Kim André Larsen

Calibration of Failure Criteria for Bucket Foundations on Drained Sand under General Loading

A new concept with respect to offshore wind turbines, the bucket foundation, is known in the oil and gas industry, although the load conditions for wind turbines are significantly different. An extensive number of loading tests with small-scale bucket foundations subjected to combined loading were carried out in the geotechnical laboratory at Aalborg University in Aalborg, Denmark. Tests were performed on buckets of various sizes, embedment ratios, and load paths on saturated dense Aalborg University Sand No. 1. The experimental results were used to evaluate the behavior of the bucket foundations in accordance with the macromodel approach. An expression to describe the combined capacity of bucket foundations was developed by calibrating the failure criteria for bucket foundations.

Adaptive plasticity model for bucket foundations

AbstractBased on experimental investigations, the literature proposes different methods for modeling the behavior and capacity of foundations subjected to combined loading. Generally, two methods are used to predict the behavior of foundations: traditional approaches and hardening plasticity solutions. The first method is only capable of determining the capacity of the foundations and not the prepeak behavior. Thus, a new strain-hardening criterion is developed by calibrating failure criteria by employing data from small-scale tests on bucket foundations subjected to static loads. The shape of the yield, potential, and failure surfaces are found to be dependent on the embedment ratio (i.e., ratio of skirt length to the diameter) and load path. For the models tested, associated flow is observed to be plausible in the radial planes, whereas nonassociated flow is observed in the planes along the V-axis.

Effect of Embedment on the Plastic Behavior of Bucket Foundations

AbstractA series of comprehensive research and development projects has validated the novel concept of the bucket foundation as an alternative to piled foundations, and bucket foundations are rapidly becoming a viable option for offshore wind farms and marginal fields.Within the last decade, experimental studies have indicated the possibility of defining foundation response using plasticity theory. Results of multiple loading tests addressing the effect of embedment on the strain-hardening behavior of shallow bucket foundations under combined loading are reported. The kinematic mechanisms accompanying pre-failure are presented. It is argued that the drained capacity of offshore bucket foundations and the ratio of plastic increments are largely influenced by embedment depth and the preload ratio V/Vpeak.

Embedment Effects on Vertical Bearing Capacity of Offshore Bucket Foundations on Cohesionless Soil

AbstractThis paper presents the results from a series of physical modeling and three-dimensional finite-element (FE) analyses in which the authors examined the uniaxial vertical capacity of suction caissons for offshore wind turbines. The experiments were carried out in quartz sand and involved monotonic application of vertical load. It was found that the drained capacity of suction caissons is dependent on embedment ratio. In contrast, predictions from conventional semiempirical depth factors were found to somewhat underestimate when applied to rough foundations. On the basis of the tests and FE analyses, new expressions for the depth factor of shallow foundations were validated for embedment ratios (aspect ratios) up to unity, calibrating the fitting parameters by using data from a range of soil profiles.