In geotechnical engineering, the main parameter for the performance of structures such as reinforced walls or deep foundations is often the shaft bearing capacity. In numerical analysis, important advancements have been made on studying the behavior of the soil and the retaining structures separately. The performance of many geotechnical foundation systems depends on the shear behavior at the soil structure interface. For deep foundations, the main component that affects friction is the horizontal earth pressure. When a pile is getting axially loaded, the soil grain network at the interface, starts to move and rearrange. In conditions of axial cyclic loading a contractive behavior of soil can generally be observed as in [1] and [2]. This can be explained by the progressive densification and relaxation of the soil under cyclic shear at the soil pile interface, as well as the local refinement of the grain distribution by grain breakage and rearrangements. As the soil contracts and decreases in volume, the normal stress around the pile surface decreases and the soil pile friction degrades. This can lead to failure of the whole geotechnical foundation system. The purpose of the work presented in this paper is to analyze locally (at the element level) the contact behavior of a soil-pile contact problem. Therefore, a 2D shear test is modeled using the Finite Element Method. The formulation of a 4 nodded zero-thickness interface element of Beer [3] is chosen with a linear interpolation function. Four constitutive contact models adapted for contact problems have been implemented. The simple Mohr-Coulomb [4] and Clough and Duncan [5] models were chosen initially, due to the ease of implementation and few number of parameters needed. After, more complicated models in the framework of elasto-plasticity such as: Lashkari [6] and Mortara [7] were implemented for the first time into the finite element code of the shear test problem. They include other phenomena such as: relative density of soil, the stress level and sand dilatancy. From the results the relation between shear displacement and shear stress has been deduced. Finally, a discussion of the advantages and the drawbacks during computation of each model is given at the end
