Probabilistic undrained resistance of subsea buried pipelines against upheaval bucking

Buried offshore pipelines that operate under high temperature and pressure may undergo upheaval buckling. Studies on the undrained uplift resistance of buried pipelines have received significant attention, but most existing solutions are limited to homogeneous clay or uniform clay of linearly increasing strength with depth. This paper demonstrates how the spatial variability of a clay influences the undrained uplift resistance and failure mechanism of buried pipelines. A random adaptive finite element limit analysis in conjunction with Monte-Carlo simulation is used to obtain the uplift resistance statistics and failure mechanisms of pipelines in spatially random clays, accounting for the effect of pipe embedment depth, clay weight (overburden), and pipe-clay interface. The worst-case correlation length at which the mean uplift resistance of pipelines reaches a minimum is investigated. Safety factors are provided for pipelines at different levels of target probability of failure. It is shown that ignoring the spatial variation in clay strength gives rise to the overestimation of the uplift resistance of pipelines. The spatial pattern of clay strength is associated to the clay failure planes around the pipeline and thus the pipe uplift resistance.