Laboratory Setup for Vertically Loaded Suction Caisson Foundation in Sand and Validation of Responses

Wind energy obtained by means of wind turbine has been proved to be a concrete resource of green energy. Development of such structures requires research on offshore construction, since this is the direction for future improvement on this field. Wind turbines are relatively light and slender devices usually installed in farms, therefore many inexpensive foundations are needed. Suction Bucket foundations are a suitable option for this purpose, but for large scale utilization more research is required, especially for in-service performance. Size of offshore wind turbine has been increasing during the last years and, following this trend, design choice will turn into foundation composed of three or four suction bucket foundations, called respectively tripod and tetrapod. Overturning moment in tripod and tetrapod is carried by vertical loading; therefore vertical pull-out capacity is tested, in both static and cyclic case of loading. Testing rig and equipment are presented together with procedures. Tests results are presented in order to verify the output of tests. CPT-based methods and beta-methods to evaluate installation and pull-out resistance are then presented and implemented in Matlab in order to validate responses. It is demonstrated that kf parameter of CPT-based methods is dependent on the overburden pressure applied. Parameters of beta methods are analyzed and defined. Satisfying results are obtained with methods that are considering a linear increase or decrease with the depth of vertical stress, depending if the case of application is installation or pull-out.