The need of clean energy have encouraged the use of offshore wind turbines. However, high costs and time consuming of current monopile foundations have incentivated the search for new types of foundations. This book presents an experimental work performed with skirted foundations. When suction is applied for its installation they are called suction caissons. The behaviour of suction caissons is studied in sand as well as in clay, during installation and under subsequent moment-lateral loadings. Results of cyclic vertical loading tests in clay and cyclic combined loading tests in sand are also presented. The theoretical forms of the yield surface and flow rule were calibrated from the results of moment loading tests under low vertical loads, which is the case of a wind turbine. Moment capacity under tension was considered in the capacity formulation. Results from cyclic moment loading tests showed that Masing's rules were obeyed. This work is relevant for engineers and designers involved in offshore wind turbine projects.