Behavior of Soil -structure interfaces under cyclic loading for large numbers of cycles: Application to piles Comportement des interfaces sol -structure sous chargement cyclique ‡ grand nombre de cycles : Application aux pieux

Pile foundations are usually subjected to cyclic loading which can be either environmental or in dustrial. Loading and unloading sequences of the pile cause very significant variation in the behavior of the pile -soil system and generate degradation of the bearing capacity and an accumulation of irreversible displacement. The paper presents a study ofthe behavior of piles subjected to axial cyclic loading for large numbers of cycles using a physical modeling approach in a calibration chamber. To focus on the degradation of the friction in soil -pile interface, the experiments are carried out in two -way displacementcontrolled tests. Firstly, The experimental set -up was presented, then the typical results of the evolution of skin friction under cyclic loading. The results indicate that the application of a large number of cycles to the pile, the skin fric tion decrease initially then increase continually up to the end of the cyclic sequence. It can be concluded that the phase of friction reinforcement is due to a partially constrained dilatancy phenomenon of the sand within the interface zone .