Geogrids and Geotextiles
Two new ASTM International standards will aid in the recent national movement to develop a mechanistic-empirical design guide for pavements. The new standards, developed by ASTM International D35 on Geosynthetics, each cover quantification of fundamental material properties for pavement components. D7499/D7499M, Test Method for Measuring Geosynthetic-Soil Resilient Interface Shear Stiffness, and D7556, Test Methods for Determining Small-Strain Tensile Properties of Geogrids and Geotextiles by In-Air Cyclic Tension Tests, are under the jurisdiction of Subcommittee D35.01 on Mechanical Properties.
“D7499 and D7556 will eventually be used to determine interaction properties and tensile properties of geosynthetic materials that will be directly utilized in the design of geosynthetic-reinforced pavements,” says Eli Cuelho, research engineer, Western Transportation Institute at Montana State University, and a D35 member.
According to Cuelho, when geosynthetics are used to reinforce the base course layers of flexible pavements, two required main design parameters include the interaction between the geosynthetic and the surrounding aggregates, and the tensile properties of the geosynthetic. While these properties are typically determined using static or semi-static loading, the most relevant interaction tests use cyclic loads. The new standards will provide tests to quantify soil/geosynthetic interaction properties or tensile properties of the geosynthetic when subjected to cyclic loading.
Cuelho says that the most likely users of D7499 and D7556 will be commercial testing laboratories that will run the tests for manufacturers and designers from public transportation agencies or private consulting companies. All interested parties are encouraged to join in the activities of D35.01.
Technical Information: Eli Cuelho, Western Transportation Institute, Montana State University, Bozeman, Mont.
ASTM Staff: Christine Basile