Geosynthetics have been used in reinforcement applications for decades now. In the early days, nonwovens were principally used to stabilise base courses in road construction. The second major area of application was the construction of steep slopes and walls, the dimensions of which have been greatly extended by the development of high-strength, highmodulus geogrids. These new products opened up new fields of application such as geosynthetic- encased soil columns or the bridging of soft soil layers on pile-like elements. The various possible applications of geosynthetic reinforcement are briefly outlined in this paper. All these application areas are surprising in that their actual bearing capacity is much higher than that calculated, and their deformation lower (Bräu and Floss, 2000); this shows that the composite behaviour of geosynthetics and soil is not yet sufficiently understood. Depending on the application, one of the following action mechanisms or a combination of them, is decisive. These are the membrane effect, the pullout behaviour and the constraining effect, which goes hand in hand with a confining effect, as well as the interlocking mechanism, which can however be subsumed under the constraining mechanism. The constraining effect and the pullout behaviour will be considered in greater detail in this paper and the research conducted at the Geotechnical Engineering Institute of the RWTH Aachen University presented.
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