Effect of cyclic loading at a large number of cycles on the bearing capacity of piles in sand

The paper presents the evolution of the bearing capacity of a pile model in calibration chamber after the application of a cyclic axial loading at a large number of cycles. This work is a part of the French research project ANR-SOLCYP which aims to understand the mechanisms governing the evolution of the bearing capacity of piles up to a very large number of cycles (105 cycles). The experimental study consists in using a calibration chamber in which axial cyclic loading is applied to pile model jacked into sand under a large number of cycles, up to 105, while measuring the axial shaft capacity before and after the cyclic sequence. Some key parameters have been investigated such as the cyclic displacement amplitude, the level of applied consolidation stress and the density index of the soil. It was found that after a large number of cycles of cyclic axial loading, the post-cyclic bearing capacity of the piles is significantly improved. Results analysis indicated that the mechanism of densification of the soil around the pile led to improve pile capacity.