The assumption for the subgrade reaction modulus of bridge abutment has an influence on the design of integral bridges. The modulus is mainly influenced by the type of filling material, the filling and compaction process, partly or unsaturated soil conditions and by the cyclic stress-strain path. The soil reactions are further dependent on the deflections and stiffness of the bridge structure. The uncertainty of most of the parameters has led to huge differences between upper and lower limits of earth pressures which have to be applied in the design of integral bridges. The aims of the investigation, are to get an improved understanding of the underlying non linear mechanical relations and to develop recommendations for design of integral bridges. The soil-structure interaction is investigated with model tests under 1g conditions. Complex finite element simulations using Abaqus software show the cyclic behavior under partly saturated conditions. The results of the physical and numerical models are compared and discussed. It is shown, that the subgrade reaction modulus is not a constant value and therefore a more sophisticated rheological non-linear spring embedment function is needed.