ABSTRACT Foundations of offshore structures are subjected to cyclic loads from wind and waves, which can cause the accumulation of deformations in saturated soil, alter stress distributions, and increase excess pore water pressures, leading to reduced bearing capacity. In order to investigate as well as describe the behavior of the foundation under cyclic loads, a new model test tank for experimental investigations was installed. A high-performance cylinder allows for the application of cyclic loads to the model foundation structure, whereas the test tank facilitates both drained and partially drained tests. In the small-scale testing facility, several sensors allow for the monitoring and recording of the soil structure interaction with a data acquisition system. Detailed insights into the test procedures, data interpretation, and the soil-structure interaction mechanisms allow for a comprehensive understanding of the system response. The primary objective of this study is to experimentally investigate the deformation modes of two gravity model foundations under drained cyclic loading with various eccentricities and to provide reliable data that can be used for back-calculation and validation of numerical models. The results show that under cyclic eccentric horizontal loading, the foundation experiences both average settlement and rotation, with both increasing as the number of load cycles rises. The predominant deformation mode depends on the type of loading. Another important insight is that the average settlement rate seems to be mainly dependent on the difference of maximum and minimum loads, whereas the rotation rate mainly depends on the average of maximum and minimum loads. Additionally, the influence of cyclic loads on postcyclic monotonic behavior was examined, and it was found that there is no degradation. Further numerical simulations using a sophisticated implicit constitutive model generally verified the correlations derived from the test results.
Goldau et al. (Fri,) studied this question.