Evaluation of Small-Scale Laterally Loaded Monopiles in Sand

In current designs of offshore wind turbines, monopiles are often used as foundation. The behaviour of the monopoles when subjected to lateral loading has not been fully investigated. In this paper the diameter effect on laterally loaded non-slender piles in sand is evaluated by means of results from six small-scale laboratory tests, numerical modelling of the same test setup and existing theory. From the numerical models, p−y curves are derived and compared to current design regulations. The recommendations in API (1993) and DNV (1992) are observed to be in poor agreement with the numerically obtained p−y curves. The initial stiffness, Epy*, of the p−y curves is found to increase with increasing pile diameter. Considerable uncertainties are observed to be related to small-scale testing, and the evaluations clearly indicate that the accuracy of small-scale testing is increased when increasing the pile diameter and applying overburden pressure.