Earthworks can be reinforced for various purposes and in various ways. Apart from reinforcing substratum layers, soil reinforcement is mainly used in stabilising steep embankments with classic reinforced earth, soil nailing and above all reinforcing with geosynthetic materials. We know very well that steep embankment structures are much more stable than determined by calculations and always display lower deformations than expected. This is due to the special bonding behaviour of the soil and reinforcing element, which is very different to that of reinforced concrete, for example, on account of the different rigidity relation-ships. But up to now there have been no generally accepted calculation methods to show the special bonding behaviour of the soil and reinforcing element in more detail. The paper contributes to a better understanding of the load-bearing characteristics of reinforced bodies of soil. It shows that tensile forces introduced into the reinforcing elements by the soil lead to deformation constraints in the body of soil, which transform the very differing stress state under load into a more isotropic stress state. This is accompanied by a significant increase in strength and simultaneously a lower deformation. In large scale biaxial tests with geogrids inserted into the soil, this effect, which up to no now has only been known in terms of quality, can now be impressively visualised too using the Digital Image Correlation (DIC) method.