Field Tests of Offshore Driven Piles Subjected to Lateral Monotonic and Cyclic Loads in Soft Clay

The large-diameter driven pile is one of the most common types of foundations used for offshore structures. Field tests of two offshore driven piles, each with a diameter of 2.2 m, subjected to lateral monotonic and cyclic loads in soft clay, were carried out at the Guishan Offshore Wind Farms in the Guangdong Province of China. Further analysis of the test results showed that the initial stiffness and ultimate soil reaction per unit length of the derived p-y curves of the driven piles were obviously larger than those of the American Petroleum Institute (API) p-y curves for the investigated soft clay soil. This finding could be a result of reconsolidation of soil around the pile after it was driven. The computed modified hyperbolic tangent p-y curves were in good agreement with the test results. For one-way cyclic loading tests, a cyclic degradation factor, t, was defined and calculated on the basis of the derived cyclic p-y curves, which were approximately linear to the cyclic soil reaction ratio and decreased as the soil depth increased. The factor t can be used to analyze the lateral cyclic responses of offshore driven piles, and the experimental results can provide valuable reference for analyses of lateral monotonic and cyclic pile–soil interactions in soft clay.