1385
Characterization of Soil-Geosynthetic Interaction under Small Displacements
Conditions
Caractérisation de l'Interaction sol-géosynthétique sous des conditions de petits déplacements
Zornberg J.G., Roodi G.H., Ferreira J.
The University of Texas at Austin, Austin, Texas, USA
Gupta R.
Geosyntec Consultants, Columbia MD, USA
ABSTRACT: While ultimate failure governs the performance of some geosynthetic-reinforced systems (e.g. reinforced walls), the
small displacement response governs the behavior of geosynthetic-reinforced pavement systems. Yet, quantification and
characterization of the effectiveness of geosynthetic products under small displacement conditions has been limited. The purpose of
this study is to develop a soil-geosynthetic interaction model that captures the stiffness of the soil-geosynthetic interaction under small
displacement conditions. The proposed model assumes: (1) a linear relationship between the axial strain of the confined reinforcement
and its unit tension, and (2) a uniform soil-geosynthetic interface shear over the active length of the geosynthetic. The resulting force
equilibrium differential equation is solved using a force boundary condition at the free end of the geosynthetic, and a displacement
boundary condition at the end of the active length of the geosynthetic. The solution results in a parameter, the stiffness of soil-
geosynthetic interaction, which consolidates the tensile properties of geosynthetic with the interaction properties of the soil-
geosynthetic interface. Results of laboratory pullout tests illustrate the validity of the soil-geosynthetic interaction model.
RÉSUMÉ : Alors que la rupture finale régit les performances de certains systèmes renforcés par des géosynthétiques (par exemple les
murs renforcés), la réponse en petits déplacements régit le comportement de chaussées renforcées par des géosynthétiques. Pourtant,
la quantification et la caractérisation de l'efficacité des produits géosynthétiques sous des conditions de petit déplacement ont été peu
étudiées. Le but de cette étude est de développer un modèle d'interaction de sol-géosynthétique qui prenne en compte la rigidité de
l'interaction sol-géosynthétique sous les conditions de petit déplacement. Le modèle proposé suppose: (1) une relation linéaire entre la
déformation axiale du géosynthétique confiné et la contrainte de traction, et (2) un cisaillement uniforme à l’interface entre le sol et le
géosynthétique sur la longueur active du géosynthétique. L’équation différentielle résultant de l’équilibre des forces est résolue à
l'aide des conditions aux limites à l'extrémité libre du géosynthétique, ainsi qu’une condition aux limites de déplacement à la fin de la
longueur active du géosynthétique. La solution met en évidence un paramètre, le coefficient de rigidité d'interaction sol-
géosynthétique, qui combine les propriétés en traction des géosynthétiques avec les propriétés de l'interaction de l'interface sol-
géosynthétique. Les résultats des essais d’arrachement en laboratoire illustrent la validité du modèle d'interaction sol-géosynthétique.
KEYWORDS: Geosynthetics, Interface Shear, Soil-Geosynthetic Interaction, Small Displacement Conditions, Reinforced Pavement.
1 INTRODUCTION
Geosynthetic reinforcements are widely used in two groups of
geotechnical systems: 1) Retaining walls and slopes, and 2)
Pavement systems. In retaining structures and slope
stabilization projects, geosynthetic reinforcements are designed
to prevent the development of failure surfaces within the soil
mass. Accordingly, tensile forces develop within the
geosynthetic reinforcements that contribute to the stability of
geosynthetic-soil composite (e.g. Zornberg and Christopher
2007). Instead, geosynthetic reinforcements in pavement
applications are used to improve the performance of the paved
road under in-service conditions induced by traffic and
environmental loads (e.g. Zornberg et al. 2012, Roodi and
Zornberg 2012). While ultimate tensile failure is the condition
of concern in the design of geosynthetic-reinforced retaining
structures, the small displacement response governs the
performance of geosynthetic-reinforced systems in pavement
reinforcement applications.
Most of the methodologies and models developed for the
analysis and design of the geosynthetic-reinforced structures
have focused on the maximum strength or ultimate capacity of
the geosynthetic layers (Gupta 2009). However, capturing the
initial stiffness of soil-geosynthetic interface is central to
accurately address the small displacement behavior of
geosynthetic reinforced pavement systems. In the absence of
proper specifications to characterize the behavior of soil-
geosynthetic interfaces under small displacements, designers
have typically relied on the mechanical properties of
geosynthetics in isolation (e.g. ultimate tensile strength or
tensile stiffness/modulus) in an attempt to satisfy a certain level
of performance (Archer and Wayne 2012). Studies have aimed
at establishing correlations between geosynthetic index
properties and their field performance. These index properties
have included the rib strength, junction strength, aperture size,
wide-width tensile strength, tensile modulus, tensile strength at
2% and 5%, and flexural rigidity (e.g. Perkins et al. 2004,
Christopher et al. 2008, Cuelho and Perkins 2009, Mahmood et
al. 2012, Chen and Abu-Farsakh 2012). However, most of these
properties correspond to the behavior of the geosynthetics in-
isolation rather than to the soil-geosynthetic interaction.
The purpose of this study is to introduce a soil-geosynthetic
parameter capable of quantifying the performance of
geosynthetic reinforcement under small displacement
conditions. This parameter is defined as “Stiffness of Soil-
Geosynthetic Interaction” or
K
SGI
, which is expected to be
constant for a given soil-geosynthetic system under specific
confinement stress. This paper describes the assumptions and
formulations used to derive the
K
SGI
. The paper also reports on
