Interfaces exist in every geotechnical system in many forms and at multiple scales. Examples include interfaces between two particles, interfaces between pile or tunnel shafts and the surrounding soil and interfaces between synthetic polymeric sheets and the underlying natural soils in engineered landfills. Irrespective of whether the interfaces are between two natural materials, a natural and man-made material, or two man-made materials, they each have their own unique set of characteristics and behavior that are governed by many factors including relative roughness, relative hardness, stress conditions, load rate effects, drainage conditions, degree of lubrication and temperature conditions. While historically, interfaces were often considered to be the “weak link” in a system, particularly as the result of a number of unexpected catastrophic failures, and thus accounted for in many subsequent design procedures as such, new insight gained over the past twenty years by researchers around the world has shown that it is possible to select combinations of materials and design an engineered interface so that it is “at least as strong” as the surrounding materials. These new insights have been gained as a result of experimental evidence, numerical modeling and analytical study of successful and failed systems.

While individual technical papers have been presented and/or published in various forums and proceedings over the years, no technical event has ever been convened for the sole purpose of allowing for the exchange of information and ideas pertaining to geotechnical interfaces. The research symposium held in September 2008 in Atlanta Georgia, USA on The Characterization and Behavior of Interfaces addressed this deficiency and the papers presented at that event are contained in these proceedings. Topics presented and discussed included:

• Characterization of interface materials

• Laboratory evaluation of interface behavior

• Field characterization of interface behavior

• Physical modeling of interface systems

• Numerical modeling of interface systems

• Analysis of systems failing at interfaces

• Field monitoring of systems containing interfaces

J. David Frost, Savannah, Georgia 2009