Offshore wind developments are moving towards deep-water regions where energy is abundant, visual impact is minimised and the larger turbine sizes can make the energy production more cost-effective. One of the key challenges facing the industry is the development of reliable substructures. While fixed foundation systems are widely used for shallow-water (<60 m) developments, permanent anchors are seen as one of the most viable mooring solutions for floating structures in deep water. In the current study, the pull-out behaviour of square plate anchors in clay was investigated using large-displacement finite-element analysis. The anchor capacity and failure mechanism were considered for a range of embedment ratios and undrained shear strengths. Three distinct modes of anchor failure identified in previous studies were examined through the analysis of four descriptors including: the pull-out capacity of the anchor, the pull-out displacement required to mobilise this capacity, the energy absorbed by the anchor during pull-out and the variation of the pull-out capacity with respect to a normalised overburden pressure. The findings of the study are presented in the form of a series of charts that can aid design through understanding of the factors controlling the development of anchor failure modes, in addition to identifying the transition point between different failure mechanisms.@en

This paper presents an experimental and analytical study to investigate the effect of shape on the pull-out capacity of shallow horizontal plate anchors in sand under drained loading conditions. Novel dynamically penetrating plate anchor concepts have been proposed for use in the offshore energy sector. These anchor concepts may have shapes that are atypical, and the analysis of pull-out capacity of these shapes may be needed for design. Most of the research on the capacity of shallow horizontal anchors has focused on square, rectangular or circular shapes. Physical and analytical modelling was used to study the capacity of circular, square, triangular and kite-shaped plate anchors. The 1g physical model results indicated that the circular anchor had the highest capacity, which was up to two times higher than the square anchor, which had the lowest capacity of all shapes included in this study. The equilateral triangle and kite shapes had capacities that fell between the circle and the square shapes. A new generalised non-associated flow limit equilibrium model was developed to predict the pull-out capacity of shallow plate anchors with convex polygon anchor shapes. The model was most accurate at embedment ratios of 4 or less, with a bias of less than 10%.@en

In recent times, interest in dynamically installed foundation systems for deep-sea construction has increased; however, these foundation systems are still under development and need quantification of various soil parameters with different perspectives. For the design of dynamically installed foundations, it is essential to assess the strain-rate effect on very soft soils. The T-bar has been widely used to characterize soft offshore sediments, such as silt and clay, and there is extensive existing literature on the interpretation of test results. Strain-rate dependence has not previously been fully examined for T-bar tests in very soft clay at very high rates of penetration. This paper examines this aspect using a physical model test. A 65-cm-thick kaolin clay bed was formed using vacuum consolidation. A T-bar was driven into the clay bed at rates that varied from 0.1 cm/s to 60 cm/s. The tests revealed that the resistance factor increased by 9 % for every 10-fold increase in the penetration rate for the material tested in this research.@en