1.1This test method covers the procedure for measuring the “Aperture Stability Modulus” of a geogrid. (The terms “Secant Aperture Stability Modulus,” “Torsional Rigidity Modulus,” “In-plane Shear Modulus,” and “Torsional Stiffness Modulus” have been used in the literature to describe this same property.)

1.2This test method is intended to determine the in-plane stability of a geogrid by clamping a center node and measuring the stiffness over an area of the geogrid. This test method is applicable for various types of geogrid.

1.3This test method is intended to provide characteristic properties for design. The test method was developed for pavement and subgrade improvement calibrated design methods requiring input of aperture stability modulus.

1.4The 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.

1.5This 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.