#### Test Method Title

Standard Test Method for Determining the Shear Strength of Soil-Geosynthetic and Geosynthetic-Geosynthetic Interfaces by Direct Shear

#### Reference Number

ASTM D5321

#### Material

Geogrid

#### Test Property

Interface shear, cohesion, friction angle

#### Description of Test

Shear resistance between a geosynthetic and a soil, or a geosynthetic and another geosynthetic is measured. The geosynthetic and other material is placed within a large-scale direct shear box with an applied normal load on top. The normal loads used (typically at least three) normally represent design conditions. A shear force is applied to the apparatus such that one section of the box is moved in relation to the other. The shear force is recorded with respect to displacement. The peak and post-peak shear stresses are plotted against the applied normal stresses. The test data are presented by a best fit straight line whose slope is the coefficient of friction between the two materials where the shearing occurred. The y-intercept of the straight line is the adhesion.

#### Number of Test Specimens

3 (or more)

#### Test Specimen Size

geosynthetic - 12" x 18" soil - 12" x 12" x up to 6"

#### Keywords

adhesion, angle, cohesion, direct, friction, interface, Mohr-Coulomb friction angle, Mohr-Coulomb shear strength envelope, shear