Abstarct: Flexible breasting dolphins comprise one or more large diameter vertical piles designed to absorb the kinetic energy of a berthing vessel by deformation characteristics of piles. The capacity of pile (or piles) to withstand berthing loads depends on the stiffness of the berthing system. The stiffness of the berthing system is a function of the stiffness of different components of the system; namely: pile(s), soil, and fender (if it exists). In fact, in this study the interaction of the soil and the pile, as one of the class of soil–structure interaction problems, is investigated. First, using experimental p-y curves for soil, the lateral behavior of the structure in the presence of the soil is modeled, and after verifiying the discussed model, a series of analyses were performed using linear and nonlinear behavior of the system (including the pile and the soil) for the lateral loads on the structure. In a study on one of the most famous flexible marine strucutures in the world, it was observed that the energy absorption capacity of the proposed model is in good agreement with required berthing energy of the design vessel. It should be noted that in the defined linear range of the material behavior, a certain depth of the soil below ground surface reaches its ultimate strength. Results from analysis of the berthing system in the range of nonlinear material behavior also indicated a significant relationship between the soil and the piles in the form of plastic hinges. These hinges behave as a distributed model, as a result of soil confinement around the pile, and variation of maximum bending moment location as the development of soil plasticity around the pile.