A Similitude Theory for Bucket Foundations Under Monotonic Horizontal Load in Dense Sand

This paper aims at finding force-displacement relationships to be employed in the design of bucket foundations for offshore wind turbine. This is accomplished by combining small-scale tests and element tests within a theoretical framework. A similitude theory, regarding the lateral displacement of bucket foundations under horizontal load, is put forward. A constitutive law of the soil and a load-displacement relationship for the bucket foundation are theoretically obtained. Triaxial tests of sand, and small- scale tests of bucket foundation, are respectively employed to corroborate the theory. Attention is given to the different behaviour shown during the compressive and dilative phases of the soil. Some analogy between triaxial tests and tests of bucket foundation are pointed out. A theoretically derived power law is found capable to represent the dimensionless horizontal load-displacement curves of experimental results. In accordance with the theory, the exponent of the power law slightly varies between tests with considerably different features. The non-dimensional moment-rotation relationship is represented by a power law as well. The approach is considered valid for fatigue design. The study may be an interesting source for further researches on long-term cyclic horizontal loading.