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SUMMARYA simplified method of analysis for estimating lateral load capacity of suction caisson anchors based on an upper bound plasticity formulation is presented. The simplification restricts the analysis to caissons in uniform and linearly varying undrained strength profiles; nevertheless, its computational efficiency permits quick evaluation of a number of parameters affecting load capacity. The validity and limitations of the simplified formulation are demonstrated through comparisons to more rigorous finite element solutions. A series of sensitivity studies demonstrate the effects of various soil conditions and loading parameters.

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Well fatigue assessment is an important aspect of the design and integrity assurance of deepwater riser-well systems. Fatigue damage arises from stress changes in a conductor due to cyclic loading. In practice, the lateral cyclic soil response is typically modeled using Winkler type springs known as the soil resistance-displacement (p-y) springs. An appropriate soil model for conductor-soil interaction analysis should predict the absolute and incremental magnitudes of stresses and the resulting impact on fatigue. Monotonic p-y relationships (backbone curves) which were originally developed for piled foundations are not appropriate for well conductor fatigue analysis. To determine the appropriate soil response an extensive study involving physical model testing in a geotechnical centrifuge and numerical analyses was initiated. The intent was to develop a robust and comprehensive approach to cover a wide range of seabed soils and loading conditions specifically for conductor fatigue analysis. Soil p-y models were developed for conductors installed in normally consolidated to lightly overconsolidated clays, medium-dense sands and over-consolidated clays. The models rely on the cyclic response of degraded soil at the steady-state condition and provide fatigue life predictions with high accuracy. This paper provides an overview of the past and recent studies that led to development of the fatigue p-y models. It presents the results of two centrifuge test series conducted in normally consolidated clay and medium dense sand. Ultimately, the paper provides recommendations for developing p-y springs specifically for well conductor fatigue analysis.