Discussion of “Column Supported Embankments with Geosynthetic Encased Columns: Validity of the Unit Cell Concept” [Geotechnical and Geological Engineering 33 (2015) 425–442

Abstract

The authors present numerical analyses of an embankment underlain by geosynthetic reinforcement and supported by geosynthetic encased columns (GRCSE). In the last part of the paper, the transverse and longitudinal tensile forces in the geosynthetic reinforcement, which underlays the embankment, are compared using a 3-d strip model and the Unit-Cell concept, both in a 3-d model and in a 2-d axisymmetric model. The results of both Unit-Cell models are very similar. The authors show that the Unit-Cell models are not able to capture the transverse force (Tx), which seems obvious, nor the longitudinal force (Ty), which may not be so obvious. The discusser would like to explain that in the authors’ case the longitudinal force (Ty) is not properly captured by the Unit-Cell models because of the ‘‘socalled’’ Poisson effect. A measure of this effect is the Poisson’s ratio (m = -ey/ex) (Fig. 1). In the 3-d strip model, Tx is notably higher than in the Unit-Cell models, as expected. The authors use a Poisson’s ratio of m = 0.3 for the geosynthetic reinforcement, and then, the higher value of Tx causes an additional tensile force in the perpendicular direction (Ty) because of the Poisson effect. Assuming plane strain conditions in the longitudinal direction (ey = 0), ey 1⁄4 0 1⁄4 1 E ry mrx 1⁄4 1 E Ty t m Tx t ð1Þ