Response of suction caissons in soft clay under vertical and horizontal loading for tidal energy converter applications

Suction caissons;Clay;Offshore Energy;Foundations

Wallace, Jeff Franklin

关键词: Suction caissons;    Clay;    Offshore Energy;    Foundations;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/101292/WALLACE-DISSERTATION-2018.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

In recent years, the push to reduce oil dependence has driven the research and use of renewable energy sources both on and offshore. Of the available offshore renewable energy resources, the tidal current serves as a promising and consistent source of energy due to its dependence on the rotation of the earth and the orbit of both the earth and the moon. Harnessing this energy requires the use of tidal energy converters (TECs), a technology that is still primarily in the development and prototyping phases. As such, design standards for TECs have not yet been developed. In order to develop such standards and deploy an economical, efficient, and reliable final product, all components of the TEC including the foundations must be thoroughly understood. TEC loading conditions will primarily be cyclic with the static loads resulting from the dead weight of the structure. The cyclic loads will have various components with periods up to approximately 24 hours and be strongly correlated to the tidal current’s flow characteristics. The TEC’s function and the tidal current’s flow characteristics provide a unique set of loading conditions when compared to traditional offshore energy structures for oil and gas. First, the vertical dead weight of the structure will be relatively low. Second, the TEC will be designed to interact with the horizontal flow of water. Third, the primarily environmental load will reverse direction approximately every 12 to 24 hours with the ebb and flood of the tide. Suction caissons provide a foundation element that are theoretically well equipped to resist these unique set of loading conditions while further contributing to the ‘green’ nature of the TEC. This study investigated the response of intermediate aspect ratio suction caissons in clay under loads applicable to TEC loading through the use of loads tests on three types of scaled physical models. The 1-g model scale load tests in kaolin and 90-g centrifuge scale load tests in kaolin allowed for the investigation of a wide range of loading conditions both monotonic and cyclic in the vertical and horizontal direction. These vertically and horizontally directed loads functioned as simplified loading conditions on suction caissons configured as multipods and monopods. The 1-g model scale load tests in laponite allowed for visualization of the failure mechanism of clay during vertical loading of suction caissons. These visualizations allowed for a comparison of the mobilized failure mechanism to the failure mechanism assumed in the design of suction caissons.