The uplift capacity of horizontal plate anchors in spatially variable clay using sparse polynomial chaos expansions

Charlton, T; Rouainia, M

The uplift capacity of horizontal plate anchors in spatially variable clay using sparse polynomial chaos expansions

Lookup NU author(s): Dr Tom Charlton ORCiD, Professor Mohamed Rouainia

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Abstract

As the offshore energy industry moves towards deepwater installations, plate anchors are increasingly used to moor floating production facilities. The ultimate holding capacity of a plate anchor in undrained clay has been widely investigated in scenarios where the undrained shear strength is a deterministic parameter, uniform or linearly increasing across the soil mass. However, it has been shown that bearing capacity of footings can be overestimated if spatial variability is not taken into account. In this paper, a least angle regression-based sparse polynomial chaos expansion is used to efficiently study the uplift capacity of horizontal plate anchors in spatially variable clay represented by a high-dimensional random field. The coefficients of the expansion are obtained from a set of finite element analyses and a range of anchor embedment ratios are modelled to investigate both shallow and deep anchor behaviour. The limiting cases of an attached and vented anchor, where the anchor is either fixed to or separable from the soil, are also considered. It is found that the probability of failure of vented anchors reduces with embedment depth due to a decrease in the variability of anchor capacity as shear planes lengthen. In the attached case, the probability of failure is dependent upon whether the anchor fails by a shallow or deep mechanism.