ASTM D7864/D7864M-15

Standard Test Method for Determining the Aperture Stability Modulus of Geogrids

SIGNIFICANCE AND USE
5.1 The Aperture Stability Modulus is a measure of the in-plane shear modulus, which is a function of other geogrid characteristics, most notably junction stability, flexural rib stiffness, and rib tensile modulus.  
5.2 The test data can be used in conjunction with interpretive methods to evaluate the geogrid aperture stability at various traffic loads and base/subgrade conditions.
Note 1: Aperture stability modulus is referenced in the FHWA Geosynthetics Design and Construction Guidelines (2008) as an input parameter for the design of geogrid-reinforced unpaved roads using punched and drawn biaxial geogrids. Geogrids of different manufacturing process and material composition may use this property in calibration and validation of their material within the associated design.  
5.3 This test method is not intended for routine acceptance testing of geogrid. This test method should be used to characterize geogrid intended for use in applications in which aperture stability is considered relevant.
SCOPE
1.1 This 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.)  
1.2 This 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.  
1.3 This 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.  
1.4 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.  
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 and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 31-May-2015
• ICS: 59.080.70 - Geotextiles
• Technical Committee: D35 - Geosynthetics
• Drafting Committee: D35.01 - Mechanical Properties

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D7864/D7864M − 15
Standard Test Method for
1
Determining the Aperture Stability Modulus of Geogrids
This standard is issued under the fixed designation D7864/D7864M; the number immediately following the designation indicates the
year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last
reapproval. A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
3
1. Scope 2.2 FHWA Document:
FHWA Geosynthetic Design and Construction Guidelines
1.1 This test method covers the procedure for measuring the
(2008)
“Aperture Stability Modulus” of a geogrid. (The terms “Secant
Aperture Stability Modulus,” “Torsional Rigidity Modulus,”
3. Terminology
“In-plane Shear Modulus,” and “Torsional Stiffness Modulus”
3.1 Definitions:
have been used in the literature to describe this same property.)
3.1.1 For definitions of general terms used in this test
method, refer to Terminology D4439.
1.2 This test method is intended to determine the in-plane
3.1.2 geogrid, n—a geosynthetic formed by a regular net-
stability of a geogrid by clamping a center node and measuring
work of integrally connected elements with apertures greater
the stiffness over an area of the geogrid. This test method is
1
than 6.35 mm [ ⁄4 in.] to allow interlocking with surrounding
applicable for various types of geogrid.
soil, rock, earth, and other surrounding materials to primarily
1.3 This test method is intended to provide characteristic
function as reinforcement.
properties for design. The test method was developed for
3.1.3 index test, n—a test procedure which may contain a
pavement and subgrade improvement calibrated design meth-
known bias but which may be used to establish an order for a
ods requiring input of aperture stability modulus.
set of specimens with respect to property of interest.
1.4 The values stated in either SI units or inch-pound units
3.2 Definitions of Terms Specific to This Standard:
are to be regarded separately as standard. The values stated in
3.2.1 aperture—the openings between adjacent ribs forming
each system may not be exact equivalents; therefore, each
an angle which enable soil interlocking to occur.
system shall be used independently of the other. Combining
3.2.2 aperture stability modulus—a measure of the in-plane
values from the two systems may result in non-conformance
torsional stiffness of a geogrid. This is defined as torque,
with the standard.
divided by the rotation at that torque.
1.5 This standard does not purport to address all of the
3.2.3 geosynthetic, n—a product manufactured from poly-
safety concerns, if any, associated with its use. It is the
meric material used with soil, rock, earth, or other geotechnical
responsibility of the user of this standard to establish appro-
engineering material as integral part of a man made project,
priate safety and health practices and determine the applica-
structure, or system.
bility of regulatory limitations prior to use.
3.2.4 initial aperture stability modulus, n—the change in
moment at 0.5 and 1.0 N-m [4.4 and 8.8 lbf-in.], respectively,
2. Referenced Documents
divided by the change in angular rotation at these two moment
2
values.
2.1 ASTM Standards:
D4439 Terminology for Geosynthetics
3.2.5 junction, n—the point where geogrid ribs are intercon-
D4354 Practice for Sampling of Geosynthetics and Rolled
nected to provide structure and dimensional stability.
Erosion Control Products(RECPs) for Testing
3.2.6 offset aperture stability modulus—the change in mo-
ment at 2.0 and 2.5 N-m [17.7 and 22.1 lbf-in.], respectively,
divided by the change in angular rotation at these two moment
1
values.
This test method is under the jurisdiction of ASTM Committee D35 on
Geosynthetics and is the direct responsibility of Subcommittee D35.01 on Mechani-
3.2.7 rib, n—for geogrids, the continuous oriented elements
cal Properties.
of a geogrid which are interconnected to a node or junction.
Current edition approved June 1, 2015. Published July 2015. DOI: 10.1520/
D7864_D7864M-15
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
3
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Available from U.S. Department of Transportation, Federal Highway
Standards volume information, refer to the standard’s Document Summary page on Administration, 1200 New Jersey Ave., SE, Washington, DC 20590, http://
the ASTM website. www.fhwa.dot.gov.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
D7864/D7864M − 15
4. Summary of Test Method 5.3 This test method is not intended for routine acceptance
testing of geogrid. This test method should be used to char
...