Soil Impact on Non-Stationary Anchor Performance

This paper discusses predictive models of penetration depth and load capacity of non-stationary anchor, an issue which affects the overall design and reliability of mooring systems in deep water. Anchors under consideration in this paper include drag embedment anchors (DEA’s), vertically loaded anchors (VLA’s), and spring-shank anchors. This paper presents examples of the performance of predictive models for anchor trajectory and capacity for given sets of soil conditions. The implications of uncertainties in anchor trajectory and capacity on the overall reliability and design of mooring systems is then assessed. DEA’s and VLA’s are an attractive option for moorings in deep water, particularly mobile offshore drilling units. A chief concern in the usage of such anchors is the uncertainty in their load capacity, uncertainty which is largely associated the difficulty in predicting their depth of penetration. More reliable design tools for predicting the trajectory and capacity of these types of anchors can lead to more economical and reliable mooring system designs for these units. Improved reliability of design tools for predicting the capacity of non-stationary anchors can also aid in gaining acceptance of this type of anchor for permanent mooring systems. Reliable predictions of anchor performance are critical to designing economical and reliable mooring systems. This topic is relevant to the design of mooring systems for hydrocarbon exploration platforms currently in use. Looking forward, reliable mooring systems are also likely to be relevant to the design of various renewable energy source production systems such as wind and current power.