COVER STORY Positioning at installation site 2017 OPA WINNER Tri-Pod Suction Buckets for Offshore Wind Turbine Foundation Geotechnical engineers have been installing innovative, permanent underwater foundation systems utilizing suction buckets for the offshore industry since the early 1980s (Senpere and Auvergne, 1982). This foundation system has been successfully used on numerous and various types of offshore structures in a wide range of environments. Suction buckets have numerous advantages compared to conventional underwater foundation systems. The more notable advantages include easy installation, large loading capacity, low noise and retrievability. The application of reduced water pressure inside the bucket facilitates the installation of the suction buckets, where a suction pump attached at the top of the bucket can accomplish the entire driving operation. Because of this efficient operation, very large suction buckets can be driven into the seafloor, which eliminates the use of a large number of small piles. In Korea, one of the most economical and reliable renewable energy sources is wind power; however, onshore wind power generation has encountered many problems, such as the lack of favorable sites and public concerns about noise and environmental damage. Consequently, offshore wind power generation has attracted increasing attention due to its abundant potential, high efficiency of grid connection, and availability of easy expansion. In November 2011, the government of Korea announced a national offshore wind power development roadmap, which targeted its offshore wind power generation with the goal of becoming one of the top three nations in the world for offshore wind power generation. Korea Electric Power Corporation Research Institute (KEPRI) is the main research arm of the Korea Electric Power Corporation (KEPCO) and conducts research and development on electricity, power generation, renewable energy and other energy-related matters. KEPRI ultimately provides forefront knowledge and leadership to KEPCO with respect to energy and related areas for its near- and long-term needs. Financial support for the overall project, of which the suction bucket foundation system installed for the pilot phase wind turbine is described below, was provided from the New and Renewable Energy Program of the Korea Institute of Energy Technology Evaluation and Planning funded by the Korean Government Ministry of Trade, Industry and Energy. This project is expected to include three stages: a pilot phase, a demonstration phase and a dissemination phase. Currently, the pilot phase is underway. As part of the pilot phase, KEPRI and Advanced Construction Technology, Inc. (ADVACT) initiated the installation of an offshore wind turbine in December 2014 and was completed in October 2016. This 3 MW-capacity wind turbine, with a hub height of about 80 m (262 ft) above the mean sea level, was installed about 200 m (656 ft) offshore in a location where the water was approximately 10 m (33 ft) deep. The length of each blade on the wind turbine is about 48 m (157 ft). AUTHORS Moo Sung Ryu, KEPRI, Daejin Kwag, ADVACT , Dr. Jun-Shin Lee, KEPRI, Tae Hwan Lee, ADVACT, Dr. Sangchul Bang, P.E., South Dakota School of Mines and Technology, and Gerard T. Houlahan, P.E., Moffatt & Nichol 14 • DEEP FOUNDATIONS • NOV/DEC 2017
