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Test Method Title
Standard Test Method for Determining the Shear Strength of Soil-Geosynthetic and Geosynthetic-Geosynthetic Interfaces by Direct Shear
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.
Preferred Test Sample Size
geosynthetic-3' x roll width soil - five gallon bucket
Number of Test Specimens
3 (or more)
Test Specimen Size
geosynthetic - 12" x 18" soil - 12" x 12" x up to 6"
interface, direct, shear, adhesion, cohesion, friction, angle, Mohr-Coulomb shear strength envelope, Mohr-Coulomb friction angle
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