specified otherwise in an agreement or specification.
1.3 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.
4. Summary of Test Method
4. 1 A continually increasing load is applied longitudinally to the specimen and the test is carried to rupture. Values for the breaking load and elongation of the test specimen are obtained from machine scales or dials, autographic recording charts, or interfaced computers.
5. Significance and Use
5.1 The grab method is applicable whenever it is desired to determine the 6’cflective strength” of the fabric in use, that is, the strength of the material in a specific width, together with the additional strength contributed by adjacent material. There is no simple relationship between grab tests and strip tests since the amount of fabric assistance depends on the construction of the fabric. It is useful as a quality control or acceptance test.
5.2 The procedure in Test Method D4632/D4632M for the determination of grab strength of geotextiles may be used for acceptance testing of commercial shipments. hut caution is advised since information about between-laboratory precision is incomplete. Comparative tests as directed in 5.2.1 are advisable.
5.2.1 In case of a dispute arising from differences in reported test results when using the procedures in Test Method D46321/D4632M for acceptance testing of commercial shipments, the purchaser and the manufacturer 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 lake a group of test spccimcn that arc as homogcncous as possible and which arc 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 the appropriate Student’s t-test and an acceptable probability ]eel chosen by the two parties before testing is begun. If a bias is found, either its cause must he found and corrected or the purchaser and the manufacturer must agree to interpret future test results in the light of the known bias.
5.3 Most geotextile fabrics can he tested by this test method. Some modification of clamping techniques may he necessary for a gien fabric, depending upon its structure. Special adaptation may be necessaiy with strong fabrics, or fabrics made from glass fibers, to prevent them from slipping in the clamps or being damaged as a result of being gripped in the clamps, such as cushioning the clamp or hoarding the specimen within the clamp.ASTM D4632/D4632M-15 pdf download.