A general expression for geosynthetic strain due to deflection

ABSTRACT: Giroud [Geosynthetics International, 2, No. 3, 635–641, 1995] presented expressions for the strain within a geosynthetic layer assuming it to take the shape of a circular or parabolic arc. A more realistic situation would be one in which the deflected shape consists of both circular and parabolic arcs. This technical note presents an expression for the geosynthetic strain for a combination of parabolic and circular shapes of the deflected geosynthetic, which is commonly observed in many field applications of geosynthetics. The special simplified cases of this general equation, expected in field situations, are discussed in detail. The variation of geosynthetic strain with relative deflection, defined as a ratio of rut depth (maximum deflection, r) to the initial length (L₀) of the geosynthetic, is presented to show the application limits of special simplified cases of the general equation. It is observed that the geosynthetic strain significantly depends on the shape of the deflected geosynthetic, especially at large rut depths. It is therefore recommended that the deflected geosynthetic shape considered must be exactly the same as the one observed or expected in the field application under consideration, especially at large strain levels. It is also shown that the approximate expression presented by Giroud holds for all possible shapes considered in this note, for small strains.