Soil-Geosynthetic Interface Strength and Stiffness Relationships From Pullout Tests

TLDR

Pullout tests are used to characterize the soil‑geosynthetic interface shear resistance and stiffness as functions of normal stress, but because geosynthetics are extensible, the data must be analyzed as a boundary‑value problem with assumptions about the geosynthetic constitutive behavior and interface interaction to be useful in analytical models of reinforced soil displacement. The study presents an analytical method that back‑calculates the shear stress–shear displacement relationship from pullout test data. The method is applied to evaluate interface shear stiffness and strength for a geogrid and a geotextile at three normal stress confinement levels. The study examines how the choice of material models influences the calculated interface properties.

Abstract

Pullout tests are commonly used to describe the ultimate shearing resistance developed along the interface between the confining soil and the geosynthetic as a function of normal stress confinement. Pullout tests can also be used to define the complete soil-geosynthetic interface relationship between shear stress and shear displacement interaction. Such a description of interface strength and stiffness characteristics is needed in analytical models used to predict a displacement response of geosynthetic-reinforced soil structures. Due to the extensibility of geosynthetics, data from pullout tests cannot be used directly to calculate strength and stiffness interface properties. The pullout test must be analyzed as a boundary-value problem with appropriate assumptions made regarding the constitutive relationship of the geosynthetic itself and for the interface interaction. An analytical method is presented that allows for the relationship between shear stress and shear displacement to be back-calculated from pullout test data. This method is used to evaluate interface shear stiffness and shear strength for a geogrid and geotextile product for three normal stress confinement levels. The significance of material models used in the formulation is examined.