By HUESKER – Key properties in effective geosynthetic reinforcement are adequate tensile stiffness and tensile strength coupled with good interaction behavior. The relatively new technical term interaction flexibility introduces a previously disregarded aspect: the flexibility of the geogrid in a reinforced structure. This property has been shown to improve the interaction between soils and the geosynthetic reinforcement.
Image of geogrid interaction flexibility in soil - HUESKER


The term interaction behavior is a general term that denotes the capacity of a geogrid (e.g., through interlock and friction) to take up and transfer forces from the soil. Previous conceptual frameworks have failed to give due attention to one particular aspect: the impact of the flexural stiffness of the geosynthetic product on interaction. By adding this key criterion, we get interaction flexibility, a term which expands the previous definition of interaction behavior.
By interaction flexibility, we mean the combined ability of a geosynthetic reinforcement product, firstly, to achieve a strong bond with the soil through optimization of the (micro-, meso- and macro-) interlock properties and, secondly, to adapt flexibly to soil particles in order to prevent void formation.
Geogrid - soil interaction, levee construction - HUESKER
The importance of this adaptability is described by C. Lackner in his PhD thesis (2012, Graz University of Technology):

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 by means of 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 explained in a new five-minute video:

See other videos on the HUESKER Group’s YouTube channel.


The safety and longevity of reinforced earthworks are largely dictated by three factors. Firstly, the incorporated geogrid must exhibit adequate tensile strength. Insufficient strength may lead to failure of the reinforcement and, consequently, of the entire structure. Secondly, the incorporated geogrid must exhibit adequate tensile stiffness—as one of the factors determining maximum structural deformation. Thirdly, good interaction behavior between soil and reinforcement plays a vital role in force transmission between the geogrid and soil, and is therefore key to structural safety and performance.
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