In a press release date July 11, 2017, HUESKER expanded on the need for a newly defined aspect of geogrids—interaction flexibility—and released a video on the characteristic. The company noted that according to the current state of scientific knowledge, the key properties of effective reinforcement are adequate tensile stiffness and tensile strength coupled with good interaction behavior. The concept of “interaction flexibility” introduces a new, previously disregarded aspect: the flexibility of the incorporated geogrid, which has been shown to improve the interaction between soil and reinforcement.
The safety and longevity of reinforced earthworks are largely dictated by three factors: 1) The incorporated geogrid must exhibit adequate tensile strength. Insufficient strength may lead to failure of the reinforcement and, consequently, of the entire structure; 2) The incorporated geogrid must exhibit adequate tensile stiffness— as one of the factors determining maximum structural deformation; 3) Good interaction behavior between soil and reinforcement plays a vital role in force transmission between geogrid and soil, and is therefore key to structural safety and performance.
“Interaction behavior” is a general term denoting the capacity of a geogrid—among other things, through interlock and friction— to take up and transfer forces from the soil. Yet, all previous conceptual frameworks have failed to give due attention to one particular aspect: the impact of the flexural stiffness of the geotextile product on interaction. By adding this key criterion, the term “interaction flexibility” expands the definition of interaction behavior.
Interaction flexibility is the combined ability of a reinforcement product to achieve a strong bond with the soil through optimization of the (micro-, meso-, and macro-) interlock properties and to adapt flexibly to soil particles in order to prevent void formation.
Christian Lackner, in his 2012 PhD thesis at the Graz (Austria) University of Technology, described the importance of this adaptability: “The interaction between soil and reinforcement is even stronger where the geogrid can adapt to the soil particles and thus prevent the formation of voids within the soil structure. In other words, the installation of very rigid geogrids can produce negative interaction effects.”
The flexibility of a geogrid is easy to characterize using an existing test method, defined in ASTM D7748. Accordingly, flexural stiffness, measured in the unit “mg-cm,” should be as low as possible.
The term “interaction flexibility” is further defined in a new five-minute video.