Pile foundations often behave under lateral forces. The complexity of soil-pile interaction is due to many geotechnical and geometrical factors as well as to the 3D nature of the phenomenon. This paper is aimed to present the results of a simplified 3D modelling of soil/pile system by linear solid finite elements. After validation of the model, a parametric study was carried out. The lateral subgrade reaction modulus was derived from a process of fitting and differentiation of shear forces curves along the pile, and a simplified formulation in homogeneous soil as well as in Gibson’s soil was proposed. At last, an assessment of this for-mulation was carried out by predicting the deflections of experimental piles tested at full scale.