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Student Award Paper Spotlight: Soil-Geosynthetic Interface Strength Properties from Inclined Plane and Direct Shear Tests – a Comparative Analysis

The October edition of Student Award Paper Spotlight presents the work of Ferreira, Vieira and Lopes, which won the Student Paper Award of the 6th Asian Regional Conference on Geosynthetics, in 2016. Through a series of laboratory tests, the authors investigated the differences in soil-geosynthetic interface shear strength parameters obtained from direct shear tests and inclined plane tests. More than 70 tests were carried out with a granite residual soil, varying the water content of the sample (dry, half of optimum water content, and optimum water content) and the geosynthetic used (geocomposite reinforcement and uniaxial extruded geogrid). Direct shear tests were used for values of normal stresses higher than 50 kPa, while inclined plane tests were used for the lower range of values. Regardless of the water content or the type of geosynthetic used, results showed that direct shear tests tend to provide parameters higher than the ones obtained with inclined plane tests, resulting in nonconservative extrapolations of the failure envelope for lower normal stresses. However, the combination of results from both tests revealed that the envelope can be represented accurately by one single straight line, as long as each test is carried out within the appropriate range of values.

To read the full paper, click here.

Reported by Leticia M. Nocko, from IGS Young Members Committee for the North American Region